U.S. patent application number 11/252745 was filed with the patent office on 2006-03-09 for antireflection film.
This patent application is currently assigned to DAI NIPPON PRINTING CO., LTD.. Invention is credited to Fumihiro Arakawa, Hiroko Suzuki.
Application Number | 20060050387 11/252745 |
Document ID | / |
Family ID | 18592421 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060050387 |
Kind Code |
A1 |
Arakawa; Fumihiro ; et
al. |
March 9, 2006 |
Antireflection film
Abstract
An object of the present invention is to eliminate drawbacks of
conventional multi-layered antireflection films, that is, that a
lot of time is required in the formation of a transparent
conductive thin film and a low-refractive index layer leading to
low processing speed, the corrosion resistance of the transparent
conductive thin film is unsatisfactory, and the reflectance over
the whole visible light region is not constant. This object can be
attained by adopting a structure comprising: a transparent layer 3,
with a pencil hardness of H or more, formed of a cured product of
an ionizing radiation-curable resin composition; provided on one
side of the transparent layer 3, a concave-convex portion 2
comprising innumerable fine concaves and convexes provided at a
pitch of not more than the wavelength of light; a transparent
substrate film 1 optionally provided on the transparent layer 3 on
its side remote from the concave-convex portion 2; and a cover
layer, having a lower refractive index than the transparent layer,
preferably provided on the fine concaves and convexes.
Inventors: |
Arakawa; Fumihiro; (Tokyo,
JP) ; Suzuki; Hiroko; (Tokyo, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
DAI NIPPON PRINTING CO.,
LTD.
TOKYO
JP
|
Family ID: |
18592421 |
Appl. No.: |
11/252745 |
Filed: |
October 19, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09804081 |
Mar 13, 2001 |
|
|
|
11252745 |
Oct 19, 2005 |
|
|
|
Current U.S.
Class: |
359/487.02 ;
359/487.05; 359/599 |
Current CPC
Class: |
G02F 1/133528 20130101;
Y10S 359/90 20130101; G02B 1/118 20130101; G02F 1/133502 20130101;
G02B 1/11 20130101; H01J 29/896 20130101; H01J 2229/8915 20130101;
G02F 2201/38 20130101 |
Class at
Publication: |
359/491 ;
359/599 |
International
Class: |
G02B 5/30 20060101
G02B005/30 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2000 |
JP |
2000-074347 |
Claims
1. An antireflection film comprising: a transparent layer formed of
a cured product of an ionizing radiation-curable resin composition,
the transparent layer having a surface hardness of not less than H
in terms of pencil hardness as measured according to JIS K 5400; a
concave-convex portion provided on one side of the transparent
layer, the concave-convex portion having a specific continuous and
regular shape comprising fine concaves and convexes continuously
provided at a predetermined pitch of not more than the wavelength
of light; and a layer, provided on the fine concaves and convexes,
formed of a resin composition having a lower light refractive index
than a refractive index of the transparent layer.
2. The antireflection film according to claim 1, wherein the
transparent layer is backed by a transparent substrate film.
3. The antireflection film according to claim 1, which has
antistatic properties.
4. A polarizing element comprising: a polarizing plate; and,
stacked on the polarizing plate, an antireflection film comprising:
a transparent layer formed of a cured product of an ionizing
radiation-curable resin composition, the transparent layer having a
surface hardness of not less than H in terms of pencil hardness as
measured according to JIS K 5400; and a concave-convex portion
provided on one side of the transparent layer, the concave-convex
portion having a specific continuous and regular shape comprising
fine concaves and convexes continuously provided at a predetermined
pitch of not more than the wavelength of light.
5. A display device comprising: a display section; and, stacked or
disposed on the display section in its viewer side, the
antireflection film according to claim 1.
6. A display device comprising: a display section; and, stacked or
disposed on the display section in its viewer side, the polarizing
element according to claim 4.
7. The antireflection film according to claim 1, wherein the
transparent layer is formed of a resin selected from the group
consisting of: cellulose diacetate, cellulose triacetate, cellulose
acetate butyrate, polyester, polyamide, polyimide, polyether
sulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl
chloride, polyvinyl acetal, polyether ketone, methyl
polymethacrylate, polycarbonate, and polyurethane.
Description
[0001] This is a Continuation of Application No. 09/804,081 filed
Mar. 13, 2001. The entire disclosure of the prior application is
hereby incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to an antireflection film
which can prevent a lowering in visibility of various articles
caused by the glare of light as a result of the reflection of light
from the surface of the articles.
[0003] The present invention also relates to an antireflection film
which can develop antireflection properties by virtue of the
adoption of a structure of fine concaves and convexes, at a pitch
of not more than the wavelength of light, present on the surface
thereof, and a polarizing element and a display device using the
antireflection film.
BACKGROUND OF THE INVENTION
[0004] Liquid-crystal displays, CRT (cathode-ray tube) displays,
plasma displays or other displays are required to have high
visibility of images displayed on these displays. The reflection of
external light from the surface of displays, however, significantly
lowers the visibility.
[0005] Regarding materials other than displays, for example,
building materials of metals or glass, for example, having a gloss
surface sometimes cause unprepared light reflection which is
obstacle to the way of vehicles and pedestrians.
[0006] In order to eliminate the problem of a lowering invisibility
of displayed images and the various problems involved, for example,
in building materials, caused by the reflection of external light,
various antireflection films have been proposed.
[0007] A representative example of the proposed antireflection
films is an antireflection member described in Japanese Patent
Laid-Open No. 80205/1997. This antireflection member comprises a
transparent substrate, a hardcoat, and an antireflection optical
thin film having a two-layer structure provided in that order. The
first layer of the antireflection optical thin film is formed of
SnO.sub.2, ZnO, In.sub.8O.sub.3, ITO or the like, and the second
layer of the antireflection optical thin film is formed of
SiO.sub.2, MgF.sub.2 or other material having a lower refractive
index than the first layer of the antireflection optical thin film.
Thus, the claimed advantage of this antireflection member is such
that the hardcoat eliminates the susceptibility to scratching, the
first layer of the antireflection optical thin film offers
antistatic properties, and the first and second layers of the
antireflection optical thin film prevent reflection.
