U.S. patent application number 12/443568 was filed with the patent office on 2010-02-04 for antiglare film, antiglare sheet, process for producing them, and image display apparatus using them.
This patent application is currently assigned to NITTO DENKO CORPORATION. Invention is credited to Tatsuki Nagatsuka, Naoto Ooe.
Application Number | 20100027127 12/443568 |
Document ID | / |
Family ID | 39343986 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100027127 |
Kind Code |
A1 |
Ooe; Naoto ; et al. |
February 4, 2010 |
ANTIGLARE FILM, ANTIGLARE SHEET, PROCESS FOR PRODUCING THEM, AND
IMAGE DISPLAY APPARATUS USING THEM
Abstract
An antiglare film and an antiglare sheet with which an image
display apparatus excelling in contrast while maintaining excellent
antiglare performance is obtained, and a simple process for
producing them are provided. In the antiglare film of the present
invention, a rugged shape in a first direction is substantially
different from a rugged shape in a second direction perpendicular
to the first direction. Preferably, an average gradient angle
.theta.a.sub.1 of the rugged shape in the first direction is larger
than an average gradient angle .theta.a.sub.2 of the rugged shape
in the second direction. More preferably, a difference
.DELTA..theta.a=.theta.a.sub.1-.theta.a.sub.2 between the average
gradient angle .theta.a.sub.1 and the average gradient angle
.theta.a.sub.2 is 0.5.degree. to 30.degree..
Inventors: |
Ooe; Naoto; (Osaka, JP)
; Nagatsuka; Tatsuki; (Osaka, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
NITTO DENKO CORPORATION
Ibaraki-shi, Osaka
JP
|
Family ID: |
39343986 |
Appl. No.: |
12/443568 |
Filed: |
September 12, 2007 |
PCT Filed: |
September 12, 2007 |
PCT NO: |
PCT/JP2007/067699 |
371 Date: |
March 30, 2009 |
Current U.S.
Class: |
359/614 ;
427/277 |
Current CPC
Class: |
G02B 5/0231 20130101;
G02B 5/021 20130101; G02B 1/11 20130101; G02B 5/02 20130101; G02B
27/0018 20130101 |
Class at
Publication: |
359/614 ;
427/277 |
International
Class: |
G02B 1/11 20060101
G02B001/11; B05D 3/12 20060101 B05D003/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2006 |
JP |
2006-293503 |
Claims
1. An antiglare film in which a rugged shape in a first direction
is substantially different from a rugged shape in a second
direction perpendicular to the first direction.
2. An antiglare film according claim 1, wherein an average gradient
angle .theta.a.sub.1 of the rugged shape in the first direction is
larger than an average gradient angle .theta.a.sub.2 of the rugged
shape in the second direction.
3. An antiglare film according to claim 2, wherein a difference
.DELTA..theta.a=.theta.a.sub.1-.theta.a.sub.2 between the average
gradient angle .theta.a.sub.1 and the average gradient angle
.theta.a.sub.2 is 0.5.degree. to 30.degree..
4. An antiglare film according to claim 2, wherein the average
gradient angle .theta.a.sub.1 is 1.degree. to 30.degree..
5. An antiglare film according to claim 2, wherein the average
gradient angle .theta.a.sub.2 is 0.degree. to 5.degree..
6. An antiglare film according to claim 1, having a thickness of 2
.mu.m to 50 .mu.m.
7. An antiglare film according to claim 1, which is formed of a
curable resin and subjected to embossment on a surface thereof.
8. An antiglare film according to claim 7, wherein the curable
resin is at least one selected from an acrylic resin, a
urethane-based resin, and an epoxy-based resin.
9. An antiglare sheet comprising a base and the antiglare film,
placed on the base, according to claim 1.
10. An antiglare sheet according to claim 9, wherein the base
contains a polyester-based resin.
11. An optical laminate comprising the antiglare film according to
claim 1 or an antiglare sheet comprising a base and the antiglare
film, placed on the base or wherein the base contains a
polyester-based resin, and a polarizer.
12. An optical laminate according to claim 11, wherein an angle
formed by an absorption axis of the polarizer and the first
direction in the antiglare film is substantially 45.degree. or
-45.degree. in a clockwise direction.
13. An optical laminate according to claim 11, wherein an
absorption axis of the polarizer and the first direction are
substantially parallel to each other.
14. An image display apparatus comprising claim 1, an antiglare
sheet comprising a base and the antiglare film, placed on the base
or wherein the base contains a polyester-based resin, or an optical
laminate comprising the antiglare film according to claim 1 or the
antiglare sheet comprising a base and the antiglare film, placed on
the base or wherein the base contains a polyester-based resin and a
polarizer.
