U.S. patent application number 09/834164 was filed with the patent office on 2001-09-06 for display apparatus with corrosion-resistant light directing film.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Epstein, Kenneth A., Fleming, Robert J., Gardner, Timothy J., Lyons, Christopher S., Maki, Stephen P., Nachbor, Mark D..
Application Number | 20010019452 09/834164 |
Document ID | / |
Family ID | 23687941 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019452 |
Kind Code |
A1 |
Epstein, Kenneth A. ; et
al. |
September 6, 2001 |
Display apparatus with corrosion-resistant light directing film
Abstract
The present invention is a display apparatus that provides
protection against damage for a metallic layer. The display
apparatus includes a light modulating layer, a polarizer, and a
light directing film. The light directing film includes a prismatic
structure having two sides, where one side includes saw tooth
formations having tilted surfaces and a metal layer on the side of
the prismatic substrate having the saw-tooth formations. A tilt
angle of the tilted surfaces offsets an optimal viewing angle for
the display from a glare angle for the display. In a first
embodiment of the invention, the light directing film of the
display apparatus further includes an inorganic protective layer
formed on the metal layer, wherein the inorganic protective layer
inhibits molecular transfer to the metal layer and balances the
color of reflected and transmitted light. The light directing film
further includes a pressure sensitive adhesive layer between a
polarizer and the inorganic protective layer. Alternatively, the
light directing film of the display apparatus of the present
invention includes a polymer protective layer formed over the metal
layer to protect the metal layer from damage. The light directing
film also includes a diffuse adhesive layer formed over the polymer
layer, attached to the polarizer. The polymer protective layer
protects the metal layer from the adhesive layer. The display
apparatus may include both the inorganic protective layer and the
polymer protective layer, in one embodiment.
Inventors: |
Epstein, Kenneth A.; (St.
Paul, MN) ; Fleming, Robert J.; (Lake Elmo, MN)
; Gardner, Timothy J.; (Inver Grove Heights, MN) ;
Lyons, Christopher S.; (St. Paul, MN) ; Maki, Stephen
P.; (North St. Paul, MN) ; Nachbor, Mark D.;
(Plymouth, MN) |
Correspondence
Address: |
MERCHANT & GOULD PC
1050 17TH STREET, SUITE 1400
DENVER
CO
80265
US
|
Assignee: |
3M Innovative Properties
Company
St. Paul
MN
|
Family ID: |
23687941 |
Appl. No.: |
09/834164 |
Filed: |
April 12, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
09834164 |
Apr 12, 2001 |
|
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|
09425765 |
Oct 22, 1999 |
|
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6264336 |
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Current U.S.
Class: |
359/606 ;
359/488.01; 359/489.06; 359/489.15; 359/493.01; 359/614; 359/615;
359/831 |
Current CPC
Class: |
G02F 1/133504 20130101;
G02F 2202/022 20130101; G02F 1/133345 20130101; G02F 1/133553
20130101 |
Class at
Publication: |
359/606 ;
359/614; 359/615; 359/483; 359/831 |
International
Class: |
G02B 005/30; G02B
027/28; G02B 005/08; G02B 017/00; G02B 027/00; G02B 005/04; G02B
007/18 |
Claims
We claim:
1. A display apparatus comprising: a light modulating layer; a
polarizer; and a light directing film, comprising: a prismatic
structure having two sides, one side including saw-tooth formations
having tilted surfaces; a metal layer on the side of the prismatic
substrate having the saw-tooth formations; an inorganic protective
layer formed on the metal layer, wherein the inorganic protective
layer inhibits molecular transfer to the metal layer; and a
pressure sensitive adhesive layer between the polarizer and the
inorganic protective layer; wherein the display apparatus has a
glare angle at which front surface glare is viewed and wherein a
tilt angle of the tilted surfaces offsets an optimal viewing angle
for the display from the glare angle; wherein the inorganic
protective layer protects the metal layer and balances the color of
reflected and transmitted light.
2. The display apparatus of claim 1, wherein the pressure sensitive
adhesive layer comprises an acrylate acrylic acid adhesive layer,
the adhesive layer being optically diffuse, and wherein the
adhesive layer inhibits damage to the metal layer.
3. The display apparatus of claim 1, wherein the pressure sensitive
adhesive layer includes optical diffuser particles.
4. The display apparatus of claim 1, wherein the inorganic
protective layer is selected from the group consisting of titanium
and titanium oxides.
5. The display apparatus of claim 4 wherein the inorganic
protective layer has a thickness greater than or equal to about 10
angstroms and less than or equal to about 3000 angstroms.
6. The display apparatus of claim 1, wherein the inorganic
protective layer is selected from the group consisting of indium
tin oxide, zinc sulfide, tin oxide, indium oxide, and titanium
oxide.
7. The display apparatus of claim 6 wherein the inorganic
protective layer has a thickness greater than or equal to about 300
angstroms and less than or equal to about 1000 angstroms.
8. The display apparatus of claim 1, wherein the inorganic
protective layer is selected from the group consisting of silicon
dioxide, silicon monoxide, and magnesium fluoride.
9. The display apparatus of claim 8 wherein the inorganic
protective layer has a thickness greater than or equal to about 300
angstroms and less than or equal to about 1500 angstroms.
10. The display apparatus of claim 1, the light directing film
further comprising a polymer protective layer, formed on the
inorganic protective layer, the pressure sensitive adhesive layer
being between the polymer protective layer and the polarizer,
wherein the polymer protective layer impedes molecular transfer to
the metal layer.
11. The display apparatus of claim 10, wherein the polymer
protective layer is selected from a group consisting of polyester,
soluble polyester, cross-linked epoxy resin, acrylic resin, epoxy
acrylate, polyethylene, polyvinylidene chloride, polyvinyl alcohol
and polymethyl methacrylate.
12. The display apparatus of claim 11 wherein the polymer
protective layer is formed by vapor deposited and cured polymer
precursor materials.
13. The display apparatus of claim 12 wherein the polymer
protective layer is formed by condensing a vaporized liquid
composition containing a monomer or prepolymer onto the metal
layer.
14. The display apparatus of claim 12 wherein the polymer
protective layer is cured using a process selected from the group
of thermal radiation, ultraviolet radiation, electron beam
radiation, plasma exposure and corona exposure.
15. The display apparatus of claim 14 wherein the polymer
protective layer has a thickness of about 1 nanometer to 2
micrometers.
