U.S. patent application number 09/945744 was filed with the patent office on 2002-05-23 for antiglare film, method for producing the same, polarizer and liquid crystal display.
Invention is credited to Matsunaga, Naohiro, Nakamura, Kazuhiro.
Application Number | 20020060849 09/945744 |
Document ID | / |
Family ID | 26600538 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020060849 |
Kind Code |
A1 |
Matsunaga, Naohiro ; et
al. |
May 23, 2002 |
Antiglare film, method for producing the same, polarizer and liquid
crystal display
Abstract
An antiglare film is described, which comprises a triacetyl
cellulose transparent support having provided thereon one or more
hard coat layers including an antiglare hard coat layer, wherein
the hard coat layer contiguous to the triacetyl cellulose
transparent support is formed from a coating solution comprising
solvents comprising one or more solvents which dissolve the
triacetyl cellulose support and one or more solvents which do not
dissolve the triacetyl cellulose support. A method for producing
the antiglare film, a polarizer wherein the antiglare film is used
and a liquid crystal display wherein the antiglare film or the
polarizer is used are also described.
Inventors: |
Matsunaga, Naohiro;
(Kanagawa, JP) ; Nakamura, Kazuhiro; (Kanagawa,
JP) |
Correspondence
Address: |
Platon N. Mandros
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
26600538 |
Appl. No.: |
09/945744 |
Filed: |
September 5, 2001 |
Current U.S.
Class: |
359/614 ;
359/586; 359/601 |
Current CPC
Class: |
G02B 1/11 20130101; G02B
27/0018 20130101; G02F 1/133502 20130101 |
Class at
Publication: |
359/614 ;
359/601; 359/586 |
International
Class: |
G02B 001/10; G02B
027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2000 |
JP |
PAT.2000-288785 |
Nov 15, 2000 |
JP |
PAT.2000-348308 |
Claims
What is claimed is:
1. An antiglare film comprising a triacetyl cellulose transparent
support having provided thereon one or more hard coat layers
including an antiglare hard coat layer, wherein the hard coat layer
contiguous to said triacetyl cellulose transparent support is
formed from a coating solution comprising solvents comprising one
or more solvents which dissolve said triacetyl cellulose support
and one or more solvents which do not dissolve said triacetyl
cellulose support.
2. The antiglare film as claimed in claim 1, wherein at least one
of the solvents which do not dissolve the triacetyl cellulose
support has higher boiling point than the boiling point of at least
one of the solvents which dissolve the triacetyl cellulose
support.
3. The antiglare film as claimed in claim 2, wherein the
temperature difference of the boiling point between the solvent
having the highest boiling point of the solvents which do not
dissolve the triacetyl cellulose support and the solvent having the
highest boiling point of the solvents which dissolve the triacetyl
cellulose support is 30.degree. C. or more.
4. The antiglare film as claimed in claim 1, wherein the antiglare
hard coat layer is formed by crosslinking by ionizing
radiation.
5. The antiglare film as claimed in claim 1, wherein a
penta-functional or more functional acrylate monomer which is
crosslinked by ionizing radiation is at least used as the component
for forming the antiglare hard coat layer.
6. The antiglare film as claimed in claim 1, wherein said triacetyl
cellulose transparent support is a triacetyl cellulose film formed
by casting a triacetyl cellulose dope prepared by dissolving a
triacetyl cellulose in a solvent not substantially containing a
dichloromethane by means of a single layer-casting process.
7. The antiglare film as claimed in claim 1, wherein said triacetyl
cellulose transparent support is a triacetyl cellulose film formed
by casting a triacetyl cellulose dope prepared by dissolving a
triacetyl cellulose in a solvent by means of a multilayer-casting
process.
8. The antiglare film as claimed in claim 1, wherein particles
having an average particle size of from 1.0 to 5.0 .mu.m are
dispersed in the antiglare hard coat layer.
9. The antiglare film as claimed in claim 1, wherein said antiglare
hard coat layer has a refractive index of from 1.50 to 2.00.
10. The antiglare film as claimed in claim 1, wherein a low
refractive index layer having a refractive index of from 1.35 to
1.45 is provided as an antireflection layer as an outermost layer
on the side of the support on which at least one hard coat layer is
provided, and the haze value of the antiglare film is 3.0% or
more.
11. A method for producing an antiglare film comprising a triacetyl
cellulose transparent support having provided thereon one or more
hard coat layers including an antiglare hard coat layer, wherein
the hard coat layer contiguous to said triacetyl cellulose
transparent support is formed from a coating solution comprising
solvents comprising one or more solvents which dissolve said
triacetyl cellulose support and one or more solvents which do not
dissolve said triacetyl cellulose support.
12. The method for producing an antiglare film as claimed in claim
11, wherein at least one of the solvents which do not dissolve the
triacetyl cellulose support has higher boiling point than the
boiling point of at least one of the solvents which dissolve the
triacetyl cellulose support.
13. The method for producing an antiglare film as claimed in claim
12, wherein the temperature difference of the boiling point between
the solvent having the highest boiling point of the solvents which
do not dissolve the triacetyl cellulose support and the solvent
having the highest boiling point of the solvents which dissolve the
triacetyl cellulose support is 30.degree. C. or more.
14. The method for producing an antiglare film as claimed in claim
11, wherein the antiglare hard coat layer is formed by crosslinking
by ionizing radiation.
15. The method for producing an antiglare film as claimed in claim
11, wherein a penta-functional or more functional acrylate monomer
which is crosslinked by ionizing radiation is at least used as the
component for forming the antiglare hard coat layer.
16. The method for producing an antiglare film as claimed in claim
11, wherein said triacetyl cellulose transparent support is a
triacetyl cellulose film formed by casting a triacetyl cellulose
dope prepared by dissolving a triacetyl cellulose in a solvent not
substantially containing a dichloromethane by means of a single
layer-casting process.
17. The method for producing an antiglare film as claimed in claim
11, wherein said triacetyl cellulose transparent support is a
triacetyl cellulose film formed by casting a triacetyl cellulose
dope prepared by dissolving a triacetyl cellulose in a solvent by
means of a multilayer-casting process.
18. The method for producing an antiglare film as claimed in claim
11, wherein particles having an average particle size of from 1.0
to 5.0 .mu.m are dispersed in the antiglare hard coat layer.
19. The method for producing an antiglare film as claimed in claim
11, wherein said antiglare hard coat layer has a refractive index
of from 1.50 to 2.00.
20. A polarizer, wherein the antiglare film as claimed in claim 1
is used as at least one of two protective films of a polarizing
layer.
21. A polarizer, wherein the antiglare film as claimed in claim 1
is used as one of two protective films of a polarizing layer and an
optical compensating film having optical anisotropy is used as the
other protective film.
22. A liquid crystal display, wherein the antiglare film as claimed
in claim 1 or the polarizer as claimed in claim 20 is used as the
outermost layer of the display.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an antiglare film, a method
for producing the same, a polarizer and a liquid crystal display
using the same.
BACKGROUND OF THE INVENTION
[0002] In image displays such as CRT, PDP and LCD, an antiglare
film or an antiglare antireflection film is generally arranged at
outermost surface of a display for the purpose of preventing the
reduction of contrast due to the reflection of an outer light and
the reflection of an image.
