U.S. patent application number 15/341313 was filed with the patent office on 2017-02-23 for method for molding an ophthalmic lens and device for applying a coating to the surface of an ophthalmic lens mold.
The applicant listed for this patent is Novartis AG. Invention is credited to Halina Heidrich, Axel Heinrich, Karsten Straube.
Application Number | 20170050344 15/341313 |
Document ID | / |
Family ID | 47080516 |
Filed Date | 2017-02-23 |
United States Patent
Application |
20170050344 |
Kind Code |
A1 |
Heidrich; Halina ; et
al. |
February 23, 2017 |
METHOD FOR MOLDING AN OPHTHALMIC LENS AND DEVICE FOR APPLYING A
COATING TO THE SURFACE OF AN OPHTHALMIC LENS MOLD
Abstract
There are described a method for applying a coating to a surface
of an ophthalmic lens mold. The mold includes male and female (20)
mold halves, with each of the mold halves being provided with a
lens forming surface (21). The method includes applying a temporary
coating to at least a portion of at least one of the male and
female mold halves (20), the temporary coating being capable of
reducing adhesive forces between a lens forming material and the
lens forming surface (21); and drying the temporary coating applied
to the portion of the lens forming surface (21). Also described is
a device (1) for applying such temporary coating to the portion of
the lens forming surface (21) of the ophthalmic lens mold.
Inventors: |
Heidrich; Halina; (Kahl am
Main, DE) ; Heinrich; Axel; (Aschaffenburg, DE)
; Straube; Karsten; (Lutherstadt Wittenberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Novartis AG |
Basel |
|
CH |
|
|
Family ID: |
47080516 |
Appl. No.: |
15/341313 |
Filed: |
November 2, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13660078 |
Oct 25, 2012 |
9511515 |
|
|
15341313 |
|
|
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61552536 |
Oct 28, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29D 11/00192 20130101;
B29C 33/58 20130101; B29D 11/00125 20130101; B29L 2011/0041
20130101 |
International
Class: |
B29C 33/58 20060101
B29C033/58; B29D 11/00 20060101 B29D011/00 |
Claims
1.-13. (canceled)
14. A device for applying a coating to a surface of an ophthalmic
lens mold, said lens mold comprising male and female mold halves,
each of said male and female mold halves being provided with a lens
forming surface, with a mold cavity being formed between said lens
forming surfaces of said male and female mold halves when the mold
is closed, said device comprising at least one coating head having
a coating face adapted to be contacted with said portion of said at
least one lens forming surface of said male and female mold halves,
said coating head being provided with feed and discharge ports
adapted to be connected with feed and discharge lines in order to
allow for a continuous flow of a temporary coating substance to and
from said coating face at least during contact of said coating face
with said portion of said lens forming surface of said at least one
of said male and female mold halves.
15. The device according to claim 14, wherein said coating face
comprises a curved outer surface generally matching a concave or
convex curvature of said lens forming surface of said male or
female mold half, respectively.
16. The device according to claim 14, wherein said coating face
comprises a mesh which is made of a material selected from the
group consisting of polyethylene, polypropylene,
polytetrafluoroethylene, polyamide, polyester, silk, steel, and
combinations of these materials.
17. The device according to claim 15, wherein said coating face
comprises a mesh which is made of a material selected from the
group consisting of polyethylene, polypropylene,
polytetrafluoroethylene, polyamide, polyester, silk, steel, and
combinations of these materials.
18. The device according to claim 16, wherein said mesh has a mesh
size (m) of about 25 .mu.m to about 1 mm.
19. The device according to claim 16, wherein said mesh is provided
with projections protruding from the coating face and having a
length in the range of about 50 .mu.m to about 2 mm.
20. The device according to claim 14, wherein the coating head
further comprises a homogenizer arranged upstream of said mesh.
