U.S. patent application number 09/837495 was filed with the patent office on 2001-12-06 for antiglare layer, antiglare film, and optical element.
Invention is credited to Kobayashi, Shigeo, Matsunaga, Takuya, Satake, Masayuki, Shibata, Hiroshi, Shouda, Takashi.
Application Number | 20010048559 09/837495 |
Document ID | / |
Family ID | 18628854 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010048559 |
Kind Code |
A1 |
Matsunaga, Takuya ; et
al. |
December 6, 2001 |
Antiglare layer, antiglare film, and optical element
Abstract
The antiglare layer includes at least one resin coat layer (a)
containing particles and a resin coat layer (b) laminated on said
resin coat layer (a). The resin coat layer (b) contains particles
and has a surface uneven configuration. An average particle size of
the particles contained in the resin coat layer (b) is smaller than
or equal to an average particle size of the particles contained in
the resin coat layer (a), is capable of restraining the screen
glaring phenomenon while maintaining the antiglare property and in
which the whiting is observed to the least extent.
Inventors: |
Matsunaga, Takuya; (Osaka,
JP) ; Satake, Masayuki; (Osaka, JP) ;
Kobayashi, Shigeo; (Osaka, JP) ; Shibata,
Hiroshi; (Osaka, JP) ; Shouda, Takashi;
(Osaka, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
620 NEWPORT CENTER DRIVE
SIXTEENTH FLOOR
NEWPORT BEACH
CA
92660
US
|
Family ID: |
18628854 |
Appl. No.: |
09/837495 |
Filed: |
April 18, 2001 |
Current U.S.
Class: |
359/613 ;
359/601; 359/609 |
Current CPC
Class: |
G02B 1/11 20130101 |
Class at
Publication: |
359/613 ;
359/601; 359/609 |
International
Class: |
G02B 027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2000 |
JP |
2000-117552 |
Claims
What is claimed is:
1. An antiglare layer comprising: at least one resin coat layer (a)
containing particles; and a resin coat layer (b) laminated on said
resin coat layer (a), said resin coat layer (b) containing
particles and having a surface uneven configuration, wherein an
average particle size of the particles contained in the resin coat
layer (b) is smaller than or equal to an average particle size of
the particles contained in the resin coat layer (a).
2. The antiglare layer of claim 1, wherein a surface roughness of
the surface uneven structure of the resin coat layer (b) is from 14
to 60 .mu.m in terms of an average crest-to-bottom interval.
3. The antiglare layer of claim 1, wherein the average particle
size of the particles contained in the resin coat layer (b) is from
1 to 6 .mu.m, and the average particle size of the particles
contained in the resin coat layer (a) is from 2 to 10 .mu.m.
4. The antiglare layer of claim 1, further comprising a
reflection-preventive layer disposed on a surface of the uneven
configuration of the resin coat layer (b), said
reflection-preventive layer having a refractive index smaller than
that of the resin coat layer (b).
5. An antiglare film comprising an antiglare layer of claim 1
disposed on one side or on both sides of a transparent
substrate.
6. An antiglare film comprising an antiglare layer of claim 4
disposed on one side or on both sides of a transparent
substrate.
7. An optical element comprising an antiglare layer of claim 1
disposed on one side or on both sides of the optical element.
8. An optical element comprising an antiglare layer of claim 4
disposed on one side or on both sides of the optical element.
9. An optical element comprising an antiglare f ilm of claim 5
disposed on one side or on both sides of the optical element.
10. An optical element comprising an antiglare film of claim 6
disposed on one side or on both sides of the optical element.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an antiglare layer used for
restraining a screen glaring phenomenon attributable to highly fine
pixels in a liquid crystal display device or the like, a film
having the antiglare layer, and an optical element provided with
the antiglare film.
[0003] 2. Description of the Background Art
[0004] Hitherto, in a display device such as a liquid crystal
display device, an antiglare layer (having an antiglittering
property) has been disposed on the uppermost surface of a panel for
preventing reflection of an outside environment by diffusing
surface reflection light and restraining the regular reflection of
outside light, thereby to improve the visibility of images. A
generally known example of such an antiglare layer is a layer
obtained by sandblasting, or by filling a resin layer having a
thickness of from 5 to 10 .mu.m suitably with or transparent
particles to impart a fine uneven structure on the surface thereof.