[0003] The particles of an inorganic or organic polymer are used in
a coating solution for forming the antiglare hard coat layer of an
antiglare film or an antiglare antireflection film for giving an
antiglare property. When a solvent which swells and dissolves a
triacetyl cellulose support is used as a solvent composition in a
coating solution for the antiglare hard coat layer for obtaining
adhesion of the triacetyl cellulose support and the antiglare hard
coat layer, the particles for giving antiglare property are
partially buried in the support, thus a sufficient antiglare
property cannot be obtained. While when a coating solution for the
antiglare hard coat layer is prepared with a solvent which does not
dissolve a triacetyl cellulose support, sufficient adhesion cannot
be obtained, although antiglare property can be obtained, so that
there arises a problem in either case.
SUMMARY OF THE INVENTION
[0004] An object of the present invention is to provide an
antiglare film having sufficient antiglare property compatible with
sufficient adhesion of a support and an antiglare hard coat layer
by merely forming an antiglare hard coat layer on a triacetyl
cellulose transparent support, further to provide an antiglare film
having an antireflection ability by providing a low refractive
index layer.
[0005] Another object of the present invention is to provide a
polarizer and a liquid crystal display using the above film.
[0006] The above objects of the present invention have been
achieved by an antiglare film, a polarizer and a liquid crystal
display each having the constitution described below.
[0007] 1. An antiglare film comprising a triacetyl cellulose
transparent support having provided thereon one or more hard coat
layers including an antiglare hard coat layer, wherein the hard
coat layer contiguous to the triacetyl cellulose transparent
support is formed from a coating solution comprising solvents
comprising one or more solvents which dissolve the triacetyl
cellulose support and one or more solvents which do not dissolve
the triacetyl cellulose support.
[0008] 2. The antiglare film as described in the above item 1,
wherein at least one of the solvents which do not dissolve the
triacetyl cellulose support has higher boiling point than the
boiling point of at least one of the solvents which dissolve the
triacetyl cellulose support.
[0009] 3. The antiglare film as described in the above item 2,
wherein the temperature difference of the boiling point between the
solvent having the highest boiling point of the solvents which do
not dissolve the triacetyl cellulose support and the solvent having
the highest boiling point of the solvents which dissolve the
triacetyl cellulose support is 30.degree. C. or more.
[0010] 4. The antiglare film as described in the above item 1, 2 or
3, wherein the antiglare hard coat layer is formed by crosslinking
by ionizing radiation.
[0011] 5. The antiglare film as described in the above item 1, 2, 3
or 4, wherein a penta-functional or more functional acrylate
monomer which is crosslinked by ionizing radiation is at least used
as the component for forming the antiglare hard coat layer.
[0012] 6. The antiglare film as described in any of the above items
1 to 5, wherein the triacetyl cellulose transparent support is a
triacetyl cellulose film formed by casting a triacetyl cellulose
dope prepared by dissolving a triacetyl cellulose in a solvent not
substantially containing a dichloromethane by means of a single
layer-casting process.
[0013] 7. The antiglare film as described in any of the above items
1 to 5, wherein the triacetyl cellulose transparent support is a
triacetyl cellulose film formed by casting a triacetyl cellulose
dope prepared by dissolving a triacetyl cellulose in a solvent by
means of a multilayer-casting process.
[0014] 8. The antiglare film as described in any of the above items
1 to 7, wherein particles having an average particle size of from
1.0 to 5.0 .mu.m are dispersed in the antiglare hard coat
layer.
[0015] 9. The antiglare film as described in the above item 8,
wherein the particles dispersed in the antiglare hard coat layer
are spherical organic polymer particles.
[0016] 10. The antiglare film as described in any of the above
items 1 to 9, wherein the antiglare hard coat layer has a
refractive index of from 1.50 to 2.00.
[0017] 11. The antiglare film as described in any of the above
items 1 to 10, wherein the antiglare hard coat layer comprises a
cured product of the composition containing a monomer having two or
more ethylenic unsaturated groups and the particles of the oxide of
at least one kind of a metal selected from the group consisting of
titanium, aluminum, indium, zinc, tin, antimony and zirconium
having particle size of 0.1 .mu.m or less.
[0018] 12. The antiglare film as described in any of the above
items 1 to 11, wherein a low refractive index layer having a
refractive index of from 1.35 to 1.45 is provided as an
antireflection layer as an outermost layer on the side of the
support on which at least one hard coat layer is provided, and the
haze value of the antiglare film is 3.0% or more.
[0019] 13. The antiglare film as described in the above item 12,
wherein the low refractive index layer comprises a cured product of
the composition comprising a fluorine-containing compound which is
crosslinked by heat or ionizing radiation and inorganic fine
particles, and the integrating sphere average reflectance of from
450 to 650 nm of the antiglare film is 2.3% or less.
[0020] 14. The antiglare film as described in the above item 13,
wherein the inorganic fine particles have an average particle size
of from 0.001 to 0.1 .mu.m.
[0021] 15. The antiglare film as described in the above item 13 or
14, wherein the inorganic fine particles are silica.
[0022] 16. The antiglare film as described in the above item 13, 14
or 15, wherein the fluorine-containing compound is a polymer
obtained by polymerizing a fluorine-containing vinyl monomer.
[0023] 17. The antiglare film as described in any of the above
items 1 to 16, wherein the triacetyl cellulose transparent support
is a triacetyl cellulose formed by multilayer-casting of a
triacetyl cellulose.
[0024] 18. A method for producing an antiglare film comprising a
triacetyl cellulose transparent support having provided thereon one
or more hard coat layers including an antiglare hard coat layer,
wherein the hard coat layer contiguous to said triacetyl cellulose
transparent support is formed from a coating solution comprising
solvents comprising one or more solvents which dissolve said
triacetyl cellulose support and one or more solvents which do not
dissolve said triacetyl cellulose support.
[0025] 19. The method for producing an antiglare film as described
in the above item 18, wherein at least one of the solvents which do
not dissolve the triacetyl cellulose support has higher boiling
point than the boiling point of at least one of the solvents which
dissolve the triacetyl cellulose support.
[0026] 20. The method for producing an antiglare film as described
in the above item 19, wherein the temperature difference of the
boiling point between the solvent having the highest boiling point
of the solvents which do not dissolve the triacetyl cellulose
support and the solvent having the highest boiling point of the
solvents which dissolve the triacetyl cellulose support is
30.degree. C. or more.
[0027] 21. The method for producing an antiglare film as described
in the above item 18, 19 or 20, wherein the antiglare hard coat
layer is formed by crosslinking by ionizing radiation.
[0028] 22. The method for producing an antiglare film as described
in the above item 18, 19, 20 or 21, wherein a penta-functional or
more functional acrylate monomer which is crosslinked by ionizing
radiation is at least used as the component for forming the
antiglare hard coat layer.
[0029] 23. The method for producing an antiglare film as described
in any of the above items 18 to 22, wherein said triacetyl
cellulose transparent support is a triacetyl cellulose film formed
by casting a triacetyl cellulose dope prepared by dissolving a
triacetyl cellulose in a solvent not substantially containing a
dichloromethane by means of a single layer-casting process.
[0030] 24. The method for producing an antiglare film as described
in any of the above items 18 to 22, wherein said triacetyl
cellulose transparent support is a triacetyl cellulose film formed
by casting a triacetyl cellulose dope prepared by dissolving a
triacetyl cellulose in a solvent by means of a multilayer-casting
process.
[0031] 25. The method for producing an antiglare film as described
in any of the above items 18 to 24, wherein particles having an
average particle size of from 1.0 to 5.0 .mu.m are dispersed in the
antiglare hard coat layer.
[0032] 26. The method for producing an antiglare film as described
in any of the above items 18 to 25, wherein said antiglare hard
coat layer has a refractive index of from 1.50 to 2.00.
[0033] 27. A polarizer, wherein the antiglare film as described in
any of the above items 1 to 17 is used as at least one of two
protective films of a polarizing layer.
