U.S. patent application number 10/328273 was filed with the patent office on 2003-10-30 for plastic lens systems, methods and apparatus.
This patent application is currently assigned to Q2100, Inc.. Invention is credited to Buazza, Omar M., Joel, Larry H., Lattis, Matthew C., Luetke, Stephen C., Powers, Galen R..
Application Number | 20030203065 10/328273 |
Document ID | / |
Family ID | 27496420 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030203065 |
Kind Code |
A1 |
Buazza, Omar M. ; et
al. |
October 30, 2003 |
Plastic lens systems, methods and apparatus
Abstract
An apparatus for preparing a plastic eyeglass lens includes a
coating unit and a lens curing unit. The apparatus is preferably
configured to allow the operation of both the coating unit and the
lens curing unit. The apparatus may also include a post-cure unit
and a controller. The controller is configured to control the
operation of the coating unit, the lens curing unit and the
post-cure unit. The lens forming unit may include an LCD filter
disposed between activating light sources and a mold assembly. The
mold assembly preferably includes two mold members held together by
a gasket. The gasket preferably includes four protrusions spaced at
90 degree intervals about the gasket. A lens forming composition
may include a first photochromic compound, a second photochromic
compound and a light effector. The light effector may alter the
color of a lens when exposed to photochromic activating light, when
compared to a lens formed from a lens forming composition which
does not include a light effector.
Inventors: |
Buazza, Omar M.;
(Louisville, KY) ; Luetke, Stephen C.;
(Louisville, KY) ; Lattis, Matthew C.;
(Louisville, KY) ; Joel, Larry H.; (Louisville,
KY) ; Powers, Galen R.; (Louisville, KY) |
Correspondence
Address: |
ERIC B. MEYERTONS
CONLEY, ROSE & TAYON, P.C.
P.O. BOX 398
AUSTIN
TX
78767-0398
US
|
Assignee: |
Q2100, Inc.
|
Family ID: |
27496420 |
Appl. No.: |
10/328273 |
Filed: |
December 23, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10328273 |
Dec 23, 2002 |
|
|
|
10188621 |
Jul 3, 2002 |
|
|
|
10188621 |
Jul 3, 2002 |
|
|
|
09161250 |
Sep 25, 1998 |
|
|
|
6416307 |
|
|
|
|
Current U.S.
Class: |
425/174.4 ;
425/808 |
Current CPC
Class: |
G02B 1/041 20130101;
Y10S 425/808 20130101; Y10S 425/812 20130101; B29D 11/00442
20130101 |
Class at
Publication: |
425/174.4 ;
425/808 |
International
Class: |
B29D 011/00 |
Claims
What is claimed is:
1. An apparatus for preparing an eyeglass lens, comprising: a first
mold member having a casting face and a non-casting face; a second
mold member having a casting face and a non-casting face, the
second mold member being spaced apart from the first mold member
during use such that the casting faces of the first mold member and
the second mold member at least partially define a mold cavity; a
coating unit for applying a coating to at least one of the mold
members or the eyeglass lens during use; and a lens curing unit
configured to direct activating light toward the mold members
during use; wherein the lens curing unit and the coating unit are
substantially contained within a single enclosure.
2. The apparatus of claim 1, wherein the apparatus is configured to
form non-photochromic lenses and photochromic lenses.
3. The apparatus of claim 1, wherein the apparatus is configured to
substantially simultaneously apply a coating to the first and
second mold members disposed within the coating unit and direct
activating light toward another pair of mold members disposed
within the lens curing unit.
4. The apparatus of claim 1, wherein the coating unit is a spin
coating unit.
5. The apparatus of claim 4, wherein the spin coating unit
comprises: a holder for holding the eyeglass lens or at least one
of the mold members, wherein the holder is configured to revolve
during use; and an activating light source configured to direct
activating light towards the coating unit during use.
6. The apparatus of claim 5, wherein the holder is configured to
revolve such that coating material is radially dispersed during
use.
7. The apparatus of claim 5, wherein the activating light source is
an ultraviolet light source.
8. The apparatus of claim 5, wherein the activating light source
has a peak light intensity at a range of about 200 nm to about 300
nm.
9. The apparatus of claim 5, wherein the activating light source
comprises a substantially linear light element.
10. The apparatus of claim 5, wherein the holder is configured to
rotate up to about 1500 revolutions per minute.
11. The apparatus of claim 1, further comprising a cover for
covering the coating unit, wherein an activating light source for
use with the coating unit is positioned on an inner surface of the
cover.
12. The apparatus of claim 1, wherein the lens curing unit
comprises a first light source configured to generate and direct
activating light toward at least one of the mold members during
use.
13. The apparatus of claim 12, wherein the first light source is
configured to direct activating light toward the first mold member,
and wherein the lens curing unit further comprises a second light
source configured to generate and direct activating light toward
the second mold member.
14. The apparatus of claim 13 wherein the first and second light
sources are configured to generate and direct a pulses of
activating light toward the mold members.
15. The apparatus of claim 12, further comprising a filter disposed
directly adjacent to at least one of the mold members, the filter
being configured to manipulate an intensity of the activating light
directed toward the mold members during use.
16. The apparatus of claim 15, wherein the filter is a hazy filter
comprising a varying thickness such that the filter varies an
intensity distribution of activating light directed across the mold
members during use.
17. The apparatus of claim 15, wherein the filter is a liquid
crystal display filter.
18. The apparatus of claim 12, further comprising an air
distributor configured to apply air to the mold members during
use.
19. The apparatus of claim 12, wherein the first light source
comprises a fluorescent light source configured to emit light at a
wavelength of about 385 nanometers to 490 nanometers.
20. The apparatus of claim 12, wherein the lens curing unit
comprises a lens drawer for positioning the mold members proximate
to the first light source, the lens drawer being configurable to be
inserted within and removed from the irradiation chamber.
21. The apparatus of claim 1, further comprising a post-cure unit,
the post-cure unit configured to simultaneously apply heat and
activating light to the interior of the post-cure unit.
22. The apparatus of claim 21, wherein the post-cure unit comprises
a fluorescent light.
23. The apparatus of claim 21, wherein the post-cure comprises a
heater, the heater configured to heat the interior of the post-cure
unit to a temperature of up to about 125.degree. C.
24. The apparatus of claim 21, wherein the post-cure unit comprises
a conductive heating apparatus, the conductive heating apparatus
being adapted to conductively apply heat to a face of at least one
of the mold members during use.
25. The apparatus of claim 1, further comprising a programmable
controller configured to substantially simultaneously control
operation of the coating unit and the lens curing unit during
use.
26. The apparatus of claim 1, further comprising a programmable
controller configured to adjust a dose of the activating light
reaching the mold member as a function of the temperature of the
mold members.
27. The apparatus of claim 1, further comprising a programmable
controller configured to vary an intensity of the light as a
function of the temperature of the molds.
28. The apparatus of claim 1, further comprising a programmable
controller configured to control operation of the lens curing unit
using a Proportional-Integral-Derivative control scheme.
29. The apparatus of claim 1, further comprising a programmable
controller and a light sensor configured to measure the dose of
light transmitted to the mold cavity, and wherein the light sensor
is configured to communicate with the programmable controller, and
wherein the programmable controller varies the intensity or
duration of light such that a predetermined dose is transmitted to
the mold cavity.
30. The apparatus of claim 1, wherein the lens curing unit
comprises a first light source and a second light source, and
further comprising a programmable controller configured to
individually control the first and second lights.
31. The apparatus of claim 1, further comprising a cooling fan for
cooling the mold members during use and a thermocouple for
measuring a temperature of the mold members during use, and further
comprising a programmable controller configured to operate the
cooling fan in response to the temperature of the mold members as
measured by the thermocouple.
32. The apparatus of claim 1, wherein the coating unit is a
spin-coating unit, and further comprising a programmable controller
configured to control a rate of rotation of a holder of the spin
coating unit.
33. The apparatus of claim 1, further comprising a post-cure unit,
the post-cure unit configured to simultaneously apply heat and
activating light to the interior of the post-cure unit, and further
comprising a programmable controller configured to substantially
simultaneously operate the coating unit, the lens curing unit, and
the post-cure unit.
34. The apparatus of claim 1, further comprising a programmable
controller configured to control operation of the lens curing unit
as a function of the eyeglass lens prescription.
35. The apparatus of claim 1, further comprising a liquid crystal
display positioned between an activating light source and one of
the mold members, and further comprising a programmable controller
configured to change the filter in response to the prescription of
the eyeglass lens.
36. An apparatus for preparing an eyeglass lens, comprising: a
first mold member having a casting face and a non-casting face; a
second mold member having a casting face and a non-casting face,
the second mold member being spaced apart from the first mold
member during use such that the casting faces of the first mold
member and the second mold member at least partially define a mold
cavity; a lens curing unit configured to direct activating light
toward the mold members during use; and a post-cure unit configured
to apply heat and activating light to the eyeglass lens.
37. An apparatus for curing an eyeglass lens, comprising: a first
mold member having a casting face and a non-casting face; a second
mold member having a casting face and a non-casting face, the
second mold member being spaced apart from the first mold member
during use such that the casting faces of the first mold member and
the second mold member at least partially define a mold cavity; a
coating unit configured for applying a coating to at least one of
the mold members or the eyeglass lens during use; a lens curing
unit configured to direct activating light toward the mold members
during use; a post-cure unit configured to apply heat and
activating light to the eyeglass lens; and a programmable
controller configured to substantially simultaneously control
operation of the coating unit, the lens curing unit, and the
post-cure unit during use.
38. A system for preparing an eyeglass lens, comprising: a first
mold member having a casting face and a non-casting face; a second
mold member having a casting face and a non-casting face, the
second mold member being adapted to be spaced apart from the first
mold member during use such that the casting faces of the first
mold member and the second mold member at least partially define a
mold cavity; a lens forming composition adapted to be disposed
within the mold cavity during use, comprising: a monomer that cures
by exposure to activating light to form the eyeglass lens during
use; a photoinitiator that initiates curing of the monomer in
response to being exposed to activating light during use; a coating
unit for applying a coating to at least one of the mold members or
the eyeglass lens during use; and a lens curing unit configured to
cure at least a portion of a lens forming composition into the
eyeglass lens by directing activating light toward mold members
during use.
39. The system of claim 38, wherein the lens forming composition
further comprises photochromic compounds.
40. The system of claim 38, wherein the lens forming composition
further comprises ultraviolet/visible light absorbing
compounds.
41. The system of claim 38, wherein the apparatus is configured to
substantially simultaneously apply a coating to a first set of mold
members and direct activating light toward a second set of mold
members.
42. The system of claim 38, wherein the coating unit is a spin
coating unit.
43. The system of claim 42, wherein the spin coating unit
comprises: a holder for holding the eyeglass lens or at least one
of the mold members, wherein the holder is configured to revolve
during use; and an activating light source configured to direct
activating light towards the coating material during use.
44. The system of claim 43, wherein the holder is configured to
revolve such that coating material is radially dispersed during
use.
45. The system of claim 43, wherein the activating light source is
an ultraviolet light source.
46. The system of claim 43, wherein the activating light source has
a peak light intensity at a range of about 200 nm to about 300
nm.
47. The system of claim 43, wherein the activating light source
comprises a substantially linear light element.
48. The system of claim 43, wherein the holder is configured to
rotate up to about 1500 revolutions per minute.
49. The system of claim 38, further comprising a cover for covering
the coating unit, wherein an activating light source for use with
the coating unit is positioned on an inner surface of the
cover.
50. The system of claim 38, wherein the lens curing unit comprises
a first light source configured to generate and direct activating
light toward at least one of the mold members during use.
51. The system of claim 50, wherein the first light source is
configured to direct activating light toward the first mold member,
and wherein the lens curing unit further comprises a second light
source configured to generate and direct activating light toward
the second mold member.
52. The system of claim 50, further comprising a filter disposed
directly adjacent to at least one of the mold members, the filter
being configured to manipulate an intensity of the activating light
directed toward the mold members during use.
53. The system of claim 52, wherein the filter is a hazy filter
comprising a varying thickness such that the filter varies an
intensity distribution of activating light directed across the mold
members during use.
54. The system of claim 52, wherein the filter is a liquid crystal
display filter.
55. The system of claim 38, further comprising an air distributor
configured to apply air to the mold cavity to remove heat from the
mold cavity during use.
56. The system of claim 50, wherein the first light source
comprises a fluorescent light source configured to emit light at a
wavelength of about 385 nanometers to 490 nanometers.
57. The system of claim 38, further comprising a post-cure unit,
the post-cure unit configured to simultaneously apply heat and
activating light to the interior of the post-cure unit.
58. The system of claim 57, wherein the post-cure unit comprises a
fluorescent light.
59. The system of claim 57, wherein the post-cure unit comprises a
heater, the heater configured to heat the interior of the post-cure
unit to a temperature of up to about 125.degree. C.
60. The system of claim 38, further comprising a programmable
controller configured to substantially simultaneously control
operation of the coating unit and the lens curing unit during
use.
61. The system of claim 38, further comprising a programmable
controller configured to adjust a dose of the activating light
reaching the mold member as a function of the temperature of the
mold members.
62. The system of claim 38, further comprising a programmable
controller configured to vary an intensity of the light as a
function of the difference in the temperature of the molds over a
period of time.
63. The system of claim 38, further comprising a programmable
controller configured to control operation of the lens curing unit
using a Proportional-Integral-Derivative control scheme.
64. The system of claim 38, further comprising a programmable
controller and a light sensor configured to measure the dose of
light transmitted to the mold cavity, wherein the light sensor is
configured to communicate with the programmable controller, and
wherein the programmable controller varies the intensity or
duration of light such that a predetermined dose is transmitted to
the mold cavity.
65. The system of claim 38, wherein the lens curing unit comprises
a first light source and a second light source, and further
comprising a programmable controller configured to individually
control the first and second lights.
66. The system of claim 38, further comprising a cooling fan for
cooling the mold members during use, a thermocouple for measuring a
temperature of the mold members during use, and a programmable
controller configured to operate the cooling fan in response to the
temperature of the mold members.
67. The system of claim 38, wherein the coating unit is a
spin-coating unit, and further comprising a programmable controller
configured to control a rate of rotation of a holder of the spin
coating unit.
68. The system of claim 38, further comprising a post-cure unit,
the post-cure unit configured to simultaneously apply heat and
activating light to the interior of the post-cure unit, and a
programmable controller configured to substantially simultaneously
operate the coating unit, the lens curing unit, and the post-cure
unit.
69. The system of claim 38, further comprising a programmable
controller configured to control operation of the lens curing unit
as a function of the eyeglass lens prescription.
70. The system of claim 38, further comprising a liquid crystal
display positioned between an activating light source and one of
the mold members, and a programmable controller configured to
change the liquid crystal display in response to the prescription
of the eyeglass lens.
71. The system of claim 38, wherein the monomer comprises an
aromatic containing bis(allyl carbonate)-functional monomer.
72. A system for preparing an eyeglass lens, comprising: a first
mold member having a casting face and a non-casting face; a second
mold member having a casting face and a non-casting face, the
second mold member being adapted to be spaced apart from the first
mold member during use such that the casting faces of the first
mold member and the second mold member at least partially define a
mold cavity; a lens forming composition adapted to be disposed
within the mold cavity during use, comprising: a monomer that cures
by exposure to activating light to form the eyeglass lens during
use; a photoinitiator that initiates curing of the monomer in
response to being exposed to activating light during use; a lens
curing unit configured to cure at least a portion of a lens forming
composition into the eyeglass lens by directing activating light
toward mold members during use; and a post-cure unit configured to
apply heat and activating light to the eyeglass lens to
substantially complete curing of the eyeglass lens during use.
73. The system of claim 72, wherein the lens forming composition
further comprises photochromic compounds.
74. The system of claim 72, wherein the lens forming composition
further comprises ultraviolet/visible light absorbing
compounds.
75. A system for preparing an eyeglass lens, comprising: a first
mold member having a casting face and a non-casting face; a second
mold member having a casting face and a non-casting face, the
second mold member being adapted to be spaced apart from the first
mold member during use such that the casting faces of the first
mold member and the second mold member at least partially define a
mold cavity; a lens forming composition adapted to be disposed
within the mold cavity during use, comprising: a monomer that cures
by exposure to activating light to form the eyeglass lens during
use; a photoinitiator that initiates curing of the monomer in
response to being exposed to activating light during use; a coating
unit configured to produce a coating on at least one of the mold
members or the eyeglass lens during use; a lens curing unit
configured to cure at least a portion of a lens forming composition
into the eyeglass lens by directing activating light toward mold
members during use; a post-cure unit configured to apply heat and
activating light to the eyeglass lens to substantially complete
curing of the eyeglass lens during use; and a programmable
controller configured to substantially simultaneously control
operation of the coating unit, the lens curing unit, and the
post-cure unit during use.
76. The system of claim 75, wherein the lens forming composition
further comprises photochromic compounds.
77. The system of claim 75, wherein the lens forming composition
further comprises ultraviolet/visible light absorbing
compounds.
78. A programmable logic controller for controlling a lens forming
apparatus, the lens forming apparatus comprising: a first mold
member having a casting face and a non-casting face; a second mold
member having a casting face and a non-casting face, the second
mold member being spaced apart from the first mold member during
use such that the casting faces of the first mold member and the
second mold member at least partially define a mold cavity; a
coating unit configured to produce a coating on at least one of the
mold members or the eyeglass lens during use; and a lens curing
unit configured to direct activating light toward the mold members
during use; wherein the controller is configured to control the
operation of the lens curing unit.
79. The controller of claim 78, wherein the controller is
configured to substantially simultaneously control the operation of
the coating unit and the lens curing unit.
80. The controller of claim 79, wherein the coating unit is a spin
coating unit, and wherein the controller is configured to control
the rotation of the holder during use.
81. The controller of claim 78, wherein the coating unit comprises
a light source, and wherein the controller is configured to control
the light source during use.
82. The controller of claim 78, wherein the controller is
configured to measure the ambient room temperature, and wherein the
controller is configured to determine the appropriate dose of light
required to cure the lens forming composition, based on the ambient
room temperature.
83. The controller of claim 78, wherein the controller is
configured to adjust a dose of the activating light reaching the
mold member as a function of the temperature of the mold
members.
84. The controller of claim 78, wherein the controller is
configured to vary an intensity of the light as a function of the
difference in the temperature of the molds over a period of
time.
85. The controller of claim 78, wherein the controller is
configured to control operation of the lens curing unit using a
Proportional-Integral-D- erivative control scheme.
86. The controller of claim 78, wherein the apparatus further
comprises a light sensor configured to measure the dose of light
transmitted to the mold cavity, and wherein the light sensor is
configured to communicate with the controller, and wherein the
controller varies the intensity or duration of light such that a
predetermined dose is transmitted to the mold cavity.
87. The controller of claim 78, wherein the lens curing unit
comprises a first light source and a second light source, and
wherein the control unit is configured to individually control the
first and second light sources.
88. The controller of claim 78, wherein the apparatus further
comprises a cooling fan for cooling the mold members during use and
a sensor for measuring a temperature of the mold members during
use, and wherein the controller is configured to operate the
cooling fan in response to the temperature of the mold members.
89. The controller of claim 78, wherein the controller is
configured to determine when a lens curing process is complete by
monitoring a temperature response of a lens forming composition
during the application of activating light.
90. The controller of claim 78, further comprising a post-cure
unit, the post-cure unit configured to simultaneously apply heat
and activating light to the interior of the post-cure unit, and
wherein the controller is configured to substantially
simultaneously operate the coating unit, the lens curing unit, and
the post-cure unit.
91. The controller of claim 78, wherein the control unit is
configured to control operation of the lens curing unit as a
function of the eyeglass lens prescription.
92. The controller of claim 78, further comprising a liquid crystal
display positioned between an activating light source and one of
the mold members, and wherein the controller is configured to
change the liquid crystal display in response to the prescription
of the eyeglass lens.
93. The controller of claim 78, wherein the controller is
configured to perform system diagnostic checks.
94. The controller of claim 78, wherein the controller is
configured to notify the user when the system requires
maintenance.
95. The controller of claim 78, wherein the controller is
configured to display instructions for the operator during a lens
forming process.
96. A programmable logic controller for controlling a lens forming
apparatus, the lens forming apparatus comprising: a first mold
member having a casting face and a non-casting face; a second mold
member having a casting face and a non-casting face, the second
mold member being spaced apart from the first mold member during
use such that the casting faces of the first mold member and the
second mold member at least partially define a mold cavity; a
coating unit configured to produce a coating on at least one of the
mold members or the eyeglass lens during use; a lens curing unit
configured to direct activating light toward the mold members
during use; and a post-cure unit configured to apply heat and
activating light to the eyeglass lens; wherein the programmable
logic controller is configured to substantially simultaneously
control the operation of the coating unit, the lens curing unit,
and the post-cure unit.
97. A gasket configured to engage a first mold set for forming a
first lens of a first power, the gasket comprising at least four
discrete projections for spacing mold members of a mold set, and
wherein the projections are arranged on an interior surface of the
gasket.
98. The gasket of claim 97, wherein the at least four discrete
projections are evenly spaced around the interior surface of the
gasket.
99. The gasket of claim 97, wherein the at least four discrete
projections are spaced at about 90 degree increments around the
interior surface of the gasket.
100. The gasket of claim 97, wherein the gasket is configured to
engage a second mold set for forming a second lens of a second
power.
101. The gasket of claim 97, wherein the gasket comprises a fill
port for receiving a lens forming composition while the gasket is
fully engaged to a mold set.
102. The gasket of claim 101, wherein the gasket further comprises
an interior surface and an exterior surface, and wherein the fill
port extends from the interior surface of the gasket to the
exterior surface.
103. An assembly for making plastic prescription lenses,
comprising: a first mold set for forming a first lens of a first
power, the first mold set comprising a front mold member and a back
mold member; a gasket for engaging the first mold set, the gasket
comprising at least four discrete projections for spacing the front
mold member from the back mold member; and wherein the front mold
member, the back mold member, and the gasket at least partially
define a mold cavity for retaining a lens forming composition.
104. The assembly of claim 103, wherein the back mold member
comprises a steep axis and a flat axis, and wherein each of the at
least four discrete projections forms an oblique angle with the
steep axis and the flat axis of the back mold member.
105. The assembly of claim 103, wherein the back mold member
comprises a steep axis and a flat axis, and wherein each of the at
least four discrete projections forms an about 45 degree angle with
the steep axis and the flat axis of the back mold member.
106. The assembly of claim 103, wherein the gasket is configured to
engage a second mold set for forming a second lens of a second
power.
107. The assembly of claim 103, wherein the gasket further
comprises a fill port for receiving a lens forming composition
while the gasket is fully engaged to the mold set.
108. A method for making a plastic eyeglass lens, comprising:
engaging a gasket with a first mold set for forming a first lens of
a first power, wherein the first mold set comprises a front mold
member and a back mold member, and wherein the front mold member,
the back mold member, and the gasket at least partially define a
mold cavity for retainig a lens forming composition, and wherein
the gasket comprises at least four discrete projections arranged on
an interior surface thereof for spacing the first and second mold
members; introducing a lens forming composition into the mold
cavity; and curing the lens forming composition.
109. The method of claim 108, wherein the back mold member
comprises a steep axis and a flat axis, and wherein engaging a
gasket with a first mold set comprises positioning the first and
second mold members such that the at least four discrete
projections each form an oblique projection angle with the steep
axis and the flat axis of the back mold member.
110. The method of claim 108, wherein the back mold member
comprises a steep axis and a flat axis, and wherein engaging a
gasket with a first mold set comprises positioning the back mold
member such that the at least four discrete projections each form
an about 45 degree projection angle with the steep axis and the
flat axis of the back mold member.
111. The method of claim 108, further comprising: removing the
first mold set from the gasket; and engaging the gasket with a
second mold set for forming a second lens of a second power.
112. The method of claim 108, wherein the gasket further comprises
a fill port for receiving a lens forming composition while the
gasket is fully engaged to a mold set.
113. The method of claim 112, wherein the fill port extends from an
interior surface to an exterior surface of the gasket.
114. A method of forming a non-photochromic lens under photochromic
lens forming conditions comprising: placing a liquid lens forming
composition in a mold cavity defined by at least a first mold
member and a second mold member, the lens forming composition
comprising: a monomer that cures by exposure to activating light to
form the eyeglass lens during use; an ultraviolet/visible light
absorbing compound; a co-initiator that activates curing of the
monomer to form the eyeglass lens during use; and a photoinitiator
that is activated upon exposure to activating light; and directing
activating light toward the mold cavity, wherein the photoinitiator
activates the co-initiator in response to being exposed to the
activating light during use, and wherein activation of the
co-initiator causes the lens forming composition to at least
partially cure to form a non-photochromic lens during use.
115. The method of claim 114, further comprising applying a
hydrophobic coat to the eyeglass lens, wherein the hydrophobic
coating is adapted to inhibit the eyeglass lens from being exposed
to water and to ambient oxygen.
116. The method of claim 114, wherein the first mold member
comprises a casting face and a non-casting face, and further
comprising placing a first hardcoat layer upon said casting face
and a second hard coat layer upon said first hardcoat layer prior
to placing the liquid lens forming composition in the mold
cavity.
117. The method of claim 114, wherein the eyeglass lens is formed
from the lens forming composition in a time period of less than
about 30 minutes.
118. The method of claim 114, further comprising placing a filter
substantially adjacent to at least one of the mold members, wherein
the filter comprises a varying thickness such that the filter
varies an intensity distribution of the activating light directed
across the mold members.
119. The method of claim 114, further comprising placing a filter
substantially adjacent to at least one of the mold members, wherein
the filter comprises a varying transmissivity such that the filter
varies an intensity distribution of the activating light directed
across the mold members.
120. The method of claim 114, wherein the monomer comprises a
polyethylenic-functional monomer containing ethylenically
unsaturated groups selected from acrylyl or methacrylyl.
121. The method of claim 114, wherein the photoinitiator forms a
first polymer chain radical in response to being exposed to
activating light, and wherein the first polymer chain radical
reacts with the co-initiator, thereby forming a second polymer
chain radical.
122. The method of claim 114, wherein the activating light has a
wavelength in the range of about 380 to about 490 nanometers.
123. A filter for use in a lens forming apparatus, the filter
comprising a liquid crystal display panel, positionable between an
activating light source for producing activating light and a mold
assembly, wherein the liquid crystal display is configured to vary
an intensity of activating light when the activating light is
directed toward the mold assembly.
124. The filter of claim 123, wherein the liquid crystal display
panel is configured to produce a pattern of light and dark areas,
wherein the dark areas reduce the intensity of the activating light
reaching the mold assembly to a greater extent than the light
areas.
125. The filter of claim 123, wherein the liquid crystal display
panel is configured to produce a pattern of light and dark areas,
and wherein the liquid crystal display panel is further configured
to allow the pattern to be altered during a curing cycle.
126. The filter of claim 123, wherein the liquid crystal display
panel is configured to produce a predetermined pattern of light and
dark area, the predetermined pattern being selected based on a
prescription of a lens defined by the mold assembly.
127. The filter of claim 123, wherein the liquid crystal display
panel is configured to become substantially entirely darkened, such
that the activating light is substantially inhibited from reaching
the mold assembly.
128. The filter of claim 123, wherein the liquid crystal display
panel is configured to be alternated between a transmissive state
and a darkened state, such that pulses of activating light are
directed toward the mold members.
129. The filter of claim 123, wherein the lens forming apparatus
further comprises an additional mold assembly, and wherein the
liquid crystal display panel is positioned between the activating
light source and the additional mold assembly, and wherein the
liquid crystal display panel is configured to produce a first
pattern of light and dark areas between the activating light source
and the mold assembly, and wherein the liquid crystal display panel
is configured to produce a second pattern of light and dark areas
between the activating light source and the additional mold
assembly.
130. The filter of claim 129, wherein the first and second patterns
are independently variable during a curing cycle.
131. The filter of claim 123, wherein the liquid crystal display
pattern is configured to be connected to a controller, the
controller being configured to alter a pattern of light and dark
areas displayed on the liquid crystal display panel in response to
lens curing conditions.
132. A method of forming a plastic eyeglass lens comprising:
placing a liquid lens forming composition in a mold cavity defined
by at least a first mold member and a second mold member, the lens
forming composition comprising: a monomer that cures by exposure to
activating light to form the eyeglass lens during use; a
photoinitiator that initiates curing of the monomer in response to
being exposed to activating light during use; directing activating
light toward the mold cavity, the activating light causing the lens
forming composition to at least partially cure; and filtering the
activated light with a filter, the filter comprising a liquid
crystal display panel, wherein the liquid crystal display panel is
configured to vary an intensity of activating light as the
activating light is directed toward the mold members.
133. The method of claim 132, wherein filtering the activated light
comprises forming a pattern of light and dark areas on the liquid
crystal display panel, wherein the dark areas reduce the intensity
of the activating light reaching the mold assembly to a greater
extent than the light areas.
134. The method of claim 133, further comprising altering the
pattern while light is directed toward the mold cavity.
135. The method of claim 132, wherein filtering the activated light
comprises forming a predetermined pattern of light and dark areas
on the liquid crystal display panel, the predetermined pattern
being selected based on a prescription of a lens defined by the
mold cavity.
136. The method of claim 132, wherein filtering the activated light
comprises substantially darkening the potion of the liquid crystal
display panel between the mold cavity and the activating light such
that the activating light is substantially inhibited from reaching
the mold assembly.
137. The method of claim 132, wherein filtering the activated light
comprises alternating the liquid crystal display panel between a
transmissive state and a darkened state such that pulses of
activating light are directed toward the mold members.
138. The method of claim 132, wherein filtering the activating
light comprises producing a pattern of light and dark areas on the
liquid crystal display panel and altering the pattern in response
to lens curing conditions.
139. The method of claim 132, wherein the altering of the pattern
is performed by a controller coupled to the liquid crystal display
panel.
140. A composition curable by exposure to activating light to form
a photochromic plastic eyeglass lens, the composition comprising: a
monomer that cures by exposure to activating light to form the
eyeglass lens during use; a photoinitiator that initiates curing of
the monomer in response to being exposed to activating light during
use; a first photochromic composition adapted, when cured in an
eyeglass lens and subsequently exposed to photochromic activating
light during use, to exhibit a first color; a second photochromic
composition adapted, when cured in an eyeglass lens and
subsequently exposed to photochromic activating light during use,
to exhibit a second color; a light effector composition, wherein
the light effector composition is adapted to affect the activated
color of the photochromic plastic eyeglass lens such that the
photochromic plastic eyeglass lens, when exposed to photochromic
activating light, selectively exhibits the first color, the second
color, or a third color during use.
141. The composition of claim 140, wherein the light effector
composition selectively affects the absorptivity of the first
photochromic composition or the second photochromic composition to
cause the eyeglass lens, when exposed to photochromic activating
light, to exhibit a predetermined color.
142. The composition of claim 140, wherein the light effector
composition selectively affects the absorptivity of the first
photochromic composition and the second photochromic composition to
cause the eyeglass lens, when exposed to photochromic activating
light, to exhibit a predetermined color.
143. The composition of claim 140, wherein the light effector
composition comprises a photo initiator.
144. The composition of claim 140, wherein the light effector
composition comprises a non-photochromic ultraviolet/visible light
absorber.
145. The composition of claim 140, wherein the light effector
composition comprises a non-photochromic dye.
146. The composition of claim 140, wherein the light effector
composition comprises an ultraviolet light stabilizer.
147. The composition of claim 140, wherein the first and second
photochromic compositions comprise a spirooxazine, a spiropyran, a
spironaphthoxazine, a spiropyridobenzoxazine, a spirobenzoxazine, a
napthopyran, a benzopyran, a spironapthopyran, an
indolinospironapthoxazi- ne, an indolinospironapthopyran, a
diarylnapthopyran, an organometallic, or a phenylmercury.
148. The composition of claim 140, wherein the monomer comprises a
polyethylenic-functional monomer containing ethylenically
unsaturated groups selected from acrylyl or methacrylyl.
149. The composition of claim 140, wherein the monomer comprises an
aromatic containing bis(allyl carbonate)-functional monomer.
150. The composition of claim 140, wherein the first photochromic
composition comprises Reversacol Sea Green and the second
photochromic composition comprises Reversacol Berry Red.
151. The composition of claim 150, wherein the light effector
composition comprises monomethylether hydroquinone, and wherein the
eyeglass lens, when exposed to photochromic activating light,
selectively exhibits a brown color.
152. The composition of claim 150, wherein the light effector
composition comprises a mixture of
2-[4-((2-hydroxy-3-dodecyloxypropyl)oxy)-2-hydroxy-
phenyl]4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine and
2-[4-((2-hydroxy-3-tridecyloxypropyl)-oxy]-2-hydroxyphenyl]4,6-bis(2,4-di-
methylpheyl-1,3,5-triazine, and wherein the eyeglass lens, when
exposed to photochromic activating light, selectively exhibits an
aqua-green color.
153. The composition of claim 150, wherein the light effector
composition comprises 2-isopropyl-thioxanthone, and wherein the
eyeglass lens, when exposed to photochromic activating light,
selectively exhibits a yellow-green color.
154. The composition of claim 150, wherein the light effector
composition comprises
2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone, and
wherein the eyeglass lens, when exposed to photochromic activating
light, selectively exhibits a green color.
155. A composition curable by exposure to activating light to form
a photochromic plastic eyeglass lens, the composition comprising: a
monomer that cures by exposure to activating light to form the
eyeglass lens during use; a photoinitiator that initiates curing of
the monomer in response to being exposed to activating light during
use; a first photochromic composition adapted, when cured in an
eyeglass lens and subsequently exposed to photochromic activating
light during use, to exhibit a first color; a second photochromic
composition adapted, when cured in an eyeglass lens and
subsequently exposed to photochromic activating light during use,
to exhibit a second color; a light effector composition, wherein
the light effector composition is adapted to affect the activated
color of the photochromic plastic eyeglass lens such that the
photochromic plastic eyeglass lens, when exposed to photochromic
activating light, selectively exhibits a third color which
substantially differs from the first and second colors during
use.
156. A composition curable by exposure to activating light to form
a photochromic plastic eyeglass lens, the composition comprising: a
monomer composition comprising an aromatic containing bis(allyl
carbonate)-functional monomer; a co-initiator composition
configured to activate curing of the monomer composition to form
the eyeglass lens during use comprising an acrylated amine; and a
photoinitiator configured to activate the co-initiator composition
in response to being exposed to activating light during use; and a
dye composition adapted to, when cured in an eyeglass lens, cause
the eyeglass lens to exhibit a second color; and wherein the dye
composition acts as a light effector composition on the
photochromic composition such that the photochromic activity of the
photochromic compound is reduced, and wherein a color of the
photochromic plastic eyeglass lens, when exposed to activating
light, exhibits a third color.
157. A method of altering an activated color of a photochromic lens
comprising: mixing a first photochromic composition adapted, when
cured in an eyeglass lens and subsequently exposed to photochromic
activating light during use, to exhibit a first color, with a
second photochromic composition adapted, when cured in an eyeglass
lens and subsequently exposed to photochromic activating light
during use, to exhibit a second color, to form a first
polymerizable lens forming composition; adding a light effector
composition to the polymerizable lens forming composition to form a
second polymerizable lens forming composition; and curing the
second polymerizable lens forming composition to form an eyeglass
lens; wherein the activated color of the eyeglass lens differs from
an activated color of an eyeglass lens formed from the first
polymerizable lens forming composition.
158. A kit for preparing a composition curable by exposure to
activating light to form a photochromic plastic eyeglass lens, the
kit comprising: a base composition comprising: a monomer that cures
by exposure to activating light to form the eyeglass lens during
use; and a photoinitiator that initiates curing of the monomer in
response to being exposed to activating light during use; a first
photochromic composition adapted, when cured in an eyeglass lens
and subsequently exposed to photochromic activating light during
use, to exhibit a first color; a second photochromic composition
adapted, when cured in an eyeglass lens and subsequently exposed to
photochromic activating light during use, to exhibit a second
color; at least two light effector compositions; wherein a first
light effector composition is adapted, when mixed with the first
photochromic composition, the second photochromic composition, and
the base composition, and after such mixture is cured to form an
eyeglass lens, to affect the activated color of the eyeglass lens
such that the eyeglass lens, when exposed to photochromic
activating light, selectively exhibits a third color during use;
and wherein a second light effector composition is adapted, when
mixed with the first photochromic composition, the second
photochromic composition, and the base composition, and after such
mixture is cured to form an eyeglass lens, to affect the activated
color of the eyeglass lens such that the eyeglass lens, when
exposed to photochromic activating light, selectively exhibits a
fourth color during use.
159. A lens forming composition curable upon exposure to activating
light to form a plastic eyeglass lens, comprising: a monomer
composition comprising an aromatic containing polyethylenic
polyether functional monomer; and a photoinitiator configured to
initiate polymerization of the monomer composition in response to
being exposed to activating light during use.
160. The lens forming composition of claim 159 wherein the aromatic
containing polyethylenic polyether functional monomer comprises an
aromatic containing polyether polyethylenic functional monomer
containing at least one group selected from acrylyl or
methacrylyl.
161. The lens forming composition of claim 159 wherein the aromatic
containing polyethylenic polyether functional monomer comprises an
ethoxylated bisphenol A containing at least one group selected from
acrylyl or methacrylyl.
162. The lens forming composition of claim 159 wherein the aromatic
containing polyethylenic polyether functional monomer comprises an
ethoxylated bisphenol A di(meth)acrylate.
163. The lens forming composition of claim 159 wherein the aromatic
containing polyethylenic polyether functional monomer comprises
ethoxylated 4 bisphenol A dimethacrylate.
164. The lens forming composition of claim 159 wherein the monomer
composition further comprises a polyethylenic functional
monomer.
165. The lens forming composition of claim 164 wherein the
polyethylenic functional monomer comprises
tris(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated 10
bisphenol A dimethacrylate, ethoxylated 4 bisphenol A
dimethacrylate, dipentaerythritol pentaacrylate, 1,6-hexanediol
dimethacrylate, isobornyl acrylate, bisphenol A bis allyl
carbonate, pentaerythritol triacrylate or mixtures thereof.
166. The lens forming composition of claim 159 wherein the aromatic
containing polyethylenic polyether functional monomer comprises an
ethoxylated bisphenol A di(meth)acrylate, and wherein the monomer
composition further comprises a polyethylenic functional
monomer.
167. The lens forming composition of claim 159 wherein the aromatic
containing polyethylenic polyether functional monomer comprises an
ethoxylated bisphenol A di(meth)acrylate, and wherein the monomer
composition further comprises a polyethylenic functional monomer,
and wherein the polyethylenic functional monomer comprises
tris(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated 10
bisphenol A dimethacrylate, ethoxylated 4 bisphenol A
dimethacrylate, dipentaerythritol pentaacrylate, 1,6-hexanediol
dimethacrylate, isobornyl acrylate, bisphenol A bis allyl
carbonate, pentaerythritol triacrylate or mixtures thereof.
168. The lens forming composition of claim 159, further comprising
a co-initiator composition, wherein the co-initiator composition
comprises an amine.
169. The lens forming composition of claim 159, further comprising
a co-initiator composition, wherein the co-initiator composition
comprises an acrylyl amine.
170. The lens forming composition of claim 159, further comprising
a co-initiator composition, wherein the co-initiator composition
comprises an ethanol amine.
171. The lens forming composition of claim 159, further comprising
a co-initiator composition, wherein the co-initiator composition
comprises an aromatic amine.
172. The lens forming composition of claim 159, further comprising
a co-initiator composition, wherein the co-initiator composition
comprises an acrylyl amine, the acrylyl amine comprising
monoacrylated amines, diacrylated amines, or mixtures thereof.
173. The lens forming composition of claim 159, further comprising
a co-initiator composition, wherein the co-initiator composition
comprises CN 384 and CN-386.
174. The lens forming composition of claim 159, further comprising
a co-initiator composition, wherein the co-initiator is an amine,
and wherein an amount of the co-initiator composition in the lens
forming composition ranges from about 500 ppm to about 7% by
weight.
175. The lens forming composition of claim 159 wherein the
photoinitiator composition comprises
bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylphenyl)ph- osphine
oxide.
176. The lens forming composition of claim 159 wherein the
photoinitiator composition comprises
bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylphenyl)ph- osphine oxide
and 1-hydroxycyclohexylphenyl ketone.
177. The lens forming composition of claim 159 wherein an amount of
the photoinitiator composition in the lens forming composition
ranges from about 50 ppm to about 0.5%.
178. The lens forming composition of claim 159 further comprising a
co-initiator, wherein the photoinitiator composition comprises
bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylphenyl)phosphine oxide
and 2-isopropylthioxanthone.
179. The lens forming composition of claim 159 further comprising a
co-initiator, wherein the photoinitiator composition comprises
bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylphenyl)phosphine
oxide.
180. The lens forming composition of claim 159 wherein the
photoinitiator composition comprises
bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylphenyl)ph- osphine oxide
and 2-isopropylthioxanthone.
181. The lens forming composition of claim 159 further comprising a
co-initiator, wherein the photoinitiator composition comprises
2-isopropylthioxanthone.
182. The lens forming composition of claim 159, further comprising
an activating light absorbing compound.
183. The lens forming composition of claim 159, further comprising
a photochromic compound.
184. The lens forming composition of claim 159, further comprising
a photochromic compound, and wherein the photochromic compound
comprises a spirooxazine, spiropyrans, spironaphthoxazines,
spiropyridobenzoxazines, spirobenzoxazines, napthopyrans
benzopyrans, spironapthopyrans, indolinospironapthoxazines,
indolinospironapthopyrans, diarylnapthopyrans, organometallic, or
phenylmercury.
185. The lens forming composition of claim 159, further comprising
a photochromic composition, wherein the photochromic composition
comprises Corn Yellow, Berry Red, Sea Green, Plum Red, Variacrol
Yellow, Palatinate Purple, CH-94, Variacrol Blue D, Oxford Blue,
CH-266 or mixtures thereof.
186. The lens forming composition of claim 159, further comprising
a photochromic compound, and wherein an amount of photochromic
compound in the lens forming composition ranges from about 50 ppm
to about 1000 ppm.
187. The lens forming composition of claim 159, further comprising
an ultraviolet absorbing compound for inhibiting at least a portion
of ultraviolet light from being transmitted through the eyeglass
lens during use.
188. The lens forming composition of claim 159, further comprising
an ultraviolet absorbing compound for inhibiting at least a portion
of ultraviolet light from being transmitted through the eyeglass
lens during use, wherein the ultraviolet absorbing compound
comprises 2-(2H
benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol,
2-hydroxy-4-methoxybenzophenone, mixtures of
2-[4-((2-hydroxy-3-dodecylox-
ypropyl)-oxy)-2-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-
e and
2-[4-((2-hydroxy-3-tridecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(-
2,4-dimethylpheyl)-1,3,5-triazine, mixtures of poly
(oxy-1,2-ethanediyl) and
.alpha.-(3-(3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyp-
henyl)-1-oxopropyl)-.gamma.-hydroxy,
.alpha.-(3-(3-(2H-benzotriazol-2-yl)--
5-(1,1-dimethylethyl)-4-hydroxyphenyl)-1-oxopropyl)-.gamma.-(3-(3-(2H-benz-
otriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl)-1-oxopropoxy),
2-(2-hydroxy-5-methylphenyl) benzotriazole,
ethyl-2-cyano-3,3-diphenylacr- ylate, or phenyl salicylate.
189. The lens forming composition of claim 159, further comprising
an ultraviolet absorbing compound for inhibiting at least a portion
of ultraviolet light from being transmitted through the eyeglass
lens during use, wherein the ultraviolet absorbing compound
comprises
2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol.
190. The lens forming composition of claim 159, further comprising
an UV absorbing composition for inhibiting at least a portion of
ultraviolet light from being transmitted through the eyeglass lens
during use, wherein the UV absorbing composition comprises a
photoinitiator and a UV absorbing compound.
191. The lens forming composition of claim 159, further comprising
a dye to form a background color within the lens.
192. The lens forming composition of claim 159 further comprising a
UV stabilizer for inhibiting degradation of the cured monomer
caused by exposure to ultraviolet light.
193. The lens forming composition of claim 159 wherein the lens
forming composition is curable to a substantially aberration free
lens in less than about 30 minutes.
194. A method for making a plastic eyeglass lens, comprising:
placing a liquid lens forming composition in a mold cavity defined
by at least a first mold member and a second mold member, the lens
forming composition comprising: a monomer composition comprising an
aromatic containing polyethylenic polyether functional monomer; and
a photoinitiator configured to initiate polymerization of the
monomer composition in response to being exposed to activating
light during use; and directing activating light toward at least
one of the mold members to cure the lens forming composition to
form the eyeglass lens.
195. The method of claim 194 wherein curing the lens forming
composition comprises polymerizing the monomer composition.
196. The method of claim 194 wherein directing activating light to
the lens forming composition comprises applying a plurality of
activating light pulses to the lens forming composition.
197. The method of claim 194, further comprising applying a
hydrophobic coating to the eyeglass lens.
198. The method of claim 194, further comprising applying a
hydrophobic coating to the eyeglass lens, wherein the hydrophobic
coating is adapted to inhibit the eyeglass lens from being exposed
to water and to ambient oxygen.
199. The method of claim 194 wherein the first mold member
comprises a casting face and a non-casting face, and further
comprising placing a first hardcoat layer upon said casting face
and a second hardcoat layer upon said first hardcoat layer prior to
placing the liquid lens forming composition in the mold cavity.
200. The method of claim 194 wherein the second mold member
comprises a casting face and a non-casting face, and further
comprising placing a material capable of being tinted upon the
casting face prior to placing the liquid lens forming composition
in the mold cavity.
201. The method of claim 194 wherein the second mold member
comprises a casting face and a non-casting face, and further
comprising placing a material capable of being tinted upon the
casting face prior to placing the liquid lens forming composition
in the mold cavity, and further comprising applying dye to the
material to tint the lens forming composition.
202. The method of claim 194, further comprising applying an
adhesion-promoter coating to an inner surface of the first mold
member and an inner surface of the second mold member to
substantially adhere the lens forming composition to the first and
second mold members during use.
203. The method of claim 194 wherein the activating light is
removed from the mold members when substantially all of the lens
forming composition has reached its gel point.
204. The method of claim 194 wherein the activating light comprises
a first intensity, and herein the activating light is directed
toward at least one of the mold members until substantially all of
the lens forming composition has reached its gel point, and further
comprising directing activating light having a second intensity
towards at least one mold member to cure substantially all of the
lens forming composition, the first intensity being greater than
the second intensity.
205. The method of claim 194 wherein the activating light is
directed toward at least one of the mold members until
substantially all of the lens forming composition has reached its
gel point, and further comprising inhibiting the activating light
from further being directed toward the mold members, thereby
allowing substantially all of the lens forming composition to
cure.
206. The method of claim 194 wherein the eyeglass lens is formed
from the lens forming composition in a time period of less than
about 10 minutes.
207. The method of claim 194 wherein the eyeglass lens is formed
from the lens forming composition in a time period of less than
about 30 minutes.
208. The method of claim 194 wherein the First mold member is
spaced apart from the second mold member by a gasket, and further
comprising removing the gasket subsequent to directing activating
light to at least one of the mold members to expose the lens
forming composition to ambient air for approximately 5 to 30
minutes, thereby cooling the lens forming composition, and further
comprising directing additional activating light toward at least
one of the mold members to at least partially cure the lens forming
composition.
209. The method of claim 194, further comprising heating the cured
lens forming composition to a temperature between approximately
100.degree. C. to 120.degree. C. for approximately 3 to 15 minutes
subsequent to curing the lens forming composition.
210. The method of claim 194, further comprising placing a filter
substantially adjacent to at least one of the mold members, wherein
the filter comprises a varying thickness such that the filter
varies an intensity distribution of activating light across the
mold members.
