JP2003240948A - Optical film, polarizing plate, optical film roll, display device using the optical film, and method for manufacturing the optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film having such characteristics that the phase difference increases with longer wavelengths and having favorable durability against high temperature and high humidity and to provide a method for manufacturing the optical film with excellent productivity. <P>SOLUTION: The optical film comprises a cellulose ester having a 2-4C acyl group as a substituent and having the substitution degree A of acetyl groups and the substitution degree B of propionyl or butyryl groups satisfying both of (I): 2.0≤A+B≤3.0 and (II): A<2.4. Further, the refractive index Nx in the slow phase axis direction and the refractive index Ny in fast phase axis direction at 590 nm wavelength satisfy (III): 0.0005≤Nx-Ny≤0.0050, and the retardation R<SB>0</SB>in the film plane is ≥30 nm and ≤200 nm. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has a retardation function that has a smaller retardation for shorter wavelengths used in optical elements such as liquid crystal display devices and anti-glare films, and can be used as a polarizing plate protective film. The present invention relates to an optical film and a method for manufacturing an optical film.

[0002]

2. Description of the Related Art Polarizing plates used in liquid crystal display devices and the like are:
Generally, it is constituted by laminating a polarizing plate protective film made of a polymer film on both surfaces of a polarizer. Examples of the polarizer include a polyvinyl alcohol-based film, an ethylene vinyl alcohol-based film, a cellulose-based film, and a polycarbonate-based film. A stretched film or a polyvinyl alcohol-based film stretched and dyed with iodine is generally used. As the polarizing plate protective film, a cellulostriacetate film is generally used because of its small optical anisotropy, excellent transparency, and excellent adhesiveness to a polarizer. It is important that the polarizing plate protective film besides the above-mentioned properties, be excellent in dimensional stability, ultraviolet absorbing function for preventing deterioration of the polarizer, moisture barrier function, and the like. The polarizer and the polarizing plate protective film are bonded mainly with natural rubber, synthetic rubber, acrylic resin, butyral resin, epoxy resin, polyester resin, polyamide resin, polyvinyl alcohol resin, etc. It is adhered using an agent or an adhesive.

[0003] A retardation plate used in a liquid crystal display device or the like is used to solve problems such as color compensation and expansion of a viewing angle by being used in combination with a polarizing plate. It has a function of converting linearly polarized light into circularly polarized light with respect to wavelength and vice versa.

[0004] Further, by using as an anti-reflection film on a front plate of a plasma display or a display using an organic EL element, it is possible to reduce coloring of reflected light. It can also be used for anti-reflection of touch panels and the like.

[0005] Conventionally, as a material of the retardation plate, there are polycarbonate, polysulfone, polyethersulfone, amorphous polyolefin and the like. These polymer films have a characteristic that the retardation becomes smaller as the wavelength becomes longer, and it has been difficult to provide an ideal retardation characteristic to all wavelengths in the visible light region.

To solve this problem, Japanese Patent Application Laid-Open No. 2000-137
No. 116 proposes using an oriented film of cellulose acetate having a degree of acetylation of 2.5 to 2.8 as a retardation plate. According to this method, the longer the wavelength is, the larger the phase difference becomes, and an ideal phase difference characteristic is obtained for all wavelengths in the visible light region.

[0007] By using a retardation plate in combination with a polarizing plate, the above-described effects can be obtained. Heretofore, a polarizing plate and a retardation plate have been configured as separate optical elements in a liquid crystal display device. Therefore, a process of bonding the polarizing plate and the retardation plate is necessary, and in addition to the complicated manufacturing process, defective products are generated due to bubbles or foreign matter entering or wrinkling during bonding. There were many problems such as doing. Also, JP-A-2002-1
The optical compensatory film proposed in No. 4230 says that the retardation is controlled by an additive, but when used as a protective film for a polarizing plate, there is a problem that it flows into a processing solution during bleed-out or saponification. This may cause a defect when producing a polarizing plate, and its improvement has been required.

[0008] The present inventors thought that the manufacturing process of the liquid crystal display device could be shortened and the occurrence of defects could be reduced by attaching a retardation plate to the polarizer instead of the polarizing plate protective film of the polarizing plate.