21. The device according to claim 14, comprising two coating heads,
each one of said coating heads having a coating face, with the
coating face of one of said two coating heads being adapted to
apply a temporary coating to at least a portion of said lens
forming surface of said male mold half and said coating face of the
other of said two coating heads being adapted to apply a temporary
coating to at least a portion of said lens forming surface of said
female mold half.
Description
[0001] This application claims the benefit under 35 USC
.sctn.119(e) of U.S. provisional application Ser. No. 61/552,536
filed Oct. 28, 2011, incorporated herein by reference in its
entirety.
FIELD
[0002] The present disclosure relates to a method for molding an
ophthalmic lens, in particular a hard or a soft contact lens, and
to a device for applying a coating to the surface of an ophthalmic
lens mold, in particular to a lens mold for molding hard or soft
contact lenses.
BACKGROUND
[0003] Mass production of ophthalmic lenses, in particular hard or
soft contact lenses, is usually performed in a fully automated
process. One example for such process described in WO 98/42497. In
a preferred method of this fully automated mass production the
contact lenses are manufactured with reusable molds including male
and female mold halves. In one processing station a starting
material, e.g. a prepolymer solution, is dispensed into the female
mold halves, and the casting molds are then closed with the
corresponding male mold halves. Suitable polymers formed by
photochemical polymerization and/or cross-linking include polymers
based on polyvinyl alcohols (PVA) or silicone hydrogels (SiHy) as
well as polymers based on polyethylene glycols (PEG). To perform
the photochemical polymerization and/or cross-linking, the starting
material contained in the closed molds is exposed to radiation,
e.g. ultraviolet radiation. After the polymerization and/or
cross-linking step the molds are opened and the contact lenses so
formed are removed from the male or female mold halves and
transported to further processing stations.
[0004] Depending on the materials from which the lens forming
surfaces of the molds are made and further depending on the
materials the contact lenses are made of, the opening of the molds
and the removal of the polymerized and/or cross-linked contact
lenses from the male or female mold halves, respectively, may turn
out to be a cumbersome task. Adhesive forces between the lens
forming surfaces and the formed contact lens may require
considerably high forces to allow the opening of the molds and/or
to allow detachment and removal of the contact lens from the male
or female mold half. Reusable casting molds are known the lens
forming surfaces of which are made from highly finished glass, such
as, e.g., quartz glass. In combination with specific contact lens
materials, e.g. silicone hydrogels (SiHy), the high adhesive forces
between the lens forming surfaces and the contact lens may result
in an unacceptably high number of contact lenses getting damaged
upon opening the molds, and/or upon the subsequent detachment and
removal of the contact lenses from the male or female mold halves.
Such damages generally render the contact lenses unable to meet the
required quality standards.
[0005] In EP-0 686 469 and EP-0 740 997 it is suggested to provide
an annular flange region extending about a mold surface of a mold
half which may be constituted of suitable plastic materials with a
thin layer or film of a polymeric surfactant. The thin layer of
surfactant is supposed to facilitate removal of excess polymeric
material (HEMA) which forms a ring extending externally of the mold
cavity. The thin layer of surfactant is applied to the flange
regions of the mold halves in a stamping station using a stamping
head consisting of a plurality of stamps each of which is adapted
to engage respectively a flange region extending about the mold
surface. For transferring the polymer surfactant to the stamps a
pad arrangement including a reservoir for the surfactant is
provided. Alternatively, a brush may be provided which is adapted
for contacting the flange region of a mold and which may be
connected with a flexible tubing connection leading to a supply
source for the surfactant (EP-0 686 469).
[0006] The application of the surfactant to the flange region of a
mold assists in the separation of the male and female mold halves
during opening of the plastic molds, and in addition assists in the
removal of the HEMA-rings extending externally of the mold cavity
of the molds. These HEMA-rings may otherwise damage the contact
lens during demolding due to adhesion to the mold halves of the
plastic mold.