[0008] In the antireflection member having the above construction,
however, a thickness of several tens of nm is necessary for each of
the first and second layers of the antireflection optical thin
film. An attempt to form these layers, for example, by sputtering
requires a lot of time which thus disadvantageously results in low
processing speed.
[0009] In addition, transparent conductive thin layers formed of
ITO or the like posses excellent transparency, but on the other
hand, disadvantageously, the corrosion resistance is
unsatisfactory.
[0010] Further, in the antireflection member having the above
construction, the reflectance on red light side and blue light side
in the visible light region (wavelength 450 nm to 650 nm), in which
humans feels glaring, is not satisfactorily evenly lowered.
Specifically, since the antireflection properties vary depending
upon the wavelength or incident angle of incident light, a lowering
in reflectance in the whole visible light region is not realized
and, in this case, a change in color or glare is left.
[0011] Further, the antireflection member cannot satisfactorily
cope with scratch and stain caused at the time of handling.
[0012] For example, for a fine concave-convex film comprising a
fine concave-convex portion provided at a pitch of not more than
the wavelength of light on the surface of a transparent acrylic
resin film or the like, it is known that, at the bottom of concaves
and convexes, a major proportion thereof is accounted for by the
acrylic resin and, thus, the refractive index of this portion
limitlessly becomes close to the light refractive index of the
acrylic resin per se (about 1.49), while, toward the surface side
of the concaves and convexes, the proportion of the acrylic resin
lowers and, instead, the proportion of air increases to provide
lower refractive index and, around the outermost surface, the
refractive index limitlessly becomes close to the refractive index
of air (1.0), whereby the provision of the concaves and convexes
has the same effect as a stack of a plurality of layers which have
successively varied light refractive indexes.
[0013] The use of the fine concave-convex film as an antireflection
film, as compared with the conventional construction of a stack of
a plurality of layers for constituting an interference layer, has
advantages including that a change in color according to the visual
angle is less likely to take place, the number of layers
constituting the structure is small and, thus, the structure is
simple, but on the other hand, this fine concave-convex film is
disadvantageous in that, since the surface is formed of very fine
concaves and convexes, the film is likely to be scratched.
[0014] Further, in the production of the concave-convex film, a
method is adopted which comprises providing a visible light-curable
or other resin composition (a photoresist), creating cured portions
and uncured portions through the utilization of the interference of
visible light laser, and performing dissolution development to form
fine concaves and convexes. This method requires a lot of time in
exposure and development, and, thus, is unsuitable for mass
reproduction. Further, a resin composition having a relatively low
molecular weight suitable for this process is used as the raw
material. Therefore, even in the cured portion, the hardness is not
very high, and, thus, the surface hardness is also
unsatisfactory.
DISCLOSURE OF THE INVENTION
[0015] Accordingly, it is an object of the present invention to
eliminate the drawbacks of the prior art, that is, low processing
speed due to the necessity of a lot of time for the formation of
the transparent conductive thin layer and the formation of the
low-refractive index layer, unsatisfactory corrosion resistance of
the transparent conductive thin layer, and uneven reflectance in
the whole visible light region.
[0016] According to the present invention, a film having on its
surface fine concaves and convexes, which has solved the above
problems of the prior art, can be realized by providing a mold
having on its surface fine concaves and convexes, bringing a
curable resin composition into contact with the surface of the
mold, optionally covering the curable resin composition with a
transparent substrate, curing the curable resin composition, and,
after curing, separating the cured product of the curable resin
composition.
[0017] The first invention relates to an antireflection film
comprising: a transparent layer formed of a cured product of an
ionizing radiation-curable resin composition; and a concave-convex
portion provided on one side of the transparent layer, the
concave-convex portion comprising innumerable fine concaves and
convexes provided at a pitch of not more than the wavelength of
light.
[0018] The second invention relates to the antireflection film
according to the first invention, wherein the transparent layer is
backed by a transparent substrate film.
[0019] The third invention relates to the antireflection film
according to the first or second invention, wherein the transparent
layer has a surface hardness of not less than H in terms of pencil
hardness.
[0020] The fourth invention relates to the antireflection film
according to any one of the first to third inventions, which
further comprises, stacked on the concaves and convexes, a layer
formed of a resin composition having lower light refractive index
than the transparent layer.
[0021] The fifth invention relates to the antireflection film
according to any one of the first to fourth inventions, which has
antistatic properties.
[0022] The sixth invention relates to a polarizing element
comprising: a polarizing plate; and, stacked on the polarizing
plate, the antireflection film according to any one of the first to
fifth inventions.
[0023] The seventh invention relates to a display device
comprising: a display section; and, stacked or disposed on the
display section in its viewer side, the antireflection film
according to any one of the first to fifth inventions or the
polarizing element according to the sixth invention.
[0024] The eighth invention relates to a process for producing an
antireflection film, comprising the steps of: providing a mold with
an uneven surface having innumerable fine concaves and convexes at
a pitch of not more than the wavelength of light; applying, onto
the mold, an ionizing radiation-curable resin composition in an
amount large enough to at least fill the concaves of the mold
surface; after the application of the ionizing radiation-curable
resin composition, covering the top of the applied resin
composition with a transparent substrate film; after covering,
curing the ionizing radiation-curable resin composition located
between the transparent substrate film and the mold to produce a
cured product of the ionizing radiation-curable resin composition;
and then separating the cured product from the mold.
[0025] The ninth invention relates to the process for producing an
antireflection film according to the eighth invention, wherein the
transparent substrate film on its side for covering the ionizing
radiation-curable resin composition is separable and which further
comprises the step of separably adhering the transparent substrate
film, in curing the ionizing radiation-curable resin composition to
produce a cured product, onto the cured product and separating the
transparent substrate film from the cured product during, before or
after the separation of the cured product from the mold.
[0026] The tenth invention relates to the process for producing an
antireflection film according to the eighth invention, which
further comprises the step of adhering the transparent substrate
film, in curing the ionizing radiation-curable resin composition to
produce a cured product, onto the cured product and, in separating
the cured product from the mold, separating the transparent
substrate film together with the cured product.