211. The method of claim 194 wherein an amount of activating light
is directed towards the mold cavity, and wherein the mold cavity
comprises a temperature, and wherein the amount of activating light
directed to the mold cavity is a function of the temperature of at
least a portion of the mold cavity.
212. The method of claim 194 wherein directing light to the lens
forming composition comprises applying a number of activating light
pulses to the lens forming composition, wherein the number of light
pulses is a function of a change in a temperature of the lens
forming composition over a period of time.
213. The method of claim 194 wherein directing light to the lens
forming composition comprises applying a plurality of activating
light pulses to the lens forming composition, wherein a duration of
the light pulses is a function of a change in a temperature of the
lens forming composition over a period of time.
214. The method of claim 194 wherein directing light to the lens
forming composition comprises applying a plurality of activating
light pulses to the lens forming composition, wherein an intensity
of the light pulses is a function of a change in a temperature of
the lens forming composition over a predetermined period of
time.
215. A lens made by the method of claim 194.
216. A lens forming composition curable upon exposure to activating
light to form a plastic eyeglass lens, comprising: a monomer
composition comprising an aromatic containing polyether
polyethylenic functional monomer containing groups selected from
acrylyl or methacrylyl; a co-initiator composition configured to
activate curing of the monomer composition to form the eyeglass
lens during use, the co-initiator comprising an acrylyl amine; and
a photoinitiator configured to activate the co-initiator
composition in response to being exposed to activating light during
use.
217. A method for making a plastic eyeglass lens, comprising:
placing a liquid lens forming composition in a mold cavity defined
by at least a first mold member and a second mold member, the lens
forming composition comprising: a monomer composition comprising an
aromatic containing polyether polyethylenic functional monomer
containing groups selected from acrylyl or methacrylyl; a
co-initiator composition configured to activate curing of the
monomer composition to form the eyeglass lens during use, the
co-initiator composition comprising an acrylyl amine; and a
photoinitiator configured to activate the co-initiator composition
in response to being exposed to activating light during use; and
directing activating light toward at least one of the mold members
to cure the lens forming composition to form the eyeglass lens.
218. A lens forming composition curable upon exposure to activating
light to form a plastic eyeglass lens, comprising: a monomer
composition comprising an aromatic containing polyether
polyethylenic functional monomer containing groups selected from
acrylyl or methacrylyl; and a photoinitiator configured to initiate
polymerization of the monomer composition in response to being
exposed to activating light during use.
219. A lens forming composition curable upon exposure to activating
light to form a plastic eyeglass lens, comprising: a monomer
composition comprising an aromatic containing polyether
polyethylenic functional monomer, a co-initiator composition
configured to activate curing of the monomer composition to form
the eyeglass lens during use, the co-initiator composition
comprising an amine; and a photoinitiator configured to activate
the co-initiator composition in response to being exposed to
activating light during use.
220. The lens forming composition of claim 219, further comprising
an activating light absorbing composition.
221. The lens forming composition of claim 219 wherein the
photoinitiator composition is configured to form a polymer chain
radical in response to being exposed to ultraviolet light during
use, and wherein the polymer chain radical reacts with the
co-initiator composition to form a monomer initiating species
during use, and wherein the polymer chain radical and the monomer
initiating species react with the monomer composition to polymerize
the monomer composition during use.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to eyeglass lenses.
More particularly, the invention relates to a lens forming
composition, system and method for making photochromic,
ultraviolet/visible light absorbing, and colored plastic lenses by
curing the lens forming composition using activating light.
[0003] 2. Description of the Relevant Art
[0004] It is conventional in the art to produce optical lenses by
thermal curing techniques from the polymer of diethylene glycol
bis(allyl)-carbonate (DEG-BAC). In addition, optical lenses may
also be made using ultraviolet ("UV") light curing techniques. See,
for example, U.S. Pat. No. 4,728,469 to Lipscomb et al., U.S. Pat.
No. 4,879,318 to Lipscomb et al., U.S. Pat. No. 5,364,256 to
Lipscomb et al., U.S. Pat. No. 5,415,816 to Buazza et al., U.S.
Pat. No. 5,529,728 to Buazza et al., U.S. Pat. No. 5,514,214 to
Joel et al., U.S. Pat. No. 5,516,468 to Lipscomb, et al., U.S. Pat.
No. 5,529,728 to Buazza et al., U.S. Pat. No. 5,689,324 to Lossman
et al., and U.S. patent application Ser. No. 07/425,371 filed Oct.
26, 1989, Ser. No. 08/439,691 filed May 12, 1995, Ser. No.
08/454,523 filed May 30, 1995, Ser. No. 08/453,770 filed May 30,
1995, Ser. No. 08/636,510 filed Apr. 19, 1996, Ser. No. 08/663,703
filed Jun. 14, 1996, Ser. No. 08/666,062 filed Jun. 14, 1996, Ser.
No. 08/853,134 filed May 8, 1997, Ser. No. 08/844,557 filed Apr.
18, 1997, Ser. No. 08/904,289 filed Jul. 31, 1997, and Ser. No.
08/959,973 filed Oct. 29, 1997, all of which are hereby
specifically incorporated by reference.
[0005] Curing of a lens by ultraviolet light tends to present
certain problems that must be overcome to produce a viable lens.
Such problems include yellowing of the lens, cracking of the lens
or mold, optical distortions in the lens, and premature release of
the lens from the mold. In addition, many of the useful ultraviolet
light-curable lens forming compositions exhibit certain
characteristics that increase the difficulty of a lens curing
process. For example, due to the relatively rapid nature of
ultraviolet light initiated reactions, it is a challenge to provide
a composition that is ultraviolet light curable to form an eyeglass
lens. Excessive exothermic heat tends to cause defects in the cured
lens. To avoid such defects, the level of photoinitiator may be
reduced to levels below what is customarily employed in the
ultraviolet curing art.
[0006] While reducing the level of photoinitiator addresses some
problems, it may also cause others. For instance, lowered levels of
photoinitiator may cause the material in regions near an edge of
the lens and proximate a gasket wall in a mold cavity to
incompletely cure due to the presence of oxygen in these regions
(oxygen is believed to inhibit curing of many lens forming
compositions or materials). Uncured lens forming composition tends
to result in lenses with "wet" edges covered by sticky uncured lens
forming composition. Furthermore, uncured lens forming composition
may migrate to and contaminate the optical surfaces of the lens
upon demolding. The contaminated lens is then often unusable.
[0007] Uncured lens forming composition has been addressed by a
variety of methods (see, e.g., the methods described in U.S. Pat.
No. 5,529,728 to Buazza et al). Such methods may include removing
the gasket and applying either an oxygen barrier or a
photoinitiator enriched liquid to the exposed edge of the lens, and
then re-irradiating the lens with a dosage of ultraviolet light
sufficient to completely dry the edge of the lens prior to
demolding. During such irradiation, however, higher than desirable
levels of irradiation, or longer than desirable periods of
irradiation, may be required. The additional ultraviolet
irradiation may in some circumstances cause defects such as
yellowing in the lens.
[0008] The low photoinitiator levels utilized in many ultraviolet
curable lens forming compositions may produce a lens that, while
fully-cured as measured by percentage of remaining double bonds,
may not possess sufficient cross-link density on the lens surface
to provide desirable dye absorption characteristics during the
tinting process.
[0009] Various methods of increasing the surface density of such
ultraviolet light curable lenses are described in U.S. Pat. No.
5,529,728 to Buazza et al. In one method, the lens is de-molded and
then the surfaces of the lens are exposed directly to ultraviolet
light. The relatively short wavelengths (around 254 nm) provided by
some ultraviolet light sources (e.g., a mercury vapor lamp) tend to
cause the material to cross-link quite rapidly. An undesirable
effect of this method, however, is that the lens tends to yellow as
a result of such exposure. Further, any contaminants on the surface
of the lens that are exposed to short wavelengths of high intensity
ultraviolet light may cause tint defects.
[0010] Another method involves exposing the lens to relatively high
intensity ultraviolet radiation while it is still within a mold
cavity formed between glass molds. The glass molds tend to absorb
the more effective short wavelengths, while transmitting
wavelengths of about 365 nm. This method generally requires long
exposure times and often the infrared radiation absorbed by the
lens mold assembly will cause premature release of the lens from a
mold member. The lens mold assembly may be heated prior to exposure
to high intensity ultraviolet light, thereby reducing the amount of
radiation necessary to attain a desired level of cross-link
density. This method, however, is also associated with a higher
rate of premature release.
[0011] It is well known in the art that a lens mold/gasket assembly
may be heated to cure the lens forming composition from a liquid
monomer to a solid polymer. It is also well known that such a lens
may be thermally postcured by applying convective heat to the lens
after the molds and gaskets have been removed from the lens.
[0012] In this application the terms "lens forming material" and
"lens forming compositions" are used interchangeably.
SUMMARY OF THE INVENTION
[0013] An embodiment of an apparatus for preparing an eyeglass lens
is described. The apparatus includes a coating unit and a lens
curing unit. The coating unit may be configured to coat either mold
members or lenses. Preferably, the coating unit is a spin coating
unit. The lens curing unit may be configured to direct activating
light toward mold members. The mold members are part of a mold
assembly that may be placed within the lens curing unit. Depending
on the type of lens forming composition used, the apparatus may be
used to form photochromic and non-photochromic lenses. The
apparatus is preferably configured to allow the operation of both
the coating unit and the lens curing unit substantially
simultaneously.
[0014] The coating unit is preferably a spin coating unit. The spin
coating unit preferably comprises a holder for holding an eyeglass
lens or a mold member. The holder is preferably coupled to a motor
that is preferably configured to rotate the holder. An activating
light source may be incorporated into a cover. The cover may be
drawn over the body of the lens curing unit, covering the coating
units. The activating light source is preferably positioned, when
the cover is closed, such that activating light may be applied to
the mold member or lens positioned within the coating unit. An
activating light source may be an ultraviolet light source, an
actinic light source (e.g., a light source producing light having a
wavelength between about 380 nm to 490 nm), a visible light source
and/or an infra-red light source. Preferably, the activating light
source is an ultraviolet light source.
[0015] The lens curing unit includes at least one, preferably two
activating light sources for irradiating a mold assembly. Mold
assembly holders may be positionable within the lens forming
apparatus such that the activating light may be applied to the mold
member during use. A filter is preferably positioned between the
mold assemblies and the activating light source. The filter is
preferably configured to manipulate the intensity of activating
light that is directed toward the mold members. The filter may be a
hazy filter that includes a frosted glass member. Alternatively,
the filter may be a liquid crystal display ("LCD") panel.
[0016] An LCD panel for use as a filter is preferably a monochrome
trans-flective panel with the back light and reflector removed. The
intensity of the light is preferably reduced as the light passes
through the LCD panel. The LCD panel is preferably programmable
such that the light transmissibility of the LCD panel may be
altered. In use, a predetermined pattern of light and dark regions
may be displayed on the LCD panel to alter the intensity of light
passing through the panel. One advantage of an LCD panel filter is
that a pattern may be altered during a curing cycle. For example,
the pattern of light and dark regions may be manipulated such that
a lens is initially cured from the center of the lens, then the
curing may be gradually expanded to the outer edges of the lens.
This type of curing pattern may allow a more uniformly cured lens
to be formed.
[0017] Another advantage is that the LCD panel may be used as a
partial shutter to reduce the intensity of light reaching the mold
assembly. By blackening the entire LCD panel the amount of light
reaching any portion of the mold assembly may be reduced. In this
manner, the LCD may be used to create "pulses" of light by
alternating between a transmissive and darkened mode.
[0018] In another embodiment, an LCD panel may be used to allow
different patterns and/or intensities of light to reach two
separate mold assemblies. If the mold assemblies are being used to
create lenses having significantly different powers, each mold
assembly may require a significantly different light irradiation
pattern and/or intensity. The use of an LCD filter may allow the
irradiation of each of the mold assemblies to be controlled
individually.
[0019] When non-LCD type filters are used, it may be necessary to
maintain a library of filters for use in the production of
different types of prescription lenses. Typically, each individual
prescription will need a particular filter pattern to obtain a high
quality lens. Since an LCD panel is programmable in a variety of
patterns, it is believed that one may use a single LCD panel,
rather than a library of filters. The LCD panel may be programmed
to fit the needs of the specific type of lens being formed.
[0020] The LCD panel filters may be coupled to a programmable logic
device that may be used to design and store patterns for use during
curing. FIGS. 7-10 show a number of patterns that may be generated
on an LCD panel and used to filter activating light. Each of these
patterns is preferably used for the production of a lens having a
specific prescription power.
[0021] The lens forming apparatus may include a post-cure unit. The
post-cure unit is preferably configured to apply heat and
activating light to mold assemblies or lenses disposed within the
post-cure unit.
[0022] The lens forming apparatus may also include a programmable
controller configured to substantially simultaneously control the
operation of the coating unit, the lens curing unit and the
post-cure unit. The apparatus may include a number of light probes
and temperature probes disposed within the coating unit, lens
curing unit, and the post-cure unit. These probes preferably relay
information about the operation of the individual units to the
controller. The information relayed may be used to control the
operation of the individual units. The operation of each of the
units may also be controlled based on the prescription of the lens
being formed.
[0023] The controller may be configured to control various
operations of the coating unit. For example, when a spin coating
unit is used the controller may control the rotation of the lens or
mold member during a coating process (e.g., whether the lens or
mold members are rotated or not and/or the speed of rotation) and
the operation of the coating unit lamps (e.g., whether the lamps
are on or off and/or the time the lamps are on).
[0024] The controller may also be configured to control the various
operations of the lens curing unit. Some of the operations that may
be controlled or measured by the controller include: (i) measuring
the ambient room temperature; (ii) determining the dose of light
(or initial dose of light in pulsed curing applications) required
to cure the lens forming composition, based on the ambient room
temperature; (iii) applying the activating light with an intensity
and duration sufficient to equal the determined dose; (iv)
measuring the composition's temperature response during and
subsequent to the application of the dose of light; (v) calculating
the dose required for the next application of activating light (in
pulsed curing applications); (vi) applying the activating light
with an intensity and duration sufficient to equal the determined
second dose; (vii) determining when the curing process is complete
by monitoring the temperature response of the lens forming
composition during the application of activating light; (viii)
turning the upper and lower light sources on and off independently;
(ix) monitoring the lamp temperature, and controlling the
temperature of the lamps by activating cooling fans proximate the
lamps; and (x) turning the fans on/off or controlling the flow rate
of an air stream produced by a fan to control the composition
temperature;
[0025] The controller may also be configured to control the
operation of the post-cure unit. Some of the operations that may be
controlled include control of the operation of the lamps (e.g.,
whether the lamps are on or off and the time the lamps are on); and
operation of the heating device (e.g., whether the heating unit is
turned on or off and/or the amount of heat produced by the heating
device).
[0026] Additionally, the controller provides system diagnostics and
information to the operator of the apparatus. The controller may
notify the user when routine maintenance is due or when a system
error is detected. The controller may also manage an interlock
system for safety and energy conservation purposes. The controller
may prevent the lamps from operating when the operator may be
exposed to light from the lamps.
[0027] The controller may also be configured to interact with the
operator. The controller preferably includes an input device and a
display screen. A number of operations controlled by the
controller, as described above, may be dependent on the input of
the operator. The controller may prepare a sequence of instructions
based on the type of lens (clear, ultraviolet/visible light
absorbing, photochromic, colored, etc.), prescription, and type of
coatings (e.g., scratch resistant, adhesion promoting, or tint)
inputted by an operator.
[0028] A variety of lens forming compositions may be cured to form
a plastic eyeglass lens in the above described apparatus. Colored
lenses, photochromic lenses, and ultraviolet/visible light
absorbing colorless lenses may be formed. The lens forming
compositions may be formulated such that the conditions for forming
the lens (e.g., curing conditions and post cure conditions) may be
similar without regard to the lens being formed. In an embodiment,
a clear lens may be formed under similar conditions used to form
photochromic lenses by adding a colorless, non-photochromic
ultraviolet/visible light absorbing compound to the lens forming
composition. The curing process for forming a photochromic lens is
such that higher doses of activating light than are typically used
for the formation of a clear, non-ultraviolet/visible light
absorbing lens may be required. In an embodiment,
ultraviolet/visible light absorbing compounds may be added to a
lens forming composition to produce a substantially clear lens
under the more intense dosing requirements used to form
photochromic lenses. The ultraviolet/visible light absorbing
compounds may take the place of the photochromic compounds, making
curing at higher doses possible for clear lenses. An advantage of
adding the ultraviolet/visible light absorbers to the lens forming
composition is that the clear lens formed may offer better
protection against ultraviolet/visible light rays than a clear lens
formed without such compounds.
[0029] An embodiment relates to an improved gasket for engaging a
mold. The gasket is preferably configured to engage a first mold
set for forming a first lens of a first power. The gasket
preferably includes at least four discrete projections for spacing
mold members of a mold set. The projections are preferably arranged
on an interior surface of the gasket. The projections are
preferably evenly spaced around the interior surface of the gasket;
in a preferred embodiment, the spacing between each projection is
about 90 degrees.
[0030] In another embodiment, an improved gasket includes a fill
port for receiving a lens forming composition while fully engaged
to a mold set. The fill port preferably extends from an interior
surface of the gasket to an exterior surface of the gasket.
Consequently, the gasket need not be partially disengaged from a
mold member of a mold set in order to receive a lens forming
composition.
[0031] In another embodiment, a mold/gasket assembly for making
plastic prescription lenses preferably includes a first mold set
for forming a first lens of a first power and a gasket for engaging
the first mold set. The first mold set may contain a front mold
member and a back mold member. The back mold member is also known
as the convex mold member. The back mold member preferably defines
the concave surface of a convex lens. The gasket is preferably
characterized by at least four discrete projections for spacing the
front mold member from the back mold member. A mold cavity for
retaining a lens forming composition is preferably at least
partially defined by the front mold member, the back mold member,
and the gasket. The back mold member preferably has a steep axis
and a flat axis. Each of the projections preferably forms an
oblique angle with the steep and the flat axis of the mold members.
In a preferred embodiment, these angles may each be about 45
degrees. Since the gasket does not include a continuous lip along
its interior surface for spacing mold members, as is conventional
in the art, the gasket may be configured to engage a large variety
of mold sets. For example, the gasket may be configured to engage a
second mold set for forming a second lens of a second power.
[0032] In another embodiment) a mold/gasket assembly for making
plastic prescription lenses includes a mold set for forming a lens
and a gasket configured to engage the mold set. The gasket is
preferably characterized by a fill port for receiving a lens
forming composition while the gasket is fully engaged to the mold.
The fill port preferably extends from an interior surface to an
exterior surface of the gasket. The mold set preferably contains at
least a front mold member and a back mold member. A mold cavity for
retaining a lens forming composition is preferably at least
partially defined by the front mold member, the back mold member,
and the gasket.
[0033] A method for making a plastic eyeglass lens is described.
The method preferably includes engaging a gasket with a first mold
set for forming a first lens of a first power. The first mold set
preferably contains at least a front mold member and a back mold
member. A mold cavity for retaining a lens forming composition may
be at least partially defined by the front mold member, the back
mold member, and the gasket. The gasket is preferably characterized
by at least four discrete projections arranged on an interior
surface thereof for spacing the front and back mold members.
Engaging the gasket with the mold set preferably includes
positioning the back mold members such that each of the projections
forms an oblique angle with the steep and flat axis of the back
mold member. In a preferred embodiment, this angle is about 45
degrees. The method preferably further includes introducing a lens
forming composition into the mold cavity and curing the lens
forming composition.
[0034] An additional embodiment provides a method for making a
plastic eyeglass lens. The method preferably includes engaging a
gasket with a first mold set for forming a first lens of a first
power. The first mold set preferably contains at least a front mold
member and a back mold member. A mold cavity for retaining a lens
forming composition may be at least partially defined by the front
mold member, the back mold member, and the gasket. Preferably, the
method further includes introducing a lens forming composition
through a fill port, wherein the front and back mold members remain
fully engaged with the gasket during the introduction of the lens
forming composition. The lens forming composition may then be
cured.
[0035] In an embodiment, a composition that includes two or more
photochromic compounds may further include a light effector
composition to produce a lens that exhibits an activated color that
differs from an activated color produced by the photochromic
compounds without the light effector composition. The activated
color is defined as the color a lens achieves when exposed to a
photochromic activating light source (e.g., sunlight). A
photochromic activating light source is defined as any light source
that produces light having a wavelength that causes a photochromic
compound to become colored. Photochromic activating light is
defined as light that has a wavelength capable of causing a
photochromic compound to become colored. The photochromic
activating wavelength band is defined as the region of light that
has a wavelength that causes coloring of photochromic compounds.
The light effector composition may include any compound that
exhibits absorbance of at least a portion of the photochromic
activating wavelength band. Light effector compositions may include
photoinitiators, ultraviolet/visible light absorbers, ultraviolet
light stabilizers, and dyes. In this manner, the activated color of
a lens may be altered without altering the ratio and or composition
of the photochromic compounds. By using a light effector
composition, a single lens forming composition may be used as a
base solution to which a light effector may be added in order to
alter the activated color of the formed lens.
[0036] The addition of a light effector composition that absorbs
photochromic activating light may cause a change in the activated
color of the formed lens. The change in activated color may be
dependent on the range of photochromic activating light absorbed by
the light effector composition. The use of different light effector
compositions may allow an operator to produce photochromic lenses
with a wide variety of activated colors (e.g., red, orange, yellow,
green, blue, indigo, violet, gray, or brown).
[0037] In an embodiment, an ophthalmic eyeglass lens may be made
from an activating light curable lens forming composition
comprising a monomer composition and a photoinitiator composition.
The monomer composition preferably includes a polyethylenic
functional monomer. Preferably, the polyethylenic functional
monomer composition includes an aromatic containing polyether
polyethylenic functional monomer. In one embodiment, the
polyethylenic functional monomer is preferably an ethoxylated
bisphenol A di(meth)acrylate.
[0038] The monomer composition may include additional monomers to
modify the properties of the formed eyeglass lens and/or the lens
forming composition. Monomers which may be used in the monomer
composition include polyethylenic functional monomers containing
groups selected from acrylyl or methacrylyl.
[0039] In one embodiment, the photoinitiator composition preferably
includes bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylphenyl)phosphine
oxide, commercially available from Ciba Additives in Tarrytown,
N.Y. under the trade name of Irgacure 819. In another embodiment,
the photoinitiator composition may include a mixture of
photoinitiators. Preferably, a mixture of Irgacure 819 and
1-hydroxycyclohexylphenyl ketone, commercially available from Ciba
Additives under the trade name of Irgacure 184, is used.
[0040] In another embodiment, an ophthalmic eyeglass lens may be
made from an activating light curable lens forming composition
comprising a monomer composition, a photoinitiator composition and
a co-initiator composition. An activating light absorbing compound
may also be present. An activating light absorbing compound is
herein defined as a compound which absorbs at least a portion of
the activating light. The monomer composition preferably includes a
polyethylenic functional monomer. Preferably, the polyethylenic
functional monomer is an aromatic containing polyether
polyethylenic functional monomer. In one embodiment, the
polyethylenic functional monomer is preferably an ethoxylated
bisphenol A di(meth)acrylate.
[0041] The co-initiator composition preferably includes amine
co-initiators. Preferably, acrylyl amines are included in the
co-initiator composition. In one embodiment, the co-initiator
composition preferably includes a mixture of CN-384 and CN-386.
[0042] Examples of activating light absorbing compounds includes
photochromic compounds, UV stabilizers, UV absorbers, and/or
dyes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] The above brief description as well as further objects,
features and advantages of the methods and apparatus of the present
invention will be more fully appreciated by reference to the
following detailed description of presently preferred but
nonetheless illustrative embodiments in accordance with the present
invention when taken in conjunction with the accompanying drawings
in which:
[0044] FIG. 1 depicts a perspective view of a plastic lens forming
apparatus.
[0045] FIG. 2 depicts a perspective view of a spin coating
unit.
[0046] FIG. 3 depicts a cut-away side view of a spin coating
unit.
[0047] FIG. 4 depicts a perspective view of a plastic lens forming
apparatus with a portion of the body removed.
[0048] FIG. 5 depicts a perspective view of the components of a
lens curing unit.
[0049] FIG. 6 depicts a perspective view of a plastic lens forming
apparatus with a portion of the body removed and the coating units
removed.
[0050] FIGS. 7-10 depict various LCD filter patterns.
[0051] FIG. 11 depicts a mold assembly.
[0052] FIG. 12 depicts a post-cure unit.
[0053] FIG. 13 depicts a view of an embodiment of a heat source and
a heat distributor.
[0054] FIG. 14 depicts a view of various embodiments of a heat
source and heat distributors.
[0055] FIG. 15 depicts a view of an embodiment of a heat source and
a heat distributor.
[0056] FIG. 16 depicts a view of an embodiment of two mold members
and a gasket.
[0057] FIG. 17 depicts a plot of the temperature of the lens
forming composition versus time during the application of
activating light pulses.
[0058] FIG. 18 depicts a schematic diagram of a lens curing
apparatus with a light sensor and controller.
[0059] FIG. 19 depicts a view of an embodiment of a system
simultaneously employing both a flash light source and a continuous
activating (e.g., fluorescent) light source.
[0060] FIG. 20 depicts an embodiment of a system simultaneously
employing two flash light sources.
[0061] FIG. 21 depicts an embodiment of a system employing an
activating light controller.
[0062] FIG. 22 depicts a graph illustrating a temperature profile
of a continuous radiation cycle.
[0063] FIG. 23 depicts a graph illustrating temperature profiles
for a continuous irradiation cycle and a pulse irradiation cycle
employed with a mold/gasket set having a 3.00D base curve, and
while applying cooled air at 58.degree. F. to the mold/gasket
set.
[0064] FIG. 24 depicts a chart illustrating qualitative
relationships among curing cycle variables.
[0065] FIG. 25 depicts a graph illustrating temperature profiles
for one curing cycle for a mold/gasket set having a 6.00D base
curve and used with three different light levels.
[0066] FIG. 26 depicts a graph illustrating continuous and pulsed
temperature profiles for a curing cycle employing a mold/gasket set
with a 6.00D base curve.
[0067] FIG. 27 depicts a graph illustrating continuous and pulsed
temperature profiles for a curing cycle employing a mold/gasket set
with a 4.50D base curve.
[0068] FIG. 28 depicts a graph illustrating continuous and pulsed
temperature profiles for a curing cycle employing a mold/gasket set
with a 3.00D base curve.
[0069] FIG. 29 depicts a cross sectional view of a flat-top bifocal
mold.
[0070] FIG. 30 depicts a plot of % transmittance of light versus
wavelength for a photochromic lens.
[0071] FIG. 31 depicts a plot of % transmittance of light versus
wavelength for both a colorless lens containing ultraviolet/visible
light absorbers and a lens containing no ultraviolet/visible light
absorbers.
[0072] FIG. 32 depicts an isometric view of an embodiment of a
gasket.
[0073] FIG. 33 depicts a top view of the gasket of FIG. 1.
[0074] FIG. 34 depicts a cross-sectional view of an embodiment of a
mold/gasket assembly.
[0075] FIG. 35 depicts an isometric view of an embodiment of a
gasket.
[0076] FIG. 36 depicts a top view of the gasket of FIG. 4.
[0077] FIG. 37 depicts a graph showing the absorption ranges of a
variety of photochromic compounds and light effectors.
[0078] FIG. 38 depicts a plastic lens forming apparatus which
includes two lens curing units.
[0079] FIG. 39 depicts chemical structure of acrylated amines.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0080] Apparatus, operating procedures, equipment, systems,
methods, and compositions for lens curing using activating light
are available from Rapid Cast, Inc., Q2100, Inc., and Fast Cast,
Inc. in Louisville, Ky.
[0081] Referring now to FIG. 1, a plastic lens curing apparatus is
generally indicated by reference numeral 10. As shown in FIG. 1,
lens forming apparatus 10 includes at least one coating unit 20, a
lens curing unit 30, a post-cure unit 40, and a controller 50.
Preferably, apparatus 10 includes two coating units 20. Coating
unit 20 is preferably configured to apply a coating layer to a mold
member or a lens. Preferably, coating unit 20 is a spin coating
unit. Lens curing unit 30 includes an activating light source for
producing activating light. As used herein "activating light" means
light that may affect a chemical change. Activating light may
include ultraviolet light (e.g., light having a wavelength between
about 300 nm to about 400 nm), actinic light, visible light or
infrared light. Generally, any wavelength of light capable of
affecting a chemical change may be classified as activating.
Chemical changes may be manifested in a number of forms. A chemical
change may include, but is not limited to, any chemical reaction
that causes a polymerization to take place. Preferably the chemical
change causes the formation of an initiator species within the lens
forming composition, the initiator species being capable of
initiating a chemical polymerization reaction. The activating light
source is preferably configured to direct light toward a mold
assembly. Post-cure unit 40 is preferably configured to complete
the polymerization of plastic lenses. Post-cure unit 40 preferably
includes an activating light source and a heat source. Controller
50 is preferably a programmable logic controller. Controller 50 is
preferably coupled to coating units 20, lens curing unit 30, and
post-cure unit 40, such that the controller is capable of
substantially simultaneously operating the three units 20, 30, and
40. Controller 50 may be a computer.
[0082] A coating unit for applying a coating composition to a lens
or a mold member and then curing the coating composition is
described in U.S. Pat. No. 4,895,102 to Kachel et al., U.S. Pat.
No. 3,494,326 to Upton, and U.S. Pat. No. 5,514,214 to Joel et al.
(all of which are incorporated herein by reference). In addition,
the apparatus shown in FIGS. 2 and 3 may also be used to apply
coatings to lenses or mold members.
[0083] FIG. 2 depicts a pair of spin coating units 102 and 104.
These spin coating units may be used to apply a scratch resistant
coating or a tint coating to a lens or mold member. Each of the
coating units includes an opening through which an operator may
apply lenses and lens mold assemblies to a holder 108. Holder 108
is preferably partially surrounded by barrier 114. Barrier 114 is
preferably coupled to a dish 115. As shown in FIG. 3, the dish
edges may be inclined to form a peripheral sidewall 121 that merges
with barrier 114. The bottom 117 of the dish is preferably
substantially flat. The flat bottom preferably has a circular
opening that allows an elongated member 109 coupled to lens holder
108 to extend through the dish 115.
[0084] Holder 108 is preferably coupled to a motor 112 via
elongated member 109. Motor 112 is preferably configured to cause
rotation of holder 108. In such a case, motor 112 is preferably
configured to cause rotation of elongated member 109, that in turn
causes the rotation of holder 108. The coating unit 102/104, may
also include an electronic controller 140. Electronic controller
140 is preferably coupled to motor 112 to control the rate at which
holder 108 is rotated by motor 112. Electronic controller 140 may
be coupled to a programmable logic controller, such as controller
50, shown in FIG. 1. The programmable logic controller may send
signals to the electronic controller to control the rotational
speed of holder 108. Preferably, motor 112 is configured to rotate
holder 108 at different rates. Motor 112 is preferably capable of
rotating the lens or mold member at a rate of up to 1500
revolutions per minute ("RPM").
[0085] In one embodiment, barrier 114 has an interior surface that
may be made or lined with an absorbent material such as foam
rubber. Preferably, this absorbent material is disposable and
removable. The absorbent material absorbs any liquids that fall off
a lens or mold member during use. Alternatively, the interior
surface of barrier 114 may be substantially non-absorbent, allowing
any liquids used during the coating process to move down barrier
114 into dish 115.
[0086] Coating units 20, are preferably positioned in a top portion
12 of lens forming apparatus 10, as depicted in FIG. 1. A cover 22
is preferably coupled to body 14 of the lens forming apparatus to
allow top portion 12 to be covered during use. A light source 23 is
preferably positioned on an inner surface of cover 22. The light
source includes at least one lamp 24, preferably two or more lamps,
positioned on the inner surface of cover 22. Lamps 24 may be
positioned such that the lamps are oriented above the coating units
20 when cover 22 is closed. Lamps 24 preferably emit activating
light upon the lenses or mold members positioned within coating
units 20. Lamps may have a variety of shapes including, but not
limited to, linear (as depicted in FIG. 1), square, rectangular,
circular, or oval. Activating light sources preferably emit light
having a wavelength that will initiate curing of various coating
materials. For example, most currently used coating materials are
preferably curable by activating light having wavelengths in the
ultraviolet region, therefore the light sources should exhibit
strong ultraviolet light emission. The light sources should,
preferably, produce minimal heat during use. Thus, lamps 24 will
preferably have low heat output. Lamps that exhibit strong
ultraviolet light emission have a peak output at a wavelength in
the ultraviolet light region, between about 200 nm to about 400 nm,
preferably the peak output is between about 200 nm to 300 nm, and
more preferably at about 254 nm. In one embodiment, lamps 24 may be
lamps that have a peak output in the ultraviolet light region, and
have relatively low heat output. Such lights are commonly known as
"germicidal" lights and any such light may be used. A "germicidal"
light emitting light with a peak output in the desired ultraviolet
region is commercially available from Voltarc, Inc. of Fairfield,
Conn. as model UV-WX G10T5.
[0087] An advantage of using a spin coating unit is that lamps of a
variety of shapes may be used (e.g., linear lamps) for the curing
of the coating materials. In one embodiment, a coating material is
preferably cured in a substantially uniform manner to ensure that
the coating is formed uniformly on the mold member or lens. With a
spin coating unit, the object to be coated may be spun at speeds
high enough to ensure that a substantially uniform distribution of
light reaches the object during the curing process, regardless of
the shape of the light source. The use of a spin coating unit
preferably allows the use of commercially available linear light
sources for the curing of coating materials.
[0088] A switch may be incorporated into cover 22. The switch is
preferably electrically coupled to light source 23 such that the
switch must be activated prior to turning the light source on.
Preferably, the switch is positioned such that closing the cover
causes the switch to become activated. In this manner, the lights
will preferably remain off until the cover is closed, thus
preventing inadvertent exposure of an operator to the light from
light source 23.
[0089] During use a lens or lens mold assembly may be placed on the
lens holder 108. The lens holder 108 may include a suction cup
connected to a metal bar. The concave surface of the suction cup
may be attachable to a face of a mold or lens, and the convex
surface of the suction cup may be attached to a metal bar. The
metal bar may be coupled to motor 112. The lens holder may also
include movable arms and a spring assembly that may be together
operable to hold a lens against the lens holder with spring tension
during use.
[0090] As shown in FIG. 4, the curing unit 30 may include an upper
light source 214, a lens drawer assembly 216, and a lower light
source 218. Lens drawer assembly 216 preferably includes a mold
assembly holder 220, more preferably at least two mold assembly
holders 220. Each of the mold assembly holders 220 is preferably
configured to hold a pair of mold members that together with a
gasket form a mold assembly. The lens drawer assembly 216 is
preferably slidingly mounted on a guide. During use, mold
assemblies may be placed in the mold assembly holders 220 while the
lens drawer assembly is in the open position (i.e., when the door
extends from the front of the lens curing unit). After the mold
assemblies have been loaded into the mold holder 220 the door may
be slid into a closed position, with the mold assemblies directly
under the upper light source 214 and above the lower light source
218. Vents (not shown) may be placed in communication with the lens
curing unit to allow a stream of air to be directed toward the mold
members when the mold members are positioned beneath the upper
lamps. An exhaust fan (not shown) may communicate with the vents to
improve the circulation of air flowing through the lens curing
unit.
[0091] As shown in FIGS. 4 and 5, it is preferred that the upper
light source 214 and lower light source 216 include a plurality of
activating light generating devices or lamps 240. Preferably, the
lamps are oriented proximate each other to form a row of lights, as
depicted in FIG. 4. Preferably, three or four lamps are positioned
to provide substantially uniform radiation over the entire surface
of the mold assembly to be cured. The lamps 240, preferably
generate activating light. Lamps 240 may be supported by and
electrically connected to suitable fixtures 242. Lamps 240 may
generate either ultraviolet light, actinic light, visible light,
and/or infrared light. The choice of lamps is preferably based on
the monomers used in the lens forming composition. In one
embodiment, the activating light may be generated from a
fluorescent lamp. The fluorescent lamp preferably has a strong
emission spectra in the 380 to 490 nm region. A fluorescent lamp
emitting activating light with the described wavelengths is
commercially available from Philips as model TLD-15W/03. In another
embodiment, the lamps may be ultraviolet lights.
[0092] In one embodiment, the activating light sources may be
turned on and off quickly between exposures. Flasher ballasts 250,
depicted in FIG. 6, may be used for this function. The flasher
ballast may be positioned beneath the coating unit. A flasher
ballast 250 may operate in a standby mode wherein a low current is
supplied to the lamp filaments to keep the filaments warm and
thereby reduce the strike time of the lamp. Such a ballast is
commercially available from Magnatek, Inc of Bridgeport, Conn.
Power supply 252 may also be located proximate the flasher
ballasts, underneath the coating unit.
[0093] FIG. 18 schematically depicts a light control system. The
light sources 214 in lens curing unit 30 apply light towards the
mold assembly 352. A light sensor 700 may be located adjacent the
light sources 214. Preferably, the light sensor 700 is a
photoresistor light sensor (photodiodes or other light sensors may
also be usable in this application). The light sensor 700 with a
filter 750 may be connected to lamp driver 702 via wires 704. Lamp
driver 702 sends a current through the light sensor 700 and
receives a return signal from the light sensor 700. The return
signal may be compared against an adjustable set point, and then
the electrical frequency sent to the light sources 214 via wires
706 may be varied depending on the differences between the set
point and the signal received from the light sensor 700.
Preferably, the light output is maintained within about +/-1.0
percent.
[0094] One "lamp driver" or light controller is a Mercron Model
FX0696-4 and Model FX06120-6 (Mercron, Inc., Dallas, Tex., U.S.A.).
These light controllers are described in U.S. Pat. Nos. 4,717,863
and 4,937,470.
[0095] In an embodiment, a flash lamp emits activating light pulses
to cure the lens forming material. It is believed that a flash lamp
would provide a smaller, cooler, less expensive, and more reliable
light source than other sources. The power supply for a flash lamp
tends to draw relatively minimal current while charging its
capacitor bank. The flash lamp discharges the stored energy on a
microsecond scale to produce very high peak intensities from the
flash tube itself. Thus flash lamps tend to require less power for
operation and generate less heat than other light sources used for
activating light curing. A flash lamp may also be used to cure a
lens coating.
[0096] In an embodiment, the flash lamp used to direct activating
light toward at least one of the mold members is a xenon light
source. The lens coating may also be cured using a xenon light
source. Referring to FIG. 21, xenon light source 980 preferably
contains photostrobe 992 having a tube 996 and electrodes to allow
the transmission of activating light. The tube may include
borosilicate glass or quartz. A quartz tube will generally
withstand about 3 to 10 times more power than a hard glass tube.
The tube may be in the shape of a ring, U, helix, or it may be
linear. The tube may include capacitive trigger electrode 995. The
capacitive trigger electrode may include a wire, silver strip, or
conductive coating located on the exterior of tube 996. The xenon
light source is preferably adapted to deliver pulses of light for a
duration of less than about 1 second, more preferably between about
{fraction (1/10)} of a second and about {fraction (1/1000)} of a
second, and more preferably still between about {fraction (1/400)}
of a second and {fraction (1/600)} of a second. The xenon source
may be adapted to deliver light pulses about every 4 seconds or
less. The relatively high intensity of the xenon lamp and short
pulse duration may allow rapid curing of the lens forming
composition without imparting significant radiative heat to the
composition.
[0097] In an embodiment, controller 990 (shown in FIG. 21) controls
the intensity and duration of activating light pulses delivered
from activating light source 980 and the time interval between
pulses, shown in FIG. 19. Activating light source 980 may include
capacitor 994, that stores the energy required to deliver the
pulses of activating light. Capacitor 994 may be adapted to allow
pulses of activating light to be delivered as frequently as
desired. Temperature monitor 997 may be located at a number of
positions within mold chamber 984. The temperature monitor may
measure the temperature within the chamber and/or the temperature
of air exiting the chamber. The system may be configured to send a
signal to cooler 988 and/or distributor 986 (shown in FIG. 19) to
vary the amount and/or temperature of the cooling air. The
temperature monitor may also determine the temperature at any of a
number of locations proximate the mold cavity and send a signal to
controller 990 to vary the pulse duration, pulse intensity, or time
between pulses as a function of a temperature within mold chamber
984.
[0098] In an embodiment, light sensor 999 may be used to determine
the intensity of activating light emanating from source 980. The
light sensor is preferably configured to send a signal to
controller 990, that is preferably configured to maintain the
intensity of the activating light at a selected level. Filter 998
may be positioned between activating light source 980 and light
sensor 999 and is preferably configured to inhibit non-activating
light rays from contacting light sensor 999, while allowing
activating rays to contact the sensor. In one embodiment, the
filter may include 365N glass or any other material adapted to
filter non-activating light (e.g., visible light) and transmit
activating light.
[0099] In an embodiment, more than one activating light source may
be used to simultaneously apply activating pulses to the lens
forming composition. Such an embodiment is shown in FIG. 20.
Activating light sources 980a and 980b may be positioned around
mold chamber 985 so that pulses may be directed toward the front
face of a lens and the back face of a lens substantially
simultaneously. Mold chamber 985 is preferably adapted to hold a
mold in a vertical position such that pulses from activating light
source 980a may be applied to the face of a first mold member,
while pulses from activating light source 980b may be applied to
the face of a second mold member. In an embodiment, activating
light source 980b applies activating light pulses to a back surface
of a lens more frequently than xenon source 980a applies activating
light pulses to a front surface of a lens. Activating light sources
980a and 980b may be configured such that one source applies light
to mold chamber 984 from a position above the chamber while the
other activating light source applies light to the mold chamber
from a position below the chamber.
[0100] In an embodiment, a xenon light source and a relatively low
intensity (e.g., fluorescent) light source may be used to
simultaneously apply activating light to a mold chamber. As
illustrated in FIG. 19, xenon source 980 may apply activating light
to one side of mold chamber 984 while low intensity fluorescent
source 982 applies activating light to another side of the mold
chamber. Fluorescent source 982 may include a compact fluorescent
"light bucket" or a diffused fluorescent lamp. The fluorescent
light source may deliver continuous or substantially pulsed
activating light as the xenon source delivers activating Light
pulses. The fluorescent source may deliver continuous activating
light rays having a relatively low intensity of less than about 100
microwatts/cm.sup.2.
[0101] In one embodiment, an upper light filter 254 may be
positioned between upper light source 214 and lens drawer assembly
216, as depicted in FIG. 5. A lower light filter 256 may be
positioned between lower light source 218 and lens drawer assembly
216. The upper light filter 254 and lower light filter 256 are
shown in FIG. 5 as being made of a single filter member, however,
those of ordinary skill in the art will recognize that each of the
filters may include two or more filter members. The components of
upper light filter 254 and lower light filter 256 are preferably
modified depending upon the characteristics of the lens to be
molded. For instance, in an embodiment for making negative lenses,
the upper light filter 254 includes a plate of Pyrex glass that may
be frosted on both sides resting upon a plate of clear Pyrex glass.
The lower light filter 256 includes a plate of Pyrex glass, frosted
on one side, resting upon a plate of clear Pyrex glass with a
device for reducing the intensity of activating light incident upon
the center portion relative to the edge portion of the mold
assembly.
[0102] Conversely, in a preferred arrangement for producing
positive lenses, the upper light filter 254 includes a plate of
Pyrex glass frosted on one or both sides and a plate of clear Pyrex
glass resting upon the plate of frosted Pyrex glass with a device
for reducing the intensity of activating light incident upon the
edge portion in relation to the center portion of the mold
assembly. The lower light filter 256 includes a plate of clear
Pyrex glass frosted on one side resting upon a plate of clear Pyrex
glass with a device for reducing the intensity of activating light
incident upon the edge portion in relation to the center portion of
the mold assembly. In this arrangement, in place of a device for
reducing the relative intensity of activating light incident upon
the edge portion of the lens, the diameter of the aperture 250 may
be reduced to achieve the same result, i.e., to reduce the relative
intensity of activating light incident upon the edge portion of the
mold assembly.
[0103] It should be apparent to those skilled in the art that each
filter 254 or 256 could be composed of a plurality of filter
members or include any other means or device effective to reduce
the light to its desired intensity, to diffuse the light and/or to
create a light intensity gradient across the mold assemblies.
Alternately, in certain embodiments no filter elements may be
used.
[0104] In one embodiment, upper light filter 254 or lower light
filter 256 each include at least one plate of Pyrex glass having at
least one frosted surface. Also, either or both of the filters may
include more than one plate of Pyrex glass each frosted on one or
both surfaces, and/or one or more sheets of tracing paper. After
passing through frosted Pyrex glass, the activating light is
believed to have no sharp intensity discontinuities. By removing
the sharp intensity distributions a reduction in optical
distortions in the finished lens may be achieved. Those of ordinary
skill in the art will recognize that other means may be used to
diffuse the activating light so that it has no sharp intensity
discontinuities.
[0105] In another embodiment, upper light filter 254 and lower
light filter 256 may be liquid crystal display ("LCD") panels.
Preferably, the LCD panel is a monochrome trans-flective panel with
the back light and reflector removed. A monochrome trans-flective
LCD panel is manufactured by Sharp Corporation and may be purchased
from Earth Computer Products. The LCD panels are preferably
positioned such that light from the light sources passes through
the LCD panels to the lens drawer assembly 216. The intensity of
the light is preferably reduced as the light passes through the LCD
panel. The LCD panel is preferably programmable such that the light
transmissibility of the LCD panel may be altered. In use, a
predetermined pattern of light and dark regions may be displayed on
the LCD panel. As light from the light sources hits these regions
the light may be transmitted through the light regions with a
higher intensity than through the darker regions. In this manner,
the pattern of light and dark areas on the LCD panel may be
manipulated such that light having the optimal curing intensity
pattern hits the mold assemblies. Although the LCD panel is not
entirely opaque in its blackened out state, it may still reduce the
intensity of light reaching the mold assemblies. Typically, the
light transmission ratio between the lightest and darkest regions
of the LCD panel is about 4 to 1.
[0106] The use of an LCD panel as a light filter offers a number of
advantages over the conventional filter systems described earlier.
One advantage is that the filter pattern may be changed actively
during a curing cycle. For example, the pattern of light and dark
regions may be manipulated such that a lens is initially cured from
the center of the lens then the curing may be gradually expanded to
the outer edges of the lens. This type of curing pattern may allow
a more uniformly cured lens to be formed. In some instances, curing
in this manner may also be used to alter the final power of the
formed lens.
[0107] Another advantage is that the LCD panel may be used as a
partial shutter to reduce the intensity of light reaching the mold
assembly. By blackening the entire LCD panel the amount of light
reaching any portion of the mold assembly may be reduced. In this
manner, the LCD may be used to create "pulses" of light by
alternating between a transmissive and darkened mode. By having the
LCD panel create these light "pulses" a flash ballast or similar
pulse generating equipment may be unnecessary. Thus, the light
sources may remain on during the entire curing cycle, with the LCD
panel creating the curing light pulses. This may also increase the
lifetime of the lamps, since the rapid cycling of lamps tends to
reduce the lamps' lifetime.
[0108] In another embodiment, an LCD panel may be used to allow
different patterns and/or intensities of light to reach two
separate mold assemblies. As depicted in FIG. 4, the lens curing
unit may be configured to substantially simultaneously irradiate
two mold assemblies. If the mold assemblies are being used to
create lenses having the same power the light irradiation pattern
and/or intensity may be substantially the same for each mold
assembly. If the mold assemblies are being used to create lenses
having significantly different powers, each mold assembly may
require a significantly different light irradiation pattern and/or
intensity. The use of an LCD filter may allow the irradiation of
each of the mold assemblies to be controlled individually. For
example, a first mold assembly may require a pulsed curing scheme,
while the other mold assembly may require a continuous irradiation
pattern through a patterned filter. The use of an LCD panel may
allow such lenses to be formed substantially simultaneously. A
first portion of the LCD panel between the light source and the
first molding apparatus may be alternatively switched between a
darkened and an undarkened state. While a first portion is used to
create pulses of activating light, another portion of the LCD panel
may be formed into the specific pattern required for the continuous
curing of the other lens.