[0034] 28. A polarizer, wherein the antiglare film as described in
any of the above items 1 to 17 is used as one of two protective
films of a polarizing layer and an optical compensating film having
optical anisotropy is used as the other protective film.
[0035] 29. A liquid crystal display, wherein the antiglare film as
described in any of the above items 1 to 17 or the polarizer as
described in the above item 27 or 28 is used as the outermost layer
of the display.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a schematic cross-sectional view showing the layer
constitution of an antiglare antireflection film.
Key to the Symbols
[0037] 1: Antiglare film
[0038] 2: Transparent support
[0039] 3: Antiglare hard coat layer
[0040] 4: Low refractive index layer
[0041] 5: Mat particles
DETAILED DESCRIPTION OF THE INVENTION
[0042] The antiglare film of the present invention comprises a
triacetyl cellulose transparent support having provided thereon one
or more hard coat layers including an antiglare hard coat layer,
and a low refractive index layer is further provided when
antireflection function is required of the antiglare film.
[0043] The fundamental constitution of the antiglare film of the
present invention is described below with reference to the
accompanying drawing.
[0044] The embodiment shown in FIG. 1 is an example of an antiglare
film of the present invention. Antiglare film 1 has the layer
constitution in order of transparent support 2 comprising a
triacetyl cellulose, antiglare hard coat layer 3, and low
refractive index layer 4. Mat particles 5 are dispersed in
antiglare hard coat layer 3. Antiglare hard coat layer 3 may
comprises a plurality of layers. Further, a hard coat layer not
having an antiglare property (not shown in the figure) may be
coated for giving film strength, although it is not always
necessary.
[0045] "Hard coat layer" used in the present invention includes
both an antiglare hard coat layer and a hard coat layer not having
an antiglare property.
[0046] The refractive index of the above antiglare hard coat layer
is preferably from 1.50 to 2.00, and the refractive index of the
low refractive index layer is preferably from 1.35 to 1.45. The
refractive index of the triacetyl cellulose used as the transparent
support is 1.48.
[0047] The antiglare film of the present invention preferably has a
haze value of 3% or more (more preferably from 3 to 15%). An
antiglare property and a haze value do not necessarily correspond
linearly, but if a haze value is smaller than 3%, an antiglare film
having sufficient antiglare property cannot be obtained. On the
other hand, if a haze value is excessively large, light scattering
on the surface or in the inside of the film is strong, as a result,
problems such as the reduction of clarity and whitening of images
arise, thus not advantageous.
[0048] Each layer constituting the antiglare film of the present
invention is described below.
Support
[0049] A transparent support for use in the antiglare
antireflection film according to the present invention is a
triacetyl cellulose support (having a refractive index of 1.48),
more preferably a triacetyl cellulose support comprising a
plurality of layers.
[0050] When the antiglare film of the present invention is used in
a liquid crystal display, the antiglare film is arranged at the
outermost surface of a liquid crystal display by the way of
providing an adhesive layer on one side, etc. Since a triacetyl
cellulose is used as a protective film for protecting the
polarizing layer of a polarizer, the antiglare film of the present
invention using a triacetyl cellulose as a support can be used as a
protective film as it is, and very advantageous economically.
[0051] As the transparent support of the antiglare film of the
present invention, it is preferred to use a triacetyl cellulose
film formed by any of a single layer-casting process or a
multilayer-casting process of co-casting a triacetyl cellulose dope
having been prepared by dissolving a triacetyl cellulose in a
solvent. In particular, from the viewpoint of environmental
protection, a triacetyl cellulose film formed using a triacetyl
cellulose dope prepared by dissolving a triacetyl cellulose in a
solvent not substantially containing a dichloromethane by a low
temperature dissolution method or a high temperature dissolution
method is preferably used.
[0052] A single layer triacetyl cellulose film is formed by a
drum-casting process or a band-casting process as disclosed in
JP-A-7-11055 (the term "JP-A" as used herein means an "unexamined
published Japanese patent application") and a multilayer triacetyl
cellulose film comprising a plurality of layers is formed by a
co-casting process as disclosed in JP-A-61-94725 and JP-B-62-43846
(the term "JP-B" as used herein means an "examined Japanese patent
publication"). That is, raw material flakes are dissolved with a
solvent, and to the solution are added various additives, e.g., a
plasticizer, an ultraviolet absorber, a degradation preventing
agent, a sliding agent, and a peeling accelerator, as required, and
then the solution (this is called a dope) is cast on a support
consisting of a horizontal endless metal belt or a rotating drum by
a dope supplying means. At this time, if the casting is single
layer-casting, a single dope is cast as a single layer, and when
the casting is multilayer casting, a dope in low concentration is
cast on both sides of a cellulose ester dope in high concentration
by co-casting, the cast solution is dried on the support to a
certain degree, the film given stiffness is peeled from the
support, and then the film is passed through a drying zone by
various transporting means to remove the solvent.
[0053] Triacetyl cellulose films produced by a co-casting process
are characterized in that they are excellent in film surface
smoothness and productivity, since a dope in low concentration is
cast on both sides of a cellulose ester dope in high concentration
by co-casting. By using such supports, streaky coating unevenness
attributable to the plane failure of a support caused at the time
of wet coating of an antiglare layer of the antiglare
antireflection film according to the present invention can be
remarkably improved, thus an antiglare antireflection film in which
excellent transmission image clarity is compatible with uniform
plane properties at wet coating can be obtained.
[0054] Further, notwithstanding a triacetyl cellulose film produced
by a co-casting process comprises a plurality of layers, a clear
interface is not present between each layer and the layers form a
continuous layer with each other, thus optical loss due to
reflection and the like at interface does not occur.
[0055] Further, a triacetyl cellulose film produced by a co-casting
process is improved especially in surface unevenness in the
transverse direction, hence the improving effect of coating
unevenness in the transverse direction is great when the upper
layer is formed by wet coating. Evaluation of such smoothness in
the transverse direction can be performed about the surface
unevenness of each pitch constituent in a wide measuring range
(from several centimeters to about 10 cm) by measuring surface
displacement with a laser displacement gauge. As a result of
similar evaluation of triacetyl cellulose films prepared in various
methods, it has become clear that the failure in surface
properties, in particular, streaky failure which occurs in the
machine direction when an antiglare hard coat layer and a low
refractive index layer are provided, is related with the height of
the surface unevenness of from 3 to 10 mm pitch.
[0056] A support having a low height of the surface unevenness of
from 3 to 10 mm pitch can be obtained by the above-described
methods, and an antiglare antireflection film which hardly causes
fault of surface properties such as streaky failure can be obtained
by forming an antiglare layer and a low refractive index layer in
order.
[0057] As the solvent for dissolving the triacetyl cellulose as
described above, a dichloromethane is representative. A hydrocarbon
halide such as a dichloromethane can be used with no problem
technically, however, from the viewpoint of the global
environmental protection and work environment, it is preferred that
the solvent does not substantially contain a hydrocarbon halide
such as dichloromethane. The terminology "does not substantially
contain" means that the ratio of a hydrocarbon halide contained in
the organic solvent is less than 5 wt % (preferably less than 2 wt
%). In particular, it is preferred that a dichloromethane is not
substantially contained in the solvent in the case of a single
layer-casting process. In the case of a co-casting process, even if
a dope using the solvent substantially containing a dichloromethane
is cast by a multilayer co-casting process, since a dope containing
a triacetyl cellulose in higher concentration as compared with the
outer cast layers can be used as the inner cast layer, as a result,
the amount of a dichloromethane released to the air can be reduced.
