JP2003075638A - Polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the display quality (especially gray scale characteristics) of a VA (Vertical Alignment) mode liquid crystal display device. SOLUTION: A polarizing plate consisting of a polarizing film and two transparent protective films disposed on both sides thereof is used. One of the transparent protective films is an optical retardation film with 20 to 70 nm Re retardation value and 150 to 400 nm Rth retardation value. The slow axis of the optical retardation film and the transmission axis of the polarizing film are placed so as to be practically in parallel with each other. The other transparent protective film has a light diffusing function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate capable of improving the viewing angle dependence of a liquid crystal display device, particularly the gradation characteristic depending on the viewing angle. The present invention also relates to a VA mode liquid crystal display device having a wide viewing angle.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device (LCD: Liquid Crystal Display) using an active matrix, a liquid crystal material having a positive dielectric constant anisotropy is horizontally disposed on a substrate surface and between opposing substrates. A liquid crystal display device of TN (Twisted Nematic) mode, which is oriented so that it is twisted by 90 degrees, is widely used. However, the TN-mode liquid crystal display device has a serious problem of poor viewing angle characteristics, and various studies have been made to improve the viewing angle characteristics. On the other hand, as a method to replace the TN mode,
A liquid crystal material having negative dielectric anisotropy is vertically aligned, and a protrusion provided on the substrate surface regulates the tilt direction of liquid crystal molecules when a voltage is applied.
An ent) type liquid crystal display device has been proposed and has succeeded in greatly improving the viewing angle characteristics.

In the MVA type liquid crystal display device, a VA (Vert) for vertically aligning a liquid crystal material having a negative dielectric anisotropy is used.
Improve the viewing angle characteristics by providing protrusions on the substrate in the liquid crystal display device of the (ically Aligned) mode so that the directions in which liquid crystal molecules are obliquely aligned when a voltage is applied are set in multiple directions within one pixel. We succeeded in significantly improving the viewing angle characteristics. However, the liquid crystal display device using the conventional MVA method has a problem in that the gradation characteristics are deteriorated depending on the viewing angle. In particular,
If the viewing angle is tilted in the up, down, left, and right directions, the gradation interval on the high-luminance side becomes small, and the gradation cannot be displayed well.

To solve this problem, Japanese Patent Laid-Open No. 2001-3378
It is shown that the display quality is improved by using a light diffusing means having a highly controlled lens structure or a diffractive structure as described in Japanese Patent No. 3 and 2001-54661. However, these concrete means are
There was a problem that it was expensive and mass production was very difficult. On the other hand, regarding the light diffusing means which is inexpensive and can be mass-produced, for example, JP-A-6-18706 and 10-
As disclosed in Japanese Patent Publication No. 20103, one formed by applying a resin containing a filler such as silicon dioxide (silica) on the surface of a transparent base film, JP-A-11-
160505, JP-A-11-305010, JP-A-11-326608, JP-A-2000-
As described in JP-A-121809, JP-A-2000-180611, and JP-A-2000-338310, those using a light diffusion layer containing a transparent resin and transparent fine particles can be mentioned.

[0005]

In the prior art, VA is used.
Although a modest viewing angle improving effect is recognized for the mode liquid crystal display device, only a practically unsatisfactory effect is obtained.

An object of the present invention is to provide a polarizing plate capable of remarkably improving the display quality (particularly the gradation characteristic) of a VA mode liquid crystal display device. It is also an object of the present invention to significantly improve the display quality (particularly the gradation characteristics) of the VA mode, which is a wide viewing angle liquid crystal display device, by using the light scattering layer.

[0007]

The object of the present invention has been achieved by the following polarizing plates (1) to (11) and the following liquid crystal display device (12). (1) A polarizing plate comprising a polarizing film and two transparent protective films arranged on both sides thereof, wherein one transparent protective film is 2
A retardation film having a Re retardation value of 0 to 70 nm and an Rth retardation value of 150 to 400 nm, wherein the slow axis of the retardation film and the transmission axis of the polarizing film are substantially parallel to each other. Has been placed,
Then, the other transparent protective film has a light diffusing function.

(2) The retardation film has an acetylation degree of 59.
The polarizing plate according to (1), which comprises 0 to 61.5% cellulose acetate. (3) The retardation film is made of cellulose acetate 100
The polarizing plate according to (2), which contains 0.01 to 20 parts by mass of an aromatic compound having at least two aromatic rings with respect to parts by mass.

(4) The transparent protective film having a light diffusion function is
The polarizing plate according to (1), which comprises a transparent support and a light diffusion layer containing translucent fine particles in a translucent resin. (5) The polarizing plate according to (4), wherein the difference between the refractive index of the transparent fine particles and the refractive index of the transparent resin is 0.02 or more and 0.15 or less. (6) The polarizing plate according to (5), wherein the transparent fine particles have a particle size distribution having at least two peaks. (7) One peak of the particle size distribution of translucent fine particles is 0.5
To 2.0 μm, and another peak is 2.
The polarizing plate according to (6), which is in the range of 5 to 5.0 nm.

(8) The transparent protective film having a light diffusion function is
The polarizing plate according to (1), which has a haze value of 40% or more. (9) The polarizing plate according to (1), wherein a low refractive index layer having a refractive index of 1.35 to 1.45 is provided on the transparent protective film having a light diffusing function. (10) The polarizing plate according to (9), wherein the low refractive index layer comprises a crosslinked cured product of a composition containing a fluorine-containing compound and inorganic fine particles, which is cured by heat or ionizing radiation. (11) The polarizing plate according to (9), wherein the low refractive index layer has an integrated sphere average reflectance of 2.5% or less in the wavelength range of 450 to 650 nm.

(12) A VA-mode liquid crystal cell and two polarizing plates arranged on both sides of the cell, wherein the two polarizing plates are respectively a polarizing film and two transparent protective films arranged on both sides thereof. In the liquid crystal display device, the transparent protective film between the polarizing film on the display surface side and the liquid crystal cell is 20 to 7
Re retardation value of 0 nm and 150 to 400 n
A retardation film having an Rth retardation value of m, wherein the slow axis of the retardation film and the transmission axis of the polarizing film on the display surface side are arranged substantially parallel to each other, and A liquid crystal display device, wherein a transparent protective film provided closest to the display surface side has a light diffusion function.

In the present specification, the Re retardation value is a value defined by the following formula (I), and the Rth retardation value is a value defined by the following formula (II): (I ) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d [where nx is the refractive index in the slow axis direction in the film plane; ny is Is the refractive index in the fast axis direction in the film plane; nz is the refractive index in the thickness direction of the film; and d is the film thickness].

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION [Basic Structure of Liquid Crystal Display Device] When the polarizing plate according to the present invention is used in a transmissive liquid crystal display device, particularly in a VA mode transmissive display device, a remarkable effect can be obtained. The transmissive liquid crystal display device includes a liquid crystal cell and two polarizing plates arranged on both sides of the liquid crystal cell. The liquid crystal cell carries liquid crystal between two electrode substrates.

In the VA mode liquid crystal cell, rod-shaped liquid crystal molecules are aligned substantially vertically when no voltage is applied. VA
The mode liquid crystal cell includes (1) a VA mode liquid crystal cell in a narrow sense in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied and are aligned substantially horizontally when voltage is applied (Japanese Patent Application Laid-Open No. 2-176625). (2) In order to widen the viewing angle, the VA mode is multi-domain (M
VA mode liquid crystal cell (SID97, Digest of tec)
h. Papers (Proceedings) 28 (1997) 845),
(3) A liquid crystal cell of a mode (n-ASM mode) in which rod-shaped liquid crystal molecules are substantially vertically aligned when no voltage is applied and twisted in a multi-domain alignment when a voltage is applied (Proceedings of Japan Liquid Crystal Conference 58-59 (1998). ))) And (4) SURVAIVAL mode liquid crystal cell (announced at LCD International 98).

FIG. 1 is a graph showing the gradation characteristics in the horizontal direction in a commercially available MVA mode liquid crystal display device. Figure 1
In the liquid crystal display device shown in (1), the gradation on the high brightness side (L7, L8) converges at a viewing angle of about 50 °, and the gradation characteristics (the viewing angle dependence of the brightness (brightness) in the voltage for displaying each gradation). Becomes worse. Therefore, when the display image is viewed from the direction of 50 °, a high-luminance image such as an X-ray image cannot be displayed accurately. The angle at which deterioration of gradation characteristics is a problem for practical use is 20 °. 2 on the high brightness side (L7, L8)
The gradation characteristic at 0 ° is preferably 40 ° or more, more preferably 50 ° or more, and most preferably 60 ° or more.

The polarizing plate comprises a polarizing film and two transparent protective films disposed on both sides of the polarizing film. In the present invention, for at least the polarizing plate on the display surface side, a transparent protective film having a function as a retardation film and a transparent protective film having a function as a light diffusion film are used in combination to function as a light diffusion film. The transparent protective film having is disposed so as to be closest to the display surface side. For the polarizing plate on the side opposite to the display surface (usually on the backlight side), a transparent protective film having a function as a retardation film can be used as a transparent protective film on the liquid crystal cell side. However, the transparent protective film having a function as a light diffusion film is not necessary in the polarizing plate on the side opposite to the display surface.

FIG. 2 is a schematic sectional view showing a typical embodiment of the liquid crystal display device according to the present invention. The liquid crystal display device shown in FIG. 2A includes a transparent protective film (1), a polarizing film (2), a transparent protective film (3p) having a function as a retardation film, in order from the backlight (BL) side. It comprises a VA mode liquid crystal cell (4), a transparent protective film (5p) having a function as a retardation film, a polarizing film (6), and a transparent protective film (7d) having a function as a light diffusion film. Transparent protective film having a function as a retardation film (5
p), the polarizing film (6) and the transparent protective film (7d) having a function as a light diffusion film constitute a polarizing plate according to the present invention.