[0109] When non-LCD type filters are used it may be necessary to
maintain a library of filters for use in the production of
different types of prescription lenses. Typically, each individual
prescription will need a particular filter pattern to obtain a high
quality lens. Since an LCD panel may be programmed into a variety
of patterns, it may be possible to rely on a single LCD panel,
rather than a library of filters. The LCD panel may be programmed
to fit the needs of the specific type of lens being formed. Such a
system also minimizes the need for human intervention, since a
controller may be programmed for a desired pattern, rather than the
operator having to choose among a "library" of filters.
[0110] The control of the temperature of an LCD panel filter during
a curing cycle may be important for achieving a proper lens. In
general as the temperature of a panel is increased the lighter
regions of the panel may become darker (i.e., less light
transmissive). Thus, it may be necessary to control the temperature
of the LCD panel during curing to ensure that light having the
appropriate intensity reaches the mold assemblies. A cooling system
or heating system may therefore, be coupled to the LCD panel to
ensure proper temperature control. In one embodiment, it is
preferred that a substantially transparent heater is attached to
the LCD panel. By increasing the temperature of the LCD panel the
light transmissibility of the panel may be decreased. It is
preferred that an LCD panel be maintained above room temperature
since at room temperature the panel may be too light to
sufficiently inhibit the light from reaching the mold assemblies.
In order to obtain a proper pattern of light and dark regions when
the LCD panel is heated it may be necessary to adjust the contrast
of the panel. This adjustment may be done either manually or
electronically.
[0111] The LCD panel filters may be coupled to a programmable logic
device that may be used to design and store patterns for use during
curing. FIGS. 7-10 show a number of patterns which may be generated
on an LCD panel and used to filter activating light. Each of these
patterns is preferably used for the production of a lens having a
specific prescription power.
[0112] As shown in FIG. 11, the mold assembly 352 may include
opposed mold members 378, separated by an annular gasket 380 to
define a lens molding cavity 382. The opposed mold members 378 and
the annular gasket 380 may be shaped and selected in a manner to
produce a lens having a desired diopter.
[0113] The mold members 378 may be formed of any suitable material
that will permit the passage of activating light. The mold members
378 are preferably formed of glass. Each mold member 378 has an
outer peripheral surface 384 and a pair of opposed surfaces 386 and
388 with the surfaces 386 and 388 being precision ground.
Preferably the mold members 378 have desirable activating light
transmission characteristics and both the casting surface 386 and
non-casting surface 388 preferably have no surface aberrations,
waves, scratches or other defects as these may be reproduced in the
finished lens.
[0114] As noted above, the mold members 378 are preferably adapted
to be held in spaced apart relation to define a lens molding cavity
382 between the facing surfaces 386 thereof The mold members 378
are preferably held in a spaced apart relation by a T-shaped
flexible annular gasket 380 that seals the lens molding cavity 382
from the exterior of the mold members 378. In use, the gasket 380
may be supported on a portion of the mold assembly holder 220
(shown in FIG. 4).
[0115] In this manner, the upper or back mold member 390 has a
convex inner surface 386 while the lower or front mold member 392
has a concave inner surface 386 so that the resulting lens molding
cavity 382 is preferably shaped to form a lens with a desired
configuration. Thus, by selecting the mold members 378 with a
desired surface 386, lenses with different characteristics, such as
focal lengths, may be produced.
[0116] Rays of activating light emanating from lamps 240 preferably
pass through the mold members 378 and act on a lens forming
material disposed in the mold cavity 382 in a manner discussed
below so as to form a lens. As noted above, the rays of activating
light may pass through a suitable filter 254 or 256 before
impinging upon the mold assembly 352.
[0117] The mold members 378, preferably, are formed from a material
that will not transmit activating light having a wavelength below
approximately 300 nm. Suitable materials are Schott Crown, S-1 or
S-3 glass manufactured and sold by Schott Optical Glass Inc., of
Duryea, Pa. or Corning 8092 glass sold by Corning Glass of Corning,
N.Y. A source of flat-top or single vision molds may be Augen Lens
Co. in San Diego, Calif.
[0118] The annular gasket 380 may be formed of vinyl material that
exhibits good lip finish and maintains sufficient flexibility at
conditions throughout the lens curing process. In an embodiment,
the annular gasket 380 is formed of silicone rubber material. such
as GE SE6035 which is commercially available from General Electric.
In another preferred embodiment, the annular gasket 380 is formed
of copolymers of ethylene and vinyl acetate which are commercially
available from E. I. DuPont de Nemours & Co. under the trade
name ELVAX7. Preferred ELVAX7 resins are ELVAX7 350 having a melt
index of 17.3-20.9 dg/min and a vinyl acetate content of 24.3-25.7
wt. %, ELVAX7 250 having a melt index of 22.0-28.0 dg/min and a
vinyl acetate content of 27.2-28.8 wt. %, ELVAX7 240 having a melt
index of 38.0-48.0 dg/min and a vinyl acetate content of 27.2-28.8
wt. %, and ELVAX7 150 having a melt index of 38.0-48.0 dg/min and a
vinyl acetate content of 32.0-34.0 wt. %. In another embodiment,
the gasket may be made from polyethylene. Regardless of the
particular material, the gaskets 80 may be prepared by conventional
injection molding or compression molding techniques which are
well-known by those of ordinary skill in the art.
[0119] In another embodiment, FIGS. 32 and 33 present an isometric
view and a top view, respectively, of a gasket 510. Gasket 510 may
be annular, and is preferably configured to engage a mold set for
forming a mold assembly. Gasket 510 is preferably characterized by
at least four discrete projections 511. Gasket 510 preferably has
an exterior surface 514 and an interior surface 512. The
projections 511 are preferably arranged upon inner surface 512 such
that they are substantially coplanar. The projections are
preferably evenly spaced around the interior surface of the gasket
Preferably, the spacing along the interior surface of the gasket
between each projection is about 90 degrees. Although four
projections are preferred, it is envisioned that more than four
could be incorporated. The gasket 510 may be formed of a silicone
rubber material such as GE SE6035 which is commercially available
from General Electric. In another embodiment, the gasket 510 may be
formed of copolymers of ethylene and vinyl acetate which are
commercially available from E. I. DuPont de Nemours & Co. under
the trade name ELVAX7. In another embodiment, the gasket 510 may be
formed from polyethylene.
[0120] As shown in FIG. 34, projections 511 are preferably capable
of spacing mold members 526 of a mold set. Mold members 526 may be
any of the various types and sizes of mold members that are well
known in the art. A mold cavity 528 at least partially defined by
mold members 526 and gasket 510, is preferably capable of retaining
a lens forming composition. Preferably, the seal between gasket 510
and mold members 526 is as complete as possible. The height of each
projection 511 preferably controls the spacing between mold members
526, and thus the thickness of the finished lens. By selecting
proper gaskets and mold sets, lens cavities may be created to
produce lenses of various powers.
[0121] A mold assembly consists of two mold members. A front mold
member 526a and a back mold member 526b, as depicted in FIG. 34.
The back mold member is also known as the convex mold member. The
back mold member preferably defines the concave surface of a convex
lens. Referring back to FIGS. 32 and 33, locations where the steep
axis 522 and the flat axis 524 of the back mold member 526b
preferably lie in relation to gasket 510 have been indicated. In
conventional gaskets, a raised lip may be used to space mold
members. The thickness of this lip varies over the circumference of
the lip in a manner appropriate with the type of mold set a
particular gasket is designed to be used with. In order to have the
flexibility to use a certain number of molds, an equivalent amount
of conventional gaskets is typically kept in stock.
[0122] However, within a class of mold sets there may be points
along the outer curvature of a the back mold member where each
member of a class of back mold members is shaped similarly. These
points may be found at locations along gasket 510, oblique to the
steep and flat axes of the mold members. In a preferred embodiment,
these points are at about 45 degree angles to the steep and flat
axes of the mold members. By using discrete projections 511 to
space the mold members at these points, an individual gasket could
be used with a variety of mold sets. Therefore, the number of
gaskets that would have to be kept in stock may be greatly
reduced.
[0123] In addition, gasket 510 may include a recession 518 for
receiving a lens forming composition. Lip 520 may be pulled back in
order to allow a lens forming composition to be introduced into the
cavity. Vent ports 516 may be incorporated to facilitate the escape
of air from the mold cavity as a lens forming composition is
introduced.
[0124] A method for making a plastic eyeglass lenses using gasket
510 is presented. The method preferably includes engaging gasket
510 with a first mold set for forming a first lens of a first
power. The first mold set preferably contains at least a front mold
member 526a and a back mold member 526b. A mold cavity for
retaining a lens forming composition may be at least partially
defined by mold members 526a and 526b and gasket 510. Gasket 510 is
preferably characterized by at least four discrete projections 511
arranged on interior surface 512 for spacing the mold members.
Engaging gasket 510 with the mold set preferably includes
positioning the mold members such that each of the projections 511
forms an oblique angle with the steep and flat axis of the back
mold member 526b. In a preferred embodiment, this angle is about 45
degrees. The method preferably further includes introducing a lens
forming composition into mold cavity 528 and curing the lens
forming composition. Curing may include exposing the composition to
activating light and/or thermal radiation. After the lens is cured,
the first mold set may be removed from the gasket and the gasket
may then be engaged with a second mold set for forming a second
lens of a second power.
[0125] FIGS. 35 and 36 present an isometric view and a top view,
respectively, of an improved gasket. Gasket 530 may be composed of
similar materials as gasket 510. Like gasket 510, gasket 530 is
preferably annular, but may be take a variety of shapes. In
addition, gasket 530 may incorporate projections 531 in a manner
similar to the projections 511 shown in FIG. 32. Alternatively,
gasket 530 may include a raised lip along interior surface 532 or
another method of spacing mold members that is conventional in the
art.
[0126] Gasket 530 preferably includes a fill port 538 for receiving
a lens forming composition while gasket 530 is fully engaged to a
mold set. Fill port 538 preferably extends from interior surface
532 of gasket 530 to an exterior surface 534 of gasket 530.
Consequently, gasket 530 need not be partially disengaged from a
mold member of a mold set in order to receive a lens forming
composition. In order to introduce a lens forming composition into
the mold cavity defined by a conventional mold/gasket assembly the
gasket must be at least partially disengaged from the mold members.
During the process of filling the mold cavity, lens forming
composition may drip onto the backside of a mold member. Lens
forming composition on the backside of a mold member may cause
activating light used to cure the lens to become locally focused,
and may cause optical distortions in the final product. Because
fill port 538 allows lens forming composition to be introduced into
a mold cavity while gasket 530 is fully engaged to a mold set,
gasket 530 preferably avoids this problem. In addition, fill port
538 may be of sufficient size to allow air to escape during the
introduction of a lens forming composition into a mold cavity;
however, gasket 530 may also incorporate vent ports 536 to
facilitate the escape of air.
[0127] A method for making a plastic eyeglass lens using gasket 530
preferably includes engaging gasket 530 with a first mold set for
forming a first lens of a first power. The first mold set
preferably contains at least a front mold member and a back mold
member. A mold cavity for retaining a lens forming composition may
be at least partially defined by the front mold member, the back
mold member, and the gasket. Preferably, the method further
includes introducing a lens forming composition through fill port
538, wherein the first and second mold members remain fully engaged
with the gasket during the introduction of the lens forming
composition. The lens forming composition may then be cured by use
of activating light and/or thermal radiation.
[0128] In operation, the apparatus may be appropriately configured
for the production of positive lenses which are relatively thick at
the center or negative lenses which are relatively thick at the
edge. To reduce the likelihood of premature release, the relatively
thick portions of a lens are preferably polymerized at a faster
rate than the relatively thin portions of a lens.
[0129] The rate of polymerization taking place at various portions
of a lens may be controlled by varying the relative intensity of
activating light incident upon particular portions of a lens. The
rate of polymerization taking place at various portions of a lens
may also be controlled by directing air across the mold members 378
to cool the mold assembly 352.
[0130] For positive lenses, the intensity of incident activating
light is preferably reduced at the edge portion of the lens so that
the thicker center portion of the lens polymerizes faster than the
thinner edge portion of the lens. Conversely, for a negative lens,
the intensity of incident activating light is preferably reduced at
the center portion of the lens so that the thicker edge portion of
the lens polymerizes faster than the thinner center portion of the
lens. For either a positive lens or a negative lens, air may be
directed across the faces of the mold members 378 to cool the mold
assembly 352. As the overall intensity of incident activating light
is increased, more cooling is needed which may be accomplished by
either or both of increasing the velocity of the air and reducing
the temperature of the air.
[0131] It is well known by those of ordinary skill in the art that
lens forming materials tend to shrink as they cure. If the
relatively thin portion of a lens is allowed to polymerize before
the relatively thick portion, the relatively thin portion will tend
to be rigid at the time the relatively thick portion cures and
shrinks and the lens will either release prematurely from or crack
the mold members. Accordingly, when the relative intensity of
activating light incident upon the edge portion of a positive lens
is reduced relative to the center portion, the center portion may
polymerize faster and shrink before the edge portion is rigid so
that the shrinkage is more uniform. Conversely, when the relative
intensity of activating light incident upon the center portion of a
negative lens is reduced relative to the edge portion, the edge
portion may polymerize faster and shrink before the center becomes
rigid so that the shrinkage is more uniform.
[0132] The variation of the relative intensity of activating light
incident upon a lens may be accomplished in a variety of ways.
According to one method, in the case of a positive lens, a ring of
opaque material may be placed between the lamps and the mold
assembly so that the incident activating light falls mainly on the
thicker center portion of the lens. Alternatively, when an LCD
panel is used as the filter, the panel may be programmed to form a
pattern so that the incident activating light falls mainly on the
thicker center portion of the lens (See FIG. 7, patterns A, B, C,
D, F, H, and I). Conversely, for a negative lens, a disk of opaque
material may be placed between the lamps 240 and the mold assembly
352 so that the incident activating light falls mainly on the edge
portion of the lens. Alternatively, when an LCD panel is used as
the filter, the panel may be programmed to form a pattern so that
the incident activating light falls mainly on the thicker edge
portion of the lens (See FIG. 9, patterns C, F, I, and FIG. 10,
patterns A, B, D, E, G, and H).
[0133] According to another method, in the case of a negative lens,
a sheet material or an LCD panel having a pattern with a variable
degree of opacity ranging from opaque at a central portion to
transparent at a radial outer portion may be disposed between the
lamps 240 and the mold assembly 352. Conversely, for a positive
lens, a sheet material or LCD panel having a pattern with a
variable degree of opacity ranging from transparent at a central
portion to opaque at a radial outer portion may be disposed between
the lamps 240 and the mold assembly 352.
[0134] As noted above, the mold assembly 352 may be cooled during
curing of the lens forming material as the overall intensity of the
incident activating light is increased. Cooling of the mold
assembly 352 generally reduces the likelihood of premature release
by slowing the reaction and improving adhesion. There may also be
improvements in the optical quality, stress characteristics and
impact resistance of the lens. Cooling of the mold assembly 352 is
preferably accomplished by blowing air across the mold assembly
352. The air preferably has a temperature ranging between 15 and
85.degree. F. (about -9.4.degree. C. to 29.4.degree. C.) to allow
for a curing time of between 30 and 10 minutes. The air
distribution devices have been found to be particularly
advantageous as they may be specifically designed to direct air
directly across the surface of the opposed mold members 378. After
passing across the surface of the opposed mold members 378, the air
emanating from the air distribution devices may be vented out of
the system. Alternately the air emanating from the air distribution
devices may be recycled back to an air cooler. In another
embodiment, the mold assembly 352 may also be cooled by disposing
the mold assembly in a liquid cooling bath.
[0135] The opposed mold members 378 are preferably thoroughly
cleaned between each curing run as any dirt or other impurity on
the mold members 378 may cause premature release. The mold members
378 may be cleaned by any conventional means well known to those of
ordinary skill in the art such as with a domestic cleaning product,
i.e., Mr. Clean.TM. available from Proctor and Gamble. Those of
ordinary skill in the art will recognize, however, that many other
techniques may also be used for cleaning the mold members 378.
[0136] After curing of the lens in lens curing unit 30, the lens
may be de-molded and post-cured in the post-cure unit 40. Post-cure
unit 40 is preferably configured to apply light, heat or a
combination of light and heat to the lens. As shown in FIG. 12,
post-cure unit 40 may include a light source 414, a lens drawer
assembly 416, and a heat source 418. Lens drawer assembly 416
preferably includes a lens holder 420, more preferably at least two
lens holders 420. Lens drawer assembly 416 is preferably slidingly
mounted on a guide. Preferably, lens drawer assembly 416 is made
from a ceramic material. Cured lenses may be placed in lens holders
420 while the lens drawer assembly 416 is in the open position
(i.e., when the door extends from the front of post-cure unit 40).
After the lenses have been loaded into lens holders 420 the door
may be slid into a closed position, with the lenses directly under
light source 414 and above heat source 418.
[0137] As shown in FIG. 12, it is preferred that the light source
414 includes a plurality of light generating devices or lamps 440.
Preferably, lamps 440 may be oriented above each of the lens
holders when the lens drawer assembly is closed. The lamps 440,
preferably, generate activating light. The lamps 440 may be
supported by and electrically connected to suitable fixtures 442.
The fixtures may be at least partially reflective and concave in
shape to direct light from the lamps 440 toward the lens holders.
The lamps may generate either ultraviolet light, actinic light,
visible light, and/or infrared light. The choice of lamps is
preferably based on the monomers used in the lens forming
composition. In one embodiment, the activating light may be
generated from a fluorescent lamp. The fluorescent lamp preferably
has a strong emission spectra from about 200 nm to about 800 nm,
more preferably between about 200 nm to about 400 nm. A fluorescent
lamp emitting activating light with the described wavelengths is
commercially available from Phillips as model PL-S 9W/10. In
another embodiment, the lamp may generate ultraviolet light.
[0138] In one embodiment, the activating light source may be turned
on and off quickly between exposures. A flasher ballast may be used
for this function. The flasher ballast may be positioned beneath
the post-cure unit. A flasher ballast may operate in a standby mode
wherein a low current is preferably supplied to the lamp filaments
to keep the filaments warm and thereby reduce the strike time of
the lamp. Such a ballast is commercially available from Magnatek,
Inc of Bridgeport, Conn.
[0139] Heat source 418 may be configured to heat the interior of
the post-cure unit. Preferably, heat source 418 is a resistive
heater. Heat source 418 may be made up of one or two resistive
heaters. The temperature of heat source 418 may be thermostatically
controlled. By heating the interior of the post-cure unit the
lenses which are placed in post-cure unit 40 may be heated to
complete curing of the lens forming material. Post-cure unit 40 may
also include a fan to circulate air within the unit. The
circulation of air within the unit may help maintain a relatively
uniform temperature within the unit. The fan may also be used to
cool the temperature of post-cure unit 40 after completion of the
post cure process.
[0140] In an embodiment, described as follows, a lens cured by
exposure to activating light may be further processed by conductive
heating. Such conductive heating tends to enhance the degree of
cross-linking in the lens and to increase the tintability of the
lens. A lens forming material is preferably placed in mold cavity
900 (illustrated in FIG. 16), which is defined by at least first
mold member 902 and second mold member 904. Activating light is
directed toward at least one of the mold members, thereby curing
the lens forming material to a lens. Heat distributor 910 (shown in
FIG. 13) may be adapted to distribute conductive heat from
conductive heat source 418 to at least one mold member. Heat
distributor 910 is preferably flexible such that at least a portion
of it may be shaped to substantially conform to the shape of face
906 or face 907 of first mold member 902 or second mold member 904,
respectively. Heat distributor 910 is preferably placed in contact
with conductive heat source 418, and mold member 902 is preferably
placed on heat distributor 910 such that face 906 of the mold
member rests on top of the heat distributor 910 Heat distributor
910 may be coupled to heat source 418. Heat is preferably
conductively applied to the heat distributor 910 by the heat source
418. Heat is preferably conducted from the heat distributor 910
through the mold member to a face of the lens. The heat distributor
may be shaped to accommodate face 906 of first mold member 902 or
face 907 of second mold member 904 such that the heat is applied to
front face 916 or back face 915 of the lens. The temperature of
heat source 418 may be thermostatically controlled.
[0141] In an embodiment, a resistive heater 418 (shown in FIG. 17)
may be used as a heat source to provide conductive heat to the
lens. A number of other heat sources may be used. In an embodiment,
heat distributor 910 may include countershape 920. Countershape 920
may be placed on top of the hot plate to distribute conductive heat
from the hot plate. The countershape is preferably flexible such
that at least a portion of it may substantially conform to the
shape of an outside face of a mold member. The countershape may be
hemispherical and either convex or concave depending upon whether
the surface of the mold assembly to be placed upon it is convex or
concave. For example, when the concave surface of the back mold is
utilized to conduct heat into the lens assembly, a convex
countershape is preferably provided to rest the assembly on.
[0142] Countershape 920 may include a glass mold, a metal optical
lap, a pile of hot salt and/or sand, or any of a number of other
devices adapted to conduct heat from heat source 912. It should be
understood that FIG. 17 includes combinations of a number of
embodiments for illustrative purposes. Any number of identical or
distinct counter-shapes may be used in combination on top of a heat
source. In an embodiment, a countershape includes a container 922
filled with particles 924. The particles preferably include metal
or ceramic material. Countershape 920 may include heat distributor
910. A layer 914 of material may be placed over the countershape
920 or heat distributor 910 to provide slow, smooth, uniform heat
conduction into the lens mold assembly. This layer preferably has a
relatively low heat conductivity and may be made of rubber, cloth,
Nomex.TM. fabric or any other suitable material that provides slow,
smooth, uniform conduction.
[0143] In an embodiment, countershape 920 includes layer 914 (e.g.,
a bag or container) filled with particles 924 such that the
countershape may be conveniently shaped to conform to the shape of
face 906 or face 907. In an embodiment, the countershape is
preferably a "beanbag" that contains particles 924 and may be
conformable to the shape of a mold face placed on top of it.
Particles 924 may include ceramic material, metal material, glass
beads, sand and/or salt. The particles preferably facilitate
conductive heat to be applied to face 906 or face 907 substantially
evenly.
[0144] In an embodiment, the countershape 920 is preferably placed
on top of heat source 41S. Countershape 920 is preferably heated
until the temperature of the countershape is substantially near or
equal to the temperature of the surface of the heat source. The
countershape may then be "flipped over" such that the heated
portion of the countershape that has a temperature substantially
near or equal to that of the surface of the heat source is exposed.
A mold may be placed on top of the heated portion of the
countershape, and the countershape is preferably conformed to the
shape of the face of the mold. In this manner, the rate of
conductive heat transfer to the lens may begin at a maximum. Heat
is preferably conductively transferred through the countershape and
the mold face to a face of the lens. The temperature of the heated
portion of the countershape may tend to decrease after the mold is
placed onto the countershape.
[0145] In an embodiment, heat distributor 910 may partially
insulate a mold member from conductive heat source 418. The heat
distributor preferably allows a gradual, uniform transfer of heat
to the mold member. The heat distributor is preferably made of
rubber and/or another suitable material. The heat distributor may
include counter-shapes of various shapes (e.g., hemispherically
concave or convex) and sizes that may be adapted to contact and
receive mold members.
[0146] In an embodiment, heat may be conductively applied by the
heat source to only one outside face of one mold member. This
outside face may be face 906 or face 907. Heat may be applied to
the back face of the lens to enhance crosslinking and/or
tintability of the tens material proximate to the surface of the
back face of the lens.
[0147] In a preferred embodiment, a thermostatically controlled hot
plate 418 is preferably used as a heat source. Glass optical mold
928 is preferably placed convex side up on hot plate 418 to serve
as a countershape. The glass optical mold preferably has about an
80 mm diameter and a radius of curvature of about 93 mm. Rubber
disc 929 may be placed over this mold 928 to provide uniform
conductive heat to the lens mold assembly. The rubber disc is
preferably made of silicone and preferably has a diameter of
approximately 74 mm and a thickness of about 3 mm. The lens mold
assembly is preferably placed on mold 928 so that outside face 906
of a mold member of the assembly rests on top of mold 928. It is
preferred that the edge of the lens mold assembly not directly
contact the hot plate. The lens mold assembly preferably receives
heat through the rubber disc and not through its mold edges.
[0148] To achieve good yield rates and reduce the incidence of
premature release while using the conductive heat method, it may be
necessary for the edge of the lens to be completely cured and dry
before conductive heat is applied. If the lens edge is incompletely
cured (i.e., liquid or gel is still present) while conductive heat
is applied, there may be a high incidence of premature release of
the lens from the heating unit.
[0149] In an embodiment, the edges of a lens may be treated to cure
or remove incompletely cured lens forming material (see above
description) before conductive heat is applied. The mold cavity may
be defined by at least gasket 908, first mold member 902, and
second mold member 904. Activating light rays may be directed
toward at least one of the mold members, thereby curing the lens
forming material to a lens preferably having front face 916, a back
face 915, and edges. Upon the formation of the lens, the gasket may
be removed from the mold assembly. An oxygen barrier may be used to
cure any remaining liquid or gel on the lens edge as described in
more detail below. An oxygen barrier treated with photoinitiator is
preferably employed. Alternatively, any remaining liquid or gel may
be removed manually. Once the edge of the lens is dry, a face of
the lens may be conductively heated using any of the methods
described herein.
[0150] In an embodiment, a lens may be tinted after receiving
conductive heat postcure treatment in a mold cavity. During tinting
of the lens, the lens is preferably immersed in a dye solution.
[0151] The operation of the lens curing system may be controlled by
a microprocessor based controller 50 (FIG. 1). Controller 50
preferably controls the operation of coating unit 20, lens curing
unit 30, and post-cure unit 40. Controller 50 may be configured to
substantially simultaneously control each of these units. In
addition, the controller may include a display 52 and an input
device 54. The display and input device may be configured to
exchange information with an operator.
[0152] Controller 50 preferably controls a number of operations
related to the process of forming a plastic lens. Many of the
operations used to make a plastic lens (e.g., coating, curing and
post-cure operations) are preferably performed under a
predetermined set of conditions based on the prescription and type
of lens being formed (e.g., ultraviolet/visible light absorbing,
photochromic, colored, etc.). Controller 50 is preferably
programmed to control a number of these operations, thus relieving
the operator from having to continually monitor the apparatus.
[0153] In some embodiments, the lens or mold members may be coated
with a variety of coatings (e.g., a scratch resistant or tinted
coating). The application of these coatings may require specific
conditions depending on the type of coating to be applied.
Controller 50 is preferably configured to produce these conditions
in response to input from the operator.
[0154] When a spin coating unit is used, controller 50 may be
configured to control the rotation of the lens or mold member
during the coating process. Controller 50 is preferably
electronically coupled to the motor of the spin coating unit. The
controller may send electronic signals to the motor to turn the
motor on and/or off. In a typical coating process the rate at which
the mold or lens is rotated is preferably controlled to achieve a
uniform and defect free coating. The controller is preferably
configured to control the rate of rotation of the mold or lens
during a curing process. For example, when a coating material is
being applied, the mold or lens is preferably spun at relatively
high rotational rates (e.g., about 900 to about 950 RPM). When the
coating material is being cured, however, a much slower rotational
rate is preferably used (e.g., about 200 RPM). The controller is
preferably configured to adjust the rotational rate of the lens or
mold depending on the process step being performed.
[0155] The controller is also preferably configured to control the
operation of lamps 24. The lamps are preferably turned on and off
at the appropriate times during a coating procedure. For example,
during the application of the coating material activating lights
are typically not used, thus the controller may be configured to
keep the lamps off during this process. During the curing process,
activating light may be used to initiate the curing of the coating
material. The controller is preferably configured to turn the lamps
on and to control the amount of time the lamps remain on during a
curing of the coating material. The controller may also be
configured to create light pulses to affect curing of the coating
material. Both the length and frequency of the light pulses may be
controlled by the controller.
[0156] The controller is also preferably configured to control
operation of the lens-curing unit. The controller may perform some
and/or all of a number of functions during the lens curing process,
including, but not limited to: (i) measuring the ambient room
temperature; (ii) determining the dose of light (or initial dose of
light in pulsed curing applications) required to cure the lens
forming composition, based on the ambient room temperature; (iii)
applying the activating light with an intensity and duration
sufficient to equal the determined dose; (iv) measuring the
composition's temperature response during and subsequent to the
application of the dose of light; (v) calculating the dose required
for the next application of activating light (in pulsed curing
applications); (vi) applying the activating light with an intensity
and duration sufficient to equal the determined second dose; (vii)
determining when the curing process is complete by monitoring the
temperature response of the lens forming composition during the
application of activating light; (viii) turning the upper and lower
light sources on and off independently; (ix) monitoring the lamp
temperature, and controlling the temperature of the lamps by
activating cooling fans proximate the lamps; and (x) turning the
fans on/off or controlling the flow rate of an air stream produced
by a fan to control the composition temperature. Herein, "dose"
refers to the amount of light energy applied to an object, the
energy of the incident light being determined by the intensity and
duration of the light.
[0157] A temperature monitor may be located at a number of
positions within the lens curing unit 30. In one embodiment an
infra-red temperature sensor may be located such that it may
measure the temperature of the mold and/or the lens forming
composition in the mold cavity. One infra-red temperature sensor
may be the Cole-Parmer Model E39669-00 (Vernon Hills, Ill.).
[0158] The temperature monitor may measure the temperature within
the chamber and/or the temperature of air exiting the chamber. The
controller may be configured to send a signal to a cooler and/or
distributor to vary the amount and/or temperature of the cooling
air. The temperature monitor may also determine the temperature at
any of a number of locations proximate the mold cavity. The
temperature monitor preferably sends a signal to the controller
such that the temperature of the mold cavity and/or the lens
forming composition may be relayed to the controller throughout the
curing process.
[0159] During the initial set-up of a curing process the
temperature of the lens forming composition within the mold cavity
may be determined. This initial temperature of the lens forming
composition may be about equal to the ambient room temperature. The
controller may then determine the initial temperature of the lens
forming composition by measuring the ambient room temperature.
Alternatively, the initial temperature of the lens forming
composition may be measured directly using the aforementioned
temperature sensors.
[0160] The controller preferably determines the initial dose to be
given to the lens forming composition based on the initial
temperature of the composition. The controller may use a table to
determine the initial dose, the table including a series of values
correlating the initial temperature to the initial dose and/or the
mass of the lens forming composition. The table may be prepared by
routine experimentation. To prepare the table a specific lens
forming composition of a specific mass is preferably treated with a
known dose of activating light. The mold cavity is preferably
disassembled and the gelation pattern of the lens forming
composition observed. This procedure may be repeated, increasing or
decreasing the dosage as dictated by the gelation patterns, until
the optimal dosage is determined for the specific lens forming
composition.
[0161] During this testing procedure the initial temperature of the
lens forming composition may be determined, this temperature being
herein referred to as the "testing temperature". In this manner,
the optimal dose for the lens forming composition at the testing
temperature may be determined. When the lens forming material has
an initial temperature that is substantially equal to the testing
temperature, the initial dosage may be substantially equal to the
experimentally determined dosage. When the lens forming material
has a temperature that is substantially greater or less than the
testing temperature, the initial dose may be calculated based on a
function of the experimentally determined initial dose. In single
dose applications the initial dose of activating light will be
sufficient to substantially cure the plastic lens. For multi-pulse
applications, the initial dose will be followed by additional light
doses.
[0162] In an embodiment, the controller is preferably adapted to
control the intensity and duration of activating light pulses
delivered from the activating light source and the time interval
between the pulses. The activating light source may include a
capacitor which stores the energy required to deliver the pulses of
activating light. The capacitor may allow pulses of activating
light to be delivered as frequently as desired. A light sensor may
be used to determine the intensity of activating light emanating
from the source. The light sensor is preferably adapted to send a
signal to the controller, which is preferably adapted to maintain
the intensity of the activating light at a selected level. A filter
may be positioned between the activating light source and the light
sensor and is preferably adapted to inhibit a portion of the
activating light rays from contacting the light sensor. This filter
may be necessary to keep the intensity of the activating light upon
the light sensor within the detectable range of the light
sensor.
[0163] In an embodiment, a shutter system may be used to control
the application of activating light rays to the lens forming
material. The shutter system preferably includes air-actuated
shutter plates that may be inserted into the curing chamber to
prevent activating light from reaching the lens forming material.
The shutter system may be coupled to the controller, which may
actuate an air cylinder to cause the shutter plates to be inserted
or extracted from the curing chamber. The controller preferably
allows the insertion and extraction of the shutter plates at
specified time intervals. The controller may receive signals from
temperature sensors allowing the time intervals in which the
shutters are inserted and/or extracted to be adjusted as a function
of a temperature of the lens forming composition and/or the molds.
The temperature sensor may be located at numerous positions
proximate the mold cavity and/or casting chamber.
[0164] Alternatively, the shutter system may include an LCD filter
that may be darkened to inhibit the activating light from reaching
the lens forming material. The controller is preferably configured
to darken the LCD panel at specified time intervals. The controller
may receive signals from temperature sensors allowing the time
intervals in which the LCD panel is darkened to be adjusted as a
function of a temperature of the lens forming composition and/or
the molds.
[0165] In an embodiment, a single dose of activating light may be
used to cure a lens forming composition. The controller may monitor
the change in temperature of the lens forming composition during
the application of activating light. The activating light
preferably initiates a polymerization reaction such that the
temperature of the lens forming composition begins to rise. By
monitoring the change in temperature over a time period the
controller may determine the rate of temperature change. The
controller preferably controls the polymerization of the lens
forming composition based on the rate of temperature change. When
the temperature is found to be rising at a faster than desired
rate, the desired rate being determined based on previous
experiments, the temperature controller may alter the intensity
and/or the duration of the pulse such that the rate of temperature
change is lowered. The duration of the activating light may be
shortened and/or the intensity of the activating light may be
diminished to achieve this effect. The controller may also increase
the rate of cooling air blowing across the mold to help lower the
temperature of the lens forming composition. Alternatively, if the
temperature of the reaction is increasing too slowly, the
controller may increase the intensity of the activating light
and/or increase the duration of the pulse. Additionally, the
controller may decrease the rate of cooling air blowing across the
mold to allow the temperature of the lens forming composition to
rise at a faster rate.
[0166] One manner in which the temperature may be controlled is by
monitoring the temperature during the application of activating
light, as described in U.S. Pat. No. 5,422,046 to Tarshiani, et al.
During activating light irradiation, the temperature of the lens
forming composition tends to rise. When the temperature reaches a
predetermined upper set point the activating light source is
preferably turned off. Removal of the activating energy may allow
the temperature to gradually begin to fall. When the temperature is
reduced to a predetermined lower set point the activating light
source is preferably turned on. In this manner, the temperature may
be controlled within a desired range. This temperature range tends
to be very broad due to the nature of the lens forming
polymerization reactions. For example, turning the activating light
off at a predetermined upper set point may not insure that the
temperature of the lens forming composition will stop at that
point. In fact, it is more likely that the temperature may continue
to rise after the upper set point has been reached. To offset this
effect the upper set point may be set at a temperature lower than
the upper temperature desired during the lens forming process. Such
a method of temperature control may be insufficient to control the
temperature. As shown in FIG. 17, increase in the temperature of a
lens forming composition during the lens forming process may not be
constant. Since the increase in temperature of the composition
changes as the process continues, the use of an upper set point for
controlling the temperature may not adequately prevent the
composition from reaching greater than desired temperatures.
Additionally, near the completion of the process the upper set
point may be set too low, thereby preventing the lens forming
composition from reaching a temperature that is adequate to
maintain the polymerization reaction due to insufficient doses of
activating light.
[0167] In an embodiment the temperature control process may be
described as a modified Proportional-Integral-Derivative ("PID")
control method. Preferably, the controller is configured to operate
the lens-curing system using a PID control method. The controller
may use a number of factors to determine the dose of activating
light applied for each pulse. The controller preferably measures
the temperature as well as the rate of temperature change.
[0168] The PID control method involves the combination of
proportional, integral and derivative controlling methods. The
first, proportional control, may be achieved by mixing two control
factors in such a way as to achieve the desired effect. For lens
control the two factors which tend to have the most effect on
temperature control may be the dosage of activating light and the
flow rate of the cooling air. These two factors may be altered to
achieve a desired temperature response. If the temperature must be
raised as rapidly as possible a full dosage of light may delivered
with no cooling air present. Similarly, if the composition must be
rapidly cooled the sample may be treated with cooling air only.
Preferably the two factors, application of incident light and
cooling, are preferably both applied to achieve the desired
temperature response. The mixture, or proportions of these factors
may allow the temperature of the composition to be controlled.
[0169] The use of proportional control tends to ignore other
effects that influence the temperature of the lens forming
composition. During the lens forming process, the temperature of
the lens forming composition may vary due to the rate of
polymerization of the reaction. When the composition is undergoing
a rapid rate of polymerization, the temperature of the composition
may rise beyond that determined by the proportional setting of the
activating light and cooling air controls. Toward the end of the
process the lens may become too cool due to the a reduction in the
rate of polymerization of the composition. The use of proportional
control may therefore be inadequate to control this procedure and
may lead to greater than desired variations in the temperature of
the composition.
[0170] These limitations may be overcome by altering the
proportions of the two components in response to the temperature of
the composition. A single set point may be used to control the
temperature of a reaction. As the temperature rises above this set
point the proportion of the activating light and cooling may be
adjusted such that the temperature begins to lower back toward the
set point. If the temperature drops below the set point the
proportion of activating light and cooling may be adjusted to raise
the temperature back to the set point. Typically, to lower the
temperature the dose of activating light may be reduced and/or the
flow rate of the cooling air may be increased. To raise the
temperature the dose of activating light may be increased and/or
the flow rate of the cooling air may be decreased.
[0171] The use of proportional control in this manner may not lead
to a steady temperature. Depending on the set point and the
response time of the lens forming composition to variations in the
dosage of light and/or cooling air, the temperature may oscillate
over the set point, never attaining a steady value. To better
control such a system the rate of change of the temperature over a
predetermined time period is preferably monitored. As the
temperature rises the rate at which the temperature rises is
preferably noted. Based on this rate of change the controller may
then alter the dosage of activating light and/or cooling air such
that a temperature much closer to the set point may be achieved.
Since the rate will change in response to changes in the rate of
polymerization, such a system may better control the temperature of
the lens forming composition throughout the process.
[0172] In an embodiment, the controller may be a modified PID
controller or a computer programmed to control the lens curing unit
using a PID control scheme. The controller preferably monitors the
temperature of the lens forming composition throughout the process.
Additionally, the controller may monitor the rate of change of
temperature throughout the reaction. When a plurality of pulses are
being applied to control the polymerization, the controller
preferably controls the duration and intensity of each pulse to
control the temperature of the composition. In a typical process
the rate of change in temperature is preferably monitored after the
application of an activating light pulse. If the temperature is
trending in an upward direction, the controller preferably waits
for the temperature to crest and start descending, before the
application of additional light pulses. This cresting temperature
may vary, as depicted in FIG. 17, throughout the lens forming
process. After the temperature has passed a predetermined set
point, a dose, calculated from the rate of change in temperature
caused by the application of the previous pulse, may be applied to
the lens forming composition. After the light pulse is delivered
the controller may repeat the procedure additional times.
[0173] When the reaction nears completion the controller detects
the lack of response to the last exposure (i.e. the lens
temperature did not increase appreciably). At this point the
controller may apply a final dose to assure a substantially
complete cure and notify the operator that the mold assembly is
ready to be removed form the chamber.
[0174] One method of controlling the dose of light reaching the
lens may be through the use of filters, as described above. In one
embodiment, an LCD filter system may be used to adjust the
intensity of incoming light. The LCD system is preferably coupled
to the controller such that a pattern displayed by the LCD system
may be altered by the controller. The controller preferably
configures the pattern of light and dark areas on the LCD panel
such that light having the optimal curing intensity pattern hits
the mold assemblies. The pattern that is produced is preferably
based on the prescription and type of lens being produced.
[0175] In another embodiment, the controller may actively change
the pattern on the LCD panel during a curing cycle. For example,
the pattern of light and dark regions may be manipulated such that
the lens is cured from the center of the lens then gradually
expanded to the outer edges of the lens. This type of curing
pattern may allow a more uniformly cured lens to be formed. In some
instances, curing in this manner may also be used to alter the
final power of the formed lens.
[0176] In another embodiment, the LCD panel may be used as a
partial shutter to reduce the intensity of light reaching the lens
assembly. By blackening the entire LCD panel the amount of light
reaching any portion of the mold assembly may be reduced. The
controller may be configured to cause the LCD panel to create
"pulses" of light by alternating between a transmissive and
darkened mode. By having the LCD panel create these light "pulses"
the need for a flash ballast or similar pulse generating equipment
may be unnecessary. Thus the use of a controller and an LCD panel
may simplify the system.
[0177] In some embodiments, the lens may require a post-curing
process. The post-cure process may require specific conditions
depending on the type of lens being formed. The controller is
preferably configured to produce these conditions in response to
input from the operator.
[0178] The controller is preferably configured to control the
operation of lamps 440 (See FIG. 12). The lamps are preferably
turned on and off at the appropriate times during the post-cure
procedure. For example, in some post-cure operations the lights may
not be required, thus the controller would keep the lights off
during this process. During other processes, the lights may be used
to complete the curing of the lens. The controller is preferably
configured to turn the lights on and to control the amount of time
the lights remain on during a post-cure procedure. The controller
may also be configured to create light pulses during the post-cure
procedure. Both the length and frequency of the light pulses may be
controlled by the controller.
[0179] The controller is preferably configured to control operation
of the heating device 418 during the post-cure operation. Heating
device 418 is preferably turned on and off to maintain a
predetermined temperature within the post-cure unit. Alternatively,
when a resistive heater is used, the current flow through the
heating element may be altered to control the temperature within
the post-cure unit. Preferably both the application of light and
heat are controlled by the controller. The operation of fans,
coupled to the post-cure unit, is also preferably controlled by the
controller. The fans may be operated by the controller to circulate
air within or into/out of the post-cure unit.
[0180] Additionally, the controller may provide system diagnostics
to determine if the system is operating properly. The controller
may notify the user when routine maintenance is due or when a
system error is detected. For example, the controller may monitor
the current passing through lamps of the coating, lens curing, or
post-cure unit to determine if the lamps are operating properly.
The controller may keep track of the number of hours that the lamps
have been used. When a lamp has been used for a predetermined
number of hours a message may be transmitted to an operator to
inform the operator that the lamps may require changing. The
controller may also monitor the intensity of light produced by the
lamp. A photodiode may be placed proximate the lamps to determine
the intensity of light being produced by the lamp. If the intensity
of light falls outside a predetermined range, the current applied
to the lamp may be adjusted to alter the intensity of light
produced (either increased to increase the intensity; or decreased
to decrease the intensity). Alternatively, the controller may
transmit a message informing the operator that a lamp needs to be
changed when the intensity of light produced by the lamp drops
below a predetermined value.
[0181] The controller may also manage an interlock system for
safety and energy conservation purposes. If the lens drawer
assembly from the coating or post-cure units are open the
controller is preferably configured to prevent the lamps from
turning on. This may prevent the operator from inadvertently
becoming exposed to the light from the lamps. Lamps 24 for the
coating unit 20 are preferably positioned on cover 22 (See FIG. 1).
In order to prevent inadvertent exposure of the operator to light
from lamps 24 a switch is preferably built into the cover, as
described above. The controller is preferably configured to prevent
the lamps 24 from turning on when the cover is open. The controller
may also automatically turn lamps 24 off if the cover is opened
when the tenses are on. Additionally, the controller may conserve
energy by keeping fans and other cooling devices off when the lamps
are off.
[0182] The controller may also be configured to interact with the
operator. The controller preferably includes an input device 54 and
a display screen 52. The input device may be a keyboard (e.g., a
full computer keyboard or a modified keyboard), a light sensitive
pad, a touch sensitive pad, or similar input device. A number the
parameters controlled by the controller may be dependent on the
input of the operator. In the initial set up of the apparatus, the
controller may allow the operator to input the type of lens being
formed. This information may include type of lens (clear,
ultraviolet absorbing, photochromic, colored, etc.), prescription,
and type of coatings (e.g., scratch resistant or tint).
[0183] Based on this information the controller is preferably
configured to transmit information back to the operator. The
operator may be instructed to select mold members for the mold
assembly. The mold members may be coded such that the controller
may indicate to the operator which molds to select by transmitting
the code for each mold member. The controller may also determine
the type of gasket required to properly seal the mold members
together. Like the mold members, the gaskets may also be coded to
make the selection of the appropriate gasket easier.
[0184] The lens forming compositions may also be coded. For the
production of certain kinds of lenses a specific lens forming
composition may be required. The controller may be configured to
determine the specific composition required and transmit the code
for that composition to the operator. The controller may also
signal to the operator when certain operations need to be performed
or when a particular operation is completed (e.g. when to place the
mold assembly in the lens curing unit, when to remove the mold
assembly, when to transfer the mold assembly, etc.).
[0185] Referring now to FIG. 38, another embodiment of a plastic
lens curing apparatus is generally indicated by reference numeral
1000. As shown in FIG. 38, lens forming apparatus 1000 includes at
least one coating unit 1020, a pair of stacked lens curing units
1030 and 1035, a post-cure unit 1040, and a controller 1050.
Preferably, apparatus 1000 includes two coating units 1020. Coating
unit 1020 is preferably configured to apply a coating layer to a
mold member or a lens. Preferably, coating unit 1020 is a spin
coating unit. Each of the lens curing units, 1030 and 1035,
includes an activating light source for producing activating light.
The activating light source is preferably configured to direct
light toward a mold assembly. Post-cure unit 1040 is preferably
configured to complete the polymerization of partially cured
plastic lenses. Post-cure unit 1040 preferably includes an
activating light source and a heat source. Controller 1050 is
preferably a programmable logic controller. Controller 1050 is
preferably coupled to coating units 1020, lens curing units 1030
and 1035, and post-cure unit 1040, such that the controller may be
capable of substantially simultaneously operating the four units
1020, 1030, 1035 and 1040. Controller 50 may be a computer. During
the production of plastic lenses the lens curing step may be the
most time consuming part of the process. By adding additional
curing units to the system the throughput of the system may be
increased, allowing the operator to form more lenses in a given
time period.
Lens Forming Compositions
[0186] The lens forming material may include any suitable liquid
monomer or monomer mixture and any suitable photosensitive
initiator. As used herein "monomer" is taken to mean any compound
capable of undergoing a polymerization reaction. Monomers may
include non-polymerized material or partially polymerized material.
When partially polymerized material is used as a monomer, the
partially polymerized material preferably contains functional
groups capable of undergoing further reaction to form a new
polymer. The lens forming material preferably includes a
photoinitiator that interacts with activating light. In one
embodiment, the photoinitiator absorbs ultraviolet light having a
wavelength in the range of 300 to 400 nm. In another embodiment,
the photoinitiator absorbs actinic light having a wavelength in the
range of about 380 nm to 490 nm. The liquid lens forming material
is preferably filtered for quality control and placed in the lens
molding cavity 382 by pulling the annular casket 380 away from one
of the opposed mold members 378 and injecting the liquid lens
forming material into the lens molding cavity 382 (See FIG. 11).
Once the lens molding cavity 382 is filled with such material, the
annular gasket 380 is preferably replaced into its sealing relation
with the opposed mold members 378.
[0187] Those skilled in the art will recognize that once the cured
lens is removed from the lens molding cavity 382 by disassembling
the opposed mold members 378, the lens may be further processed in
a conventional manner, such as by grinding its peripheral edge.