[0027] The eleventh invention relates to the process for producing
an antireflection film according to any one of the eighth to tenth
inventions, wherein the mold with an uneven surface having fine
concaves and convexes is provided by forming concaves and convexes
of the mold in a photosensitive resin by a laser beam interference
method to produce an original mold and then producing a metallic
stamper from the original mold by a plating method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIGS. 1A and 1B are cross-sectional views showing the stack
structure of an antireflection films;
[0029] FIGS. 2A, 2B, 2C, 2D, and 2E are cross-sectional views
showing embodiments of the form of fine concaves and convexes
provided on the surface of an antireflection film;
[0030] FIGS. 3A, 3B, and 3C are diagrams showing the arrangement of
concaves and convexes;
[0031] FIG. 4 is a diagram showing a production apparatus;
[0032] FIG. 5 is a cross-sectional view showing an embodiment of
the application of an antireflection film to a polarizing plate;
and
[0033] FIG. 6 is a cross-sectional view showing an embodiment of
the application of an antireflection film to a liquid-crystal
panel.
BEST MODE FOR CARRYING OUT THE INVENTION
[0034] For example, as shown in FIG. 1A, an antireflection film 1
according to the present invention comprises: a transparent
substrate film 1; and, stacked on the transparent substrate film 1,
a transparent layer 3 having on its top surface a concave-convex
portion 2 having innumerable fine concaves and convexes at a pitch
of not more than the wavelength of light. In general, the
transparent layer 3 is a continuous layer. When the transparent
substrate film 1 is provided, however, the transparent layer 3 may
be formed of a group of discrete convexes.
[0035] Alternatively, as shown in FIG. 1B, the antireflection film
1 may further comprise a surface layer 4, constituted by a
different transparent layer, stacked on the concave-convex portion
2 located on the surface of the transparent layer 3. In the
drawing, the top of the surface layer 4 is shown as being flat. The
surface layer, however, may have a form conformed to the form of
the concave-convex portion 2.
[0036] In both the embodiments shown in FIGS. 1A and 1B, the
transparent substrate film 1 may not be provided.
[0037] Further, in both the embodiments shown in FIGS. 1A and 1B,
the provision of the concave-convex portion 2 is not limited to the
provision thereof on one side of the antireflection film 1, and the
concave-convex portion 2 may be formed on both sides of the
antireflection film 1.
[0038] Preferably, the transparent substrate film i is transparent
and smooth and is free from the inclusion of foreign matter.
Further, the transparent substrate film 1 preferably has mechanical
strength for fabrication and product use reasons. When heat of the
display is conveyed to the antireflection film, the transparent
substrate film 1 preferably has heat resistance.
[0039] Thermoplastic resin films, for example, cellulose diacetate,
cellulose triacetate, cellulose acetate butyrate, polyester,
polyamide, polyimide, polyether sulfone, polysulfone,
polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl
acetal, polyether ketone, methyl polymethacrylate, polycarbonate,
and polyurethane, are generally preferred as the transparent
substrate film 1.
[0040] Polyesters, which are frequently used in photographic films
coated with a photographic emulsion, are preferred from the
viewpoints of mechanical strength and suitability for coating.
Cellulose triacetate and the like are preferred from the viewpoints
of high transparency, the freedom from optical anisotropy, and low
refractive index, and polycarbonates are preferred from the
viewpoints of transparency and heat resistance.
[0041] These thermoplastic resin films are flexible and easy to use
and, including the time of handling, are not required to be bent at
all, and, when a hard product is desired, plates, such as the resin
plate or the glass plate, may also be used.
[0042] The thickness of the transparent substrate film 1 is
preferably about 8 to 1000 .mu.m, more preferably about 25 to 300
.mu.gm. In the case of plates, the thickness may exceed the above
upper limit.
[0043] In the transparent substrate film 1, in order to improve the
adhesion to a layer formed on the upper surface thereof, or layers
formed on respective upper and lower surfaces thereof, in general,
the transparent substrate film 1 may be subjected to conventional
various treatments, that is, physical treatments, such as corona
discharge treatment or oxidation, or alternatively, a primer layer
(not shown) maybe formed on the transparent substrate film 1 by
previously coating a coating composition called an anchor agent or
a primer.
[0044] The transparent layer 3 provided with the concave-convex
portion 2 of innumerable fine concaves and convexes is formed of a
cured product of an ionizing radiation-curable resin
composition.
[0045] Preferably, the ionizing radiation-curable resin composition
is high in curing speed in the formation of the concave-convex
portion 2 by casting using a mold, and comes to have high scratch
resistance after curing from the viewpoint of avoiding the scratch
of the surface of the transparent layer 3.
[0046] The ionizing radiation-curable resin composition is more
preferably such that the hardness after curing is not less than "H"
as measured by a pencil hardness test according to JIS K 5400.
[0047] Regarding the light refractive index of the transparent
layer 3, lower refractive index is preferred from the viewpoint of
antireflection properties. From the viewpoint of long-term use as
the antireflection film, however, the surface should have fastness
properties, particularly scratch resistance. In this case, higher
hardness is advantageous, and, thus, the density should be
increased to enhance the hardness. For this reason, the light
refractive index of the transparent layer 3 is preferably 1.4 to
1.7, more preferably not more than 1.6.
[0048] The ionizing radiation-curable resin composition may be a
mixture prepared by properly mixing prepolymer, oligomer, and/or
monomer, having a polymerizable unsaturated bond or an epoxy group
in the molecule thereof, together. The ionizing radiation refers to
electromagnetic radiations or charged particle beams which have
energy quantum high enough to polymerize or crosslink the molecule.
In general, ultraviolet light or electron beam is used.
[0049] Examples of prepolymers and oligomers usable in the ionizing
radiation-curable resin composition include: unsaturated
polyesters, such as condensation products between unsaturated
dicarboxylic acids and polyhydric alcohols; methacrylates, such as
polyester methacrylate, polyether methacrylate, polyol
methacrylate, and melamine methacrylate; acrylates, such as
polyester acrylate, epoxy acrylate, urethane acrylate, polyether
acrylate, polyolacrylate, andmelamineacrylate; and cationically
polymerizable epoxy compounds.