In the case of highly fine liquid display device, however, when an
antiglare layer such as described above is mounted thereon, a
random intense-faint light is generated on the surface to aggravate
the glaring, thereby inviting a problem of decrease in the image
quality. In order to restrain such glaring, a method is proposed to
dispose two or more of the aforesaid resin coats. Although such
means can prevent the glaring phenomenon to some extent, the
glaring phenomenon is not yet sufficiently restrained.
[0005] In addition, the aforementioned antiglare layer having a
surface uneven configuration is effective in imparting the
antiglare property in the case where an average crest-to-bottom
interval is small to provide a dense structure, and the glaring
phenomenon can be restrained to some extent. On the other hand, in
the case of a structure having a dense surface uneven
configuration, a phenomenon called "whiting" occurs in which the
surface looks whity by random reflection of outside light on the
surface layer. This leads to a problem of decrease in the
visibility of black color display particularly in a display device
such as a liquid display device.
[0006] An object of the present invention is to provide an
antiglare layer, which is capable of restraining the screen-glaring
phenomenon while maintaining the antiglittering property and in
which the whiting is observed to the least extent. A further object
of the present invention is to provide a film having the antiglare
layer and an optical element provided with the antiglare film.
SUMMARY OF THE INVENTION
[0007] As a result of repeated eager studies to solve the
aforementioned problems of the prior art, the inventors have found
out that the aforesaid object can be achieved by an antiglare layer
having a structure described below, thereby completing the present
invention.
[0008] Namely, the present invention is directed to an antiglare
layer comprising at least one resin coat layer (a) containing
particles and a resin coat layer (b) laminated on the resin coat
layer (a), the resin coat layer (b) containing particles and having
a surface uneven configuration, wherein an average particle size of
the particles contained in the resin coat layer (b) is smaller than
or equal to an average particle size of the particles contained in
the resin coat layer (a).
[0009] In the present invention, the antiglare layer is made of a
laminate where the lower layer contains particles having a larger
average particle size than that of the particles contained in the
upper layer. As a consequence, light diffusion can be effectively
carried out in each layer, thereby restraining the glaring
phenomenon attributable to diffusion of backlight in a liquid
crystal display device.
[0010] Further, the antiglare layer of the present invention is
designed in such a manner that the average particle size of the
particles contained in the upper layer in the aforesaid laminate
structure is smaller than or equal to the average particle size of
the particles contained in the lower layer so that the particles
with a smaller average particle size appear in the upper layer.
Such a design mitigates the denseness of the surface uneven
configuration to some extent, increases the crest-to-bottom
interval of the surface uneven configuration to some extent, and
reduces the average slant angle, whereby the whiting can be
restrained. In the present invention, since the glaring is
restrained by the above-mentioned laminate structure, the glaring
on the surface is not so conspicuous to cause decrease in the image
quality or in the visibility of the display screen as in the case
of restraining the whiting by an antiglare layer with a
single-layer structure.
[0011] Further, the resin coat layer (a) constituting the lower
layer of the antiglare layer in the present invention serves to
improve the surface rubbing resistance and hardness.
[0012] In the aforesaid antiglare layer, a surface roughness of the
surface uneven structure of the resin coat layer (b) is preferably
from 14 to 60 .mu.m, more preferably from 20 to 50 .mu.m, in terms
of an average crest-to-bottom interval.
[0013] When the average crest-to-bottom interval is within the
above-mentioned range, the antiglaring property and the antiwhiting
property is obtained a good balance, hence it is preferable. The
average crest-to-bottom interval is more preferably less than or
equal to 30 .mu.m from the standpoint of the antiglittering
property and the antiglaring property, and is preferably more than
or equal to 30 .mu.m from the standpoint of the antiwhiting
property. Here, the average crest-to-bottom interval is a value
measured by using a contact-type surface roughness meter under a
condition with a trace distance of 3 mm and a speed of 0.3
mm/s.
[0014] In the aforesaid antiglare layer, the average particle size
of the particles contained in the resin coat layer (b) is
preferably from 1 to 6 .mu.m, and the average particle size of the
particles contained in the resin coat layer (a) is preferably from
2 to 10 .mu.m.