The liquid crystal display device shown in FIG. 2B has a transparent protective film (1), a polarizing film (2), a transparent protective film (3), and a VA mode liquid crystal cell in order from the backlight (BL) side. (4), a transparent protective film (5p) having a function as a retardation film, a polarizing film (6), and a transparent protective film (7d) having a function as a light diffusing film. The transparent protective film (5p) having a function as a retardation film, the polarizing film (6) and the transparent protective film (7d) having a function as a light diffusion film constitute a polarizing plate according to the present invention.

The transparent protective film having a function as a retardation film may be formed by laminating a retardation film on an ordinary transparent protective film. However, it is preferable to impart a function as a retardation film to the transparent protective film itself. The transparent protective film having a function as a light diffusing film can impart the function as a light diffusing film to the transparent protective film itself. However, it is preferable to stack a light diffusion film (light diffusion layer) on an ordinary transparent protective film (which functions as a transparent support).

[Transparent Protective Film Having Function as Light-Diffusing Film] The light-diffusing film is a film that refracts and scatters light. Specifically, a microlens film with minute lenses formed, a lenticular film, a film with fine particles mixed therein, a diffusion film with a randomly roughened surface, an internal refractive index distribution film, or a diffraction grating layer is used. can do. The film containing fine particles can be preferably used as a light diffusion film that can be mass-produced at low cost. It is particularly preferable that the transparent protective film having a light diffusing function is composed of a transparent support and a light diffusing layer (light diffusing film) containing translucent fine particles in a light transmissive resin.

FIG. 3 is a schematic sectional view showing a typical form of a transparent protective film having a light diffusing function. The transparent protective film (10) shown in FIG. 3 comprises a transparent support (20) and a light diffusion layer (30) containing transparent particles (41, 42) in a transparent resin (31). It becomes. The light diffusion layer (3
0) includes the first light-transmissive fine particles (41) and the second light-transmissive fine particles (42) having two kinds of peaks of different particle diameter distributions (different in refractive index). One type of translucent fine particles may be used. Further, translucent fine particles having the same kind (having the same refractive index) and two peaks of the particle size distribution may be used for the light diffusion layer.

The first transparent fine particles (41) are composed of a transparent resin (eg silica, refractive index: 1.51) (average particle diameter 1.0 μm). The second transparent fine particles (42) are composed of another transparent resin (for example, styrene, refractive index: 1.61) (average particle diameter 3.5).
μm). The light diffusion function is obtained by the difference in the refractive index between the translucent fine particles (41, 42) and the translucent resin (31).
The difference in refractive index is preferably 0.02 to 0.15. When the difference in refractive index is less than 0.02, the light diffusion effect may not be obtained. When the refractive index difference is larger than 0.15, the light diffusivity is too high, and the entire film may be whitened. The difference in refractive index is more preferably 0.03 to 0.13, and is currently preferably 0.04 to 0.10.

It is preferable that one peak of the particle size distribution of the transparent fine particles is in the range of 0.5 to 2.0 μm, and the other peak is in the range of 2.5 to 5.0 nm. Such a particle size distribution can be easily achieved by mixing two types of fine particle groups having different most frequent particle sizes.
With the peak in the range of 0.5 to 2.0 μm (in FIG. 3, the most frequent particle diameter of the translucent fine particles (41)), an appropriate light scattering angle distribution as a light diffusion film can be obtained.
In the light diffusion film, it is necessary to diffuse the incident light to some extent in order to improve the display quality (improve the downward viewing angle). The greater the diffusion effect, the better the viewing angle characteristics. However, in order to maintain the front brightness in terms of display quality, it is necessary to increase the transmittance as much as possible. By setting the particle size peak to 0.1 μm or more, backscattering can be reduced and the decrease in brightness can be suppressed. The particle size peak is 2.0 μm.
By the following, a large scattering effect is obtained and the viewing angle characteristics are improved. This peak is 0.3 to 1.8 μm
The range of 0.4 to 1.6 is more preferable.
Most preferably, it is in the range of μm.

Due to the peak in the range of 2.5 to 5.0 μm (in FIG. 3, the most frequent particle diameter of the transparent fine particles (42)),
Suitable surface scattering can be obtained as a light diffusion film. In the light diffusion film, in order to improve the display quality,
It is also important to prevent the reflection of external light by appropriate surface scattering. As described above, the most frequent (mode) particle size (rather than the average particle size) is more important as the particle size of the fine particles. In this specification, the most frequent particle size means a particle size in which fine particles are classified by particle size (0.1 μm unit) and the maximum number of fine particles are classified. The particle size of the fine particles described below (including the examples) means the most frequent particle size.

The lower the haze value of the surface, the smaller the blurring of the display, and the clearer the display can be obtained. Occur. On the contrary, if the haze value is too high, it becomes whitish and whitening (reduction of black density) occurs. The surface haze value (hs) is
0.5 <hs <30 is preferable, 7 ≦ hs ≦ 20 is more preferable, and 7 ≦ hs ≦ 15 is most preferable. In order to control the surface haze value, it is preferable to provide appropriate irregularities on the resin layer surface with fine particles. Haze value (cloudiness value) is JI
According to SK-7105, a measuring instrument (for example, HR-10
0, manufactured by Murakami Color Research Laboratory). When the particle diameter of the transparent fine particles is 2.0 μm or less, the surface irregularities are small, the effect of surface scattering is small, and reflection by external light cannot be sufficiently suppressed. On the other hand, when the particle diameter is 5.0 μm or more, the surface irregularities become large and the reflection is suppressed, but the whiteness is remarkably reduced and the display quality is deteriorated. Particle size is 2.2 to 4.7μ
m is preferable, and 2.4 to 4.5 μm is more preferable.

The surface irregularities preferably have an average surface roughness (Ra) of 1.2 μm or less, more preferably 0.5 μm or less, and most preferably 0.2 μm or less. There is a correlation between the haze value of the light diffusion film, particularly the internal scattering haze that greatly contributes to the diffusion of transmitted light and the viewing angle improving effect. That is, if the light emitted from the backlight is diffused by the light diffusion film provided on the surface of the polarizing plate on the viewing side, the viewing angle characteristic is improved. However, if it is diffused too much, the backscatter becomes large and the front luminance is reduced. Also, if the scattering is too large,
The problem that the image sharpness is deteriorated occurs. The internal scattering haze is preferably 30 to 80%, more preferably 35 to 70%, most preferably 40 to 60%. As a method of increasing the internal scattering haze, a method of increasing the particle concentration having a particle diameter of 0.5 μm to 1.5 μm, a method of increasing the difference in refractive index between the transparent resin and the transparent fine particles, or a transparent light is used. A method of reducing the size of the fine particles can be adopted. From the viewpoint of visibility, it is also necessary to provide the surface haze with the surface irregularities. The surface haze is preferably 40 to 90% in the presence of the internal scattering haze and the surface haze, and is 45
To 80% is more preferable, and 50 to 70% is the most preferable.

By using the translucent fine particles having at least two particle size distribution peaks as described above, it is possible to independently optimize the viewing angle characteristics relating to the display quality and the reflection of external light. The intensity of the two particle size distribution peaks (substantially the mixing ratio of the two types of light-transmitting fine particles) allows the light diffusion function of the transparent protective film to be finely set, as compared with fine particles having a single peak. be able to.

The transparent fine particles are preferably a mixture of two or more kinds of monodisperse fine particles having different particle sizes. If the fine particles before mixing (although they are not monodispersed after mixing) are monodisperse (there is no variation in particle size), the haze can be easily adjusted with respect to the scattering characteristics. Variations are reduced and the haze value is easier to design. Organic fine particles or inorganic fine particles can be used as the translucent fine particles. As organic fine particles,
Plastic beads are preferred. It is preferable to select and use a material having a difference in refractive index with the translucent resin that has the above-mentioned numerical value, from plastics having high transparency. Examples of plastic beads include acrylic-styrene copolymer beads (refractive index: 1.55), melamine beads (refractive index: 1.
57), polycarbonate beads (refractive index: 1.5
7), styrene beads (refractive index: 1.60), crosslinked polystyrene beads (refractive index: 1.61), polymethylmethacrylate beads (refractive index: 1.49), silica beads (refractive index: 1.44), Included are benzoguanamine-melamine formaldehyde beads (refractive index: 1.68) and polyvinyl chloride beads (refractive index: 1.60). The particle size of the plastic beads is preferably 0.1 to 5 μm. The plastic beads are preferably used in an amount of 5 to 30 parts by mass with respect to 100 parts by mass of the translucent resin.

When the light-transparent fine particles tend to settle in the resin composition (light-transmitting resin), an inorganic filler (eg silica) may be added to prevent settling. In addition, when the addition amount of the inorganic filler is increased, the transparency of the coating film is adversely affected. Therefore, it is preferable to add an inorganic filler having a particle diameter of 0.5 μm or less to the translucent resin in an amount of less than 0.1% by mass to the extent that the transparency of the coating film is not impaired.

As the translucent resin, a resin which is cured by ultraviolet rays or electron beams is generally used. Specifically, it can be classified into three types: an ionizing radiation curable resin, an ionizing radiation curable resin, a mixture of a thermoplastic resin and a solvent, and a thermosetting resin. The thickness of the light diffusion layer is 0.5 to 50 μm.
m is preferable, 1 to 20 μm is more preferable, 2 to 10 μm is further preferable, and 3 to 7 μm is most preferable.

The translucent resin has a refractive index of 1.50 to 2.
00 is preferable, 1.57 to 1.90 is more preferable, and 1.64 to 1.80 is most preferable. The refractive index of the transparent resin is a value measured without the transparent fine particles. If the refractive index is too small, the antireflection property will decrease.
When the refractive index is too large, the tint of reflected light becomes strong.