[0007] However, depending on the lens material used the problem of
detaching and removing the contact lens from the male and/or female
mold half remains unsolved, particularly in cases where the molded
contact lens strongly adheres to the lens forming surfaces of the
male and/or female mold halves, as this is the case with contact
lenses based on silicon hydrogels. As a result, considerably high
forces are still required for the separation of the mold halves,
that is to say for opening the mold. In addition, once the mold
halves have been separated (the mold has been opened) the contact
lenses continue to strongly adhere to the male mold half or to the
female mold half, respectively. Moreover, application of the high
forces required may result in damages to the ophthalmic lens. It is
therefore and object of the present invention to overcome these
problems and to provide a method and a device which reduces the
considerably high forces required to open the molds and which
facilitates detachment and removal of the ophthalmic lenses, e.g.
the contact lenses, from the male and female mold halves of the
opened lens molds. The solution to these problems shall be capable
of being fully integrated in an automated mass production process
for molding ophthalmic lenses, in particular soft and hard contact
lenses.
SUMMARY
[0008] In accordance with the invention a method for molding an
ophthalmic lens, in particular a soft or a hard contact lens, using
a mold including male and female mold halves is provided. Each of
the male and female mold halves is provided with a lens forming
surface, with a mold cavity being formed between the lens forming
surfaces of the male and female mold halves when the mold is
closed. The method includes the steps of: [0009] applying a
temporary coating to at least a portion of at least one of the lens
forming surfaces of the male and female mold halves, the temporary
coating being capable of reducing adhesive forces between a lens
forming material and the lens forming surface; [0010] drying the
temporary coating applied to the at least one portion of the at
least one of the lens forming surfaces; [0011] introducing a lens
forming material into the female mold half; [0012] assembling the
male and female mold halves to close the mold; [0013] curing the
lens forming material in the mold cavity formed between the lens
forming surfaces of the male and female mold halves to form the
ophthalmic lens; [0014] opening the mold; and [0015] removing the
ophthalmic lens from the male mold half or from the female mold
half.
[0016] By providing at least a portion of at least one of the lens
forming surfaces of the male and female mold halves with a
temporary coating the adhesive forces between the ophthalmic lens
and the lens forming surface are considerably reduced. This
facilitates both the separation of the mold halves, that is to say
opening the mold, as well as the detachment and removal of the
polymerized and/or cross-linked ophthalmic lens from the male or
female mold halves, respectively, and helps to either completely or
at least to a large extent avoid damages to the ophthalmic lens.
Thus, the number of ophthalmic lenses which do not meet the
required quality standards can at least be greatly reduced. The
process steps of coating at least a portion of the lens forming
surface(s) of the male and female mold halves and drying the
applied temporary coating can be easily integrated as additional
steps in a fully automated mass production of ophthalmic lenses,
which can be performed before the lens forming material is
dispensed into the female mold half.
[0017] In one embodiment of the method according to the invention,
the temporary coating is removed from the at least one portion of
the at least one lens forming surface of the male and female mold
halves after having removed the ophthalmic lens from the male and
female mold halves. The removal of the temporary coating may not
require additional process steps or additional process time, it may
be performed together with the general cleaning of the (reusable)
mold halves before reusing them to form the next ophthalmic lens,
e.g. contact lens. Accordingly, every contact lens is formed using
a freshly coated mold or mold half so as to ensure the quality of
the coating and, as a consequence, the quality of the molded
ophthalmic lenses. The coating material is selected so as to be
compatible with both the material of the mold halves and the lens
forming material which is introduced into the female mold half
after the coating and drying of the at least one lens forming
surface of the male and female mold halves of a mold.
[0018] In a further embodiment of the method according to the
invention the temporary coating is applied to the entire lens
forming surface of at least one of the male and female mold halves.
By applying the coating to the entire lens forming surface(s) of
the casting mold, the adhesive forces may be reduced even further.