[0050] Examples of monomers usable in the ionizing radiation
curable resin composition include: styrene monomers, such as
styrene and .alpha.-methylstyrene; acrylic esters, such as methyl
acrylate, .alpha.-ethylhexyl acrylate, methoxyethyl acrylate,
butoxyethyl acrylate, butyl acrylate, methoxybutyl acrylate, and
phenyl acrylate; methacrylic esters, such as methyl methacrylate,
ethyl methacrylate, propyl methacrylate, methoxyethyl methacrylate,
ethoxymethyl methacrylate, phenyl methacrylate, and lauryl
methacrylate; unsaturated substituted-type substituted amino
alcohol esters, such as 2-(N,N-diethylamino) ethyl acrylate,
2-(N,N-dimethylamino) ethyl acrylate, 2-(N,N-dibenzylamino)methyl
acrylate, and 2-(N,N-diethylamino)propyl acrylate; unsaturated
carboxylic acid amides, such as acrylamide and methacrylamide;
compounds, such as ethylene glycol diacrylate, propylene glycol
diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate,
and triethylene glycol diacrylate; polyfunctional compounds, such
as dipropylene glycol diacrylate, ethylene glycol diacrylate,
propylene glycol dimethacrylate, and diethylene glycol
dimethacrylate; and/or polythiol compounds having two or more thiol
groups in the molecule thereof, for example, trimethylolpropane
trithioglycolate, trimethylolpropane trithiopropylate, and
pentaerythritol tetrathioglycolate.
[0051] In general, one of or a mixture of two or more of the above
compounds may be optionally used as the monomer in the ionizing
radiation-curable resin composition. In this case, from the
viewpoint of imparting ordinary suitability for coating to the
ionizing radiation-curable resin composition, the content of the
prepolymer or oligomer is preferably not less than 5% by weight,
and the content of the monomer and/or polythiol compound is not
more than 95% by weight.
[0052] When flexibility is required of a cured product of the
ionizing radiation-curable resin composition, the amount of the
monomer may be reduced, or alternatively, an acrylate monomer with
the number of functional groups being one or two may be used. On
the other hand, when abrasion resistance, heat resistance, and
solvent resistance are required of the cured product of the
ionizing radiation-curable resin composition, the ionizing
radiation-curable resin composition maybe designed, for example, so
that an acrylate monomer having three or more functional groups is
used. Monomers having one functional group include 2-hydroxy
acrylate, 2-hexyl acrylate, and phenoxyethyl acrylate. Monomers
having two functional groups include ethylene glycol diacrylate and
1,6-hexanediol diacrylate. Monomers having three or more functional
groups include trimethylolpropane triacrylate, pentaerythritol
tetraacrylate, pentaerythritol tetraacrylate, and dipentaerythritol
hexaacrylate.
[0053] A resin not curable upon exposure to an ionizing radiation
may also be added to the ionizing radiation-curable resin
composition in order to regulate properties, for example, the
flexibility and surface hardness of the cured product of the
ionizing radiation-curable resin composition. Specific examples of
resins usable herein include thermoplastic resins, such as
polyurethane resins, cellulosic resins, polyvinyl butyral resins,
polyester resins, acrylic resins, polyvinyl chloride resins, and
polyvinyl acetate resins. Among them, the addition of polyurethane
resin, cellulosic resin, polyvinylbutyral resin or the like is
preferred from the viewpoint of improving the flexibility.
[0054] When the ionizing radiation-curable resin composition is
curedbyultraviolet irradiation, aphotopolymerization initiator or a
photopolymerization accelerator may be added. Photopolymerization
initiators usable in the case of a resin system having a radically
polymerizable unsaturated group include acetophenones,
benzophenones, thioxanthones, benzoin, and benzoin methyl ether.
They may be used alone or as a mixture of two or more. On the other
hand, photopolymerization initiators usable in the case of a resin
system having a cationically polymerizable functional group include
aromatic diazonium salts, aromatic sulfonium salts, aromatic
iodonium salts, metallocene compounds, and benzoinsulfonic esters.
They may be used alone or as a mixture of two or more. The amount
of the photopolymerization initiator added may be 0.1 to 10 parts
by weight based on 100 parts by weight of the ionizing
radiation-curable resin composition.
[0055] The following organic reactive silicon compounds may be used
in combination with the ionizing radiation-curable resin
composition.
[0056] A first type of organosilicon compounds usable herein
includes those represented by formula R.sub.mSi(OR')n wherein R and
R' each represent an alkyl group having 1 to 10 carbon atoms and m
(subscript of R) and n (subscript of R') are each an integer with
m+n=4.
[0057] Specific examples of this type of organosilicon compounds
include tetramethoxysilane, tetraethoxysilane,
tetra-iso-propoxysilane, tetra-n-propoxysilane,
tetra-n-butoxysilane, tetra-sec-butoxysilane,
tetra-tert-butoxysilane, tetrapentaethoxysilane,
tetrapenta-iso-propoxysilane, tetrapenta-n-propoxysilane,
tetrapenta-n-butoxysilane, tetrapenta-sec-butoxysilane,
tetrapenta-tert-butoxysilane, methyltriethoxysilane,
methyltripropoxysilane, methyltributoxysilane,
dimethyldimethoxysilane, dimethyldiethoxysilane,
dimethylethoxysilane, dimethylmethoxysilane, dimethylpropoxysilane,
dimethylbutoxysilane, methyldimethoxysilane, methyldiethoxysilane,
and hexyltrimethoxysilane.
[0058] A second type of organosilicon compounds usable in
combination with the ionizing radiation-curable resin composition
is a silane coupling agent.
[0059] Specific examples of silane coupling agents usable herein
include .gamma.-(2-aminoethyl)aminopropyltrimethoxysilane,
.gamma.-(2-aminoethyl)aminopropylmethyldimethoxysilane,
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
.gamma.-aminopropyltriethoxysilane,
.gamma.-methacryloxypropylmethoxysilane,
N-.beta.-(N-vinylbenzylaminoethyl)-.gamma.-aminopropylmethoxysilane
hydrochloride, .gamma.-glycidoxypropyltrimethoxysilane,
aminosilane, methylmethoxysilane, vinyltriacetoxysilane,
.gamma.-mercaptopropyltrimethoxysilane,
.gamma.-chloropropyltrimethoxysilane, hexamethyldisilazane,
vinyltris(.beta.-methoxyethoxy)silane, octadecyldimethyl
[3-(trimethoxysilyl) propyl] ammonium chloride,
methyltrichlorosilane, and dimethyldichlorosilane.
