JP2009003451A - Light diffusion film, antireflection film, polarizing plate, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize wide angle visualization of an image display device, particularly prevention of gradation inversion in the downward direction of a panel of a liquid crystal display device and reflection of outside light, and to further realize an image with no blur even in a high-definition liquid crystal display device. <P>SOLUTION: The light diffusion film including a transparent substrate and a light diffusion layer is provided, wherein the light diffusion layer has, within a range of 0.01-0.2%, a scattered light intensity at 30° to a light intensity at 0° emission angle in a scattered light profile by a goniophotometer, and the light diffusion layer comprises a light transmissive resin and light transmissive fine particles. The light transmissive fine particles have a refractive index different from that of the light transmissive resin, the light transmissive resin has a refractive index of 1.51-2.00, and the difference between the refractive index of the light transmissive fine particles and that of the light transmissive resin is 0.02-0.20. The light diffusion layer has, within a range of ≤0.02%, a scattered light intensity at 60° to a light intensity at 0° emission angle in the scattered light profile by the goniophotometer, and the light diffusion layer has a total haze value within a range of 40-90%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light diffusion film having a transparent substrate and a light diffusion layer. The present invention also relates to an antireflection film having a transparent substrate, a light diffusion layer, and a low refractive index layer in this order. Furthermore, the present invention also relates to a polarizing plate in which protective films are provided on both sides of the polarizing film. Furthermore, the present invention also relates to an image display device using a light diffusion film, an antireflection film or a polarizing plate.

In general, a liquid crystal display device is composed of a polarizing plate and a liquid crystal cell. A drawback in the display quality of the liquid crystal display device is a viewing angle and reflection of external light.
Regarding the viewing angle, in the TN mode TFT liquid crystal display devices which are currently mainstream, an optical compensation film is inserted between the polarizing plate and the liquid crystal cell as described in Patent Documents 1 to 3, and the liquid crystal display device having an extremely wide viewing angle. Is realized. However, the liquid crystal display device still has a problem that gradation inversion in the lower direction of the panel occurs.
With respect to this problem, the light diffusion means is provided in Patent Document 4, the optical axis conversion plate is provided in Patent Document 5, and the optical means for diffusing outgoing light is provided in Patent Document 6 on the viewing side surface. It has been proposed that display quality be improved. However, the specific means described in these are light diffusion means having a highly controlled lens structure or diffractive structure, and are expensive and very difficult to mass-produce.

Patent Documents 7 and 8 disclose a light diffusion film that is inexpensive and can be mass-produced by coating a resin containing a filler (eg, silicon dioxide (silica)) on the surface of a transparent substrate film. Yes. Patent Documents 9 to 14 disclose other light diffusion films. Even when these light diffusion films are used, the display quality is not sufficiently improved.
In recent years, liquid crystal display devices are often used for high-definition monitor applications with fine pixels. When the light diffusing film is used in a high-definition monitor, another major problem is that the image is likely to be blurred.

On the other hand, for reflection of external light, an antireflection film is generally used. The antireflection film is disposed on the outermost surface of the display that reduces the reflectivity by using the principle of optical interference in order to prevent contrast degradation and image reflection due to reflection of external light. However, the conventional antireflection film cannot solve the above-described viewing angle problem, and an antireflection film that is excellent in reflection of external light and that can solve the viewing angle problem is desired. It was.
JP-A-8-50206 Japanese Patent Laid-Open No. 7-191217 European Patent 0911656A2 Japanese Patent No. 2822983 JP 2001-33783 A JP 2001-56461 A JP-A-6-18706 Japanese Unexamined Patent Publication No. 10-20103 JP-A-11-160505 Japanese Patent Laid-Open No. 11-305010 JP 11-326608 A JP 2000-121809 A JP 2000-180611 A JP 2000-338310 A

An object of the present invention is to highly realize a wide viewing angle of a liquid crystal display device, in particular, gradation inversion in the lower direction of the panel and prevention of reflection of external light.
Another object of the present invention is to realize an image that is not stunned even in a high-definition liquid crystal display device.
Furthermore, an object of the present invention is to increase the viewing angle (particularly the downward viewing angle) without increasing the thickness of the liquid crystal panel.
Still another object of the present invention is to prevent the occurrence of contrast reduction, gradation or black-and-white reversal, or hue change due to a change in viewing angle.

The object of the present invention is the following (1) to (3) light diffusion film, the following (4) to (6) antireflection film, the following (7) polarizing plate and the following (8) image display device. Achieved.
(1) A light diffusing film having a transparent base material and a light diffusing layer, wherein the light diffusing layer is in the range of 0.01 to 0.2%, and the light having an emission angle of 0 ° of the scattered light profile of the goniophotometer The light diffusing layer is made of a translucent resin and translucent fine particles, and the translucent fine particles have a refractive index different from the refractive index of the translucent resin. The light-sensitive resin has a refractive index of 1.51 to 2.00, the difference between the refractive index of the light-transmitting fine particles and the refractive index of the light-transmitting resin is 0.02 to 0.20, and the light diffusion layer However, in the range of 0.02% or less, the scattered light profile of the goniophotometer has a scattered light intensity of 60 ° with respect to the light intensity of the output angle of 0 °, the light diffusion layer is in the range of 40 to 90%, Light diffusing film with all haze values.

(2) The light diffusing film according to (1), wherein the translucent fine particles comprise fine particles having a particle size of 0.5 μm to 2.0 μm and fine particles having a particle size of 2.5 μm to 5.0 μm.
(3) The light transmissive resin of the light diffusion layer contains a monomer having a high refractive index and / or metal oxide ultrafine particles having a high refractive index together with a binder polymer having a saturated hydrocarbon or polyether as a main chain. The light diffusion film according to (1) or (2).

(4) An antireflection film having a transparent substrate, a light diffusing layer and a low refractive index layer in this order, and the light diffusing layer is in the range of 0.01 to 0.2%, and the scattering of the goniophotometer The light profile has a scattered light intensity of 30 ° with respect to the light intensity at an emission angle of 0 °, the light diffusion layer is made of a light-transmitting resin and light-transmitting fine particles, and the light-transmitting fine particles are Have different refractive indexes, the translucent resin has a refractive index of 1.51 to 2.00, and the difference between the refractive index of the translucent fine particles and the refractive index of the translucent resin is 0.02 to Further, the antireflection film has an average value in the wavelength region of 450 to 650 nm of the specular reflectance at 5 degrees incidence in the range of 2.5% or less, and the light diffusion layer is in the range of 0.2% or less. In the range of less than 02%, the light intensity of the goniophotometer's scattered light profile with an output angle of 0 ° It has a scattered light intensity of 60 ° to the light diffusion layer, 40 to a range of 90%, the anti-reflection film having a total haze value.
(5) The antireflection film according to (4), wherein the translucent fine particles comprise fine particles having a particle size of 0.5 μm to 2.0 μm and fine particles having a particle size of 2.5 μm to 5.0 μm.
(6) The light transmissive resin of the light diffusion layer contains a monomer having a high refractive index and / or metal oxide ultrafine particles having a high refractive index together with a binder polymer having a saturated hydrocarbon or polyether as a main chain. The antireflection film according to (4) or (5).

(7) A polarizing plate in which a protective film is provided on both surfaces of the polarizing film, wherein one of the protective films is the light diffusion film according to any one of (1) to (3), or (4) to (6) A polarizing plate, which is the antireflection film according to any one of (6).
(8) The light diffusing film according to any one of (1) to (3), the antireflection film according to any one of (4) to (6), or the polarizing plate according to (7) On the outermost layer of the display.

The present inventor has found that there is a correlation between the intensity distribution of scattered light measured with a goniophotometer and the effect of improving the viewing angle. The present inventor has further studied, controlled the haze value, and made an antireflection film in which a specific low refractive index layer is laminated, so that the reflection of external light and the viewing angle can be performed without sacrificing image blurring. Improved achieved.
That is, the more the light emitted from the backlight is diffused by the light diffusion film installed on the surface of the polarizing plate on the viewing side, the better the viewing angle characteristics. However, if it is diffused too much, backscattering will increase and the front brightness will decrease. Further, if the scattering is too large, there arises a problem that the image clarity is deteriorated. Therefore, it is necessary to control the scattered light intensity distribution within a certain range.

As a result of further investigation by the present inventor, in order to achieve a desired visual recognition characteristic, the scattered light intensity of 30 °, which correlates particularly with the viewing angle improvement effect, is constant with respect to the light intensity of the scattered light profile at the output angle of 0 °. It was found that it should be controlled within the range. It has also been found that from the viewpoint of image clarity, it is sufficient to control the intensity of scattered light in the 60 ° direction, which has a correlation with image blurring.
As a result, according to the present invention, a wide viewing angle of the liquid crystal display device, in particular, gradation inversion in the lower direction of the panel and prevention of reflection of external light can be realized at a high level. In addition, according to the present invention, it is possible to realize an image without any suspicion even in a high-definition liquid crystal display device. Furthermore, according to the present invention, the viewing angle (particularly the downward viewing angle) can be increased without increasing the thickness of the liquid crystal panel. Furthermore, according to the present invention, it is possible to prevent the occurrence of contrast reduction, gradation or black-and-white reversal, or hue change due to a change in viewing angle.