It goes without saying that while the temporary coating may be
applied to only at least a portion of one of the lens forming
surfaces of the male and female mold halves, it may well be applied
to at least a portion of the lens forming surfaces of both the male
and female mold halves, and may also be applied to the entire lens
forming surfaces of both the male and female mold halves.
[0019] In automated mass production processes for the manufacture
of ophthalmic lenses, in particular soft and hard contact lenses,
reusable molds may be used which include lens forming surfaces
which are made of glass, such as, e.g., quartz glass. Due to the
design of the mold halves, excess lens forming material may be
displaced in a controlled manner to an annular space outside the
mold cavity and surrounding the mold cavity as the mold halves are
assembled to form a closed mold. In order to further reduce any
additional adhesive forces caused by the displaced excess lens
material, e.g. when opening the mold, in another embodiment of the
method according to the invention the temporary coating is also
applied to an annular region of the male and female mold halves
outside the lens forming surface.
[0020] In an advantageous embodiment of the method according to the
invention, the temporary coating may be applied in liquid form.
[0021] In a further embodiment of the method according to the
invention, the liquid temporary coating is applied to the lens
forming surface with the aid of a coating head capable of
maintaining a continuous flow of the liquid to and from a coating
face of the coating head during the application step. The
continuous flow of the liquid assists in obtaining a uniform liquid
coating on the lens forming surface so that there are no uncoated
areas.
[0022] In a further embodiment of the method according to the
invention, the liquid is applied to the lens forming surface to
form a film having a thickness in the range of about 100 .mu.m to
about 200 .mu.m. This thin film allows to obtain a smooth uniform
temporary coating of the lens forming surface, this uniform film
being maintained at least until after the drying step, thus
resulting in a uniform smooth coating of the coated portion of the
lens forming surface.
[0023] Generally, the temporary coating can be selected taking the
properties of the lens forming material and the material of the
lens forming surfaces of the mold halves into account. However, in
one particular embodiment of the method according to the invention
the temporary coating is selected from the group consisting of
polyvinylalcohol and copolymers of vinylalcohole;
polyvinylpyrrolidone (e.g. Kollidon.RTM. from BASF); copolymers of
N-vinylpyrrolidone with e.g. vinylacetate (Luviskole.RTM. from
BASF), polytetrahydrofurane, polyethylene glycols, polypropylene
glycols, copolymers of polyethylene glycols with polypropylene
glycols (e.g. Pluronics.RTM. or Tetronics.RTM. from BASF),
polyacrylamide and copolymers thereof, e.g. with acrylic acid;
poly(vinylpyridine) and copolymers thereof.
[0024] While drying of the applied temporary coating may be
performed in various manners, in one embodiment of the method
according to the invention the step of drying the temporary coating
is performed using infrared radiation which is a fast and
convenient way for drying the applied temporary coating.
[0025] As already mentioned, the removal of the temporary coating
after the ophthalmic lens has been detached and removed from the
male and female mold halves can be accomplished during the regular
course of cleaning the mold halves. Accordingly, in one embodiment
of the method according to the invention the step of removing the
temporary coating is performed by exposing the respective coated
lens forming surface to a rinsing liquid, such as, e.g., water,
water with additives and solvents.
[0026] While the method according to the invention is generally
applicable in connection with many contact lens forming materials,
in one embodiment of the invention the lens forming material is
selected from the group consisting of polymers based on polyvinyl
alcohols (PVA), silicone hydrogels (SiHy), and polyethylene glycols
(PEG). In particular the silicone hydrogel (SiHy) materials--while
having advantageous lens properties--tend to generate considerably
high adhesive forces, so that the method according to the invention
is particularly suitable for these materials.