[0015] The average particle sizes of the particles contained in the
resin coat layer (a) and the resin coat layer (b) are not
specifically limited as long as the average particle size of the
particles contained in the resin coat layer (b) is relatively
smaller than or equal to the average particle size of the particles
contained in the resin coat layer (a). However, if the average
particle sizes of the particles are respectively within the
above-mentioned ranges, the antiglittering property, the
antiglaring property, and the antiwhiting property of the antiglare
layer can be effectively exhibited. The average particle size of
the particles contained in the lower resin coat layer (a) is more
preferably from 3 to 5 .mu.m in order to obtain a light-diffusing
effect more efficiently. The average particle size of the particles
contained in the upper resin coat layer (b) is more preferably from
2 to 3 .mu.m in order to exhibit the aforesaid surface uneven
configuration and to restrain the whiting to the minimum.
[0016] Further, the antiglare layer preferably includes a
reflection-preventive layer disposed on a surface of the uneven
configuration of the resin coat layer (b), the
reflection-preventive layer having a refractive index smaller than
that of the resin coat layer (b).
[0017] The reflection-preventive layer having a small refractive
index can restrain the surface reflection and reduces the whiting
more effectively.
[0018] In addition, the present invention is also directed to an
antiglare film including the aforesaid antiglare layer disposed on
one side or on both sides of a transparent substrate. The present
invention is also directed to an optical element including the
aforesaid antiglare layer or the aforesaid antiglare film disposed
on one side or on both sides of the optical element.
[0019] The antiglare layer of the present invention can be used for
various fields of use as an antiglare film disposed on a
transparent substrate, for example, in an optical element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is an illustration of an example of a film provided
with an antiglare layer of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Hereafter, preferred embodiments of the present invention
will be described with reference to the attached drawings.
[0022] FIG. 1 illustrates an antiglare film in which an antiglare
layer 4 is formed on a transparent substrate 1. In the antiglare
layer 4, an upper resin coat layer 2(b) having a surface uneven
configuration is formed on a lower resin coat layer 2(a). In FIG.
1, the shown lower resin coat layer 2(a) is made of a single layer;
however, the resin coat layer 2(a) may be made of plural
layers.
[0023] Particles 3(a) and 3(b) are contained in the resin coat
layers 2(a) and 2(b). The particles 3(a) in the resin coat layer
2(a) may be in the inside of the layer or at the interface between
the upper resin coat layer 2(b) and the resin coat layer 2(a), or
at the interface between the transparent substrate 1 and the resin
coat layer 2(a). The particles 3(b) in the resin coat layer 2(b)
form an uneven configuration on the surface of the antiglare
layer.
[0024] The resins constituting the resin coat layers 2(a) and 2(b)
may be, for example, an ultraviolet-curing resin. The
ultraviolet-curing resin may be one of a variety of resins
including polyester-type resins, acryl-type resins, urethane-type
resins, amide-type resins, silicone-type resins, and epoxy-type
resins, and maybe a monomer, an oligomer, a polymer, or the like of
ultraviolet-curing type. A preferably-used ultraviolet-curing resin
may be, for example, one having an ultraviolet-polymerizing
functional group, in particular, one containing an acryl-type
monomer or oligomer having two or more ultraviolet-polymerizing
functional groups, particularly from three to six of such
functional groups, as a component. The ultraviolet-curing type
resin may contain an ultraviolet polymerization initiator. Here,
the resins constituting the resin coat layer 2(a) and 2(b) may be
the same or different.
[0025] Examples of the particles 3(a) and 3(b) include inorganic
particles which may be electroconductive such as silica, alumina,
titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium
oxide, and antimony oxide, crosslinked or non-crosslinked organic
particles made of various polymers such as poly(methyl
methacrylate) or polyurethane, silicone-type particles, and others.
One or more suitable kinds of these particles may be used either
alone or in combination. Here, the particles 3(a) and 3(b) may be
the same or different.
[0026] The transparent substrate 1 may be a film made of a
transparent polymer. Examples of the polymers for forming the
transparent substrate 1 include polyester-type polymers such as
poly(ethylene terephthalate) and poly(ethylene naphthalate);
cellulosic-type polymers such as diacetylcellulose and
triacetylcellulose; polycarbonate-type polymers; acryl-type
polymers such as poly(methyl methacrylate); styrene-type polymers
such as polystyrene and acrylonitrile-styrene copolymer;
olefinic-type polymers such as polyethylene, polypropylene,
cyclo-type polyolefins, polyolefins having a norbornene structure,
and ethylene-propylene copolymer; vinyl chloride-type polymers;
amide-type polymers such as nylon and aromatic polyamides;
imide-type polymers; sulfone-type polymers; polyether sulfone-type
polymers; polyetheretherketone-type polymers; polyphenylene
sulfide-type polymers; vinylalcohol-type polymers; vinylidene
chloride-type polymers; vinyl butyral-type polymers; allylate-type
polymers; polyoxymethylene-type polymers; epoxy-type polymers; and
blends of the above-mentioned polymers.