In the present invention, in order to achieve a desired visual recognition characteristic, the scattered light intensity at 30 °, which correlates particularly with the effect of improving the viewing angle, is 0.01 to 0.00% with respect to the light intensity at the output angle of 0 ° of the scattered light profile. Adjust to the 2% range. The scattered light intensity at 30 ° is preferably in the range of 0.02 to 0.15%, and more preferably in the range of 0.03 to 0.1%.
From the viewpoint of image clarity, it is more preferable to control the intensity of scattered light in the 60 ° direction, which has a correlation with image blurring. Specifically, the scattered light intensity at 60 ° with respect to the light intensity at an emission angle of 0 ° in the scattered light profile is preferably 0.02% or less, more preferably 0.01% or less, and Most preferably, it is 005% or less.
The scattered light profile can be measured using a commercially available automatic variable angle photometer (GP-5 type, manufactured by Murakami Color Research Laboratory Co., Ltd.) for the prepared light scattering film.

Adjustment of the haze value is also important for improving the viewing angle characteristics. The internal scattering haze is preferably 30% to 80%, more preferably 35% to 70%, and most preferably 40% to 60%.
As a method for increasing the internal scattering haze, there are methods such as increasing the concentration of particles having a particle size of 0.5 to 2.0 μm, increasing the film thickness, and further increasing the refractive index of the particles.
Apart from the internal scattering haze, it is also necessary to provide surface haze by surface irregularities from the viewpoint of visibility, and in the state where the internal scattering haze and surface haze exist, the total haze value is 40% or more. A corner improvement effect is exhibited, preferably 40% to 90%, more preferably 45% to 80%, and most preferably 50% to 70%.

[Basic structure of light diffusion film]
FIG. 1 is a schematic cross-sectional view showing the basic structure of a light diffusion film.
The light diffusion film (10) shown in FIG. 1 is formed by laminating a transparent substrate film (20), a light diffusion layer (30), and a low refractive index layer (50). The light diffusion layer (30) includes the first light-transmitting fine particles (41) and the second light-transmitting fine particles (42) in the light-transmitting resin (31). The light diffusion layer (30) may be composed of a plurality of layers.
Two or more kinds of translucent fine particles may be used.

The refractive index of the translucent resin (31) of the light diffusion layer (30) is preferably 1.51 to 2.00. The refractive index of the low refractive index layer (50) is preferably 1.35 to 1.45. The refractive index of triacetyl cellulose preferably used as the transparent substrate film (20) is 1.48.
By increasing the refractive index of the light diffusion layer, an excellent antireflection effect can be obtained even if the refractive index of the low refractive index layer is in the range of 1.35 to 1.45. When the refractive index of the light diffusion layer is too small, the antireflection effect is lowered. When the refractive index of the light diffusion layer is too large, the color of the reflected light becomes strong.

[Light diffusion layer]
A light-diffusion layer consists of translucent particle | grains and translucent resin. The scattered light profile and the haze value are adjusted by the translucent particles and the translucent resin.
In the present invention, it is preferable to use translucent fine particles having two or more particle sizes.

The two or more kinds of translucent fine particles preferably have a refractive index difference of 0.02 to 0.20 with respect to the translucent resin constituting the entire light diffusion layer. When the refractive index difference is less than 0.02, the difference in refractive index between the two is too small to obtain a light diffusion effect. When the refractive index difference is larger than 0.20, the light diffusibility is too high and the entire film is whitened. The refractive index difference is more preferably 0.03 to 0.15, and most preferably 0.04 to 0.13.
The particle size of the translucent fine particles (42) is preferably 0.5 μm to 2.0 μm. By adjusting the particle diameter, the above-described angular distribution of light scattering can be obtained.

In the present invention, it is necessary to diffuse incident light to some extent in order to improve 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.
When the particle diameter is 0.5 μm or less, the effect of scattering is great and the viewing angle characteristics are dramatically improved, but the backscattering becomes large and the brightness is drastically reduced. On the other hand, when the thickness is 2.0 μm or more, the scattering effect is reduced and the improvement in viewing angle characteristics is reduced. Accordingly, the particle diameter is preferably 0.6 μm to 1.8 μm, and most preferably 0.7 μm to 1.7 μm.

Further, the particle diameter of the translucent fine particles (41) is preferably 2.5 μm to 5.0 μm. Thereby, surface scattering suitable for the present invention can be obtained.
In order to achieve good display quality, it is also necessary to prevent reflection of external light.
The lower the haze value of the surface, the smaller the blurring of the display and the clear display can be obtained. However, when the haze value is too low, reflection and sparkle that is called surface glare (scintillation) occur. Conversely, if it is too high, it becomes whitish (whitening; black density reduction), and the surface haze value hs is preferably 0.5 <hs <30, more preferably 3 ≦ hs ≦ 20, and most preferably 7 ≦ hs ≦ 15.
In order to control this surface haze value, it is used as a preferable form to provide moderate unevenness on the surface of the resin layer with fine particles. The haze value (cloudiness value) can be measured using HR-100 manufactured by Murakami Color Research Laboratory according to JIS-K-7105.

When the particle diameter is 2.5 μm or less, the surface unevenness becomes small, the effect of surface scattering is small, and reflection due to external light cannot be sufficiently suppressed. On the other hand, when the thickness is 5.0 μm or more, the surface unevenness becomes large and the reflection is suppressed, but it is markedly whitened and the display quality is lowered. Accordingly, the particle diameter is preferably 2.2 μm to 4.7 μm, and most preferably 2.4 μm to 4.5 μm.
The surface roughness is preferably 1.2 μm or less, more preferably 0.8 μm or less, and most preferably 0.5 μm or less. The surface roughness can be measured using an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.).

  By using two or more kinds of light-transmitting fine particles having different particle diameters and mixing the light-transmitting fine particles, the viewing angle characteristics related to display quality and the reflection of external light are each independently provided. It is possible to optimize and fine setting is possible by the mixing ratio of the light-transmitting fine particles, and control is possible as compared with the case of one type, and various designs are facilitated.

The translucent fine particles (41) and (42) may be monodispersed organic fine particles or inorganic fine particles. As the particle size is not more varied, the scattering characteristics are less varied, and the haze value can be easily designed.
As the translucent fine particles, plastic beads are preferred, and those having particularly high transparency and a difference in refractive index from the translucent resin are preferred.
As organic fine particles, polymethyl methacrylate beads (refractive index 1.49), acrylic-styrene copolymer beads (refractive index 1.54), melamine beads (refractive index 1.57), polycarbonate beads (refractive index 1.57). ), Styrene beads (refractive index 1.60), cross-linked polystyrene beads (refractive index 1.61), polyvinyl chloride beads (refractive index 1.60), benzoguanamine-melamine formaldehyde beads (refractive index 1.68), etc. It is done.
As the inorganic fine particles, silica beads (refractive index 1.44), alumina beads (refractive index 1.63) and the like are used.

  As described above, the particle size of the light-transmitting fine particles may be appropriately selected from 0.5 to 5 μm, and may be contained in an amount of 5 to 30 parts by mass with respect to 100 parts by mass of the light-transmitting resin.

  In the case of the above translucent fine particles, since the translucent fine particles are likely to settle in the resin composition (translucent resin), an inorganic filler such as silica may be added to prevent sedimentation. . As the amount of the inorganic filler added increases, it is more effective in preventing the sedimentation of the translucent fine particles, but adversely affects the transparency of the coating film. Therefore, preferably, an inorganic filler having a particle size of 0.5 μm or less is contained in an amount of less than about 0.1% by mass so as not to impair the transparency of the coating film with respect to the translucent resin.

As the translucent resin, there are three types of resins that are mainly cured by ultraviolet rays and electron beams, that is, an ionizing radiation curable resin, a mixture of an ionizing radiation curable resin and a thermoplastic resin and a solvent, and a thermosetting resin. Is done. The thickness of the light diffusion layer is usually about 0.5 μm to 50 μm, preferably 1 μm to 20 μm, more preferably 2 μm to 10 μm, and most preferably 3 μm to 7 μm.
The refractive index of the translucent resin is preferably 1.51 to 2.00, more preferably 1.51 to 1.90, still more preferably 1.51 to 1.85, and particularly preferably. 1.51-1.80. In addition, the refractive index of translucent resin is the value measured without including translucent fine particles.
When the refractive index is too small, the antireflection property is lowered. Furthermore, when this is too large, the color of reflected light becomes strong, which is not preferable.

  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. The binder is preferably crosslinked. The polymer having a saturated hydrocarbon as the 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 monomers having two or more ethylenically unsaturated groups include esters of polyhydric alcohols and (meth) acrylic acid (eg, ethylene glycol di (meth) acrylate, 1,4-dichlorohexane diacrylate, penta Erythritol 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 Examples include 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone), vinyl sulfone (eg, divinyl sulfone), acrylamide (eg, methylenebisacrylamide) and methacrylamide. included. Among these, acrylate or methacrylate monomers having at least three functional groups, and further acrylate monomers having at least five functional groups are preferable from the viewpoint of film hardness, that is, scratch resistance. A mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate is commercially available and is particularly preferably used.