[0027] Another aspect of the invention relates to a device for
applying a coating to a surface of an ophthalmic lens mold, in
particular a lens mold for molding hard or soft contact lenses. The
lens mold includes male and female mold halves, each of the male
and female mold halves being provided with a lens forming surface,
with a mold cavity being formed between the lens forming surfaces
of the male and female mold halves when the mold is closed. The
device includes at least one coating head having a coating face
adapted to be contacted with the portion of the at least one lens
forming surface of the male and female mold halves. The coating
head is provided with feed and discharge ports adapted to be
connected with feed and discharge lines in order to allow for a
continuous flow of a temporary coating substance to and from the
coating face at least during contact of the coating face with the
portion of the lens forming surface of the at least one of the male
and female mold halves.
[0028] The coating head, by allowing for a continuous flow of the
temporary coating substance to at least a portion of the lens
forming surface, enables the deposition of a uniform film of the
temporary coating substance, typically a liquid, on the lens
forming surface so that there are no uncoated areas. The film
typically has a thickness in the range of about 100 .mu.m to about
200 .mu.m. This thin film allows to obtain a smooth uniform
temporary coating of the lens forming surface, the uniform film
being maintained at least until after the drying step, thus
resulting in a uniform smooth coating of the coated portion of the
lens forming surface.
[0029] In one embodiment of the device according to the invention,
the coating face includes a curved outer surface generally matching
a concave or convex curvature of the lens forming surface of the
male or female mold half, respectively.
[0030] In another embodiment of the device according to the
invention, the coating face includes a mesh which is made of a
material selected from the group consisting of polyethylene,
polypropylene, polytetrafluoroethylene, polyamide, polyester, silk,
steel, and combinations of these materials. The materials for the
mesh are selected such that they do not cause damage to the lens
forming surface(s) as they contact the lens forming surface(s).
[0031] In a further embodiment of the device according to the
invention, the mesh has a mesh size of about 25 .mu.m to about 1
mm. The mesh size is selected such that it may be penetrated by the
liquid coating substance and that it enhances a uniform
distribution thereof across the mesh and, as a consequence, across
the contacted lens forming surface. At the same time, the mesh size
is selected to allow an easy cleaning of the mesh after application
of the liquid coating substance to the lens forming surface.
[0032] In a further embodiment of the device according to the
invention, the mesh is provided with projections protruding from
the coating face and having a length in the range of about 50 .mu.m
to about 2 mm. The protrusions result in a certain minimum distance
of the rest of the mesh from the lens forming surface to be coated
and, together with the distance between adjacent protrusions, they
allow removal of the coating head from the lens forming surface
once the film has been uniformly applied to the lens forming
surface without breaking of the film due to adhesion forces.
[0033] In a still further embodiment of the device according to the
invention, the coating head further includes a homogenizer arranged
upstream of the mesh. The homogenizer further improves an even
distribution of the coating substance subsequently applied through
the mesh. By way of example, the homogenizer may include one or
more ceramic tiles.
[0034] A still further embodiment of the device according to the
invention includes two coating heads, each one of the coating heads
having a coating face, with the coating face of one of the two
coating heads being adapted to apply a temporary coating to at
least a portion of the lens forming surface of the male mold half
and the coating face of the other of the two coating heads being
adapted to apply a temporary coating to at least a portion of the
lens forming surface of the female mold half. It is immediately
evident, that this embodiment is particularly suitable to
simultaneously apply a coating to the lens forming surfaces of both
the male and female mold halves of a mold.
[0035] It is to be understood that in automated productions lines
for the mass production of ophthalmic lenses, in particular soft or
hard contact lenses, a larger number of casting molds may be
arranged in side by side configuration, in order to simultaneously
manufacture a plurality of lenses at a time. Thus, a corresponding
number of devices for applying a temporary coating to the lens
forming surfaces of the female and/or male mold halves,
respectively, may likewise be arranged in side by side
configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The afore-mentioned advantages of the invention will become
apparent from the following description of an exemplary embodiment
of the invention. The embodiment described is not intended to limit
the invention to the embodiment. In particular, the embodiment
described below is related to the manufacturing of contact lenses,
which is by way of example only. In the following description,
reference is made to the schematic drawings which are not to scale,
in which
[0037] FIG. 1 shows a sectional view of a device for applying a
temporary coating to a lens forming surface of a female mold half;
and
[0038] FIG. 2 shows the detail II of FIG. 1 at a larger scale.