[0027] The thickness of the transparent substrate 1 may be
appropriately determined and is typically from about 10 to about
500 .mu.m from the standpoints of the strength, the workability
such as a handling property, and the layer thinness. The thickness
of the transparent substrate 1 is preferably from 30 to 300 .mu.m,
more preferably from 50 to 200 .mu.m.
[0028] The aforesaid antiglare film may be produced as follows.
First, a resin (ultraviolet-curing resin, application solution)
containing particles 3(a) is applied onto the transparent substrate
1, followed by drying and curing to form a resin coat layer 2(a).
And, a resin (ultraviolet-curing resin, application solution)
containing particles 3(b) is applied, followed by drying and curing
to form a resin coat layer 2(b) having a surface uneven
configuration.
[0029] Applying the application solution onto the transparent
substrate 1 by a suitable method such as the doctor blade method or
the gravure roll coater method may form the resin coat layer 2(a).
The ratio of the particles 3(a) contained in the application
solution is not particularly limited; however, the ratio is
preferably from 5 to 20 parts by weight with respect to 100 parts
by weight of the resin, from the standpoint of the antiglaring
property. The thickness of the resin coat layer 2(a) is not
particularly limited; however, the thickness is preferably from
about 3 to about 10 .mu.m, more preferably from 3 to 5 .mu.m.
[0030] The surface uneven configuration of the resin coat layer
2(b) may be formed, for example, by a method of applying the
application solution by a suitable method such as the doctor blade
method or the gravure roll coater method so that the particles 3(b)
contained in the resin constituting the resin coat layer 2(b)
contribute to form the surface uneven configuration, as illustrated
in FIG. 1. The surface uneven configuration can also be formed by
surface roughening of the surface of the transparent substrate 1 by
a suitable method such as sandblasting, emboss rolling, or etching,
and successively applying the application solution on the roughened
surface.
[0031] The ratio of the particles 3(b) contained in the application
solution is not particularly limited; however, the ratio is
preferably from 2 to 18 parts by weight with respect to 100 parts
by weight of the resin, from the standpoint of the balance between
the antiglaring property and the antiwhiting property. The
thickness of the resin coat layer 2(b) is not particularly limited;
however, the thickness is preferably equal to or smaller than the
average particle size of the particles 3(b) contained in the resin
coat layer 2(b).
[0032] A reflection-preventive layer 5 may be disposed on the
surface of the uneven configuration of the resin coat layer (b),
which is the uppermost surface of the antiglare layer, as
illustrated in FIG. 1. The reflection-preventive layer 5 has a
refractive index smaller than that of the resin coat layer (b) and
may be made, for example, of fluorine-containing polysiloxane. The
thickness of the reflection-preventive layer 5 is not particularly
limited; however, the thickness is preferably from about 0.05 to
0.3 .mu.m, more preferably from 0.1 to 0.3 .mu.m.
[0033] Furthermore, an optical element (not illustrated) may be
attached to the antiglare film of FIG. 1. The optical element may
be, for example, a polarizing plate or a phase difference plate,
and these may be used as a laminate. The optical element can be
attached via a suitable adhesive layer, which is excellent in
transparency and weathering resistance, such as an acryl-type,
rubber-type, or silicone-type adhesive or a hot-melt-type adhesive,
in accordance with the needs.
[0034] Examples of the polarizing plate include a film obtained by
adsorbing iodine or a dichroic substance, e.g. a dichroic dye, onto
a hydrophilic polymer film such as a poly(vinyl alcohol)-type film,
a film of poly (vinyl alcohol)-type which has undergone partial
conversion into formal, or a film of a partially saponified
ethylene-vinyl acetate-type copolymer, and then stretching the
film. Examples of the polarizing plate further include a polarizing
film of dehydrated poly(vinyl alcohol) and a polarizing film of
dehydrochlorinated poly (vinyl chloride). Examples of the phase
difference plate include a uniaxially or biaxially stretched film
of a polymer film exemplified in the aforementioned transparent
substrate, and a liquid crystal polymer film. The phase difference
plate may be formed as a laminate of two or more layers of
stretched film. Laminating a polarizing plate and a phase
difference plate can form an elliptic polarizing plate.