In the present invention, it is preferred not to contain a
hydrocarbon halide such as a dichloromethane even in the case of a
co-casting process. Further, it is possible to increase a casting
speed of a co-casting process, thus a co-casting process is
excellent in productivity too.
[0058] When a triacetyl cellulose dope is prepared by using a
solvent not substantially containing a dichloromethane or the like,
the peculiar dissolution methods described below are essential.
[0059] A first dissolution method which is called a cooling
dissolution method is described below. In the first place, a
triacetyl cellulose is gradually added to a solvent with stirring
at a temperature around room temperature (from -10 to 40.degree.
C.). In the next place, the mixed product is cooled to from -100 to
-10.degree. C. (preferably from -80 to -10.degree. C., more
preferably from -50 to -20.degree. C., and most preferably from -50
to -30.degree. C.). Refrigeration can be performed in a dry
ice.methanol bath (-75.degree. C.) or a refrigerated diethylene
glycol solution (from -30 to -20.degree. C.). The mixed product of
a triacetyl cellulose and a solvent is solidified by refrigeration.
Further, when this solid product is heated to from 0 to 200.degree.
C. (preferably from 0 to 150.degree. C., more preferably from 0 to
120.degree. C., and most preferably from 0 to 50.degree. C.), the
solid product comes to a solution wherein triacetyl cellulose is
flowing in the solvent. The temperature increase may be performed
by merely allowing the solid product to stand in room temperature
or the solid product may be heated in a hot bath.
[0060] A second dissolution method which is called a high
temperature dissolution method is described below. In the first
place, a triacetyl cellulose is gradually added to a solvent with
stirring at a temperature around room temperature (from -10 to
40.degree. C.). It is preferred that the triacetyl cellulose
solution according to the present invention comprises a mixed
solvent containing various solvents and a triacetyl cellulose added
thereto and swelled in advance. The concentration of the triacetyl
cellulose solution in this method is preferably 30 wt % or less,
but in view of the drying efficiency at film-forming time, the
concentration of the triacetyl cellulose solution is preferably as
high as possible. In the next place, the mixed solution of organic
solvents is heated at from 70 to 240.degree. C. (preferably from 80
to 220.degree. C., more preferably from 100 to 200.degree. C., and
most preferably from 100 to 190.degree. C.) under pressure of from
0.2 to 30 PMa. Since the heated solution cannot be coated as it is,
it is necessary that the solution should be cooled to not higher
than the lowest boiling point of the solvents used. In such a case,
the solution is generally cooled to -10 to 50.degree. C. and then
returned to normal pressure. A high pressure and high temperature
container or line in which the triacetyl cellulose solution is
contained may be merely allowed to stand at room temperature to
effect refrigeration, or more preferably the container and line may
be refrigerated with a cooling medium such as cooling water.
[0061] When the antiglare film of the present invention is used in
a liquid crystal display, the antiglare film is arranged at the
outermost surface of the liquid crystal display by the way of
providing an adhesive layer on one side of the film, etc. Since a
triacetyl cellulose film is used as a protective film for
protecting the polarizing layer of a polarizer in a liquid crystal
display, the antiglare film of the present invention can be used as
a protective film as it is, therefore very preferred.
[0062] For using the antiglare film of the present invention as the
protective film of a polarizing layer, it is necessary that the
protective film is subjected to saponification treatment from the
viewpoint of adhesive property. Since the antiglare film of the
present invention is resistant to saponification, the film can
undergo saponification treatment just before being stuck on the
protective film. Saponification treatment may be performed directly
to the triacetyl cellulose film or may be performed after an
antiglare hard coat layer has been formed, but it is preferably
performed after the layer has been entirely formed from the point
of productivity.
Antiglare Hard Coat Layer
[0063] An antiglare hard coat layer is a layer for giving an
antiglare property to the antiglare film of the present invention,
and mat particles are dispersed in a high refractive index
material.
[0064] The refractive index of an antiglare hard coat layer is
preferably from 1.50 to 2.00, more preferably from 1.57 to 1.90,
and still more preferably from 1.64 to 1.80. The refractive index
of the antiglare hard coat layer is a value measured in the state
not containing mat particles.
[0065] An antireflection property lowers when a refractive index is
too small, while when it is too large, the tint of the reflected
light of the antiglare film of the present invention becomes
strong, which is not preferred.
[0066] Further, since light scattering attributable to surface
unevenness due to mat particles dispersed in a high refractive
index material is caused in the antiglare hard coat layer, the
influence of optical interference is not caused in the antiglare
layer. In a hard coat layer having high refractive index not
containing mat particles, an amplitude large in reflectance is seen
in the wavelength dependency of reflectance by the optical
interference due to the difference in the refractive index between
a hard coat layer and a support, as a result, the effect of
preventing reflection is deteriorated and, at the same time, color
unevenness comes to occur. However, in the antiglare film of the
present invention, these problems are solved by the scattering
effect by the surface unevenness of the antiglare layer.
[0067] The binder for use in the antiglare hard coat layer is
preferably a polymer having a saturated hydrocarbon or a polyether
as the main chain, and a polymer having a saturated hydrocarbon as
the main chain is more preferred. Further, a binder is preferably
crosslinked. It is preferred to obtain a polymer having a saturated
hydrocarbon as the main chain by the polymerization reaction of an
ethylenic unsaturated monomer. For obtaining a crosslinked binder,
it is preferred to use a monomer having two or more ethylenic
unsaturated groups.
[0068] The examples of the monomers having two or more ethylenic
unsaturated groups include esters of polyhydric alcohol and
(meth)acrylic acid (e.g., ethylene glycol di(meth)acrylate,
1,4-cyclohexane diacrylate, pentaerythritol tetra(meth)acrylate,
pentaerythritol tri(meth) acrylate, trimethylolpropane
tri(meth)acrylate, trimethylolethane tri(meth)acrylate,
dipentaerythritol tetra(meth)acrylate, dipentaerythritol
penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
1,3,5-cyclohexanetriol trimethacrylate, polyurethane polyacrylate,
and polyester polyacrylate), vinylbenzene derivatives (e.g.,
1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloyl ethyl ester, and
1,4-divinylcyclohexanone), vinyl sulfone (e.g., divinyl sulfone),
acrylamide (e.g., methylenebisacrylamide) and methacrylamide. Of
these monomers, penta-functional or more acrylates are preferred
from the viewpoint of film hardness, i.e., scratch resistance. The
mixtures of dipentaerythritol pentaacrylate and dipentaerythritol
hexaacrylate are commercially available and particularly preferably
used.
[0069] These monomers having an ethylenic unsaturated group are
dissolved in a solvent with various kinds of polymerization
initiators and other additives, coated and dried, and then cured by
ionizing radiation or thermal polymerization reaction.
[0070] In place of or in addition to the monomers having two or
more ethylenic unsaturated groups, crosslinking structure may be
introduced into a binder by the reaction of a crosslinkable group.
The examples of crosslinkable functional groups include an
isocyanate group, an epoxy group, an aziridine group, an oxazoline
group, an aldehyde group, a carbonyl group, a hydrazine group, a
carboxyl group, a methylol group and an active methylene group.
Vinylsulfonic acid, acid anhydride, cyanoacrylate derivative,
melamine, etherified methylol, ester and urethane, and metal
alkoxide such as tetramethoxysilane can be used as the monomers for
introducing crosslinking structure. Functional groups which show a
crosslinking property as a result of decomposition reaction, e.g.,
a blocked isocyanate group, may also be used, i.e., crosslinking
functional groups which show reactivity as a result of
decomposition may be used in the present invention even if they do
not show reactivity in a moment.