16. The display apparatus of claim 10 wherein the polymer
protective layer is formed by a plasma process selected from the
group consisting of plasma-polymerization and plasma-enhanced
chemical vapor deposition.
17. The display apparatus of claim 10, wherein the polymer
protective layer has a thickness of about 100 to 5000
Angstroms.
18. The display apparatus of claim 10, wherein the polymer
protective layer includes one side having tilted surfaces
corresponding to the tilted surfaces of the prismatic structure and
a second side being substantially planar.
19. The display apparatus of claim 10, wherein the polymer
protective layer includes polymethyl methacrylate.
20. The display apparatus of claim 10, wherein the polymer
protective layer is solution coated.
21. The display apparatus of claim 1 further comprising a polymer
substrate.
22. The display apparatus of claim 21, the polymer substrate
comprising a material selected from the group of PET, polyether
sulphone, polycarbonate, cellulose diacetate, and cellulose
triacetate.
23. The display apparatus of claim 21, the polymer substrate being
birefringent.
24. The display apparatus of claim 21, the polymer substrate being
non-birefringent.
25. The display apparatus of claim 21, the polymer substrate having
a thickness of greater than or equal to about 25 microns and less
than or equal to about 1000 microns.
26. The display apparatus of claim 1, the prismatic structure
comprising cured resin.
27. The display apparatus of claim 1, the prismatic structure
comprising UV curable cross-linked epoxy-acrylate.
28. The display apparatus of claim 1, the metal layer comprising a
material selected from a group consisting of silver, chromium,
nickel, aluminum, titanium, aluminum-titanium alloy, gold,
zirconium, platinum, palladium, aluminum-chromium alloy and
rhodium.
29. The display apparatus of claim 1, the metal layer having a
thickness greater than or equal to about 25 angstroms and less than
or equal to about 3000 angstroms.
30. The display apparatus of claim 1, wherein the metal layer is
vacuum deposited.
31. The display apparatus of claim 1, wherein the metal layer is
deposited by plating.
32. The display apparatus of claim 1, further comprising a light
cavity for providing light to the light modulating layer, adjacent
to the prismatic polymer substrate, wherein the metal layer is
partially transmissive.
33. The display apparatus of claim 1, wherein the pressure
sensitive adhesive layer includes one side having tilted surfaces
corresponding to the tilted surfaces of the prismatic structure and
a second side being substantially planar.
34. The display apparatus of claim 1, further comprising a cured
polymer layer between the metal layer and the pressure sensitive
adhesive layer, the cured polymer layer including one side having
tilted surfaces corresponding to the tilted surfaces of the
prismatic structure and a second side being substantially
planar.
35. The display apparatus of claim 1, wherein the pressure
sensitive adhesive layer is incorporated into the polarizer.
36. The display apparatus of claim 1, wherein the pressure
sensitive adhesive layer is incorporated into the prismatic polymer
substrate.
37. A display apparatus of claim 1, wherein the prismatic layer
includes tilted surfaces with a tilt angle of about 1.degree. or
more and about 35.degree. or less from horizontal.
38. A display apparatus of claim 1, wherein the prismatic layer
includes tilted surfaces with a tilt angle of about 3.degree. or
more and about 12.degree. or less from horizontal.
39. A display apparatus of claim 1, wherein the prismatic layer
includes tilted surfaces with a tilt angle of about 6.degree. or
more and about 9.degree. or less from horizontal.
40. A display apparatus of claim 1, wherein the saw-tooth
formations have a repeat distance of about 5 microns or more and
about 200 microns or less.
41. A display apparatus of claim 1, wherein the saw-tooth
formations have a repeat distance of about 30 microns or more and
about 80 microns or less.
42. A display apparatus of claim 1, wherein the saw-tooth
formations have a repeat distance of about 50 microns.
43. A display apparatus comprising: a light modulating layer; a
polarizer; and a light directing film, comprising: a polymer
substrate; a prismatic structure having two sides, one side
including saw-tooth formations having tilted surfaces; a metal
layer on the side of the prismatic substrate having saw-tooth
formations; a polymer protective layer formed over the metal layer;
and a diffuse adhesive layer formed over the polymer layer,
attached to the polarizer; wherein the display apparatus has a
glare angle at which front surface glare is viewed and a tilt angle
of the tilted surfaces of the saw-tooth formations offsets an
optimal viewing angle for the display from the glare angle; wherein
the polymer protective layer protects the metal layer from mobile
reactive species in the adhesive layer.
44. The display apparatus of claim 43 wherein the metal layer
comprises a silver layer having a thickness of about 400
angstroms.
45. The display apparatus of claim 43 wherein the polymer
protective layer is selected from a group consisting of soluble
polyester, epoxy resin, acrylic resin, epoxy acrylate,
polyethylene, polyvinylidene chloride, and polyvinyl alcohol.
46. The display apparatus of claim 43 wherein the polymer
protective layer comprises polymethyl methacrylate.
47. The display apparatus of claim 46 wherein the polymer
protective layer has a thickness of about 10 microns.
48. The display apparatus of claim 43 wherein the polymer
protective layer comprises one side adjacent to the saw tooth
formations and a second side that is substantially planar.
49. The display apparatus of claim 43 wherein the diffuse adhesive
layer comprises butyl acrylate acrylic acid.
50. The display apparatus of claim 43 wherein the prismatic
structure comprises UV curable epoxy acrylate.
51. The display apparatus of claim 43 wherein the saw-tooth
formations include tilted surfaces at about 6 degrees or more and
about 9 degrees or less.
52. A display apparatus of claim 43, wherein the saw-tooth
formations have a repeat distance of about 5 microns or more and
about 200 microns or less.
53. A display apparatus of claim 43, wherein the saw-tooth
formations have a repeat distance of about 30 microns or more and
about 80 microns or less.
54. A display apparatus of claim 43, wherein the saw-tooth
formations have a repeat distance of about 50 microns.
55. The display apparatus of claim 43 wherein the polymer substrate
is PET.
56. A display apparatus comprising: a light modulating layer; a
polarizer; a light directing film comprising: a polymer substrate;
a prismatic structure having two sides, one including saw-tooth
formations having tilted surfaces; a silver layer on the side of
the prismatic substrate having saw-tooth formations; a polymer
protective layer of polymethyl methacrylate formed over the silver
layer; and a diffusive adhesive layer formed over the polymer
protective layer, adhered to the polarizer; wherein the display
apparatus has a glare angle at which front surface glare is viewed
and a tilt angle of the tilted surfaces of the saw-tooth formations
offsets an optimal viewing angle for the display from the glare
angle; wherein the polymer protective layer protects the silver
layer from the adhesive layer.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to a light directing
arrangement and method for use with a display apparatus, and more
particularly to a light directing arrangement that is resistant to
corrosion and directs an image to an angle different from a glare
angle.