EXAMPLES
[0035] Hereafter, examples of the present invention showing the
construction and the effects of the present invention will be
described. Here, parts and percentage (%) in each example refer to
parts and percentage (%) by weight, unless otherwise specifically
mentioned.
Example 1
[0036] (Formation of Resin Coat Layer (a))
[0037] An application solution with a concentration of 40% of solid
components, which was obtained by mixing 6 parts of silica
spherical particles having an average particle size of 3.0 .mu.m
and 0.5 part of a benzophenone-type photo-polymerization initiator
with respect to 100 parts of an ultraviolet-curing resin (urethane
acrylate-type monomer) by means of toluene, was applied onto a
triacetylcellulose film (80 .mu.m). After drying, the film was
subjected to curing by ultraviolet radiation to form a coat film (4
.mu.m) having a flat surface.
[0038] (Formation of Resin Coat Layer (b))
[0039] Further, an application solution with a concentration of 30%
of solid components, which was obtained by mixing 14parts of silica
spherical particles having an average particle size of 2.0 .mu.m
and 0.5 part of a benzophenone-type photo-polymerization initiator
with respect to 100 parts of an ultraviolet-curing resin (urethane
acrylate-type monomer) by means of toluene, was applied onto the
aforesaid coat film. After drying, the film was subjected to curing
by ultraviolet radiation to form a coat film (1.5 .mu.m) having a
surface uneven configuration with an average crest-to-bottom
interval of 20.1 .mu.m, thereby producing an antiglare film having
a two-layer structure.
Examples 2 to 6, and Comparative Examples 1 to 2
[0040] An antiglare film having a two-layer structure was produced
in the same manner as in Example 1 except that the average particle
size and/or the amount of use of the silica spherical particles for
forming the resin coat layers (a) and (b) were changed to those
shown in Table 1. The average crest-to-bottom interval of the
surface uneven configuration is shown in Table 1.
Example 7
[0041] Fluorine-containing polysiloxane was applied onto an uneven
configuration part of the uppermost surface of the antiglare film
obtained in Example 1, thereby to produce an antiglare film having
a reflection-preventive layer of 0.1 .mu.m thickness disposed
thereon.
Comparative Example 3
[0042] The resin coat layer (b) was formed without forming the
resin coat layer (a) in Example 1, thereby to produce an antiglare
film having a single-layer structure.
[0043] A film obtained by bonding a polarizing plate (185 .mu.m) to
the antiglare film of each of Examples and Comparative Examples was
bonded to a glass substrate. On a mask pattern (with an aperture
ratio of 25%) fixed to a light table, a degree of glaring
(antiglaring property) was evaluated by eye inspection with the
following standard. Further, a black tape was stuck onto the
surface of the glass substrate opposite to the surface having the
polarizing plate bonded thereto, and the whiting (antiwhiting
property) was evaluated by eye inspection with the following
standard. Each evaluation is a relative evaluation with ".times."
representing the case in which the antiglare film of Comparative
Example 5 was used. The results are shown in Table 1.
[0044] (Antiglaring Property)
[0045] .circleincircle. . . . no glaring at all
[0046] .smallcircle. . . . little glaring
[0047] .DELTA. . . . some glaring but raising no practical
problem
[0048] .times. . . . significant glaring
[0049] (Antiwhiting Property)
[0050] .circleincircle. . . . no whiting at all
[0051] .smallcircle. . . . little whiting
[0052] .DELTA. . . . some whiting but raising no practical
problem
[0053] .times. . . . significant whiting
1 TABLE 1 Particles of resin Particles of resin coat layer (a) coat
layer (b) Average Average Average crest-to-bottom particle particle
interval Antiglaring Antiwhiting (Parts) size (.mu.m) (Parts) size
(.mu.m) (.mu.m) property property Example 1 6 3 14 2 20.1
.largecircle. .largecircle. Example 2 12 3 14 2 31.5 .largecircle.
Example 3 6 3 12 2 46.6 .largecircle. .largecircle. Example 4 6 3
12 3 40.5 .largecircle. .largecircle. Example 5 6 3 16 2 15.0
.largecircle. .DELTA. Example 6 6 3 10 2 53.2 .DELTA. .largecircle.
Example 7 6 3 14 2 20.1 .largecircle. .largecircle. Comparative 0
-- 14 2 30.1 X .largecircle. Example 1 Comparative 6 1.5 14 2 30.5
X .largecircle. Example 2 Comparative None 14 2 20.1 X
.largecircle. Example 3
* * * * *