[0071] The binders having these crosslinkable functional groups can
form crosslinking structure by heating after coating.
[0072] In addition to the above binder polymers, the binder of the
antiglare hard coat layer is formed from the polymers obtained by
the copolymerization of the above binder polymer and a monomer
having a high refractive index and/or metal oxide ultra fine
particles having a high refractive index, etc.
[0073] The examples of monomers having a high refractive index
include bis (4-methacryloylthiophenyl) sulfide, vinylnaphthalene,
vinylphenyl sulfide, 4-methacryloxyphenyl-4'-methoxyphenyl
thioether, etc.
[0074] It is preferred for the metal oxide ultra fine particles
having a high refractive index to contain fine particles having a
particle size of 100 nm or less, preferably 50 nm or less,
comprising at least one oxide of metal selected from the group
consisting of zirconium, titanium, aluminum, indium, zinc, tin and
antimony. As the examples of the fine particles, ZrO.sub.2,
TiO.sub.2, Al.sub.2O.sub.3, In.sub.2O.sub.3, ZnO, SnO.sub.2,
Sb.sub.2O.sub.3 and ITO, and ZrO.sub.2 is especially preferred of
these.
[0075] The addition amount of the metal oxide ultra fine particles
is preferably from 10 to 90 wt %, more preferably from 20 to 80 wt
%, of the entire weight of the antiglare hard coat layer.
[0076] For the purpose of imparting an antiglare property and
preventing the deterioration of reflectance due to the interference
by the hard coat layer and a support, and for preventing irregular
color, inorganic or organic polymer particles are dispersed in the
antiglare hard coat layer as the mat particles. The shape of the
mat particles is not especially restricted but a perfect spherical
shape is preferred for giving a uniform antiglare property.
Further, from the viewpoint of the dispersion stability of the
particles in a coating solution, organic polymer particles are more
preferred. The average particle size of the mat particles is
preferably from 1.0 to 5.0 .mu.m, more preferably from 1.5 to 4.0
.mu.m, and still more preferably from 2.0 to 3.0 .mu.m, in number
average particle size by a Coulter method. If the average particle
size is less than 1.0 .mu.m, an antiglare property is insufficient
and if it exceeds 5.0 .mu.m, transmission image clarity is
deteriorated.
[0077] As the mat particles for use in the antiglare hard coat
layer, amorphous silica particles, crosslinked PMMA series
particles, crosslinked polystyrene series particles, and
crosslinked benzoguanamine series particles are preferably used
from the viewpoint of an average particle size, a refractive index,
and easiness of dispersion. Of these, spherical organic polymer
particles are particularly preferred.
[0078] When the antiglare hard coat layer is in contact with the
support, the solvents for the coating solution for forming the
antiglare hard coat layer comprise one or more solvents which
dissolve the triacetyl cellulose support and one or more solvents
which do not dissolve the triacetyl cellulose support for
contriving to reconcile the exhibition of antiglare property and
the adhesion of the support to the antiglare layer. More
preferably, at least one of the solvents which do not dissolve the
triacetyl cellulose support has higher boiling point than the
boiling point of at least one of the solvents which dissolve the
triacetyl cellulose support. Still more preferably, the temperature
difference of the boiling point between the solvent having the
highest boiling point of the solvents which do not dissolve the
triacetyl cellulose support and the solvent having the highest
boiling point of the solvents which dissolve the triacetyl
cellulose support is 30.degree. C. or more, and most preferably,
the temperature difference is 50.degree. C. or more.
[0079] As the solvents which dissolve a triacetyl cellulose, the
following solvents can be exemplified:
[0080] Ethers having from 3 to 12 carbon atoms, specifically,
dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane,
propylene oxide, 1,4-dioxane, 1,3-dioxolan, 1,3,5-trioxane,
tetrahydrofuran, anisole, phenetole, etc.;
[0081] Ketones having from 3 to 12 carbon atoms, specifically,
acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone,
diisobutyl ketone, cyclopentanone, cyclohexanone, methyl
cyclohexanone, etc.;
[0082] Esters having from 3 to 12 carbon atoms, specifically, ethyl
formate, propyl formate, n-pentyl formate, methyl acetate, ethyl
acetate, methyl propionate, ethyl propionate, n-pentyl acetate,
.gamma.-butyrolactone, etc.;
[0083] Organic solvents having two or more functional groups,
specifically, 2-methoxymethyl acetate, 2-ethoxymethyl acetate,
2-ethoxyethyl acetate, 2-ethoxyethyl propionate, 2-methoxyethanol,
2-propoxyethanol, 2-butoxyethanol, 1,2-diacetoxyacetone,
acetylacetone, diacetone alcohol, methyl acetoacetate, ethyl
acetoacetate, etc.
[0084] These solvents can be used alone or in combination of two or
more.
[0085] As the solvents which do not dissolve triacetyl cellulose,
methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol,
tert-butanol, 1-pentanol, 2-methyl-2-butanol, cyclohexanol,
isobutyl acetate, methyl isobutyl ketone, 2-octanone, 2-pentanone,
2-hexanone, 2-heptanone, 3-pentanone, 3-heptanone, 4-heptanone can
be exemplified.
[0086] These solvents can be used alone or in combination of two or
more.
[0087] The weight ratio of the total amount of the solvents which
dissolve triacetyl cellulose (A) to the total amount of the
solvents which do not dissolve triacetyl cellulose (B) (A/B) is
preferably from 5/95 to 50/50, more preferably from 10/90 to 40/60,
and still more preferably from 15/85 to 30/70.
Hard Coat Layer Not Having Antiglare Property
[0088] In the antiglare film of the present invention, a hard coat
layer not having an antiglare property may be coated between the
transparent support and the antiglare layer, if necessary, for the
purpose of improving film strength, but this layer is not an
requisite layer.
[0089] The refractive index of the hard coat layer not having an
antiglare property is preferably from 1.50 to 1.60.
[0090] The same components as the binder constituting the antiglare
hard coat layer can be used in the hard coat layer not having an
antiglare property except that mat particles are not dispersed
therein, and the refractive index can be made to fall within the
above range by the adjustment of the components.
[0091] When the hard coat layer not having an antiglare property is
in contact with the support, the same meaning as to the solvents as
described in the antiglare hard coat layer is applied as it is to
the solvents for the coating solution for forming the hard coat
layer not having an antiglare property.
Low Refractive Index Layer
[0092] A low refractive index layer is provided as the
antireflection layer as the outermost layer on the side of the
support on which the hard coat layer is provided for the purpose of
giving an antireflection ability to the antiglare film of the
present invention.
[0093] The refractive index of the low refractive index layer is
preferably from 1.35 to 1.45.
[0094] It is preferred that the refractive index of the low
refractive index layer should satisfy the following equation
(I):
(m.lambda./4).times.0.7<n.sub.1d.sub.1<(m.lambda./4).times.1.3
(I)
[0095] wherein m represents a positive odd number (generally 1)
n.sub.1 represents the refractive index of the low refractive index
layer, and d.sub.1 represents the film thickness of the low
refractive index layer (nm). .lambda. represents the wavelength of
a visible ray, and is the value in the range of from 450 to 650
nm.
[0096] Satisfying the above equation (I) means that m (a positive
odd number, generally 1) which satisfies equation (I) in the above
wavelength range is present.
[0097] A cured fluorine-containing resin of a heat curing type or
ionizing radiation curing type crosslinkable fluorine-containing
compound is used in the low refractive index layer. The coefficient
of dynamic friction of a cured fluorine-containing resin is
preferably from 0.03 to 0.15, and the contact angle to water is
preferably from 90 to 120.degree..