BACKGROUND OF THE INVENTION
[0002] Liquid crystal displays (LCD) are used in many different
types of electronic devices, including portable computers, cellular
phones, and digital watches. One class of LCD, which is
substantially reflective, often includes a reflector for directing
ambient light to the viewer. Another class of LCD often includes a
partially transmissive reflector for also allowing light from a
light source within the device to convey information to the viewer.
A partially transmissive reflector is commonly called a
transflector, and an LCD that incorporates a transflector is
commonly called transflective. The reflector may be made of metal
or other types of composite materials. Some examples of LCD devices
are discussed in co-pending application, "Optical Devices Using
Reflecting Polarizing Materials", Ser. No. 09/298,003, filed Apr.
22, 1999.
SUMMARY OF THE INVENTION
[0003] The present invention is a display apparatus that provides
protection against corrosion for a metallic layer. The display
apparatus includes a light modulating layer sandwiched between two
polarizers and a light directing film. The light directing film
includes a prismatic structure having two sides, where one side
includes saw-tooth formations having tilted surfaces, and a metal
layer on the side of the prismatic substrate having the saw-tooth
formations. The tilt angle of the tilted surfaces offsets an
optimal viewing angle for the display from a glare angle for the
display.
[0004] In a first embodiment of the invention, the light directing
film of the display apparatus further includes an inorganic
protective layer formed on the metal layer, wherein the inorganic
protective layer inhibits molecular transfer to the metal layer and
balances the color of reflected and transmitted light. The light
directing film further includes a pressure sensitive adhesive layer
between a polarizer and the inorganic protective layer.
[0005] The pressure sensitive adhesive layer may be an acrylate
acrylic acid adhesive layer, the adhesive layer being optically
diffuse, wherein the adhesive layer inhibits corrosion of the metal
layer, in one embodiment of the invention. The pressure sensitive
adhesive layer may include optical diffuser particles. The
inorganic protective layer may be one or more materials selected
from the group consisting of titanium, indium tin oxide, zinc
sulfide, tin oxide, indium oxide, titanium oxide, silicon dioxide,
silicon monoxide, and magnesium fluoride. The metal layer may be
selected from one or more of the group consisting of silver,
chromium, nickel, aluminum, titanium, aluminum-titanium alloy,
gold, zirconium, platinum, palladium, aluminum-chromium alloy and
rhodium. The metal layer is preferably silver. The prismatic
structure may be made of cured resin, such as a UV curable
cross-linked epoxy-acrylate.
[0006] The display apparatus may also include a light cavity for
providing light to the light modulating layer, adjacent to the
prismatic polymer substrate, wherein the metal layer is partially
transmissive.
[0007] The tilted surfaces of the prismatic layer may have a tilt
angle of about 1.degree. to 35.degree. from horizontal, more
preferably about 3.degree. to 12.degree. from horizontal, and most
preferably about 6.degree. to 9.degree. from horizontal, in one
application. The saw-tooth formations may have a repeat distance of
about 5 microns or more and about 200 microns or less, more
preferably about 30 microns or more and about 80 microns or less,
and most preferably about 50 microns, for one application.
[0008] In a second embodiment of the present application, a polymer
protective layer is formed over the metal layer to protect the
metal layer from corrosion. The light directing film also includes
a diffuse adhesive layer formed over the polymer layer, attached to
the polarizer. The polymer protective layer protects the metal
layer from the mobile reactive species in the adhesive layer. The
polymer protective layer may be selected from a group consisting of
cross-linked epoxy, cross-linked or linear acrylic resin, soluble
polyester, polyethylene, polyvinylidene chloride, polyvinyl alcohol
and polymethyl methacrylate.
[0009] The polymer protective layer may be formed by solution
coating in a preferred embodiment, in which case the thickness can
range from about 0.01 micron to about 50 microns. Alternatively,
the polymer protective layer may be formed by the vapor deposition
and subsequent curing of a polymer precursor onto the metal layer.
The protective layer may be cured using a process selected from the
group of thermal radiation, ultraviolet radiation, electron beam
radiation, plasma exposure and corona exposure. In the case of
formation using vapor deposition, the polymer protective layer may
have a thickness of about 1 nanometer to 2 micrometers.
[0010] Alternatively, the polymer protective layer may be formed by
a plasma process selected from the group consisting of
plasma-polymerization and plasma-enhanced chemical vapor
deposition. Preferably, the polymer protective layer is a solution
coated polymethyl methacrylate. Preferably, the metal layer is a
silver layer having a thickness of about 400 Angstroms. The diffuse
adhesive layer may preferably be butyl acrylate acrylic acid
adhesive.
[0011] The display apparatus of the present invention may include
both the inorganic protective layer and the polymer protective
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention may be more completely understood by
considering the detailed description of various embodiments of the
invention which follows in connection with the accompanying
drawings.
[0013] FIG. 1 is a cross-sectional view of a display apparatus of
one embodiment of the present invention, including a light
directing film.
[0014] FIG. 2 is a cross-sectional view of a display apparatus of
another embodiment of the present invention, including a light
directing film and a light cavity.
[0015] FIG. 3 is a cross-sectional view of one embodiment of a
light directing film of the present invention, before incorporation
into a display apparatus.
[0016] FIG. 4 is a cross-sectional view of a second embodiment of a
light directing film of the present invention.
[0017] FIG. 5 illustrates time versus reflectivity during
weathering for a silver/indium tin oxide film.
[0018] FIG. 6 illustrates time versus reflectivity during
weathering of a silver/zinc sulfide film.
[0019] FIG. 7 illustrates the transmission spectra for a
silver/indium tin oxide coating on a light directing film.
[0020] FIG. 8 shows the reflection spectra for a silver/indium tin
oxide coating on a light directing film.
[0021] FIG. 9 illustrates the reflectance of an LCD versus the
viewing angle for four different types of LCD's, where each LCD
incorporates a different type of transflector.
[0022] FIG. 10 is a cross-sectional view of another embodiment of a
light directing film of the present invention.
[0023] FIG. 11 is a cross-sectional view of another embodiment of a
light directing film of the present invention.
[0024] FIG. 12 is a cross-sectional view of another embodiment of a
light directing film of the present invention.