DETAILED DESCRIPTION OF EMBODIMENTS
[0039] In FIG. 1 a device for applying a temporary coating to a
lens forming surface of a mold half is generally designated with
reference numeral 1. More specifically, the device shown in FIG. 1
includes a coating head 2 which is in contact with a lens forming
surface 21 of a female mold half 20 of a contact lens mold. The
lens forming surface 21 of the female mold half 20 is of generally
concave shape and is embodied as an insert 23 which can be made of
glass, e.g. BK7 or quartz-glass, the insert 23 being arranged in a
mount 24 which can be made of metal, for example. A support 25
houses mount 24 with the insert 23 arranged therein. The lens
forming surface 21 of female mold half 20 is surrounded by an
annular flange region 22.
[0040] Coating head 2 includes a housing 3 provided with feed and
discharge ports 4, 5 adapted to be connected with tubular lines.
The coating head 2 may be attached to a means (not shown) for
moving the coating head 2 towards and away from the female mold
half 20, this being indicated by the double arrow P. In a space 9
inside the housing 3 a homogenizer 10 is arranged, which may
include one or more ceramic tiles. The device further includes a
mesh 6 mounted to the housing on that side of coating head 2 facing
female mold half 20. The mesh 6 can be made of polyethylene,
polypropylene, polytetrafluoroethylene, polyamide, polyester, silk,
steel, and the like. The front side of the mesh 6, i.e. that side
of the mesh facing lens forming surface 21 of female mold half 20,
represents a coating face 7 which, in use, contacts the lens
forming surface 21 of the female mold half 20. The coating face 7
has a curvature which is generally complementary to the curvature
of lens forming surface 21. In the embodiment shown the coating
face 7 is of convex shape and curvature in order to match the
concave-shaped lens forming surface 21 of the female mold half 20.
It goes without saying, that in order to apply a temporary coating
to a male mold half having a convex-shaped lens forming surface the
coating head will be provided with a coating face of concave shape
and matching curvature.
[0041] FIG. 2 shows the encircled detail II of FIG. 1 at a larger
scale. From FIG. 2 it becomes clear that the mesh 6 is a network
having a mesh size m which may be in the range of about 25 .mu.m to
about 1 mm. The mesh is provided with projections 8 protruding from
the coating face 7. These projections 8 may a length l in the range
of about 50 .mu.m to about 2 mm. In use, the projections 8 contact
the lens forming surface 21 of the female mold half 20 so that the
coating face 7 is arranged at a distance from the lens forming
surface 21.
[0042] The device for applying a temporary coating to a lens
forming surface of a mold half may be integrated into an automated
productions line for contact lenses, upstream of a processing
station, in which the casting molds are filled with a lens forming
material, such as polymers based on polyvinyl alcohols (PVA),
silicone hydrogels (SiHy), and polyethylene glycols (PEG). Flexible
tubular lines may be connected with the feed and discharge ports 4,
5 in order to supply a coating liquid to the coating head 2. The
coating liquid may be polyvinylalcohol and copolymers of
vinylalcohol; polyvinylpyrrolidone (e.g. Kollidon.RTM. from BASF);
copolymers of N-vinylpyrrolidone with e.g. vinylacetate
(Luviskole.RTM. from BASF), polytetrahydrofurane, polyethylene
glycols, polypropylene glycols, copolymers of polyethylene glycols
with polypropylene glycols (e.g. Pluronics.RTM. or Tetronics.RTM.
from BASF), polyacrylamide and copolymers thereof, e.g. with
acrylic acid; poly(vinylpyridine) and copolymers thereof. The
coating liquid enters the coating head 2 via feed port 4, as
indicated in FIG. 1 by the arrow I, and is evenly distributed by
flowing through the homogenizer 10 before it reaches the mesh 6.