[0098] As the crosslinkable fluorine-containing compound, silane
compounds containing a perfluoroalkyl group, e.g.,
(heptadecafluoro-1,1,2,2-tetrade- cyl)triethoxysilane, and
fluorine-containing copolymers containing a fluorine-containing
monomer and a monomer for providing a crosslinking property as
constitutional units can be exemplified.
[0099] The specific examples of the fluorine-containing monomers
include, e.g., fluoroolefins (e.g., fluoroethylene, vinylidene
fluoride, tetrafluoroethylene, hexafluoroethylene,
hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole, etc.),
partially or completely fluorinated alkyl ester derivatives of
(meth)acrylic acid (e.g., Biscote 6FM (manufactured by Osaka Yuki
Kagaku Co., Ltd.), M-2020 (manufactured by Daikin Kogyo Co.,
Ltd.)), and completely or partially fluorinated vinyl ethers,
etc.
[0100] As the monomers for providing a crosslinking property,
(meth)acrylate monomers having a crosslinkable functional group in
advance in the molecule, e.g., glycidyl methacrylate,
(meth)acrylate monomers having a carboxyl group, a hydroxyl group,
an amino group or a sulfonic acid group (e.g., (meth)acrylic acid,
methylol (meth)acrylate, hydroxyalkyl (meth)acrylate, allyl
acrylate, etc.) can be exemplified. In the latter case,
crosslinking structure can be introduced after copolymerization as
disclosed in JP-A-10-25388 and JP-A-10-147739.
[0101] Not only the above-described copolymers of a
fluorine-containing monomer and a monomer for providing a
crosslinking property but the polymers of these monomers
copolymerized with other monomers may be used in the low refractive
index layer.
[0102] Other monomers which may be copolymerized are not
particularly restricted and, e.g., olefins (e.g., ethylene,
propylene, isoprene, vinyl chloride, vinylidene chloride), acrylic
esters (e.g., methyl acrylate, ethyl acrylate, 2-ethylhexyl
acrylate), methacrylic esters (e.g., methyl methacrylate, ethyl
methacrylate, butyl methacrylate, ethylene glycol dimethacrylate),
styrene derivatives (e.g., styrene, divinylbenzene, vinyltoluene,
.alpha.-methylstyrene), vinyl ethers (e.g., methyl vinyl ether),
vinyl esters (e.g., vinyl acetate, vinyl propionate, vinyl
cinnamate), acrylamides (e.g., N-tert-butylacrylamide,
N-cyclohexylacrylamide), methacrylamides and acrylonitrile
derivatives can be exemplified.
[0103] For giving a scratch resisting property, it is preferred
that the ultra fine particles of an Si oxide having an average
particle size of preferably 0.1 .mu.m or less, more preferably from
0.001 to 0.05 .mu.m, be added to the fluorine-containing resins for
use in the low refractive index layer. In view of the prevention of
reflection, the refractive index is preferably the lower, but as
the refractive index of the fluorine-containing resin is lowered,
the scratch resistance is deteriorated. Accordingly, the best
balanced point of scratch resistance and low refractive index can
be found by optimizing the refractive index of the
fluorine-containing resin and the addition amount of the ultra fine
particles of an Si oxide. As the ultra fine particles of an Si
oxide, silica sols dispersed in commercially available organic
solvents may be added to the coating solution as they are or
various kinds of commercially available silica powders may be used
by being dispersed in organic solvents.
Formation of Each Layer
[0104] Each layer of the antiglare film can be formed by coating
according to various coating method, e.g., a dip coating method, an
air knife coating method, a curtain coating method, a roller
coating method, a wire bar coating method, a gravure coating method
and an extrusion coating method (disclosed in U.S. Pat. No.
2,681,294). Two or more layers may be coated at the same time.
Simultaneous coating methods are disclosed, e.g., in U.S. Pat. Nos.
2,761,791, 2,941,898, 3,508,947, 3,526,528 and Yuji Harazaki,
Coating Kogaku (Coating Engineering), p. 253, Asakura Shoten Co.
(1973).
Application to Liquid Crystal Display and Polarizer
[0105] The antiglare film of the present invention can be applied
to image displays, e.g., a liquid crystal display (LCD), a plasma
display panel (PDP), an electroluminescence display (ELD) and a
cathode ray tube (CRT). The antiglare film of the present invention
is used by adhering the transparent support side of the film to the
image displaying face of an image display, but when the antiglare
film is used on the surface or in the inside of LCD, it is more
preferred to use the film as it is as the film of one side of the
two protective films for protecting the polarizing layer of a
polarizer. It is still more preferred to use an optical
compensating film having optical anisotropy on the other side in
view of capable of providing the effect of widening the angle of
visibility.
[0106] In the antiglare film of the present invention, a sufficient
antiglare property is compatible with sufficient adhesion of a
support and an antiglare hard coat layer by merely forming an
antiglare hard coat layer on a triacetyl cellulose transparent
support. Further, a film comprising the antiglare film of the
present invention provided with a low refractive index layer as the
antireflection layer is possessed of not only an antiglare property
but an antireflection ability.
[0107] Further, a polarizer and a liquid crystal display using the
above film comprising the antiglare film of the present invention
provided with a low refractive index layer as the antireflection
layer are free of the reflection of an outer light, therefore
excellent contrast can be obtained. The polarizer and the liquid
crystal display are excellent in visibility and image clarity,
because reflected images are inconspicuous due to the antiglare
property.
[0108] The present invention is more specifically described below
with referring to examples, but it should not be construed as the
present invention is limited thereto.
EXAMPLE 1
Preparation of Triacetyl Cellulose Dope A
[0109] Starting materials comprising 17.4 weight parts of triacetyl
cellulose, 2.6 weight parts of triphenyl phosphate, 66 weight parts
of dichloromethane, 5.8 weight parts of methanol, and 8.2 weight
parts of n-butanol were mixed with stirring and dissolved to
prepare triacetyl cellulose dope A.
Preparation of Triacetyl Cellulose Dope B
[0110] Starting materials comprising 24 weight parts of triacetyl
cellulose, 4 weight parts of triphenyl phosphate, 66 weight parts
of dichloromethane, and 6 weight parts of methanol were mixed with
stirring and dissolved to prepare triacetyl cellulose dope B.
Preparation of Triacetyl Cellulose Dope C
[0111] A heterogeneous gel state solution obtained by stirring 20
weight parts of triacetyl cellulose, 48 weight parts of methyl
acetate, 20 weight parts of cyclohexanone, 5 weight parts of
methanol, 5 weight parts of ethanol, 2 weight parts of triphenyl
phosphate/biphenyldiphenyl phosphate (1/2), 0.1 weight part of
silica (a particle size of 20 nm), and 0.2 weight part of
2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-buty-
lanilino)-1,3,5-triazine was cooled at -70.degree. C. for 6 hours,
then heated at 50.degree. C. and stirred to prepare triacetyl
cellulose dope C.
Preparation of Triacetyl Cellulose Dope D
[0112] A heterogeneous gel state solution obtained in the same
manner as in the preparation of triacetyl cellulose dope C was
heated in a stainless steel sealed container at 1 MPa, 180.degree.
C. for 5 minutes, and then the container was put in a water bath at
50.degree. C. to be cooled, thereby triacetyl cellulose dope D was
prepared.