  These monomers having an ethylenically unsaturated group can be cured by a polymerization reaction by ionizing radiation or heat after being dissolved in a solvent, coated and dried together with various polymerization initiators and other additives.

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 the reaction of a crosslinkable group. Examples of the crosslinkable functional group include isocyanate group, epoxy group, aziridine group, oxazoline group, aldehyde group, carbonyl group, hydrazine group, carboxyl group, methylol group and active methylene group. Vinylsulfonic 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. A functional group that exhibits crosslinkability as a result of the decomposition reaction, such as a block isocyanate group, may be used. That is, in the present invention, the crosslinkable functional group may not react immediately but may exhibit reactivity as a result of decomposition.
The binder having these crosslinkable functional groups can form a crosslinked structure by heating after coating.

The translucent resin is preferably formed from a monomer having a high refractive index and / or metal oxide ultrafine particles having a high refractive index in addition to the binder polymer.
Examples of the high refractive index monomer include bis (4-methacryloylthiophenyl) sulfide, vinyl naphthalene, vinyl phenyl sulfide, 4-methacryloxyphenyl-4′-methoxyphenyl thioether and the like.
Examples of the metal oxide ultrafine particles having a high refractive index include a particle diameter of 100 nm or less, preferably 50 nm or less, made of at least one oxide selected from zirconium, titanium, aluminum, indium, zinc, tin, and antimony. It is preferable to contain fine particles. The metal oxide ultrafine particles having a high refractive index are preferably oxide ultrafine particles of at least one metal selected from Al, Zr, Zn, Ti, In and Sn. Specific examples include ZrO ₂ , TiO ₂ , _{al 2 O 3, In 2 O} 3, ZnO, SnO 2, Sb 2 O 3, ITO , and the like. Among these, ZrO ₂ is particularly preferably used.
The addition amount of the high refractive index monomer and the metal oxide ultrafine particles is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, based on the total mass of the translucent resin.

  When the translucent resin and the transparent substrate film are in contact with each other, the solvent of the coating solution for forming the translucent resin is used to achieve both the antiglare property and the adhesion between the support and the antiglare layer. The transparent base film (for example, triacetyl cellulose support) is dissolved in at least one solvent and the transparent base film is not dissolved in at least one solvent. More preferably, at least one of the solvents that do not dissolve the transparent base film has a higher boiling point than at least one of the solvents that dissolve the transparent base film. More preferably, the difference in boiling point temperature between the solvent having the highest boiling point among the solvents that do not dissolve the transparent substrate film and the solvent having the highest boiling point among the solvents that dissolve the transparent substrate film is 30 ° C. or more. Yes, most preferably 50 ° C. or higher.

As a solvent for dissolving the transparent substrate film (preferably triacetyl cellulose):
Ethers having 3 to 12 carbon atoms: Specifically, dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, 1,3-dioxolane, 1,3,5- Trioxane, tetrahydrofuran, anisole and phenetole;
Ketones having 3 to 12 carbon atoms: specifically, acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, and methylcyclohexanone;
Esters having 3 to 12 carbon atoms: specifically, ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, propion brewed ethyl, n-pentyl acetate, and γ-ptyrolactone;
Organic solvent having two or more kinds of functional groups: Specifically, 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, and ethyl acetoacetate;
Is mentioned.
These can be used alone or in combination of two or more. The solvent for dissolving the transparent substrate is preferably a ketone solvent.

As a solvent that does not dissolve the transparent base film (preferably triacetyl cellulose), methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl- Examples include 2-butanol, cyclohexanol, isobutyl acetate, methyl isobutyl ketone, 2-octanone, 2-pentanone, 2-hexanone, 2-heptanone, 3-pentanone, 3-heptanone, and 4-heptanone.
These can be used alone or in combination of two or more.

  The mass ratio (A / B) of the total amount (A) of the solvent that dissolves the transparent substrate film and the total amount (B) of the solvent that does not dissolve the transparent substrate film is preferably 5/95 to 50/50, more preferably It is 10 / 90-40 / 60, More preferably, it is 15 / 85-30 / 70.

  As a curing method of the ionizing radiation curable resin composition as described above, the ionizing radiation curable resin composition can be cured by a normal curing method, that is, irradiation with an electron beam or ultraviolet rays.

  For example, in the case of electron beam curing, 50 to 1000 KeV emitted from various electron beam accelerators such as a Cockrowalton type, a bandegraph type, a resonant transformation type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type. Preferably, an electron beam having an energy of 100 to 300 KeV is used, and in the case of ultraviolet curing, ultraviolet rays emitted from rays of ultra-high pressure mercury lamp, high pressure mercury lamp, low pressure mercury lamp, carbon arc, xenon arc, metal halide lamp, etc. are used. it can.

[Low refractive index layer]
The low refractive index layer is provided as an antireflection layer in the outermost layer on the side where the light diffusion layer is provided on the support for the purpose of imparting antireflection ability.
The refractive index of the low refractive index layer is preferably 1.35 to 1.45 as described above.
The refractive index of the low refractive index layer preferably satisfies the following formula (I).
(Mλ / 4) × 0.7 <n1d1 <(mλ / 4) × 1.3 Expression (I)
In the formula, m is a positive odd number (generally 1), n1 is the refractive index of the low refractive index layer, and d1 is the film thickness (nm) of the low refractive index layer. Further, λ is the wavelength of visible light, and is a value in the range of 450 to 650 (nm).
In addition, satisfy | filling said numerical formula (I) means that m (positive odd number, usually 1) which satisfy | fills numerical formula (I) exists in the said wavelength range.

For the low refractive index layer of the present invention, a fluorine-containing resin obtained by curing a thermosetting or ionizing radiation-curable crosslinkable fluorine-containing compound is used. Thereby, compared with the low refractive index layer using magnesium fluoride or calcium fluoride, it is excellent in scratch resistance even when used as the outermost layer. The refractive index of the thermosetting or ionizing radiation curable crosslinkable fluorine-containing compound is preferably 1.35 or more and 1.45 or less. The dynamic friction coefficient of the cured fluororesin is preferably 0.03 to 0.15, and the contact angle with water is preferably 90 to 120 degrees.
Examples of such crosslinkable fluorine-containing compounds include perfluoroalkyl group-containing silane compounds (for example, (heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane), fluorine-containing monomers and crosslinkable groups. Examples thereof include a fluorine-containing copolymer having a monomer for imparting as a structural unit.

  Specific examples of the fluorine-containing monomer unit include, for example, fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole, etc. ), (Meth) acrylic acid partial or fully fluorinated alkyl ester derivatives (for example, Biscoat 6FM (manufactured by Osaka Organic Chemicals) and M-2020 (manufactured by Daikin)), fully or partially fluorinated vinyl ethers, and the like.

  As a monomer for imparting a crosslinkable group, in addition to a (meth) acrylate monomer having a crosslinkable functional group in the molecule in advance such as glycidyl methacrylate, it has a carboxyl group, a hydroxyl group, an amino group, a sulfonic acid group, etc. ) Acrylate monomers (for example, (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate, etc.). JP-A-10-25388 and JP-A-10-147739 disclose that the latter can introduce a crosslinked structure after copolymerization.

Further, in 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 other monomers may be used.
Other monomers that may be copolymerized are not particularly limited. For example, olefins (ethylene, propylene, isoprene, vinyl chloride, vinylidene chloride, etc.), acrylic esters (methyl acrylate, methyl acrylate, ethyl acrylate) , 2-ethylhexyl acrylate), methacrylates (methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene glycol dimethacrylate, etc.), styrene derivatives (styrene, divinylbenzene, vinyltoluene, α-methylstyrene, etc.), Vinyl ethers (methyl vinyl ether, etc.), vinyl esters (vinyl acetate, vinyl propionate, vinyl cinnamate, etc.), acrylamides (N-tert-butylacrylamide, N-cyclohexylacrylamide, etc.), methacrylate Amides, acrylonitrile derivatives, and the like.

In order to impart scratch resistance to the fluorine-containing resin used for the low refractive index layer, Si oxide ultrafine particles having an average particle diameter of preferably 0.1 μm or less, more preferably 0.001 to 0.05 μm are added. And preferably used. From the viewpoint of antireflection properties, the lower the refractive index, the better. However, 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 Si oxide ultrafine particles, it is possible to find the best point of the balance between scratch resistance and low refractive index.
As the ultrafine particles of Si, 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.