The mesh size m allows the coating liquid to penetrate the mesh 6
and reach the coating face 7. The effect of the projections 8 is
that the rest of the mesh 6 is arranged at a distance from the lens
forming surface 21. This distance depends on the length of the
projections 8. The coating liquid is applied to the lens forming
surface 21 of the female mold half through the mesh 6 and between
projections 8. The projections 8 serve to reduce adhesive forces
that occur as the coating head 2 is moved away from the coated lens
forming surface 21 surface in order to prevent a break of the
liquid film. In this manner, a smooth uniform film of a liquid
coating substance can be applied to the lens forming surface 21.
This film may have a thickness which may be in the range of about
100 .mu.m to about 200 .mu.m and is maintained until it is
subsequently dried, e.g. with the aid of infrared (IR) radiation so
as to form a temporary coating on the lens forming surface 21 of
the female mold half. Optionally, the temporary coating may be
applied to the annular region 22 as well, but this is not provided
for in the embodiment described.
[0043] During application of the liquid coating substance, the
liquid coating substance is continuously transported through
coating head 2. It exits coating head 2 through discharge port 5 as
indicated in FIG. 1 by arrow O, so that during application of the
liquid coating substance there is a continuous flow of liquid over
the lens forming surface 21. Once application of the liquid coating
substance is completed and the film is properly formed on the lens
forming surface 21, the coating head 2 is moved away from lens
forming surface 21 and the liquid film on lens forming surface 21
is dried by subjecting the liquid film on lens forming surface 21
to infrared radiation. The temporary coating of lens forming
surface is then completed. The female mold half 20 may then be
filled with the lens forming material, and the mold may then be
closed by assembling the male and female mold halves to form a mold
cavity between the lens forming surfaces of the male and female
mold halves, the mold cavity determining the shape of the contact
lens to be manufactured. During closing of the mold with the aid of
the male mold half, any excess lens forming material may be
displaced into an annular space formed by the annular regions of
the male and female mold halves. The lens forming material inside
the mold cavity may then be polymerized and/or cross-linked e.g. by
irradiation with ultraviolet radiation, as this is known in the
art. When the mold is closed the annular space may be in
communication with the mold cavity so that in case shrinkage occurs
during polymerization and/or cross-linking of the lens forming
material contained in the mold cavity additional material may flow
from the annular space into the mold cavity so as to compensate for
that shrinkage.
[0044] Once polymerization and/or cross-linking has been completed,
the mold halves are separated from one another, that is to say the
mold is opened, and the so formed contact lens is removed from the
male mold half or from the female mold half, respectively, for
further processing. The contact lens molds are then cleaned so as
to be reused after cleaning. During this ordinary cleaning of the
mold halves which is usually performed using water as a rinsing
liquid, the temporary coating is also removed from the lens forming
surface 21. Alternatively, other rinsing liquids such as water with
additives and solvents and the like may be used. Thus, the removal
of the temporary coating does not require an additional process
step but may be performed together with the ordinary process of
cleaning the mold halves. After cleaning, the mold halves may be
used again to form the next contact lens in the automated lens
production process.
[0045] In the embodiment, coating of the entire lens forming
surface of a female mold half has been described. It is to be noted
though, that the lens forming surface does not necessarily have to
be entirely coated. In certain instances it may be sufficient to
apply the temporary coating only to a part of the lens forming
surface. Also, while it has been described that the temporary
coating is applied to the female mold half, the temporary coating
can alternatively be applied to the male mold half, and in
particular to both the male and female mold halves of a mold. As
already indicated, the temporary coating may in addition be
provided to the annular region surrounding the lens forming surface
of the male and/or female mold half, respectively.
* * * * *