[0025] FIG. 13 is a cross-sectional view of another embodiment of a
light directing film of the present invention.
[0026] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to particular embodiments described. On the contrary, the
intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] The present invention is believed to be applicable to a
variety of systems and arrangements that direct light away from a
glare angle and inhibit corrosion of a reflective or transflective
metal layer in a display. The invention has been found to be
particularly advantageous in application environments where a
transflective display is needed, that is, a display that is capable
of being illuminated by an ambient light source or by a light
source within the display. While the present invention is not so
limited, an appreciation of the various aspects of the invention is
best gained through a discussion of the various application
examples operating in such an environment,
[0028] FIG. 1 illustrates a cross-section of one particular
embodiment of a display 10 of the present invention including a
lens or touch screen 14. The lens or touch screen 14 may receive
input from the user of the display, or may contribute specific
optical qualities to the display. The display further includes a
light modulating layer 20, made up of a top polarizer 22, a liquid
crystal layer 24, and a bottom polarizer 26. Further, a light
directing film 28 is attached to the bottom polarizer 26. The light
directing film of the present invention may also be incorporated
into a display device that includes only one polarizer, although it
will more commonly be used in a device having two polarizers that
sandwich the liquid crystal layer. The light directing film 28 is
provided to steer the image toward a desired viewing angle, which
is substantially different than a glare angle of the display 10.
The structure of the light directing film 28 is discussed in detail
below. The light directing film 28 may also be referred to as a
beam steering film or tilted mirror film.
[0029] In FIG. 1, an ambient light source 30 is illustrated,
producing incoming ambient light rays 32. In this illustration, a
light ray 32 from source 30 is incident on the display apparatus at
angle a from the normal. The normal is the direction perpendicular
to the display surface. A portion of the incoming light will be
reflected as glare, illustrated by glare ray 34, by the top surface
of the display apparatus 10. The glare ray 34 has a glare angle, b,
from the normal. The glare image will be visible over a range of
viewing angles, but will have a peak brightness at glare angle b.
Angle a is equal to angle b, according to the law of reflection.
Another portion of the incoming light will pass through the light
modulating layer 20 and be reflected by the light directing film
28, as the display information or image, represented by image ray
38. The light directing film 28 is designed to direct the image ray
38 so that it will emerge from the display 10 at an angle from the
normal that is substantially different than the glare angle b. The
display image will also be visible over a range of viewing angles,
and will have a peak brightness at a narrower range of viewing
angles, centered around an "optimal viewing angle." In FIG. 1, the
peak image angle or optimal viewing angle is nearly normal to the
display, as represented by image ray 38. As a result, a viewer of
the display apparatus 10 at position 44 can view the display image
clearly without interference from the glare image.
[0030] FIG. 2 illustrates an alternate display device 200 of the
present invention, wherein components that are similar to the
embodiment of FIG. 1 have identical reference numbers. Display
device 200 includes a light cavity 50, for providing light to the
light modulating layer 24 and illuminating the display apparatus
200. The light cavity 50 includes a light source 52 and a reflector
54. The light cavity 50 may be configured in many different
arrangements, to direct light 60 toward the light modulating layer
20. For example, the light cavity 50 may be an edge-illuminated
light guide, an electroluminescent panel, or one of many other
light cavity arrangements that are known in the art.
[0031] FIG. 3 shows a more detailed view of the cross section of
one embodiment of a titled mirror film or light directing film 300,
before it is incorporated into a display device. The light
directing film includes a silicone liner 310, a pressure sensitive
adhesive 314, an optional polymer protective layer 316, an optional
inorganic protective layer 318, and a metal layer 320. The metal
layer 320 provides a reflective surface for reflecting the ambient
light toward the light modulating layer to produce a display image.
The silicone liner 310 may be provided on the light directing film
300 to cover the adhesive 314. The silicone liner 310 is removed
before the pressure sensitive adhesive 314 is attached to the
bottom polarizer 26.
[0032] The metal layer 320 is formed on a prismatic structure 322,
that is adjacent to a polymer substrate 324. Throughout the text,
the words "formed on" or "formed over" will be used to refer to a
layer that is formed on top of, but not necessarily directly
adjacent to, another layer. Accordingly, the metal layer may not be
directly adjacent to the prismatic structure. Intervening layers
could be present.
[0033] A protective liner 326 may be adjacent to the polymer
substrate 324, on the side opposite from the metal layer 320, if
needed, to protect the polymer substrate during shipping or after
incorporation into the display apparatus. The prismatic structure
322 includes two sides, where one side 328 includes saw tooth
formations 329 having tilted surfaces 330. A second side 332 of the
prismatic structure 322 is preferably substantially smooth or
planar.
[0034] The prismatic structure 322 is configured to direct the
display image ray 38 to emerge from the display apparatus at an
angle substantially different from the glare ray 34, which has an
angle b from the normal. In order to accomplish the redirection of
the image, the prismatic layer 322 includes tilted surfaces 330.
The tilted surfaces are configured so that the peak, or greatest
brightness, of the display image occurs at an angle that is
different than the peak viewing angle of the glare image.
[0035] It is helpful to consider the orientation of a typical
viewer of an LCD. For many LCD's in hand-held devices, the typical
viewer will orient the display at about 30.degree. from horizontal.
The viewer's eyes will be at about 10.degree. from the normal. The
ambient light source is assumed to be directly overhead. Therefore
the ambient light is incident on the display at an angle a, which
is said to be -30.degree. from the display normal. The glare image
will then have a peak at about 30.degree. from the display normal.
The light directing film of the present invention functions to
direct the display image to an optimal viewing angle, or peak
brightness angle, that is substantially different from the glare
angle. In the preceding example, the optimal viewing angle would be
substantially different from 30.degree. away from the normal. Of
course, the display will function to redirect the peak brightness
angle to be different than the glare angle in situations where the
incidence angle is not -30.degree. from normal. There will be a
functional relationship between the light incidence angle and the
peak brightness angle.
[0036] In order to accomplish the redirection of the optimal
viewing angle, the tilted surfaces 330 have a tilt angle t of about
1.degree. to 35.degree. from horizontal in one embodiment.
Preferably, the tilted surfaces have a tilt angle of about
3.degree. to 12.degree. from horizontal. Most preferably, the tilt
angle t will be about 6-9.degree. from the horizontal. These
preferred tilt angles are determined based on the typical viewer
scenario mentioned above, and are also dependent on the qualities
of a particular LCD.