[0060] A third type of organosilicon compounds usable in
combination with the ionizing radiation-curable resin composition
is an ionizing radiation-curable silicon compound.
[0061] Specific examples of ionizing radiation curing silicon
compounds usable herein include organosilicon compounds, containing
a plurality of functional groups capable of being reaction
crosslinked upon exposure to an ionizing radiation, for example,
polymerizable double bond groups, having a molecular weight of not
more than 5,000. More specifically, this type of organosilicon
compounds include polysilanes terminated on one end with a vinyl
functional group, polysilanes terminated on both ends with a vinyl
functional group, polysiloxanes terminated on one end with a vinyl
functional group, polysiloxanes terminated on both ends with a
vinyl functional group, and vinyl-functional polysilanes or
vinyl-functional polysiloxanes obtained by reacting these
compounds. Specific examples of reactive organosilicon compounds
usable herein include the following compounds. ##STR1##
[0062] In formulae (a) to (e), R.sup.1and R.sup.2 each
independently represent an alkyl group having 1 to 4 carbon atoms,
and a to d and n are each such a number as will bring the molecular
weight of the compound to not more than 5,000.
[0063] Other organosilicon compounds usable in combination with the
ionizing radiation-curable resin composition include
(meth)acryloxysilane compounds, such as
3-(meth)acryloxypropyltrimethoxysilane and
3-(meth)acryloxypropylmethyldimethoxysilane.
[0064] Shapes of fine concaves and convexes 2 at a pitch of not
more than the wavelength of light formed on the top of the
transparent layer 3 include: a shape as illustrated in FIGS. 1 and
2A wherein the fine concaves and convexes 2 at the upper edge of
section are in a sine curve form; and shapes wherein the fine
concaves and convexes 2 at the upper edge of section are in a form
other than the sine curve form, for example, a shape as illustrated
in FIG. 2B wherein the section in its apex 2a is in an arc form, a
rise portion 2b is linear, and the convex is tapered off to a
point, a triangular wave shape as illustrated in FIG. 2C, and a
rectangular wave shape as illustrated in FIG. 2D.
[0065] Among them, the profiles as shown in FIGS. 2A, 2B, and 2C,
wherein the depth varies from place to place, are preferred, and
when these profiles are used, the light refractive index varies
according to the position in the thicknesswise direction of the
transparent layer 3.
[0066] In the case of the profile shown in FIG. 2D among these
profiles, the area of the horizontal cut surface does not vary in
any height portion, and, hence, the proportion of the transparent
layer 3 is the same and the light refractive index in the upper
portion of the wave is identical to that in the lower portion of
the wave. A layer having a constant and predetermined refractive
index may be formed by fixing the pitch and the width of the
wave.
[0067] In addition, the shape as shown in FIG. 2E, wherein the
convex is not tapered off to a point, is also possible. This shape,
however, is unfavorable because, in the production of the shape
using a mold, the separation from the mold is difficult.
[0068] In the transparent layer 3 having the above profile, the
fine concaves and convexes may be arranged so that, as viewed from
the side of the concave-convex portion 2, when attention is given
to concaves, as shown in FIG. 3A (perspective view), parallel
grooves 5 (parallel partitions 6 when attention is given to
convexes) are provided, or so that, as shown in FIG. 3B or 3C (as
viewed from the top), the fine concaves and convexes are arranged
in a planar form (wherein the concentric circles represent contour
lines).
[0069] All the above types have antireflection properties. The
groove type as shown in FIG. 3A, however, has directional
properties, and, thus, the reflectance may vary according to the
direction of incident light. On the other hand, the
two-dimensionally arranged type as shown in FIG. 3B or 3C is
substantially free from directional properties and thus is
preferred.
[0070] Although there are a wide variety of shapes in the
concave-convex portion 2, the pitch (=cycle) of waves in concaves
and convexes, which appear in the profile, is very small and is not
more than the wavelength of light, preferably not more than 300 nm.
Although there is no particular lower limit of the pitch, the pitch
is preferably not less than 100 nm when the accuracy of the mold is
taken into consideration.
[0071] When the difference of elevation in the waves of the
concave-convex portion is larger, the reflectance is lower and the
antireflective effect is better. For this reason, the difference of
elevation is preferably not less than 100 nm. Although there is no
particular upper limit of the difference of elevation, when the
pitch is usually assumed to be 200 to 300 nm, the difference of
elevation is preferably about 50 to 200% of the pitch value, that
is, about 100 to 600 nm.
[0072] The concave-convex portion of fine concaves and convexes may
be formed using the ionizing radiation-curable resin composition on
the top surface of the transparent layer 3, for example, by a
method wherein, in the formation of the transparent layer 3 by
coating, the coating is covered with an embossing film having
concaves and convexes and, in this state, the coating is cured, a
method wherein embossing means, such as embossing roll, pressed
against the coating while optional heating, or a method wherein a
transfer film, from which a transparent layer 3 can be transferred,
is prepared by coating on a releasable substrate having concaves
and convexes on its releasable face and the transparent layer 3 is
then transferred using the transfer film.
[0073] A more preferred method for forming the concave-convex
portion is as follows.
[0074] At the outset, an assembly of a photosensitive resin stacked
on a suitable substrate is provided, and is exposed by laser beam
interference. In this case, a photosensitive material, provided
with a film, commercially available as a photosensitive material
for the production of relief holograms may be utilized. The
exposure is carried out by interference of two or more divided
larger beams. Thus, cured portions and uncured portions are formed
at a pitch of not more than the wavelength of light. After the
exposure, development is carried out by a method according to the
type of the photosensitive resin, usually by a method wherein
uncured portions are removed by a specific solvent, thereby
preparing an original mold having a concave-convex surface of
innumerable fine concaves and convexes at a pitch of not more than
the wavelength of light.
[0075] The original mold is formed of a polymer having a relatively
low molecular weight from the viewpoint of facilitating the
formation of the concaves and convexes, and thus has unsatisfactory
solvent resistance. In addition, this original mold is fragile.
Therefore, the repetition of replication using this original mold a
large number of times is not favorable.