[0188] A polymerizable lens forming composition includes an
aromatic-containing bis(allyl carbonate)-functional monomer and at
least one polyethylenic-functional monomer containing two
ethylenically unsaturated groups selected from acrylyl or
methacrylyl. In a preferred embodiment, the composition further
includes a suitable photoinitiator. In other preferred embodiments,
the composition may include one or more polyethylenic-functional
monomers containing three ethylenically unsaturated groups selected
from acrylyl or methacrylyl, and a dye.
[0189] Aromatic-containing bis(allyl carbonate)-functional monomers
include bis(allyl carbonates) of dihydroxy aromatic-containing
material. The dihydroxy aromatic-containing material from which the
monomer is derived may be one or more dihydroxy aromatic-containing
compounds. Preferably the hydroxyl groups are attached directly to
nuclear aromatic carbon atoms of the dihydroxy aromatic-containing
compounds. The monomers are themselves known and may be prepared by
procedures well known in the art.
[0190] The aromatic-containing bis(allyl carbonate)-functional
monomers may be represented by the formula: 1
[0191] in which A.sub.1 is the divalent radical derived from the
dihydroxy aromatic-containing material and each R.sub.0 is
independently hydrogen, halo, or a C.sub.1-C.sub.4 alkyl group. The
alkyl group is usually methyl or ethyl. Examples of R.sub.0 include
hydrogen, chloro, bromo, fluoro, methyl, ethyl, n-propyl, isopropyl
and n-butyl. Most commonly R.sub.0 is hydrogen or methyl; hydrogen
is preferred. A subclass of the divalent radical Al which is of
particular usefulness is represented by the formula: 2
[0192] in which each R.sub.1 is independently alkyl containing from
1 to about 4 carbon atoms, phenyl, or halo; the average value of
each (a) is independently in the range of from 0 to 4; each Q is
independently oxy, sulfonyl, alkanediyl having from 2 to about 4
carbon atoms, or alkylidene having from 1 to about 4 carbon atoms;
and the average value of n is in the range of from 0 to about 3.
Preferably Q is methylethylidene, viz., isopropylidene.
[0193] Preferably the value of n is zero, in which case A.sub.1 is
represented by the formula: 3
[0194] in which each R.sub.1, each a, and Q are as discussed in
respect of Formula II Preferably the two free bonds are both in the
ortho or para positions. The para positions are especially
preferred.
[0195] The dihydroxy aromatic-containing compounds from which
A.sub.1 is derived may also be polyether-functional chain extended
compounds. Examples of such compounds include alkaline oxide
extended bisphenols. Typically the alkaline oxide employed is
ethylene oxide, propylene oxide, or mixtures thereof. By way of
exemplification, when para, para-bisphenols are chain extended with
ethylene oxide, the bivalent radical A.sub.1 may often be
represented by the formula: 4
[0196] where each R.sub.1, each a, and Q are as discussed in
respect of Formula II, and the average values of j and k are each
independently in the range of from about 1 to about 4.
[0197] A preferred aromatic-containing bis(allyl
carbonate)-functional monomer is represented by the formula: 5
[0198] and is commonly known as bisphenol A bis(allyl
carbonate).
[0199] A wide variety of compounds may be used as the polyethylenic
functional monomer containing two or three ethylenically
unsaturated groups. A preferred polyethylenic functional compound
containing two or three ethylenically unsaturated groups may be
generally described as the acrylic acid esters and the methacrylic
acid esters of aliphatic polyhydric alcohols, such as, for example,
the di- and triacrylates and the di- and trimethacrylates of
ethylene glycol, triethylene glycol, tetraethylene glycol,
tetramethylene glycol, glycerol, diethyleneglycol, butyleneglycol,
propyleneglycol, pentanediol, hexanediol, trimethylolpropane, and
tripropyleneglycol. Examples of specific suitable
polyethylenic--functional monomers containing two or three
ethylenically unsaturated groups include
trimethylolpropanetriacrylate (TMPTA), tetraethylene glycol
diacrylate (TTEGDA), tripropylene glycol diacrylate (TRPGDA), 1,6
hexanedioldimethacrylate (HDDMA), and hexanedioldiacrylate
(HDDA).
[0200] In general, a photoinitiator for initiating the
polymerization of the lens forming composition preferably exhibits
an absorption spectrum over the 300-400 nm range. High absorptivity
of a photoinitiator in this range, however, is not desirable,
especially when casting a thick lens. The following are examples of
illustrative photoinitiator compounds: methyl benzoylformate,
2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl
ketone, 2,2-di-sec-butoxyacetophenone, 2,2-diethoxyacetophenone,
2,2-diethoxy-2-phenyl-acetophenone,
2,2-dimethoxy-2-phenyl-acetophenone, benzoin methyl ether, benzoin
isobutyl ether, benzoin, benzil, benzyl disulfide,
2,4-dihydroxybenzophenone, benzylideneacetophenone, benzophenone
and acetophenone. Preferred photoinitiator compounds are
1-hydroxycyclohexyl phenyl ketone (which is commercially available
from Ciba-Geigy as Irgacure 184), methyl benzoylformate (which is
commercially available from Polysciences, Inc.), or mixtures
thereof.
[0201] Methyl benzoylformate is a generally preferred
photoinitiator because it tends to provide a slower rate of
polymerization. The slower rate of polymerization tends to prevent
excessive heat buildup (and resultant cracking of the lens) during
polymerization. In addition, it is relatively easy to mix liquid
methyl benzoylformate (which is liquid at ambient temperatures)
with many acrylates, diacrylates, and allyl carbonate compounds to
form a lens forming composition. The lenses produced with the
methyl benzoylformate photoinitiator tend to exhibit more favorable
stress patterns and uniformity.
[0202] A strongly absorbing photoinitiator will absorb most of the
incident light in the first millimeter of lens thickness, causing
rapid polymerization in that region. The remaining light will
produce a much lower rate of polymerization below this depth and
will result in a lens that has visible distortions. An ideal
photoinitiator will exhibit high activity, but will have a lower
extinction coefficient in the useful range. A lower extinction
coefficient of photoinitiators at longer wavelengths tends to allow
the activating light to penetrate deeper into the reaction system.
This deeper penetration of the activating light allows
photoinitiator radicals to form uniformly throughout the sample and
provide excellent overall cure. Since the sample may be irradiated
from both top and bottom, a system in which appreciable activating
light reaches the center of the thickest portion of the lens is
preferred. The photoinitiator solubility and compatibility with the
monomer system is also an important requirement.
[0203] An additional consideration is the effect of the
photoinitiator fragments in the finished polymer. Some
photoinitiators generate fragments that impart a yellow color to
the finished lens. Although such lenses actually absorb very little
visible light, they may be cosmetically undesirable.
[0204] Photoinitiators are often very system specific so that
photoinitiators that are efficient in one system may function
poorly in another. In addition, the initiator concentration, to a
large extent, may be dependent on the incident light intensity and
the monomer composition. The identity of the initiator and its
concentration may be important for any particular formulation. A
concentration of initiator that is too high may lead to cracking
and yellowing of the lens. Concentrations of initiator that are too
low may lead to incomplete polymerization and a soft material.
[0205] Dyes and/or pigments are optional materials that may be
present when high transmission of light is not necessary.
[0206] The listing of optional ingredients discussed above is by no
means exhaustive. These and other ingredients may be employed in
their customary amounts for their customary purposes so long as
they do not seriously interfere with good polymer formulating
practice.
[0207] 1. Activating, Light Curable Lens Forming Compositions
[0208] According to a preferred embodiment, a lens forming
composition that may be cured with activating light includes an
aromatic-containing bis(allyl carbonate) functional monomer,
preferably bisphenol A bis(allyl carbonate), admixed with one or
more faster reacting polyethylenic functional monomers containing
two acrylate or methacrylate groups such as 1,6 hexanediol
dimethacrylate (HDDMA), 1,6 hexanediol diacrylate (HDDA),
tetraethylene glycol diacrylate (TTEGDA), and tripropylene glycol
diacrylate (TRPGDA) and optionally a polyethylenic functional
monomer containing three acrylate groups such as trimethylolpropane
triacrylate (TMPTA). Generally, compounds containing acrylate
groups polymerize much faster than those containing allyl
groups.
[0209] According to one embodiment, the liquid lens forming
composition includes bisphenol A bis(allyl carbonate) in place of
DEG-BAC. The bisphenol A bis(allyl-carbonate) monomer has a higher
refractive index than DEG-BAC making it more suitable for the
production of thinner lenses, which may be important with
relatively thick positive or negative lenses. The bisphenol A
bis(allyl-carbonate) monomer is commercially available from PPG
Industries under the trade name HIRI I or CR-73. Lenses made from
this product sometimes have a very slight, barely detectable,
degree of yellowing. A small amount of a blue dye consisting of 9,
10-anthracenedione, 1-hydroxy-4-[(4-methylphenyl)amino] available
as Thermoplast Blue 684 from BASF Wyandotte Corp. is preferably
added to the composition to counteract the yellowing. In addition,
the yellowing tends to disappear if the lens is subjected to the
above-described post-cure heat treatment. Moreover, if not
post-cured the yellowing tends to disappear at ambient temperature
after approximately 2 months.
[0210] TTEGDA, available from Sartomer and Radcure, is a diacrylate
monomer that, preferably, is included in the composition because it
is a fast polymerizing monomer that reduces yellowing and yields a
very clear product. If too much TTEGDA is included in the more
preferred composition, i.e., greater than about 25% by weight,
however, the finished lens may be prone to cracking and may be too
flexible as this material softens at temperatures above 40.degree.
C. If TTEGDA is excluded altogether, the finished lens may be too
brittle.
[0211] HDDMA, available from Sartomer, is a dimethacrylate monomer
that has a very stiff backbone between the two methacrylate groups.
HDDMA, preferably, is included in the composition because it yields
a stiffer polymer and increases the hardness and strength of the
finished lens. This material is quite compatible with the bisphenol
A bis(allyl carbonate) monomer. HDDMA contributes to high
temperature stiffness, polymer clarity and speed of
polymerization.
[0212] TRPGDA, available from Sartomer and Radcure, is a diacrylate
monomer that, preferably, is included in the composition because it
provides good strength and hardness without adding brittleness to
the finished lens. This material is also stiffer than TTEGDA.
[0213] TMPTA, available from Sartomer and Radcure, is a triacrylate
monomer that, preferably, is included in the composition because it
provides more crosslinking in the finished lens than the
difunctional monomers. TMPTA has a shorter backbone than TTEGDA and
increases the high temperature stiffness and hardness of the
finished lens. Moreover, this material contributes to the
prevention of optical distortions in the finished lens. TMPTA also
contributes to high shrinkage during polymerization. The inclusion
of too much of this material in the more preferred composition may
make the finished lens too brittle.
[0214] Certain of the monomers that are preferably utilized, such
as TTEGDA, TRPGDA and TMPTA, include impurities and have a yellow
color in certain of their commercially available forms. The yellow
color of these monomers is preferably reduced or removed by passing
them through a column of alumina (basic) which includes aluminum
oxide powder--basic. After passage through the alumina column
differences between monomers obtained from different sources may be
substantially eliminated. It is preferred, however, that the
monomers be obtained from a source which provides the monomers with
the least amount of impurities contained therein. The composition
is preferably filtered prior to polymerization thereof to remove
suspended particles.
[0215] 2. Lens Forming Compositions Including Ultraviolet/Visible
Light Absorbing Materials
[0216] Materials that absorb various degrees of ultraviolet/visible
light may be used in an eyeglass lens to inhibit
ultraviolet/visible light from being transmitted through the
eyeglass lens. The phrase "ultraviolet/visible light" is taken to
mean light having a wavelength in the ultraviolet light range or
both the ultraviolet and visible light ranges. The phrase
"ultraviolet/visible light absorbing compounds" refers to compounds
which absorb ultraviolet/visible light. An eyeglass lens that
includes ultraviolet/visible light absorbing compounds
advantageously inhibits ultraviolet/visible light from being
transmitted to the eye of a user wearing the lens. Thus, eyeglass
lenses containing ultraviolet/visible light absorbing compounds may
function to protect the eyes of a person from damaging
ultraviolet/visible light. Photochromic pigments are one type of
ultraviolet/visible light absorbing compounds. Photochromic
inorganic lenses which contain silver halide particles or cuprous
halide particles suspended throughout the body of the lens are well
known and have been commercially available for decades. Such
inorganic lenses, however, suffer the disadvantage of being
relatively heavy and less comfortable to the wearer when compared
to organic lenses. Consequently, the majority of the eyeglass
lenses produced today are typically formed from organic materials
rather than inorganic materials. Accordingly, photochromic plastic
eyeglass lenses have been the subject of considerable attention in
recent years.
[0217] Efforts to provide a plastic eyeglass lens which
demonstrates photochromic performance have primarily centered
around permeating and/or covering the surface(s) of an already
formed lens with photochromic pigments. This general technique may
be accomplished by a number of specific methods. For example, (a)
the lens may be soaked in a heated bath which contains photochromic
pigments, (b) photochromic pigments may be transferred into the
surface of a plastic lens via a solvent assisted transfer process,
or (c) a coating containing photochromic pigments may be applied to
the surface of a lens. A problem with such methods may be that the
lens often might not absorb enough of the photochromic pigments at
low temperatures, resulting in an eyeglass lens which does not
exhibit acceptable photochromic performance. Unfortunately,
increasing the temperature used during absorption of the
photochromic pigments may not be a solution to this problem since
at high temperatures degradation of the polymer contained within
the lens may occur.
[0218] Attempts have also been made to incorporate photochromic
pigments into the liquid monomer from which plastic lenses are
thermally polymerized. See U.S. Pat. No. 4,913,544 to Rickwood et
al., wherein it is disclosed that triethyleneglycol dimethacrylate
monomer was combined with 0.2% by weight of various spiro-oxazine
compounds and 0.1% benzoyl peroxide and subsequently thermally
polymerized to form non-prescription eyeglass lenses. Generally,
efforts to incorporate photochromic pigments into the liquid
monomer from which the lenses are polymerized have been
unsuccessful. It is believed that the organic peroxide catalysts
utilized to initiate the thermal polymerization reaction tend to
damage the photochromic pigments, impairing their photochromic
response.
[0219] Curing of an eyeglass lens using activating light to
initiate the polymerization of a lens forming composition generally
requires that the composition exhibit a high degree of activating
light transmissibility so that the activating radiation may
penetrate to the deeper regions of the lens cavity. Otherwise the
resulting cast lens may possess optical aberrations and
distortions. The cast lens may also contain layers of cured
material in the regions closest to the transparent mold faces,
sandwiching inner layers which are either incompletely cured,
gelled, barely gelled, or even liquid. Often, when even small
amounts of ultraviolet/visible light absorbing compounds of the
types well known in the art are added to a normally light curable
lens forming composition, substantially the entire amount of lens
forming composition contained within the lens cavity may remain
liquid in the presence of activating light.
[0220] Photochromic pigments which have utility for photochromic
eyeglass lenses absorb ultraviolet light strongly and change from
an unactivated state to an activated state when exposed to
ultraviolet light. The presence of photochromic pigments, as well
as other ultraviolet/visible light absorbing compounds within a
lens forming composition, generally does not permit enough
activating radiation to penetrate into the depths of the lens
cavity sufficient to cause photoinitiators to break down and
initiate polymerization of the lens forming composition. Thus, it
may be difficult to cure a lens forming composition containing
ultraviolet/visible light absorbing compounds using activating
light (e.g., if the activating light has a wavelength in the
ultraviolet or visible region). It is therefore desirable to
provide a method for using activating light to initiate
polymerization of an eyeglass lens forming monomer which contains
ultraviolet/visible light absorbing compounds, in spite of the high
activating light absorption characteristics of the
ultraviolet/visible light absorbing compounds. Examples of such
ultraviolet/visible light absorbing compounds other than
photochromic pigments are fixed dyes and colorless additives.
[0221] In an embodiment, an ophthalmic eyeglass lens may be made
from a lens forming composition comprising a monomer, an
ultraviolet/visible light absorbing compound, a photoinitiator, and
a co-initiator. Herein, an "ophthalmic eyeglass lens" is taken to
mean any plastic eyeglass lens, including a prescription lens, a
non-prescription lens, a progressive lens, a sunglass lens, and a
bifocal lens. The lens forming composition, in liquid form, is
preferably placed in a mold cavity defined by a first mold member
and a second mold member. It is believed that activating light
which is directed toward the mold members to activate the
photoinitiator causes the photoinitiator to form a polymer chain
radical. The polymer chain radical preferably reacts with the
co-initiator more readily than with the monomer. The co-initiator
may react with a fragment or an active species of either the
photoinitiator or the polymer chain radical to produce a monomer
initiating species in the regions of the lens cavity where the
level of activating light may be either relatively low or not
present.
[0222] Preferably, the monomers selected as components of the lens
forming composition are capable of dissolving the
ultraviolet/visible light absorbing compounds added to them.
Herein, "dissolving" is taken to mean being substantially
homogeneously mixed with. For example, monomers may be selected
from a group including polyether (allyl carbonate) monomers,
multi-functional acrylate monomers, and multi-functional
methacrylic monomers for use in an ultraviolet/visible light
absorbing lens forming composition.
[0223] In an embodiment, the following mixture of monomers,
hereinafter referred to as PRO-629, may be blended together before
addition of other components required to make the lens forming
composition. This blend of monomers is preferably used as the basis
for a lens forming composition to which ultraviolet/visible light
absorbing compounds are added.
[0224] 32% Tripropyleneglycol diacrylate (SR-306)
[0225] 21% Tetraethyleneglycol diacrylate (SR-268)
[0226] 20% Trimethylolpropane triacrylate (SR-351)
[0227] 17% Bisphenol A bis allyl carbonate (HiRi)
[0228] 10% Hexanediol dimethacrylate (SR-239)
[0229] The acrylic and methacrylic monomers listed above are
commercially available from Sartomer Company in Exton, Pa. The
bisphenol A bis allyl carbonate is commercially available from PPG
in Pittsburgh, Pa. The hexanediol dimethacrylate is hereinafter
referred to as HDDMA.
[0230] A polymerization inhibitor may be added to the monomer
mixture at relatively low levels to inhibit polymerization of the
monomer at inappropriate times (e.g., during storage). Preferably
about 0 to 50 ppm of monomethylether hydroquinone (MEHQ) are added
to the monomer mixture. It is also preferred that the acidity of
the monomer mixture be as low as possible. Preferably less than
about 100 ppm residual acrylic acid exists in the mixture. It is
also preferred that the water content of the monomer mixture be
relatively low, preferably less than about 0.15%.
[0231] Photoinitiators include: 1-hydroxycyclohexylphenyl ketone
commercially available from Ciba Additives under the trade name of
Irgacure 184; mixtures of bis(2,6-dimethoxybenzoyl)
(2,4,4-trimethyl phenyl) phosphine oxide and
2-hydroxy-2-methyl-1-phenyl-propan-1-one commercially available
from Ciba Additives under the trade name of Irgacure 1700; mixtures
of bis(2,6-dimethoxybenzoyl) (2,4,4 trimethyl phenyl) phosphine
oxide and 1-hydroxycyclohexylphenyl ketone commercially available
from Ciba Additives under the trade names of Irgacure 1800 and
Irgacure 1850; 2,2-dimethoxy-2-phenyl acetophenone commercially
available from Ciba Additives under the trade name of Irgacure 651;
2-hydroxy-2-methyl-1-phenyl-propan-1-one commercially available
from Ciba Additives under the trade names of Darocur 1173; mixtures
of 2,4,6-trimethylbenzoyl-diphenylphoshine oxide and
2-hydroxy-2-methyl-1-ph- enyl-propan-1-one commercially available
from Ciba Additives under the trade name of Darocur 4265;
2,2-diethoxyacetophenone (DEAP) commercially available from First
Chemical Corporation of Pascagoula, Miss., benzil dimethyl ketal
commercially available from Sartomer Company under the trade name
of KB-1; an alpha hydroxy ketone initiator commercially available
from Sartomer company under the trade name of Esacure KIP 100F;
2-methyl thioxanthone (MTX), 2-chloro-thioxanthone (CTX),
thioxanthone (TX), and xanthone, all commercially available from
Aldrich Chemical; 2-isopropyl-thioxanthone (ITX) commercially
available from Aceto Chemical in Flushing, N.Y.; mixtures of
triaryl sulfonium hexafluoroantimonate and propylene carbonate
commercially available from Sartomer Company under the trade names
of SarCat CD 1010, SarCat 1011, and SarCat K185; diaryliodinium
hexafluoroantimonate commercially available from Sartomer Company
under the trade name of SarCat CD-1012; mixtures of benzophenone
and 1-hydroxycyclohexylphenyl ketone commercially available from
Ciba Additives under the trade name of Irgacure 500;
2-benzyl-2-N,N-dimethylam- ino-1-(4-morpholinophenyl)-1-butanone
commercially available from Ciba Additives under the trade name of
Irgacure 369; 2-methyl-1-[4-(methylthio-
)phenyl]-2-morpholino-propan-1-one commercially available from Ciba
Additives under the trade name of Irgacure 907;
bis(.eta.5-2,4-cyclopenta- dien-1-yl)-b
is-[2,6-difluoro-3-(1H-pyrrol-1-yl) phenyl] titanium commercially
available from Ciba Additives under the trade name of Irgacure 784
DC; mixtures of 2,4,6-trimethyl-benzophenone and
4-methyl-benzophenone commercially available from Sartomer Company
under the trade name of EsaCure TZT; and benzoyl peroxide and
methyl benzoyl formate both available from Aldrich Chemical in
Milwaukee, Wis.
[0232] A preferred photoinitiator is bis(2,6-dimethoxybenzoyl)
(2,4,4 trimethyl phenyl) phosphine oxide, commercially available
from Ciba Additives in Tarrytown, N.Y. under the trade name of
CGI-819. The amount of CGI-819 present in a lens forming
composition containing photochromic compounds preferably ranges
from about 30 ppm by weight to about 2000 ppm by weight.
[0233] Co-initiators include reactive amine co-initiators
commercially available from Sartomer Company under the trade names
of CN-381, CN-383, CN-384, and CN-386, where these co-initiators
are monoacrylic amines, diacrylic amines, or mixtures thereof.
Other co-initiators include N-methyldiethanolamine (NMDEA),
triethanolamine (TEA), ethyl-4-dimethylaminobenzoate (E-4-DMAB),
ethyl-2-dimethylaminobenzoate (E-2-DMAB), all commercially
available from Aldrich Chemicals. Co-initiators which may also be
used include n-butoxyethyl-4-dimethylamin- o benzoate, p-dimethyl
amino benzaldehyde. Other co-initiators include
N,N-dimethyl-p-toluidine, octyl-p-(dimethylamino) benzoate
commercially available from The First Chemical Group of Pascagoula,
Miss.
[0234] Preferably, the co-initiator is N-methyldiethanolamine
(NMDEA) commercially available from Aldrich Chemical in Milwaukee,
Wis., CN-384 commercially available from Sartomer Company, or
CN-386 also commercially available from Sartomer Company. The
quantity of NMDEA present in a lens forming composition containing
photochromic pigments is preferably between about 1 ppm by weight
and 7% by weight and more preferably between about 0.3% and 2% by
weight. Further, certain fixed pigments which may be added to the
lens forming composition to create a background color within the
lens (i.e., to tint the lens), may also function as co-initiators.
Examples of such fixed pigments include Thermoplast Blue P, Oil
Soluble Blue II, Thermoplast Red 454, Thermoplast Yellow 104, Zapon
Brown 286, Zapon Brown 287, all commercially available from BASF
Corporation in Holland, Mich.
[0235] Ultraviolet/visible light absorbing compounds which may be
added to a normally ultraviolet/visible light transmissible lens
forming composition include 2-(2H benzotriazole-2-yl)-4-(1,1,3,3
tetramethylbutyl)phenol and 2-hydroxy-4-methoxybenzophenone, both
commercially available from Aldrich Chemical as well as mixtures of
2-[4-((2-hydroxy-3-dodecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-di-
methylphenyl)-1,3,5-triazine and
2-[4-((2-hydroxy-3-tridecyloxypropyl)-oxy-
)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl-1,3,5-triazine
commercially available from Ciba Additives under the trade name of
Tinuvin 400, mixtures of poly (oxy-1,2-ethanediyl),
.alpha.-(3-(3-(2H-benzotriazol-2-y-
l)-5-(1,1-dimethylethyl)-4-hydroxyphenyl)-1-oxopropyl)-.omega.-hydroxy
and poly (oxy-1,2-ethanediyl),
.alpha.-(3-(3-(2H-benzotriazol-2-yl)-5-(1,1-di-
methylethyl)-4-hydroxyphenyl)-1-oxopropyl)-.omega.-(3-(3-(2H-b
enzotriazol-2-yl)-5-1,1-dimethylethyl)-4-hydroxyphenyl)-1-oxopropoxy)
commercially available from Ciba Additives under the trade name of
Tinuvin 1130. Other ultraviolet/visible light absorbers may include
Tinuvin 328, Tinuvin 900, 2-(2 hydroxy-5-methyl-phenyl)
benzotriazole, ethyl-2-cyano 3,3-diphenyl acrylate, and phenyl
salicylate.
[0236] While any number of families of photochromic pigments may be
incorporated into the blend of monomers, either individually or in
combination, spiropyrans, spironaphthoxazines,
spiropyridobenzoxazines, spirobenzoxazines, napthopyrans,
benzopyrans, spirooxazines, spironapthopyrans,
indolinospironapthoxazines, indolinospironapthopyrans,
diarylnapthopyrans, and organometallic materials are of particular
interest. A phenylmercury compound available from Marks Polarized
Corporation in Hauppauge, N.Y. under the trade name of A241 may be
an appropriate organometallic material. The quantity of
photochromic pigments present in the lens forming composition is
preferably sufficient to provide observable photochromic effect.
The amount of photochromic pigments present in the lens forming
composition may widely range from about 1 ppm by weight to 5% by
weight. In preferred compositions, the photochromic pigments are
present in ranges from about 30 ppm to 2000 ppm. In the more
preferred compositions, the photochromic pigments are present in
ranges from about 150 ppm to 1000 ppm. The concentration may be
adjusted depending upon the thickness of the lens being produced to
obtain optimal visible light absorption characteristics.
[0237] In an embodiment, hindered amine light stabilizers may be
added to the lens forming composition. It is believed that these
materials act to reduce the rate of degradation of the cured
polymer caused by exposure to ultraviolet light by deactivating
harmful polymer radicals. These compounds may be effective in
terminating oxygen and carbon free radicals, and thus interfering
with the different stages of auto-oxidation and photo-degradation.
A useful hindered amine light stabilizer is
bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-sebacate commercially
available from Ciba Additives under the trade name of Tinuvin 292.
Hindered phenolic anti-oxidants and thermal stabilizers may also be
added to a lens forming composition. The hindered phenolic
compounds hereof include thiodiethylene
bis(3,5,-di-tert-butyl-4-hydroxy)- hydroxycinnamate commercially
available from Ciba Additives under the trade name of Irganox 1035
and octadecyl-3,5-bis(1,1-dimethylethyl)-4-hyd-
roxybenzene-propanoate commercially available from Ciba Additives
under the trade name of Irganox 1076.
[0238] Preferably, more than one monomer and more than one
initiator are used in a lens forming composition to ensure that the
initial polymerization of the lens forming composition with
activating light does not occur over too short a period of time.
The use of such a lens forming composition may allow greater
control over the gel formation, resulting in better control of the
optical quality of the lens. Further, greater control over the rate
of exothermic heat generation may be achieved. Thus, cracking of
the lens and premature release of the lens from the mold which are
typically caused by the release of heat may be prevented. An
example of a poor initiator system was observed when CGI-819 was
used alone as a photoinitiator in combination with the PRO-629
monomer blend to which ultraviolet/visible light absorbing
compounds had been added. When such an initiator system was used, a
fast rate of reaction occurred near the surface of the lens cavity
while a very slow rate of reaction occurred in the deeper regions
of the cavity. The resultant lens exhibited unwanted waves and
distortions.
[0239] In another example, a small amount of a co-initiator, i.e.,
NMDEA was added to the above lens forming composition. During the
curing process, two separate waves of heat were generated when the
composition was irradiated continuously with activating light at
about 600 microwatts/cm.sup.2. One possible explanation for this
phenomena is that the first wave resulted from reaction of the
NMDEA and the second wave resulted from the reaction of the
unconsumed portion of the CGI-819. Another possible explanation is
that the rate of reaction was faster in the top portion than in the
bottom portion of the lens forming composition since activating
light was separately directed toward both the bottom and the top
mold members. A third wave of heat generation may also occur if the
rate of reaction at the middle portion of the lens forming
composition is different from the rates at the bottom and top
portions. Unfortunately, the resulting lens possessed waves and
distortions. It is postulated, however, that as the amounts of both
CGI-819 and NMDEA are increased, the two waves of exothermic heat
will move closer together in time, causing the optical quality of
the lens to improve, the hardness of the lens to increase, and the
rate of heat generation to be slow enough to prevent cracking and
premature release of the lens from the mold.
[0240] It is anticipated that the optimal amount of initiators may
be achieved when the total amount of both initiators are minimized
subject to the constraint of complete polymerization and production
of a rigid, aberration free lens. The relative proportions of the
photoinitiator to the co-initiator may be optimized by
experimentation. For example, an ultraviolet/visible light
absorptive lens forming composition that includes a photoinitiator
with no co-initiator may be cured. If waves and distortions are
observed in the resulting lens, a co-initiator may then be added to
the lens forming composition by increasing amounts until a lens
having the best optical properties is formed. It is anticipated
that excess co-initiator in the lens forming composition should be
avoided to inhibit problems of too rapid polymerization, yellowing
of the lens, and migration of residual, unreacted co-initiator to
the surface of the finished lens.
[0241] The following charts may be used as a guide in the selection
of an appropriate photoinitiator/co-initiator system for various
ultraviolet/visible light absorbing lens forming compositions.
1 Photoinitiator Guide Lens Forming Composition Type UV Absorptive
UV Absorptive UV Absorptive Photoinitiator Yellowness Odor Shelf
Life Photochromic Fixed Pigments Colorless CGI 819 Moderate Low
Good Good Good Good Irgacure 184 Low Low Good Good Good Good
Irgacure 651 High Low Poor Less Preferred Good Less Preferred
Irgacure 1700 High Low Fair Good Good Less Preferred Irgacure 1800
Moderate Low Good Good Good Less Preferred Irgacure 1850 Moderate
Low Good Good Good Good Darocur 1173 High Low Good Good Good Less
Preferred Darocur 4265 High Moderate Fair Good Good Less Preferred
DEAP High Strong Poor Less Preferred Less Preferred Less Preferred
KB-1 High Strong Poor Less Preferred Less Preferred Less Preferred
EsaCure KIP 100F High Strong Poor Less Preferred Less Preferred
Less Preferred Irgacure 369 High Moderate Poor Less Preferred Good
Less Preferred Irgacure 500 High Strong Poor Less Preferred Less
Preferred Less Preferred Irgacure 784 DC High Low Poor Less
Preferred Less Preferred Less Preferred Irgacure 907 High Strong
Poor Less Preferred Less Preferred Less Preferred Benzoyl peroxide
Moderate Low Poor Less Preferred Less Preferred Less Preferred
Methyl benzoyl formate Moderate Low Fair Less Preferred Less
Preferred Less Preferred EsaCure TZT High Low Poor Less Preferred
Less Preferred Less Preferred ITX High Low Poor Less Preferred Good
Good MTX High Low Poor Less Preferred Good Good CTX High Low Poor
Less Preferred Less Preferred Less Preferred TX High Low Poor Less
Preferred Less Preferred Less Preferred Xanthone High Low Poor Less
Preferred Less Preferred Less Preferred CD-1010 Low Low Poor Good
Less Preferred Less Preferred CD-1011 Low Low Poor Good Less
Preferred Less Preferred CD1012 Low Low Poor Good Good Good
[0242]
2 Co-initiator Guide Lens Forming Composition Type UV Absorptive UV
Absorptive UV Absorptive Co-initiator Photochromic Fixed Pigments
Colorless CN-383 Good CN-384 Good Good Good CN-386 Good Good Good
NMDEA Good Good Good N, NMDEA Less Preferred Less Preferred TEA
Less Preferred Less Preferred E-4-DMAB Good Less Preferred Less
Preferred E-2-DMAB Less Preferred Less Preferred
[0243] As mentioned above, exothermic reactions occur during the
curing process of the lens forming composition. The thicker
portions of the lens forming composition may generate more heat
than the thinner portions of the composition as a result of the
exothermic reactions taking place. It is believed that the speed of
reaction in the thicker sections is slower than in the thinner
sections. Thus, in a positive lens a "donut effect" may occur in
which the relatively thin outer portion of the lens forming
composition reaches its fully cured state before the relatively
thick inner portion of the lens forming composition. Conversely, in
a negative lens the relatively thin inner portion of the lens
forming composition may reach its fully cured state before the
relatively thick outer portion of the lens forming composition.
[0244] An eyeglass lens formed using the above described lens
forming composition may be applicable for use as a prescription
lens or for a non-prescription lens. Particularly, such a lens may
be used in sunglasses. Advantageously, photochromic sunglass lenses
would remain light enough in color to allow a user to see through
them clearly while at the same time prohibiting ultraviolet light
from passing through the lenses. In one embodiment, a background
dye may be added to the photochromic lens to make the lens appear
to be a dark shade of color at all times like typical
sunglasses.
[0245] 3. Variable Color Photochromic Lens Forming Compositions
[0246] Photochromic compounds tend to absorb certain wavelengths of
light strongly and change from a colorless state to a colored
state. The "colorless state" of a photochromic compound is defined
as the state in which the compound exhibits no color or only a
slight amount of color. The "colored state" of a photochromic
compound is defined as the state in which the photochromic compound
exhibits a visible light color significantly stronger than the
colorless state. A "photochromic activating light source" is
defined as any light source that produces light having a wavelength
which causes a photochromic compound to change from a colorless
state to a colored state.
[0247] "Photochromic activating light" is defined as light having a
wavelength capable of causing a photochromic compound to change
from a colorless state to a colored state. Photochromic activating
light typically includes light having a wavelength from between
about 200 nm to about 500 nm. A photochromic activating light
source may also produce other wavelengths of light, besides
photochromic activating light.
[0248] A photochromic compound which is transparent and normally
colorless will, upon exposure to a photochromic activating light
source (e.g., ultraviolet light), become colored and, therefore,
less visible light transmissive. When removed from the photochromic
activating light source, the photochromic substance tends to revert
back to its colorless state. This may be represented by the
following equation: 6
[0249] The colorless form is believed to be in equilibrium with the
colored form. The equilibrium between the colorless form and the
colored form may be controlled by the presence of photochromic
activating light (represented by h.nu.). If a photochromic compound
is exposed to a photochromic activating light source, the
equilibrium tends to shift toward the colored form of the
photochromic compound. When the photochromic activating light
source is removed, or reduced, or if the photochromic compound is
heated, the equilibrium tends to shift back toward the colorless
form of the photochromic compound. Photochromic compounds of this
type may be particularly useful in eyeglass lenses. In the absence
of photochromic activating light (e.g., when indoors) the glasses
tend to remain colorless and light transmissive. When exposed to a
photochromic activating light source (e.g., sunlight) the
photochromic compounds become activated and colored, lowering the
light transmittance of the lens. The term "activated color" is
defined as the color which an eyeglass attains when photochromic
compounds, which are included in the eyeglass lens, become
activated and colored when exposed to a photochromic activating
light source. In this manner, photochromic compounds may allow a
single lens to be used as both an indoor lens and an outdoor
lens.
[0250] When incorporated into transparent plastic lenses and
activated by exposure to a photochromic activating light source,
photochromic compounds tend to exhibit variety of colors (e.g.,
red, orange, yellow, green, blue, indigo, purple, violet, gray, and
brown), causing the lens that the photochromic compounds are
disposed within to exhibit the color of the photochromic compound.
Thus, the activated color of a photochromic eyeglass lens may be
controlled by the particular photochromic compounds dispersed
within the eyeglass lens.
[0251] It is known that the activated color of a photochromic
eyeglass lens may take on more neutral colors, such as brown or
gray, by forming the eyeglass lens with two or more photochromic
compounds present. U.S. Pat. No. 4,968,454 to Crano et. al.,
describes a composition which includes two photochromic compounds
used to form plastic lenses. The formed plastic lenses exhibit a
gray or brown color in the presence of a photochromic activating
light source. Crano et. al., describes the use of two or more
organic photochromic compounds within a plastic lens. One of the
organic photochromic compounds exhibits an absorption maximum in
the range between about 590 nm to about 700 nm in the presence of a
photochromic activating light source. The other organic
photochromic compound exhibits an absorption maximum in the range
between about 400 nm and less than about 500 nm. The ratios of the
compounds may be varied to produce lenses which exhibit a variety
of activated colors. Typically, either the ratios of the
photochromic compounds or the specific photochromic compound used
may be varied to effect a change in the activated color of the
lens.
[0252] In an embodiment, a composition which includes two or more
photochromic compounds may further include a light effector
composition to produce a lens which exhibits an activated color
which differs from an activated color produced by the photochromic
compounds without the light effector composition. The light
effector composition may include any compound which absorbs
photochromic activating light. Light effector compositions may
include photoinitiators, non-photochromic ultraviolet/visible light
absorbers (as defined above), non-photochromic dyes, and
ultraviolet light stabilizers. In this manner, the activated color
of a lens may be altered without altering the ratio and or
composition of the photochromic compounds. This may be particularly
important when large batches of lens forming compositions are
prepared before use. If photochromic lenses which exhibit a variety
of activated colors are to be produced, it is typically necessary
to create a separate lens forming composition for each colored
lens. By using a light effector composition, a single lens forming
composition may be used as a base solution to which a light
effector may be added in order to alter the activated color of the
formed lens.
[0253] The activated color of a photochromic lens may be determined
by the visible light absorption of the photochromic compounds in
their colored state. When two photochromic compounds are present,
the equilibrium between the colored and the colorless forms may be
represented by the following equations: 7
[0254] Where PC.sup.1 Colorless represents the colorless form of
the first photochromic compound; PC.sup.2 Colorless represents the
colorless form of the second photochromic compound; PC light.sup.1
represents the wavelengths of light which cause PC.sup.1 Colorless
to shift its colored state (PC.sup.1 Colored); PC light.sup.2
represents the wavelengths of light which cause PC.sup.1 Colorless
to shift to its colored state (PC.sup.2 Colored). As depicted in
FIG. 37, the wavelength of light which may activate the
photochromic compounds PC.sup.1 and PC.sup.2 may differ depending
on the chemical structure of the photochromic compounds. PC
light.sup.1, which activates the first photochromic compound
PC.sup.1, has a wavelength in the range between about
.lambda..sup.1 and .lambda..sup.2 nm. PC light.sup.2, which
activates the second photochromic compound, has a wavelength in the
range between about .lambda..sup.3 and .lambda..sup.4 nm. These
wavelength ranges may differ (as depicted in FIG. 37) or may be
substantially the same.
[0255] The addition of a light effector composition which absorbs
photochromic activating light may cause a change in the activated
color of the formed lens. The change in activated color may be
dependent on the range of photochromic activating light absorbed by
the light effector composition. The addition of light effector
compositions may have different effects on the activated color of
the lens, depending on the absorbance of the light effector
composition. In one embodiment, the light effector composition may
interfere with the photochromic activity of the first photochromic
compound (PC.sup.1). As illustrated in the equations below, the
presence of a light effector composition (Effector.sup.1) may cause
a shift in the equilibrium of PC.sup.1 while having little or no
effect on PC.sup.2. 8
[0256] Such an effect may cause an increase or decrease in the
concentration of PC.sup.1 Colored produced when the lens is exposed
to a photochromic activating light source. The equilibrium of the
other photochromic compound PC.sup.2 may not be significantly
altered. Thus, the activated color of the lens may be significantly
different than the activated color of a lens that does not include
a light effector composition (Effector.sup.1). In the above case,
if the concentration of PC.sup.1 Colored is, for example,
decreased, the activated color of the lens may become shifted
toward the activated color of PC.sup.2. For example, if the
activated color of a lens which includes PC.sup.1 only is
blue-green; with PC.sup.2 only is red; and with both PC.sup.1 and
PC.sup.2 is gray; the activated color of the lens may become more
red (e.g., shift from gray to green, yellow, orange or red) if the
concentration of PC.sup.1 Colored is decreased. It is theorized
that such an effector may have an absorbance in a region of light
similar to the PC Light.sup.1 region. The effector may interfere
with the absorption of photochromic activating light by PC.sup.1 by
competing with PC.sup.1 for the light. pC.sup.2 remains relatively
unaffected by the light effector composition since its active
photochromic activating light range differs significantly from the
photochromic activating light range for PC.sup.1. This is
graphically illustrated in FIG. 37, where Effector.sup.1 is
depicted as having an absorption within the PC.sup.1 Light.sup.1
region. By competing with PC.sup.1 for the photochromic activating
light, Effector.sup.1 may cause a decrease in the amount of
PC.sup.1 Colored being produced.
[0257] In another embodiment, a light effector may interact with
both photochromic compounds, altering the amount of PC.sup.1
colored and PC.sup.2 colored produced. The equation below depicts
this case: 9
[0258] Such an effect may cause an increase or decrease in the
concentration of both PC.sup.1 Colored and PC.sup.2 Colored
produced when the lens is exposed to a photochromic activating
light source. This change in the equilibrium may cause the
activated color of the lens to be significantly different than the
activated color of a lens that does not include a light effector
composition. In the above case if the concentration of PC.sup.1
Colored is, for example, decreased and the concentration of
PC.sup.2 Colored is, for example, increased, the activated color of
the lens may become shifted toward the activated color of PC.sup.2
colored. For example, if the activated color of a lens which
includes PC.sup.1 only is blue-green; with PC.sup.2 only is red;
and with both PC.sup.1 and PC.sup.2 is gray; the activated color of
the lens may become more red in the presence of the light effector
composition. The direction of the shift may depend on which
photochromic compound is effected more by the presence of the light
effector composition. It is theorized that the light effector
composition (Effector.sup.2) may have an absorbance in a region
that significantly overlaps the PC Light.sup.1 and PC Light.sup.2
regions. The light effector composition interferes with the
absorption of photochromic activating light by both PC.sup.1 and
PC.sup.2 by competing with the compounds for light having the
appropriate activating wavelength. If the light effector interferes
with the photochromic light absorption of PC.sup.1 to a greater
extent then PC.sup.2 the color may shift toward PC.sup.2.
Alternatively, the activated color may shift toward PC.sup.1 if the
light effector absorption interferes with the absorption of
photochromic light by PC.sup.2 to a greater extent than PC.sup.1.
In FIG. 37, Effector.sup.1 is depicted as having an absorption
within both the PC.sup.1 and PC.sup.2 absorption region.
[0259] In another embodiment, a light effector composition may
interfere with the photochromic activity of the second photochromic
compound (PC.sup.2). As illustrated in the equations below, the
presence of a light effector composition (Effector.sup.1) may cause
a shift in the equilibrium of PC.sup.2 while having little or no
effect on PC.sup.1. 10
[0260] Such an effect may cause an increase or decrease in the
concentration of PC.sup.2 Colored produced when the lens is exposed
to a photochromic activating light source. The equilibrium of the
other photochromic compound PC.sup.1 may not be significantly
altered. In the above case, if the concentration of PC.sup.2
Colored is, for example, decreased, the activated color of the lens
may become shifted toward the activated color of PC.sup.1. For
example, if the activated color of a lens which includes PC.sup.1
only is blue-green; with PC.sup.2 only is red; and with both
PC.sup.1 and PC.sup.2 is gray; the activated color of the lens may
become more blue (e.g., shift from gray to green, green-blue, or
blue) if the concentration of PC.sup.1 Colored is decreased. It is
theorized that such an effector may have an absorbance in a region
of light similar to the PC Light.sup.2 region. The effector may
interfere with the absorption of photochromic activating light by
PC.sup.2 by competing with PC.sup.2 for the light. PC.sup.1 remains
relatively unaffected by the light effector composition since its
active photochromic activating light range differs significantly
from the photochromic activating light range for PC.sup.2. This is
graphically illustrated in FIG. 37, where Effector.sup.1 is
depicted as having an absorption within the PC Light.sup.2 region.
By competing with PC.sup.2 for the photochromic activating light,
Effector may cause a decrease in the amount of PC.sup.2 Colored
being produced.
[0261] While the above examples relate to the use of two
photochromic compounds, light effector compositions may be used to
effect the activated color of a lens which includes more than two
photochromic compounds. The color changes for these systems may be
more varied than described above, due to the variety of ranges in
which the photochromic compounds absorb the photochromic activating
light. For example, if three photochromic compounds are present,
with activated colors of red, blue and green, a variety of colors
may be produced depending on the interaction of the light effector
composition with the photochromic activating light. The light
effector may absorb the photochromic activating light such that the
concentration of the colored form of two of the three photochromic
compounds is reduced. The formed lens would than exhibit a color
which is closest to the activated color of the non-effected
photochromic compound. In the above example, a lens with an
activated color of substantially blue, red, or green may be
obtained by the addition of a light effector. Alternatively, the
light effector compound may reduce the concentration of the colored
form of only one of the photochromic compounds. In the above
example, the activated color of the lens may become yellow (from
red and green, with reduced amount of blue), green-blue (from green
and blue, with reduced amount of red) or purple (from red and blue,
with reduced amount of green). A full spectrum of activated colors
may be produced by changing the composition of the light effector
composition, without having to alter the ratio or chemical
composition of the photochromic compounds.
[0262] It should also be understood that the light effector
composition may include one or more light effector compounds. The
use of multiple light effector compounds may allow the activated
color of the lens to be further altered.
[0263] In another embodiment, a photochromic activating light dye
may be added to the lens forming composition to alter the activated
color of a lens. The dye preferably exhibits a dye color when
exposed to visible light. The dye color, however, is not
significantly altered in the presence or absence of photochromic
activating light. When mixed with a lens forming composition which
includes at least one photochromic compound the dye may alter the
activated color of the lens, as well as the color of the lens in
the absence of photochromic activating light.
[0264] In one embodiment, the dye may interfere with the
photochromic activity of a photochromic compound. The activated
color of a lens formed without the dye would preferably change when
the dye is added to the lens. The activated color of the lens may
vary depending on the type of dye chosen. In one embodiment, the
dye may interfere with the absorbance of photochromic activating
light by the photochromic compound. This interference may lead to a
reduced concentration of the colored form of the photochromic
compound. The activated color of the lens may be a mixture of the
dye color and the photochromic color. For example, if a dye is blue
and the photochromic compound is red, the lens may take on a purple
color (i.e., a combination of the two colors).
[0265] It should be understood that the activated color of the lens
may be significantly different the an activated color of a lens in
which the photochromic compound is unaffected by the dye. When the
absorption of photochromic activating light by the photochromic
compound is unaffected by the dye, the intensity of the colored
form of the photochromic compound may not be reduced. Thus, the
activated color of the lens is formed from a mixture of the dye
color and the full intensity of the colored form of the
photochromic compound. When the dye interferes with the
photochromic activating light absorbance of the photochromic
compound, the color of the lens is based on a combination of the
dye and the reduced intensity of the colored form of the
photochromic compound. The reduced intensity of the colored form of
the photochromic compound may cause the lens to have a color that
is substantially different from the color produced when the
unaffected colored form of the photochromic compound is mixed with
the dye.
[0266] While described above for one photochromic compound, it
should be understood that the dye may have an effect on mixtures of
photochromic compounds such that a full spectrum of colors may be
achieved. The selection of the appropriate dye based on the
photochromic compounds present allows the color of the lenses to be
altered without changing the ratio of the photochromic
compounds.