15. An image display apparatus according to claim 14, wherein the
antiglare film, the antiglare sheet, or the optical laminate is
placed so that the first direction corresponds to a horizontal
direction of a display screen, and the second direction corresponds
to a vertical direction of the display screen.
16. A process for producing an antiglare film, comprising: applying
a solution of a curable resin to form a resin film; forming a
predetermined rugged shape in a first direction of the resin film,
and forming a rugged shape, which is different from the rugged
shape in the first direction, in a second direction perpendicular
to the first direction; and curing the resin film with the rugged
shape formed thereon.
17. An process for producing an antiglare film according to claim
16, wherein the rugged shape is formed by embossment.
Description
TECHNICAL FIELD
[0001] The present invention relates to an antiglare film and an
antiglare sheet. More specifically, the present invention relates
to an antiglare film and an antiglare sheet that can provide an
image display apparatus excelling in contrast while maintaining
excellent antiglare performance. The present invention also relates
to a simple process for producing the antiglare film and the
antiglare sheet. Further, the present invention relates to an image
display apparatus excelling in contrast with less so-called white
blurring, using the antiglare film or the antiglare sheet.
BACKGROUND ART
[0002] In image display apparatuses such as a liquid crystal
display (LCD) apparatus, an organic EL display apparatus, and a
plasma display panel (PDP) apparatus, indoor illumination such as
fluorescent light, sunlight incident through a window, a shadow of
an operator/viewer, or the like is reflected on a display screen,
which may impair the visibility of an image. In order to enhance
the visibility of an image, for example, an LCD surface is provided
with a light diffusing layer with a minute rugged structure. Such a
light diffusing layer can diffuse surface reflected light and
suppress the specular reflection of outdoor light, thereby
suppressing reflections (that is, the light diffusing layer has
antiglare performance).
[0003] As a method of forming such a light diffusing layer, a
method of applying a resin with fine particles dispersed therein
has been the mainstream because of the ease of formation of a fine
structure and excellent productivity (see, for example, Patent
Document 1). However, the entire surface of such a light diffusing
layer diffuses and reflects light strongly, consequently, there
arises a problem in that the contrast of a display screen is
degraded due to so-called white blurring (phenomenon in which a
display screen becomes whity during a black display).
[0004] Patent Document 1: JP 3743624 B
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0005] The present invention has been made for solving the
conventional problems as described above, and an object of the
present invention is to provide an antiglare film and an antiglare
sheet with which an image display apparatus excelling in contrast
while maintaining excellent antiglare performance is obtained, and
a simple process for producing them.
Means for Solving the Problems
[0006] An antiglare film of the present invention has a rugged
shape in a first direction and a rugged shape in a second direction
perpendicular to the first direction which are substantially
different from each other.
[0007] In a preferred embodiment, an average gradient angle
.theta.a.sub.1 of the rugged shape in the first direction is larger
than an average gradient angle .theta.a.sub.2 of the rugged shape
in the second direction. In a more preferred embodiment, a
difference .DELTA..theta.a=.theta.a.sub.1-.theta.a.sub.2 between
the average gradient angle .theta.a.sub.1 and the average gradient
angle .theta.a.sub.2 is 0.5.degree. to 30.degree..
[0008] In a preferred embodiment, the average gradient angle
.theta.a.sub.1 is 1.degree. to 30.degree.. In a preferred
embodiment, the average gradient angle .theta.a.sub.2 is 0.degree.
to 5.degree.. In a preferred embodiment, a thickness of the
antiglare film is 2 .mu.m to 50 .mu.m.
[0009] In a preferred embodiment, the antiglare film is formed of a
curable resin and subjected to embossment on a surface thereof. In
a more preferred embodiment, the curable resin is at least one
selected from an acrylic resin, a urethane-based resin, and an
epoxy-based resin.
[0010] According to another aspect of the present invention, an
antiglare sheet is provided. The antiglare sheet includes abase and
the antiglare film placed on the base. In a preferred embodiment,
the base contains a polyester-based resin.
[0011] According to still another aspect of the present invention,
an optical laminate is provided. The optical laminate includes the
antiglare film or the antiglare sheet, and a polarizer.
[0012] In a preferred embodiment, an angle formed by an absorption
axis of the polarizer and the first direction in the antiglare film
is substantially 45.degree. or -45.degree. in a clockwise
direction. In another preferred embodiment, an absorption axis of
the polarizer and the first direction are substantially parallel to
each other.
[0013] According to still another aspect of the present invention,
an image display apparatus is provided. The image display apparatus
includes the antiglare film, the antiglare sheet, or the optical
laminate.