[0076] To overcome this problem, a method is preferably adopted
wherein the original mold is plated with a metal such as nickel to
prepare a first metallic mold which may be then used for
replication. Alternatively, the first metallic mold is further
plated to prepare several second metallic molds which are then used
for replication. These metallic molds are in many cases called
metallic stampers.
[0077] More preferably, use is made of a mold roll wherein the
shape of the mold surface thus obtained has been formed on a roll
surface and, if necessary, this has been brought to a composer form
(multi-side attachment on an identical plate surface), or a mold
roll wherein the shape of the mold surface has been continuously
formed in a roll face direction and a circumferential
direction.
[0078] In the replication of the shape of the mold surface, the
shape of the original mold is the same as the shape of the second
metallic mold, while the shape of the original mold is reverse to
that of the first metallic mold. Further, the shape of fine
concaves and convexes in the antireflection film is reverse to the
shape of fine concaves and convexes on the surface in the mold for
the production of the antireflection film. Therefore, in order to
provide a desired shape as the antireflection film, if necessary,
the shape of the fine concaves and convexes may be reversed in
addition to the formation of the metal mold using plating. In this
case, however, when the profile of the fine concaves and convexes
is, for example, a sine curve form, there is an exceptional case
where the original shape is not different from the reverse shape of
the mold.
[0079] In the following description, except for the above
exceptional case, the shape of fine concaves and convexes on the
surface of the mold is assumed to be reverse to the desired shape
of fine concaves and convexes in an antireflection film.
[0080] FIG. 4 illustrates the production of an antireflection film
in a continuous manner by means of an apparatus 10 using a mold
roll.
[0081] In FIG. 4, the transparent substrate film 1 is unwound from
above on the left in the drawing, is guided between the nip roll
11a and the mold roll 12, is traveled halfway round the mold roll
12 on its upper side, is passed through between the mold roll 12
and a nip roll 11b, and is then discharged toward the right
side.
[0082] The mold roll 12 is driven so as to rotate clockwise as
indicated by an arrow within the mold roll 12. The nip rolls 11a
and 11b are free-run according to the rotation of the mold roll
(the nip rolls 11a and 11b are rotated as indicated by respective
arrows within the rolls). A brake is installed on the unwinding
side of the transparent substrate film 1, and the tension during
travel can be regulated by the brake together with a winding motor
provided on the discharge side of the transparent substrate film 1.
Further, the tension is kept constant between both the nip rollers
11a and 11b.
[0083] A die head 13 is installed just under the mold roll 12. The
die head 13 is constructed so that a liquid reservoir 14 is
provided in its interior, a slit 15 is provided in its upper part,
and an ionizing radiation-curable resin composition 17 is
externally fed through a pipe 16.
[0084] A necessary amount of the ionizing radiation-curable resin
composition 17 is extruded upward from the slit 15 according to the
travel of the transparent substrate film 1, is coated on the
surface of the mold roll, and is also filled into concaves 12a in
the mold roll 12, and, when the ionizing radiation-curable resin
composition 17 is passed through between the nip roll 11a and the
mold roll, the coverage is regulated.
[0085] An ionizing radiation exposure system 18 is installed above
the mold roll 12. When the transparent substrate film is passed
under the exposure system 18, an ionizing radiation is applied to
crosslink and cure the ionizing radiation-curable resin composition
on the transparent substrate film 1, whereby the transparent layer
3 is adhered to the transparent substrate film 1.
[0086] Thereafter, the cured transparent layer 3, together with the
transparent substrate film, is wound.
[0087] When the transparent substrate film 1 is laminated, at least
the concaves 12a on the surface of the mold roll are filled with
the ionizing radiation-curable resin composition, and, in this
case, the contact of the transparent substrate film with the
exposed surface of the ionizing radiation-curable resin composition
filling the concaves 12a suffices for contemplated results. On the
other hand, when the transparent substrate film is not used, the
ionizing radiation-curable resin composition is preferably applied
in an amount large enough for the ionizing radiation-curable resin
composition to form a continuous film on the surface of the
mold.
[0088] In the embodiment shown in the drawing, the ionizing
radiation-curable resin composition is applied onto the mold roll
12, and this is preferred. However, when the inclusion of air
bubbles at the time of lamination can be prevented, a method may be
used wherein the ionizing radiation-curable resin composition is
applied on the transparent substrate film 1 side followed by
contact with the mold roll 12.
[0089] After the ionizing radiation-curable resin composition is
coated on the surface of the mold roll 12, if necessary, a doctor
ring may be applied.
[0090] In the above embodiment, ultraviolet light or electron beam
is generally used as the ionizing radiation. However, other
ionizing radiation may be used. The number of exposure system
disposition sites is not limited to one above the mold roll 12, and
a desired number of ionizing radiation exposure systems may be
installed at any sites between just after coating and the passage
through the nip roll 11b. When a satisfactory space cannot be
ensured around the mold roll 12, an ionizing radiation exposure
system may be further installed at a position after the nip roll
11b to further apply the ionizing radiation.
[0091] Curing of the ionizing radiation-curable resin composition
17 by the application of the ionizing radiation creates adhesion
between the cured product of the ionizing radiation-curable resin
composition 17 and the transparent substrate film 1. Therefore,
after the curing, the separation of the cured product of the
ionizing radiation-curable resin composition 17 together with the
transparent substrate film 1 can provide an antireflection film
wherein a transparent layer 3 formed of a cured product of the
ionizing radiation-curable resin composition is stacked on the
transparent substrate film land fine concaves and convexes, which
reflect the shape of fine concaves and convexes of the mold
surface, are provided on the surface of the transparent layer
3.
[0092] When the production of an antireflection film not provided
with the transparent substrate film is contemplated, a method may
be adopted wherein the lamination of the transparent substrate film
is omitted. Alternatively, an antireflection film not provided with
the transparent substrate film 1 may be produced by a method
wherein the separability is imparted to the transparent substrate
film 1 on its surface to be coated with the ionizing
radiation-curable resin composition and the transparent substrate
film 1 is separated simultaneously with the separation of the
transparent layer from the mold surface, only the transparent
substrate film 1 is first separated followed by separation of the
transparent layer 3, or the transparent layer 3 together with the
transparent substrate film 1 is first separated followed by
separation of the transparent substrate film 1. The use of the
transparent substrate film 1 during the process is preferred
because the thickness of the transparent layer 3 can be easily
regulated and the influence of dust in the air can also be
avoided.