[0037] In many applications, it is desirable for the repeat
distance of the saw tooth formations 329, to be small enough so
that the saw tooth formations are not perceptible to the human eye
at the typical viewing distance. The repeat distance may also be
defined as the horizontal distance between saw tooth formations.
However, the saw tooth formations should be large enough to be
capable of being reliably formed. The smaller the formation, the
more difficult the production procedures for manufacturing the
prismatic layer. In a hand-held LCD with a typical viewing distance
of about 40 to 60 cm, the repeat distance in one embodiment ranges
from about 5 microns or more to about 200 microns or less. More
preferably, the repeat distance may range from 30 microns to about
80 microns. Most preferably, the saw tooth formations have a repeat
distance of about 50 microns. However, where the display is much
larger and viewed from a greater distance, such as for a billboard
or roadside sign, the repeat distance may be substantially
larger.
[0038] The prismatic structure may include a cured resin, an
embossable, thermoplastic material, or another material capable of
forming the saw tooth formations and having the desired optical
properties. Preferably, the prismatic structure is formed of a
cured resin, such as a cross-linked epoxy-acrylate. Preferably, the
prismatic structure 322 provides smooth surfaces for metal
deposition, and has excellent adhesion to both the polymer
substrate 324 and to the metal layer 320. The prismatic structure
is preferably pinhole free. The composition of the prismatic
structure 322 is preferably highly transmissive of visible light,
scratch resistant, and has low outgassing. Preferably, the resin
retains the saw tooth form without shrinkage when cured and when
exposed to heat and humidity. Further, preferably the material of
the prismatic structure is non-halogenated, more preferably
non-brominated because halogen agents, especially bromine, may
cause corrosion of the metal layer.
[0039] One example of a cross-linked epoxy acrylate that is
preferred for use in the prismatic structure is a UV curable
composition including the following components, which are listed
with a range of percentage weight: bisphenol-A epoxy diacrylate
(55-80%), methyl styrene (5-25%), acrylated epoxy (1-10%), a
photoinitiator (0.25-5%) (such as Lucirin TPO), and
fluorosurfactant (0.1-0.3%). Further, the composition may or may
not include a second photoinitiator, such as Irgacure 184, at a
percentage weight up to 5%. The lack of a significant amount of a
halogen agent heavier than flourine is an advantage because of the
corrosive effect of some halogen agents on some metals,
particularly on silver. Although the fluorosurfactant is a halogen,
it is relatively inert, present in only small quantities, and at
least partially evaporates when the metal layer is formed on the
prismatic layer. The presence of the methyl styrene may contribute
to the favorable adhesion characteristics with the polymer
substrate and with the metal layer. This composition provides the
advantages mentioned above, and also changes the mechanical
properties of the metal surface, making it less brittle. This
composition is more completely described in a co-pending U.S.
patent application titled "Compositions and Structures Made
Therefrom", having Attorney Docket No. 7780.514US01, filed on the
same date as the present application.
[0040] The saw tooth formations 329 can be formed in the prismatic
structure 322 by many different methods known in the art, such as
applying the resin structure between a substrate and a tool having
saw tooth formations and polymerizing the composition under UV
radiation, then separating the sheet from the tool. Other formation
methods are also known and may be utilized in the present
invention. Assuming that the apex angle is 90.degree., the
thickness of the prismatic structure from a peak to a valley can be
determined based on the repeat distance (r) and tilt angle (t),
where:
Thickness=(r/2)sin(2t)
[0041] For example, a prismatic structure with a 6-7.degree. tilt
angle and a 50 micron repeat distance, may have a peak to valley
thickness in the range of 5-7 microns. Positioned as a base to the
triangle portions of the saw tooth formations, the prismatic
structure may include a "land portion" that is a flat layer
component underneath the triangle portions. The prismatic structure
322 of the embodiment of FIG. 3 has a land portion below the dashed
line within the prismatic layer 322. The embodiments of FIGS. 10-11
also include a land portion 1018 or 1118 of the prismatic structure
1012 or 1112, below the dashed line. The land portion of the
prismatic structure may be in the range of 0 to 3 microns, and may
depend on the process used to form the prismatic structure.
Preferably, the land portion of the prismatic structure has a
thickness of about 0.5 microns.
[0042] The metal layer 320 is formed on the saw tooth formations
328 of the prismatic structure 322. The metal layer 320 is
preferably highly reflective, and partially transmissive. The
transmissivity of the metallic layer 320 makes it possible to use a
light cavity 50 in the display apparatus, as illustrated in FIG. 2.
The metal layer may be composed of many different materials capable
of forming reflective layers including, one or more of: silver,
chromium, nickel, aluminum, titanium, aluminum-titanium alloy,
gold, zirconium, platinum, palladium, aluminum-chromium alloy or
rhodium. The metal layer may be formed on the prismatic substrate
using many different methods that are known in the art, including
vacuum deposition or plating. Suitable vacuum deposition techniques
include sputtering, evaporation and cathodic arc deposition.
Plating techniques such as electroplating or solution plating could
also be used. The metal layer 320 may have a thickness greater than
or equal to about 25 angstroms and less than or equal to about 3000
angstroms. Preferably, the metal layer has a relatively uniform
thickness.
[0043] Preferably, the metal layer is partially transmissive,
allowing light from an internal light cavity to illuminate the
display. The most preferred materials for a partially transmissive
metallic layer are silver and aluminum, because of their reflective
and transmissive qualities as thin layers. Silver is most preferred
for its low light absorption, meaning that the sum of the
reflectivity and the transmissivity of silver is high compared to
other materials. In the preferred embodiment, the metal layer is a
silver layer of about 400 angstroms. However, two factors limit the
performance of silver in a transflective liquid crystal display
apparatus. Silver is vulnerable to attack by airborne pollutants
and solid borne ions, reactive monomers and solvents. Airborne
pollutants that may attack silver include compounds from tail pipe
emissions and the components of acid rain, especially those
including sulfur. In addition, silver is more transmissive than
aluminum in the blue visible light range. While aluminum appears
neutral in color, silver has a yellowish cast. In addition to
silver, other metals are also vulnerable to corrosion and other
types of damage and have color characteristics that favor a
particular color.