[0014] In a preferred embodiment, the antiglare film, the antiglare
sheet, or the optical laminate is placed so that the first
direction corresponds to a horizontal direction of a display
screen, and the second direction corresponds to a vertical
direction of the display screen.
[0015] According to still another aspect of the present invention,
a process for producing an antiglare film is provided. The process
for producing an antiglare film includes applying and drying a
solution of a curable resin to form a resin film; forming a
predetermined rugged shape in a first direction of the resin film,
and forming a rugged shape, which is different from the rugged
shape in the first direction, in a second direction perpendicular
to the first direction; and curing the resin film with the rugged
shape formed thereon.
[0016] In a preferred embodiment, the rugged shape is formed by
embossment.
Effects of the Invention
[0017] According to the present invention, by allowing the rugged
surface shape of an antiglare film to have anisotropy, there can be
provided the antiglare film with which an image display apparatus
excelling in contrast while maintaining excellent antiglare
performance can be obtained. More specifically, in a conventional
image display apparatus (for example, a flat panel display such as
a liquid crystal display apparatus), a display screen specularly
reflects outdoor light due to smoothness thereof, which causes a
phenomenon of reflections. In contrast, when an antiglare film with
an isotropic rugged surface is attached, although reflections can
be prevented by diffused reflection, a white blurring phenomenon
occurs inevitably due to the diffused reflection. According to the
present invention, by adopting a rugged surface shape with
particular anisotropy, the balance between the specular reflection
and the diffused reflection can be kept appropriately
(specifically, the rugged surface shape can subject outdoor light
from above to specular reflection as a smooth surface, and can
subject outdoor light from back and horizontal directions to
diffused reflection appropriately). Consequently, reflections and
white blurring, which have not been simultaneously prevented
conventionally, can be prevented simultaneously.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] [FIG. 1] A schematic view illustrating a rugged surface
shape of an antiglare film according to a preferred embodiment of
the present invention.
[0019] [FIG. 2] A schematic view illustrating a calculation method
of an average gradient angle.
[0020] [FIG. 3] A schematic cross-sectional view of an antiglare
sheet according to a preferred embodiment of the present
invention.
[0021] [FIG. 4] A schematic view illustrating a process for
producing an antiglare film according a preferred embodiment of the
present invention.
[0022] [FIG. 5] A laser micrograph of a surface shape of an
antiglare film obtained in an example of the present invention.
DESCRIPTION OF SYMBOLS
[0023] 10 first direction
[0024] 20 second direction
[0025] 100 antiglare film
[0026] 110 base
[0027] 200 antiglare sheet
BEST MODE FOR CARRYING OUT THE INVENTION
[0028] A. Antiglare Film
[0029] An antiglare film of the present invention has a rugged
surface shape with anisotropy. More specifically, as shown in FIG.
1, in an antiglare film 100 of the present invention, a rugged
shape when viewed in a first direction 10 and a rugged shape when
viewed in a second direction 20 perpendicular to the first
direction are substantially different. Preferably, the surface
roughness of the rugged shape when viewed in the first direction 10
is larger than the surface roughness of the rugged shape when
viewed in the second direction 20. That is, the rugged shape when
viewed in the first direction 10 has a statistical average distance
between the mountain and the valley of the rugged shape larger than
that when viewed in the second direction 20. FIG. 1 is a schematic
view for allowing the rugged shape of the antiglare film of the
present invention to be understood easily, and needless to say, an
actual antiglare film may not have such an extreme rugged
shape.
[0030] More preferably, an average gradient angle .theta.a.sub.1 of
the rugged shape in the first direction 10 is larger than an
average gradient angle .theta.a.sub.2 of the rugged shape in the
second direction 20. More specifically, a difference
.DELTA..theta.a=.theta.a.sub.1-.theta.a.sub.2 between the average
gradient angle .theta.a.sub.1 and the average gradient angle
.theta.a.sub.2 is preferably 0.5.degree. to 30.degree., more
preferably 0.5.degree. to 25.degree., particularly preferably
1.degree. to 20.degree., and most preferably 1.degree. to
7.degree.. With such a relationship, white blurring and reflections
can be prevented satisfactorily while antiglare performance is
maintained. Note that .theta.a.sub.1 and .theta.a.sub.2 can be
respectively increased or decreased appropriately by changing the
level difference of the rugged shape per unit length in the first
and second directions. For example, .theta.a.sub.1 can be increased
by increasing the level difference of the rugged shape in the first
direction, and .theta.a.sub.1 can be decreased by decreasing the
level difference of the rugged shape in the first direction.
[0031] Herein, the "average gradient angle" refers to the average
of the gradient of a straight line connecting the mountain to the
valley of a surface roughness curve in a standard length. For
example, as shown in FIG. 2, assuming that every height (distance
between the mountain and the valley) at a standard length L is
h.sub.1, h.sub.2, h.sub.3, h.sub.4, . . . h.sub.n, the average
gradient angle .theta.a is represented by the following expression.