The binder used for the translucent resin is preferably a polymer having a saturated hydrocarbon or polyether as the main chain, and more preferably a polymer having a saturated hydrocarbon as the main chain. Further, the binder is preferably crosslinked. The polymer having a saturated hydrocarbon as a main chain is preferably obtained by a polymerization reaction of an ethylenically unsaturated monomer. In order to obtain a crosslinked binder, it is preferable to use a monomer having two or more ethylenically unsaturated groups.

Examples of the monomer having two or more ethylenically unsaturated groups include esters of polyhydric alcohol and (meth) acrylic acid (eg, ethylene glycol di (meth) acrylate, 1,4-dichlorohexanediene). Acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,3,5-
Cyclohexanetriol trimethacrylate, polyurethane polyacrylate, polyester polyacrylate), vinylbenzene derivatives (eg, 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone), vinyl sulfone (Eg, divinyl sulfone), acrylamide (eg, methylenebisacrylamide) and methacrylamide. More than 5 functional alcohol (meta)
Acrylate can form a coating having high hardness, that is, high scratch resistance. A commercially available monomer (for example, a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate) is also preferably used.

The monomer having an ethylenically unsaturated group is
After being dissolved, coated and dried in a solvent together with various polymerization initiators and other additives, it can be cured by a polymerization reaction by ionizing radiation or heat. Instead of or in addition to the monomer having two or more ethylenically unsaturated groups, a crosslinked structure may be introduced into the binder by a reaction of the crosslinkable group. Examples of the crosslinkable functional group include an isocyanate group, an epoxy group, an aziridine group, an oxazoline group, an aldehyde group, a carbonyl group, a hydrazine group, a carboxyl group, a methylol group and an active methylene group. Vinyl sulfonic acid, acid anhydride, cyanoacrylate derivative, melamine, etherified methylol, ester and urethane, and metal alkoxide such as tetramethoxysilane can also be used as a monomer for introducing a crosslinked structure. You may use the functional group which shows crosslinkability as a result of a decomposition reaction like a block isocyanate group. That is, the crosslinkable functional group may be in a precursor state (which shows reactivity as a result of decomposition). The binder having a crosslinkable functional group can form a crosslinked structure by heating after coating.

The transparent resin binder is formed of, in addition to the above binder polymer, a polymer obtained by copolymerizing a monomer having a high refractive index with the binder polymer or a metal oxide ultrafine particle having a high refractive index. Examples of high refractive index monomers include
Bis (4-methacryloylthiophenyl) sulfide,
Vinyl naphthalene, vinyl phenyl sulfide and 4
-Methacryloxyphenyl-4'-methoxyphenyl thioether. Examples of the metal used for the metal oxide ultrafine particles having a high refractive index are zirconium, titanium,
Includes aluminum, indium, zinc, tin and antimony. As the metal oxide, ZrO ₂ , Ti
O ₂ , Al ₂ O ₃ , In ₂ O ₃ , ZnO, SnO ₂ , S
b ₂ O ₃ and ITO are preferred. ZrO ₂ is particularly preferred. The particle size of the ultrafine particles is preferably 100 nm or less,
50 nm or less is more preferable. The amount of the ultrafine metal oxide particles added is preferably 10 to 90% by mass of the translucent resin, and more preferably 20 to 80% by mass.

When cellulose triacetate is used as a transparent support, the solvent of the coating liquid for forming the light-transmitting resin is a solvent in which cellulose triacetate is dissolved,
It is preferable to use a mixture with a solvent in which cellulose triacetate is insoluble. The boiling point of the solvent in which cellulose triacetate is not dissolved is preferably higher than the boiling point of the solvent in which cellulose triacetate is dissolved. The temperature difference between the boiling point of the solvent in which cellulose triacetate is insoluble and the boiling point of the solvent in which cellulose triacetate is soluble is preferably 30 ° C. or higher, and more preferably higher than 50 ° C. When two kinds of solvents in which cellulose triacetate is dissolved or in which cellulose triacetate is not dissolved are used in combination, it is sufficient that at least one kind of solvent satisfies the above stipulation. Regarding the temperature difference of boiling points,
It is preferable that the above-mentioned rule is satisfied in comparison with the solvent having the highest boiling point.

The solvent in which cellulose triacetate is dissolved means a solvent in which the solubility of cellulose triacetate having an acetylation degree of 60% at 25 ° C. is 1% by mass or more. The solvent in which cellulose triacetate does not dissolve,
It means a solvent in which the solubility of cellulose triacetate having an acetylation degree of 60% at 25 ° C. is less than 1% by mass. Examples of solvents in which cellulose triacetate is soluble include ethers having 3 to 12 carbon atoms (eg, dibutyl ether,
Dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, 1,3
-Dioxolane, 1,3,5-trioxane, tetrahydrofuran, anisole, phenetole), a ketone having 3 to 12 carbon atoms (eg, acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, Methylcyclohexanone, methylcyclohexanone), esters having 3 to 12 carbon atoms (eg, ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, propionate ethyl, acetic acid n)
-Pentyl, γ-ptyrolactone) and an organic solvent having two or more kinds of functional groups (eg, methyl 2-methoxyacetate, methyl 2-ethoxyacetate, ethyl 2-ethoxyacetate, ethyl 2-ethoxypropionate, 2-methoxyethanol) , 2-propoxyethanol, 2-butoxyethanol, 1,2-diacetoxyacetone, acetylacetone, diacetone alcohol, methyl acetoacetate, ethyl acetoacetate).

Examples of solvents in which cellulose triacetate is insoluble include alcohols (eg, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl). 2-butanol, cyclohexanol), ester (eg, isobutyl acetate), ketone (eg, methyl isobutyl ketone, 2-octanone, 2-
(Pentanone, 2-hexanone, 2-heptanone, 3-pentanone, 3-heptanone, 4-heptanone).

The mass ratio (A / B) of the amount (A) of the solvent in which cellulose triacetate is dissolved and the amount (B) of the solvent in which cellulose triacetate is not dissolved is 5/95 to 5
0/50 is preferable, 10/90 to 40/60 is more preferable, and 15/85 to 30/70 is most preferable.

The ionizing radiation-curable resin composition can be cured by irradiation with electron beams or ultraviolet rays.

In the case of electron beam curing, an electron beam accelerator (eg, Cockroff-Walton type, Van de Graaff type, resonance transformer type, insulating core transformer type, linear type, dynamitron type,
Electron beam emitted from high frequency type) is used. The electron beam energy is preferably 50 to 1000 KeV and 10
0 to 300 KeV is more preferable. In the case of ultraviolet curing, ultraviolet rays emitted from a light source (for example, ultra-high pressure mercury lamp, high pressure mercury lamp, low pressure mercury lamp, carbon arc, xenon arc, metal halide lamp) are used.

In the transparent protective film having a light diffusing function, it is preferable to use a polymer film or a glass plate as the transparent support, and it is more preferable to use a polymer film. Examples of polymers forming the polymer film include cellulose ester (cellulose triacetate, cellulose diacetate, cellulose acetate butyrate), cellulose film, polyester (eg,
Polyethylene terephthalate), polyether sulfone, polyolefins (eg polyacrylic acid esters, polymethylpentene), polyurethanes, polycarbonates, polysulfones, polyethers, polyetherketones and poly (meth) acrylonitriles. The thickness of the transparent support is preferably 25 to 1000 μm.

Since the transparent support is used on the outermost surface of the polarizing plate, a cellulose acetate film which is generally used as a protective film for polarizing plates is particularly preferable. Cellulose acetate film has an acetylation degree of 59.0 to 6
It is preferably 1.5% cellulose triacetate. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is ASTM: D-817-
According to the measurement and calculation of the degree of acetylation in 91 (Test method for cellulose acetate etc.). The viscosity average degree of polymerization (DP) of cellulose acetate is preferably 250 or more, more preferably 290 or more.
The cellulose acetate preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a weight average molecular weight and Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, and most preferably 1.4 to 1.6. preferable.

Generally, the 2-, 3- and 6-positions of cellulose
The hydroxyl group at the position is not uniformly substituted with an acetyl group, but the degree of substitution at the 6-position tends to be smaller than the degree of substitution at the 2-position and the 3-position. In the cellulose acetate used for the transparent support, the 6-position substitution degree is preferably equal to or higher than the 2-position and 3-position. 2nd place,
The ratio of the 6-position substitution degree to the total of the 3-position and 6-position substitution degrees is preferably 32% or more, more preferably 33% or more, and most preferably 34% or more. The 6-position substitution degree of cellulose acetate is
It is also preferably 0.88 or more. The substitution degree at each position can be measured by NMR. JP-A-1
Paragraph Nos. [0043] to [004 of Japanese Patent Laid-Open No. 1-5851
4] [Example] [Synthesis Example 1], paragraph numbers [0048] to
[0049] [Synthesis example 2], paragraph numbers [0051] to
[0052] The cellulose acetate obtained by the method of [Synthesis example 3] can be used for the transparent support.

It is preferable to produce the cellulose acetate film by the solvent casting method. In the solvent cast method, a film is manufactured using a solution (dope) in which cellulose acetate is dissolved in an organic solvent.
The organic solvent includes ether having 3 to 12 carbon atoms, ketone having 3 to 12 carbon atoms, and 3 to 12 carbon atoms.
It is preferable to include a solvent selected from the ester and a halogenated hydrocarbon having 1 to 6 carbon atoms. The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, -O-, -CO- and -COO-) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the ketone having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. 3 to 1 carbon atoms
Examples of esters of 2 include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol. The number of carbon atoms in the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of hydrogen atoms in the halogenated hydrocarbon substituted with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and 35 to 65 mol%.
More preferably, it is 40% by mol, and most preferably 40-60% by mol. Methylene chloride is a typical halogenated hydrocarbon. You may mix and use 2 or more types of organic solvents.