Antireflection film is perpendicular peeling electrification measured at normal temperature and normal humidity for either triacetyl cellulose (TAC) or polyethylene terephthalate (PET) is in -200Pc ^{(picocoulomb)} / cm 2 ~ + ^200pc (picocoulomb) / cm ² Preferably there is. More preferably ^{-100pc / cm 2 ~ + 100pc /} cm 2, more preferably from ^{-50pc / cm 2 ~ + 50pc /} cm 2, and most preferably 0pc / cm ^2. Here, the unit pc (picocoulomb) is 10 ⁻¹² coulomb.
More preferably, the vertical peel charge measured at room temperature of 10% RH is −100 pc / cm ² to +100 pc / cm ² , more preferably −50 pc / cm ² to +50 pc / cm ² , most preferably 0 pc / cm ^{2. 2} .

The measurement method of the vertical peeling charge is as follows.
The measurement sample is left in advance for 2 hours or more in an environment of measurement temperature and humidity. The measuring device is composed of a table on which a measurement sample is placed and a head that can hold a partner film and can repeatedly press and peel the measurement sample from above, and an electrometer for measuring the amount of charge is connected to the head. The antiglare and antireflection film to be measured is placed on a table, and TAC or PET is attached to the head. After neutralizing the measurement portion, the head is pressure-bonded to the measurement sample and peeled off repeatedly, and the charge values at the first peeling and the fifth peeling are read and averaged. This is repeated for three samples by changing the sample, and the average of all the samples is defined as vertical peeling charge.

Depending on the type of the counterpart film and the measurement sample, there are cases where it is positively charged and negatively charged, but the problem is the size of the absolute value.
In general, the absolute value of charging is larger in a low humidity environment. The absolute value of the antiglare antireflection film of the present invention is also small.

The antireflection film is excellent in dust resistance because the absolute value of the vertical peeling charge at normal temperature and humidity and normal temperature of 10% RH is small.
In order to set the value of the vertical peeling charge within the above range, the ratio of various elements on the surface of the antireflection film is adjusted.

The surface resistance value of the antireflection film is 1 × 10 ¹¹ Ω / □ or more, preferably 1 × 10 ¹² Ω / □ or more. The measuring method of the surface resistance value is a circular electrode method described in JIS. That is, the current value one minute after voltage application is read to determine the surface resistance value (SR).
In the present invention, the idea is fundamentally different from the method of improving the dust resistance (dust adhesion preventing property) by reducing the surface resistance value, for example, 1 × 10 ¹⁰ Ω / □ or less. This method is not adopted because the image display quality is deteriorated. In the present invention, the absolute value of the vertical peeling charge is reduced by the above-described method. Therefore, it is not necessary to reduce the surface resistance value, and the surface resistance value is 1 × 10. ¹¹ Ω / □ or more can be achieved, and the image display quality does not deteriorate.

In the antireflection film, the average value of the specular reflectance at 5 ° incidence in the wavelength region from 450 nm to 650 nm is 2.5% or less, preferably 1.2% or less, more preferably 1.1% or less. is there.
Moreover, it is preferable that the average value in the wavelength region from 450 nm to 650 nm of the integrated reflectance at 5 degrees incidence is 2.5% or less, and more preferably 2.3% or less.

The specular reflectance at 5 degrees incidence and the 5 degrees incidence will be described.
The specular reflectivity at 5 degrees incidence is a ratio of the intensity of light reflected at -5 degrees normal to the incident light from the normal direction +5 degrees of the sample, and is a measure of reflection due to specular reflection of the background. When applied to an antiglare and antireflection film, the intensity of light reflected at −5 degrees in the normal direction is reduced by the amount of scattered light caused by surface irregularities provided for imparting antiglare properties. Therefore, specular reflectance can be said to be a measurement method that reflects the contribution of both antiglare and antireflection properties.

On the other hand, the integrated reflectance at 5 degrees incidence is the ratio of the integrated value of the intensity of light reflected in all directions with respect to the light incident from the normal direction of the sample +5 degrees. When applied to an antireflection film, the reflection light is not reduced due to the antiglare property, and therefore, measurement that reflects only the antireflection property is possible.
Therefore, by setting the average values of both the reflectances in the wavelength region from 450 nm to 650 nm to 2.5% or less (specular reflectance) and 2.5% or less (integral reflectance), respectively, antiglare And antireflection properties can be satisfied at the same time.

When the average value of the specular reflectance in the wavelength region from 450 nm to 650 nm at 5 degrees incidence of the antireflection film exceeds 2.5%, the reflection of the background becomes a concern, and when applied to the surface film of a display device Visibility is reduced.
On the other hand, if the average value in the wavelength region from 450 nm to 650 nm of the integrated reflectance at 5 ° incidence of the antireflection film exceeds 2.5%, the effect of improving the contrast of the display device is reduced, and the antiglare property is imparted. The display screen is whitened by the scattered light caused by the surface unevenness of the surface, and the display quality of the display device is lowered.

The antireflection film has a LIE when the color of the specularly reflected light with respect to the incident light of 5 degrees from the CIE standard light source D65 is quantified by L *, a *, and b * values in the CIE 1976 L * a * b * color space. It is preferably designed to fall within the ranges of * ≦ 10, 0 ≦ a * ≦ 2, and −5 ≦ b * ≦ 2. The color of the regular reflection light that satisfies this is a neutral color.
The color of the specularly reflected light with respect to 5 ° incident light of the CIE standard light source D65 is obtained by calculating the product of the measured value of the specular reflectance in the wavelength range of 380 nm to 780 nm and the spectral distribution of each light source D65 at 5 ° The obtained spectral reflection spectrum can be quantified by calculating the L * value, a * value, and b * value of the CIE1976 L * a * b * color space, respectively.
When the L * value is larger than 10, the antireflection property is not sufficient. If the a * value is larger than 2, the red uneven color of the reflected light is strong, and if it is less than 0, the green color is strong. Further, when the b * value is less than −5, the bluish color is strong, and when it is larger than 2, the yellow color is strong, which is not preferable.

An antireflection film having such a neutral-colored reflected light and having a low reflectance can optimize the balance between the refractive index of the low refractive index layer and the refractive index of the binder material of the antiglare layer. can get.
In general, an antireflection film using an optical thin film formed by vapor deposition or sputtering of three or more layers can reduce the average value of the specular reflectance to 0.3% or less, and thus the L * value can also be reduced to 3 or less. Is 10 or more and the b * value is less than −10, and the color of the reflected light is very strong. However, in the antiglare antireflection film of the present invention, the color of the reflected light is high. Greatly improved.

[Transparent substrate]
Examples of the transparent base material include a transparent resin film, a transparent resin plate, a transparent resin sheet, and transparent glass. Examples of transparent resin films include triacetyl cellulose (TAC) film (refractive index 1.48), polyethylene terephthalate (PET) film, diacetylene cellulose film, acetate butyrate cellulose film, polyether sulfone film, and polyacrylic resin film. Polyurethane resin film, polyester film, polycarbonate film, polysulfone film, polyether film, polymethylpentene film, polyether ketone film, (meth) acrylonitrile film, and the like can be used. The thickness is usually about 25 μm to 1000 μm.
Since the transparent substrate is used on the outermost surface of the polarizing plate, it is preferable to use a cellulose acetate film that is generally used as a protective film for the polarizing plate.
As the transparent substrate film of the light scattering film, a cellulose acetate film having high transparency and a smooth surface is preferable.

In the present invention, it is particularly preferable to use cellulose acetate having an acetylation degree of 59.0 to 61.5% for the transparent base film.
The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).
The viscosity average polymerization degree (DP) of the cellulose ester is preferably 250 or more, and more preferably 290 or more.
The cellulose ester used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, 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.

In general, the 2, 3, and 6 hydroxyl groups of cellulose acylate are not evenly distributed by 1/3 of the total substitution degree, and the substitution degree of the 6-position hydroxyl group tends to be small. In the present invention, it is preferable that the substitution degree of the 6-position hydroxyl group of cellulose acylate is larger than that of the 2- and 3-positions.
The hydroxyl group at the 6-position with respect to the total substitution degree is preferably substituted with 32% or more of an acyl group, more preferably 33% or more, and particularly preferably 34% or more. Furthermore, the substitution degree of the 6-position acyl group of cellulose acylate is preferably 0.88 or more.
The 6-position hydroxyl group may be substituted with a propionyl group, butyroyl group, valeroyl group, benzoyl group, acryloyl group or the like, which is an acyl group having 3 or more carbon atoms, in addition to the acetyl group. The degree of substitution at each position can be determined by NMR.
As the cellulose acylate of the present invention, “0043” to “0044” “Example” [Synthesis Example 1], “0048” to “0049” [Synthesis Example 2], and “0051” to “0051” described in JP-A No. 11-5851. The cellulose acetate obtained by the method of “0052” [Synthesis Example 3] can be used.

It is preferable to produce a cellulose acetate film by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which cellulose acetate is dissolved in an organic solvent.
The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain.
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 types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms 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 of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogenated hydrocarbon hydrogen atoms substituted with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is 40 to 60 mol%, and most preferably. Methylene chloride is a representative halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.

A cellulose acetate solution can be prepared by a general method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (room temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent. Non-chlorinated solvents can also be used, and examples thereof include those described in the published technical report 2001-1745.
The amount of cellulose acetate is adjusted so that it is contained in an amount of 10 to 40% by mass in the resulting solution. The amount of cellulose acetate is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).
The solution can be prepared by stirring cellulose acetate and an organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, cellulose acetate and an organic solvent are placed in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., more preferably 80 to 110 ° C.

Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component 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. The entire container can also be heated 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 stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.
Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in the container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, cellulose acetate can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a cellulose acetate with a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method.
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 the mixture at 10 to 40% by mass. The amount of cellulose acetate is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

The mixture is then cooled 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, and most preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate 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 to the final cooling temperature.

Furthermore, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), cellulose acetate is dissolved in the organic solvent. The temperature can be raised by simply leaving it at room temperature or in a warm bath.
The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second 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 until the final heating temperature is reached. .
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 determined by merely observing the appearance of the solution with the naked eye.

In the cooling dissolution method, it is desirable to use an airtight container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.
In addition, according to differential scanning calorimetry (DSC), a 20 mass% solution obtained by dissolving cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) in methyl acetate by a cooling dissolution method was 33. There exists a quasi-phase transition point between a sol state and a gel state in the vicinity of ° C., and a uniform gel state is obtained below this temperature. Therefore, it is necessary to keep this solution at a temperature equal to or higher than the pseudo phase transition temperature, preferably about 10 ° C. plus the gel phase transition temperature. However, this pseudo phase transition temperature varies depending on the degree of acetylation of cellulose acetate, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.

A cellulose acetate film is produced from the prepared cellulose acetate solution (dope) by a solvent cast method.
The dope is cast on a drum or band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.
The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried by high-temperature 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, it is possible to shorten the time from casting to stripping. 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 acylate solution (dope) can be used to form a film by casting two or more layers. In this case, it is preferable to produce a cellulose acylate film by a solvent cast 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 10 to 40%. The surface of the drum or band is preferably finished in a mirror state.

  When casting a plurality of cellulose acylate liquids of two or more layers, it is possible to cast a plurality of cellulose acylate solutions, and cellulose is supplied from a plurality of casting openings provided at intervals in the traveling direction of the support. Films may be produced while casting and laminating solutions containing acylates. For example, the methods described in JP-A Nos. 61-158414, 1-122419, 11-198285, etc. Can be adapted. Further, it may be formed into a film by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, It can be carried out by the methods described in JP-A-61-104813, JP-A-61-158413, JP-A-6-134933. Further, a cellulose acylate film flow in which a flow of a high-viscosity cellulose acylate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acylate solution and the high- and low-viscosity cellulose acylate solutions are simultaneously extruded. The extending method may be used.

Alternatively, using two casting ports, the film cast on the support is peeled off by the first casting port, and the second casting is performed on the side that is in contact with the support surface, so that the film is removed. For example, it is a method described in Japanese Patent Publication No. 44-20235.
The cellulose acylate solutions to be cast may be the same solution or different cellulose acylate solutions, and are not particularly limited. In order to give a function to a plurality of cellulose acylate layers, a cellulose acylate solution corresponding to the function may be extruded from each casting port.
Furthermore, the cellulose acylate solution can be cast by simultaneously casting other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer).

  In a single-layer solution, it is necessary to extrude a high-concentration and high-viscosity cellulose acylate solution to obtain the required film thickness. In this case, the stability of the cellulose acylate solution is poor and solids are generated. In many cases, however, it becomes a problem due to a failure or poor flatness. As a solution to this problem, by casting multiple cellulose acylate solutions from the casting port, it is possible to extrude a highly viscous solution onto the support at the same time, producing a flat film with improved flatness. Not only can this be achieved, but also the use of a concentrated cellulose acylate solution can achieve a reduction in drying load and increase the production speed of the film.

A plasticizer can be added to the cellulose acetate film in order to improve mechanical properties or increase the drying rate. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.
The addition amount of the plasticizer is preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass of the amount of the cellulose ester.

  A degradation inhibitor (eg, antioxidant, peroxide decomposer, radical inhibitor, metal deactivator, acid scavenger, amine) may be added to the cellulose acetate film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent 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. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the added amount exceeds 1% by mass, bleeding-out (bleeding) of the deterioration preventing agent to the film surface may be observed. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

The cellulose acetate film is preferably subjected to a surface treatment. Specific examples include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. In addition, as described in JP-A-7-333433, it is preferable to provide an undercoat layer.
From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film in these treatments is preferably Tg or less, specifically 150 ° C. or less.
When used as a transparent protective film of a polarizing plate, it is particularly preferable to carry out acid treatment or alkali treatment, that is, saponification treatment on cellulose acetate, from the viewpoint of adhesiveness with the polarizing film.
The surface energy is preferably 55 mN / m or more, and more preferably 60 mN / m or more and 75 mN / m or less.

Hereinafter, the alkali saponification treatment will be specifically described as an example.
The film surface is preferably immersed in an alkaline solution, neutralized with an acidic solution, washed with water and dried.
Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution, and the prescribed concentration of hydroxide ions is preferably 0.1N to 3.0N, and more preferably 0.5N to 2.0N. preferable. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably 40 ° C to 70 ° C.
From the viewpoint of productivity, it is preferable to apply an alkali solution and remove the alkali from the film surface by washing with water after saponification treatment. From the viewpoint of wettability, the coating solvent is preferably an alcohol such as IPA, n-butanol, methanol, and ethanol, and it is preferably used to add water, propylene glycol, ethylene glycol, or the like as an alkali dissolution aid.
The surface energy of a solid can be determined by a contact angle method, a wet heat method, and an adsorption method as described in “Basics and Applications of Wetting” (issued by Realize 1989.12.10). In the case of the cellulose acetate film of the present invention, the contact angle method is preferably used.
Specifically, two types of solutions having known surface energies are dropped on a cellulose acetate film, and at the intersection of the surface of the droplet and the surface of the film, the angle formed by the tangent line drawn on the droplet and the surface of the film The surface angle of the film can be calculated by defining the angle containing the droplet as the contact angle.

[Optically anisotropic layer made of liquid crystal compound]
The liquid crystal compound used in the optically anisotropic layer may be a rod-like liquid crystal or a discotic liquid crystal, and these are high molecular liquid crystals or low molecular liquid crystals, and further, low molecular liquid crystals are crosslinked and no longer exhibit liquid crystallinity. Including. Most preferred as the liquid crystalline compound of the present invention is a discotic liquid crystal.

  Preferable examples of the rod-like liquid crystal include those described in JP 2000-304932A. Examples of the discotic liquid crystal of the present invention include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, page 2655 (1994), and azacrown-based and phenylacetylene-based macrocycles. The discotic liquid crystal generally has a structure in which these are used as a mother nucleus at the center of a molecule, and a linear alkyl group, an alkoxy group, a substituted benzoyloxy group, etc. are radially substituted as the linear chain, and the liquid crystallinity is improved. Show. However, the molecule itself is not limited to the above description as long as the molecule itself has negative uniaxiality and can give a certain orientation. Further, in the present invention, it is not necessary that the final product is formed from a discotic compound, for example, the low molecular discotic liquid crystal has a group that reacts with heat, light, or the like. As a result, it may be polymerized or cross-linked by reaction with heat, light or the like, resulting in high molecular weight and loss of liquid crystallinity. Preferred examples of the discotic liquid crystal are described in JP-A-8-50206.

  The optically anisotropic layer is a layer having birefringence made of a compound having a discotic structural unit, and the surface of the discotic structural unit is inclined with respect to the transparent support surface, and the surface of the discotic structural unit is The angle formed with the transparent support surface is preferably changed in the depth direction of the optically anisotropic layer.

  The surface angle (tilt angle) of the discotic structural unit generally increases or decreases in the depth direction of the optical anisotropic layer and with increasing distance from the bottom surface of the optical anisotropic layer. The tilt angle preferably increases with increasing distance. Further, the change in the inclination angle includes continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, and intermittent change including increase and decrease. it can. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the inclination angle includes a region that does not change, it is preferable that the inclination angle increases or decreases as a whole. Further, it is preferable that the inclination angle increases as a whole, and it is particularly preferable that the inclination angle changes continuously.

  The optically anisotropic layer is generally formed by applying a solution obtained by dissolving a discotic compound and other compounds in a solvent onto an alignment film, drying it, and then heating it to a discotic nematic phase formation temperature, and then aligning it (discotic nematic). Obtained by maintaining the phase) and cooling. Alternatively, the optically anisotropic layer is formed by applying a solution obtained by dissolving a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) in a solvent onto the alignment film, drying, and then discotic nematic. It is obtained by heating to the phase formation temperature, followed by polymerization (by irradiation with UV light, etc.) and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C, particularly preferably 70 to 170 ° C.

  For example, the tilt angle of the discotic unit on the support side can be generally adjusted by selecting a discotic compound or a material for the alignment film, or by selecting a rubbing treatment method. The inclination angle of the discotic unit on the surface side (air side) is generally selected from the discotic compound or other compounds (eg, plasticizer, surfactant, polymerizable monomer and polymer) used together with the discotic compound. Can be adjusted. Furthermore, the degree of change in the tilt angle can be adjusted by the above selection.