In the antiglare film having a rugged surface shape with anisotropy
according to the present invention, no strict correlation is found
between the average gradient angle .theta.a and the surface
roughness Ra. For example, in the case where the surface roughness
Ra.sub.1 in the first direction is larger than the surface
roughness Ra.sub.2 in the second direction, the average gradient
angle .theta.a.sub.1 in the first direction is larger than the
average gradient angle .theta.a.sub.2 in the second direction in
many cases. The opposite case may occur. On the other hand, in a
conventional antiglare film having isotropic (random) rugged shape,
.theta.a.sub.1 and .theta.a.sub.2 are substantially equal, and
Ra.sub.1 and Ra.sub.2 are substantially equal. It is one of the
achievements of the present invention to have found the
relationship between the average gradient angle in two directions,
and the white blurring and reflections in an antiglare film with an
isotropic rugged surface shape.
.theta. a = tan - 1 ( h 1 + h 2 + h 3 + h 4 + + h n L ) [ Numerical
Expression 1 ] ##EQU00001##
[0032] The average gradient angle .theta.a.sub.1 is preferably
1.degree. to 30.degree., more preferably 2.degree. to 27.degree.,
particularly preferably 3.5.degree. to 15.degree., and most
preferably 3.5.degree. to 10.degree.. Further, the average gradient
angle .theta.a.sub.2 is preferably 0.degree. to 5.degree., more
preferably 0.1.degree. to 3.5.degree., particularly preferably
0.1.degree. to 2.5.degree., and most preferably 0.2.degree. to
1.5.degree.. By setting the average gradient angles .theta.a.sub.1
and .theta.a.sub.2 respectively in such ranges, the white blurring
and reflections can be further prevented.
[0033] The thickness of the antiglare film of the present invention
is preferably 2 .mu.m to 50 .mu.m, and more preferably 3 .mu.m to
30 .mu.m. If the thickness is in such ranges, a desired rugged
shape can be formed, and the transparency and mechanical strength
of the film also can be ensured.
[0034] As a material constituting the antiglare film of the present
invention, any suitable material usable in an optical film can be
adopted. Preferably, the antiglare film of the present invention is
formed of a curable resin. Specific examples of the curable resin
include an energy line curable resin and a thermosetting resin.
Specific examples of the energy line include an electron beam and
light (e.g., UV-light, visible light). When such a curable resin is
used, the curable resin can be cured substantially completely after
a desired rugged shape is formed, whereby the formed rugged shape
can be solidified. Consequently, a film excellent in durability,
retention, and stability of a rugged shape can be obtained.
Specific examples of such a curable resin include an acrylic resin,
a urethane-based resin, an epoxy-based resin, an acrylic
urethane-based resin, a polyester-based resin, an amide-based
resin, and a silicone-based resin. The acrylic resin,
urethane-based resin, and epoxy-based resin are preferred. Those
curable resins can be used alone or in combination. Those curable
resins are generally available in a liquid composition form.
[0035] The curable resin (liquid composition) can further contain
any suitable additives in accordance with the purpose. Specific
examples of the additives include a surfactant, a plasticizer, an
antioxidant, a conductivity providing material, a UV-absorber, a
photostabilizer, a cross-linking agent, a cross-linking assistant,
a polymerization initiator, and a thickener. By adjusting the kind
and/or amount of the additives to be used, an antiglare film having
desired properties can be obtained in accordance with the
purpose.
[0036] The rugged shape of the antiglare film of the present
invention is preferably formed by embossment. The method of forming
a rugged shape will be described in detail in the item C described
later.
[0037] B. Antiglare Sheet
[0038] FIG. 3 is a schematic cross-sectional view of an antiglare
sheet according to a preferred embodiment of the present invention.
An antiglare sheet 200 includes a base 110 and an antiglare film
100 placed on the base. The antiglare film is as described in the
item A. In one embodiment, the base and the antiglare film are
laminated directly (that is, via no adhesion layer).
[0039] The above base is typically formed of a film containing a
resin which is transparent and small optical birefringence.