The cellulose acetate solution can be prepared by a general method. The general method means treatment at a temperature of 0 ° C. or higher (normal temperature or high temperature). The solution can be prepared by using the dope preparation method and apparatus in the usual solvent casting method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent. The amount of cellulose acetate is adjusted so that the obtained solution contains 10 to 40% by mass. The amount of cellulose acetate is more preferably 10 to 30% by mass. The organic solvent (main solvent) may contain any of the additives described below. The solution can be prepared by stirring cellulose acetate and an organic solvent at room temperature (0 to 40 ° C.). The highly concentrated solution may be stirred under pressure and heat. Specifically, the cellulose acetate and the organic solvent are placed in a pressure vessel and sealed, and the mixture is stirred under pressure while being heated to a temperature not lower than the boiling point of the solvent at room temperature and not boiling the solvent. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

Each component may be roughly mixed in advance and then put in a container. Moreover, you may throw in in a container one by one. The container must be configured to allow stirring. The container can be pressurized by injecting an inert gas such as nitrogen gas.
Alternatively, the increase in vapor pressure of the solvent due to heating may be used. Alternatively, after sealing the container, each component may be added under pressure. When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. It is also possible to heat the entire container by providing a plate heater outside the container and piping to circulate the liquid. It is preferable to provide a stirring blade inside the container and use this to stir. The stirring blade is
The length that reaches the vicinity of the wall of the container is preferable. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the wall of the container. Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is cooled and then taken out from the container, or after taking out, it is cooled using a heat exchanger or the like.

The solution can also be prepared by the cooling dissolution method. In the cooling dissolution method, cellulose acetate can be dissolved even in an organic solvent which is difficult to dissolve by a usual dissolution method. Even if the solvent is a solvent that can dissolve cellulose acetate by an ordinary dissolution method, the cooling dissolution method has an effect of rapidly obtaining a uniform solution. In the cooling dissolution method, first, cellulose acetate is gradually added to an organic solvent with stirring at room temperature. The amount of cellulose acetate is preferably adjusted so as to be contained in this mixture in an amount of 10 to 40% by mass. The amount of cellulose acetate is more preferably 10 to 30% by mass. Furthermore, any additives described below may be added to the mixture.

Next, the mixture is heated to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50).
To -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (-75 ° C) or a cooled diethylene glycol solution (-30 to -20 ° C). When cooled in this way, the mixture of cellulose acetate and organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, 12
Most preferably, it is at least ° C / min. The higher the cooling rate, the more preferable, but 10000 ° C./sec is the theoretical upper limit, 1000 ° C./sec is the technical upper limit, and 1
00 ° C./sec is a practical upper limit. The cooling rate is
It is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling until the final cooling temperature is reached.

Further, this is 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C.,
When heated to the most preferably 0 to 50 ° C., the cellulose acetate dissolves in the organic solvent. The temperature may be raised by leaving it at room temperature or by heating it in a warm bath. The heating rate is preferably 4 ° C / min or more, and 8 ° C / min.
It is more preferably at least minutes, and most preferably at 12 ° C./minute or more. The higher the heating rate, the more preferable, but 10000 ° C./sec is the theoretical upper limit,
0 ° C./sec is the technical upper limit and 100 ° C./sec is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating to the final heating temperature. . A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be judged only by visually observing the appearance of the solution.

In the cooling dissolution method, it is desirable to use a closed container in order to avoid mixing of water due to dew condensation during cooling. In the cooling and heating operation, pressure is applied during cooling,
If the pressure is reduced during heating, the dissolution time can be shortened. In order to carry out the pressurization and depressurization, it is desirable to use a pressure resistant container. A 20% by mass solution of cellulose acetate (acetylation degree: 60.9%, viscosity average degree of polymerization: 299) dissolved in methyl acetate by a cooling dissolution method was 3% by differential scanning calorimetry (DSC).
A quasi-phase transition point between a sol state and a gel state exists near 3 ° C., and at this temperature or lower, a uniform gel state is obtained. Therefore,
This solution must be kept at a temperature not lower than the pseudo phase transition temperature, preferably about 10 ° C. plus the gel phase transition temperature. However, this pseudo-phase transition temperature differs depending on the degree of acetylation of cellulose acetate, the viscosity average degree of polymerization, the solution concentration and the organic solvent used.

A cellulose acetate film is produced from the prepared cellulose acetate solution (dope) by the solvent casting method. The dope is cast on a drum or band and the solvent is evaporated to form a film. The dope before casting is preferably adjusted in concentration so that the solid content is 18 to 35%. The surface of the drum or band is preferably mirror-finished. Regarding the casting and drying methods in the solvent casting method, US Pat.
No. 03, No. 2492078, No. 2492977, No. 2492978, No. 2607704, No. 27390.
No. 69, No. 2739070, British Patent 640731.
Nos. 736,892 and JP-B-45-455
4, JP-A-49-5614, JP-A-60-176834.
Nos. 60-203430 and 62-115035. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or lower.
After casting, it is preferable to apply air for 2 seconds or more to dry. It is also possible to strip the obtained film from the drum or band and further dry it with hot air whose temperature is successively changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, the time from casting to stripping can be shortened. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

The prepared cellulose acetate solution (dope) may be used to form a film by casting two or more layers. In this case, it is preferable to produce the cellulose acetate film by the solvent casting method.
The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 10 to 40%. The surface of the drum or band is preferably mirror-finished.

When a plurality of cellulose acetate solutions having two or more layers are cast, a plurality of cellulose acetate solutions are respectively cast from a plurality of casting holes provided at intervals in the traveling direction of the support while being laminated. A film can be produced (described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285). The film can also be formed by casting a cellulose acetate solution from two casting ports (Japanese Patent Publication No. 60-27562, JP-A No. 61-947).
No. 24, No. 61-946245, No. 61-10481.
No. 3, 61-158413, and JP-A-6-13.
4933). In addition, a cellulose acetate film casting method (described in JP-A-56-162617) in which a flow of a high-viscosity cellulose acetate solution is wrapped with a low-viscosity cellulose acetate solution and the high- and low-viscosity cellulose acetate solutions are simultaneously extruded is disclosed. May be adopted.

The film formed on the support by the first casting port is peeled off using the two casting ports, and the second casting is performed on the side in contact with the surface of the support. Can be prepared (described in JP-B-44-20235). The plurality of cellulose acetate solutions may have the same composition. In order to give a function to a plurality of cellulose acetate layers, a cellulose acetate solution corresponding to the function may be extruded from each casting port.
The cellulose acetate solution is used for other functional layers (eg, adhesive layer, dye layer, antistatic layer, antihalation layer, U layer).
It is also possible to simultaneously cast the V absorbing layer, the polarizing layer, etc.).

In the monolayer solution, it is necessary to extrude a highly concentrated and highly viscous cellulose acetate solution in order to obtain a required film thickness. In that case, the stability of the cellulose acetate solution is poor, and solid matters are generated, which often causes problems such as defective spots and poor flatness. By casting a plurality of cellulose acetate solutions through the casting port, a highly viscous solution can be simultaneously extruded onto the support. Further, not only can the flatness be improved and an excellent planar film can be produced, but also by using a concentrated cellulose acetate solution, the drying load can be reduced and the film production speed can be increased.

A plasticizer may be added to the cellulose acetate film in order to improve the mechanical properties or improve the drying speed. As a plasticizer,
Phosphate esters or carboxylic acid esters are used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TC).
P) is included. Typical carboxylic acid esters are phthalic acid esters and citric acid esters. Examples of phthalates include dimethyl phthalate (DM
P), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). An example of a citric acid ester is triethyl O-acetylcitrate (OACT).
E) and O-acetyl tributyl citrate (OACT
B) is included. Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate,
Includes dibutyl sebacate and various trimellitic acid esters. Phthalates plasticizer (DMP, DE
P, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The amount of plasticizer added is 0.1 to 25 times the amount of cellulose ester.
It is preferably mass%, more preferably 1 to 20 mass%, and most preferably 3 to 15 mass%.

A deterioration inhibitor (eg, antioxidant, peroxide decomposer, radical inhibitor, metal deactivator, acid scavenger, amine) may be added to the cellulose acetate film. For the deterioration preventing agent, see JP-A-3-19920.
No. 1, No. 5-1907073, No. 5-194789
Nos. 5,271,471 and 6,107,854. The addition amount of the deterioration inhibitor is preferably 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. If the addition amount is less than 0.01% by mass, the effect of the deterioration inhibitor is hardly recognized. Addition amount is 1% by mass
If it exceeds the range, bleed-out (bleeding) of the deterioration preventive agent on the film surface may be observed. Butylated hydroxytoluene (BHT) and tribenzylamine (TBA) can be mentioned as examples of particularly preferable deterioration preventing agents.

The cellulose acetate film is preferably surface-treated. Specific methods include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment and ultraviolet irradiation treatment. Further, an undercoat layer (described in JP-A-7-333433) may be provided. From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film is set to Tg in these treatments.
(Glass transition temperature) or less, specifically 150 ° C. or less is preferable. When used as a transparent protective film for a polarizing plate, it is particularly preferable to carry out acid treatment or alkali treatment, that is, saponification treatment of cellulose acetate, from the viewpoint of adhesion to the polarizing film. The surface energy is preferably 55 mN / m or more, 60 mN
/ M or more and 75 mN / m or less is more preferable.

Alkali saponification treatment is most preferred. The alkali saponification treatment is preferably carried out in a cycle of immersing the film surface in an alkali solution, neutralizing the film with an acid solution, washing with water and drying. Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution, and the normal concentration of hydroxide ion is preferably 0.1 to 3.0N, more preferably 0.5 to 2.0N. preferable. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably 40 to 70 ° C. From the viewpoint of productivity, it is preferable to apply an alkali solution, and after the saponification treatment, remove the alkali from the film surface by washing with water. From the viewpoint of wettability, an alcohol (eg, I
PA, n-butanol, methanol, ethanol) are preferable, and it is also preferable to add an alkali dissolution aid (eg, water, propylene glycol, ethylene glycol).