[0267] In an embodiment, a lens forming composition includes at
least two photochromic compounds. The photochromic compounds are
preferably chosen to that have an activated color at opposite ends
of the visible spectrum (e.g., blue and red). In one embodiment,
the photochromic compounds may be Reversacol Berry Red (giving a
red activated color) and Reversacol Sea Green (giving a blue-green
color). The appropriate mixture of these two photochromic compounds
gives the formed lens an activated color of gray. The addition of
effectors may cause the formed lens to have a wide variety of
activated colors (e.g. red, orange, yellow, yellow green, green,
aqua-green, blue, violet, purple, or brown). These changes in color
may be accomplished without altering the ratio between the first
and second photochromic compounds.
[0268] A lens forming composition based on the PRO-629 mixture of
monomers may be used to develop photochromic lenses (See the
section entitled "Lens Forming Compositions Including
Ultraviolet/Visible Light Absorbing Materials"). The remainder of
the lens forming composition preferably includes photoinitiators,
co-initiators, photochromic compounds. The amount of photochromic
pigments present in the lens forming composition may widely range
from about 1 ppm by weight to 5% by weight. In preferred
compositions, the photochromic pigments are present in ranges from
about 30 ppm to 2000 ppm. In the more preferred compositions, the
photochromic pigments are present in ranges from about 150 ppm to
1000 ppm. The concentration may be adjusted depending upon the
thickness of the lens being produced to obtain optimal visible
light absorption characteristics.
[0269] To alter the color of the active lens formed from this base
composition a light effector composition may be added to the base
composition. The light effector composition preferably includes one
or more light effectors. The light effector composition may be a
pure composition of one or more light effectors. Alternatively, the
light effectors may be diluted in a solution which has a
composition similar to the base composition. The light effectors
preferably include photochromic activating light absorbing
compounds. More preferably, non-photochromic photochromic
activating light absorbing compounds are added to alter the
activated color of the formed lens. Examples of light effectors
include polymerization inhibitors (e.g., MEHQ), photoinitiators,
co-initiators, fixed pigments and dyes, and hindered amine light
stabilizers. All of these classes of compounds are described in
greater detail in the previous section. After the light effector
composition has been added, the amount of light effectors present
in the lens forming composition may widely range from about 1 ppm
by weight to 5% by weight. In preferred compositions, the light
effectors are present in ranges from about 30 ppm to 2000 ppm. In
the more preferred compositions, the light effectors are present in
ranges from about 150 ppm to 1000 ppm. The concentration may be
adjusted depending upon the thickness of the lens being produced to
obtain optimal visible light absorption characteristics.
[0270] An advantage of the described composition is that the
activated color of a lens may be altered without altering the ratio
and or composition of the photochromic compounds. By using a light
effector composition, a single lens forming composition may be used
as a base composition to which a light effector composition may be
added in order to alter the activated color of the formed lens. The
base composition may be supplied for use in the production of a
variety of photochromic lenses. Along with the base composition, a
light effector composition, which includes one or more light
effector compounds, may be included with the base composition. The
light effector composition may be added to the base composition to
alter the activated color of the formed lenses. In this manner, a
single stock photochromic lens forming composition may be used to
create photochromic lenses having a variety of activated
colors.
[0271] In another embodiment, the base composition and at least two
light effector compositions may be package together as a kit. The
addition of the first light effector composition may alter the
activated color of the formed lenses to produce a first color. The
addition of the second light effector composition may alter the
activated color of the formed lenses to produce a second color.
Additional light effectors compositions may also be included with
the kit. The kit may allow a user to produce lens forming
compositions which may be used to produce lens having a variety of
activated colors by the addition of the appropriate light effector
composition to the base composition.
[0272] 4. Mid-Index Lens Forming Composition
[0273] In an embodiment, an ophthalmic eyeglass lens may be made
from a lens forming composition comprising a monomer composition
and a photoinitiator composition.
[0274] The monomer composition preferably includes an aromatic
containing polyethylenic polyether functional monomer. In an
embodiment, the polyether employed is an ethylene oxide derived
polyether, propylene oxide derived polyether, or mixtures thereof.
Preferably, the polyether is an ethylene oxide derived polyether.
The aromatic polyether polyethylenic functional monomer preferably
has the general structure (V), depicted below where each R.sub.2 is
a polymerizable unsaturated group, m and n are independently 1 or
2, and the average values of j and k are each independently in the
range of from about 1 to about 20. Common polymerizable unsaturated
groups include vinyl, allyl, allyl carbonate, methacrylyl, acrylyl,
methacrylate, and acrylate.
R.sub.2--[CH.sub.2--(CH.sub.2).sub.m--O].sub.j-A[-[O--(CH.sub.2).sub.n--CH-
.sub.2].sub.k--R.sub.2
[0275] A.sub.1 is the divalent radical derived from a dihydroxy
aromatic-containing material. A subclass of the divalent radical
A.sub.1 which is of particular usefulness is represented by formula
(II): 11
[0276] in which each R.sub.1 is independently alkyl containing from
1 to about 4 carbon atoms, phenyl, or halo; the average value of
each (a) is independently in the range of from 0 to 4; each Q is
independently oxy, sulfonyl, alkanediyl having from 2 to about 4
carbon atoms, or alkylidene having from 1 to about 4 carbon atoms;
and the average value of n is in the range of from 0 to about 3.
Preferably Q is methylethylidene, viz., isopropylidene.
[0277] Preferably the value of n is zero, in which case A.sub.1 is
represented by formula (III): 12
[0278] in which each R.sub.1, each a, and Q are as discussed with
respect to Formula II. Preferably the two free bonds are both in
the ortho or para positions. The para positions are especially
preferred.
[0279] In an embodiment, when para, para-bisphenols are chain
extended with ethylene oxide, the central portion of the aromatic
containing polyethylenic polyether functional monomer may be
represented by the formula: 13
[0280] where each R.sub.1, each a, and Q are as discussed with
respect to Formula II, and the average values of j and k are each
independently in the range of from about 1 to about 20.
[0281] In another embodiment, the polyethylenic functional monomer
is an aromatic polyether polyethylenic functional monomer
containing at least one group selected from acrylyl or methacrylyl.
Preferably the aromatic polyether polyethylenic functional monomer
containing at least one group selected from acrylate and
methacrylate has the general structure (VI), depicted below where
R.sub.0 is hydrogen or methyl, where each R.sub.1, each a, and Q
are as discussed with respect to Formula II, where the values of j
and k are each independently in the range of from about 1 to about
20, and where R.sub.2 is a polymerizable unsaturated group (e.g.,
vinyl, allyl, allyl carbonate, methacrylyl, acrylyl, methacrylate,
or acrylate). 14
[0282] In one embodiment, the aromatic containing polyether
polyethylenic functional monomer is preferably an ethoxylated
bisphenol A di(meth)acrylate. Ethoxylated bisphenol A
di(meth)acrylates have the general structure depicted below where
each R.sub.0 is independently hydrogen or methyl, each R.sub.1,
each a, and Q are as discussed with respect to Formula II, and the
values of j and k are each independently in the range of from about
1 to about 20. 15
[0283] Preferred ethoxylated bisphenol A dimethacrylates include
ethoxylated 2 bisphenol A diacrylate (where j+k=2, and R.sub.0 is
H), ethoxylated 2 bisphenol A dimethacrylate (where j+k=2, and
R.sub.0 is Me), ethoxylated 3 bisphenol A diacrylate (where j+k=3,
and R.sub.0 is H), ethoxylated 4 bisphenol A diacrylate (where
j+k=4, and R.sub.0 is H), ethoxylated 4 bisphenol A dimethacrylate
(where j+k=4, and R.sub.0 is Me), ethoxylated 6 bisphenol A
dimethacrylate (where j+k=6, and R.sub.0 is Me), ethoxylated 8
bisphenol A dimethacrylate (where j+k=8, and R.sub.0 is Me),
ethoxylated 10 bisphenol A diacrylate (where j+k=10, and R.sub.0 is
H), ethoxylated 10 bisphenol A dimethacrylate (where j+k=10, and
R.sub.0 is Me), ethoxylated 30 bisphenol A diacrylate (where
j+k=30, and R.sub.0 is H), ethoxylated 30 bisphenol A
dimethacrylate (where j+k=30, and R.sub.0 is Me). These compounds
are commercially available from Sartomer Company under the trade
names PRO-631, SR-348, SR-349, SR-601, CD-540, CD-541, CD-542,
SR-602, SR480, SR-9038, and SR-9036 respectively. Other ethoxylated
bisphenol A dimethacrylates include ethoxylated 3 bisphenol A
dimethacrylate (where j+k=3, and R.sub.0 is Me), ethoxylated 6
bisphenol A diacrylate (where j+k=30, and R.sub.0 is H), and
ethoxylated 8 bisphenol A diacrylate (where j+k=30, and R.sub.0 is
H). In all of the above described compounds Q is
C(CH.sub.3).sub.2.
[0284] The monomer composition preferably may also include a
polyethylenic functional monomer. Polyethylenic functional monomers
are defined herein as organic molecules which include two or more
polymerizable unsaturated groups. Common polymerizable unsaturated
groups include vinyl, allyl, allyl carbonate, methacrylyl, acrylyl,
methacrylate, and acrylate. Preferably, the polyethylenic
functional monomers have the general formula (VII) or (VIII)
depicted below, where each R.sub.0 is independently hydrogen, halo,
or a C.sub.1-C.sub.4 alkyl group and where A.sub.1 is as described
above. It should be understood that while general structures (VII)
and (VIII) are depicted as having only two polymerizable
unsaturated groups, polyethylenic functional monomers having three
(e.g., tri(meth)acrylates), four (e g., tetra(meth)acrylates), five
(e.g., penta(meth)acrylates), six (e.g., hexa(meth)acrylates) or
more groups may be used. 16
[0285] Preferred polyethylenic functional monomers which may be
combined with an aromatic containing polyethylenic polyether
functional monomer to form the monomer composition include, but are
not limited to, ethoxylated 2 bisphenol A dimethacrylate,
tris(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated 10
bisphenol A dimethacrylate, ethoxylated 4 bisphenol A
dimethacrylate, dipentaerythritol pentaacrylate, 1,6-hexanediol
dimethacrylate, isobornyl acrylate, pentaerythritol triacrylate,
ethoxylated 6 trimethylolpropane triacrylate, and bisphenol A bis
allyl carbonate.
[0286] According to one embodiment, the liquid lens forming
composition includes ethoxylated 4 bisphenol A dimethacrylate.
Ethoxylated 4 bisphenol A dimethacrylate monomer, when cured to
form an eyeglass lens, typically produces lenses that have a higher
index of refraction than comparable lenses produced using DEG-BAC.
Lenses formed from such a mid-index lens forming composition which
includes ethoxylated 4 bisphenol A dimethacrylate may have an index
of refraction of about 1.56 compared to the PRO-629 compositions
(previously described) which tend to have an index of refraction of
about 1.51. A lens made from a higher index of refraction polymer
may be thinner than a lens made from a lower index of refraction
polymer because the differences in the radii of curvature between
the front and back surface of the lens do not have to be as great
to produce a lens of a desired focal power. Lenses formed from a
lens forming composition which includes ethoxylated 4 bisphenol A
dimethacrylate may also be more rigid than lenses formed from
PRO-629 based compositions.
[0287] The monomer composition may include additional monomers,
which, when combined with ethoxylated 4 bisphenol A dimethacrylate,
may modify the properties of the formed eyeglass lens and/or the
lens forming composition. Tris(2-hydroxyethyl)isocyanurate
triacrylate, available from Sartomer under the trade name SR-368,
is a triacrylate monomer that may be included in the composition to
provide improved clarity, high temperature rigidity, and impact
resistance properties to the finished lens. Ethoxylated 10
bisphenol A dimethacrylate, available from Sartomer under the trade
name SR-480, is a diacrylate monomer that may be included in the
composition to provide impact resistance properties to the finished
lens. Ethoxylated 2 bisphenol A dimethacrylate, available from
Sartomer under the trade name SR-348, is a diacrylate monomer that
may be included in the composition to provide tintability
properties to the finished lens. Dipentaerythritol pentaacrylate,
available from Sartomer under the trade name SR-399, is a
pentaacrylate monomer that may be included in the composition to
provide abrasion resistance properties to the finished lens.
1,6-hexanediol dimethacrylate, available from Sartomer under the
trade name SR-239, is a diacrylate monomer that may be included in
the composition to reduce the viscosity of the lens forming
composition. Isobornyl acrylate, available from Sartomer under the
trade name SR-506, is an acrylate monomer that may be included in
the composition to reduce the viscosity of the lens forming
composition and enhance tinting characteristics. Bisphenol A bis
allyl carbonate may be included in the composition to control the
rate of reaction during cure and also improve the shelf life of the
lens forming composition. Pentaerythritol triacrylate, available
from Sartomer under the trade name SR-444, is a triacrylate monomer
that may be included in the composition to promote better adhesion
of the lens forming composition to the molds during curing.
Ethoxylated 6 trimethylolpropane triacrylate, available from
Sartomer under the trade name SR-454, may also be added.
[0288] Photoinitiators which may be used in the lens forming
composition have been described in previous sections. In one
embodiment, the photoinitiator composition preferably includes
bis(2,6-dimethoxybenzoyl)-- (2,4,4-trimethylphenyl)phosphine oxide
(IRG-819) which is commercially available from Ciba Additives under
the trade name of Irgacure 819. The amount of Irgacure 819 present
in a lens forming composition preferably ranges from about 30 ppm
by weight to about 2000 ppm by weight. In another embodiment, the
photoinitiator composition may include a mixture of photoinitiator.
Preferably, a mixture of Irgacure 819 and 1-hydroxycyclohexylphenyl
ketone, commercially available from Ciba Additives under the trade
name of Irgacure 184 (IRG-184), is used. Preferably, the total
amount of photoinitiators in the lens forming composition ranges
from about 50 ppm to about 1000 ppm.
[0289] In another embodiment, an ophthalmic eyeglass lens may be
made from lens forming composition comprising a monomer
composition, a photoinitiator composition, and a co-initiator
composition. The lens forming composition, in liquid form, is
preferably placed in a mold cavity defined by a first mold member
and a second mold member. It is believed that activating light
which is directed toward the mold members to activate the
photoinitiator composition causes the photoinitiator to form a
polymer chain radical. The co-initiator may react with a fragment
or an active species of either the photoinitiator or the polymer
chain radical to produce a monomer initiating species. The polymer
chain radical and the monomer initiating species may react with the
monomer to cause polymerization of the lens forming
composition.
[0290] The monomer composition preferably includes an aromatic
containing polyethylenic polyether functional monomer having a
structure as shown above. Preferably, the polyethylenic functional
monomer is an aromatic polyether polyethylenic functional monomer
containing at least one group selected from acrylyl or
methacrylyl.
[0291] More preferably, the polyethylenic functional monomer is an
ethoxylated bisphenol A di(meth)acrylate The monomer composition
may include a mixture of polyethylenic functional monomers, as
described above. The photoinitiators which may, be present in the
lens forming composition have been described above.
[0292] The lens forming composition preferably includes a
co-initiator composition. The co-initiator composition preferably
includes amine co-initiators. Amines are defined herein as
compounds of nitrogen formally derived from ammonia (NH.sub.3) by
replacement of the hydrogens of ammonia with organic substituents.
Co-initiators include acrylyl amine co-initiators commercially
available from Sartomer Company under the trade names of CN-381,
CN-383, CN-384, and CN-386, where these co-initiators are
monoacrylyl amines, diacrylyl amines, or mixtures thereof. Other
co-initiators include ethanolamines. Examples of ethanolamines
include but are not limited to N-methyldiethanolamine (NMDEA) and
triethanolamine (TEA) both commercially available from Aldrich
Chemicals. Aromatic amines (e.g., aniline derivatives) may also be
used as co-initiators. Example of aromatic amines include, but are
not limited to, ethyl-4-dimethylaminobenzoate (E-4-DMAB),
ethyl-2-dimethylaminobenzoate (E-2-DMAB),
n-butoxyethyl-4-dimethylaminobe- nzoate,
p-dimethylaminobenzaldehyde, N,N-dimethyl-p-toluidine, and
octyl-p-(dimethylamino)benzoate commercially available from Aldrich
Chemicals or The First Chemical Group of Pascagoula, Miss.
[0293] Preferably, acrylated amines are included in the
co-initiator composition. Acrylyl amines may have the general
structures depicted in FIG. 39, where R.sub.0 is hydrogen or
methyl, n and m are 1 to 20, preferably 1-4, and R.sub.1 and
R.sub.2 are independently alkyl containing from 1 to about 4 carbon
atoms or phenyl. Monoacrylyl amines may include at least one
acrylyl or methacrylyl group (see compounds (A) and (B) in FIG.
39). Diacrylyl amines may include two acrylyl, two methacrylyl, or
a mixture of acrylyl or methacrylyl groups (see compounds (C) and
(D) in FIG. 39). Acrylyl amines are commercially available from
Sartomer Company under the trade names of CN-381, CN-383, CN-384,
and CN-386, where these co-initiators are monoacrylyl amines,
diacrylyl amines, or mixtures thereof. Other acrylyl amines include
dimethylaminoethyl methacrylate and dimethylaminoethyl acrylate
both commercially available from Aldrich. In one embodiment, the
co-initiator composition preferably includes a mixture of CN-384
and CN-386. Preferably, the total amount of co-initiators in the
lens forming composition ranges from about 50 ppm to about 7% by
weight.
[0294] An advantage to lens forming compositions which include a
co-initiator is that less photoinitiator may be used to initiate
curing of the lens forming composition. Typically, plastic lenses
are formed from a lens forming composition which includes a
photoinitiator and a monomer. To improve the hardness of the formed
lenses the concentration of photoinitiator may be increased.
Increasing the concentration of photoinitiator, however, may cause
increased yellowing of the formed lens, as has been described
previously. To offset this increase in yellowing, a permanent dye
may be added to the lens forming composition. As the amount of
yellowing is increased the amount of dye added may also be
increased. Increasing the concentration of the dye may cause the
light transmissibility of the lens to decrease.
[0295] A lens forming composition that includes a co-initiator may
be used to reduce the amount of photoinitiator used. To improve the
hardness of the formed lenses a mixture of photoinitiator and
co-initiator may be used to initiate curing of the monomer. The
above-described co-initiators typically do not significantly
contribute to the yellowing of the formed lens. By adding
co-initiators to the lens forming composition, the amount of
photoinitiator may be reduced. Reducing the amount of
photoinitiator may decrease the amount of yellowing in the formed
lens. This allows the amount of dyes added to the lens forming
composition to be reduced and light transmissibility of the formed
lens may be improved without sacrificing the rigidity of the
lens.
[0296] The lens forming composition may also include activating
light absorbing compounds. These compounds may absorb at least a
portion of the activating light which is directed toward the lens
forming composition during curing. One example of activating light
absorbing compounds are photochromic compounds. Photochromic
compounds which may be added to the lens forming composition have
been previously described. Preferably, the total amount of
photochromic compounds in the lens forming composition ranges from
about 1 ppm to about 1000 ppm. Examples of photochromic compounds
which may be used in the lens forming composition include, but are
not limited to Corn Yellow, Berry Red, Sea Green, Plum Red,
Variacrol Yellow, Palatinate Purple, CH-94, Variacrol Blue D,
Oxford Blue and CH-266. Preferably, a mixture of these compounds is
used. Variacrol Yellow is a napthopyran material, commercially
available from Great Lakes Chemical in West Lafayette, Ind. Corn
Yellow and Berry Red are napthopyrans and Sea Green, Plum Red and
Palatinate Purple are spironaphthoxazine materials commercially
available from Keystone Aniline Corporation in Chicago, Ill.
Variacrol Blue D and Oxford Blue are spironaphthoxazine materials,
commercially available from Great Lakes Chemical in West Lafayette,
Ind. CH-94 and CH-266 are benzopyran materials, commercially
available from Chroma Chemicals in Dayton, Ohio. The composition of
a Photochromic Dye Mixture which may be added to the lens forming
composition is described in the table below.
3 Photochromic Dye Mixture Corn Yellow 22.3% Berry Red 19.7% Sea
Green 14.8% Plum Red 14.0% Variacrol Yellow 9.7% Palatinate Purple
7.6% CH-94 4.0% Variacrol Blue D 3.7% Oxford Blue 2.6% CH-266
1.6%
[0297] The lens forming composition may also other activating light
absorbing compounds such as UV stabilizers, UV absorbers, and dyes.
UV stabilizers, such as Tinuvin 770 may be added to reduce the rate
of degradation of the formed lens caused by exposure to ultraviolet
light. UV absorbers, such as
2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbut- yl)phenol, may
be added to the composition to provide UV blocking characteristics
to the formed lens. Small amounts of dyes, such as Thermoplast Blue
684 and Thermoplast Red from BASF may be added to the lens forming
composition to counteract yellowing. These classes of compounds
have been described in greater detail in previous sections.
[0298] In an embodiment, a UV absorbing composition may be added to
the lens forming composition. The UV absorbing composition
preferably includes a photoinitiator and a UV absorber.
Photoinitiators and UV absorbers have been described in greater
detail in previous sections. Typically, the concentration of UV
absorber in the lens forming composition required to achieve
desirable UV blocking characteristics is in the range from about
0.1 to about 0.25%/by weight. For example,
2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol may be
added to the lens forming composition as a UV absorber at a
concentration of about 0.17%.
[0299] By mixing a photoinitiator with a UV absorbing compound the
combined concentration of the photoinitiator and the UV absorber
required to achieve the desired UV blocking characteristics in the
formed lens may be lower than the concentration of UV absorber
required if used alone. For example,
2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol may be
added to the lens forming composition as a UV absorber at a
concentration of about 0.17% to achieve the desired UV blocking
characteristics for the formed lens. Alternatively, a UV absorbing
composition may be formed by a combination of
2-(2H-benzotriazol-2-yl)-4-- (1,1,3,3,-tetramethylbutyl)phenol with
the photoinitiator 2-isopropyl-thioxanthone (ITX), commercially
available from Aceto Chemical in Flushing, N.Y. To achieve similar
UV blocking characteristics in the formed lens, significantly less
of the UV absorbing composition may be added to the lens forming
composition, compared to the amount of UV absorber used by itself.
For example, 2-(2H-benzotriazol-2-yl)-4-(1,1,-
3,3,-tetramethylbutyl)phenol at a concentration of about 700 ppm,
with respect to the lens forming composition, along with 150 ppm of
the photoinitiator 2-isopropyl-thioxanthone (2-ITX) may be used to
provide UV blocking characteristics. Thus, a significant reduction,
(e.g., from 0.15% down to less than about 1000 ppm), in the
concentration of UV absorber may be achieved, without a reduction
in the UV blocking ability of the subsequently formed lens. An
advantage of lowering the amount of UV absorbing compounds present
in the lens forming composition is that the solubility of the
various components of the composition may be improved.
[0300] The tables below list some examples of mid-index lens
forming compositions. The UV absorber is
2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tet- ramethylbutyl)phenol.
4 Ingredient Formula 1 Formula 2 Formula 3 Formula 4 Formula 5
Formula 6 Irgacure 819 694.2 ppm 486 ppm 480 ppm 382 ppm 375 ppm
414 ppm Irgacure 184 CN 384 0.962% 0.674% 0.757% 0.62% 0.61% 0.66%
CN386 0.962% 0.674% 0.757% 0.62% 0.61% 0.66% SR-348 97.98% 68.65%
98.2% 81.2% 79.6% 86.4% SR-368 SR-480 29.95% CD-540 SR-399 SR-239
2.0% 2.08% SR-506 CR-73 17.2% 16.9% 10.0% PRO-629 Tinuvin 770 290
ppm UV Absorber 0.173% Thermoplast 0.534 ppm 0.374 ppm 0.6 ppm 0.5
ppm 4.5 ppm 4.58 ppm Blue Thermoplast 0.019 ppm 0.0133 ppm 0.015
ppm 0.012 ppm 0.58 ppm 0.58 ppm Red Mineral Oil 136 ppm 65 ppm
Photochromic 470 ppm 507 ppm Dye Mixrure Ingredient Formula 7
Formula 8 Formula 9 Formula 10 Formula 11 Formula 12 Irgacure 819
531.2 ppm 462 ppm 565.9 ppm 226 ppm 443 ppm 294 ppm Irgacure 184
18.7 ppm 144 ppm CN 384 0.77% 0.887% 0.78% 0.40% 0.61% CN 386 0.77%
0.887% 0.78% 0.53% 0.61% SR-348 72.4% 70.36% 58.20% 41.5% 88.70%
SR-368 24.1% 23.87% 21.4% 7.0% SR-480 CD-540 18.7% 0.74% 97.76%
SR-399 46.8% SR-239 1.86% 3.65% 20.1% 2.00% SR-506 10.0% CR-73
20.1% 2.9% PRO-629 0.05% Tinuvin 770 UV Absorber Thermoplast 0.567
ppm 3.62 ppm 0.70 ppm 0.255 ppm 0.6 ppm 4.3 ppm Blue Thermoplast
0.0147 ppm 0.576 ppm 0.014 ppm 0.006 ppm 0.028 ppm 0.24 ppm Red
Photochromic 450 ppm Dye Mixture Ingredient Formula 13 Formula 14
Formula 15 Formula 16 Formula 17 Formula 18 Irgacure 819 760 ppm
620 ppm 289 ppm 105 ppm 343 ppm Irgacure 184 CN 384 0.73% 0.34%
0.475% CN 386 0.73% 0.34% 1.00% 0.70% 0.475% 2-ITX 188 ppm 141 ppm
SR-348 89.00% 92.00% 98.90% SR-368 SR-480 CD-540 97.57% 96.20%
99.28% 0.34% SR-399 SR-239 2.30% 2.30% 0.01% SR-506 SR-444 SR-454
10.00% 6.9% CR-73 PRO-629 Tinuvin 770 UV Absorber 785 ppm
Thermoplast 4.9 ppm 5.1 ppm 0.508 ppm 0.35 ppm 0.69 ppm Blue
Thermoplast 0.276 ppm 0.285 ppm 0.022 ppm 0.002 ppm 0.034 ppm Red
Dioctyl- 125 ppm phthalate Butyl stearate Photochromic 499 ppm Dye
Mixture Ingredient Formula 19 Fonnula 20 Formula 21 Formula 22
Formula 23 Formula 24 Irgacure 819 490 ppm 635 ppm 610 ppm 735 ppm
320 ppm 600 ppm Irgacure 184 CN 384 0.680% 0.746% 0.705% 0.60% CN
386 0.680% 0.746% 0.705% 0.60% 2-ITX SR-348 69.30% 68.60% SR-368
74.0% 22.10% SR-480 CD-540 98.45% 92.60% 98.50% 1.0% 1.97% SR-399
SR-239 0.01% 3.86% 0.16% SR-506 0.10% SR-444 29.30% SR-454 25.0%
7.40% CR-73 PRO-629 0.007% 2.06% Tinuvin 770 UV Absorber
Thermoplast 0.37ppm 0.507 ppm 3.07 ppm 4.3 ppm 0.15 ppm 0.29 ppm
Blue Thermoplast 0.013 ppm 0.0126 ppm 0.336 ppm 0.41 ppm 0.006 ppm
0.012 ppm Red Dioctyl- pthalate Butyl stearate Photochromic 442 ppm
497 ppm Dye Mixture Ingredient Formula 25 Formula 26 Formula 27
Formula 28 Formula 29 Formula 30 Formula 31 Irgacure 819 650 ppm
464 ppm 557 ppm 448 ppm 460 ppm Irgacure 184 300 ppm CN 384 0.650%
0.70% CN 386 0.650% 0.70% 2-ITX 600 ppm 120 ppm SR-348 39.10%
SR-368 13.00% 19.60% 20.70% SR-480 10.70% CD-540 88.96% 41.90%
1.60% 1.30% 99.94% 99.96% SR-399 SR-239 SR-506 98.30% 79.00% 67.24%
SR-444 9.70% 4.60% SR-454 CR-73 PRO-629 Tinuvin 770 UV Absorber
Thermoplast 0.566 ppm 0.52 ppm 0.24 ppm 0.19 ppm 0.467 ppm Blue
Thermoplast 0.02 ppm 0.013 ppm 0.01 ppm 0.008 ppm 0.024 ppm Red
Dioctyl- phthalate Butyt stearate 75 ppm 35 ppm Photochromic Dye
Mixture
[0301] In one embodiment, plastic lenses may be formed by disposing
a mid-index lens forming composition into the mold cavity of a mold
assembly and irradiating the mold assembly with activating light.
Coating materials may be applied to the mold members prior to
filling the mold cavity with the lens forming composition.
[0302] After filing the mold cavity of the mold assembly the mold
assembly is preferably placed in the lens curing unit and subjected
to activating light. Preferably, actinic light is used to irradiate
the mold assembly. A clear polycarbonate plate may be placed
between the mold assembly and the activating light source. The
polycarbonate plate preferably isolates the mold assembly from the
lamp chamber, thus preventing airflow from the lamp cooling fans
from interacting with the mold assemblies. The activating light
source may be configured to deliver from about 0.1 to about 10
milliwatts/cm2 to at least one non-casting face, preferably both
non-casting faces, of the mold assembly. Depending on the
components of the lens forming composition used the intensity of
activating light used may be <1 milliwatt/cm.sup.2. The
intensity of incident light at the plane of the lens curing unit
drawer is measured using an International Light IL-1400 radiometer
equipped with an XRL140A detector head. This particular radiometer
preferably has a peak detection wavelength at about 400 nm, with a
detection range from about 310 nm to about 495 nm. The
International Light IL-1400 radiometer and the XRL140A detector
head are both commercially available International Light,
Incorporated of Newburyport, Mass.
[0303] After the mold assembly is placed within the lens curing
unit, the mold assemblies are preferably irradiated with activating
light continuously for 30 seconds to thirty minutes, more
preferably from one minute to five minutes. Preferably, the mold
assemblies irradiated in the absence of a cooling air stream. After
irradiation, the mold assemblies were removed from the lens curing
unit and the formed lens demolded. The lenses may be subjected to a
post-cure treatment in the post-cure unit.
[0304] In general, it was found that the use of a photoinitiator
(e.g., IRG-819 and IRG-184) in the lens forming composition
produces lenses with better characteristics than lens formed using
a co-initiator only. For example, formula 15, described in the
above table, includes a monomer composition (a mixture of SR-348
and SR-454) and a co-initiator (CN-386). When this lens forming
composition was exposed to activating light for 15 min. there was
no significant reaction or gel formation. It is believed that the
co-initiator requires an initiating species in order to catalyze
curing of the monomer composition. Typically this initiating
species is produced from the reaction of the photoinitiator with
activating light.
[0305] A variety of photoinitiators and photoinitiators combined
with co-initiators may be used to initiate polymerization of the
monomer composition. One initiator system which may be used
includes photoinitiators IRG-819 and 2-ITX and a co-initiator, see
Formulas 17-18. Such a system is highly efficient at initiating
polymerization reactions. The efficiency of a polymerization
catalyst is a measurement of the amount of photoinitiator required
to initiate a polymerization reaction. A relatively small amount of
an efficient photoinitiator may be required to catalyze a
polymerization reaction, whereas a greater amount of a less
efficient photoinitiator may be required to catalyze the
polymerization reaction. The IRG-819/2-ITX/co-initiator system may
be used to cure lenses forming compositions which include a UV
absorbing compound. This initiator system may also be used to form
colored lenses.
[0306] An initiator system that is less efficient than the
IRG-819/2-ITX/co-initiator system includes a mixture of the
photoinitiators IRG-819 and 2-ITX, see Formula 31. This system is
less efficient at initiating polymerization of lens forming
compositions than the IRG-819/2-ITX/co-initiator system. The
IRG-819/2-ITX system may be used to cure very reactive monomer
compositions. An initiator system having a similar efficiency to
the IRG-819/2-ITX system includes a mixture of IRG-819 and
co-initiator, see Formulas 1-6,8-9, 11, 14-15, 19-22, and 25-26.
The IRG-819/co-initiator system may be used to cure clear lenses
which do not include a UV blocking compound and photochromic lens
forming compositions.
[0307] Another initiator system which may be used includes the
photoinitiator 2-ITX and a co-initiator. This initiator system is
much less efficient at initiating polymerization reactions than the
IRG-819/co-initiator system. The 2-ITX/co-initiator system is
preferably used for curing monomer compositions which include
highly reactive monomers.
[0308] The use of the above described mid-index lens forming
compositions may minimize or eliminate a number of problems
associated with activating light curing of lenses. One problem
typical of curing eyeglass lenses with activating light is
pre-release. Pre-release may be caused by a number of factors. If
the adhesion between the mold faces and the shrinking lens forming
composition is not sufficient, pre-release may occur. The
propensity of a lens forming composition to adhere to the mold
face, in combination with its shrinkage, determine how the process
variables are controlled to avoid pre-release. Adhesion is affected
by such factors as geometry of the mold face (e.g., high-add
flattop bifocals tend to release because of the sharp change in
cavity height at the segment line), the temperature of the mold
assembly, and the characteristics of the in-mold coating material.
The process variables which are typically varied to control
pre-release include the application of cooling fluid to remove
exothermic heat, controlling the rate of heat generation by
manipulating the intensities and timing of the activating
radiation, providing differential light distribution across the
thin or thick sections of the mold cavity manipulating the
thickness of the molds, and providing in-mold coatings which
enhance adhesion. An advantage of the above described mid-index
lens forming compositions is that the composition appears to have
enhanced adhesion characteristics. This may allow acceptable lenses
to be produced over a greater variety of curing conditions. Another
advantage is that higher diopter lenses may be produced at
relatively low pre-release rates, broadening the achievable
prescription range.
[0309] Another advantage of the above described mid-index lens
forming compositions is that they tend to minimize problems
associated with dripping during low intensity curing of lenses
(e.g., in the 1 to 6 milliwatt range). Typically, during the
irradiation of the lens forming composition with activating light,
small amounts of monomer may be squeezed out of the cavity and run
onto the non-casting faces of the molds. Alternatively, during
filling of the mold assembly with the lens forming composition, a
portion of the lens forming composition may drip onto the
non-casting faces of the mold assembly. This "dripping" onto the
non-casting faces of the mold assembly tends to cause the
activating light to focus more strongly in the regions of the
cavity located underneath the drippings. This focusing of the
activating light may affect the rate of curing. If the rate of
curing underneath the drippings varies significantly from the rate
of curing throughout the rest of the lens forming composition,
optical distortions may be created in the regions below the
drippings.
[0310] It is believed that differences in the rate of gelation
between the center and the edge regions of the lens forming
composition may cause dripping to occur. During the curing of a
lens forming composition, the material within the mold cavity tends
to swell slightly during the gel phase of the curing process. If
there is enough residual monomer around the gasket lip, this liquid
will tend to be forced out of the cavity and onto the non-casting
faces of the mold. This problem tends to be minimized when the lens
forming composition undergoes fast, uniform gelation. Typically, a
fast uniform gelation of the lens forming composition may be
achieved by manipulating the timing, intensities, and distribution
of the activating radiation. The above described mid-index lens
forming compositions, however, tend to gel quickly and uniformly
under a variety of curing conditions, thus minimizing the problems
caused by dripping.
[0311] Another advantage of the above described mid-index lens
forming compositions is that the compositions tend to undergo
uniform curing under a variety of curing conditions. This uniform
curing tends to minimize optical aberrations within the formed
lens. This is especially evident during the formation of high plus
power flattop lenses which tend to exhibit optical distortions
after the lens forming composition is cured. It is believed that
the activating radiation may be reflected off of the segment line
and create local differences in the rate of gelation in the regions
of the lens forming composition that the reflected light reaches.
The above described mid-index lens forming compositions tend to
show less optical distortions caused by variations of the intensity
of activating radiation throughout the composition.
[0312] Other advantages include drier edges and increased rigidity
of the formed lens. An advantage of drier edges is that the
contamination of the optical faces of the lens by uncured or
partially cured lens forming composition is minimized.
Methods of Forming Plastic Lenses
[0313] Plastic lenses may be formed by disposing a lens forming
composition into the mold cavity of a mold assembly and irradiating
the mold assembly with activating light. Coating materials may be
applied to the mold members prior to filling the mold cavity with
the lens forming composition. The lens may be treated in a
post-cure unit after the lens-curing process is completed.
[0314] The operation of the above described system to provide
plastic lenses involves a number of operations. These operations
are preferably coordinated by the controller 50, which has been
described above. After powering the system, an operator is
preferably signaled by the controller to enter the prescription of
the lens, the type of lens, and the type of coating materials for
the lens. Based on these inputted values the controller will
preferably indicate to the operator which molds and gaskets will be
required to form the particular lens.
[0315] After obtaining the appropriate mold members the mold
members are preferably cleaned prior to loading with a lens forming
composition. The inner surface (i.e., casting surface) of the mold
members may be cleaned on a spin coating unit 20 by spraying the
mold members with a cleaning solution while spinning the mold
members. Examples of cleaning solutions include methanol, ethanol,
isopropyl alcohol, acetone, methyl ethyl ketone, or a water based
detergent cleaner. Preferably, a cleaning solution which includes
isopropyl alcohol is used to clean the mold members. As the mold
member is contacted with the cleaning solution, dust and dirt may
be removed and transferred into the underlying dish 115 of the
curing unit. After a sufficient amount of cleaning solution has
been applied the mold members may be dried by continued spinning
without the application of cleaning solution.
[0316] In an embodiment, the inner surface, i.e., the casting face,
of the front mold member may be coated with one or more hardcoat
layers before the lens forming composition is placed within the
mold cavity. Preferably, two hardcoat layers are used so that any
imperfections, such as pin holes in the first hardcoat layer, are
covered by the second hardcoat layer. The resulting double hardcoat
layer is preferably scratch resistant and protects the subsequently
formed eyeglass lens to which the double hardcoat layer adheres.
The hardcoat layers are preferably applied using a spin coating
unit 20. The mold member is preferably placed in the spin coating
unit and the coating material applied to the mold while spinning at
high speeds (e.g., between about 900 to 1000 RPM). After a
sufficient amount of coating material has been applied, the coating
material may be cured by the activating light source disposed in
the cover. The cover is preferably closed and activating light is
preferably applied to the mold member while the mold member is
spinning at relatively low speeds (e.g., between about 150 to 250
RPM). Preferably control of the spinning and the application of
activating light is performed by controller 50. Controller 50 is
preferably configured to prompt the operator to place the mold
members on the coating unit, apply the coating material to the mold
member, and close the cover to initiate curing of the coating
material.
[0317] In an embodiment, the eyeglass lens that is formed may be
coated with a hydrophobic layer, e.g. a hardcoat layer. The
hydrophobic layer preferably extends the life of the photochromic
pigments near the surfaces of the lens by preventing water and
oxygen molecules from degrading the photochromic pigments.
[0318] In a preferred embodiment, both mold members may be coated
with a cured adhesion-promoting composition prior to placing the
lens forming composition into the mold cavity. Providing the mold
members with such an adhesion-promoting composition is preferred to
increase the adhesion between the casting surface of the mold and
the lens forming composition. The adhesion-promoting composition
thus reduces the possibility of premature release of the lens from
the mold. Further, it is believed that such a coating also provides
an oxygen and moisture barrier on the lens which serves to protect
the photochromic pigments near the surface of the lens from oxygen
and moisture degradation. Yet further, the coating provides
abrasion resistance, chemical resistance, and improved cosmetics to
the finished lens.
[0319] In an embodiment, the casting face of the back mold member
may be coated with a material that is capable of being tinted with
dye prior to filling the mold cavity with the lens forming
composition. This tintable coat preferably adheres to the lens
forming composition so that dyes may later be added to the
resulting eyeglass lens for tinting the lens. The tintable coat may
be applied using the spin coating unit as described above.
[0320] The controller may prompt the user to obtain the appropriate
lens forming composition. In one embodiment, the controller will
inform the user of which chemicals and the amounts of each chemical
that is required to prepare the lens forming composition.
Alternatively, the lens forming compositions may be preformed. In
this case the controller may indicate to the operator which of the
preformed lens forming compositions should be used.
[0321] In an embodiment, dyes may be added to the lens forming
composition. It is believed that certain dyes may be used to attack
and encapsulate ambient oxygen so that the oxygen may be inhibited
from reacting with free radicals formed during the curing process.
Also, dyes may be added to the composition to alter the color of an
unactivated photochromic lens. For instance, a yellow color that
sometimes results after a lens is formed may be "hidden" if a
blue-red or blue-pink dye is present in the lens forming
composition. The unactivated color of a photochromic lens may also
be adjusted by the addition of non-photochromic pigments to the
lens forming composition.
[0322] In a preferred technique for filling the lens molding cavity
382 (see FIG. 11), the annular gasket 380 is placed on a concave or
front mold member 392 and a convex or back mold member 390 is moved
into place. The annular gasket 380 is preferably pulled away from
the edge of the back mold member 390 at the uppermost point and a
lens forming composition is preferably injected into the lens
molding cavity 382 until a small amount of the lens forming
composition is forced out around the edge. The excess is then
removed, preferably, by vacuum. Excess liquid that is not removed
could spill over the face of the back mold member 390 and cause
optical distortion in the finished lens.
[0323] The mold assembly, with a lens forming composition disposed
within the mold cavity, is preferably placed within the lens curing
unit. Curing of the lens forming composition is preferably
initiated by the controller after the lens curing unit door is
closed. The curing conditions are preferably set by the controller
based on the prescription and type of lens being formed.
[0324] After the curing cycle has been completed. The controller
preferably prompts the user to remove the mold assembly from the
lens curing unit. In an embodiment, the cured lens may be removed
from the mold apparatus. The cured lens may be complete at this
stage and ready for use.
[0325] In another embodiment, the cured lens may require a post
cure treatment. After the lens is removed from the mold apparatus
the edges of the lens may be dried and scraped to remove any
uncured lens forming composition near the edges. The controller may
prompt the user to place the partially cured lens into a post-cure
unit. After the lens has been placed within the post-cure unit the
controller may apply light and/or heat to the lens to complete the
curing of the lens. In an embodiment, partially cured lenses may be
heated to about 115.degree. C. while being irradiated with
activating light. This post-treatment may be applied for about 5
minutes.
[0326] When casting a lens, particularly a positive lens that is
thick in the center, cracking may be a problem. Addition
polymerization reactions, including photochemical addition
polymerization reactions, may be exothermic. During the process, a
large temperature gradient may build up and the resulting stress
may cause the lens to crack. Yellowing of the finished lens may
also be a problem. Yellowing tends to be related to the monomer
composition, the identity of the photoinitiator, and the
concentration of the photoinitiator.
[0327] The formation of optical distortions usually occurs during
the early stages of the polymerization reaction during the
transformation of the lens forming composition from the liquid to
the gel state. Once patterns leading to optical distortions form
they may be difficult to eliminate. When gelation occurs there
typically is a rapid temperature rise. The exothermic
polymerization step causes a temperature increase, which in turn
causes an increase in the rate of polymerization, which causes a
further increase in temperature. If the heat exchange with the
surroundings is not sufficient to cool the lens, there will be a
runaway situation that leads to premature release, the appearance
of thermally caused striations and even breakage.
[0328] Accordingly, when continuous activating light is applied, it
is preferred that the reaction process be smooth and not too fast
but not too slow. Heat is preferably not generated by the process
so fast that it may not be exchanged with the surroundings. The
incident activating light intensity is preferably adjusted to allow
the reaction to proceed at a desired rate. It is also preferred
that the seal between the annular gasket 380 and the opposed mold
members 378 be as complete as possible.
[0329] Factors that have been found to lead to the production of
lenses that are free from optical distortions may be (1) achieving
a good seal between the annular gasket 380 and the opposed mold
members 378; (2) using mold members 378 having surfaces that are
free from defects; (3) using a formulation having an appropriate
type and concentration of photoinitiator that will produce a
reasonable rate of temperature rise; and (4) using a homogeneous
formulation. Preferably, these conditions are optimized.
[0330] Premature release of the lens from the mold will result in
an incompletely cured lens and the production of lens defects.
Factors that contribute to premature release may be (1) a poorly
assembled mold assembly 352; (2) the presence of air bubbles around
the sample edges; (3) imperfection in gasket lip or mold edge; (4)
inappropriate formulation; (5) uncontrolled temperature rise; and
(6) high or non-uniform shrinkage. Preferably, these conditions are
minimized.
[0331] Premature release may also occur when the opposed mold
members 378 are held too rigidly by the annular gasket 380.
Preferably, there is sufficient flexibility in the annular gasket
380 to permit the opposed mold members 378 to follow the lens as it
shrinks. Indeed, the lens must be allowed to shrink in diameter
slightly as well as in thickness. The use of an annular gasket 380
that has a reduced degree of stickiness with the lens during and
after curing is therefore desirable.
[0332] Despite the above problems, the advantages offered by the
radiation cured lens molding system clearly outweigh the
disadvantages. The advantages of a radiation cured system include a
significant reduction in energy requirements, curing time and other
problems normally associated with conventional thermal systems.
[0333] 1. Method of Forming a Plastic Lens by Curing With
Activating Light.
[0334] In one embodiment, plastic lenses may be formed by disposing
a lens forming composition into the mold cavity of a mold assembly
and irradiating the mold assembly with activating light. Coating
materials may be applied to the mold members prior to filling the
mold cavity with the lens forming composition. The lens may be
treated in a post-cure unit after the lens-curing process is
completed.
[0335] The lens forming composition is preferably prepared
according to the following protocol. Appropriate amounts of HDDMA,
TTEGDA, TMPTA and TRPGDA are mixed and stirred thoroughly,
preferably with a glass rod. The acrylate/methacrylate mixture may
then be passed through a purification column.
[0336] A suitable purification column may be disposed within a
glass column having a fitted glass disk above a Teflon stopcock and
having a top reservoir with a capacity of approximately 500 ml and
a body with a diameter of 22 mm and a length of about 47 cm. The
column may be prepared by placing on the fitted glass disk
approximately 35 g. of activated alumina (basic), available from
ALFA Products, Johnson Matthey, Danvers, Mass. in a 60 mesh form or
from Aldrich in a 150 mesh form. Approximately 10 g. of an
inhibitor remover (hydroquinone/methylester remover) available as
HR-4 from Scientific Polymer Products, Inc., Ontario, N.Y. then may
be placed on top of the alumina and, finally, approximately 35 g.
of activated alumina (basic) may be placed on top of the inhibitor
remover.
[0337] Approximately 600 g. of the acrylate/methacrylate mixture
may then be added above the column packing. An overpressure of 2-3
psi may then be applied to the top of the column resulting in a
flow rate of approximately 30 to 38 grams per hour. Parafilm may be
used to cover the junction of the column tip and the receiving
bottle to prevent the infiltration of dust and water vapor. The
acrylate/methacrylate mixture, preferably, may be received in a
container that is opaque to activating light.
[0338] An appropriate amount of bisphenol A bis(allyl carbonate)
may then be added to the acrylate/methacrylate mixture to prepare
the final monomer mixture.
[0339] An appropriate amount of a photoinitiator may then be added
to the final monomer mixture, The final monomer mixture, with or
without photoinitiator, may then be stored in a container that is
opaque to activating light.
[0340] An appropriate amount of a dye may also be added to the
final monomer mixture, with or without photoinitiator.
[0341] After filling the mold cavity with the lens forming
composition, the mold assembly is preferably irradiated with
activating light. In one embodiment, the lamps generate an
intensity at the lamp surface of approximately 4.0 to 7.0
mW/cm.sup.2 of ultraviolet light having wavelengths between 300 and
400 nm, which light is very uniformly distributed without any sharp
discontinuities throughout the reaction process. Such bulbs are
commercially available from Sylvania under the trade designation
Sylvania Fluorescent (F15T8/2052) or Sylvania Fluorescent
(F15T8/350BL/18") GTE. Activating light having wavelengths between
300 and 400 nm is preferred because the photoinitiators preferably
absorb most efficiently at this wavelength and the mold members
378, preferably, allow maximum transmission at this wavelength. It
is preferred that there be no sharp intensity gradients of
activating light either horizontally or vertically through the lens
composition during the curing process. Sharp intensity gradients
through the lens may lead to defects in the finished lens.