Specific examples of the resin include: polyester-based resins such
as polyethylene terephthalate, polyethylene naphthalate;
cellulose-based resins such as diacetyl cellulose and triacetyl
cellulose; polycarbonate-based resins; acrylic resins such as
polymethyl methacrylate; styrene-based resins such as polystyrene
and a acrylonitrile-styrene copolymer; olefin-based resins such as
polyethylene, polypropylene, polyolefin having a cyclic or
norbornene structure and an ethylene-propylene copolymer; vinyl
chloride-based resin; amide-based resins such as nylon and aromatic
polyamide; imide-based resins; sulfone-based resins; polyether
sulfone-based resins; polyether ether ketone-based resins;
polyphenylene sulfide-based resins; vinyl alcohol-based resins;
vinylidene chloride-based resins; vinyl butyral-based resins;
arylate-based resins; polyoxymethylene-based resins; epoxy-based
resins; and blended products thereof. Preferred are polyester-based
resins and particularly preferred is polyethylene
terephthalate.
[0040] The thickness of the base is preferably 1 .mu.m to 500 .mu.m
and more preferably 20 .mu.m to 300 .mu.m.
[0041] C. Process for Producing Antiglare Film and Antiglare
Sheet
[0042] FIG. 4 is a schematic view illustrating a process for
producing an antiglare film according to a preferred embodiment of
the present invention. First, a solution of a curable resin is
applied to the transported base 110 to form a coating layer (resin
film) 100'. The curable resin is as described in the item A. The
curable resin is generally available in a liquid composition form,
and hence it can be applied directly. Alternatively, the curable
resin may be applied after the viscosity thereof is adjusted by
diluting the curable resin with a predetermined solvent or adding a
thickener to the curable resin. By adjusting the viscosity, the
coating thickness is adjusted, and as a result, the thickness of
the antiglare sheet can be adjusted. If required, the flow of the
coating layer may be prevented or suppressed by subjecting the
curable resin after being applied to a predetermined heat
treatment. The heating temperature and heating time can be adjusted
appropriately depending upon the kind of the curable resin, the
kind and content of the solvent, the viscosity of the coating
liquid, the desired thickness, and the like. The coating layer can
be formed directly on the base with no adhesion layer or the like.
If required, the base may be subjected to a treatment (for example,
a corona treatment, a flame treatment) for enhancing the
adhesiveness between the base and the coating layer.
[0043] As the application method 120 of the curable resin solution,
any appropriate method may be employed. Specific examples of the
method include: coating methods such as an air doctor coating, a
blade coating, a knife coating, a reverse coating, a transfer roll
coating, a gravure roll coating, a kiss coating, a cast coating, a
spray coating, a slot orifice coating, a calendar coating, an
electrocoating, a dip coating, and a die coating; printing methods
such as a letterpress printing such as aniline printing, a intaglio
printing such as a direct gravure printing and an offset gravure
printing, a litho printing such as an offset printing, and a
stencil printing such as a screen printing.
[0044] Next, a predetermined rugged shape is formed in a first
direction on the surface of the coating layer 100', and a rugged
shape different from the rugged shape in the first direction is
formed in a second direction perpendicular to the first direction.
Such a rugged shape with anisotropy is preferably formed by
embossment. More specifically, the embossment is performed by
allowing a laminate of the base 110/coating layer 100' to be
pressed with an emboss roll 130. By using the emboss roll, the
following advantages are obtained: (1) a rugged shape with
anisotropy, which has been substantially impossible to form
according to a method of dispersing particles to form a rugged
shape, can be formed; (2) films transported continuously are
subjected to embossment, which can realize excellent productivity;
(3) the reproducibility of a rugged shape is remarkably excellent,
compared with the case of dispersing particles to form a rugged
shape, and hence the variation in films can be prevented
remarkably; and (4) it is only necessary to shape the surface of an
emboss roll and transfer the shape to a film, and therefore,
compared with the case of forming a rugged shape directly on a
film, a rugged shape as designed can be formed on a film, and it is
very easy to design such a rugged shape.
[0045] Next, the coating layer 100' with a rugged shaped formed on
the surface is completely cured to form an antiglare film 100. The
curing method and curing conditions can be appropriately selected
depending upon the kind of the curable resin. For example, if the
curable resin is an electron beam curable resin (for example,
UV-curable resin), the curable resin may be irradiated with an
electron beam (e.g., UV-light), and if the curable resin is a
thermosetting resin, the curable resin may be heated. In the case
of using the electron beam curable resin, the coating layer may be
cured by being irradiated with an electron beam, and thereafter,
may be heat-treated, if required, to evaporate a solvent.
[0046] As described above, the antiglare sheet 200 having the base
110 and the antiglare film 100 is obtained. In the case of using
the antiglare film alone, the base may be peeled. In this case, the
base may have been subjected to any suitable peeling treatment.