The surface energy of a solid can be determined by the contact angle method, the heat of wetting method, and the adsorption method as described in "Basic Wetting and Application of Wetting" (published by Realize Co., December 12, 1989). In the case of the cellulose acetate film of the present invention, it is preferable to use the contact angle method. Specifically, two kinds of solutions having known surface energies are dropped onto a cellulose acetate film, and at the intersection between the surface of the droplet and the film surface, the angle between the tangent line drawn to the droplet and the film surface is used. The surface energy of the film can be calculated by defining the angle containing the drop as the contact angle.

[Low Refractive Index Layer] A low refractive index layer can be provided on the transparent protective film having a light diffusing function. The low bending rate layer can function as an antireflection layer. By providing the low refractive index layer, it is possible to achieve an integrated sphere average reflectance of 2.5% or less in the wavelength range of 450 to 650 nm. The low refractive index layer preferably has a refractive index of 1.35 to 1.45. The refractive index of the low refractive index layer preferably satisfies the following mathematical formula (I). (I) (mλ / 4) × 0.7 <n1d1 <(mλ / 4) × 1.3 In the formula, m is a positive odd number (generally 1), and n1 is the refractive index of the low refractive index layer. , And d1 is the film thickness (nm) of the low refractive index layer. Λ is the wavelength of visible light,
The value is in the range of 50 to 650 (nm). Satisfying the above formula (I) means that there is m (a positive odd number, usually 1) satisfying the formula (I) in the above wavelength range.

The low refractive index layer is preferably composed of a crosslinked cured product of a composition containing a fluorine-containing compound and inorganic fine particles by heat or ionizing radiation. Using a crosslinkable fluorine-containing compound as the fluorine-containing compound, a crosslinking reaction is carried out,
As a result, it is preferable to form a cured fluororesin. The dynamic friction coefficient of the cured fluorine-containing resin is
It is preferably 0.03 to 0.15. The contact angle of the cured fluororesin with water is preferably 90 to 120 degrees. As the crosslinkable fluorine-containing compound, a perfluoroalkyl group-containing silane compound (eg,
(Heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane) is preferably used. Further, a fluorinated copolymer having a fluorinated monomer and a monomer for imparting a crosslinkable group as constitutional units may be used.

Examples of fluorine-containing monomers include fluoroolefins (eg, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2).
-Dimethyl-1,3-dioxole), partially or fully fluorinated alkyl esters of (meth) acrylic acid and fully or partially fluorinated vinyl ethers. Kind of things. As the partially or fully fluorinated alkyl ester of (meth) acrylic acid, a commercially available product (eg, biscoat 6FM, manufactured by Osaka Organic Chemical Co., Ltd .; M-2020, manufactured by Daikin Co., Ltd.) can also be used. As a monomer for imparting a crosslinkable group, a crosslinkable functional group (eg, glycidyl group, carboxyl, hydroxyl, amino, sulfo) is included in the molecule.
A (meth) acrylate monomer having (eg, glycidyl methacrylate, (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate) is used. The crosslinked structure may be introduced after forming the polymer (described in JP-A Nos. 10-25388 and 10-147739).

For the low refractive index layer, not only a copolymer of the above-mentioned fluorine-containing monomer and a monomer for imparting a crosslinkable group, but also a polymer obtained by copolymerizing this with another monomer may be used. Examples of other monomers that can be copolymerized include:
Olefins (eg ethylene, propylene, isoprene,
Vinyl chloride, vinylidene chloride), acrylic acid ester (eg, methyl acrylate, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate), methacrylic acid ester (eg, methyl methacrylate, ethyl methacrylate, butyl methacrylate, Ethylene glycol dimethacrylate), styrene, styrene derivative (eg, divinylbenzene, vinyltoluene, α-methylstyrene), vinyl ether (eg, methyl vinyl ether),
Vinyl ester (eg, vinyl acetate, vinyl propionate, vinyl cinnamate), acrylamides (eg, N-tert.
-Butylacrylamide, N-cyclohexylacrylamide), methacrylamide and acrylonitrile.

The fluorine-containing resin used for the low refractive index layer preferably has an average particle size of 0.1 μm in order to impart scratch resistance.
m or less, more preferably 0.001 to 0.05 μm S
It is preferable to use ultrafine oxide particles of i. From the viewpoint of antireflection property, the lower the refractive index, the more preferable, but as the refractive index of the fluororesin is lowered, the scratch resistance deteriorates.
Therefore, by optimizing the refractive index of the fluorine-containing resin and the addition amount of the Si oxide ultrafine particles, it is possible to find the best balance between scratch resistance and low refractive index. As the Si oxide ultrafine particles, silica sol dispersed in a commercially available organic solvent may be added to the coating solution as it is, or various commercially available silica powders may be dispersed in an organic solvent and used.

[Transparent protective film functioning as retardation film] Re retardation value and Rt of the retardation film
The h retardation value is defined by the following formulas (I) and (II), respectively. The measurement wavelength is 550 nm. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d In the formulas (I) and (II), nx is the slow axis direction in the film plane ( The direction in which the refractive index becomes maximum). In the formulas (I) and (II), ny is the refractive index in the fast axis direction (direction in which the refractive index is minimum) in the film plane. In the formula (II), nz is the refractive index in the thickness direction of the film. In formulas (I) and (II), d
Is the film thickness in nm.

In the transparent protective film functioning as a retardation film, the Re retardation value is 20 to 70 nm,
Then, the Rth retardation value is 70 to 400 nm
Adjust to. When two transparent protective films functioning as a retardation film are used in the liquid crystal display device, the Rth retardation value of the film is preferably 70 to 200 nm. When a single transparent protective film that functions as a retardation film is used in a liquid crystal display device, the Rth retardation value of the film is preferably 150 to 400 nm. The birefringence of the retardation film (Δn: nx−
ny) is preferably 0.00025 to 0.00088. The birefringence index {(nx + ny) / 2-nz} of the retardation film in the thickness direction is 0.00088.
It is preferably from 0.005 to 0.005.

A transparent polymer film has been conventionally used as the retardation film. Examples of the resin film and polymer include norbornene resin, cellulose ester (eg, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate), polyester (eg, polyethylene terephthalate, polycarbonate), polyether sulfone, polyolefin (eg, poly Methyl pentene, polyacrylic acid ester), polyurethane, polysulfone, polyether, polyether ketone and poly (meth) acrylonitrile.
Commercially available norbornene resin (Arton, manufactured by JSR Corporation);
ZEONEX, ZEONOR, manufactured by Nippon Zeon Co., Ltd. may be used. The thickness of the transparent protective film that functions as a retardation film is preferably 25 to 300 μm.

As the transparent protective film functioning as a retardation film, it is preferable to use a cellulose acetate film which is generally used as a protective film for polarizing plates. That is, in order not to make the liquid crystal display device thick, it is preferable to use one sheet of cellulose acetate film having both a function as a retardation film and a function as a transparent protective film (protective function of the polarizing film).
Cellulose acetate film generally does not cause birefringence. Therefore, in order to impart the above retardation value, it is preferable to use the following retardation increasing agent and further carry out a stretching treatment.

An aromatic compound having at least two aromatic rings can be used as a retardation increasing agent for the cellulose acetate film. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acetate. The aromatic compound is based on 100 parts by mass of cellulose acetate,
It is more preferably used in the range of 0.05 to 15 parts by mass, and most preferably 0.1 to 10 parts by mass. You may use together two or more types of aromatic compounds. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

The aromatic hydrocarbon ring is a 6-membered ring (that is,
A benzene ring) is particularly preferable. The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, a 6-membered ring or a 7-membered ring, more preferably a 5-membered ring or a 6-membered ring.
The aromatic heterocycle generally has the largest number of double bonds.
As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring,
Oxazole ring, isoxazole ring, thiazole ring,
Isothiazole ring, imidazole ring, pyrazole ring, furazan ring, triazole ring, pyran ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,3
A 5-triazine ring is included. As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, A benzene ring and a 1,3,5-triazine ring are more preferable. It is particularly preferred that the aromatic compound has at least one 1,3,5-triazine ring.

The number of aromatic rings contained in the aromatic compound is 2
It is preferably from 20 to 20, more preferably from 2 to 12, even more preferably from 2 to 8, and most preferably from 2 to 6. The bonding relationship between two aromatic rings is (b) when forming a condensed ring (a).
It can be classified into a case where it is directly connected by a single bond and a case where it is connected through a linking group (c) (because it is an aromatic ring, a spiro bond cannot be formed). The connection relation may be any of (a) to (c).

Examples of the condensed ring of (a) (condensed ring of two or more aromatic rings) include indene ring, naphthalene ring, azulene ring, fluorene ring, phenanthrene ring, anthracene ring, acenaphthylene ring, naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring,
A phenanthridine ring, a xanthene ring, a phenazine ring, a phenothiazine ring, a phenoxathiine ring, a phenoxazine ring and a thianthrene ring are included. A naphthalene ring, an azulene ring, an indole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring, a benzotriazole ring and a quinoline ring are preferable. The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Connect two aromatic rings with two or more single bonds,
An aliphatic ring or a non-aromatic heterocycle may be formed between the two aromatic rings.