  As the plasticizer, surfactant and polymerizable monomer, any compound is used as long as it has compatibility with the discotic compound and can change the tilt angle of the liquid crystalline discotic compound or does not inhibit the alignment. Can also be used. Among these, polymerizable monomers (eg, compounds having a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group) are preferable. The above compound is generally used in an amount of 1 to 50% by mass (preferably 5 to 30% by mass) based on the discotic compound. Furthermore, a polyfunctional acrylate is mentioned as an example of a preferable polymerizable monomer. The number of functional groups is preferably 3 or more, and more preferably 4 or more. Most preferred is a hexafunctional monomer. A preferred example of the hexafunctional monomer is dipentaerythritol hexaacrylate. It is also possible to use a mixture of these polyfunctional monomers having different numbers of functional groups.

Any polymer can be used as the polymer as long as it is compatible with the discotic compound and can change the tilt angle of the liquid crystalline discotic compound. Examples of polymers include cellulose esters. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. The polymer is generally 0.1 to 10% by mass (preferably 0.1 to 8% by mass, particularly 0.1 to 5% by mass) based on the discotic compound so as not to inhibit the alignment of the liquid crystalline discotic compound. ).
In the present invention, the film is preferably a rubbing-treated film composed of a cellulose acetate film, an alignment film provided thereon, and a discotic liquid crystal formed on the alignment film, and the alignment film made of a crosslinked polymer.

[Alignment film]
The alignment film is a layer composed of two kinds of crosslinked polymers. Any polymer that is crosslinkable by a crosslinker can be used, even if the at least one polymer is itself a crosslinkable polymer. The alignment film is formed by reacting a polymer having a functional group or a polymer having a functional group introduced therein with light, heat, pH change, or the like; or a cross-linking that is a highly reactive compound. It can be formed by introducing a bonding group derived from a cross-linking agent between polymers using an agent and cross-linking the polymers.

  Such crosslinking is usually carried out by applying a coating liquid containing the above polymer or a mixture of a polymer and a crosslinking agent on a transparent support, followed by heating or the like. As long as it can be ensured, after the alignment film is coated on the transparent support, a cross-linking process may be performed at any stage until the final optical compensation sheet is obtained. Considering the orientation of the compound having a discotic structure (optically anisotropic layer) formed on the alignment film, it is also preferable that the compound having the discotic structure is sufficiently crosslinked after being oriented. That is, when a coating solution containing a polymer and a crosslinking agent capable of crosslinking the polymer is applied on a transparent support, after heating and drying (in general, crosslinking is performed, but when the heating temperature is low, discotic When heated to the nematic phase formation temperature, the crosslinking proceeds further), a rubbing treatment is performed to form an alignment film, and then a coating solution containing a compound having a disk-like structural unit is applied onto the alignment film, and a discotic nematic After heating above the phase formation temperature, the optical anisotropic layer is formed by cooling.

  As the polymer used in the alignment film of the present invention, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Of course, some polymers are possible. Examples of the polymer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylolacrylamide), styrene / vinyl toluene copolymer. , Polymers such as chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene and polycarbonate, and Examples of the compound include a silane coupling agent. Examples of preferred polymers are water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyville alcohol, and modified polyvinyl alcohol, and gelatin, polyville alcohol, and modified polyvinyl alcohol are preferred. Mention may be made of bil alcohol and modified polyvinyl alcohol.

Among the above polymers, polyvinyl alcohol or modified polyvinyl alcohol is preferable, and it is most preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization.
The polyvinyl alcohol has, for example, a saponification degree of 70 to 100%, generally a saponification degree of 80 to 100%, and more preferably a saponification degree of 85 to 95%. The degree of polymerization is preferably in the range of 100 to 3000. Examples of the modified polyvinyl alcohol include those modified by copolymerization (for example, COONa, Si (OX) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ COO, SO ₃ Na, C ₁₂ H _25, etc. Modified by chain transfer (for example, COONa, SH, C ₁₂ H ₂₅ etc. are introduced as modifying groups), modified by block polymerization (modified groups such as COOH, for example) , CONH ₂ , COOR, C ₆ H _5, etc. are introduced). Among these, unmodified or modified polyvinyl alcohol having a saponification degree of 80 to 100%, more preferably unmodified or alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95%.
The method for synthesizing these modified polymers, measuring the visible absorption spectrum, and determining the introduction rate y are described in detail in JP-A-8-338913.

  Specific examples of the crosslinking agent used together with the polymer such as polyvinyl alcohol include the following, and these include the above water-soluble polymers, particularly polyvinyl alcohol and modified polyvinyl alcohol (including the above-mentioned specific modified products). It is preferable when used in combination with. For example, activating aldehydes (eg, formaldehyde, glyoxal and glutaraldehyde), N-methylol compounds (eg, dimethylolurea and methyloldimethylhydantoin), dioxane derivatives (eg, 2,3-dihydroxydioxane), carboxyl groups (Eg, carbenium, 2-naphthalenesulfonate, 1,1-bispyrrolidino-1-chloropyridinium and 1-morpholinocarbonyl-3- (sulfonatoaminomethyl)), active vinyl compounds (eg, 1,- 3,5-triacryloyl-hexahydro-s-triazine, bis (vinylsulfone) methane and N, N′-methylenebis- [β- (vinylsulfonyl) propionamide]), active halogen compounds (eg, 2,4-dichloro -6-hydro Shi -S- triazine), isoxazole compounds, and dialdehyde starches, such as can be increased. These can be used alone or in combination. In view of productivity, it is preferable to use an aldehyde having a high reaction activity, particularly glutaraldehyde.

  There is no particular limitation on the cross-linking agent, and the amount of the additive added tends to improve as the moisture resistance is increased. However, 0.1 to 20% by mass is preferable, and 0.5 to 15% by mass is particularly preferable because the alignment ability as the alignment film is lowered when 50% by mass or more is added to the polymer. The alignment film of the present invention contains a certain amount of the crosslinking agent that has not reacted even after the crosslinking reaction is completed. The amount of the crosslinking agent is preferably 1.0% by mass or less in the alignment film. In particular, it is preferably 0.5% by mass or less. If the cross-linking agent is contained in the alignment film in an amount exceeding 1.0 mass, sufficient durability cannot be obtained. That is, when used in a liquid crystal display device, reticulation may occur when used for a long time or when left in a high temperature and high humidity atmosphere for a long time.

  The alignment film can basically be formed by applying an alignment film forming material, the above polymer and a transparent support containing a crosslinking agent, followed by heat drying (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be carried out at any time after coating on the transparent support. And when using water-soluble polymers, such as said polyvinyl alcohol, as an orientation film formation material, it is preferred that a coating liquid is a mixed solvent of organic solvents, such as methanol and water, which has a defoaming action, and the ratio is mass. The ratio of water: methanol is generally 0: 100 to 99: 1, preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the layer surface of an orientation film and also an optically anisotropic layer reduces remarkably. Examples of the coating method include a spin coating method, a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E type coating method. The E-type coating method is particularly preferable. The film thickness is preferably 0.1 to 10 μm. Heating and drying can be performed at 20 ° C to 110 ° C. In order to form sufficient cross-linking, 60 ° C to 100 ° C is preferable, and 80 ° C to 100 ° C is particularly preferable. The drying time can be 1 minute to 36 hours. Preferably, it is 5 minutes to 30 minutes. The pH is preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, the pH is 4.5 to 5.5, and 5 is particularly preferable.

  The alignment film is provided on the transparent support or the undercoat layer. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above. The alignment film functions to define the alignment direction of the liquid crystalline discotic compound provided thereon.

  For the rubbing treatment, a treatment method widely used as a liquid crystal alignment treatment process of the LCD can be used. That is, a method of obtaining alignment by rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are flocked on average.

[Transparent support on which optically anisotropic layer is coated]
The transparent support is not particularly limited as long as it is a plastic film having a high transmittance, but it is preferable to use cellulose acetate which is a protective film for a polarizing plate. It may be optically uniaxial or biaxial.
Since the transparent support on which the optically anisotropic layer is coated itself plays an optically important role, the Re retardation value of the transparent support of the present invention is 0 to 200 nm, and Rth retardation is used. The value is preferably adjusted to 70 to 400 nm.
When two optically anisotropic cellulose acetate films are used in the liquid crystal display device, the Rth retardation value of the film is preferably 70 to 250 nm.
When one optically anisotropic cellulose acetate film is used for the liquid crystal display device, the Rth retardation value of the film is preferably 150 to 400 nm.

The birefringence (Δn: nx−ny) of the cellulose acetate film is preferably 0.00 to 0.002. The birefringence {(nx + ny) / 2-nz} in the thickness direction of the cellulose acetate film is preferably 0.001 to 0.04.
The retardation value (Re) is calculated according to the following formula.
Retardation value (Re) = (nx−ny) × d
In the equation, nx is a refractive index in the slow axis direction in the plane of the retardation plate (maximum refractive index in the plane); ny is a refraction in a direction perpendicular to the slow axis in the plane of the retardation plate. Rate.
(II) Rth = {(nx + ny) / 2−nz} × d
Formula (II) is the refractive index in the slow axis direction (the direction in which the refractive index is maximized) in the film plane. ny is the refractive index in the fast axis direction (the direction in which the refractive index is minimum) in the film plane. nz is the refractive index in the thickness direction of the film. d is the thickness of the film whose unit is nm.