[0047] D. Optical Laminate
[0048] The optical laminate of the present invention includes the
antiglare film or the antiglare sheet, and a polarizer. In one
embodiment, the antiglare film or the antiglare sheet and the
polarizer are laminated via an adhesion layer. Preferably, the
optical laminate includes the antiglare film, the base, and the
polarizer in the stated order. According to such an embodiment, the
base also functions as a protective layer of the polarizer, thereby
enhancing the durability of the polarizer. Further, in the case
where the optical laminate is exposed to a high-temperature or
low-temperature environment, a stress involved in the expansion or
contraction of the polarizer is not transmitted directly to the
antiglare film, and hence cracks can be prevented from being
generated in the antiglare film.
[0049] As the polarizer, any suitable polarizer can be adopted.
Specific examples include: a stretched film of a polymer film
containing a polyvinyl alcohol-based resin as a main component,
which contains iodine or a dichroic dye; an O-type polarizer in
which a liquid crystalline composition containing a dichroic
substance and a liquid crystalline compound is aligned in a
constant direction, as disclosed in U.S. Pat. No. 5,523,863; and an
E-type polarizer in which a lyotropic liquid crystal is aligned in
a constant direction, as disclosed in U.S. Pat. No. 6,049,428.
Preferably, the polarizer is the stretched film of a polymer film
containing a polyvinyl alcohol-based resin as a main component,
which contains iodine or a dichroic dye. This is because such a
stretched film has a high polarization degree and can enhance a
contrast ratio in a front direction of an image display apparatus.
Such a polymer film is produced by a method described in, for
example, JP 2001-315144 A [Example 1].
[0050] The transmittance (may also be referred to as single axis
transmittance) of the polarizer at a wavelength of 440 nm measured
at 23.degree. C. is preferably 41% or more and more preferably 43%
or more. Further, the polarization degree is preferably 99.8% or
more, and more preferably 99.9% or more.
[0051] In the case where the polarizer is a stretched film of a
polymer film containing a polyvinyl alcohol-based resin as a main
component, the adhesion layer is preferably composed of a
water-soluble adhesive. The water-soluble adhesive preferably
contains a polyvinyl alcohol-based resin as a main component. The
thickness of the adhesion layer is typically 0.1 .mu.m to 50 .mu.m,
and preferably 1 .mu.m to 30 .mu.m. If the thickness of the
adhesion layer is in the above ranges, an antiglare film and a
polarizer can be bonded without floating and peeling, and an
adhesive strength and an adhesion time without any adverse effects
in terms of a practical use can be obtained.
[0052] In one embodiment, the absorption axis of the polarizer and
the first direction of the antiglare film are substantially
parallel to each other. Such an optical laminate is used
particularly preferably in a normally black type liquid crystal
display apparatus, and white blurring and reflections can be
prevented satisfactorily. In another embodiment, an angle formed by
the absorption axis of the polarizer and the first direction of the
antiglare film is substantially 45.degree. or -45.degree. in a
clockwise direction. Such an optical laminate is used particularly
preferably in a normally white type liquid crystal display
apparatus, and white blurring and reflections can be prevented
satisfactorily.
[0053] E. Image Display Apparatus
[0054] The image display apparatus of the present invention
includes the antiglare film, the antiglare sheet, or the optical
laminate. Specific examples of the image display apparatus of the
present invention include a liquid crystal display (LCD) apparatus,
an organic EL display apparatus, a plasma display panel (PDP)
apparatus, and a field emission display (FED). Particularly
preferably, the image display apparatus of the present invention is
an image display apparatus with a large screen (for example, a
large liquid crystal television).
[0055] Preferably, the antiglare film, the antiglare sheet, or the
optical laminate is placed so that a first direction (an arrow 10
in FIG. 1) in the antiglare film corresponds to the horizontal
direction of a display screen, and a second direction (an arrow 20
in FIG. 1) corresponds to the vertical direction of the display
screen. For example, the antiglare film is placed so that the first
direction is substantially identical to the horizontal direction
(horizontally long direction) of the screen of a stationary liquid
crystal television. Due to such a configuration, white blurring can
be particularly prevented remarkably.
[0056] Hereinafter, the present invention will be described
specifically by way of examples; however, the present invention is
not limited to those examples. An evaluation method in the examples
will be described below.
(1) Average Gradient Angle .theta.a:
[0057] The rugged surface of an antiglare film was measured in a
length of 4 mm in a predetermined direction under conditions of a
scanning speed of 0.1 mm/sec. and a cut-off value of 0.8 mm by a
needle-contact surface roughness meter (High-precision micro figure
measuring instrument Surfcoder ET4000, manufactured by Kosaka
Laboratory Ltd.) having a measurement needle whose tip end made of
diamond has a radius of curvature R of 2 .mu.m, and an average
gradient angle .theta.a(.degree.) was obtained from the surface
roughness curve.