Preparation of Coating Solution for Antiglare Hard Coat Layer
[0113] As the binder constituting the antiglare hard coat layer, a
mixture of dipentaerythritol pentaacrylate and dipentaerythritol
hexaacrylate (DPRA, manufactured by Nippon Kayaku Co., Ltd.) was
used. As the photopolymerization initiator, an appropriate amount
of Irgacure 907 (manufactured by Ciba Fine Chemicals Co., Ltd.) was
added. As the high refractive index material for imparting a high
refractive index to the antiglare hard coat layer, zirconium oxide
fine particles having a particle size of about 30 nm were
dispersion-liquefied by a solvent and added to the coating solution
of the antiglare hard coat layer. Further, as the spherical
particles for imparting an antiglare property, Eposter MS
(crosslinked benzoguanamine particles, average particle size: about
2 .mu.m, the refractive index of the particles: 1.68, manufactured
by Nippon Shokubai Co., Ltd.) was dispersion-liquefied by a solvent
and added to the coating solution of the antiglare hard coat layer.
The concentration of the coating solution of the antiglare hard
coat layer containing the above solid contents was adjusted so that
when the wet coating amount was 5.2 ml/m.sup.2 the refractive index
of the antiglare hard coat layer (the refractive index of the
composite layer of the binder and the zirconium oxide) after being
dried and UV-cured became 1.68, the film thickness 1.4 .mu.m, and
the haze 14% (related with the concentration of the particles). The
solvent composition of the coating solution of the antiglare hard
coat layer at this time was only methyl ethyl ketone (100%). The
coating solution of the antiglare hard coat layer was filtered in
advance before coating through a polypropylene filter (PPE-03)
having a pore diameter of 3 .mu.m.
Preparation of Coating Solution for Low Refractive Index Layer
[0114] To 2,240 g of a thermally crosslinkable fluorine-containing
polymer (JN-7228, manufactured by JSR Co., Ltd., the concentration
of the solid contents: 6 wt %, a methyl ethyl ketone solution)
having a refractive index of 1.42 were added 192 g of MEK-ST (an
average particle size: from 10 to 20 nm, a methyl ethyl ketone
dispersion of an SiO.sub.2 sol having the concentration of the
solid contents of 30 wt %, manufactured by Nissan Chemical
Industries, Ltd.), 2,224 g of a methyl ethyl ketone, and 144 g of
cyclohexanone, stirred, and then the mixture was filtered through a
polypropylene filter (PPE-01) having a pore diameter of 1 .mu.m,
thereby a coating solution for the low refractive index layer was
prepared. When this coating solution is coated on the above
antiglare hard coat layer having haze of 14%, the haze of the
resulting coated layer finally becomes 12%.
Comparative Sample No. 1
[0115] The above coating solution for antiglare hard coat layer was
coated on a triacetyl cellulose film (TAC-TD80U, manufactured by
Fuji Photo Film Co., Ltd.) having a thickness of 80 .mu.m by means
of a bar coater and dried at 120.degree. C., and then the coated
layer was cured with the irradiation of ultraviolet using an air
cooling type metal halide lamp (manufactured by I Graphics Co.,
Ltd.) having a capacity of 160 W/cm at illuminance of 400
mW/cm.sup.2 and the quantity of radiation of 300 mJ/cm.sup.2, thus
an antiglare hard coat layer having a thickness of 1.4 .mu.m was
formed.
[0116] The above coating solution for low refractive index layer
was coated thereon with a bar coater and dried at 80.degree. C.,
and subjected to crosslinking at 120.degree. C. for 8 minutes,
thereby a low refractive index layer having a thickness of 0.096
.mu.m was formed.
Comparative Sample Nos. 2 to 12 and Sample Nos. 1 to 12 of the
Invention
[0117] Comparative Sample Nos. 2 to 12 and Sample Nos. 1 to 12 of
the invention were prepared in the same manner as in the
preparation of Comparative Sample No. 1 except that the final
coating solution solvent composition of the coating solution for
the antiglare hard coat layer was changed as shown in Table 1
below.
Evaluation of Surface Displacement of Transparent Support
[0118] The smoothness of the transparent support prepared by each
casting process was evaluated according to the following
method.
[0119] Each transparent support was cut to a size of 170 mm.times.4
mm vertically to the casting direction, both ends of the support
were fixed by being stuck on an acryl plate. A laser displacement
gauge (KL130A, manufactured by Anritsu Co., Ltd.) was used for
measuring surface displacement and a mask was provided on the laser
ray-receiving part so that only the surface reflection could be
measured on conditions of the measuring range of 135 mm and the
measuring spacing of 100 .mu.m. The surface displacement measured
was taken in as the two dimensional coordinate data. In the next
place, for removing the ingredients of undulation due to the
flexure of the base film, the displacements up and down from the
central line of the two dimensional coordinate data were described
as plus and minus respectively with the central line of the two
dimensional coordinate data as the curve fitted by a septuple
formula, and the surface displacements of the film to respective
positions were graphed. The height of the surface unevenness having
a pitch of from 3 to 10 mm was read from the graph and the ratio of
the height to the pitch was computed.
Evaluation of Antiglare Antireflection Film
[0120] Evaluation of the following each item was performed with the
prepared antiglare antireflection film.
[0121] (1) Haze
[0122] The haze of the obtained film was measured using a haze
meter MODEL 1001DP (manufactured by Nippon Denshoku Kogyo Co.,
Ltd.).
[0123] (2) Evaluation of Transmission Image Clarity
[0124] The value of the transmission image clarity of the prepared
antiglare antireflection film was measured by an optical comb of
0.5 mm width using an image clarity tester model ICM-2D
(manufactured by Suga Shikenki Co., Ltd.). It was found that the
value of the transmission image clarity was an important indicator
for developing an antiglare antireflection film matching a
high-definition LCD monitor. The larger the value, it can be said
that the film corresponds to high precision. The goal was set at
30% or more in the present invention.
[0125] (3) Evaluation of Antiglare Property
[0126] A bare fluorescent lamp with no louver (8,000 cd/cm.sup.2)
was reflected on the antiglare antireflection film prepared, and
the degree of a blur of the reflected image was evaluated by the
following criteria.
[0127] .circleincircle.: The contour of the fluorescent lamp could
not be recognized at all or hardly recognized.
[0128] .largecircle.: The contour of the fluorescent lamp could be
slightly recognized.
[0129] .DELTA.: The fluorescent lamp was blurred but the contour
could be recognized.
[0130] X: The fluorescent lamp was hardly blurred.
[0131] (4) Adhering Property
[0132] On the surface of the antiglare antireflection film, a 25 mm
square portion was notched with a single edged blade to make 25
square portions (one square was 5 mm.times.5 mm), a commercially
available cellophane adhesive tape was applied to the surface of
the film with a load of 1 kg, and the adhesion was evaluated by
whether the film was peeled or not with the cellophane tape when
the cellophane tape was peeled. The test was repeated five times
and the adhesion was evaluated by the following criteria.
[0133] .circleincircle.: The film did not peel off at all.
[0134] .largecircle.: Less than one square peeled off on
average.
[0135] .DELTA.: From one to less than five squares peeled off on
average.
[0136] X :Five or more squares peeled off on average.
[0137] The results of the comparative samples are shown in Table 1
and the results of the samples of the present invention are shown
in Table 2 below.
[0138] As is shown in Table 1, when the solvent composition
constituting the coating solution of the antiglare hard coat layer
comprises only a solvent which does not dissolve the triacetyl
cellulose support, there arises a problem in the adhesion.
[0139] While when the solvent composition comprises only a solvent
which dissolves the triacetyl cellulose support, the particles for
giving antiglare property are buried in the support dissolved,
there arises a problem in that the antiglare property cannot be
obtained.