[Polarizer]
The polarizing plate comprises a polarizing film and two protective films disposed on both sides thereof. As one protective film, the light diffusion film and the antireflection film of the present invention can be used. As the other protective film, a normal cellulose acetate film may be used.
Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally manufactured using a polyvinyl alcohol film.
The transparent substrate of the light diffusing film or the slow axis of the cellulose acetate film and the transmission axis of the polarizing film are arranged so as to be substantially parallel.
It was found that the moisture permeability of the protective film is important for the productivity of the polarizing plate.
The polarizing film and the protective film are bonded together with a water-based adhesive, and the adhesive solvent is dried by diffusing in the protective film. The higher the moisture permeability of the protective film, the faster the drying and the higher the productivity. However, if the protective film is too high, moisture will enter the polarizing film depending on the usage environment (high humidity) of the liquid crystal display device. Polarization ability decreases.

The moisture permeability of the polarizing plate is determined by the thickness of the transparent substrate, polymer film (and polymerizable liquid crystal compound), free volume, hydrophilicity / hydrophobicity, and the like.
When the light diffusion film or antireflection film of the present invention is used as a protective film for a polarizing plate, the moisture permeability is preferably 100 to 1000 g / m ² · 24 hrs, more preferably 300 to 700 g / m ² · 24 hrs. preferable.
In the case of film formation, the thickness of the transparent substrate can be adjusted by lip flow rate and line speed, or stretching and compression. Since the moisture permeability varies depending on the main material to be used, it is possible to make a preferable range by adjusting the thickness.
In the case of film formation, the free volume of the transparent substrate can be adjusted by the drying temperature and time. Also in this case, moisture permeability varies depending on the main material to be used, so that a preferable range can be obtained by adjusting the free volume.
The hydrophilicity / hydrophobicity of the transparent substrate 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 lowered by adding a hydrophobic additive.
By independently controlling the moisture permeability, a polarizing plate having an optical compensation ability can be manufactured at low cost with high productivity.

In the present invention, a polarizing plate in which the light diffusing film or antireflection film of the present invention, a polarizer, and an optically anisotropic layer composed of a liquid crystalline compound are laminated in this order is preferable.
The optically anisotropic layer may be formed as a layer containing a discotic compound (discotic compound) or a rod-like liquid crystal compound on the polymer film. In the present invention, the liquid crystal compound is preferably a discotic compound. The optically anisotropic layer is preferably formed by aligning a discotic compound (or rod-shaped liquid crystal compound) and fixing the alignment state.
A discotic compound generally has a large birefringence. The discotic compound has various orientation forms. Therefore, by using a discotic compound, an optically anisotropic layer having optical properties that cannot be obtained by a conventional stretched birefringent film can be obtained. Optical anisotropic layers using a discotic compound are described in JP-A-6-214116, US Pat. Nos. 5,583,679, 5,646,703, and West German Patent 3,911,620A1.

[Image display device]
The light diffusing film, antireflection film or polarizing plate of the present invention is advantageously used in an image display device, and is preferably used as the outermost layer of the display. The image display device includes a liquid crystal display device, an organic electroluminescence display device, a plasma display panel, and a cathode tube display device. It is particularly effective when used in a liquid crystal display device.
A TN, VA, OCB, IPS, and ECB mode liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates.
In the liquid crystal display device, one optically anisotropic layer is arranged between the liquid crystal cell and one polarizing plate, or two optically anisotropic layers are arranged between the liquid crystal cell and both polarizing plates.

The liquid crystal cell is preferably in VA mode, OCB mode, or TN mode.
In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied.

  The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625) (2) Liquid crystal cell (SID97, Digest of tech. Papers (Preliminary Proceed) 28 (1997) 845 in which the VA mode is converted into a multi-domain (MVA mode) for widening the viewing angle ), (3) A liquid crystal cell in a mode (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Preliminary collections 58-59 of the Japan Liquid Crystal Society) (1998)) and (4) SURVAVAL mode liquid crystal cells (announced at LCD International 98).

  The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between the upper part and the lower part of the liquid crystal cell. It is disclosed in the specifications of Japanese Patent Nos. 45882525 and 5410422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed.

In a TN mode liquid crystal cell, rod-like liquid crystalline molecules are substantially horizontally aligned when no voltage is applied, and are twisted and aligned at 60 to 120 °.
The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.

[Example 1]
The light transmissive resin constituting the light diffusion layer is 100 parts by mass of a hard coat liquid containing silica ultrafine particle dispersion (Desolite Z7526, manufactured by JSR Corporation, refractive index 1.51), and crosslinked polystyrene beads ( 25 parts by mass of Soken Chemicals Co., Ltd., SX130H, particle size 1.3 μm, refractive index 1.61), 6 parts by mass of cross-linked polystyrene beads (SX350H, particle size 3.5 μm, refractive index 1.61) by Soken Chemical, A mixture prepared by mixing these with methyl ethyl ketone / methyl isobutyl ketone (20/80 mass ratio) to a solid content of 45% is placed on a triacetyl cellulose film (TD-80U, manufactured by Fuji Photo Film Co., Ltd.). After coating and drying the solvent so that the coating amount of 1.3 μm crosslinked polystyrene beads is 1.1 g / m ² , 160 W / cm air-cooled metal halai Using a drump (manufactured by Eye Graphics Co., Ltd.), an ultraviolet ray having an illuminance of 400 mW / cm ² and an irradiation amount of 300 mJ / cm ² was irradiated to cure the coating layer to prepare a light diffusion film A-01. The dry thickness of the light diffusion layer of this film was 3.5 μm.

(Preparation of coating solution for low refractive index layer)
MEK-ST (SiO ₂ sol methyl ethyl ketone (MEK) having an average particle size of 10 to 20 nm and a solid content concentration of 30% by mass was added to 93 g of a heat-crosslinkable fluorine-containing polymer having a refractive index of 1.42 (JN-7228, manufactured by JSR Corporation). ) Dispersion (manufactured by Nissan Chemical Co., Ltd.) 8 g and methyl ethyl ketone 100 g were added, stirred, and then filtered through a polypropylene filter having a pore size of 1 μm to prepare a coating solution for a low refractive index layer.

[Example 2]
On the light diffusion layer of the light diffusion film A-01, the coating solution for the low refractive index layer is applied using a bar coater, dried at 80 ° C., and then thermally crosslinked at 120 ° C. for 10 minutes to obtain a thickness. A low refractive index layer of 0.096 μm was formed to produce a light diffusion film A-02.

[Example 3]
Light diffusion films A-03 to A-07 were prepared in the same manner as the light diffusion film A-02 except that the coating amount of 1.3 μm crosslinked polystyrene beads was changed. The coating amount is as shown in Table 1.

[Example 4]
Light diffusion similar to light diffusion film A-02 except that 1.3 μm cross-linked polystyrene beads were changed to 1.5 μm silica beads (Nippon Shokubai Co., Ltd., Seahoster KE-P150, refractive index 1.44). Films A-08 to A-09 were prepared. The coating amount is as shown in Table 1.

[Example 5]
Translucent resin constituting the light diffusion layer is zirconium oxide ultrafine particle dispersion-containing hard coat coating solution (Desolite KZ-7114A, manufactured by JSR Corporation) 100 parts, translucent resin (Nippon Kayaku DPHA) 57 The mass part was stirred and mixed, dissolved in a methyl ethyl ketone / methyl isobutyl ketone (20/80 mass ratio) solution, then coated and UV-cured, and the refractive index of the coating film obtained was 1.61.
In this solution, 17 parts by mass of polymethyl methacrylate beads (MX150, particle size 1.5 μm, refractive index 1.49) and polymethylmethacrylate beads (MX300, MX300) were used as translucent fine particles. Triacetyl having a particle size of 3.0 μm, a refractive index of 1.49), 7 parts by mass, and these were mixed and adjusted to a solid content of 50% with methyl ethyl ketone / methyl isobutyl ketone (20/80 mass ratio). On a cellulose film (manufactured by Fuji Photo Film Co., Ltd., TD-80U), the coating amount of 1.5 μm polymethyl methacrylate-based beads is 0.4 g / m ^2, and after solvent drying, 160 W / cm. with air-cooled metal halide lamp (manufactured by eye graphics Co.), illuminance 400 mW / cm ^2, irradiation amount 300 mJ / cm To prepare a light diffusion film B-01 to cure the coated layer of ultraviolet irradiation. The dry thickness of the light diffusing layer of this film was 3.0 μm.

[Example 6]
On the light diffusion layer of the light diffusion film B-01, the above-mentioned coating solution for the low refractive index layer is applied using a bar coater, dried at 80 ° C., and further thermally crosslinked at 120 ° C. for 10 minutes to obtain a thickness. A low refractive index layer of 0.096 μm was formed, and a light diffusion film B-02 was produced.