The linking group (c) is also preferably bonded to the carbon atoms of the two aromatic rings. The linking group is an alkylene group, an alkenylene group, an alkynylene group, -CO-, -O.
It is preferably-, -NH-, -S- or a combination thereof. Examples of linking groups composed of combinations are shown below. Note that the left-right relationship in the following examples of the linking group may be reversed. c1: -CO-O- c2: -CO-NH- c3: -alkylene-O- c4: -NH-CO-NH- c5: -NH-CO-O- c6: -O-CO-O- c7: -O-alkylene-O-c8: -CO-alkenylene-c9: -CO-alkenylene-NH-c10: -CO-alkenylene-O-c11: -alkylene-CO-O-alkylene-O-CO
-Alkylene-c12: -O-alkylene-CO-O-alkylene-O-
CO-alkylene-O-c13: -O-CO-alkylene-CO-O-c14: -NH-CO-alkenylene-c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent. Examples of the substituent include a halogen atom (F, C
1, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl group, alkenyl group, alkynyl group, aliphatic acyl group, aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group , Alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamide group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic substituted sulfamoyl group, aliphatic substituted ureido group and non-aromatic An aromatic heterocyclic group is included.

The number of carbon atoms in the alkyl group is preferably 1-8. A chain alkyl group is preferable to a cyclic alkyl group, and a straight chain alkyl group is particularly preferable.
The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2
-Hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl. The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a straight chain alkenyl group is particularly preferable.
The alkenyl group may further have a substituent. Examples of alkenyl groups include vinyl, allyl and 1-hexenyl. The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a straight chain alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of alkynyl groups include ethynyl, 1-butynyl and 1-hexynyl.

The number of carbon atoms of the aliphatic acyl group is 1 to 1
It is preferably 0. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl.
The number of carbon atoms of the aliphatic acyloxy group is preferably 1-10. Examples of the aliphatic acyloxy group include acetoxy. The number of carbon atoms in the alkoxy group is 1
It is preferably from 8 to 8. The alkoxy group may further have a substituent (eg, an alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy. The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl. The alkoxycarbonylamino group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.

The number of carbon atoms in the alkylthio group is 1 to 1.
It is preferably 2. Examples of the alkylthio group include methylthio, ethylthio and octylthio.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of alkylsulfonyl groups include methanesulfonyl and ethanesulfonyl. The number of carbon atoms of the aliphatic amide group is preferably 1-10. Examples of the aliphatic amide group include acetamide. The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamide group include methanesulfonamide, butanesulfonamide and n-octanesulfonamide. The aliphatic substituted amino group preferably has 1 to 10 carbon atoms. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino. The number of carbon atoms of the aliphatic-substituted carbamoyl group is preferably 2-10. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl. The number of carbon atoms of the aliphatic-substituted sulfamoyl group is preferably 1-8. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl. The aliphatic substituted ureido group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted ureido group include methylureido. Examples of the non-aromatic heterocyclic group include piperidino and morpholino. The molecular weight of the retardation increasing agent is preferably 300 to 800. Specific examples of the retardation increasing agent are described in JP-A-200
No. 0-111914, 2000-275434, and WO 00/65384.

The cellulose acetate film is preferably stretched for adjusting the retardation and further reducing the strain. Since stretching can reduce strain in the stretching direction, biaxial stretching is more preferable in order to reduce strain in all in-plane directions. Biaxial stretching, there are simultaneous biaxial stretching method and sequential biaxial stretching method, the sequential biaxial stretching method is preferable from the viewpoint of continuous production, after casting the dope, stripped from the band or drum, width direction After stretching in the (longitudinal method), it is stretched in the longitudinal direction (width direction).

The method of stretching in the width direction is described in JP-A-62-115035, JP-A-4-152125, JP-A-4-284111, JP-A-4-298310, and JP-A-11-48271. There is. The film is stretched at room temperature or under heating. The heating temperature is preferably below the glass transition temperature of the film. The film can be stretched during processing during drying,
It is particularly effective when the solvent remains. In the case of stretching in the longitudinal direction, for example, the film is stretched by adjusting the speed of the film transport roller so that the film winding speed is faster than the film stripping speed. In the case of stretching in the width direction, the film can also be stretched by conveying while holding the width of the film with a tenter and gradually widening the width of the tenter. After the film is dried, it may be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine). The stretch ratio of the film (the ratio of the increase due to the stretching with respect to the original length) is preferably 5 to 50%, more preferably 10 to 40%, and most preferably 15 to 35%. When the stretched cellulose acetate film is used as a protective film for a polarizing plate, the transmission axis of the polarizing plate and the slow axis of the cellulose acetate film are parallel to each other. For that purpose, it is preferable that the draw ratio in the width direction is larger than the draw ratio in the longitudinal direction.

[Polarizing Plate] The polarizing plate comprises a polarizing film and two transparent protective films arranged on both sides of the polarizing film. In the polarizing plate (on the display surface side) according to the present invention, a transparent protective film that functions as the above retardation film is used as one transparent protective film, and a transparent protective film that functions as the above-mentioned light diffusion film as the other transparent protective film. To use. In the polarizing plate on the backlight side, the transparent protective film functioning as the above-mentioned retardation film can be used as one transparent protective film. A normal cellulose acetate film may be used as the other transparent protective film. Iodine-based polarizing film,
There are dye-based polarizing films and polyene-based polarizing films that use dichroic dyes. The iodine type polarizing film and the dye type polarizing film are generally manufactured using a polyvinyl alcohol type film. The slow axis of the retardation film and the transmission axis of the polarizing film are arranged so as to be substantially parallel to each other.

The moisture permeability of the transparent protective film is important for the productivity of the polarizing plate. The polarizing film and the protective film are attached with an aqueous adhesive, and the adhesive solvent is dried by diffusing in the transparent protective film. The higher the moisture permeability of the transparent protective film, the faster it will dry,
Although the productivity is improved, when it is too high, the polarizing ability is lowered due to the entry of water into the polarizing film due to the usage environment (high humidity) of the liquid crystal display device. The moisture permeability of the transparent protective film is
Thickness of polymer film (and polymerizable liquid crystal compound),
Determined by free volume, hydrophilicity / hydrophobicity, etc. When using a polymer film as a transparent protective film for a polarizing plate,
The moisture permeability is preferably 100 to 1000 g / m ² · 24 hours, 300 to 700 g / m ² · 24 hours
More preferably rs. In the case of film formation, the film thickness can be adjusted by the lip flow rate and line speed, or by stretching and compression. Since the moisture permeability differs depending on the main material used, it is possible to adjust the thickness to a preferable range. In the case of film formation, the free volume of the film can be adjusted by the drying temperature and time. Also in this case, since the moisture permeability differs depending on the main material used, it is possible to adjust the free volume to a preferable range. The hydrophilicity / hydrophobicity of the retardation film can be adjusted by an additive. The moisture permeability can be increased by adding a hydrophilic additive to the free volume, and conversely, the moisture permeability can be decreased by adding a hydrophobic additive.
By independently controlling the moisture permeability, it becomes possible to manufacture a polarizing plate having an optical compensation ability at low cost and with high productivity.

[0085]

EXAMPLES [Example 1] (Preparation of transparent protective film functioning as retardation film) A commercially available norbornene (Arton, JSR Co., Ltd.) film (thickness: 100 μm) was obtained, and the width thereof was kept at 180 ° C. After stretching 30% in the direction, 10% in the longitudinal direction,
A transparent protective film that functions as a retardation film was prepared.
About the produced transparent protective film, the ellipsometer (M-
150, manufactured by JASCO Corporation, using a wavelength of 550 nm
The Re retardation value and the Rth retardation value were measured. As a result, Re is 40 nm and Rth
Was 110 nm.

(Preparation of transparent protective film functioning as a light diffusion film) An ultraviolet curable resin (Z7 having a refractive index of 1.51)
526, manufactured by JSR Co., Ltd., 100 parts by mass, a curing initiator (Irgacure 184, manufactured by Ciba Geigy), 5 parts by mass, and a crosslink having a refractive index of 1.61 and a particle size of 1.3 μm as the first translucent particles. Styrene beads (Soken Chemical Co., Ltd.)
17 parts by mass, and 7 parts by mass of crosslinked styrene beads having a refractive index of 1.61 and a particle size of 3.5 μm (manufactured by Soken Chemical Co., Ltd.) as the second translucent fine particles are mixed with methyl ethyl ketone / methyl isobutyl ketone. It was dispersed in a solvent (mass ratio 3/7) to prepare a dispersion liquid having a solid content of 24 mass%. The dispersion liquid was mixed with cellulose triacetate film (TD-80).
U, Fuji Photo Film Co., Ltd., dry film thickness 6.0
It was applied to have a thickness of μm. After drying, 160 W / cm air-cooled metal halide lamp (I Graphics Co., Ltd.)
Illuminance 400 mW / cm ² , irradiation amount 300
The transparent protective film that functions as a light diffusion film was prepared by irradiating with ultraviolet rays of mJ / cm ² to cure the coating layer. JI
When the haze (cloudiness value) of the transparent protective film was measured using a measuring instrument (HR-100, manufactured by Murakami Color Research Laboratory) in accordance with SK-7105, it was 67%.

(Production of Polarizing Plate on Viewing Side) Iodine was adsorbed on a stretched polyvinyl alcohol film to produce a polarizing film. The transparent protective film that functions as a light diffusion film is saponified, and a polyvinyl alcohol adhesive is used to form a transparent support (cellulose triacetate film).
Was affixed to one side of the polarizing film so that was on the polarizing film side. Next, the transparent protective film functioning as a retardation film is saponified, and a polyvinyl alcohol adhesive is used to
It was attached to the opposite side of the polarizing film. In this way, the viewing side polarizing plate according to the present invention was produced.

(Production of Backlight-Side Polarizing Plate) Iodine was adsorbed on a stretched polyvinyl alcohol film to produce a polarizing film. Commercially available cellulose triacetate film (Fujitac TD80, Fuji Photo Film Co., Ltd.)
Saponification treatment) was applied to one side of the polarizing film using a polyvinyl alcohol adhesive. Next, saponification is performed on the transparent protective film that functions as a retardation film,
It was attached to the opposite side using a polyvinyl alcohol adhesive. In this way, a backlight side polarizing plate was produced.