(2) Center Line Average Surface Roughness Ra:
[0058] A center line average surface roughness Ra was measured in
accordance with JIS B0601-1994. Specifically, a glass plate
(thickness: 1.3mm) manufactured by Matsunami Ind. Ltd. was attached
to a surface of the antiglare film opposite to the rugged surface
with a pressure-sensitive adhesive to create a sample, and an Ra
value of the sample was measured by High-precision micro figure
measuring instrument Surfcoder ET4000, manufactured by Kosaka
Laboratory Ltd.
(3) White Blurring:
(3-1) Visual Observation Evaluation:
[0059] A fluorescent light placed at an angle of about 50.degree.
with respect to a liquid crystal panel was lit, and the lightness
(whiteness) when viewing the liquid crystal panel from a front
surface was evaluated by visual observation in three stages.
Specifically, the case where almost no whiteness was found on the
panel was evaluated as .smallcircle.; the case where a part of the
panel became strong white or the case where a large part of the
panel was whitish was evaluated as .DELTA.; and the case where a
large part of the panel was strong white was evaluated as
.times..
(3-2) Front Brightness Evaluation:
[0060] A fluorescent light placed at an angle of about 50.degree.
with respect to a liquid crystal panel was lit to radiate 200
lux-light on the panel surface, and the brightness in a front
direction was measured by a brightness meter (BM-5A, manufactured
by Topcon Technohouse Corporation).
(4) Reflections:
[0061] A fluorescent light was placed in front of a liquid crystal
panel and was lit, and the clearness of a contour of the
fluorescent light reflected on the panel was evaluated by visual
observation in three stages. The case where the contour of the
fluorescent light was not recognized was evaluated as
.smallcircle.; the case where the contour was recognized although
it was not clear was evaluated as .DELTA.; and the case where the
contour was recognized clearly was evaluated as .times..
(5) Observation of Surface Shape of Antiglare Film
[0062] The surface shape of the antiglare film was observed using a
laser microscope (KEYENCE VK-8500 (monitor unit), VK-8510
(microscope body)).
Example 1
[0063] A UV-curable acrylic resin (Beam-set (product name),
manufactured by Arakawa Chemical Industries, Ltd.) was applied to a
polyethylene terephthalate (PET) film (Lumirror U34 (product name);
thickness of 100 .mu.m, manufactured by Toray Industries, Inc.)
with a comma coater in a thickness of 10 .mu.m, whereby a laminate
of a PET base/acrylic resin coating layer was produced.
Subsequently, the laminate was irradiated with UV-light from the
PET base side while being pressed against a roll embossed in a
predetermined surface shape to cure the coating layer, whereby an
antiglare sheet having a configuration of a base/antiglare film was
obtained. The irradiation strength of UV-light was 40 mW/cm.sup.2,
and the total irradiation amount of UV-light was 300 mJ/cm.sup.2.
Table 1 shows a surface roughness Ra.sub.1 and an average gradient
angle .theta.a.sub.1 in a first direction of the antiglare film of
the obtained antiglare sheet, a surface roughness Ra.sub.2 and an
average gradient angle .theta.a.sub.2 in a second direction, and
.DELTA..theta.. Further, FIG. 5 shows a laser micrograph of the
surface shape of the antiglare film.
[0064] The obtained antiglare sheet was attached to a liquid
crystal panel taken out from a notebook computer (Wide 17 type,
INSPIRON 630 m (Trade name), manufactured by Dell Computer
Corporation). At this time, the antiglare sheet was attached to the
liquid crystal panel so that the first direction of the antiglare
film (herein, the direction in which the average gradient angle
.theta.a is larger) is substantially identical to the horizontal
direction of a display screen, and the second direction (herein,
the direction in which the average gradient angle .theta.a is
smaller) is substantially identical to the vertical direction of
the display screen. The white blurring and reflections of the
liquid crystal panel to which the antiglare film was attached were
evaluated. Table 1 below shows the results.
TABLE-US-00001 TABLE 1 White blurring .theta.a1 .theta.a2
.DELTA..theta.a Ra1 Ra2 Front brightness (.degree.) (.degree.)
(.degree.) (.mu.m) (.mu.m) (Lx) Reflections Example 1 3.9 0.8 3.1
0.38 0.1 .smallcircle. (0.08) .smallcircle. Example 2 3.9 3.2 0.7
0.37 0.70 .smallcircle. (0.11) .smallcircle. Example 3 11.3 3.5 7.8
1.27 1.14 .smallcircle. (0.10) .smallcircle. Example 4 26.4 2.0
24.4 1.78 0.71 .smallcircle. (0.10) .smallcircle. Comparative 0.8
0.8 0 0.10 0.10 .smallcircle. (0.08) .DELTA. example 1 Comparative
3.9 3.9 0 0.37 0.37 .DELTA. (0.33) .smallcircle. example 2
Comparative 0.8 3.9 -3.1 0.1 0.38 .DELTA. (0.33) .DELTA. example 3
Comparative 2.0 26.4 -24.4 0.71 1.78 x (4.82) .smallcircle. example
4 Comparative 3.5 11.3 -7.8 1.15 1.27 x (4.19) .smallcircle.
example 5
Example 2
[0065] An antiglare sheet was obtained in the same way as in
Example 1, except for using an emboss roll having a different
surface shape (i.e., except for obtaining different Ra.sub.1,
.theta.a.sub.1, Ra.sub.2, .theta.a.sub.2, and .DELTA..theta.).