[Example 7]
Light diffusing films B-03 to B-06 were prepared in the same manner as the light diffusing film B-02 except that the coating amount of the 1.5 μm polymethyl methacrylate beads was changed. The coating amount is as shown in Table 2.

[Example 8]
A light diffusing film B-07 was produced in the same manner as the light diffusing film B-02 except that the 1.5 μm polymethyl methacrylate-based beads were changed to 5.0 μm polymethyl methacrylate-based beads.

[Example 9]
Light diffusion films B-08 to A-09 were prepared in the same manner as the light diffusion film B-02 except that the 1.5 μm polymethyl methacrylate beads were changed to 1.3 μm crosslinked polystyrene beads and the coating amount was changed. The coating amount is as shown in Table 2.

[Example 10]
The same as the light diffusion film B-02 except that the 1.5 μm polymethyl methacrylate beads were changed to melamine formaldehyde beads (made by Nippon Shokubai, particle size 0.5 μm, refractive index 1.68), and the coating amount was changed. Light diffusing film B-10 was produced. The coating amount is as shown in Table 2.

(Evaluation of light diffusion film)
The obtained light diffusion film was evaluated for the following items. The results are shown in Tables 1 and 2.

(1) Specular reflectivity A spectrophotometer V-550 (manufactured by JASCO Corporation) is equipped with an adapter ARV-474, and in the wavelength region of 380 to 780 nm, the mirror surface has an output angle of -5 degrees at an incident angle of 5 °. The reflectance was measured, the average reflectance of 450 to 650 nm was calculated, and the antireflection property was evaluated.

(2) Haze The haze of the obtained film was measured using a haze meter MODEL 1001DP (manufactured by Nippon Denshoku Industries Co., Ltd.).

(3) Evaluation of scattered light profile Using an automatic goniophotometer GP-5 (manufactured by Murakami Color Research Laboratory Co., Ltd.), a light diffusing film is arranged perpendicular to the incident light, and it extends in all directions. The scattered light profile was measured. The scattered light intensity of 30 ° with respect to the light intensity at the output angle of 0 ° and the scattered light intensity of 60 ° with respect to the light intensity at the output angle of 0 ° were obtained.
FIG. 2 is a scattering profile of the light diffusing film (A-02) produced in Example 2. In FIG. 2, the concentric intervals are logarithmic.

  Next, a polarizing plate was prepared using the light diffusing film of the above example, and an evaluation was performed with a liquid crystal display device.

(Preparation of viewing side polarizing plate)
A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film. Light diffusion films A-01 to 09 and B-01 to 10 are subjected to saponification treatment and polarized using a polyvinyl alcohol adhesive so that the transparent substrate (triacetylcellulose) of the light diffusion film is on the polarizing film side. Affixed to one side of the membrane. In addition, an optical compensation film WVSA12B (manufactured by Fuji Photo Film) having an optically anisotropic layer made of a liquid crystalline compound is subjected to saponification treatment so that the film support becomes the polarizing film side using a polyvinyl alcohol-based adhesive. Affixed to the opposite side. In this way, viewing-side polarizing plates PA-01 to 09 and PB-01 to 10 were produced.

(Preparation of backlight side polarizing plate)
A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film. A commercially available triacetylcellulose film (Fuji Photo Film, Fujitac TD80) was saponified and attached to one side of the polarizing film using a polyvinyl alcohol adhesive. Further, saponification treatment is performed on an optical compensation film WVSA12B (manufactured by Fuji Photo Film) having an optically anisotropic layer made of a liquid crystalline compound so that the cellulose acetate film becomes the polarizing film side using a polyvinyl alcohol-based adhesive. Affixed to the opposite side. In this way, a backlight side polarizing plate was produced.

[Example 11]
A pair of polarizing plates provided in a liquid crystal display device (6E-A3, manufactured by Sharp Corporation) using a TN type liquid crystal cell is peeled off, and instead of polarizing plates PA-01 to 09 and PB-01 to 10, Each optical compensation film was attached to the viewer side via an adhesive so that the optical compensation film was on the liquid crystal cell side. On the backlight side, a backlight side polarizing plate was attached via an adhesive so that the optical compensation film was on the liquid crystal cell side. The transmission axis of the polarizing plate on the viewer side and the transmission axis of the polarizing plate on the backlight side were arranged to be in the O mode.
About the produced liquid crystal display device, the viewing angle was measured in eight steps from black display (L1) to white display (L8) using the measuring machine (EZ-Contrast160D, ELDIM company make).

Further, an image was displayed on the liquid crystal display device, and the image blur was evaluated in the following three stages.
I don't understand the image blur at all: A
The image is slightly amazed: B
Can recognize image blur: C
The results are shown in Tables 1 and 2.

From the results shown in Tables 1 and 2, the following is clear.
When a light diffusing film having a 30 ° / 0 ° scattered light intensity ratio of 0.01% or more was processed into a polarizing plate and used in a liquid crystal display device, a remarkable viewing angle improvement effect was obtained. In particular, the viewing angles in the downward and left-right directions are improved. However, when the scattered light intensity ratio at 30 ° / 0 ° exceeds 0.2%, the effect of widening the viewing angle is great, but the image becomes blurred. Therefore, the light diffusion film having a scattered light intensity ratio of 30 ° / 0 ° of 0.01% to 0.2% has no image blurring, and a wide viewing angle of the liquid crystal display device can be achieved.

Further, as is apparent from the table, the light diffusion film obtained by laminating the low refractive index layer and performing the antireflection treatment has a low specular reflectance of 2.5% or less and exhibits excellent antireflection properties.
Thus, the light diffusion film, antireflection film, polarizing plate, and liquid crystal display device of the present invention show excellent visibility.

It is a cross-sectional schematic diagram which shows the basic composition of a light-diffusion film. It is a scattering profile of the light-diffusion film (A-02) produced in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light diffusion film 20 Transparent support 30 Light diffusion layer 41 Matte particle 1
42 Matt particles 2
50 Low refractive index layer

Claims (8)

  A light diffusing film having a transparent base material and a light diffusing layer, wherein the light diffusing layer is in the range of 0.01 to 0.2% with respect to the light intensity at an emission angle of 0 ° of the scattered light profile of the goniophotometer. The light diffusion layer is made of a translucent resin and translucent fine particles, and the translucent fine particles have a refractive index different from that of the translucent resin, and the translucent resin Has a refractive index of 1.51 to 2.00, the difference between the refractive index of the translucent fine particles and the refractive index of the translucent resin is 0.02 to 0.20, and the light diffusion layer is 0 0.02% or less of the scattered light profile of the goniophotometer has a scattered light intensity of 60 ° with respect to the light intensity of the output angle of 0 °, and the light diffusion layer has a total haze value of 40 to 90%. A light diffusing film.   2. The light diffusing film according to claim 1, wherein the translucent fine particles comprise fine particles having a particle size of 0.5 μm to 2.0 μm and fine particles having a particle size of 2.5 μm to 5.0 μm.   The translucent resin of the light diffusion layer contains a monomer having a high refractive index and / or metal oxide ultrafine particles having a high refractive index together with a binder polymer having a saturated hydrocarbon or polyether as a main chain. Or the light-diffusion film of 2.   An antireflection film having a transparent substrate, a light diffusion layer, and a low refractive index layer in this order, wherein the light diffusion layer is in the range of 0.01 to 0.2% of the scattered light profile of the goniophotometer. The light diffusing layer is made of a translucent resin and translucent fine particles, and the translucent fine particles have a refractive index different from the refractive index of the translucent resin. The translucent resin has a refractive index of 1.51 to 2.00, and the difference between the refractive index of the translucent fine particles and the refractive index of the translucent resin is 0.02 to 0.20. Furthermore, the antireflection film has an average value in the wavelength region of 450 to 650 nm of the specular reflectance at 5 degrees incidence in the range of 2.5% or less, and the light diffusion layer is 0.02% or less. Of the scattered light profile of the goniophotometer with respect to the light intensity at an output angle of 0 ° 0 has an intensity of scattered light °, the light diffusion layer is in the range of 40 to 90%, the anti-reflection film having a total haze value.   5. The antireflection film according to claim 4, wherein the translucent fine particles comprise fine particles having a particle size of 0.5 μm to 2.0 μm and fine particles having a particle size of 2.5 μm to 5.0 μm.   The translucent resin of the light diffusion layer contains a monomer having a high refractive index and / or metal oxide ultrafine particles having a high refractive index together with a binder polymer having a saturated hydrocarbon or polyether as a main chain. Or 5. The antireflection film according to 5.   It is a polarizing plate in which the protective film is provided on both surfaces of the polarizing film, and one of the protective films is the light diffusion film according to any one of claims 1 to 3, or any one of claims 4 to 6. A polarizing plate, which is the antireflection film described in the item.   The light diffusion film according to any one of claims 1 to 3, the antireflection film according to any one of claims 4 to 6, or the polarizing plate according to claim 7 is provided on an outermost layer of the display. Image display device.

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