(Production of Liquid Crystal Display Device) A pair of polarizing plates and a pair of optical compensation sheets provided in a liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.) using a vertical alignment type liquid crystal cell were peeled off. .. Then, the produced viewing-side polarizing plate was attached via an adhesive so that the transparent protective film functioning as a retardation film was on the liquid crystal cell side. Next, the produced backlight-side polarizing plate was attached via an adhesive so that the transparent protective film functioning as a retardation film was on the liquid crystal cell side. The crossed Nicols were arranged so that the transmission axis of the viewing-side polarizing plate was in the vertical direction and the transmission axis of the backlight-side polarizing plate was in the horizontal direction. About the produced liquid crystal display device, a measuring machine (EZ-Contrast160
D, manufactured by ELDIM) was used to measure the viewing angle in eight steps from black display (L1) to white display (L8). The results are shown in Table 1.

[Example 2] (Preparation of transparent protective film functioning as retardation film) The following composition was placed in a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution. did.

[0091] ────────────────────────────────────   Cellulose acetate solution composition ────────────────────────────────────   100 parts by mass of cellulose acetate having a degree of acetylation of 60.9%   Triphenyl phosphate (plasticizer) 7.8 parts by mass   Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass   Methylene chloride (first solvent) 300 parts by mass   Methanol (second solvent) 54 parts by mass   1-butanol (3rd solvent) 11 parts by mass ────────────────────────────────────

To another mixing tank, 16 parts by mass of the following retardation increasing agent, 80 parts by mass of methylene chloride and 20 parts by mass of methanol were charged and stirred while heating to prepare a retardation increasing agent solution.
25 parts by mass of the retardation increasing agent solution was mixed with 474 parts by mass of the cellulose acetate solution and sufficiently stirred to prepare a dope. The amount of retardation increasing agent added is
The amount was 3.5 parts by mass with respect to 100 parts by mass of cellulose acetate.

[0093]

[Chemical 1]

The obtained dope was cast using a band casting machine. A film with a residual solvent content of 15% by mass
At 0 ° C., transverse stretching was performed at a stretching ratio of 25% using a tenter to obtain a cellulose acetate film (thickness: 80
μm) was produced. About the produced transparent protective film (cellulose acetate film), the ellipsometer (M-
150, manufactured by JASCO Corporation, using a wavelength of 550 nm
The Re retardation value and the Rth retardation value were measured. As a result, Re was 40 nm and Rth was 110 nm.

(Preparation of transparent protective film functioning as a light diffusion film) An ultraviolet curable resin (Z7 having a refractive index of 1.61)
526, manufactured by JSR Co., Ltd.) 100 parts by mass, a curing initiator (Irgacure 184, manufactured by Ciba Geigy) 5 parts by mass, a first light transmitting fine particle having a refractive index of 1.49 and a particle size of 1.5 μm. 8 parts by mass of methyl methacrylate beads (manufactured by Soken Chemical Co., Ltd.), and crosslinked styrene beads (manufactured by Soken Chemical Co., Ltd.) 5 having a refractive index of 1.61 and a particle diameter of 3.5 μm as the second translucent fine particles. Part by mass is a mixed solvent of methyl ethyl ketone / methyl isobutyl ketone (mass ratio 1
/ 9) to prepare a dispersion having a solid content of 45% by mass. The dispersion was applied onto a cellulose triacetate film (TD-80U, manufactured by Fuji Photo Film Co., Ltd.) so that the dry film thickness was 3.5 μm. 16 after drying
Using an air-cooled metal halide lamp of 0 W / cm (manufactured by Eye Graphics Co., Ltd.), an illuminance of 400 mW / cm ² ,
Ultraviolet rays having an irradiation dose of 300 mJ / cm ² were irradiated to cure the coating layer to prepare a transparent protective film functioning as a light diffusion film. According to JIS-K-7105, the haze (cloudiness value) of the transparent protective film was measured using a measuring device (HR-100 manufactured by Murakami Color Research Laboratory), and it was 48%.

(Production of Polarizing Plate on Viewing Side) Iodine was adsorbed on a stretched polyvinyl alcohol film to produce a polarizing film. The transparent protective film that functions as a light diffusion film is saponified, and a polyvinyl alcohol adhesive is used so that the transparent support (cellulose triacetate film) of the transparent protective film that functions as a light diffusion film is on the polarizing film side. It was attached to one side of the polarizing film. Next, the transparent protective film functioning as a retardation film was saponified, and a polyvinyl alcohol-based adhesive was used to attach it to the opposite side of the polarizing film. The slow axis of the retardation film and the transmission axis of the polarizing film were arranged so as to be parallel to each other. In this way, the viewing side polarizing plate according to the present invention was produced.

(Production of Backlight-Side Polarizing Plate) Iodine was adsorbed on a stretched polyvinyl alcohol film to produce a polarizing film. Commercially available cellulose triacetate film (Fujitac TD80, Fuji Photo Film Co., Ltd.)
Saponification treatment) was applied to one side of the polarizing film using a polyvinyl alcohol adhesive. Next, saponification is performed on the transparent protective film that functions as a retardation film,
It was attached to the opposite side of the polarizing film using a polyvinyl alcohol adhesive. The slow axis of the retardation film and the transmission axis of the polarizing film were arranged so as to be parallel to each other. In this way, a backlight side polarizing plate was produced.

(Production of Liquid Crystal Display Device) A pair of polarizing plates and a pair of optical compensation sheets provided in a liquid crystal display device (VL-1530S, manufactured by Fujitsu Limited) using a vertical alignment type liquid crystal cell were peeled off. . Then, the produced viewing-side polarizing plate was attached via an adhesive so that the transparent protective film functioning as a retardation film was on the liquid crystal cell side. Next, the produced backlight-side polarizing plate was attached via an adhesive so that the transparent protective film functioning as a retardation film was on the liquid crystal cell side. The crossed Nicols were arranged so that the transmission axis of the viewing-side polarizing plate was in the vertical direction and the transmission axis of the backlight-side polarizing plate was in the horizontal direction. About the produced liquid crystal display device, a measuring machine (EZ-Contrast160
D, manufactured by ELDIM) was used to measure the viewing angle in eight steps from black display (L1) to white display (L8). The results are shown in Table 1.

[Example 3] (Preparation of transparent protective film functioning as retardation film) A dope was prepared by mixing 474 parts by mass of a cellulose acetate solution with 56 parts by mass of a retardation increasing agent solution (100 parts by mass of cellulose acetate). 7.8 parts by weight of the retardation increasing agent) and a draw ratio of 14
A cellulose acetate film was produced in the same manner as in Example 2 except that the percentage was changed. About the produced transparent protective film (cellulose acetate film), a wavelength of 5 was measured using an ellipsometer (M-150, manufactured by JASCO Corporation).
The Re retardation value and Rth retardation value at 50 nm were measured. As a result, Re is 50n
m and Rth were 240 nm.

(Transparent protection that functions as a light diffusion film
Fabrication of film) UV curable resin (DP with refractive index of 1.54)
HA, manufactured by Nippon Kayaku Co., Ltd.) 100 parts by mass, curing initiator
(Irgacure 907, manufactured by Ciba Geigy) 3 mass
And a transparent particle having a refractive index of 1.61 and a particle size
Of 1.3 μm cross-linked styrene beads (Soken Chemical Co., Ltd.)
11 parts by mass of methyl ethyl ketone / cyclohexa
Dispersed in non-mixed solvent (mass ratio 6/4), solid content
An 11 mass% dispersion was prepared. Dispersion, cellulose
Triacetate film (TD-80U, Fuji Photo Film)
Rum Co., Ltd.) so that the dry film thickness is 2.0 μm
Applied. After drying, it was irradiated with ultraviolet rays of 140 mJ. Furthermore
In addition, the ultraviolet curable resin (DPHA, whose refractive index is 1.54)
100 parts by mass of Nippon Kayaku Co., Ltd., a curing initiator (IRGA
Cure 907, manufactured by Ciba Geigy) 3 parts by mass, first transparent
Refractive index of 1.61 and particle size of 3.5μm
6 parts by mass of cross-linked styrene beads (manufactured by Soken Chemical Co., Ltd.),
And a refractive index of 1.61 as the second translucent fine particles, a particle size
Is 1.3 μm cross-linked styrene beads (Soken Chemical Co., Ltd.)
16 parts by mass of methyl ethyl ketone / cyclohexanone
(Mass ratio 6/4) dispersed to a solid content of 22% by mass
A dispersion was prepared. Disperse the dispersion on top of the first layer to form a dry film.
It was applied to a thickness of 3.0 μm. 160W after drying
/ Cm air-cooled metal halide lamp (eye graphic
Illuminance 400 mW / cm ², Irradiation
Amount 300mJ / cm²The coating layer is cured by irradiating ultraviolet rays of
Let In this way, the light diffusion layer was formed. JIS
-Measurement device according to K-7105 (Murakami Color Research Laboratory)
Manufactured by HR-100) to measure haze.
As a result, it was 56%.

A heat-crosslinkable fluoropolymer having a refractive index of 1.42 (JN-7228, manufactured by JSR Corporation) in 2240 g of methyl ethyl ketone solution (solid content concentration 6% by mass) had an average particle diameter of 10 to 20 nm and a solid content of 10 to 20 nm. S with a concentration of 30% by mass
Methyl ethyl ketone dispersion of iO ₂ sol (MEK-S
T, Nissan Chemical Co., Ltd.) 192 g, methyl ethyl ketone 2224 g, and cyclohexanone 144 g,
After stirring, the mixture was filtered through a polypropylene filter (PPE-01) having a pore size of 1 μm to prepare a coating liquid for low refractive index layer. Using a bar coater the coating liquid for the low refractive index layer,
After coating on the light diffusion layer and drying at 80 ° C, another 12
Thermal crosslinking was performed at 0 ° C. for 8 minutes to form a low refractive index layer having a thickness of 0.096 μm. In this way, a transparent protective film functioning as a light diffusion film with a low refractive index layer was produced.