[0140] On the other hand, as is apparent from the results shown in
Table 2, the adhesion is compatible with the antiglare property
when the solvent composition of the coating solution comprises both
of the solvent dissolving the triacetyl cellulose support and the
solvent not dissolving the triacetyl cellulose support. Further,
when the boiling point of the solvent which does not dissolve the
triacetyl cellulose support is higher than that of the solvent
which dissolves the triacetyl cellulose support, and the larger the
difference of the boiling points, the greater is the effect.
1TABLE 1 Solvent Composition Compar- of Antiglare Solubility
Boiling ative Hard Coat of TAC of Point Antiglare Sample Layer (wt
%) Solvent (.degree. C.) Property Adhesion 1 MEK (100)
.largecircle. 80 .times. .circleincircle. 2 MC (100) .largecircle.
39 .times. .circleincircle. 3 AC (100) .largecircle. 56 .times.
.circleincircle. 4 MA (100) .largecircle. 56 .times.
.circleincircle. 5 DOK (100) .largecircle. 101 .times.
.circleincircle. 6 CH (100) .largecircle. 156 .times.
.circleincircle. 7 DAA (100) .largecircle. 168 .times.
.circleincircle. 8 MT (100) .times. 65 .times. 9 PR (100) .times.
97 .times. 10 MIBK (100) .times. 116 .times. 11 iBA (100) .times.
118 .times. 12 CC (100) .times. 173 .times. In the column of
solubility, .largecircle. means soluble and .times. means
insoluble.
[0141]
2TABLE 2 Solvent Composition Sample of Antiglare Solubility Boiling
of the Hard Coat of TAC of Point Antiglare Invention Layer (wt %)
Solvent (.degree. C.) Property Adhesion 1 CH/MIBK
.largecircle./.times. 156/116 .largecircle. .circleincircle.
(30/70) 2 DAA/MIBK .largecircle./.times. 168/116 .largecircle.
.circleincircle. (30/70) 3 MEK/CH/
.largecircle./.largecircle./.times. 80/156/ .largecircle.
.circleincircle. MIBK 116 (15/15/70) 4 MA/MIBK
.largecircle./.times. 56/116 .circleincircle. .circleincircle.
(30/70) 5 MEK/MIBK .largecircle./.times. 80/116 .circleincircle.
.circleincircle. (30/70) 6 MA/OC .largecircle./.times. 56/173
.circleincircle..degree. .circleincircle. (30/70) 7 MEK/OC
.largecircle./.times. 80/173 .circleincircle..degree.
.circleincircle. (30/70) 8 CH/OC .largecircle./.times. 156/173
.circleincircle. .circleincircle. (30/70) 9 DAA/OC
.largecircle./.times. 168/173 .circleincircle. .circleincircle.
(30/70) 10 MEK/MA/ .largecircle./.largecircle./.DELTA. 80/56/
.circleincircle. .circleincircle. MIBK 116 (15/15/70) 11 MEK/CH/OC
.largecircle./.largecircle./.DELTA. 80/156/ .circleincircle.
.circleincircle. (15/15/70) 173 12 MEK/MA/OC
.largecircle./.largecircle./.DELTA. 80/56/ .circleincircle..degree.
.circleincircle. (15/15/70) 173 In the column of solubility,
.largecircle. means soluble and .times. means insoluble. In the
column of antiglare property, .largecircle..degree. is better than
.circleincircle. by one rank.
[0142] The abbreviations in Tables 1 and 2 are as follows.
3 AC: Acetone iBA: Isobutyl acetate CH: Cyclohexanone DAA:
Diacetone alcohol DOK: 1,4-Dioxane MA: Methyl acetate MC: Methylene
chloride MEK Methyl ethyl ketone MIBK: Methyl isobutyl ketone MT:
Methanol OC: 2-Octanone PR: 1-Propanol
Sample Nos. 13 to 15 of the Invention
[0143] As is shown in Table 3, antiglare antireflection film Sample
Nos. 13, 14 and 15 of the invention were prepared in the same
manner as in the preparation of Sample No. 7 of the present
invention except that only the particle size of the polymer
particles and the thickness of the antiglare hard coat layer were
changed in such a manner that the ratio of the thickness of the
antiglare hard coat layer to the average particle size of particles
giving the antiglare property was kept constant (1.4/2.0=0.7) and
the haze 12% as the antiglare antireflection film was not
changed.
[0144] As is apparent from the results shown in Table 3, all of the
samples of the present invention satisfy the required performances
but the particle sizes of from 2 to 3 .mu.m are preferred in view
of the transmission image clarity and the antiglare property.
4TABLE 3 Thickness of Sample Antiglare Particle of the Layer Size
Antiglare Transmission Invention (.mu.m) (.mu.m) Property Adhesion
Image Clarity 13 0.7 1.0 .circleincircle. .circleincircle. 30 or
more (7) (1.4) (2.0) (.circleincircle..degree.) (.circleincircle.)
(30 or more) 14 2.1 3.0 .circleincircle. .circleincircle. 30 or
more 15 3.5 5.0 .circleincircle. .circleincircle. 10
Sample Nos. 16 to 18 of the Invention
[0145] Antiglare antireflection film Sample Nos. 16, 17 and 18 of
the invention were prepared in the same manner as in the
preparation of Sample No. 7 of the invention except that the
triacetyl cellulose support was replaced with the following
triacetyl cellulose support I, II or III.
[0146] 1. Preparation of Triacetyl Cellulose Support I
[0147] According to JP-A-11-254594, multilayer-casting was
performed by means of a three layer co-casting die with the
arrangement so that dope A was cast on both sides of dope B, and
the dopes were discharged simultaneously on a metal drum, the cast
film was peeled from the drum, and dried, thereby a three layer
co-cast triacetyl cellulose film of 10 .mu.m, 60 .mu.m and 10 .mu.m
from the drum side was formed. Clear interfaces were not formed
between each layer of the film.
[0148] 2. Preparation of Triacetyl Cellulose Support II
[0149] According to JP-A-7-11055, the above-described triacetyl
cellulose dope C was cast by single layer drum casting and
triacetyl cellulose support II having a thickness of 80 .mu.m was
formed.
[0150] 3. Preparation of Triacetyl Cellulose Support III
[0151] According to JP-A-7-11055, the above-described triacetyl
cellulose dope D was cast by single layer drum casting and
triacetyl cellulose support III having a thickness of 80 .mu.m was
formed.
[0152] When the displacement in the transverse direction of the
film surface of each of the above triacetyl cellulose films I, II
and III was measured according to the measuring method using the
later-described laser displacement gauge, none of the samples had
the height of the surface unevenness of from 3 to 10 mm pitch of
{fraction (1/10,000)} or more of the pitch.
[0153] Incidentally, when the displacement in the transverse
direction of the film surface of TAC-TD80U was measured with the
laser displacement gauge, the height of the surface unevenness of
about 3 mm pitch was from 0.3 to 0.4 .mu.m and a little unevenness
was present.
[0154] Since Sample Nos. 16, 17 and 18 were excellent in the
smoothness of the support, the coated state of the antiglare hard
coat layer was still better than that of Sample No. 7 of the
invention, thus an excellent antiglare antireflection film could be
obtained. Other results of the evaluations were the same as those
of Sample No. 7 of the invention.
[0155] In the next place, an antiglare antireflection polarizer was
produced using an antiglare film having provided thereon an
antireflection layer according to the present invention. When a
liquid crystal display was manufactured using the above polarizer,
since the reflection of an outer light was excluded, excellent
contrast was obtained. Visibility and image clarity were excellent,
because reflected images were inconspicuous due to the antiglare
property.
[0156] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope
thereof.
* * * * *