White blurring and reflections were evaluated in the same way as in
Example 1, except for using the antiglare sheet. Table 1 shows the
results.
Example 3
[0066] An antiglare sheet was obtained in the same way as in
Example 1, except for using an emboss roll having a different
surface shape (i.e., except for obtaining different Ra.sub.1,
.theta.a.sub.1, Ra.sub.2, .theta.a.sub.2, and .DELTA..theta.).
White blurring and reflections were evaluated in the same way as in
Example 1, except for using the antiglare sheet. Table 1 shows the
results.
Example 4
[0067] An antiglare sheet was obtained in the same way as in
Example 1, except for using an emboss roll having a different
surface shape (i.e., except for obtaining different Ra.sub.1,
.theta.a.sub.1, Ra.sub.2, .theta.a.sub.2, and .DELTA..theta.).
White blurring and reflections were evaluated in the same way as in
Example 1, except for using the antiglare sheet. Table 1 shows the
results.
Comparative Example 1
[0068] A commercially available polarizing plate with an antiglare
function (antiglare polarizing plate NPF-SEG-1425DUAG200,
manufactured by Nitto Denko Corporation) was attached to the same
liquid crystal panel as that in Example 1 in place of a viewer side
polarizing plate, and white blurring and reflections were
evaluated. Table 1 shows the results.
Comparative Example 2
[0069] A commercially available polarizing plate with an antiglare
function (antiglare polarizing plate NPF-SEG-1425DUAGS1,
manufactured by Nitto Denko Corporation) was attached to the same
liquid crystal panel as that in Example 1 in place of a viewer side
polarizing plate, and white blurring and reflections were
evaluated. Table 1 shows the results.
Comparative Example 3
[0070] The same antiglare film as that in Example 1 was used. The
antiglare film was attached to a liquid crystal panel in the same
way as in Example 1, except that the first direction (direction in
which the average gradient angle .theta.a is larger) was allowed to
be substantially identical to the vertical direction of a display
screen, and the second direction (direction in which the average
gradient angle .theta.a is smaller) was allowed to be substantially
identical to the horizontal direction of the display screen, and
white blurring and reflections were evaluated. Table 1 shows the
results.
Comparative Example 4
[0071] The same antiglare film as that in Example 3 was used. The
antiglare film was attached to a liquid crystal panel in the same
way as in Example 3, except that the first direction (direction in
which the average gradient angle .theta.a is larger) was allowed to
be substantially identical to the vertical direction of a display
screen, and the second direction (direction in which the average
gradient angle .theta.a is smaller) was allowed to be substantially
identical to the horizontal direction of the display screen, and
white blurring and reflections were evaluated. Table 1 shows the
results.
Comparative Example 5
[0072] The same antiglare film as that in Example 4 was used. The
antiglare film was attached to a liquid crystal panel in the same
way as in Example 4, except that the first direction (direction in
which the average gradient angle .theta.a is larger) was allowed to
be substantially identical to the vertical direction of a display
screen, and the second direction (direction in which the average
gradient angle .theta.a is smaller) was allowed to be substantially
identical to the horizontal direction of the display screen, and
white blurring and reflections were evaluated. Table 1 shows the
results.
[0073] As is apparent from the comparison between Examples 1 to 4
and Comparative Examples 1 to 2, the antiglare sheet of the
examples according to the present invention can simultaneously
prevent both reflections and white blurring. As is apparent from
Comparative Examples 3 to 5, the antiglare sheet of the present
invention is attached to an image display apparatus in a particular
positional relationship, whereby white blurring and reflections (in
particular, white blurring) can be prevented remarkably.
INDUSTRIAL APPLICABILITY
[0074] The antiglare film, the antiglare sheet, and the optical
laminate of the present invention can be respectively used
preferably in various kinds of image display apparatuses (for
example, a liquid crystal display apparatus, a self-emitting type
display apparatus) Specific examples of applicable image display
apparatuses include a liquid crystal display (LCD) apparatus, an
organic EL display apparatus, a plasma display panel (PDP)
apparatus, and a field emission display (FED).
* * * * *