(Production of Polarizing Plate on Viewing Side) Iodine was adsorbed on a stretched polyvinyl alcohol film to produce a polarizing film. The transparent protective film that functions as a light diffusion film is saponified, and a polyvinyl alcohol adhesive is used so that the transparent support (cellulose triacetate film) of the transparent protective film that functions as a light diffusion film is on the polarizing film side. It was attached to one side of the polarizing film. Next, the transparent protective film functioning as a retardation film was saponified, and a polyvinyl alcohol-based adhesive was used to attach it to the opposite side of the polarizing film. The slow axis of the retardation film and the transmission axis of the polarizing film were arranged so as to be parallel to each other. In this way, the viewing side polarizing plate according to the present invention was produced.

(Production of Backlight-Side Polarizing Plate) Iodine was adsorbed on a stretched polyvinyl alcohol film to produce a polarizing film. Commercially available cellulose triacetate film (Fujitac TD80, Fuji Photo Film Co., Ltd.)
Saponification treatment) was applied to one side of the polarizing film using a polyvinyl alcohol adhesive. Next, a commercially available triacetyl cellulose film (Fujitac TD80,
Fuji Photo Film Co., Ltd.) was subjected to saponification treatment, and a polyvinyl alcohol-based adhesive was used to attach it to the opposite side of the polarizing film. In this way, a backlight side polarizing plate was produced.

(Production of Liquid Crystal Display Device) A pair of polarizing plates and a pair of optical compensation sheets provided in a liquid crystal display device (VL-1530S, manufactured by Fujitsu Limited) using a vertical alignment type liquid crystal cell were peeled off. . Then, the produced viewing-side polarizing plate was attached via an adhesive so that the transparent protective film functioning as a retardation film was on the liquid crystal cell side. Next, the manufactured backlight-side polarizing plate was attached to the opposite side of the liquid crystal cell via an adhesive. The crossed Nicols were arranged so that the transmission axis of the viewing-side polarizing plate was in the vertical direction and the transmission axis of the backlight-side polarizing plate was in the horizontal direction.
About the produced liquid crystal display device, a measuring instrument (EZ-Contra
st160D, manufactured by ELDIM), using black display (L
The viewing angle was measured in 8 steps from 1) to white display (L8). The results are shown in Table 1.

[Comparative Example 1] (Preparation of transparent protective film not functioning as retardation film)
A cellulose acetate film was produced in the same manner as in the preparation of the transparent protective film functioning as the retardation film of Example 2, except that the cellulose acetate solution was used as it was as a dope and no stretching treatment was performed. About the produced transparent protective film (cellulose acetate film), an ellipsometer (M-150, JASCO Corporation)
Re retardation value and Rth retardation value at a wavelength of 550 nm were measured. As a result, Re was 4 nm and Rth was 48 nm.

(Preparation of viewing-side polarizing plate) A polarizing film was prepared by adsorbing iodine on a stretched polyvinyl alcohol film, and a commercially available cellulose triacetate film (Fujitac TD80, manufactured by Fuji Photo Film Co., Ltd.) was saponified. , Using polyvinyl alcohol adhesive,
It was attached to one side of the polarizing film. Next, saponification treatment is performed on the produced transparent protective film that does not function as a retardation film,
It was attached to the opposite side of the polarizing film using a polyvinyl alcohol adhesive. In this way, a viewing side polarizing plate for comparison was prepared.

(Backlight Side Polarizing Plate) Iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizing film. A commercially available cellulose triacetate film (Fujitac TD80, manufactured by Fuji Photo Film Co., Ltd.) was saponified and attached to one side of the polarizing film using a polyvinyl alcohol adhesive. Next, a commercially available cellulose triacetate film (Fujitac TD80, manufactured by Fuji Photo Film Co., Ltd.) was subjected to a saponification treatment, and a polyvinyl alcohol-based adhesive was used to attach it to the opposite side. In this way, a backlight side polarizing plate was produced.

(Production of Liquid Crystal Display Device) A pair of polarizing plates and a pair of optical compensation sheets provided in a liquid crystal display device (VL-1530S, manufactured by Fujitsu Limited) using a vertical alignment type liquid crystal cell were peeled off. .. Then, the produced viewing-side polarizing plate was attached via an adhesive so that the transparent protective film that did not function as a retardation film was on the liquid crystal cell side. Next, the manufactured backlight-side polarizing plate was attached to the opposite side of the liquid crystal cell via an adhesive. The crossed Nicols were arranged so that the transmission axis of the viewing-side polarizing plate was in the vertical direction and the transmission axis of the backlight-side polarizing plate was in the horizontal direction.
About the produced liquid crystal display device, a measuring instrument (EZ-Contra
st160D, manufactured by ELDIM), using black display (L
The viewing angle was measured in 8 steps from 1) to white display (L8). The results are shown in Table 1.

[0109]

[Table 1] Table 1 ──────────────────────────────────── Liquid crystal contrast ratio of 10 or more Range Display with good gradation characteristics Transmission axis direction Transmission axis to transmission axis direction Transmission axis to 45 ° direction 45 ° direction ────────────────────── ─────────────── Example 1> 80 °> 80 ° 47 ° 45 ° Example 2> 80 °> 80 ° 50 ° 49 ° Example 3> 80 °> 80 ° 51 ° 50 ° Comparative Example 1> 80 ° 44 ° 20 ° 15 ° ─────────────────────────────────── (Note) Good gradation characteristics indicate angles that are equivalent to the high brightness gradations (L7, L8) at the left and right viewing angles of 20 degrees shown in the detailed description.

[Brief description of drawings]

FIG. 1 is a graph showing gray scale characteristics in a horizontal direction in a commercially available MVA mode liquid crystal display device.

FIG. 2 is a schematic sectional view showing a typical embodiment of a liquid crystal display device according to the present invention.

FIG. 3 is a schematic sectional view showing a typical form of a transparent protective film having a light diffusing function.

[Explanation of symbols]

BL Backlight 1, 3 Transparent protective film 2, 6 Polarizing film 3p, 5p Transparent protective film 4 having a function as a retardation film 4 VA mode liquid crystal cell 7d, 10 Transparent protective film having a function as a light diffusion film 10 Light Transparent protective film 20 having a diffusion function 20 Transparent support 31 Translucent resin 41 First translucent fine particles 42 Second translucent fine particles

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1335 510 G02F 1/13363 1/13363 G02B 1/10 A F term (reference) 2H042 BA02 BA12 BA14 BA20 2H049 BA02 BA06 BA27 BA42 BB03 BB18 BB19 BB22 BB33 BB43 BB63 BC03 BC12 BC22 2H091 FA08X FA08Z FA11X FA11Z FA31X FA31Z FB04 FB12 HA06 EU01 EA86 EA126 EA126 EV136 EA026A36 AZ16 AB02 AZ16 AB02 BB16 CC02 FD206 GQ05

Claims (12)

[Claims] 1. A polarizing plate comprising a polarizing film and two transparent protective films disposed on both sides of the polarizing film, wherein one transparent protective film has a Re retardation value of 20 to 70 nm and 1
A retardation film having an Rth retardation value of 50 to 400 nm, wherein the slow axis of the retardation film and the transmission axis of the polarizing film are arranged substantially parallel to each other, and A polarizing plate having a transparent protective film having a light diffusion function. 2. The polarizing plate according to claim 1, wherein the retardation film is made of cellulose acetate having a degree of acetylation of 59.0 to 61.5%. 3. The polarizing plate according to claim 2, wherein the retardation film contains 0.01 to 20 parts by mass of an aromatic compound having at least two aromatic rings with respect to 100 parts by mass of cellulose acetate. 4. The polarizing plate according to claim 1, wherein the transparent protective film having a light diffusing function comprises a transparent support and a light diffusing layer containing translucent fine particles in a translucent resin. 5. The difference between the refractive index of the transparent fine particles and the refractive index of the transparent resin is 0.02 or more and 0.15 or less.
The polarizing plate described in. 6. The polarizing plate according to claim 5, wherein the translucent fine particles have a particle size distribution having at least two peaks. 7. The method according to claim 6, wherein one peak of the particle size distribution of the translucent fine particles is in the range of 0.5 to 2.0 μm and the other peak is in the range of 2.5 to 5.0 nm. The polarizing plate described. 8. The transparent protective film having a light diffusing function is 40
The polarizing plate according to claim 1, which has a haze value of not less than%. 9. A transparent protective film having a light diffusing function,
The polarizing plate according to claim 1, further comprising a low refractive index layer having a refractive index of 1.35 to 1.45. 10. The polarizing plate according to claim 9, wherein the low refractive index layer comprises a crosslinked cured product of a composition containing a fluorine-containing compound and inorganic fine particles, which is cured by heat or ionizing radiation. 11. The low refractive index layer has a wavelength of 450 to 650.
The polarizing plate according to claim 9, which has an integrating sphere average reflectance of 2.5% or less in a range of nm. 12. A VA-mode liquid crystal cell and two polarizing plates arranged on both sides thereof, the two polarizing plates comprising:
A liquid crystal display device comprising a polarizing film and two transparent protective films disposed on both sides thereof, wherein the transparent protective film between the polarizing film on the display surface side and the liquid crystal cell is 20 to 70n.
A retardation film having a Re retardation value of m and an Rth retardation value of 150 to 400 nm, wherein the slow axis of the retardation film and the transmission axis of the polarizing film on the display surface side are substantially parallel to each other. A liquid crystal display device, characterized in that the transparent protective film provided on the display surface side has a light diffusing function.