[0044] To address these issues, one embodiment of the present
invention includes an inorganic protective layer 318 formed on the
metal layer, where the inorganic protective layer inhibits
molecular transfer to the metal layer. In addition, the inorganic
protective layer 318 preferably balances the color of the light
that is reflected and transmitted by the metal layer 320. Preferred
materials for the inorganic protective layer include indium tin
oxide (ITO), zinc sulfide (ZnS), tin oxide, indium oxide and
titanium oxide. Where these materials are used, in combination with
a silver layer, where a colorless reflectance and transmission
spectra is desired, the inorganic protective layer may have a
thickness greater than or equal to about 300 angstroms and less
than or equal to about 1000 angstroms. These types of inorganic
protective layer do provide protection for the metal layer at
thinner layers, but the color correction properties may also be
considered when determining the thickness of the inorganic
protective layer. Silver metal reflectivity is higher at the red
end of the visible spectrum than the blue end. Use of ITO, ZnS, or
other dielectric materials on the silver will shift the relative
reflectivity as a function of wavelength so that the reflected
light is redder, bluer or more neutral, depending on the dielectric
thickness, than is seen with the native silver reflectivity. This
color shifting first occurs in the thickness range of 300 angstroms
to 1000 angstroms, and repeats at higher order thickness'. For each
type of metal layer and each type of inorganic protective layer,
any color correction requirements are preferably be considered when
determining the thickness of the inorganic protective layer.
[0045] Other possible materials for the inorganic protective layer
include titanium and its oxides, where the layer would have a
thickness greater than or equal to about 10 angstroms and less than
or equal to about 3000 angstroms. In addition, the inorganic
protective layer 318 may be selected from the group consisting of
silicon dioxide, silicon monoxide, and magnesium fluoride, with a
thickness of greater than or equal to about 300 angstroms and less
than or equal to about 1500 angstroms. Other metals and alloys,
their oxides and suboxides can be used where the material is
deposited from the metallic source and is oxidized by subsequent
exposure, such as titanium.
[0046] ITO demonstrates the most favorable properties for use as
the inorganic protective layer on a silver metal layer. Zinc
sulfide and titanium are also preferred materials for use as the
inorganic protective layer in some devices.
[0047] It may be desirable in some displays to include a tie layer
or nucleation layer on one or both sides adjacent to the metal
layer, to improve film formation. Some examples of commonly used
tie layers include titanium, chromium, zirconium, nickel iron
chromium or other alloys. However, in the preferred embodiment of
the invention where silver is used as the metal layer and ITO or
ZnS is used as the inorganic protective layer, the use of a tie
layer did not substantially improve the performance of the light
directing film.
[0048] FIG. 5 shows the reflection change during weathering of a
silver layer coated with ITO. Accelerated environmental tests were
carried out for ITO/Ag films with a constant Ag thickness of 33 nm
and varied ITO thicknesses of 8 nm, 15 nm, and 38 nm. The ITO/Ag
films were coated with a pressure sensitive adhesive with diffusing
properties and were then laminated to glass. The samples were then
placed in an environment with a temperature of 65.degree. C. and
95% relative humidity, and the reflectance of the samples were
measured at regular intervals. Most ITO/Ag films were found to be
quite protective.
[0049] FIG. 6 shows the reflection change of a silver and ZnS layer
during accelerated environmental tests. To produce the data found
in FIG. 6, a silver coating with a constant thickness of 33 nm was
combined with varied ZnS thicknesses of 33 nm, 43 nm, and 83 nm.
The Ag/ZnS films were coated with a pressure sensitive adhesive
with diffusing properties and were then laminated to glass. The
samples were then placed in an environment with a temperature of
65.degree. C. and 95% relative humidity. The thickest ZnS films
offered protection. However, the performance of the ZnS films was
not as good as the protection provided by the ITO films.
[0050] FIG. 7 shows the transmission spectra for an ITO/Ag coating
on a light directing film with a fixed silver thickness of 50 nm
and varied ITO thicknesses of approximately 30 nm, 40 nm, 55 nm,
and 75 nm. A variation of the ITO thickness changes the transmitted
color of the full construction. FIG. 8 shows the reflection spectra
for an ITO/Ag coating on a light directing film with the same
qualities as the film used for FIG. 7. Again, a variation of the
ITO thickness changed the reflected color of the full construction.
For FIGS. 7 and 8, the transmission spectra was measured without
the adhesive layer.
[0051] Now referring to FIG. 3, the pressure sensitive adhesive 314
is preferably an optically diffuse layer. In one embodiment of the
invention, the pressure sensitive adhesive layer includes an
acrylate acrylic acid adhesive. The adhesive 314 may include
optical diffuser particles, dispersed throughout the adhesive layer
to improve the diffusive properties of the adhesive layer.
[0052] The adhesive layer may inhibit corrosion and other damage of
the metal layer, by providing a deterrent to the migration of
molecules between the bottom polarizer 26 and the metal layer 320.
The polarizer may contain halogens and other reactants, that may
migrate to the metal layer 320, causing corrosion and other damage.
For example, iodine may migrate to the metal layer from the
polarizer causing corrosion. However, in the preferred embodiment,
the adhesive deters the migration of molecules including iodine to
the metallic layer, thereby extending the lifetime of the metallic
layer 320.
[0053] The pressure sensitive adhesive may be of the type butyl
acrylate/acrylic acid, having a ratio between 90/10 and 97/3,
iso-octyl acrylate acrylic acid having a ratio between 90/10 and
97/3, or iso-octyl acrylate/acrylic acid/isobornyl
acrylate/Regalrez 6108 having a ratio of approximately
66.3/0.67/13.4/19.3. The adhesive may be used in combination with
one or more of bisamide cross-linker, benzoyl peroxide initiator,
an aziridine cross-linker, a chlorinated cross-linker such as
XL-330, Irgacure 651 cross-linker, or other standard acrylic
adhesive cross-linkers. In addition, the adhesive may contain one
or more of the following additives: benzotriazole, 5-amino
benzotriazole, 5-butyl benzotriazole, benzotriazole 5-carboxylic
acid, octadecyl thiol, or thiosilanes. One example of a pressure
sensitive adhesive that may be used with the present invention is
described in PCT WO 99/21913, which is hereby incorporated by
reference. The diffusive quality of the pressure sensitive adhesive
layer may be adjusted by modifying the concentration of diffusing
particles suspended within the adhesive, depending on the specific
level of diffusion that is desired.
[0054] In one embodiment of the present invention, the light
directing film 300 includes a polymer barrier layer or polymer
protective layer 316, formed on the inorganic protective layer 318.