[0093] The antireflection film 1 according to the present
invention, even in such a state that the fine concaves and convexes
2 are exposed on the surface, can exhibit satisfactory effect.
Preferably, however, a layer 4 formed using a resin composition
having a lower light refractive index than the transparent layer 3
is stacked on the fine concaves and convexes 2 from the viewpoint
of preventing scratching or staining caused by accidental
contact.
[0094] The formation of the layer 4 from a fluororesin or a
silicone resin is preferred because the light refractive index is
1.3 to 1.4 which is generally lower than the refractive index of
the transparent layer 3 formed of a cured product of the ionizing
radiation-curable resin composition (that is, a cured product of
acrylate resin composition which has a light refractive index of
not less than 1.5). Further, this is also preferred from the
viewpoint of a contact angle between the material and water of not
less than 100 degrees which indicates that antifouling properties
can also be provided.
[0095] When the necessity of imparting a special function to the
layer 4 is not very high due to the use of the fluororesin,
silicone resin or the like, the layer 4 may be formed of a
thermoplastic resin, other than the fluororesin and silicone resin,
which is selected in consideration of the adhesion of the
underlying transparent layer 3.
[0096] The above material may be applied by a dry process, such as
vapor deposition, or a wet process, such as conventional coating. A
method may also be adopted wherein the material is previously
coated on the mold surface for imparting fine concaves and convexes
to the transparent layer 3 and the ionizing radiation-curable resin
composition is applied on the coating, whereby the layer 4 is
stacked.
[0097] When a transparent layer is formed from a mixture of the
fluororesin or silicone resin with the ionizing radiation-curable
resin composition for the transparent layer 3, the fluororesin or
the silicone resin may be bled out.
[0098] In the antireflection film according to the present
invention, in addition to the above construction, treatment may be
carried out including antistatic treatment for preventing the
deposition of dust during the use of the antireflection film or
tackiness-imparting treatment on the antireflection film in its
side remote from the fine concaves and convexes 2 from the
viewpoint of the convenience of the application of the
antireflection film.
[0099] Specifically, the antistatic treatment may be carried out by
applying an antistatic agent or conductive fine particles. When the
transparent layer 3 or the surface layer 4 is formed by coating,
the antistatic agent or conductive fine particles may be mixed into
the coating composition used followed by the application of the
coating composition.
[0100] Alternatively, the antistatic treatment may be carried out
by coating the antistatic agent per se on the transparent layer
3.
[0101] Further, the antistatic treatment may be carried out by
forming a conductive layer, using a coating composition containing
conductive fine particles, or a thin layer of a metal oxide under
the transparent layer 3 or between the substrate film 1 and the
transparent layer 3 when the transparent substrate film 1 is
used.
[0102] The tackiness-imparting treatment may be carried out by
directly coating a polyacrylic ester or a rubber pressure-sensitive
adhesive. In general, a release paper with a pressure-sensitive
adhesive coated thereon is laminated, and the release paper is
allowed to remain unseparated until use from the viewpoint of
avoiding accidental adhesion or deposition of dust due to the
exposure of the pressure-sensitive adhesive.
[0103] The thickness of the pressure-sensitive adhesive layer is
preferably about 20 to 40 Wm.
[0104] The antireflection film according to the present invention,
as shown in FIGS. 5 and 6, is in many cases used in applications
related to displays.
[0105] FIG. 5 is a cross-sectional view showing an embodiment of
the application of the antireflection film to a polarizing plate.
In this case, an antireflection film 21 is stacked on the top
surface of a polarizing plate 22 having a three-layer structure of
a surface layer 22a, a polarizing layer 22b, and a backside layer
22a' stacked in that order on top of one another to provide an
antireflective polarizing element 20.
[0106] In this case, a construction may be adopted wherein the
surface layer 22a is provided as the substrate and a transparent
layer 3 stacked directly on the substrate. However, the stacking of
the antireflection film subjected to the above tackiness-imparting
treatment onto the polarizing plate 22 having the above three-layer
structure is convenient from the practical point of view.
[0107] The antireflective polarizing plate comprising the
antireflection film 21 stacked on the top surface of the polarizing
plate 22 is very usefully applied onto liquid-crystal displays.
[0108] In FIG. 6, the antireflective polarizing plate 20 is stacked
onto the top surface (=viewer side face) of a liquid-crystal panel
23 comprising a liquid crystal sandwiched between two glass plates
which have a transparent electrode in their inner surface and face
each other so that the antireflective polarizing plate 20 on its
antireflection film 21 side faces outward. In general, a polarizing
plate 22 is stacked on the underside of the liquid-crystal panel
23.
[0109] According to the above construction, the reflection of
external light from the surface of the liquid-crystal display is
prevented. Therefore, even under an environment such that external
light, such as illumination or sunlight, cannot be avoided, there
is no possibility that the external light is reflected and
consequently the visibility of the display contents of the
liquid-crystal display is lowered.
[0110] In addition, the antireflection film according to the
present invention, when stacked on the surface of displays, such as
CRT (cathode-ray tube) displays or plasma displays, or disposed on
the viewer side, can inhibit the reflection of external light from
the surface of the displays to prevent a lowering invisibility of
display images.
[0111] Further, the antireflection film according to the present
invention, when applied onto the surface of building materials of
metals or glass or those having other gloss surface, can prevent
accidental light reflection. This can eliminate the influence of
reflection on the way of vehicles and pedestrians, and, at the same
time, can prevent a reduction in visibility of the appearance
inherent in them.
EXAMPLES
Example 1
[0112] A photosensitive resin was coated by a spinner onto a glass
substrate with a diameter of 76 mm to prepare a photosensitive
material. The photosensitive material was exposed by means of a
laser interference exposure system using an argon laser (wavelength
351 nm) at an angle of incidence of 40 degrees from three
directions. After the exposure, solvent development was carried out
to prepare an original mold having fine concaves and convexes
arranged lengthwise and breadthwise on a cured product of the
photosensitive resin.
[0113] The pitch of concaves and convexes on the original mold was
280 nm, and the difference in level between concaves and convexes
was 200 to 250 nm.