[0342] If lenses are produced with continuous activating light
without any mold cooling, the temperature of the mold-lens assembly
may rise to above 50.degree. C. Low diopter lenses may be prepared
in this fashion, but higher plus or minus diopter lenses may fail.
Certain lenses may be made by controlling (e.g., cooling) the
temperature of the lens material during cure with circulating
uncooled fluid (i.e., fluid at ambient temperatures). The ambient
fluid in these systems is preferably directed towards the mold
members in the same manner as described above. Circulating ambient
temperature fluid permits manufacture of a wider range of
prescriptions than manufacture of the lenses without any mold
cooling at all.
[0343] Many polymerization factors may be interrelated. The ideal
temperature of polymerization is typically related to the diopter
and thickness of the lens being cast. Lower temperatures (below
about 10.degree. C.) are preferred to cast higher + or - diopter
lenses when using continuous activating light. These lower
temperatures tend to permit an increase in photoinitiator
concentration, which in turn may speed up the reaction and lower
curing time.
[0344] Preventing premature release when using continuous
activating light may also be somewhat dependent upon the flow rates
of cooling fluid, as well as its temperature. For instance, if the
temperature of the cooling fluid is decreased it may also be
possible to decrease the flowrate of cooling fluid. Similarly, the
disadvantages of a higher temperature cooling fluid may be somewhat
offset by higher flow rates of cooling fluid.
[0345] In one embodiment the air flow rates for a dual distributor
system (i.e., an air distributor above and below the lens
composition) are about 1-30 standard cubic feet ("scf") (about
0.028-0.850 standard cubic meters, "scm") per minute per
distributor, more preferably about 4-20 scf (about 0.113-0.566 scm)
per minute per distributor, and more preferably still about 9-15
scf (about 0.255-0.423 scm) per minute per distributor. "Standard
conditions," as used herein, means 60.degree. F. (about
15.5.degree. C.) and one atmosphere pressure (about 101
kilopascals).
[0346] The thickness of the glass molds used to cast polymerized
lenses may affect the lenses produced. A thinner mold tends to
allow more efficient heat transfer between the polymerizing
material and the cooling air, thus reducing the rate of premature
release. In addition, a thinner mold tends to exhibit a greater
propensity to flex. A thinner mold tends to flex during the
relatively rapid differential shrinkage between the thick and thin
portions of a polymerized lens, again reducing the incidence of
premature release. In one embodiment the first or second mold
members have a thickness less than about 5.0 mm, preferably about
1.0-5.0 mm, more preferably about 2.0-4.0 mm, and more still about
2.5-3.5 mm.
[0347] "Front" mold or face means the mold or face whose surface
ultimately forms the surface of an eyeglass lens that is furthest
from the eye of an eyeglass lens wearer. "Back" mold or face means
the mold or face whose surface ultimately forms the surface of an
eyeglass lens that is closest to the eye of an eyeglass lens
wearer.
[0348] In one embodiment, the lens forming material is preferably
cured to form a solid lens at relatively low temperatures,
relatively low continuous activating light intensity, and
relatively low photoinitiator concentrations. Lenses produced as
such generally have a Shore D hardness of about 60-78 (for
preferred compositions) when cured for about 15 minutes as
described above. The hardness may be improved to about 80-81 Shore
D by postcure heating the lens in a conventional oven for about 10
minutes, as described above.
[0349] The activating light cured lenses may demonstrate excellent
organic solvent resistance to acetone, methyl ethyl ketone, and
alcohols.
[0350] 2. Preparing Lenses of Various Powers by Altering the Lens
Forming Conditons.
[0351] It has been determined that in some embodiments the finished
power of an activating light polymerized lens may be controlled by
manipulating the curing temperature of the lens forming
composition. For instance, for an identical combination of mold
members and gasket, the focusing power of the produced lens may be
increased or decreased by changing the intensity of activating
light across the lens mold cavity or the faces of the opposed mold
members.
[0352] As the lens forming material begins to cure, it passes
through a gel state, the pattern of which, within the mold
assembly, leads to the proper distribution of internal stresses
generated later in the cure when the lens forming material begins
to shrink. As the lens forming material shrinks during the cure,
the opposed mold members will preferably flex as a result of the
different amounts of shrinkage between the relatively thick and the
relatively thin portions of the lens. When a negative lens, for
example, is cured, the upper or back mold member will preferably
flatten and the lower or front mold member will preferably steepen
with most of the flexing occurring in the lower or front mold
member. Conversely, with a positive lens, the upper or back mold
member will preferably steepen and the lower or front mold member
will preferably flatten with most of the flexing occurring in the
upper or back mold member.
[0353] By varying the intensity of the activating light between the
relatively thin and the relatively thick portions of the lens in
the lens forming cavity, it is possible to create more or less
total flexing. Those light conditions which result in less flexing
will tend to minimize the possibility of premature release.
[0354] The initial curvature of the opposed mold members and the
center thickness of the lens produced may be used to compute the
targeted power of the lens. Herein, the "targeted power" of a lens
is the power a lens may have if the lens were to have a curvature
and thickness substantially identical to the mold cavity formed by
the opposed mold members. The activating light conditions may be
manipulated to alter the power of the lens to be more or less than
the targeted power.
[0355] By varying the amount of activating light reaching the lens
mold the polymerization rate, and therefore the temperature of the
lens forming composition may be controlled. It has been determined
that the maximum temperature reached by the lens forming
composition during and/or after activation by light may effect the
final power of the lens. By allowing the lens forming composition
to reach a temperature higher than the typical temperatures
described in previous embodiments, but less than the temperature at
which the formed lens will crack, the power of the lens may be
decreased. Similarly, controlling the polymerization such that the
temperature of the lens forming composition remains substantially
below the typical temperatures described in previous embodiments,
but at a sufficient temperature such that a properly cured lens is
formed, the power of the lens may be increased. Similarly,
increasing the temperature of the lens forming composition during
curing may decrease the power of the resulting lens.
[0356] In an embodiment, an ophthalmic eyeglass lens may be made
from a lens forming composition comprising a monomer and a
photoinitiator, by irradiation of the lens forming composition with
activating light. The composition may optionally include one or
more of: an ultraviolet/visible light absorbing compound, a
polymerization inhibitor, a co-initiator, a hindered amine light
stabilizer, and a dye. The activating light may include
ultraviolet, actinic, visible or infrared light. The lens forming
composition may be treated with activating light such that an
eyeglass is formed that has a power substantially equal to the
targeted power for a given mold cavity. The peak temperature of the
lens forming process may be the maximum temperature attained after
the application of each pulse of activating light. As depicted in
FIG. 40, each pulse of activating light may cause the lens forming
composition to rise to a peak temperature.
[0357] After reaching this peak temperature the lens forming
composition may begin to cool until the next application of
activating light. If the peak temperature of the lens forming
composition is controlled such that the formed lens has a power
substantially equal to the targeted power, the peak temperature is
referred to as the "matching temperature". The matching temperature
may be determined by performing a series of experiments using the
same mold cavity. In these experiments the peak temperature
attained during the process is preferably varied. By measuring the
power of the lenses obtained through this experiment the matching
temperature range may be determined.
[0358] When the temperature of the lens forming composition is
allowed to rise above the matching temperature during treatment
with activating light, the power of the lens may be substantially
less than the targeted power of the lens. Alternatively, when the
temperature of the lens forming composition is allowed to remain
below the matching temperature, the power of the lens may be
substantially greater than the targeted power of the lens. In this
manner, a variety of lenses having substantially different lens
powers from the targeted power may be produced from the same mold
cavity.
[0359] When the lenses cured by the activating light are removed
from the opposed mold members, they are typically under a stressed
condition. It has been determined that the power of the lens may be
brought to a final resting power, by subjecting the lenses to a
post-curing heat treatment to relieve the internal stresses
developed during the cure and cause the curvature of the front and
the back of the lens to shift. Typically, the lenses may be cured
by the activating light in about 10-30 minutes (preferably about 15
minutes). The post-curing heat treatment is preferably conducted at
approximately 85-120.degree. C. for approximately 5-15 minutes.
Preferably, the post-curing heat treatment is conducted at
100-110.degree. C. for approximately 10 minutes. Prior to the
post-cure, the lenses generally have a lower power than the final
resting power. The post-curing heat treatment reduces yellowing of
the lens and reduces stress in the lens to alter the power thereof
to a final resting power.
[0360] In an embodiment, an ophthalmic eyeglass lens may be made
from a lens forming composition comprising a monomer and a
photoinitiator, by irradiation of the lens forming composition with
activating light. The composition may optionally include one or
more of: an ultraviolet/visible light absorbing compound, a
polymerization inhibitor, a co-initiator, a hindered amine light
stabilizer, and a dye. The activating light may include
ultraviolet, actinic, visible or infrared light. The lens forming
composition may be treated with activating light such that an
eyeglass is formed. The lens may be kept within the mold cavity
formed by the mold members until the light has completely cured the
lens forming composition. The minimum time which a lens must remain
in the mold cavity to produce a lens with the targeted power, with
respect to the mold cavity, is herein referred to as the "demolding
time". The demolding time may be determined by performing a series
of experiments using the same mold cavity. In these experiments the
time that the lens is released from the mold cavity during the
process is preferably varied. By measuring the power of the lenses
obtained through these experiments the demolding time range may be
determined.
[0361] When a formed lens is removed prior to the demolding time,
the power of the lens may be substantially greater than the
targeted power of the lens. By varying the demolding time a variety
of lenses having substantially greater lens powers from the
targeted power may be produced from the same mold cavity.
[0362] 3. Postcure With an Oxygen Barrier Enriched With
Photoinitiator
[0363] In certain applications, all of the lens forming composition
may fail to completely cure by exposure to activating light when
forming the lens. In particular, a portion of the lens forming
composition proximate the gasket often remains in a liquid state
following formation of the lens. It is believed that the gaskets
may be often somewhat permeable to air, and, as a result, oxygen
permeates them and contacts the portions of the lens forming
material that are proximate the gasket. Since oxygen tends to
inhibit the polymerization process, portions of the lens forming
composition proximate the gasket tend to remain uncured as the lens
is formed.
[0364] Uncured lens forming composition proximate the gasket may be
a problem for several reasons. First, the liquid lens forming
composition leaves the edges of the cured lens in a somewhat sticky
state, which makes the lenses more difficult to handle. Second, the
liquid lens forming composition may be somewhat difficult to
completely remove from the surface of the lens. Third, liquid lens
forming composition may flow and at least partially coat the
surface of lenses when such lenses are removed from the molds. This
coating may be difficult to remove and makes application of scratch
resistant coatings or tinting dyes more difficult. This coating
tends to interfere with the interaction of scratch resistant
coatings and tinting dyes with the cured lens surface. Fourth, if
droplets of liquid lens forming material form, these droplets may
later cure and form a ridge or bump on the surface of the lens,
especially if the lens undergoes later postcure or scratch
resistant coating processes. As a result of the above problems,
often lenses must be tediously cleaned or recast when liquid lens
forming composition remains after the lens is formed in an initial
cure process.
[0365] The problems outlined above may be mitigated if less liquid
lens forming composition remains proximate the gasket after the
lens is formed. One method of lessening this "wet edge" problem
relates to increasing the amount of photoinitiator present in the
lens forming composition (i.e., increasing the amount of
photoinitiator in the lens forming composition above about 0.15
percent). Doing so, however, tends to create other problems.
Specifically, increased photoinitiator levels tend to cause
exothermic heat to be released at a relatively high rate during the
reaction of the composition. Premature release and/or lens cracking
tends to result. Thus it is believed that lower amounts of
photoinitiator are preferred.
[0366] The wet edge problem has been addressed by a variety of
methods described in U.S. Pat. No. 5,529,728 to Buazza et. al. Such
methods relate to removing the gasket and applying either an oxygen
barrier or a photoinitiator enriched liquid to the exposed edge of
the lens. The lens is preferably re-irradiated with sufficient
activating light to completely dry the edge of the lens prior to
demolding.
[0367] An embodiment relates to improving the methods described in
U.S. Pat. No. 5,529,728 to Buazza et. al. This embodiment relates
to combining an oxygen barrier with a photoinitiator. Specifically,
in one embodiment an oxygen barrier 970 (e.g., a thin strip of
polyethylene film or the like as shown in FIG. 12) is preferably
embedded or impregnated with a photoinitiator 972. The oxygen
barrier is preferably wrapped around the edge of a cured lens which
is still encased between two molds (but with the gasket removed).
While still "in the mold," the lens is preferably exposed to
activating light, thereby drying its edge. An improvement of this
method over those previously disclosed is that there may be a
significant reduction in the dosage of activating light necessary
to bring the lens edge to dryness.
[0368] A plastic oxygen barrier film which includes a
photoinitiator may be made by: (a) immersing a plastic film in a
solution comprising a photoinitiator, (b) removing the plastic film
from the solution, and (c) drying the plastic film. The solution
may include an etching agent. Preferably a surface of the plastic
film is etched prior to or while immersing the plastic film in the
solution.
[0369] In one example, thin strips (e.g., about 10 mm wide) of high
density polyethylene film (approximately 0.013 mm thick) may be
soaked in a solution of 97% acetone and 3% Irgacure 184 (a
photoinitiator commercially available from Ciba Geigy located in
Farmingdale, N.J.) for about five minutes. The polyethylene film
may be obtained from Tape Solutions, Inc. (Nashville, Tenn.). In a
more preferred embodiment, 0.5% BYK-300 (a flow agent commercially
available from BYK Chemie located in Wallingford, Conn.) may be
included in the soaking solution. It is believed that xylene in the
BYK-300 tends to etch the surface of the film and make the film
more receptive to absorption of the Irgacure 184. In a still more
preferred embodiment, the treated polyethylene strips may be dipped
in acetone for about ten seconds to remove excess Irgacure 184.
Excess photoinitiator may be seen as a white powder which coats the
strips after drying. In either case, the strips are preferably
allowed to air dry before applying them to the edge of the lens as
described above.
[0370] In one alternate embodiment, a plastic eyeglass lens may be
made by the following steps: (1) placing a liquid polymerizable
lens forming composition in a mold cavity defined by a gasket, a
first mold member, and a second mold member; (2) directing first
activating light rays toward at least one of the mold members to
cure the lens forming composition so that it forms a lens with a
back face, edges, and a front face, and wherein a portion of the
lens forming composition proximate the edges of the lens is not
fully cured; (3) removing the gasket to expose the edges of the
lens; (4) applying an oxygen barrier which includes a
photoinitiator around the exposed edges of the lens such that at
least a portion of the oxygen barrier photoinitiator is proximate
lens forming composition that is not fully cured; and (5) directing
second activating light rays towards the lens such that at least a
portion of the oxygen barrier photoinitiator initiates reaction of
lens forming composition while the oxygen barrier substantially
prevents oxygen from outside the oxygen barrier from contacting at
least a portion of the lens forming composition. The first and
second activating light rays may (a) be at the same or different
wavelengths and/or intensities, (b) be continuous or pulsed, and
(c) be from the same or different light source.
[0371] A purpose of the steps 4-5 is to reduce the amount of
uncured liquid lens forming composition that is present when the
lens is separated from the molds and/or gasket. It has been found
that reducing the amount of liquid lens forming composition may be
especially advantageous if such reduction occurs before the molds
are separated from the cured lens. Separating the molds from the
cured lens may cause uncured liquids to at least partially coat the
lens faces. This coating may occur when uncured liquid lens forming
composition gets swept over the faces when the molds are separated
from the lens. It is believed that curing of the lens tends to
create a vacuum between the lens and the mold. Air may sweep over
the mold faces to fill this vacuum when the molds are separated
from the lens. This air tends to take liquid lens forming
composition into the vacuum with it.
[0372] In step 4 above, an oxygen barrier which includes a
photoinitiator is preferably applied to the edges or sides of the
lens after the gasket is removed. Preferably, this oxygen barrier
is applied while the lens is still attached to the molds. In an
alternate embodiment, this oxygen barrier is preferably applied to
the edges or sides of the molds at the same time it is applied to
the sides of the lens. In a preferred embodiment, the sides of the
lenses are first cleaned or wiped to remove at least a portion of
the uncured liquid lens forming composition before the oxygen
barrier is applied.
[0373] After the oxygen barrier is applied, second activating light
rays may be directed towards the lens. After the second activating
light rays are directed toward the lens, at least a portion of the
liquid lens forming composition that was not cured in the initial
cure steps may be cured. It is believed that the photoinitiator
embedded in the oxygen barrier facilitates faster and more complete
curing of the uncured lens forming composition. As such, less
second activating light rays may be employed, thereby lessening the
time and energy required in this step. Furthermore, lens quality
tends to be enhanced since a lower application of the second
activating light rays tends to reduce the potential for lens
yellowing.
[0374] In a preferred embodiment, substantially all of the
remaining liquid lens forming composition is cured after the second
activating light rays are directed toward the lens. More
preferably, the lens is substantially dry after the second
activating light is directed towards the lens.
[0375] After the second activating light is directed toward the
lens, the lens may then be demolded. The lens may then be tinted.
After the lens is demolded, a scratch resistant coating may be
applied to the lens. In one embodiment, a scratch resistant coating
is preferably applied to the demolded lens by applying a liquid
scratch resistant coating composition to a face of the lens and
then applying activating light rays to this face to cure the liquid
scratch resistant coating to a solid.
[0376] In an embodiment, the activating light for curing the
scratch resistant coating is ultraviolet light. The intensity of
the activating light applied to the face of the lens to cure the
liquid scratch resistant coating composition to a solid is
preferably about 150-300 mW/cm.sup.2 at a wavelength range of about
360-370 nm, and about 50-150 mW/cm.sup.2 at a wavelength range of
about 250-260 nm. The lens may be heated after removal from the
molds, or after application of a scratch resistant coating to the
lens.
[0377] In a preferred embodiment, the above method may further
include the additional step of directing third activating light
rays towards the lens before the oxygen barrier is applied. These
third activating light rays are preferably applied before the
gasket is removed. Preferably, the second and third activating
light rays are directed toward the back face of the lens (as stated
above, the second and third activating light rays are preferably
applied while this lens is in the mold cavity). The third
activating light rays are preferably about the same range of
intensity as the second activating light rays. The same apparatus
may be used for both the second and third activating light
rays.
[0378] In a preferred embodiment, the method described above also
includes the step of removing the oxygen barrier from the edges of
the lens.
[0379] The second and third activating light rays may be repeatedly
directed towards the lens. For instance, these activating light
rays may be applied via a light assembly whereby the lens passes
under a light source on a movable stand. The lens may be repeatedly
passed under the lights. Repeated exposure of the lens to the
activating light rays may be more beneficial than one prolonged
exposure.
[0380] Preferably the oxygen barrier includes a film, and more
preferably a plastic, flexible, and/or elastic film. In addition,
the oxygen barrier is preferably at least partially transparent to
activating light so that activating light may penetrate the oxygen
barrier to cure any remaining liquid lens forming composition.
Preferably, the oxygen barrier is stretchable and self-sealing.
These features make the film easier to apply. Preferably, the
oxygen barrier is resistant to penetration by liquids, thus keeping
any liquid lens forming composition in the mold assembly.
Preferably, the oxygen barrier includes a thermoplastic
composition. It is anticipated that many different oxygen barriers
may be used (e.g., saran wrap, polyethylene, etc.). In one
preferred embodiment, the film is "Parafilm M Laboratory Film"
which is available from American National Can (Greenwich, Conn.,
U.S.A.). The oxygen barrier may also include aluminum foil.
[0381] Preferably, the oxygen barrier is less than about 1.0 mm
thick. More preferably, the oxygen barrier is 0.01 to 0.10 mm
thick, and more preferably still, the oxygen barrier is less than
0.025 mm thick. If the oxygen barrier is too thick, then it may not
be readily stretchable and/or conformable, and it may not allow a
sufficient amount of light to pass through it. If the oxygen
barrier is too thin, then it may tend to tear.
[0382] In an alternate method, a lens may be cured between two mold
members. The gasket may be removed and any remaining liquid lens
composition may be removed. At this point a mold member may be
applied to a substantially solid conductive heat source. Heat may
then be conductively applied to a face of the lens by (a)
conductively transferring heat to a face of a mold member from the
conductive heat source, and (b) conductively transferring heat
through such mold member to the face of the lens. The oxygen
barrier enriched with photoinitiator may then be applied, and
second activating light rays may be directed towards the lens to
cure the remaining lens forming composition.
[0383] 4. Applying Coating Materials to Lenses
[0384] In an embodiment, coating apparatus 20 may be used to apply
a pre-coat to a lens before the hardcoat is applied. The pre-coat
may serve to increase the "wettability" of the surface to which the
hardcoat is to be applied. A surfactant has been conventionally
employed for this purpose, however surfactants tend to affect the
volatility and flow characteristics of lens coatings in an
unfavorable manner. The pre-coat may include acetone and/or
BYK-300. Upon even distribution of the hardcoat onto a lens, the
coating may be wiped near the edges of the lens to prevent the
formation of excessive flakes during curing.
[0385] 5. Curing by the Application of Pulsed Activating Light
[0386] A polymerizable lens forming composition may be placed in a
mold/gasket assembly and continuously exposed to appropriate levels
of activating light to cure the composition to an optical lens. The
progress of the curing reaction may be determined by monitoring the
internal temperature of the composition. The lens forming
composition may be considered to pass through three stages as it is
cured: (1) induction, (2) gel formation & exotherm, and (3)
extinction. These stages are illustrated in FIG. 22 for a
-0.75-1.00 power lens cured by continuous application of activating
light. FIG. 22 shows temperature within the mold cavity as a
function of time throughout a continuous radiation curing
cycle.
[0387] The induction stage occurs at the beginning of the curing
cycle and is typically characterized by a substantially steady
temperature of the lens forming composition as it is irradiated
with activating light (or falling temperature when the curing,
chamber temperature is below that of the composition). During the
induction period, the lens forming composition remains in a liquid
state as the photoinitiator breaks down and consumes inhibitor and
dissolved oxygen present in the composition. As the inhibitor
content and oxygen content of the composition fall, decomposing
photoinitiator and the composition begin to form chains to produce
a pourable, "syrup-like" material.
[0388] As irradiation continues, the "syrup" proceeds to develop
into a soft, non-pourable, viscous, gel. A noticeable quantity of
heat will begin to be generated during this soft gel stage. The
optical quality of the lens may be affected at this point. Should
there be any sharp discontinuities in the intensity of the
activating light (for example, a drop of composition on the
exterior of a mold which focuses light into a portion of the lens
forming composition proximate the drop), a local distortion will
tend to be created in the gel structure, likely causing an
aberration in the final product. The lens forming composition will
pass through this very soft gel state and through a firm gel state
to become a crystalline structure. When using OMB-91 lens forming
composition, a haze tends to form momentarily during the transition
between the gel and crystalline stages. As the reaction continues
and more double bonds are consumed, the rate of reaction and the
rate of heat generated by the reaction will slow, which may cause
the internal temperature of the lens forming composition to pass
through a maximum at the point where the rate of heat generation
exactly matches the heat removal capacity of the system.
[0389] By the time the maximum temperature has been reached and the
lens forming composition begins to cool, the lens will typically
have achieved a crystalline form and will tend to crack rather than
crumble if it is broken. The rate of conversion will slow
dramatically and the lens may begin to cool even though some
reaction still may be occurring. Irradiation may still be applied
through this extinction phase. Generally, the curing cycle is
assumed to be complete when the temperature of the lens forming
composition falls to a temperature near its temperature at the
beginning of exotherm (i.e., the point where the temperature of the
composition increased due to the heat released by the
reaction).
[0390] The continuous irradiation method tends to work well for
relatively low mass lenses (up to about 20-25 grams, see, e.g.,
U.S. Pat. Nos. 5,364,256 and 5,415,816). As the amount of material
being cured increases, problems may be encountered. The total
amount of heat generated during the exothermic phase is
substantially proportional to the mass of the lens forming
material. During curing of relatively high mass lenses, a greater
amount of heat is generated per a given time than during curing of
lower mass lenses. The total mold/gasket surface area available for
heat transfer (e.g., heat removal from the lens forming
composition), however, remains substantially constant. Thus, the
internal temperature of a relatively high mass of lens forming
material may rise to a higher temperature more rapidly than
typically occurs with a lower mass of lens forming material. For
example, the internal temperature of a low minus cast-to-finish
lens typically will not exceed about 100.degree. F., whereas
certain thicker semi-finished lens "blanks" may attain temperatures
greater than about 350.degree. F. when continually exposed to
radiation. The lens forming material tends to shrink as curing
proceeds and the release of excessive heat during curing tends to
reduce the adhesion between the mold and the lens forming material.
These factors may lead to persistent problems of premature release
and/or cracking during the curing of lens forming material having a
relatively high mass.
[0391] An advantage of the present method is the production of
relatively high-mass, semi-finished lens blanks and high power
cast-to-finish lenses without the above-mentioned problems of
premature release and cracking. The methods described below allow
even more control over the process of curing ophthalmic lenses with
activating light-initiated polymerization than previous methods. By
interrupting or decreasing the activating light at the proper time
during the cycle, the rate of heat generation and release may be
controlled and the incidence of premature release may be reduced.
An embodiment relates to a method of controlling the rate of
reaction (and therefore the rate of heat generation) of an
activating light-curable, lens forming material by applying
selected intermittent doses (e.g., pulses) of radiation followed by
selected periods of decreased activating light or "darkness". It is
to be understood that in the description that follows, "darkness"
refers to the absence of activating radiation, and not necessarily
the absence of visible light.
[0392] More particularly, an embodiment relates to: (a) an initial
exposure period of the lens forming material to radiation (e.g.,
continuous or pulsed radiation) extending through the induction
period, (b) interrupting or decreasing the irradiation before the
material reaches a first temperature (e.g., the maximum temperature
the composition could reach if irradiation were continued) and
allowing the reaction to proceed to a second temperature lower than
the first temperature, and (c) applying a sufficient number of
alternating periods of exposure and decreased activating light or
darkness to the lens forming material to complete the cure while
controlling the rate of heat generation and/or dissipation via
manipulation of the timing and duration of the radiation, or the
cooling in the curing chamber. FIG. 23 shows the temperature within
the mold cavity as a function of time for both (a) continuous
activating light exposure and (b) pulsed activating light
exposure.
[0393] In the context of this application, a "gel" occurs when the
liquid lens forming composition is cured to the extent that it
becomes substantially non-pourable, yet is still substantially
deformable and substantially not crystallized.
[0394] In the following description, it is to be understood that
the term "first period" refers to the length of time of the initial
exposure period where radiation (e.g., in pulses) is applied to the
lens forming composition, preferably to form at least a portion of
the composition into a gel. "First activating" rays or light refers
to the radiation applied to the lens forming composition during the
initial exposure period. "Second activating" rays or light refers
to the radiation that is applied to the lens forming composition
(e.g., in pulses) after the composition has been allowed to cool to
the "third temperature" mentioned above. "Second period" refers to
the duration of time that second activating rays are directed to
the lens forming composition. "Third period" refers to the duration
of decreased activating light or darkness that ensues after
activating light has been delivered in the second period.
[0395] In an embodiment, the lens forming material is preferably
placed in a mold cavity defined in part between a first mold member
and a second mold member. The first mold member and/or second mold
member may or may not be continuously cooled as the formation of
the lens is completed during the second period and/or third period.
One method of removing heat from the lens forming material is to
continuously direct air at a non-casting face of at least one of
the mold members. It is preferred that air be directed at both the
first and second mold members. A cooler may be used to cool the
temperature of the air to a temperature below ambient temperature,
more preferably between about 0.degree. C. and about 20.degree. C.,
and more preferably still between about 3.degree. C. and about
15.degree. C. Air may also be used to cool at least one of the mold
members (in any of the manners described previously) during the
first period.
[0396] In an embodiment, the first period ends when at least a
portion of the lens forming composition begins to increase in
temperature or form a gel, and the first activating rays are
decreased or removed (e.g., blocked) such that they cease to
contact the first or second mold members. It is preferred that the
first period be sufficient to allow the lens forming material to
gel in the mold cavity such that there is substantially no liquid
present (except small amounts proximate the edge of the material).
The interruption of irradiation prior to complete gellation may in
some circumstances produce optical distortions. It is preferred
that the length of the first period be selected to inhibit the lens
forming composition from reaching a first temperature. The first
temperature is preferably the maximum temperature that the lens
forming composition could reach if it was irradiated under the
system conditions (e.g., flow rate and temperature of any cooling
air, wavelength and intensity of radiation) until the "exothermic
potential" (i.e., ability to evolve heat through reaction) of the
composition was exhausted.
[0397] According to an embodiment, the reactions within the
composition are preferably allowed to proceed after the first
activating rays are removed until the composition reaches a second
temperature. The second temperature is preferably less than the
first temperature. The first temperature is preferably never
reached by the composition. Thus, the composition is preferably
prevented from achieving the first temperature and then cooling to
the second temperature. The composition is preferably allowed to
cool from the second temperature to the third temperature. This
cooling may occur "inactively" by allowing heat to transfer to the
ambient surroundings, or at least one of the mold members may be
cooled by any of the methods described above.
[0398] In an embodiment, the curing of the lens forming material
may be completed by directing second activating rays (e.g., in
pulses) toward at least one of the mold members. The second
activating rays may be directed toward the mold member(s) for a
second period that may be determined according to the rate of
reaction of the lens forming composition. The change in temperature
of the composition or a portion of the mold cavity, or the air in
or exiting the chamber may be an indicator of the rate of reaction,
and the second period may be determined accordingly. The second
period may be varied such that subsequent pulses have a longer or
shorter duration than previous pulses. The time between pulses
(i.e., the third period) may also be varied as a function of the
temperature and/or reaction rate of the composition. To achieve a
light pulse, (a) the power to a light source may be turned on and
then off, (b) a device may be used to alternately transmit and then
block the passage of light to the lens forming composition, or (c)
the light source and/or mold assembly may be moved to inhibit
activating light from contacting the lens forming material. The
second and/or third periods are preferably controlled to allow
rapid formation of a lens while reducing the incidence of (a)
premature release of the lens from the first and/or second mold
member and/or (b) cracking of the lens.
[0399] In an embodiment, the second period is preferably controlled
to inhibit the temperature of the composition from exceeding the
second temperature. The temperature of the lens forming composition
may continue to increase after radiation is removed from the first
and/or second mold members due to the exothermic nature of
reactions occurring within the composition. The second period may
be sufficiently brief such that the pulse of second activating rays
is removed while the temperature of the composition is below the
second temperature, and the temperature of the composition
increases during the third period to become substantially equal to
the second temperature at the point that the temperature of the
composition begins to decrease.
[0400] In an embodiment, the third period extends until the
temperature of the composition becomes substantially equal to the
third temperature. Once the temperature of the composition
decreases to the third temperature, a pulse of second activating
rays may be delivered to the composition. In an embodiment, the
second period remains constant, and the third period is preferably
controlled to maintain the temperature of the composition below the
second temperature. The third period may be used to lower the
temperature of the composition to a temperature that is expected to
cause the composition to reach but not exceed the second
temperature after a pulse is delivered to the composition.
[0401] In an embodiment, a shutter system may be used to control
the application of first and/or second activating rays to the lens
forming material. The shutter system preferably includes
air-actuated shutter plates that may be inserted into the curing
chamber to prevent activating light from reaching the lens forming
material. Alternatively, the shutter system may include an LCD
panel. Controller 50 may receive signals from thermocouple(s)
located inside the lens-curing chamber, proximate at least a
portion the mold cavity, or located to sense the temperature of air
in or exiting the chamber, allowing the time intervals in which the
shutters are inserted and/or extracted to be adjusted as a function
of a temperature within the curing chamber. The thermocouple may be
located at numerous positions proximate the mold cavity and/or
casting chamber.
[0402] The wavelength and intensity of the second activating rays
are preferably substantially equal to those of the first activating
rays. It may be desirable to vary the intensity and/or wavelength
of the radiation (e.g., first or second activating rays). The
particular wavelength and intensity of the radiation employed may
vary among embodiments according to such factors as the identity of
the composition and curing cycle variables.
[0403] Numerous curing cycles may be designed and employed. The
design of an optimal cycle should include consideration of a number
of interacting variables. Significant independent variables
include: 1) the mass of the sample of lens forming material, 2) the
intensity of the light applied to the material, 3) the physical
characteristics of the lens forming material, and 4) the cooling
efficiency of the system. Significant curing cycle (dependent)
variables include: 1) the optimum initial exposure time for
induction and gelling, 2) the total cycle time, 3) the time period
between pulses, 4) the duration of the pulses, and 5) the total
exposure time.
[0404] Most of the experiments involving these methods were
conducted using below described OMB-91 monomer. The OMB-91
formulation and properties are listed below.
[0405] OMB-91 Formulation:
5 INGREDIENT WEIGHT PERCENT Sartomer SR 351 (Trimethylolpropane
20.0 +/- 1.0 Triacrylate) Sartomer SR 268 (Tetraethylene 21.0 +/-
1.0 Glycol Diacrylate) Sartomer SR 306 (Tripropylene 32.0 +/- 1.0
Glycol Diacrylate) Sartomer SR 239 (1,6 Hexanediol 10.0 +/- 1.0
Dimethacrylate) (Bisphenol A Bis (Ally1 Carbonate)) 17.0 +/- 1.0
Irgacure 184 (1-Hydroxycyclohexyl 0.017 +/- 0.0002 Phenyl Ketone)
Methyl Benzoyl Formate 0.068 +/- 0.0007 Methyl Ester of
Hydroquinone ("MeHQ") 35 ppm +/- 10 ppm Thermoplast Blue P
(9,10-Anthracenedione, 0.35 ppm +/- 0.1 ppm 1-hydroxy-4-((4-methyl
phenyl) Amino)
[0406] Measurements/Properties:
6 PROPERTY PROPOSED SPECIFICATION Appearance Clear Liquid Color
(APHA) 50 maximum (Test Tube Test) Match Standard Acidity (ppm as
Acrylic Acid) 100 maximum Refractive Index 1.4725 +/- 0.002 Density
1.08 +/- 0.005 gm/cc. at 23.degree. C. Viscosity @ 22.5 Degrees C.
27.0 +/- 2 centipoise Solvent Weight (wt %) 0.1 Maximum Water (wt
%) 0.1 Maximum MeHQ (from HPLC) 35 ppm +/- 10 ppm
[0407] It should be recognized that methods and systems disclosed
could be applied to a large variety of radiation-curable, lens
forming materials in addition to those mentioned herein. It should
be understood that adjustments to curing cycle variables
(particularly the initial exposure time) may be required even among
lens forming compositions of the same type due to variations in
inhibitor levels among batches of the lens forming compositions. In
addition, changes in the heat removal capacity of the system may
require adjustments to the curing cycle variables (e.g. duration of
the cooling periods between radiation pulses). Changes in the
cooling capacity of the system and/or changes in compositions of
the lens forming material may require adjustments to curing cycle
variables as well.
[0408] Significant variables impacting the design of a pulsed
curing cycle include (a) the mass of the material to be cured and
(b) the intensity of the activating light applied to the material.
If a sample is initially overdosed with radiation, the reaction may
progress too far and increase the likelihood of premature release
and/or cracking. If a sample is underdosed initially in a fixed
(i.e., preset) curing cycle, subsequent exposures may cause too
great a temperature rise later in the cycle, tending to cause
premature release and/or cracking. Additionally, if the light
intensity varies more than about +/-10% in a cycle that has been
designed for a fixed light intensity level and/or fixed mass of
lens forming material, premature release and/or cracking may
result.
[0409] An embodiment involves a curing cycle having two processes.
A first process relates to forming a dry gel by continuously
irradiating a lens forming composition for a relatively long
period. The material is preferably cooled down to a lower
temperature under darkness, after the irradiation is complete. A
second process relates to controllably discharging the remaining
exothermic potential of the material by alternately exposing the
material to relatively short periods of irradiation and longer
periods of decreased irradiation (e.g., dark cooling).
[0410] The behavior of the lens forming material during the second
process will depend upon the degree of reaction of the lens forming
material that has occurred during the first process. For a fixed
curing cycle, it is preferable that the extent of reaction
occurring in the first process consistently fall within a specified
range. If the progress of reaction is not controlled well, the
incidence of cracking and/or premature release may rise. For a
curing cycle involving a composition having a constant level of
inhibitor and initiator, the intensity of the radiation employed is
the most likely source of variability in the level of cure attained
in the first process. Generally, a fluctuation of +/-5% in the
intensity tends to cause observable differences in the cure level
achieved in the first process. Light intensity variations of +/-10%
may significantly reduce yield rates.
[0411] The effect of various light intensities on the material
being cured depends upon whether the intensity is higher or lower
than a preferred intensity for which the curing cycle was designed.
FIG. 25 shows temperature profiles for three embodiments in which
different light levels were employed. If the light intensity to
which the material is exposed is higher than a preferred intensity,
the overdosage may cause the reaction to proceed too far. In such a
case, excessive heat may be generated, increasing the possibility
of cracking and/or premature release during the first process of
the curing cycle. If premature release or cracking of the overdosed
material does not occur in the first process, then subsequent
pulses administered during the second process may create very
little additional reaction.
[0412] If the light intensity is lower than a preferred intensity
and the lens forming material is underdosed, other problems may
arise. The material may not be driven to a sufficient level of cure
in the first process. Pulses applied during the second process may
then cause relatively high amounts of reaction to occur, and the
heat generated by reaction may be much greater than the heat
removal capacity of the system. Thus the temperature of the lens
forming material may tend to excessively increase. Premature
release may result. Otherwise, undercured lenses that continue
generating heat after the end of the cycle may be produced.
[0413] The optimal initial radiation dose to apply to the lens
forming material may depend primarily upon its mass. The initial
dose may also be a function of the light intensity and exposure
time. A method for designing a curing cycle for a given
mold/gasket/monomer combination may involve selecting a fixed light
intensity.
[0414] The methods disclosed may involve a wide range of light
intensities. Using a relatively low intensity may allow for the
length of each cooling step to be decreased such that shorter and
more controllable pulses are applied. Where a fluorescent lamp is
employed, the use of a lower intensity may allow the use of lower
power settings, thereby reducing the load on the lamp cooling
system and extending the life of the lamp. A disadvantage of using
a relatively low light intensity is that the initial exposure
period may be somewhat longer. Relatively high intensity levels
tend to provide shorter initial exposure times while placing more
demand upon the lamp drivers and/or lamp cooling system, either of
which tends to reduce the life of the lamp.
[0415] Once a light intensity is selected, the initial exposure
time may be determined. A convenient method of monitoring the
reaction during the cycle involves fashioning a fine gauge
thermocouple, positioning it inside the mold cavity, and connecting
it to an appropriate data acquisition system. A preferred
thermocouple is Type J, 0.005 inch diameter, Teflon-insulated wire
available from Omega Engineering. The insulation is preferably
stripped back about 30 to 50 mm and each wire is passed through the
gasket wall via a fine bore hypodermic needle. The needle is
preferably removed and the two wires may be twisted together to
form a thermocouple Junction inside the inner circumference of the
gasket. The other ends of the leads may be attached to a miniature
connector which may be plugged into a permanent thermocouple
extension cord leading to the data acquisition unit after the mold
set is filled.
[0416] The data acquisition unit may be a Hydra 2625A Data Logger
made by John Fluke Mfg. Company. It is preferably connected to an
IBM compatible personal computer running Hydra Data Logger
software. The computer is preferably configured to display a trend
plot as well as numeric temperature readings on a monitor. The scan
interval may be set to any convenient time period and a period of
five or ten seconds usually provides good resolution.
[0417] The position of the thermocouple Junction in the mold cavity
may affect its reading and behavior through the cycle. When the
junction is located between the front and back molds, relatively
high temperatures may be observed compared to the temperatures at
or near the mold face. The distance from the edge of the cavity to
the junction may affect both absolute temperature readings as well
as the shape of the curing cycle's temperature plot. The edges of
the lens forming material may begin to increase in temperature
slightly later than other portions of the material. Later in the
cycle, the lens forming material at the center may be somewhat
ahead of the material at the edge and will tend to respond little
to the radiation pulses, whereas the material near the edge may
tend to exhibit significant activity. When performing experiments
to develop curing cycles, it is preferred to insert two probes into
the mold cavity, one near the center and one near the edge. The
center probe should be relied upon early in the cycle and the edge
probe should guide the later stages of the cycle.
[0418] Differing rates of reaction among various regions of the
lens forming material may be achieved by applying a differential
light distribution across the mold face(s). Tests have been
performed where "minus type" light distributions have caused the
edge of the lens forming material to begin reacting before the
center of the material. The potential advantages of using light
distributing filters to cure high mass semi-finished lenses may be
offset by non-uniformity of total light transmission that tends to
occur across large numbers of filters.
[0419] After the selection and/or configuration of (a) the
radiation intensity, (b) the radiation-curable, lens forming
material, (c) the mold/gasket set, and (d) the data acquisition
system, the optimum initial exposure period may be determined. It
is useful to expose a sample of lens forming material to continuous
radiation to obtain a temperature profile. This will provide an
identifiable range of elapsed time within which the optimal initial
exposure time will fall. Two points of interest may be the time
where the temperature rise in the sample is first detected ("T
initial" or "Ti"), and the time where the maximum temperature of
the sample is reached ("Tmax"). Also of interest is the actual
maximum temperature, an indication of the "heat potential" of the
sample under the system conditions (e.g., in the presence of
cooling).
[0420] As a general rule, the temperature of high mass lenses
(i.e., lenses greater than about 70 grams) should remain under
about 200.degree. F. and preferably between about 150.degree. F.
and about 180.degree. F. Higher temperatures are typically
associated with reduced lens yield rates due to cracking and/or
premature release. Generally, the lower mass lenses (i.e., lenses
no greater than about 45 grams) should be kept under about
150.degree. F. and preferably between about 110.degree. F. and
about 140.degree. F.
[0421] The first period may be selected according to the mass of
the lens forming material. In an embodiment, the lens forming
material has a mass of between about 45 grams and about 70 grams
and a selected second temperature between about 150.degree. F. and
about 200.degree. F. According to another embodiment, the lens
forming material has a mass no greater than about 45 grams and a
second temperature less than about 150.degree. F. In yet another
embodiment, the lens forming material has a mass of at least about
70 grams, and a second temperature between about 170.degree. F. and
about 190.degree. F.
[0422] An experiment may be performed in which the radiation is
removed from the mold members slightly before one-half of the time
between T initial and Tmax. The initial exposure time may be
interactively reduced or increased according to the results of the
above experiment in subsequent experiments to provide a Tmax in a
preferred range. This procedure may allow the determination of the
optimal initial exposure time for any given mold/gasket set and
light intensity.
[0423] A qualitative summary of relationships among system
variables related to the above-described methods is shown in FIG.
24.
[0424] After the initial exposure period, a series of irradiation
pulse/cooling steps may be performed to controllably discharge the
remaining exothermic potential of the material and thus complete
the cure. There may be at least two approaches to accomplish this
second process. The first involves applying a large number of very
short pulses and short cooling periods. The second approach
involves applying a fewer number of longer pulses with
correspondingly longer cooling periods. Either of these two methods
may produce a good product and many acceptable cycles may exist
between these extremes.
[0425] The described method relates to using pulsed application of
light to produce a large range (e.g., from -6 to +4 diopter) of
lenses without requiring refrigerated cooling fluid (e.g., cooled
air). With proper light application, air at ambient may be used as
a cooling fluid, thus significantly reducing system costs.
[0426] The following general rules for the design of pulse/cooling
cycles may be employed to allow rapid curing of a lens while
inhibiting premature release and/or cracking of the lens. The
duration of the pulses preferably does not result in a temperature
that exceeds the maximum temperature attained in the initial
exposure period. The length of the cooling period may be determined
by the length of time necessary for the internal temperature of the
lens forming material to return to near the temperature it had
immediately before it received a pulse. Following these general
rules during routine experimentation may permit proper curing
cycles to be established for a broad range of lens forming
materials, light intensity levels, and cooling conditions.
[0427] Preferably, light output is measured and controlled by
varying the amount of power applied to the lights in response to
changes in light output. Specifically, a preferred embodiment
includes a light sensor mounted near the lights. This light sensor
measures the amount of light, and then a controller increases the
power supplied to maintain the first activating light rays as the
intensity of the first activating light rays decreases during use,
and vice versa. Preferably, the power is varied by varying the
electric frequency supplied to the lights.
[0428] In an embodiment, a medium pressure mercury vapor lamp is
used to cure the lens forming material and the lens coating. This
lamp and many conventional light sources used for activating light
curing may not be repeatedly turned on and off since a several
minute warm-up period is generally required prior to operation.
Mercury vapor light sources may be idled at a lower power setting
between exposure periods (i.e., second periods), however, the light
source will still generate significant heat and consume electricity
while at the lower power setting.
[0429] In an embodiment, air at ambient temperature may be used to
cool the lens forming composition. When a xenon flash lamp is used,
the pulses of light generally have a duration of much less than
about one second and considerably less radiative heat tends to be
transferred to the lens forming composition compared to curing
methods employing other activating light sources. Thus, the reduced
heat imparted to the lens forming composition may allow for air at
ambient temperature to remove sufficient heat of exotherm to
substantially inhibit premature release and/or cracking of the
lens.
[0430] In an embodiment, a xenon source is used to direct first
activating light rays toward the first and second mold members to
the point that a temperature increase is measured and/or the lens
forming composition begins to or forms a gel. It is preferred that
the gel is formed with less than 15 pulses of radiation, and more
preferably with less than about 5 pulses. It is preferred that the
gel is formed before the total time to which the composition has
been exposed to the pulses exceeds about {fraction (1/10)} or
{fraction (1/100)} of a second.
[0431] In an embodiment, a reflecting device is preferably employed
in conjunction with the xenon light source. The reflecting device
is positioned behind the flash source and preferably allows an even
distribution of activating light rays from the center of the
composition to the edge of the composition.
[0432] In an embodiment, a xenon light flash lamp is preferably
used to apply a plurality of activating light pulses to the lens
forming composition to cure it to an eyeglass lens in a time period
of less than 30 minutes, or more preferably, less than 20 or 15
minutes.
[0433] The use of a xenon light source also may allow the formation
of lenses over a wider range of diopters. Higher power lenses
exhibit greatest thinnest to thickest region ratios, meaning that
more shrinkage-induced stress may be created, causing greater mold
flexure and thus increased tendency for premature release. Higher
power lenses also possess thicker regions. Portions of lens forming
material within these thicker regions may receive less light than
regions closer to the mold surfaces. Continuous irradiation lens
forming techniques typically require the use of relatively low
light intensities to control the heat generated during curing. The
relatively low light intensities used tends to result in a long,
slow gellation period. Optical distortions tend to be created when
one portion of the lens is cured at a different rate than another
portion. Methods characterized by non-uniform curing are typically
poorly suited for the production of relatively high power lenses,
since the deeper regions (e.g., regions within a thick portion of a
lens) tend to gel at a slower rate than regions closer to the mold
surfaces.
[0434] The relatively high intensity attainable with the xenon
source may allow deeper penetration into, and/or saturation of, the
lens forming material, thereby allowing uniform curing of thicker
lenses than in conventional radiation-initiated curing. More
uniform gelation may occur when the lens forming material is dosed
with a high intensity pulse of activating light and then subjected
to decreased activating light or darkness as the reaction proceeds
without activating radiation. Lenses having a diopter of between
about +5.0 and about -6.0 and greater may be cured. It is believed
that light distribution across the sample is less critical when
curing and especially when gelation is induced with relatively high
intensity light. The lens forming material may be capable of
absorbing an amount of energy per time that is below that delivered
during a relatively high intensity pulse. The lens forming material
may be "oversaturated" with respect to the light delivered via a
high intensity flash source. In an embodiment, the xenon source is
preferably used to cure a lens having a diopter between about -4.0
and about -6.0. In an embodiment, the xenon source is preferably
used to cure a lens having a diopter between about +2.0 and about
+4.0.