The polymer protective layer 316 inhibits molecular transfer to the
metal layer 320 in this embodiment. The polymer protective layer
may or may not be used in combination with the inorganic protective
layer. The polymer protective layer or polymer layer 316 is
selected from a group consisting of cross-linked epoxy resin,
cross-linked or linear acrylic resin, epoxy acrylate, polyester
such as Vitel.RTM., polyethylene, polyvinylidene chloride, and
polyvinyl alcohol. One example of a cross-linked acrylic resin that
may be used has the tradename B48N, produced by Rohm and Haas, 100
Independence Mall West, Philadelphia, Pa. 19106-2399.
[0055] If the polymer protective layer is used in combination with
the inorganic protective layer, then the polymer protective layer
316 will typically be deposited on the inorganic protective layer,
as illustrated in FIG. 3. Where the polymer protective layer is
used in a light directing film without the inorganic protective
layer, then the polymer protective layer is typically deposited
directly onto the metal layer. The construction of such an
arrangement would be similar to the construction of FIG. 3, if the
inorganic protective layer 318 were eliminated.
[0056] The polymer protective layer may be formed using a variety
of methods known in the art. For example, the polymer protective
layer is preferably solution coated, in which case the thickness of
the polymer protective layer 316 may range from about 0.01 micron
to about 50 microns. The polymer protective layer may be
conformally deposited on the metal layer or inorganic protective
layer, or may planarize or partially planarize the underlying saw
tooth formations.
[0057] Where the polymer protective layer 316 has a planarizing
function, one side of the layer has tilted surfaces corresponding
to the tilted surfaces of the prismatic structure, and a second
side of the layer 316 is substantially planar. It is possible that
the polymer protective layer 316 may include more than one layer.
For example, if the polymer protective layer is intended to
planarize the underlying prismatic structure, it may include more
than one layer. Also, depending on the material that is used, more
than one layer may be desirable to ensure that the polymer
protective layer functions as a proper barrier.
[0058] One possible method for forming the polymer protective layer
316 is vapor depositing volatile monomeric or oligomeric polymer
precursors, then curing the precursors. The deposition may take
place at normal atmospheric pressure or under vacuum. Curing may be
accomplished using either thermal, ultraviolet, or electron beam
radiation, or plasma or corona exposure. One example of such a
method for conformal deposition and some examples of specific
materials are described in co-pending applications U.S. Ser. Nos.
09/259,100, titled "Retroreflective Articles Having Polymer
Multilayer Reflective Coatings" and U.S. Ser. No. 09/259,487,
titled "Method of Coating Microstructured Substrates with Polymeric
Layer(s), Allowing Preservation of Surface Feature Profile", which
are both incorporated by reference herein. Using the method
described in these two above-referenced co-pending patent
applications, a typical polymer protective layer would have a
thickness of about 1 nm to about 2 micron. In some embodiments,
this method may be preferred to solution coating the polymer
protective layer, because the solvent used in solution coating may
be detrimental to the metal layer or other layers of the display
apparatus. The polymer protective layer could also be deposited
using plasma processes such as plasma polymerization or
plasma-enhanced chemical vapor deposition, as is known in the
art.
[0059] One preferred material for the polymer protective layer is
solution-coated polymethyl methacrylate (PMMA) with a thickness of
about 10 microns. The PMMA may include additives such as UV
blockers and tarnish-inhibiting agents. One preferred additive to
the PMMA is glycol dimercaptoacetate (GDA), a corrosion inhibitor
for silver. This and other additives that may be used with the
polymer protective layer are discussed in U.S. Pat. Nos. 4,307,150
and 4,645,714, which are hereby incorporated by reference herein.
Alternatively, the polymer protective layer could include the
UV-curable cross-linked epoxy acrylate described above as the
preferred material for the prismatic structure.
[0060] Several of the embodiments of the present invention include
a polymer substrate. The polymer substrate may be a material
selected from the group consisting of PET, polyether sulphone
(PES), polycarbonate, cellulose diacetate, and cellulose
triacetate, and may be birefringent or non-birefringent.
Preferably, the polymer substrate has a thickness of about 25 to
1000 microns.
[0061] FIG. 9 illustrates the advantage of including a light
directing film in a display apparatus. FIG. 9 plots the reflected
light profile, showing reflected luminescence measured in foot
lamberts (fL) versus viewing angle, for four different LCD's. The
four LCD's are identical except that a different transflector is
used. The incident light was collimated and directed at -30 degrees
to the normal.
[0062] In the TMF example, a light directing film of one embodiment
of the present invention was utilized. The TMF was attached to the
bottom polarizer of a light modulating layer, similar to the device
illustrated in FIG. 1. Specifically, the TMF film included a
polymer substrate, a polymer prismatic layer, a silver layer and a
polymer protective layer of PMMA. The TMF was adhered to the back
polarizer of the LCD.
[0063] The Holographic film is a reflective film formed by the
action of interfering laser beams on a photoactive medium. It
reflects light at a designed angle different from the glare
direction, but has a hue of a single color, usually green. One
example of this type of film is Imagix.RTM. film manufactured by
Polaroid Corporation. The Standard transflector is a composite
material formed from an adhesive matrix and a reflective
particulate adhered to a clear substrate, for example using the
trade name NPF-EG4225P3, manufactured by Nitto Denko. The TDF film
is a 3M product comprising a diffusing adhesive coated on one side
of a reflective polarizer substrate and a neutral density film
coated on the back side of the substrate. TDF replaces the bottom
polarizer of a reflective display, while the Holographic film and
the Standard transflector adhere to the back surface of a dichroic
bottom display polarizer.
[0064] In FIG. 9, the glare peak for the display is at about
28-36.degree.. The standard, Holographic and TDF samples have
brightness peaks during ambient mode performance near this glare
peak. The TMF sample of the present invention has a brightness peak
substantially different than this glare peak, however, at about
12.degree.. The incident light was at -30.degree. from normal
incidence during the testing.
[0065] According to the present invention, the light directing film
of FIG. 2 may be constructed in many different ways, and still
accomplish the redirection of the image angle away from the glare
angle, protect the metal film from corrosion and other damage, and
balance color of the reflected and transmitted light. Four
different construction examples are shown in FIGS. 10-13. For
example, in FIG. 10, a light directing film 1000 is illustrated
including a polymer film substrate 1010, a cured prismatic polymer
layer 1012, a metal layer 1014, and an adhesive layer 1016. The
prismatic layer 1012 includes a land portion 1018, as previously
discussed, below the dashed line through the prismatic structure.