[0114] The surface of the original mold was electrolessly plated,
followed by plating with nickel to prepare a 100 .mu.m-thick
duplicate mold. This procedure was repeated to prepare duplicate
molds. A large mold having a width of 500 mm and a length of 980 mm
was prepared by multi-side attachment of the duplicate molds thus
obtained.
[0115] This large mold was applied to a roll with a diameter of 300
nm (circumference 980 nm) to prepare a mold roll.
[0116] In this case, when the spacing of the seam is not less than
1 mm, an ionizing radiation-curable resin composition is filled
into the gap, and this makes it difficult to separate a cured
product of the ionizing radiation-curable resin composition from
the mold. In order to prevent this unfavorable phenomenon, welding
was carried out to fill the gap with the mold.
[0117] An acrylate ultraviolet-curable resin (stock number Z 9009,
manufactured by Japan Synthetic Rubber Co., Ltd.; light refractive
index after curing 1.59) was provided. In this case, the viscosity
of the acrylate ultraviolet-curable resin was regulated to a value
between 100 to 2000 cps by temperature control from the viewpoints
of degassing and the reproduction of the mold shape. An
easy-adhesion polyester resin film (A 4300, manufactured by Toyobo
Co., Ltd.; thickness 125 .mu.m) was provided as a transparent
substrate film. Using the apparatus described above with reference
to FIG. 4, the ultraviolet-curable resin was coated onto the mold
roll, and a transparent substrate film was laminated onto the
coating. Ultraviolet light was then applied to the
ultraviolet-curable resin to cure the ultraviolet-curable resin.
The cured product, together with the transparent substrate film,
was separated from the mold roll. Thus, an antireflection film was
prepared which comprised fine concaves and convexes provided on the
surface of the cured film of the ultraviolet-curable resin.
Example 2
[0118] A fluororesin-based surface coating liquid was coated by
dipping on fine concaves and convexes on the cured film in the
antireflection film prepared in Example 1. The coating was then
dried to prepare an antireflection film.
[0119] Fingerprints were applied onto the surface of this
antireflection film, and the surface of the antireflection film was
then wiped with cotton. As a result, the fingerprints could be
wiped off.
Example 3
[0120] An antireflection film was prepared in the same manner as in
Example 1, except that a coating composition (an ATO ultrafine
particles coating composition, manufactured by Shinto Paint Co.,
Ltd.) containing ultrafine particles of ATO (antimony-dopedindium
tin oxide) was coated onto the easy-adhesion polyester resin film
as used in Example 1.
Comparative Example
[0121] The mold roll prepared in Example 1 was provided as an
embossing plate. Concaves and convexes were formed by heat
embossing on a polycarbonate resin film (thickness 130 .mu.m) using
this mold roll. Thus, an antireflection film was prepared.
[0122] The antireflection films prepared in Examples 1 to 3 and the
comparative example were measured for the average reflectance, the
pencil hardness, and the charge decay. The results are shown in
Table 1.
[0123] The average reflectance was measured in the wavelength range
of 380 to 780 nm with MPC-3100 manufactured by Shimadzu Seisakusho
Co., Ltd. The pencil hardness was measured with a pencil hardness
tester EP-001 manufactured by Rigaku Kogyo. The charge decay was
measured with a static honestmeter Type H-0110 manufactured by
SHISHIDO ELECTROSTATIC, LTD. TABLE-US-00001 TABLE 1 Average Pencil
hardness (as measured Charge reflectance according to JIS K 5400)
decay Ex. 1 0.5% H -- Ex. 2 0.5% H -- Ex. 3 1.3% H 4 sec Comp. Ex.
6% B --
[0124] According to the present invention, the adoption of a
structure comprising a transparent layer, formed of a cured product
of an ionizing radiation-curable resin composition, and, provided
on the surface of the transparent layer, a concave-convex portion
with innumerable fine concaves and convexes at a pitch of not more
than the wavelength of light can provide an antireflection film
which can be easily produced by molding in a short time and, does
not involve a corrosion problem, and has an even reflectance in a
visible light region.
[0125] According to the second embodiment of the present invention,
an antireflection film can be provided which, by virtue of backing
of the transparent layer with a transparent substrate film, has
advantages of higher strength and better flatness, in addition to
the effect of the present invention.
[0126] According to the third embodiment of the present invention,
an antireflection film can be provided which has advantages of a
high surface pencil hardness of not less than H and in its turn
less susceptibility to scratching, in addition to the effects of
the first or second embodiment of the present invention.
[0127] According to the fourth embodiment of the present invention,
an antireflection film can be provided which, by virtue of stacking
of a layer having a lower refractive index than the transparent
layer on the surface, has an advantage of excellent fastness
properties and stain resistance of the surface, in addition to the
above effects.
[0128] According to the fifth embodiment of the present invention,
an antireflection film can be provided which, by virtue of
antistatic properties imparted to the antireflection film, has an
advantage of no significant deposition of dust, in addition to the
effects of any one of the above embodiments of the present
invention.
[0129] According to the sixth embodiment of the present invention,
a polarizing element can be provided wherein the effects of the
antireflection film of the present invention have been added to a
polarizing plate.
[0130] According to the seventh embodiment of the present
invention, a display device can be provided which additionally has
the effects of the antireflection film as defined in any one of
claims 1 to 5 according to the present invention and the effects of
the polarizing element.
[0131] According to the eighth embodiment of the present invention,
an antireflection film can be produced by a very efficient process
wherein an ionizing radiation-curable resin composition is shaped
by means of a mold, and the shape is then cured by the application
of an ionizing radiation.
[0132] According to the ninth embodiment of the present invention,
by virtue of the use of a separable transparent substrate film, in
addition to the above effect of the present invention, an
additional advantage can be attained such that an antireflection
film consisting of a transparent layer alone can be efficiently
produced.
[0133] According to the tenth embodiment of the present invention,
in addition to the above effect of the present invention, an
additional advantage can be attained such that an antireflection
film comprising a stack of a transparent substrate film and a
transparent layer and having higher strength and better flatness
can be efficiently produced.
[0134] According to the eleventh embodiment of the present
invention, in addition to the above effect of the present
invention, an antireflection film having desired properties can be
accurately and stably produced by an established process.
* * * * *