[0435] The methods disclosed herein allow curing of high-mass
semi-finished lens blanks from the same material used to cure
cast-to-finish lenses. Both are considered to be "eyeglass lenses"
for the purposes of this patent. These methods may also be used to
cure a variety of other lens forming materials. These methods have
been successfully used to make cast-to-finish lenses in addition to
semi-finished lenses.
[0436] 6. Improved Lens Curing Process
[0437] When casting an eyeglass lens with activating light, the
gelation pattern of the lens forming composition may affect the
resultant optical quality of the lens. If there are localized
discontinuities in the light intensities received by the monomer
contained in the casting cavity during the early stages of the
polymerization process, optical distortions may be seen in the
finished product. Higher power lenses are, by definition, thicker
in certain regions than relatively lower power lenses of the same
diameter. The layers of a lens closest to the mold faces of the
casting cavity tend to receive a higher light intensity than the
deeper layers because the lens forming composition absorbs some of
the incident light. This causes the onset of polymerization to be
delayed in the deeper layers relative to the outer layers, which
may cause optical distortions in the finished product. It is
believed that concurrent with this differential curing rate, there
is a difference in the rate of exothermic heat generation,
specifically, the deeper regions will begin to generate heat after
the outer regions in the cavity have already cured and the
effectiveness of the heat removal may be impaired, contributing to
optical waves and distortions in the finished product. This
phenomena is particularly observable in high powered positive
lenses due to the magnification of such defects.
[0438] In an embodiment, the lens forming composition contained
within the casting cavity is exposed to relatively high intensity
activating light for a time period sufficient to initialize the
reaction. Irradiation is preferably terminated before the
polymerization of the lens forming composition proceeds far enough
to generate a substantial amount of heat. This initial relatively
high intensity dose preferably substantially uniformly gels the
material within the casting cavity such that the difference in the
rate of reaction between the inner and outer layers of the lens
being cured is preferably reduced, thereby eliminating the waves
and distortions often encountered when using continuous low
intensity irradiation to initialize the reaction, particularly with
high dioptric power positive lenses.
[0439] In an embodiment, the relatively high intensity dose of
activating light is preferably applied to the lens forming
composition in the form of pulses. The pulses preferably have a
duration of less than about 10 seconds, preferably less than about
5 seconds, and more preferably less than about 3 seconds. The
pulses preferably have an intensity of at least about 10
milliwatts/cm.sup.2, more preferably at least about 100
milliwatts/cm.sup.2, and more preferably still between about 150
milliwatts/cm.sup.2 and about 250 milliwatts/cm.sup.2. It is
preferred that substantially all of the lens forming composition
forms into a gel after the initial application of the relatively
high intensity activating light. In an embodiment, no more than an
insubstantial amount of heat is generated by exothermic reaction of
the lens forming composition during the initial application of the
relatively high intensity activating light.
[0440] Subsequent to this initial high intensity dose, a second
irradiation step may be performed in which the material contained
within the casting cell is preferably irradiated for a relatively
longer time at a relatively lower intensity while cool fluid is
directed at the non-casting surface of at least one of the molds
forming the cavity. The cooling fluid preferably removes the
exothermic heat generated by the polymerization of the lens forming
composition. If the intensity of the activating light is too great
during this second irradiation step, the rate of heat generation
will tend to be too rapid and the lens may release prematurely from
the casting face of the mold and/or crack. Similarly, should the
rate of heat removal from the lens forming composition be too slow,
the lens may release prematurely and/or crack. It is preferred that
the mold/gasket assembly containing the lens forming composition be
placed within the cooling environment as shortly after the initial
dose of activating light as possible.
[0441] In an embodiment, the activating light applied to the lens
forming composition during the second irradiation step is
preferably less than about 350 microwatts/cm.sup.2, more preferably
less than about 150 microwatts/cm.sup.2, and more preferably still
between about 90 microwatts/cm.sup.2 and about 100
microwatts/cm.sup.2. During the second irradiation step, the
activating light may be applied to the lens forming composition
continuously or in pulses. A translucent high density polyethylene
plate may be positioned between the activating light generator and
at least one of the mold members to reduce the intensity of the
activating light to within a preferred range.
[0442] In an embodiment, relatively high intensity activating light
is preferably applied to the lens curing composition in a third
irradiation step to post-cure the lens subsequent to the second
relatively low intensity irradiation step. In the third irradiation
step, pulses of activating light are preferably directed toward the
lens forming composition, although the composition may be
continuously irradiated instead. The pulses preferably have an
intensity of at least about 10 milliwatts/cm.sup.2, more preferably
at least about 100 milliwatts/cm.sup.2, and more preferably still
between about 100 milliwatts/cm.sup.2 and about 150
milliwatts/cm.sup.2.
[0443] Each of the above-mentioned irradiation steps is preferably
performed by directing the activating light through each of the
first and second mold members. The eyeglass lens is preferably
cured in a total time of less than 30 minutes and is preferably
free of cracks, striations, distortions, haziness, and
yellowness.
[0444] It is believed that the above-described methods enable the
production of whole lenses in prescription ranges beyond those
currently attainable with continuous low intensity irradiation. The
method may be practiced in the curing of relatively high or low
power lenses with a reduced incidence of optical distortions in the
finished lens as compared to conventional methods. It is to be
understood that the above-described methods may be used
independently or combined with the methods and apparatus of
preferred embodiments described above in the previous sections.
[0445] 7. Improved Scratch Resistant Lens Formation Process
[0446] The "in-mold" method involves forming a scratch resistant
coating over an eyeglass lens by placing the liquid coating in a
mold and subsequently curing it. The in-mold method may be
advantageous to "out-of-mold" methods since the in-mold method
exhibits less occurrences of coating defects manifested as
irregularities on the anterior surface of the coating. Using the
in-mold method produces a scratch resistant coating that replicates
the topography and smoothness of the mold casting face. However, a
problem encountered when using conventional in-mold scratch
resistant coatings is that minute "pinholes" often form in the
coating. It is believed that the pinholes may be caused by either
contaminants on the mold, airborne particles falling on the coating
before it is cured, or bubbles formed during the application of the
coating which burst afterwards. The formation of such pinholes is
especially prevalent when using a flat-top bifocal mold, such as
the one depicted in FIG. 29. As illustrated, the segment line 454
of a bifocal segment 452 below the main surface 456 of the mold
reduces the smoothness of the casting face. When a coating is
spin-coated over the mold face, this indentation may become an
obstacle to the even flow of the casting face. The pinhole defects
may be a problem in tinted lenses because the dye used to tint a
lens may penetrate through the pinholes, resulting in a tiny speck
of dye visible in the lens.
[0447] According to an embodiment, a first coating composition
(i.e., a polymerizable "primer" material) is preferably passed
through a filter and then placed within a mold member having a
casting face and a non-casting face. The first coating composition
preferably contains a photoinitiator to make it curable upon
exposure to activating light. The mold member may then be spun so
that the first composition becomes distributed over the casting
face. The mold member may be rotated about a substantially vertical
axis at a speed between about 750 and about 1500 revolutions per
minute, preferably between about 800 and about 1000 revolutions per
minute, more preferably at about 900 revolutions per minute.
Further, a dispensing device may be used to direct an additional
amount of the first composition onto the casting face while the
mold member is spinning. The dispensing device preferably moves
from the center of the mold member to an edge of the mold member so
that the additional amount is preferably directed along a radius of
the mold member. Activating light is preferably directed at the
mold member to cure at least a portion of the first
composition.
[0448] A second coating composition may then be placed upon the
first composition in the mold member. The second coating is also
preferably curable when exposed to activating light because it
contains a photoinitiator. The mold member is preferably spun to
distribute the second coating composition over the cured portion of
the first coating composition. The mold member may also be spun
simultaneously while adding the second composition to the mold
member. Activating light is then preferably directed at the mold
member to simultaneously cure at least a portion of the second
coating composition and form a transparent combination coat having
both coating compositions. The combination coat is preferably a
substantially scratch-resistant coating. The mold member may then
be assembled with a second mold member by positioning a gasket
between the members to seal them. Therefore, a mold having a cavity
shared by the original two mold members is formed. An edge of the
gasket may be displaced to insert a lens-forming composition into
the cavity. The combination coat and the lens-forming material
preferably adhere well to each other. This lens-forming composition
preferably comprises a photoinitiator and is preferably cured using
activating light. Air which preferably has a temperature below
ambient temperature may be directed toward a non-casting face of
the second mold member to cool the lens-forming composition while
it is being cured.
[0449] The primer coat preferably comprises a mixture of high
viscosity monomers, a low viscosity, low flashpoint organic
solvent, and a suitable photoinitiator system. The solvent may make
up more than about 80% of the mixture, preferably about 93% to 96%.
This mixture preferably has low viscosity and preferably covers any
surface irregularity during the spin application, for example the
segment line of a flat-top bifocal mold. The low flashpoint solvent
preferably evaporates off relatively quickly, leaving a thin layer
of high viscosity monomer, containing photoinitiator, which coats
the casting face of the mold. The cured primer coat is preferably
soft to allow it to adhere well to the glass mold face. Since the
primer coat is soft, it may not possess scratch resistant
characteristics. However, applying a high scratch resistance hard
coating (i.e., the second coating composition) to the primer coat
preferably results in a scratch resistant combination coat. The
hard coat preferably contains a solvent which evaporates when the
mold member is rotated to distribute the hard coating over the
primer coat.
[0450] In general, the ideal primer material preferably possesses
the following characteristics: exhibits chemical stability at
normal storage conditions (e.g., at room temperature and in the
absence of activating light); flows well on an irregular surface,
especially over a flat-top bifocal segment; when cured with a
specified activating light dose, leaves a crack-free coating, with
a high double bond conversion (approximately greater than 80%);
maintains adhesion with the mold face through the lens forming
curing cycle, especially the segment part of the flat-top bifocal
mold; and is chemically compatible with the hard coat that is
subsequently applied on top of it (e.g., forms an optically clear
combination coat). Even though pinhole defects may be present in
either the primer coat or the hard coat, it is highly unlikely that
defects in one coat would coincide with defects of another coat.
Each coat preferably covers the holes of the other coat, resulting
in less pinholes in the combination coat. Thus, the finished
in-mold coated lens may be tinted using dye without problems
created by pinholes. It is also preferably free of cracks,
yellowness, haziness, and distortions.
[0451] In an embodiment, the gasket between the first mold member
and the second mold member may be removed after a portion of the
lens-forming material has been cured. The removal of the gasket
preferably exposes an edge of the lens. An oxygen barrier having a
photoinitiator may be placed around the exposed edge of the lens,
wherein the oxygen barrier photoinitiator is preferably near an
uncured portion of the lens-forming composition. Additional
activating light rays may then be directed towards the tens to
cause at least a portion of the oxygen barrier photoinitiator to
initiate reaction of the lens-forming material. The oxygen barrier
preferably prevents oxygen from contacting at least a portion of
the lens forming composition during exposure of the lens to the
activating rays.
[0452] According to one embodiment, a substantially solid
conductive heat source is preferably applied to one of the mold
members. Heat may be conductively transferred from the heat source
to a face of the mold member. Further, the heat may be conductively
transferred through the mold member to the face of the lens.
[0453] 8. Method for Forming a Plastic Lens Containing
Ultraviolet/Visible Light Absorbing Compounds.
[0454] Materials (hereinafter referred to as "ultraviolet/visible
light absorbing compounds") that absorb various degrees of
ultraviolet/visible light may be used in an eyeglass lens to
inhibit ultraviolet/visible light from being transmitted through
the eyeglass lens. Such an eyeglass lens advantageously inhibits
ultraviolet/visible light from being transmitted to the eye of a
user wearing the lens. Curing of an eyeglass lens using activating
light to initiate the polymerization of a lens forming composition
generally requires that the composition exhibit a high degree of
activating light transmissibility so that the activating radiation
may penetrate to the deeper regions of the lens cavity. Otherwise
the resulting cast lens may possess optical aberrations and
distortions. The cast lens may also contain layers of cured
material in the regions closest to the transparent mold faces,
sandwiching inner layers which may be either incompletely cured,
gelled, barely gelled, or even liquid. Often, when even small
amounts of ultraviolet/visible light absorbing compounds of the
types well known in the art are added to a normally activating
light curable lens forming composition, substantially the entire
amount of lens forming composition contained within the lens cavity
may remain liquid in the presence of activating radiation.
[0455] Photochromic pigments which have utility for photochromic
eyeglass lenses absorb ultraviolet/visible light strongly and
change from an unactivated state to an activated state when exposed
to ultraviolet/visible light. The presence of photochromic
pigments, as well as other ultraviolet/visible light absorbing
compounds within a lens forming composition, generally does not
permit enough activating radiation to penetrate into the depths of
the lens cavity sufficient to cause photoinitiators to break down
and initiate polymerization of the lens forming composition. Thus,
it may be difficult to cure a lens forming composition containing
ultraviolet/visible light absorbing compounds using activating
light. It is therefore desirable to provide a method for using
activating light to initiate polymerization of an eyeglass lens
forming monomer which contains ultraviolet/visible light absorbing
compounds, in spite of the high activating light absorption
characteristics of the ultraviolet/visible light absorbing
compounds. Examples of such ultraviolet/visible light absorbing
compounds other than photochromic pigments are fixed dyes and
colorless additives.
[0456] In an embodiment, an ophthalmic eyeglass lens may be made
from a lens forming composition comprising a monomer, an
ultraviolet/visible light absorbing compound, an photoinitiator,
and a co-initiator. Examples of these compounds are listed in the
section "Lens Forming Compositions Including Ultraviolet/Visible
Light Absorbing Materials". The lens forming composition, in liquid
form, is preferably placed in a mold cavity defined by a first mold
member and a second mold member. It is believed that activating
light, which is directed toward the mold members to activate the
photoinitiator, causes the photoinitiator to form a polymer chain
radical. The polymer chain radical preferably reacts with the
co-initiator more readily than with the monomer. The co-initiator
may react with a fragment or an active species of either the
photoinitiator or the polymer chain radical to produce a monomer
initiating species in the regions of the lens cavity where the
level of activating light is either relatively low or not
present.
[0457] The co-initiator is preferably activated only in the
presence of the photoinitiator. Further, without the co-initiator,
the photoinitiator may exclusively be activated near the surface of
the lens forming composition but not within the middle portion of
the composition. Therefore, using a suitable photoinitiator
combined with a co-initiator permits polymerization of the lens
forming composition to proceed through the depths of the lens
cavity. A cured, clear, aberration free lens is preferably formed
in less than about 30 minutes, more preferably in less than about
10 minutes. The lens, when exposed to ultraviolet/visible light
preferably inhibits at least a portion of the ultraviolet/visible
light from being transmitted through the lens that is preferably
formed. A lens that permits no ultraviolet light from passing
through the lens (at least with respect to certain ultraviolet
wavelengths) is more preferred.
[0458] The identity of the major polymerizable components of the
lens forming composition tends to affect the optimal curing
process. It is anticipated that the identity of the
ultraviolet/visible light absorbing compound present in the monomer
or blend of monomers may affect the optimal
photoinitiator/co-initiator system used as well as the optimal
curing process used to initiate polymerization. Also, varying the
identities or the proportions of the monomer(s) in the lens forming
composition may require adjustments to various production process
variables including, but not limited to, exposure times, exposure
intensities, cooling times and temperatures, activating light and
thermal postcure procedures and the like. For example, compositions
comprising relatively slow reacting monomers, such as bisphenol A
bis allyl carbonate or hexanediol dimethacrylate, or compositions
comprising relatively higher proportions of such monomers may
require either longer exposure times, higher intensities, or both.
It is postulated that increasing the amount of either fast reacting
monomer or the initiator levels present in a system will require
reduced exposure times, more rigidly controlled light doses, and
more efficient exothermic heat removal.
[0459] Exothermic reactions may occur during the curing process of
the lens forming composition. The thicker portions of the lens
forming composition may generate more heat than the thinner
portions of the composition as a result of the exothermic reactions
taking place. It is believed that the speed of reaction in the
thicker sections is slower than in the thinner sections. Thus, in a
positive lens a "donut effect" may occur in which the relatively
thin outer portion of the lens forming composition reaches its
fully cured state before the relatively thick inner portion of the
lens forming composition. Conversely, in a negative lens the
relatively thin inner portion of the lens forming composition may
reach its fully cured state before the relatively thick outer
portion of the lens forming composition.
[0460] After the lens forming composition is preferably loaded into
a mold assembly, the mold assembly is preferably irradiated with
activating light at an appropriate intensity and duration.
Typically, the intensity and duration of activating light required
to produce a lens containing ultraviolet/visible light absorbers is
preferably significantly higher than the intensity and duration of
light required for forming non-ultraviolet/visible light absorbing
lenses. The mold assembly may also require multiple doses for
curing. This may require a different apparatus and/or setup from
that used to form non-UV absorbing lenses.
[0461] In one embodiment, an apparatus may be capable of forming
clear, colored, or photochromic lenses without significantly
altering the apparatus. In order to achieve this the lens forming
composition will preferably include ultraviolet/visible light
absorbers. By placing ultraviolet/visible light absorbers in a
clear non-photochromic lens forming composition, a clear lens may
be obtained under similar conditions to those used for colored and
photochromic lenses. Thus, the addition of ultraviolet/visible
light absorbers to a non-photochromic lens forming composition,
allows both photochromic and non-photochromic lens forming
compositions to be cured using the same apparatus and similar
procedures. An added advantage, is that the produced clear lenses
provide additional ultraviolet/visible light protection to the user
that may not be present in clear lenses formed without
ultraviolet/visible light absorbers. In this manner, plastic lenses
may be formed which exhibit many of the same properties as glass
lenses however, the plastic lenses may be produced more rapidly, at
lower cost, and have a weight significantly less than their glass
counterparts.
[0462] 9. Actinic Light Initiated Polymerization
Ultraviolet/Visible Light Absorbing Compositions.
[0463] Curing of an eyeglass lens using activating light to
initiate the polymerization of a lens forming composition generally
requires that the composition exhibit a high degree of activating
light transmissibility so that the activating light may penetrate
to the deeper regions of the lens cavity. Otherwise the resulting
cast lens may possess optical aberrations and distortions. The cast
lens may also contain layers of cured material in the regions
closest to the transparent mold faces, sandwiching inner layers
which may be either incompletely cured, gelled, barely gelled, or
even liquid. Often, when even small amounts of activating light
absorbing compounds have been added to a normally curable lens
forming composition, substantially the entire amount of lens
forming composition contained within the lens cavity may remain
liquid in the presence of activating light.
[0464] Photochromic pigments that have utility for photochromic
eyeglass lenses typically absorb activating light strongly and
change from an inactivated state to an activated state when exposed
to activating light. The presence of photochromic pigments, as well
as other activating light absorbing compounds within a lens forming
composition, generally does not permit enough activating radiation
to penetrate into the depths of the lens cavity sufficient to cause
photoinitiators to break down and initiate polymerization of the
lens forming composition. Examples of such activating light
absorbing compounds other than photochromic pigments are fixed dyes
and colorless additives.
[0465] It is therefore difficult to cure a lens forming composition
containing activating light absorbing compounds using activating
light. One solution to this problem involves the use of a
co-initiator. By using a co-initiator, activating light may be used
to initiate the polymerization reaction. It is believed that
activating light that is directed toward the mold members may cause
the photoinitiator to form a polymer chain radical. The polymer
chain radical preferably reacts with the co-initiator more readily
than with the monomer. The co-initiator may react with a fragment
or an active species of either the photoinitiator or the polymer
chain radical to produce a monomer initiating species in the
regions of the lens cavity where the level of activating light is
either relatively low or not present. It is therefore desirable to
provide a method for polymerizing an eyeglass lens forming
composition that contains light absorbing compounds by using
activating light having a wavelength that is not absorbed by the
light absorbing compounds, thus avoiding the need for a
co-initiator.
[0466] In an embodiment, an ophthalmic eyeglass lens may be made
from a lens forming composition comprising a monomer, a light
absorbing compound, and a photoinitiator, by irradiation of the
lens forming composition with activating light. As used herein
"activating light" means light that may effect a chemical change.
Activating light may include ultraviolet light, actinic light,
visible light or infrared light. Generally any wavelength of light
capable of effecting a chemical change may be classified as
activating. Chemical changes may be manifested in a number of
forms. A chemical change may include, but is not limited to, any
chemical reaction which causes a polymerization to take place.
Preferably the chemical change causes the formation of a initiator
species within the lens forming composition, the initiator species
being capable of initiating a chemical polymerization reaction.
[0467] The lens forming composition, in liquid form, is preferably
placed in a mold cavity defined by a first mold member and a second
mold member. It is believed that activating light, when directed
toward and through the mold members to activate the photoinitiator,
causes the photoinitiator to form a polymer chain radical. The
polymer chain radical may react with a fragment or an active
species of either photoinitiator or the polymer chain radical to
produce a monomer initiating species in other regions of the lens
cavity.
[0468] The use of activating light of the appropriate wavelength
preferably prevents the lens from darkening during the curing
process. Herein, "darkening" means becoming at least partially
non-transparent to the incoming activating light such that the
activating light may not significantly penetrate the lens forming
composition. Photochromic compounds may cause such darkening.
Ultraviolet/visible light absorbing compounds present in the lens
forming composition may prevent activating light having a
wavelength substantially below about 380 nm from penetrating into
the lens forming composition. When treated with activating light
containing light with wavelengths in the ultraviolet region, e.g.
light with wavelengths below about 380 nm, the ultraviolet/visible
light absorbing compounds may darken, preventing further
ultraviolet activating light from penetrating the lens forming
composition. The darkening of the lens forming composition may also
prevent non-ultraviolet activating light from penetrating the
composition. This darkening effect may prevent activating light of
any wavelength from initiating the polymerization reaction
throughout the lens forming composition.
[0469] When the ultraviolet/visible light absorbing compounds
absorb in the ultraviolet region, activating light having a
wavelength above about 380 nm (e.g., actinic light) may be used to
prevent the darkening effect. Because the wavelength of the
activating light is substantially above the wavelength at which the
ultraviolet/visible light absorbing compounds absorb, the darkening
effect may be avoided. Additionally, activating light with a
wavelength above about 380 nm may be used to initiate the
polymerization of the lens forming material. By the use of such
activating light an eyeglass lens containing ultraviolet/visible
light absorbing compounds may, in some circumstances, be formed
without the use of a co-initiator.
[0470] In an embodiment, the above-described lens forming
composition, where the ultraviolet/visible light absorbing compound
absorbs, predominantly, ultraviolet light, may be treated with
activating light having a wavelength above about 380 nm to activate
the photoinitiator. Preferably, activating light having a
wavelength substantially between about 380 nm to 490 nm is used. By
using activating light above about 380 nm the darkening effect
caused by the ultraviolet/visible light absorbing compounds may be
avoided. The activating light may penetrate into the lens forming
composition, initiating the polymerization reaction throughout the
composition. A filter which blocks light having a wavelength that
is substantially below about 380 nm may be used to prevent the
ultraviolet/visible light absorbing compounds from darkening.
[0471] The use of activating light permits polymerization of the
lens forming composition to proceed through the depths of the lens
cavity. A cured, clear, aberration free lens is preferably formed
in less than about 30-60 minutes, more preferably in less than
about 20 minutes. As used herein a "clear lens" means a lens that
transmits visible light without scattering so that objects beyond
the lens may be seen clearly. As used herein "aberration" means the
failure of a lens to produce point-to-point correspondence between
an object and its image. The lens, when exposed to
ultraviolet/visible light, preferably inhibits at least a portion
of the ultraviolet/visible light from being transmitted through the
lens. In this manner the eye may be protected from certain light. A
lens that permits no ultraviolet/visible light from passing through
the lens (at least with respect to certain wavelengths) is more
preferred.
[0472] In an embodiment, the lens forming composition that contains
an ultraviolet/visible light absorbing compound may be cured with
an activating light. Preferably, the activating light has a
wavelength substantially above about 380 nm. The lens forming
composition may be cured by exposing the composition to activating
light multiple times. Alternatively, the lens forming composition
may be cured by exposing the composition to a plurality of
activating light pulses, at least one of the pulses having a
duration of less than about one second (more preferably less than
about 0.1 seconds, and more preferably between 0.1 and 0.001
seconds). Preferably, all activating light directed toward the mold
members is at a wavelength between about 380 nm to 490 nm. The
previously described embodiments which describe various methods and
compositions for forming eyeglass lenses may also be utilized to
form the eyeglass lens hereof, by replacing the ultraviolet light
in these examples with activating light having a wavelength
substantially greater than about 380 nm.
[0473] In an embodiment, the activating light may be generated from
a fluorescent lamp. The fluorescent lamp is preferably used to
direct activating light rays toward at least one of the mold
members. At least one and preferably two fluorescent light sources,
with strong emission spectra in the 380 to 490 nm region may be
used. When two light sources are used, they are preferably
positioned on opposite sides of the mold cavity. A fluorescent lamp
emitting activating light with the described wavelengths is
commercially available from Philips Electronics as model
TLD-15W/03.
[0474] Preferably, three or four fluorescent lamps may be
positioned to provide substantially uniform radiation over the
entire surface of the mold assembly to be cured. The activating
light source may be turned on and off quickly between exposures. A
flasher ballast may be used for this function. A flasher ballast
may operate in a standby mode wherein a low current is supplied to
the lamp filaments to keep the filaments warm and thereby reduce
the strike time of the lamp. Such a ballast is commercially
available from Magnatek, Inc of Bridgeport, Conn. Alternately, the
light source may employ a shutter system to block the light between
doses. This shutter system is preferably controlled by a
micro-processor based control system in order to provide the
necessary doses of light. A feedback loop may be used to control
the light intensity so that intensity fluctuations due to
environmental variables (e.g. lamp temperature) and lamp aging may
be minimized. A light sensor may be incorporated into the control
system to minimize variances in dose for a given exposure time.
[0475] The identity of the major polymerizable components of the
lens forming composition tends to affect the optimal curing
process. It is anticipated that the identity of the light absorbing
compound present in the monomer or blend of monomers may affect the
optimal photoinitiator system used as well as the optimal curing
process used to initiate polymerization. Also, varying the
identities or the proportions of the monomer(s) in the lens forming
composition may require adjustments to various production process
variables including, but not limited to, exposure times, exposure
intensities, cooling times and temperatures, postcure procedures
and the like. For example, compositions including relatively slow
reacting monomers, such as bisphenol A bis allyl carbonate or
hexanediol dimethacrylate, or compositions including relatively
higher proportions of such monomers may require either longer
exposure times, higher intensities, or both. It is postulated that
increasing the amount of either fast reacting monomer or the
initiator levels present in a system will require reduced exposure
times, more rigidly controlled light doses, and more efficient
exothermic heat removal.
[0476] Preferably, the monomers selected as components of the lens
forming composition are capable of dissolving the light absorbing
compounds added to them. As used herein "dissolving" means being
substantially homogeneously mixed. For example, monomers may be
selected from a group including polyether (allyl carbonate)
monomers, multi-functional acrylate monomers, and multi-functional
methacrylic monomers for use in an ultraviolet/visible light
absorbing lens forming composition.
[0477] In an embodiment, the mixture of monomers, previously
described as PRO-629, may be blended together before addition of
other components required to make the lens forming composition.
This blend of monomers is preferably used as the basis for a lens
forming composition to which ultraviolet/visible light absorbing
compounds are added.
[0478] A polymerization inhibitor may be added to the monomer
mixture at relatively low levels to inhibit polymerization of the
monomer at inappropriate times (e.g., during storage). Preferably
about 0 to 50 ppm of monomethylether hydroquinone (MEHQ) are added
to the monomer mixture. It is also preferred that the acidity of
the monomer mixture be as low as possible. Preferably less than
about 100 ppm residual acrylic acid exists in the mixture. It is
also preferred that the water content of the monomer mixture be
relatively low, preferably less than about 0.15 percent.
[0479] Photoinitiators which have utility in the present method
have been described in previous embodiments. Ultraviolet/visible
light absorbing compounds which may be added to a normally
ultraviolet/visible light transmissible lens forming composition
have also been described in previous embodiments. The quantity of
photochromic pigments present in the lens forming composition is
preferably sufficient to provide observable photochromic effect.
The amount of photochromic pigments present in the lens forming
composition may widely range from about 1 ppm by weight to 1-5% by
weight. In preferred compositions, the photochromic pigments are
present in ranges from about 30 ppm to 2000 ppm. In the more
preferred compositions, the photochromic pigments are present in
ranges from about 150 ppm to 1000 ppm. The concentration may be
adjusted depending upon the thickness of the lens being produced to
obtain optimal visible light absorption characteristics.
[0480] In another embodiment co-initiators may be added to the lens
forming composition. As described previously, such compositions may
aid the polymerization of the lens forming composition by
interacting with the photoinitiator such that the composition
polymerizes in a substantially uniform manner. It is anticipated
that the optimal amount of the initiators is where the total amount
of both initiators are minimized subject to the constraint of
complete polymerization and production of a rigid, aberration free
lens. The relative proportions of the photoinitiator to the
co-initiator may be optimized by experimentation. For example, an
ultraviolet/visible light absorptive lens forming composition that
includes a photoinitiator with no co-initiator may be cured. If
waves and distortions are observed in the resulting lens, a
co-initiator may then be added to the lens forming composition by
increasing amounts until a lens having the best optical properties
is formed. It is anticipated that excess co-initiator in the lens
forming composition should be avoided to inhibit problems of too
rapid polymerization, yellowing of the lens, and migration of
residual, unreacted co-initiator to the surface of the finished
lens.
[0481] In an embodiment, hindered amine light stabilizers may be
added to the lens forming composition. It is believed that these
materials act to reduce the rate of degradation of the cured
polymer caused by exposure to ultraviolet light by deactivating
harmful polymer radicals. These compounds may be effective in
terminating oxygen and carbon free radicals, and thus interfering
with the different stages of auto-oxidation and photo-degradation.
Preferably, more than one monomer and more than one initiator are
used in a lens forming composition to ensure that the initial
polymerization of the lens forming composition with activating
light does not occur over too short a period of time. The use of
such a lens forming composition may allow greater control over the
gel formation, resulting in better control of the optical quality
of the lens.
[0482] An eyeglass lens formed using the lens forming compositions
described may be applicable for use as a prescription lens and for
a non-prescription lens. Particularly, such a lens may be used in
sunglasses. Advantageously, photochromic sunglass lenses would
remain light enough in color to allow a user to see through them
clearly while at the same time prohibiting ultraviolet/visible
light from passing through the lenses. In one embodiment, a
background dye may be added to the photochromic lens to make the
lens appear to be a dark shade of color at all times like typical
sunglasses.
SPECIFIC EXAMPLES
[0483] The following examples are included to demonstrate
embodiments of the invention. Those of skill in the art, in light
of the present disclosure, should appreciate that many changes may
be made in the specific examples that are disclosed and still
obtain a like or similar result without departing from the spirit
and scope of the invention.
Example 1
Formation of a Plastic Lens by Curing With Activating Light
[0484]
7 Formulation: 17% Bisphenol A bis(allyl carbonate) 10% 1,6
Hexanediol dimethacrylate 20% Trimethylolpropane triacrylate 21%
Tetraethyleneglycol diacrylate 32% Tripropyleneglycol diacrylate
0.012% 1 Hydroxycyclohexyl phenyl ketone 0.048 Methyl
benzoylformate <10 ppm Hydroquinone &
Methylethylhydroquinone
[0485] Hydroquinone and Methylethylhydroquinone were stabilizers
present in some of the diacrylate and/or triacrylate compounds
obtained from Sartomer. Preferably the amount of stabilizers is
minimized since the stabilizers affect the rate and amount of
curing. If larger amounts of stabilizers are added, then generally
larger amounts of photoinitiators must also be added.
[0486] Light Condition: mW/cm.sup.2 measured at plane of sample
with Spectroline DM 365N Meter from Spectronics Corp. (Westbury,
N.Y.)
8 Center Edge Top: 0.233 0.299 Bottom: 0.217 0.248
[0487] Air Flow: 9.6 standard cubic feet per minute ("CFM") per
manifold--19.2 CFM total on sample
[0488] Air Temperature: 4.4 degrees Centigrade
[0489] Molds: 80 mm diameter Corning #8092 glass
9 Radius Thickness Concave: 170.59 2.7 Convex: 62.17 5.4
[0490] Gasket: General Electric SE6035 silicone rubber with a 3 mm
thick lateral lip dimension and a vertical lip dimension sufficient
to provide an initial cavity center thickness of 2.2 mm.
[0491] Filling: The molds were cleaned and assembled into the
gasket. The mold/gasket assembly was then temporarily positioned on
a fixture which held the two molds pressed against the gasket lip
with about 1 kg. of pressure. The upper edge of the gasket was
peeled back to allow about 27.4 grams of the monomer blend to be
charged into the cavity. The upper edge of the gasket was then
eased back into place and the excess monomer was vacuumed out with
a small aspirating device. It is preferable to avoid having monomer
drip onto the noncasting surface of the mold because a drop tends
to cause the activating light to become locally focused and may
cause an optical distortion in the final product.
[0492] Curing: The sample was irradiated for fifteen minutes under
the above conditions and removed from the lens curing unit. The
molds were separated from the cured lens by applying a sharp impact
to the junction of the lens and the convex mold. The sample was
then postcured at 110.degree. C. in the post-cure unit for an
additional ten minutes, removed and allowed to cool to room
temperature.
[0493] Results: The resulting lens measured 72 mm in diameter, with
a central thickness of 2.0 mm, and an edge thickness of 9.2 mm. The
focusing power measured .about.5.05 diopter. The lens was water
clear ("water-white"), showed negligible haze, exhibited total
visible light transmission of about 94%, and gave good overall
optics. The Shore D hardness was about 80. The sample withstood the
impact of a 1 inch steel ball dropped from fifty inches in
accordance with ANSI 280.1-1987, 4.6.4 test procedures.
Example 2
Oxygen Barrier Example #1
[0494] A liquid lens forming composition was initially cured as in
a process and apparatus similar to that specified in Example 1. The
composition was substantially the same as specified in Example 1,
with the exception that hydroquinone was absent, the concentration
of methylethylhydroquinone was about 25-45 ppm, the concentration
of 1-hydroxycyclohexyl phenyl ketone was 0.017 percent, and the
concentration of methylbenzoylformate was 0.068 percent. The
composition underwent the initial 15 minute cure under the "1st
activating light." The apparatus was substantially the same as
described for the above Example 1, with the following
exceptions:
[0495] 1. The air flowrate on each side of the lens mold assembly
was estimated to be about 18-20 cubic feet per minute.
[0496] 2. The air flowrate in and out of the chamber surrounding
the lights was varied in accordance with the surface temperature of
the lights. The air flowrate was varied in an effort to keep the
temperature on the surface of one of the lights between
104.5.degree. F. and 105.degree. F.
[0497] 3. The activating light output was controlled to a set point
by varying the power sent to the lights as the output of the lights
varied.
[0498] 4. Frosted glass was placed between the lights and the
filters used to vary the intensity of the activating light across
the face of the molds. Preferably the glass was frosted on both
sides. The frosted glass acts as a diffuser between the lights and
these filters. This frosted glass tended to yield better results if
it was placed at least about 2 mm from the filter, more preferably
about 10-15 mm, more preferably still about 12 mm, from the filter.
Frosted glass was found to dampen the effect of the filters. For
instance, the presence of the frosted glass reduced the systems'
ability to produce different lens powers by varying the light (see
Example 1 and FIG. 1).
[0499] After initial cure, the lens mold assembly was removed from
the curing chamber. The lens mold assembly included a lens
surrounded by a front mold, a back mold, and a gasket between the
front and back molds (see, e.g., the assembly in FIG. 11).
[0500] At this point the protocol in Example 1 stated that the lens
was demolded (see above). While demolding at this point is
possible, as stated above, generally some liquid lens forming
composition remained, especially in areas of the lens proximate the
gasket. Therefore, the lens was not demolded as stated in Example
1. Instead, the gasket was removed, liquid lens forming composition
was wiped off the edges of the lens, and a layer of oxygen barrier
(Parafilm M) with photoinitiator was wrapped around the edges of
the lens while the lens was still between the molds. The Parafilm M
was wrapped tightly around the edges of the lens and then stretched
so that it would adhere to the lens and molds (i.e., in a manner
similar to that of Saran wrap). The lens mold assembly was then
placed in the post-cure unit so that the back face of the lens
(while between the molds) could then be exposed to additional
activating light.
[0501] This second activating light was at a substantially higher
intensity than the initial cure light, which was directed at an
intensity of less than 10 mW/cm.sup.2. The mold assembly was
irradiated with ultraviolet light for about 22 seconds. The total
light energy applied during these 22 seconds was about 4500
millijoules per square centimeter ("mJ/cm.sup.2").
[0502] It has been found that applying activating light at this
point helped to cure some or all of the remaining liquid lens
forming composition. The second activating light step may be
repeated. In this example, the second activating light step was
repeated once. It is also possible to expose the front or both
sides of the lens to the second activating light.
[0503] After the second activating light was applied, the mold
assembly was allowed to cool. The reactions caused by exposure to
activating light may be exothermic. The activating lights also tend
to emit infra-red light which in turn heats the mold assembly. The
lens was then demolded. The demolded lens was substantially drier
and harder than lenses that were directly removed from mold
assemblies after the initial cure step.
Example 3
Oxygen Barrier Example #2
[0504] The protocol of Oxygen Barrier Example #1 was repeated
except that prior to removal of the gasket the lens mold assembly
was positioned so that the back face of the lens was exposed to
third activating light. In this case the third activating light was
at the same intensity and for the same time period as one pass of
the second activating light. It has been found that applying third
activating light at this point helped to cure some or all of the
remaining liquid lens forming composition so that when the gasket
was removed less liquid lens forming composition was present. All
of the remaining steps in Oxygen Barrier Example #1 were applied,
and the resultant lens was substantially dry when removed from the
molds.
Example 4
Conductive Heating Example
[0505] A liquid lens forming composition was initially cured in a
process and apparatus similar to that specified in Example 1 except
for post-cure treatment, which was conducted as follows:
[0506] After the sample was irradiated for 15 minutes, the lens was
placed in the post-cure unit to receive a dose of about 1500
mj/cm.sup.2 (+/-100 mJ) of activating light per pass. The gasket
was then removed from the mold assembly and the edges of the mold
were wiped with an absorbent tissue to remove incompletely cured
lens forming material proximate the mold edges. A strip of plastic
material impregnated with photoinitiator was wrapped around the
edges of the molds that were exposed when the gasket was removed.
Next, the mold assembly was passed through the post-cure unit once
to expose the front surface of the mold to a dose of about 1500
mJ/cm.sup.2. The mold assembly was then passed through the
post-cure unit four more times, with the back surface of the mold
receiving a dose of about 1500 mJ/cm.sup.2 per pass. The heat
source of the post-cure unit was operated such that the surface of
the hot plate reached a temperature of 340.degree. F.
(+/-50.degree. F.). A conformable "beanbag" container having a
covering made of NOMEX fabric was placed on the hot plate. The
container contained glass beads and was turned over such that the
portion of the container that had directly contacted the hot plate
(i.e., the hottest portion of the container) faced upward and away
from the hot plate. The mold assembly was then placed onto the
heated, exposed portion of the container that had been in direct
contact with the hot plate. The concave, non-casting face of the
mold was placed onto the exposed surface of the container, which
substantially conformed to the shape of the face. Heat was
conducted through the container and the mold member to the lens for
13 minutes. A lens having a Shore D hardness of 84 was formed.
Example 5
Curing Cycles
[0507] Some established cycles are detailed in the table below for
three semi-finished mold gasket sets: a 6.00D base curve, a 4.50D
base curve, and a 3.00D base curve. These cycles have been
performed with cooling air, at a temperature of about 56.degree.
F., directed at the front and back surfaces of a mold assembly.
Frosted diffusing window glass was positioned between the samples
and the lamps, with a layer of PO-4 acrylic material approximately
1 inch below the glass. A top light intensity was adjusted to 760
microwatts/cm.sup.2 and a bottom light intensity was adjusted to
950 microwatts/cm.sup.2, as measured at about the plane of the
sample. A Spectroline meter DM365N and standard detector stage were
used. An in-mold coating as described in U.S. Pat. No. 5,529,728 to
Buazza et. al. was used to coat both the front and back molds.
10 BASE CURVE Mold Sets 6.00 4.50 3.00 Front Mold 5.95 4.45 2.93
Back Mold 6.05 6.80 7.80 Gasket -5.00 13 mm 16 mm Resulting
Semifinished Blank Diameter 74 mm 76 mm 76 mm Center Thickness 9.0
mm 7.8 mm 7.3 mm Edge Thickness 9.0 mm 11.0 mm 15.0 mm Mass 46
grams 48 grams 57 grams Curing Cycle Variables Total Cycle Time
25:00 25:00 35:00 Initial Exposure 4:40 4:40 4:35 Number of Pulses
4 4 4 Timing (in seconds) and Duration of Pulses @ Elapsed Time
From Onset of Initial Exposure Pulse 1 15@10:00 15@10:00 15@13:00
Pulse 2 15@15:00 15@15:00 15@21:00 Pulse 3 30@19:00 30@19:00
20@27:00 Pulse 4 30@22:00 30@22:00 30@32:00
[0508] FIGS. 26, 27, and 28 each show temperature profiles of the
above-detailed cycles for a case where the activating light
exposure is continuous and a case where the activating light
delivery is pulsed. In FIGS. 26-28, "Io" denotes the initial
intensity of the activating light used in a curing cycle. The
phrase "Io=760/950" means that the light intensity was adjusted to
initial settings of 760 microwatts/cm.sup.2 for the top lamps and
950 microwatts/cm.sup.2 for the bottom lamps. The "interior
temperature" of FIGS. 26-28 refers to a temperature of the lens
forming material as measured by a thermocouple located within the
mold cavity.
Example 6
Pulse Method Using a Medium Pressure Vapor Lamp
[0509] An eyeglass lens was successfully cured with activating
light utilizing a medium pressure mercury vapor lamp as a source of
activating light (i.e., the UVEXS Model 912 previously described
herein). The curing chamber included a six inch medium pressure
vapor lamp operating at a power level of approximately 250 watts
per inch and a defocused dichroic reflector that is highly
activating light reflective. A high percentage of infrared
radiation was passed through the body of the reflector so that it
would not be directed toward the material to be cured. The curing
chamber further included a conveyer mechanism for transporting the
sample underneath the lamp. With this curing chamber, the transport
mechanism was set up so that a carriage would move the sample from
the front of the chamber to the rear such that the sample would
move completely through an irradiation zone under the lamp. The
sample would then be transported through the zone again to the
front of the chamber. In this manner the sample was provided with
two distinct exposures per cycle. One pass, as defined hereinafter,
consists of two of these distinct exposures. One pass provided a
dosage of approximately 275 millijoules measured at the plane of
the sample using an International Light IL 1400 radiometer equipped
with a XRL 340 B detector.
[0510] A lens cavity was created using the same molds, lens forming
composition, and gasket as described in Example 7 below. The
reaction cell containing the lens forming material was placed on a
supporting stage such that the plane of the edges of the convex
mold were at a distance of approximately 75 mm from the plane of
the lamp. The lens cavity was then exposed to a series of
activating light doses consisting of two passes directed to the
back surface of the mold followed immediately by one pass directed
to the front surface of the mold. Subsequent to these first
exposures, the reaction cell was allowed to cool for 5 minutes in
the absence of any activating radiation at an air temperature of
74.6 degrees F. and at an air flow rate of approximately 15 to 25
scf per minute to the back surface and 15 to 25 scf to the front
surface of the cell. The lens cavity was then dosed with one pass
to the front mold surface and returned to the cooling chamber for 6
minutes. Then the back surface was exposed in one pass and then was
cooled for 2 minutes. Next, the front surface was exposed in two
passes and then cooled for 3.5 minutes. The front surface and the
back surface were then each exposed to two passes, and the gasket
was removed to expose the edges of the lens. A strip of
polyethylene film impregnated with photoinitiator was then wrapped
around the edge of the lens and the front and back surfaces were
exposed to another 3 passes each. The back surface of the cell was
then placed on the conductive thermal in-mold postcure device using
a "bean-bag" container filled with glass beads on a hot plate at
about 340.degree. F. described previously (see Example 4) for a
time period of 13 minutes, after which the glass molds were removed
from the finished lens. The finished lens exhibited a distance
focusing power of -6.09 diopters, had excellent optics, was
aberration-free, was 74 mm in diameter, and had a center thickness
of 1.6 mm. During the cooling steps, a small surface probe
thermistor was positioned against the outside of the gasket wall to
monitor the reaction. The results are summarized below.
11 Approx. Elapsed Time Gasket After Activating Wall Temperature
Activating Light Dose Light Dose (min) (.degree. F.) 2 passes to
back surface 0 Not recorded and 1 pass to front surface 1 80.5 2
79.7 3 79.0 4 77.1 5 76.2 1 pass to front surface 0 Not recorded 1
83.4 2 86.5 3 84.6 4 Not recorded 5 81.4 6 79.5 1 pass to back
surface 0 Not recorded 1 79.3 2 79.0 2 passes to front surface 0
Not recorded 1 78.4 2 77.8 3 77.0 3.5 76.7
Example 7
Pulse Method Using a Single Xenon Flash Lamp
[0511] An eyeglass lens was successfully cured with activating
light utilizing a xenon flash lamp as a source of activating light.
The flash lamp used was an Ultra 1800 White Lightning photographic
strobe, commercially available from Paul C. Buff Incorporated of
Nashville, Tenn. This lamp was modified by replacing the standard
borosilicate flash tubes with quartz flash tubes. A quartz flash
tube is preferred because some of the activating light generated by
the arc inside the tube tends to be absorbed by borosilicate glass.
The strobe possessed two semicircular flash tubes that trigger
simultaneously and the flash tubes were positioned to form a ring
approximately 73 millimeters in diameter. The hole in the reflector
behind the lamps, which normally contains a modeling lamp for
photographic purposes, was covered with a flat piece of
highly-polished activating light reflective material that is
commercially available under the trade name of Alzac from Ultra
Violet Process Supply of Chicago, Ill. The power selector switch
was set to full power. The activating light energy generated from
one flash was measured using an International Light IL 1700
Research Radiometer available from International Light,
Incorporated of Newburyport, Mass. The detector head was an
International Light XRL 340 B, which is sensitive to radiation in
the 326 nm to 401 nm region. The window of the detector head was
positioned approximately 35 mm from the plane of the flash tubes
and was approximately centered within the ring formed by the
tubes.
[0512] A mold cavity was created by placing two round 80 mm
diameter crown glass molds into a silicone rubber ring or gasket
that possessed a raised lip around its inner circumference. The
edges of the glass molds rested upon the raised lip to form a
sealed cavity in the shape of the lens to be created. The inner
circumference of the raised lip corresponded to the edge of the
finished lens. The concave surface of the first mold corresponded
to the front surface of the finished lens and the convex surface of
the second mold corresponded to the back surface of the finished
lens. The height of the raised lip of the rubber ring into which
the two glass molds are inserted controls the spacing between the
two glass molds, thereby controlling the thickness of the finished
lens. By selecting proper gaskets and first and second molds that
possess various radii of curvature, lens cavities may be created to
produce lenses of various powers.
[0513] A lens cavity was created by placing a concave glass mold
with a radius of curvature of 407.20 mm and a convex glass mold
with a radius of curvature of 65.26 mm into a gasket which provided
spacing between the molds of 1.8 mm measured at the center of the
cavity. Approximately 32 grams of a lens forming monomer was
charged into the cavity. The lens forming material used for this
test was OMB-91 lens monomer. The reaction cell containing the lens
forming material was placed horizontally on a supporting stage such
that the plane of the edges of the convex mold were at a distance
of approximately 30 mm from the plane of the flash tubes and the
cell was approximately centered under the light source.