The adhesive layer 1016 planarizes, or back-fills the saw tooth
formations of the prismatic layer 1012. The adhesive layer 1016 may
or may not contain the optical diffuser particles that are
illustrated in this embodiment. The light directing film 1000
attaches to the bottom polarizer of a reflective LCD using adhesive
layer 1016. The light directing film 1000 will also include at
least one additional layer adjacent to the metal layer 1014,
according to the invention, such as an inorganic protective layer,
a polymer protective layer, or both, that are not illustrated in
FIG. 10.
[0066] FIG. 11 shows a cross-section of a light directing film
1100, including a polymer film substrate 1110, a cured prismatic
polymer layer 1112, a metal layer 1114, and a cured polymer layer
1116. The prismatic layer 1112 includes a land portion 1118, as
previously discussed, below the dashed line through the prismatic
structure. The cured polymer layer 1116 may planarize or back-fill
the saw tooth formations, and may or may not contain optical
diffuser particles. The light directing film 1100 may be positioned
in a display apparatus with the cured polymer layer 1116 adjacent
to the bottom polarizer of a reflective LCD and may be bonded with
an adhesive native to the polarizer. Therefore, in this embodiment,
the pressure sensitive adhesive is resident within the polarizer.
The light directing film 1100 will also include at least one
additional layer adjacent to the metal layer 1114, according to the
invention, such as an inorganic protective layer, a polymer
protective layer, or both, that are not illustrated in FIG. 11.
[0067] FIG. 12 illustrates another embodiment of a light directing
film 1200 of the present invention. The light directing film
includes a cured polymer layer 1210, a cured prismatic polymer
layer 1214, which may or may not contain optical diffuser
particles, a metal layer 1212, and a polymer film substrate 1216.
In the embodiment of FIG. 12, the optical diffuser particles are
present within the prismatic layer 1214, rather than in the
adhesive layer. The optical diffuser particles might also be
included in other layers of the construction, such as the polymer
protective layer, that are between the metal layer and the ambient
light source. The metal layer 1212 is formed on the cured prismatic
polymer layer 1214, and the cured polymer layer 1210 back-fills the
prisms. The light directing film 1200 is positioned with the
substrate 1216 adjacent to the bottom polarizer of a reflective LCD
and may be bonded with an adhesive native to the polarizer.
Therefore, in this embodiment, the pressure sensitive adhesive is
included within the polarizer. The light directing film 1200 will
also include at least one additional layer adjacent to the metal
layer 1212, according to the invention, such as an inorganic
protective layer, a polymer protective layer, or both, that are not
illustrated in FIG. 12.
[0068] FIG. 13 shows a light directing film 1300 including a
polymer film substrate 1310, which may or may not contain optical
diffuser particles, a metal layer 1312 formed on the polymer film
substrate 1310, and a cured polymer layer 1314, which back-fills
the saw tooth formations. In this embodiment, the diffusing
characteristic is provided by the polymer film substrate 1310
rather than by the adhesive layer. The light directing film 1300 is
positioned with the polymer film substrate 1310 adjacent to the
bottom polarizer of a reflective LCD and may be bonded with an
adhesive native to the polarizer. Therefore, in this embodiment,
the pressure sensitive adhesive is included within the polarizer.
As in FIGS. 10-12, the embodiment of FIG. 13 will also include at
least one additional layer adjacent to the metal layer 1312,
according to the invention, such as an inorganic protective layer,
a polymer protective layer, or both, that are not illustrated in
FIG. 13.
[0069] This invention provides a reflective or transflective
optical film multilayer construction that can serve as a component
of an information display device, such as an LCD in a cellular
telephone. Back reflectors and transflectors, and other light
control elements in such devices are subjected to high heat and/or
humidity conditions in field use and in product qualification.
Previously, similar constructions using thin metal films as the
reflective/transflective layer failed under these conditions by
losing reflectivity or optical density.
[0070] The variants of the light directing film listed below have
been tested and can survive harsh environmental conditions. The
following compositions showed only negligible degradation of
transmissivity and reflectivity after being subjected to 65.degree.
C. at 95% relative humidity for at least 240 hours. The
reflectivity, averaged over the visible spectrum suffered less than
3% degradation during the environmental tests. These compositions
were attached to a polarizer during testing.
EXAMPLES
[0071] 1. A construction of:
[0072] a) a polymer substrate of 5 mil polyester;
[0073] b) a prismatic structure of bromine-free epoxy acrylate
resin;
[0074] c) a metal layer of about 200 angstroms aluminum;
[0075] d) an inorganic protective layer of about 50 angstroms
titanium; and
[0076] e) a pressure sensitive adhesive layer of butyl
acrylate/acrylic acid (ratio about 90/10); survived 400 hours of
65.degree. C. at 95% relative humidity with negligible degradation
(less than 3%) of the transmissivity and reflectivity of the
construction in the visible wavelengths.
[0077] 2. A construction of:
[0078] a) a polymer substrate of 5 mil polyester;
[0079] b) a prismatic structure of bromine-free epoxy acrylate
resin;
[0080] c) a metal layer of about 400 angstroms silver;
[0081] d) an inorganic protective layer of about 500 angstroms zinc
sulfide; and
[0082] e) a pressure sensitive adhesive layer of butyl
acrylate/acrylic acid (ratio about 90/10); survived 480 hours of
65.degree. C. at 95% relative humidity with negligible degradation
(less than 3%) of the transmissivity and reflectivity of the
construction in the visible wavelengths.
[0083] 3. A construction of:
[0084] a) a polymer substrate of 5 mil polyester;
[0085] b) a prismatic structure of bromine-free epoxy acrylate
resin;
[0086] c) a metal layer of about 400 angstroms silver;
[0087] d) a polymer protective layer of PMMA; and
[0088] e) a pressure sensitive adhesive layer of butyl
acrylate/acrylic acid (ratio about 90/10); survived over 240 hours
of 65.degree. C. at 95% relative humidity with negligible
degradation (less than 3%) of the reflectivity and transmissivity
of the construction in the visible wavelengths.
[0089] As noted above, the present invention is applicable to a
number of different LCD's including reflective layers. Accordingly,
the present invention should not be considered limited to the
particular examples described above, but rather should be
understood to cover all aspects of the invention as set out in the
attached claims. Various modifications, equivalent processes, as
well as numerous structures to which the present invention may be
applicable will be readily apparent to those of skill in the art
upon review of the present specification. The claims are intended
to cover such modifications and devices.
* * * * *