[0514] The back surface of the lens cavity was then exposed to a
first series of 5 flashes, with an interval of approximately 4
seconds in between each flash. The cell was then turned over and
the front surface was exposed to another 4 flashes with intervals
of about 4 seconds in between each flash. It is preferable to apply
the first set of flashes to the back surface to start to cure the
material so that any air bubbles in the liquid monomer will not
migrate from the edge of the cavity to the center of the optical
zone of the lens. Subsequent to these first nine flashes, the
reaction cell was allowed to cool for five minutes in the absence
of any activating radiation. To cool the reaction cell, air at a
temperature of 71.4 degrees F. and at a flow rate of approximately
15 to 25 scf per minute was applied to the back surface and air at
a temperature of 71.4 degrees F. and at a flow rate of
approximately 15 to 25 scf per minute was applied to the front
surface of the cell. The back surface of the lens cavity was then
dosed with one more flash and returned to the cooling chamber for
four minutes.
[0515] Next, the cell was exposed to one flash on the front surface
and cooled in the cooling chamber for seven minutes. Then the cell
was exposed to one flash on the front surface and one flash on the
back surface and cooled for three minutes. Next, the cell was
exposed to two flashes on the front surface and two flashes on the
back surface and cooled for four and a half minutes. The cell was
then exposed to five flashes each to the back surface and front
surface, and the gasket was removed to expose the edges of the
lens. A strip of polyethylene film impregnated with photoinitiator
(Irgacure 184) was then wrapped around the edge of the lens, and
the cell was exposed to another five flashes to the front surface
and fifteen flashes to the back surface. The back surface of the
cell was then placed on the conductive thermal in-mold postcure
device (i.e., "bean bags" filled with glass beads sitting on a hot
plate at approx. 340.degree. F.) as described previously (see
conductive heating example above) for a time period of 13 minutes,
after which the glass molds were removed from the finished lens.
The finished lens exhibited a distance focusing power of -6.16
diopters and a +2.55 bifocal add power, had excellent optics, was
aberration-free, was 74 mm in diameter, and had a center of
thickness of 1.7 mm. During the cooling steps, a small surface
probe thermistor was positioned against the outside of the gasket
wall to monitor the reaction. The results are summarized below.
12 Elapsed Time Gasket Dose From Dose (min) Wall Temperature (F.) 5
flashes to back surface 4 0 Not recorded flashes to front surface 1
Not recorded 2 78.4 3 77.9 4 76.9 5 75.9 1 flash to back surface 0
Not recorded 1 76.8 2 77.8 3 78 4 77.8 1 flash to front surface 0
Not recorded 1 79.4 2 81.2 3 81.1 4 79.7 5 78.7 6 77.5 7 77.4 1
flash to front surface and 1 0 Not recorded flash to back surface 1
78.8 2 78.8 3 78.0 2 flashes to front surface and 0 Not recorded 2
flashes to back surface 1 80.2 2 79.8 3 78.3 4 76.7 4.5 76.3
Example 8
Improved Curing Example
[0516] An 80 mm diameter glass progressive addition mold with a
nominal distance radius of curvature of -6.00 diopters and a +2.50
diopter bifocal add power was sprayed with a mixture of isopropyl
alcohol and distilled water in equal parts and wiped dry with a
lint free paper towel. The progressive mold was lenticularized to
provide an optical zone 68 mm in diameter along the 180 degree
meridian and 65 mm in diameter along the 90 degree meridian. The
non-casting face of the mold was mounted to a suction cup, which
was attached to a spindle. The spindle was placed on a spin coat
unit. A one inch diameter pool of liquid Primer was dispensed into
the center of the horizontally positioned glass mold from a soft
polyethylene squeeze bottle equipped with a nozzle with an orifice
diameter of approximately 0.040 inches. The composition of the
Primer is discussed in detail below (see Scratch Resistant Lens
Formation Process Example).
[0517] The spin motor was engaged to rotate the mold at a speed of
approximately 850 to 900 revolutions per minute, which caused the
liquid material to spread out over the face of the mold.
Immediately thereafter, a steady stream of an additional 1.5 to 2.0
grams of Primer material was dispensed onto the casting face of the
spinning mold with the nozzle tip positioned at a 45 degree angle
approximately 12 mm from the mold face such that the stream was
flowing with the direction of rotation of the mold. The stream of
Primer material was directed first at the center of the mold face
and then dispensed along the radius of the mold face in a direction
from the center toward the edge of the mold face. The solvent
present in the Primer was allowed to evaporate off for 8 to 10
seconds while the mold was rotated. The rotation was stopped and
the Primer coat present on the mold was cured via two exposures to
the activating light output from the medium pressure mercury vapor
lamp, totaling approximately 300 mJ/cm.sup.2.
[0518] The spin motor was again engaged and approximately 1.5 to
2.0 grams of HC8-H Hard Coat (see description below), commercially
available from the FastCast Corporation of Louisville, Ky. was
dispensed onto the spinning mold in a similar fashion as the Primer
coat. The solvent present in the HC8-H was allowed to evaporate off
for 25 seconds while the mold was rotated. The rotation was stopped
and the HC8-H coat was cured in the same manner as the Primer
coat.
[0519] The mold was removed from the FlashCure unit and assembled
into a silicone rubber gasket in combination with a cleaned convex
mold possessing a radius of curvature of +2.00 diopters. The raised
lip present on the inner circumference of the rubber gasket
provided a spacing of 6.3 mm between the two molds at the center
point. The mold/gasket assembly was positioned on a filling stage
and the edge of the gasket was peeled back to permit the cavity to
be filled with OMB-91 lens forming composition, commercially
available from the FastCast Corporation of Louisville, Ky. The edge
of the gasket was returned to its sealing relationship with the
edges of the molds and the excess lens forming composition was
vacuumed off the non-casting surface of the back mold with a
suction device. The filled mold/gasket assembly was placed on a
stage in a lens curing unit and subjected to four exposures of the
activating light output from the six inch medium pressure mercury
vapor lamp, totaling approximately 600 mJ/cm.sup.2.
[0520] Immediately following this initial dose of high intensity
activating light, the assembly was continuously exposed to streams
of air having a temperature of 42.degree. F. while being irradiated
with very low intensity activating light for eight minutes. The
light intensity measured approximately 90 microwatts/cm.sup.2 from
above plus approximately 95 microwatts/cm.sup.2 from below,
according to the plus lens light distribution pattern called for by
the manufacturer. The lamp racks are typically configured to
deliver activating light having an intensity of about 300
microwatt/cm.sup.2 for the standard fifteen minute curing cycle.
The reduction in activating light intensity was accomplished by
inserting a translucent high density polyethylene plate into the
light distribution filter plate slot along with the plus lens light
distribution plate. A translucent high density polyethylene plate
was positioned between the front mold member and one light
distribution plate and between the back mold member and the other
light distribution plate.
[0521] The non-casting surface of the back mold was subsequently
exposed to four doses of high intensity activating light totaling
approximately 1150 mJ/cm.sup.2. The gasket was stripped from the
assembly and residual uncured material wiped from the exposed edge
of the lens. An oxygen barrier strip (polyethylene) was wrapped
around the edge of the lens and the mold was exposed to two more
doses of high intensity activating light totaling 575 mJ/cm.sup.2
to the non-casting surface of the front mold followed by eight more
flashes to the non-casting surface of the back mold totaling 2300
mJ/cm.sup.2.
[0522] The non-casting surface of the back mold was placed in
contact with a thermal transfer pad, commercially available from
the FastCast Corporation of Louisville, Ky., at a temperature of
approximately 150 to 200.degree. F. for thirteen minutes. The
assembly was removed from the thermal transfer pad and the back
mold was removed with a slight impact from an appropriately sized
wedge. The front mold with the lens attached thereto was placed in
a container of room temperature water and the lens separated from
the front mold. The now-finished lens was sprayed with a mixture of
isopropyl alcohol and water in equal parts and wiped dry. The lens
read +3.98 D with an addition power of +2.50, was clear,
non-yellow, and exhibited good optics.
Example 9
Scratch Resistant Lens Formation Example
[0523] A first coating composition, hereinafter referred to as
"Primer", was prepared by mixing the following components by
weight:
[0524] 93.87% acetone;
[0525] 3.43% SR-399 (dipentaerythritol pentaacrylate), available
from Sartomer;
[0526] 2.14% CN-104 (epoxy acrylate), available from Sartomer;
[0527] 0.28% Irgacure 184 (1-hydroxycyclohexylphenylketone),
available from Ciba-Geigy; and
[0528] 0.28% Darocur 1173
(2-hydroxy-2-methyl-1-phenyl-propan-1-one) available from
Ciba-Geigy.
[0529] A second coating composition, hereinafter referred to as
"HC8-H" was prepared by mixing the following components by
weight:
[0530] 84.69% 1-methoxy 2-propanol;
[0531] 9.45% SR-399 (dipentaerythritol pentaacrylate), available
from Sartomer;
[0532] 4.32% SR601 (ethoxylated bisphenol A diacrylate), available
from Sartomer; and
[0533] 1.54% Irgacure 184 (1-hydroxycyclohexyl phenyl ketone),
available from Ciba-Geigy.
[0534] Each of these coating compositions was prepared by first
dissolving the monomers into the solvent, then adding the
photoinitiators, mixing well, and finally passing the composition
through a one micron filter prior to use.
[0535] An 80 mm diameter glass, 28 mm flattop mold with a distance
radius of curvature of -6.00 diopters and a +2.00 diopter bifocal
add power were sprayed with a mixture of isopropyl alcohol and
distilled water in equal parts. The flattop mold was wiped dry with
a lint free paper towel. The non-casting face of the mold was
mounted to a suction cup, which was attached to a spindle. The
spindle was placed on the spin coating unit.
[0536] A one inch diameter pool of liquid Primer was dispensed into
the center of the horizontally positioned glass mold. The Primer
was dispensed from a soft polyethylene squeeze bottle equipped with
a nozzle having an orifice diameter of approximately 0.040 inches.
A spin motor of the spinning device was engaged to rotate the mold
at a speed of approximately 850 to 900 revolutions per minute,
causing the liquid Primer to spread out over the face of the mold.
immediately thereafter, a steady stream of an additional 1.5 to 2.0
grams of Primer material was dispensed onto the casting face of the
spinning mold. The stream of Primer material was directed onto the
casting face with the nozzle tip positioned at a 45 degree angle
approximately 12 mm from the mold face. This positioning of the
nozzle tip made the stream to flow with the direction of rotation
of the mold. The stream of Primer material was directed first at
the center of the mold face and then dispensed along the radius of
the mold face in a direction from the center toward the edge of the
mold face.
[0537] The solvent present in the Primer was allowed to evaporate
off for 8 to 10 seconds during rotation of the mold. The rotation
was stopped and the Primer coat which remained on the mold was
cured via two exposures to the activating output from a medium
pressure mercury vapor lamp, totaling approximately 300
mJ/cm.sup.2. All light intensity/dosage measurements cited herein
were taken with an International Light IL-1400 Radiometer equipped
with an XLR-340B Detector Head, both commercially available from
International Light, Inc. of Newburyport, Mass.
[0538] Upon exposure to the activating light, the spin motor was
again engaged and approximately 1.5 to 2.0 grams of HC8-H Hard
Coat, commercially available from the FastCast Corporation of
Louisville, Ky. was dispensed onto the spinning mold in a similar
fashion as the Primer coat. The solvent present in the HC8-H was
allowed to evaporate off for 25 seconds while the mold was
spinning. The rotation was stopped, and the HC8-H coat was cured in
the same manner as the Primer coat.
[0539] The mold was removed from the spin coating unit and
assembled into a silicone rubber gasket in combination with a
cleaned convex mold possessing a radius of curvature of +7.50
diopters. The raised lip present on the inner circumference of the
rubber gasket provided a spacing of 1.8 mm between the two molds at
the center point. At this point, the mold/gasket assembly was
positioned on a filling stage and the edge of the gasket was peeled
back to permit the cavity to be filled with OMB-91 lens forming
composition, commercially available from the FastCast Corporation
of Louisville, Ky. The edge of the gasket was returned to its
sealing relationship with the edges of the molds and the excess
lens forming composition was vacuumed off the non-casting surface
of the back mold with a suction device.
[0540] The filled mold/gasket assembly was transferred from the
filling stage to a lens curing unit. While in the lens curing unit,
the assembly was continuously irradiated with activating light from
both sides for a period of 15 minutes at approximately 300
microwatts/cm.sup.2 from above and at approximately 350
microwatts/cm.sup.2 from below, according to the minus lens light
distribution pattern called for by the manufacturer. During the
irradiation, the casting cell was continuously exposed to streams
of air having a temperature of 42.degree. F.
[0541] The non-casting surface of the back mold was exposed to four
doses of high intensity activating light totaling approximately
1150 mJ/cm.sup.2. The gasket was stripped from the assembly and
residual uncured material was wiped from the exposed edge of the
lens. An oxygen barrier strip (polyethylene) was wrapped around the
edge of the lens. The mold/gasket assembly was exposed to two more
doses of high intensity activating light, wherein 575 mJ/cm.sup.2
total was directed to the non-casting surface of the front mold.
Subsequently, eight more flashes of the activating light were
directed to the non-casting surface of the back mold, totaling 2300
mJ/cm.sup.2.
[0542] The non-casting surface of the back mold was placed in
contact with a thermal transfer pad, commercially available from
the FastCast Corporation of Louisville, Ky., at a temperature of
approximately 150 to 200.degree. F. for thirteen minutes. The
mold/gasket assembly was removed from the thermal transfer pad, and
the back mold was removed with a slight impact from an
appropriately sized wedge. The front mold with the lens attached
thereto was placed in a container of room temperature water. While
within the water, the lens became separated from the front mold.
The now-finished lens was sprayed with a mixture of isopropyl
alcohol and water in equal parts and wiped dry.
[0543] The lens was positioned in a holder and placed into a heated
dye pot for 5 minutes. The dye pot contained a solution of BPI
Black, commercially available from Brain Power, Inc. of Miami,
Fla., and distilled water at a temperature of approximately 190
degrees F. The lens was removed from the dye pot, rinsed with tap
water, and wiped dry. The lens exhibited a total visible light
absorbance of approximately 80%. When inspected for cosmetic
defects on a light table, no pinhole defects were observed.
Further, the tint which had been absorbed by the back surface of
the lens was found to be smooth and even.
Example 10
Formation of a Plastic Lens Containing Photochromic Material
[0544] A polymerizable mixture of PRO-629 (see above for a
description of the components of PRO-629), photochromic pigments,
and a photoinitiator/co-initiator system was prepared according to
the following procedure. A photochromic stock solution was prepared
by dissolving the following pigments into 484 grams of HDDMA.
13 Pigment grams % by wt. Dye #94 1.25 0.250% Dye #266 0.45 0.090%
Variacrol Red PNO 2.66 0.532% Variacrol Yellow L 1.64 0.328%
Reversacol Corn Yellow 3.58 0.716% Reversacol Berry Red 2.96 0.590%
Reversacol Sea Green 2.17 0.434% Reversacol Palatinate Purple 1.29
0.258% Total 16.0 3.200%
[0545] Dye #94 and Dye #266 are indilino-spiropyrans commercially
available from Chroma Chemicals, Inc. in Dayton, Ohio. Variacrol
Red PNO is a spiro-napthoxazine material and Variacrol Yellow L is
a napthopyran material, both commercially available from Great
Lakes Chemical in West Lafayette, Ind. Reversacol Corn Yellow and
Reversacol Berry Red are napthopyrans and Reversacol Sea Green, and
Reversacol Palatinate Purple are spiro-napthoxazine materials
commercially available from Keystone Analine Corporation in
Chicago, Ill.
[0546] The powdered pigments were weighed and placed in a beaker.
The HDDMA was added to the powdered pigments, and the entire
mixture was heated to a temperature in the range from about
50.degree. C. to 60.degree. C. and stirred for two hours.
Subsequently, the photochromic stock solution was cooled to room
temperature and then gravity fed through a four inch deep bed of
aluminum oxide basic in a one inch diameter column. Prior to
passing the stock solution through the alumina, the alumina was
washed with acetone and dried with air. The remaining HDDMA was
forced out of the alumina with pressurized air. It is believed that
this filtration step removes any degradation by-products of the
photochromic pigments and/or any impurities present in the mixture.
After the filtration step, the stock solution was passed through a
1 micron filter to remove any alumina particles which may have
passed out of the column with the stock solution.
[0547] A photoinitiator stock solution containing a photoinitiator
combined with an ultraviolet/visible light absorber was also
prepared by mixing 2.56 grams of CGI-819 and 0.2 grams of Tinuvin
400, an ultraviolet/visible light absorber commercially available
from Ciba Additives of Tarrytown, N.Y., with 97.24 grams of
PRO-629. The stock solution was stirred for two hours at room
temperature in the absence of light. The photoinitiator stock
solution was then filtered by passing it through a layer of alumina
and a one micron filter. The stock solution was placed in an opaque
polyethylene container for storage.
[0548] A background dye stock solution was prepared by mixing 50
grams of a 422 ppm solution of A241/HDDMA, 50 grams of a 592 ppm
solution of Thermoplast Red 454/HDDMA, 50 grams of 490 ppm solution
of Zapon Brown 286/HDDMA, 50 grams of 450 ppm solution of Zapon
Brown 287/HDDMA, 50 grams of 1110 ppm solution of Oil Soluble Blue
II/HDDMA, and 50 grams of a 1110 ppm solution of Thermoplast Blue
II/HDDMA, all with 700 grams of PRO-629. The entire mixture was
heated to a temperature ranging from about 50.degree. C. to
60.degree. C. and subsequently stirred for two hours.
[0549] A lens forming composition was prepared by adding 12.48
grams of the above described photochromic stock solution, 10 grams
of the photoinitiator stock solution, 27 grams of the background
dye stock solution, and 7.3 grams of the NMDEA co-initiator to
943.22 grams of PRO-629. The components of the lens forming
composition were stirred at room temperature for several minutes
until well mixed. This composition is hereafter referred to as PC
#1. The PC#1 contained the following amounts of components.
14 Component Amount Tripropyleneglycol diacrylate 31.16%
Tetraethyleneglycol diacrylate 20.45% Trimethylolpropane
triacrylate 19.47% Bisphenol A bis allyl carbonate 16.55%
Hexanediol dimethacrylate 11.56% Dye #94 31.20 ppm Dye #266 11.20
ppm Variacrol Red PNO 66.40 ppm Variacrol Yellow L 40.90 ppm
Reversacol Corn Yellow 89.30 ppm Reversacol Berry Red 73.60 ppm
Reversacol Sea Green 54.20 ppm Reversacol Palatinate Purple 32.20
ppm A241 0.57 ppm Thermoplast Red 454 0.80 ppm Zapon Brown 286 0.66
ppm Zapon Brown 287 0.61 ppm Oil Soluble Blue II 1.50 ppm
Thermoplast Blue 1.50 ppm CGI-819 255.90 ppm NMDEA 0.73% Tinuvin
400 20.00 ppm
[0550] An 80 mm diameter concave glass progressive addition mold
having a distance radius of curvature of 6.00 diopters and a +1.75
diopter bifocal add power was sprayed with a mixture of isopropyl
alcohol and distilled water in equal parts and wiped dry with a
lint free paper towel. The mold was then mounted with its casting
face upward on the center of a stage. The mold was fixed securely
to the stage using three equidistant clip-style contact points to
hold the periphery of the mold. The mold stage had a spindle
attached to it which was adapted to connect to a spin coating
device. The mold stage, with the mold affixed, was placed within
the spin coating device. The mold was rotated at approximately 750
to 900 revolutions per minute. A stream of isopropyl alcohol was
directed at the casting surface while the casting surface was
simultaneously brushed with a soft camel hair brush to clean the
surface. After the cleaning step, the mold surface was dried by
directing a stream of reagent grade acetone over the surface and
allowing it to evaporate off, all while continuing the rotation of
the mold.
[0551] The rotation of the mold was then terminated and a one inch
diameter pool of a liquid coating composition was dispensed into
the center of the horizontally positioned glass mold from a soft
polyethylene squeeze bottle equipped with a nozzle having an
orifice diameter of approximately 0.040 inches. The spin motor was
engaged to rotate the mold at a speed of approximately 750 to 900
revolutions per minute, causing the liquid material to spread out
over the face of the mold. Immediately thereafter, a steady stream
of an additional 1.5 to 2.0 grams of the coating composition was
dispensed onto the casting face of the spinning mold. The stream
was moved from the center to the edge of the casting face with a
nozzle tip positioned at a 45.degree. angle approximately 12 mm
from the mold face. Thus, the stream was flowing with the direction
of rotation of the mold.
[0552] The solvent present in the coating composition was allowed
to evaporate while rotating the mold for 10 to 15 seconds. The
rotation was stopped, and then the coating composition on the mold
was cured via a total exposure of approximately 300 mJ/cm.sup.2 of
activating light. The light was provided from a medium pressure
mercury vapor lamp. All light intensity/dosage measurements cited
herein were taken with an International Light IL-1400 Radiometer
equipped with an XLR-340B Detector Head, both commercially
available from International Light, Inc. of Newburyport, Mass. At
this point, the spin motor was again engaged and approximately 1.5
to 2.0 grams of additional coating composition was dispensed onto
the spinning mold. The solvent of the composition was allowed to
evaporate, and the composition was cured in a similar fashion to
the first layer of coating composition.
[0553] The above described coating composition comprised the
following materials:
15 Material % by wt. Irgacure 184 0.91% Tinuvin 770 0.80% CN-104
2.00% SR-601 1.00% SR-399 8.60% Acetone 26.00% Ethanol 7.00%
1-Methoxypropanol 53.69%
[0554] Irgacure 184 is a photoinitiator commercially available from
Ciba Additives, Inc. CN-104 is an epoxy acrylate oligomer, SR-601
is an ethoxylated bisphenol A diacrylate, and SR-399 is
dipentaerythritol pentaacrylate, all available from Sartomer
Company in Exton, Pa. The acetone, the ethanol, and the
1-methoxypropanol were all reagent grade solvents. The Tinuvin 770
improves the impact resistance of the lens and is available from
Ciba Additives, Inc.
[0555] An 80 mm diameter convex mold with radii of curvature of
6.80/7.80 diopters was cleaned and coated using the same procedure
described above except that no pooling of the coating composition
occurred in the center of the mold when the composition was
dispensed thereto.
[0556] The concave and convex molds were then assembled together
with a silicone rubber gasket. A raised lip on the inner
circumference of the rubber gasket provided a spacing of 2.8 mm
between the two molds at the center point. At this point the
mold/gasket assembly was positioned on a filling stage. The edge of
the gasket was peeled back to permit the cavity to be filled with
PC #1 lens forming composition. The edge of the gasket was returned
to its sealing relationship with the edges of the molds, and the
excess lens forming composition was vacuumed from the non-casting
surface of the back mold with a suction device. The filled
mold/gasket assembly was then transferred from the filling stage to
a lens curing unit. The assembly was placed with the back mold
facing upward on a black stage configured to hold the mold/gasket
assembly.
[0557] An activating light filter was then placed on top of the
back mold. The filter was approximately 80 mm in diameter which is
the same as the mold diameter. The filter also had a spherical
configuration with a center thickness of 6.7 mm and an edge
thickness of 5.5 mm. The filter was taken from a group of
previously made filters. These filters were formed by using
eyeglass lens casting molds and gaskets to create cavities that
were thickest in the center (a plus spherical cavity) and cavities
that were thinnest in the center (a minus spherical cavity). A
toric component was also incorporated with some of these cavities
to form compound cavities.
[0558] The filter cavities were filled with an activating light
curable composition comprising by weight: 99.37% PRO-629, 0.35%
K-Resin, 0.27% NMDEA, 121 ppm CGI-819, and 10 ppm Tinuvin 400.
K-resin is a styrene-butadiene copolymer commercially available
from Phillips Chemical Company. To form this composition, the
K-resin was first dissolved in toluene. An appropriate amount of
the K-resin toluene solution was added to the PRO-629, and then the
toluene was evaporated off by heat and stirring. The NMDEA, CGI-19,
and the Tinuvin 400 were then added to the PRO-629/K-Resin
solution. The compositions contained in the cavities were cured by
exposure to activating light. When the cured article was removed
from the mold cavity, it exhibited a high degree of haze caused by
the incompatibility of the PRO-629 and the K-Resin. In the
strictest sense of the word, it should be noted that these filters
were not "lenses" because their function was not to focus light but
rather to scatter and diffuse light.
[0559] The mold/gasket assembly and the filter were then irradiated
with four consecutive doses of activating light totaling
approximately 1150 mJ/cm.sup.2, as previously measured at the plane
of the mold cavity with no filter or any other intervening media
between the light source and the plane. The mold/gasket assembly
was then turned over on the stage so that the front mold was facing
upward. The mold/gasket assembly was further rotated 90 degrees
around the paraxial axis from its original position. The light
filter was then placed over the front mold. The entire assembly was
then exposed to two more doses of activating light totaling
approximately 575 mJ/cm.sup.2. The mold/gasket assembly was removed
from the curing chamber. The gasket was removed from the molds, and
the exposed edge of the lens was wiped to remove any residual
liquid. The molds with lens were then placed in a vertical
orientation in a rack, and the non-casting faces of both the front
and back molds were exposed to ambient room temperature air for a
period of approximately ten minutes. Then, without the
aforementioned light filter in place, the mold assembly was dosed
with four exposures totaling 600 mJ/cm.sup.2 directed toward the
back mold and two exposures totaling 300 mJ/cm.sup.2 directed
toward the front mold.
[0560] Subsequent to these exposures, the junction of the back mold
and the lens was scored with the edge of a brass spatula. The back
mold was then removed from the lens by positioning an appropriate
sized Delrin wedge between the front and back molds and applying a
sharp impact to the wedge. The lens, along with the front mold to
which it was attached, was held under running tap water and
simultaneously brushed with a soft brush to remove any flakes or
particles of polymer from the edges and surface of the lens. The
front mold was then separated from the lens by breaking the seal
between the two with the point of a pin pressed against the
junction of the front mold and the lens. The lens was then placed
concave side upward on a lens stage of similar design to the mold
stage, except that the peripheral clips were configured to secure a
smaller diameter workpiece. The lens stage, with the lens affixed,
was positioned on the spin coating unit and rotated at about 750 to
900 revolutions per minute. A stream of isopropyl alcohol was
directed at the concave surface while simultaneously brushing the
surface with a soft, clean brush.
[0561] After brushing, a stream of isopropyl alcohol was directed
at the surface of the lens, and the rotation was continued for a
period of approximately 30 seconds until the lens was dry. The lens
was turned over on the stage so that the convex surface of the lens
faced upward. Then the cleaning procedure was repeated on the
convex surface. With the convex surface facing upward, the lens was
dosed with four exposures of activating light totaling
approximately 1150 mJ/cm.sup.2. The lens was again turned over on
the stage such that the concave surface was upward. The lens was
subjected to an additional two exposures totaling 300 mJ/cm.sup.2.
The lens was removed from the stage and placed in a convection oven
at 115.degree. C. for five minutes. After annealing the lens, it
was removed from the oven and allowed to cool to room temperature.
At this point the lens was ready for shaping by conventional means
to fit into an eyeglass frame.
[0562] The resulting lens was approximately 72 mm in diameter. The
lens had a center thickness of 2.6 mm, a distance focusing power of
-0.71-1.00 diopters, and a bifocal addition strength of 1.74
diopters. The lens appeared to have a bleached color of tan. Also,
the lens that was formed exhibited approximately 75% visible
transmittance as measured with a Hoya ULT-3000 meter. The lens was
exposed to midday sunlight at a temperature of approximately
75.degree. F. for 3 minutes. After being exposed to sunlight, the
lens exhibited a gray color and a visible light transmittance of
approximately 15%. The optics of the lens appeared to be crisp,
without aberrations in either the distance or the bifocal segment
regions. The same lens forming composition was cured to form a
plano lens so that the lens could be scanned with a Hewlett Packard
Model 8453 UV-Vis spectrophotometer. See FIG. 30 for a plot of %
transmittance versus wavelength (nm), as exhibited by the piano
lens in its lightened state (i.e., without sunlight exposure). The
lens exhibited very little transmittance of light at wavelengths
below about 370 nm.
[0563] The eyeglass lens of this example was formed from a lens
forming composition included ultraviolet/visible light absorbing
photochromic compounds by using activating light. Since
photochromic pigments tend to absorb ultraviolet/visible light
strongly, the activating light might not have penetrated to the
depths of the lens forming composition. The lens forming
composition, however, contained a co-initiator in conjunction with
a photoinitiator to help promote the curing of the entire lens
forming composition. The present example thus demonstrates that a
photochromic lens containing both a photoinitiator and a
co-initiator may be cured using activating light to initiate
polymerization of the lens forming composition.
Example 11
Casting a Colorless Lens Containing Ultraviolet/Visible Light
Absorbers
[0564] According to a preferred embodiment, a polymerizable mixture
of PRO-629 (see above for a description of the components of
PRO-629), colorless ultraviolet/visible light absorbing compounds,
an ultraviolet stabilizer, background dyes, and a
photoinitiator/co-initiator package was prepared according to the
following procedure. Six separate stock solutions were prepared.
One stock solution contained the photoinitiator, two stock
solutions contained ultraviolet/visible light absorbing compounds,
one stock solution contained co-initiators, one stock solution
contained an ultraviolet light stabilizer, and one stock solution
contained a background dye package. Each of these stock solutions
were treated by passing them through a one inch diameter column
packed with approximately 30 grams of alumina basic. It is believed
that this step reduced the impurities and trapped the acidic
byproducts present in each of the additives to the PRO-629. The
following is a detailed description of the preparation of the
polymerizable mixture mentioned above.
[0565] About 500 grams of a photoinitiator stock solution was
prepared by dissolving 2.5% by weight of bis(2,6-dimethoxybenzoyl)
(2,4,4-trimethyl-phenyl) phosphine oxide (CGI-819 commercially
available from Ciba Additives) in Pro-629. This mixture was passed
through an alumina basic column in the dark.
[0566] About 500 grams of the ultraviolet light absorber stock
solution was prepared by dissolving 2.5% by weight of
2(2H-benzotriazol-2-yl)-4-(1- ,1,3,3-tetramethyl)phenol (98%
purity) in PRO-629. This mixture was also passed through an alumina
basic column.
[0567] About 500 grams of a co-initiator stock solution was
prepared by mixing 70% by weight of CN-384 (a reactive amine
co-initiator commercially available from Sartomer Company) in
Pro-629. This mixture was passed through an alumina basic
column.
[0568] About 271 grams of an ultraviolet light stabilizer stock
solution was prepared by mixing 5.55% by weight of Tinuvin 292 in
PRO-629. This mixture was passed through an alumina basic
column.
[0569] About 250 grams of an ultraviolet/visible light absorber
stock solution was prepared by mixing 5.0% Tinuvin 400 (a mixture
of
2-[4-((2-hydroxy-3-dodecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-di-
methylphenyl)-1,3,5-triazine and
2-[4-((2-hydroxy-3-tridecyloxypropyl)-oxy-
)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine) by
weight in PRO-629. This mixture was passed through an alumina basic
column.
[0570] About 1000 grams of a background dye stock solution was
prepared by mixing about 50 grams of a 592 ppm solution of
Thermoplast Red 454/HDDMA, 50 grams of 490 ppm solution of Zapon
Brown 286/HDDMA, 50 grams of 450 ppm solution of Zapon Brown
287/HDDMA, 50 grams of 1110 ppm solution of Oil Soluble Blue
II/HDDMA, and 50 grams of a 1110 ppm solution of Thermoplast Blue
P/HDDMA, all with 750 grams of PRO-629. The entire mixture was
heated to a temperature between about 50.degree. and 60.degree. C.
and stirred for two hours. This mixture was passed through an
alumina basic column.
[0571] About 250 grams of CN-386 (a reactive amine co-initiator
commercially available from Sartomer Company) was passed through an
alumina basic column.
[0572] A lens forming composition was prepared by mixing 967.75
grams of PRO-629 with 12.84 grams of the 2.5%
2(2H-benzotriazol-2-yl)-4-(1,1,3,3-t- etramethyl)phenol
ultraviolet/visible light absorber stock solution, 4.3 grams of the
70% CN-384 co-initiator stock solution, 8.16 grams of the 2.5%
CGI-819 photoinitiator stock solution, 0.53 grams of the CN-386,
1.54 grams of the Tinuvin 400 ultraviolet/visible light absorber
stock solution, 0.92 grams of the Tinuvin 292 ultraviolet light
stabilizer stock solution, and 4.0 grams of the background dye
stock solution. The resulting lens forming composition contained
the following components:
16 Material % by weight PRO-629 99.10%
2(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethyl)phenol 321 ppm
Tinuvin 400 77 ppm Tinuvin 292 51 ppm CN-384 0.3% CN-386 0.53%
CGI-819 204 ppm Thermoplast Red 0.12 ppm Zapon Brown 286 0.10 ppm
Zapon Brown 287 0.10 ppm Oil Soluble Blue II 0.22 ppm Thermoplast
Blue 0.22 ppm
[0573] An 80 mm diameter flattop concave glass mold with a distance
radius of curvature of 2.85 diopters and a +3.00 diopter bifocal
add power was cleaned and coated as described in Example 10.
[0574] An 80 mm diameter convex mold with radii of curvature of
7.05 diopters was cleaned and coated in the same fashion described
above except that no pooling of the coating composition occurred in
the center of the mold when the composition was dispensed
thereto.
[0575] Both the concave and convex molds were then provided with a
cured adhesion-promoting coating composition. By providing such a
coating, the adhesion between the casting surface of the glass mold
and the lens forming composition was increased, thereby reducing
the possibility of premature release of the lens from the mold. The
coating further provided abrasion resistance, chemical resistance,
and improved cosmetics to the finished lens.
[0576] The concave and convex molds were then assembled and placed
within a lens curing unit as described in Example 10.
[0577] An activating light filter was then placed on top of the
back mold. The filter was approximately 80 mm in diameter which is
the same as the mold diameter. It had a piano configuration with a
thickness of 3.1 mm. This filter transmitted approximately 30% of
the incident activating light from the source as measured using the
IL 1400 radiometer with a XRL-340B detector head. The filter was
taken from a group of previously made filters. The fabrication of
these filters was discussed in Example 10.
[0578] The mold/gasket assembly in which the lens forming
composition had been placed and which had been covered by the above
described filter was then irradiated with four consecutive doses of
activating light totaling approximately 600 mJ/cm.sup.2, as
measured using the 1L-1400 Radiometer equipped with the XLR-340B
detector. This measurement was taken at the plane of the mold
cavity while no filter or any intervening media was present between
the light source and the plane. The mold/gasket assembly was then
turned over on the stage so that the front mold was facing upward.
The mold/gasket assembly was further rotated 90 degrees around the
paraxial axis from its original position. The light filter was then
replaced over the front mold. The entire assembly was exposed to
two more doses of activating light totaling approximately 300
mJ/cm.sup.2.
[0579] The mold/gasket assembly was then removed from the curing
chamber, and the gasket was removed from the assembly. The mold was
then returned to the lens curing chamber such that the back mold
was facing upward. An opaque rubber disc, approximately 80 mm in
diameter was placed over the back mold. This disc had the function
of preventing activating light from impinging on the major portion
of the material contained within the cavity. With the disc in
position, the cell was exposed to two more exposures at 300
mJ/cm.sup.2. This subsequent exposure was used to cure the residual
liquid around the edges of the lens, particularly around the
junction between the front mold and the lens and to help seal the
periphery. The mold assembly was removed from the curing chamber
and placed in a vertical orientation in a rack. The non-casting
faces of both the front and back molds were then exposed to ambient
room temperature air for a period of approximately fifteen minutes.
At this point, the entire mold assembly was dosed with two
exposures totaling 300 mJ/cm.sup.2 directed toward the back mold
and two exposures totaling 300 mJ/cm.sup.2 directed toward the
front mold, without the aforementioned light filter or opaque disc
in place.
[0580] The lens was removed from the mold assembly and post-cured
as described in Example 10.
[0581] The resulting lens was approximately 72 mm in diameter, had
a center thickness of 1.5 mm, a distance focusing power of 4.08
diopters, and a bifocal addition strength of 3.00 diopters. The
resultant lens was water white. The optics of the lens were crisp,
without aberrations in either the distance or the bifocal segment
regions. The same lens forming composition was cured to form a
plano lens. The piano lens was scanned with a Hewlett Packard Model
8453 UV-Vis spectrophotometer. See FIG. 31 for a plot of %
transmittance versus wavelength (nm), as exhibited by the
photochromic lens when exposed to sunlight. The lens exhibited
virtually no transmittance of light at wavelengths below about 370
nm. Also shown in FIG. 31 are the results of a similar scan made on
a piano lens formed using the OMB-91 lens forming composition (see
Curing by the Application of Pulsed Activating Light above for
components of OMB-91). The OMB-91 lens, which has no
ultraviolet/visible light absorbing compounds, appears to transmit
light at wavelengths shorter than 370 nm, unlike the colorless lens
that contained ultraviolet/visible light absorbing compounds.
[0582] The eyeglass lens of this example was cured using activating
light even though the lens forming composition included activating
light absorbing compounds. Since activating light absorbing
compounds tend to absorb activating light strongly, the activating
light might not have penetrated to the depths of the lens forming
composition. The lens forming composition, however, contained a
co-initiator in conjunction with a photoinitiator to help promote
the curing of the entire lens forming composition. The present
example thus demonstrates that a lens containing
ultraviolet/visible light absorbing compounds may be cured using
activating light to initiate polymerization of a lens forming
composition which contains a photoinitiator/co-initiator system.
The lens was also produced using activating light of comparable
intensity and duration as was used for the production of
photochromic lenses. Thus, the addition of ultraviolet/visible
light absorbers to a non-photochromic lens forming composition,
allows both photochromic and non-photochromic lens forming
compositions to be cured using the same apparatus and similar
procedures.
Example 12
Casting a Colored Lens Containing Ultraviolet/Visible Light
Absorbers
[0583] According to a preferred embodiment, a polymerizable mixture
of PRO-629 (see above for a description of the components of
PRO-629), fixed pigments, and a photoinitiator/co-initiator package
was prepared according to the following procedure. Nine separate
stock solutions were prepared. Seven of the stock solutions
contained fixed pigments, one of the stock solutions contained an
ultraviolet/visible light absorbing compound, and one of the stock
solutions contained a photoinitiator. Each of these stock solutions
were treated by passing them through a one inch diameter column
packed with approximately 30 grams of alumina basic. It is believed
that this step reduces the impurities and traps the acidic
byproducts present in each of the additives to the PRO-629.
[0584] For each of the following fixed pigments, a stock solution
was prepared by the following procedure. The pigments used were
Thermoplast Red 454, Thermoplast Blue P, Oil Soluble Blue II, Zapon
Green 936, Zapon Brown 286, Zapon Brown 287, and Thermoplast Yellow
284. One gram of each pigment was dissolved in 499 grams of HDDMA.
Each mixture was heated to a temperature in the range of from about
50.degree. C. to about 60.degree. C. for approximately two hours.
This mixture was passed through an alumina basic column. The
alumina was then washed with 200 grams of HDDMA at a temperature of
about 50.degree. C. to about 60.degree. C. followed by 300 grams of
PRO-629 at a temperature of about 50.degree. C. to about 60.degree.
C. This washing step ensured that any pigments trapped in the
alumina were washed into the stock solution. This resulted in stock
solutions which contained a 0.1% concentration of each pigment in
29.97% PRO-629 and 69.93% HDDMA.
[0585] About 250 grams of the ultraviolet/visible light absorber
stock solution was prepared by dissolving 5.0% Tinuvin 400 by
weight in PRO-629. This mixture was passed through an alumina basic
column.
[0586] About 500 grams of the photoinitiator stock solution was
prepared by dissolving 2.5% by weight of bis(2,6-dimethoxybenzoyl)
(2,4,4-trimethylphenyl) phosphine oxide (CGI-819 commercially
available from Ciba Additives) in PRO-629. This mixture was passed
through an alumina basic column in the dark.
[0587] A lens forming composition was prepared by mixing 685.3
grams of PRO-629 with 10.48 grams of the 2.5% CGI-819
photoinitiator stock solution, 5.3 grams of NMDEA
(N-methyldiethanolamine is commercially available from Aldrich
Chemicals), 0.6 grams of Tinuvin 400 ultraviolet/visible light
absorber stock solution, 7 grams of the Thermoplast Red stock
solution, 58.3 grams of the Thermoplast Blue stock solution, 55.5
of the Oil Soluble Blue II stock solution, 29.2 grams of the Zapon
Green 936 stock solution, 68.1 grams of the Zapon Brown 286 stock
solution, 38.9 grams of the Zapon Brown 287 stock solution, and
41.3 grams of the Thermoplast Yellow 104 stock solution. The
resulting lens forming composition contained the following
components:
17 Material % by weight Bisphenol A bis allyl carbonate 13.35%
Tripropyleneglycol diacrylate 25.13% Tetraethyleneglycol diacrylate
16.49% Trimethylolpropane triacrylate 15.71% Hexanediol
dimethacrylate 28.75% Thermoplast Red 7.0 ppm Zapon Brown 286 68.1
ppm Zapon Brown 287 38.9 ppm Oil Soluble Blue II 55.5 ppm
Thermoplast Blue 58.3 ppm Zapon Green 936 29.2 ppm Thermoplast
Yellow 104 41.3 ppm NMDEA 0.53% CGI-819 262 ppm Tinuvin 400 30
ppm
[0588] An 80 mm diameter flattop concave glass mold with a distance
radius of curvature of 6.0 diopters was cleaned and coated as
described in Example 10.
[0589] An 80 mm diameter convex mold with radii of curvature of
6.05 diopters was cleaned and coated in the same fashion except
that no pooling of the coating composition occurred in the center
of the mold when the composition was dispensed thereto.
[0590] The concave and convex molds were then coated with a cured
adhesion-promoting coating composition. By providing such a
coating, the adhesion between the casting surface of the glass mold
and the curing lens forming composition was increased, thereby
reducing the possibility of premature release of the lens from the
mold. The coating also provided abrasion resistance, chemical
resistance, and improved cosmetics to the finished lens.
[0591] The concave and convex molds were then assembled and placed
within a lens curing unit as described in Example 10.
[0592] An activating light filter was then placed on top of the
back mold. The filter was approximately 80 mm in diameter, which is
the same as the mold diameter. It had a plano configuration with a
thickness of 3.1 mm. This filter transmitted approximately 30% of
the incident activating light from the source as measured using the
IL-1400 radiometer with a XRL-340B detector head. The filter was
taken from a group of previously made filters. The fabrication of
these filters was discussed in Example 10.
[0593] The mold/gasket assembly containing the lens forming
composition was then irradiated with six consecutive doses of
activating light totaling approximately 1725 mJ/cm.sup.2, as
previously measured using the IL-1400 Radiometer equipped with the
XLR-340B detector, at the plane of the mold cavity with no filter
or any intervening media between the light source and the plane.
The mold/gasket assembly was then turned over on the stage so that
the front mold was facing upward. The entire assembly was then
exposed to six more doses of activating light totaling
approximately 1725 mJ/cm.sup.2. The mold/gasket assembly was
removed from the curing chamber. The gasket was removed from the
molds, and the assembly was placed in a vertical orientation in a
rack such that the non-casting faces of both the front and back
molds were exposed to ambient room temperature air for a period of
approximately ten minutes. At this point, the assembly was returned
to the lens curing chamber and was dosed with four exposures
totaling 600 mJ/cm.sup.2 directed toward the back mold and four
exposures totaling 600 mJ/cm.sup.2 directed toward the front
mold.
[0594] The lens was removed from the mold assembly and post-cured
as described in Experiment 10.
[0595] The resulting lens was approximately 74 mm in diameter, had
a center thickness of 2.7 mm, and a distance focusing power of
+0.06 diopters. The resultant lens was dark green/grayish in color
and could be used as a sunglass lens. The optics of the lens were
crisp, without aberrations. The lens exhibited visible light
transmission of approximately 10%. When scanned with a Hewlett
Packard Model UV-Vis spectrophotometer, the lens transmitted
virtually no light at wavelengths less than 650 nm.
[0596] The sunglass lens of this example was cured using activating
light even though the lens forming composition included
ultraviolet/visible absorbing fixed pigments. Since such fixed
pigments tend to absorb a portion of the activating light strongly,
the activating light might not have penetrated to the depths of the
lens forming composition. The lens forming composition, however,
contained a co-initiator in conjunction with a photoinitiator to
help promote the curing of the entire lens forming composition. The
present example thus demonstrates that a sunglass lens containing
ultraviolet/visible light absorbing fixed pigments may be cured
using activating light, which includes ultraviolet/visible light,
to initiate polymerization of a lens forming composition that
contains a photoinitiator/co-initiator system.
Example 13
Altering the Activated color of a Photochromic Lens
[0597] According to a preferred embodiment, a polymerizable mixture
of PRO-629 (see above for a description of the components of
PRO-629), fixed pigments, a photoinitiator/co-initiator, and two
photochromic compounds was prepared in a manner similar to that
described in Example 12. The resulting lens forming composition
includes PRO-629, and the following components:
18 Material amount IRG-184 80 ppm IRG 819 280 ppm CN-384 1.0%
CN-386 1.0% Thermoplast Blue 0.67 ppm Thermoplast Red 0.04 ppm
Reversacol Sea Green 300 ppm Reversacol Berry Red 600 ppm
[0598] After the lens forming composition was prepared, a variety
of light effectors were added to the lens forming composition
described above. The modified lens forming composition was then
placed within a mold cavity, prepared as described in Example
12.
[0599] Both sides of the mold assembly was irradiated with two
doses of actinic light (e.g., light having a wavelength above about
380 nm). The first dose was applied for between 20 to 40 seconds.
The final dose was applied for about 5 minutes. The resulting lens
was demolded and treated with additional actinic light in a
post-cure unit. The formed lens was exposed to sunlight and the
activated color of the lens observed. The following table
summarizes the results when MEHQ, Tinuvin 400, ITX, and IRG-369 are
used as light effectors. S9 represents a lens formed without any
added light effectors.
19 EFFECTOR UV ACTIVATED SAMPLE EFFECTOR AMOUNT ABSORBANCE COLOR S9
None -- -- Gray S10 MEHQ 350 ppm 294-317 nm Brown S11 Tinuvin 400
1130 ppm 295-390 nm Aqua-Green S12 ITX 500 ppm 280-415 nm
Yellow-Green S13 IRG-369 300 ppm 290-390 nm Green
[0600] The activated color of the formed lens was noted after
exposing the formed lens to sunlight. The presence of light
effectors can have a significant effect on the color of the lens.
It should be noted that this change in color may be obtained
without altering the relative ratio of the photochromic compounds
(i.e., Berry Red and Sea Green). MEHQ which exhibits absorption in
the low ultraviolet light region tends to shift the color of the
lens toward red, thus causing the lens to take on a brown color
when exposed to sunlight. The absorbers Tinuvin 400, ITX, and
IRG-369 all tend to produce lenses having various green shades.
Because of the broad photochromic activating light absorbance range
of these compounds they may be effecting the photochromic activity
of both photochromic compounds.
[0601] The above examples represent specific examples of how an
activated color of a lens may be altered by the addition of a light
effector to a lens forming composition. By running similar studies
with other light effectors, the activated color of a lens may be
adjusted to a variety of different colors (e.g., red, orange,
yellow, green, blue, indigo, or violet) without changing the nature
of the photochromic compounds.
[0602] Further modifications and alternative embodiments of various
aspects of the invention will be apparent to those skilled in the
art in view of this description. Accordingly, this description is
to be construed as illustrative only and is for the purpose of
teaching those skilled in the art the general manner of carrying
out the invention. It is to be understood that the forms of the
invention shown and described herein are to be taken as the
presently preferred embodiments. Elements and materials may be
substituted for those illustrated and described herein, parts and
processes may be reversed, and certain features of the invention
may be utilized independently, all as would be apparent to one
skilled in the art after having the benefit of this description of
the invention. Changes may be made in the elements described herein
without departing from the spirit and scope of the invention as
described in the following claims.
* * * * *