A conventional retardation plate using polycarbonate cannot be saponified, so that it has poor adhesion to a polarizer and is difficult to use as a protective film for a polarizing plate. According to the above-mentioned Japanese Patent Application Laid-Open No. 2000-137116, since the material of the retardation plate is cellulose acetate, the problem of the adhesiveness to the polarizer was thought to be improved. However, since the degree of acetylation is lower than that of ordinary cellulose-triacetate, the moisture content of the film becomes too large, and the barrier property of moisture is significantly reduced. It has been found that there is a problem that the polarizer and the polarizing plate protective film are peeled off or the polarizer is deteriorated when exposed for a long time. Even when used as a retardation film separately from the polarizing plate protective film, a retardation plate having more excellent dimensional stability has been required. Further, a retardation film having excellent production stability and surface quality has also been required.

In recent years, liquid crystal display devices have been provided with portability, and the chances of using them outdoors have been increasing, and the usage of such devices installed in vehicles has been increasing. Has been receiving special attention in recent years. Considering the conditions of use, the durability of such a polarizing plate is 8
It is necessary that the polarizing plate does not deteriorate when exposed for 1000 hours in an environment of 0 ° C. and 90% RH. Further, there is also a demand for a retardation film having little change in retardation characteristics under high temperature and high humidity conditions.

As described above, an optical film having a phase difference function of increasing the phase difference as the wavelength becomes longer and having good resistance to high temperature and high humidity has not yet been put to practical use. Met.

[0012]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical film which has a characteristic that the longer the wavelength is, the larger the phase difference becomes, and which has good resistance to high temperature and high humidity and excellent productivity. It is to provide a manufacturing method.

[0013]

The above object has been attained by the structure described in the claims of the present invention.

Hereinafter, the present invention will be described in detail.

The cellulose ester used in the present invention has an acyl group having 2 to 4 carbon atoms as a substituent and satisfies the following formulas (I) and (II) simultaneously. (I) 2.0 ≦ A + B ≦ 3.0 (II) A <2.4 Here, A is the degree of substitution of an acetyl group, and B is the degree of substitution of an acyl group having 3 or 4 carbon atoms.

Cellulose has three hydroxyl groups in one glucose unit, and the degree of substitution is a numerical value indicating on average how many acyl groups are bonded to one glucose unit. . Therefore, the maximum degree of substitution is 3.0. These acyl groups may be substituted at the 2-, 3-, and 6-positions of the glucose unit on average, or may be substituted with a distribution. Furthermore, cellulose esters having various degrees of substitution of acyl groups may be blended to be in the above range as the cellulose ester as a whole.

The degree of substitution of the acetyl group and the degree of substitution of the other acyl group are determined by ASTM-D817-96.

It is particularly preferable that the following formulas (IV) and (V) are simultaneously satisfied.

(IV) 2.4 ≦ A + B ≦ 2.8 (V) 1.4 ≦ A ≦ 2.0 When the degree of substitution between the acetyl group and the acyl group having 3 to 4 carbon atoms is within the above range. In addition, it is possible to obtain an optical film having a characteristic that the retardation becomes larger as the wavelength becomes longer, and has a good moisture content and water barrier property.

It is particularly preferable that the average degree of substitution of the acetyl group is less than 2.0, because the dispersion of the retardation during stretching is small.

The viscosity average polymerization degree (polymerization degree) of the cellulose ester used in the present invention is preferably from 200 to 700, and particularly preferably from 250 to 500. By being in the above range, an optical film excellent in mechanical strength can be obtained.

The viscosity average degree of polymerization (DP) is determined by the following method. [Viscosity average degree of polymerization (DP)] 0.2 g of absolutely dried cellulose ester is precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride and ethanol (mass ratio 9: 1). This is measured for drop seconds at 25 ° C. using an Ostwald viscometer, and the degree of polymerization is determined by the following equation. ηrel = T / Ts [η] = (lnηrel) / CDP = [η] / Km Here, T is the number of seconds of falling of the measurement sample, Ts is the number of seconds of falling of the solvent, and C is the concentration of cellulose ester (g). / L), Km =
It is 6 × 10 ^-4 .

The raw cellulose for the cellulose ester used in the present invention includes cotton linter and wood pulp (derived from softwood or hardwood). Cellulose esters of different raw materials may be used alone or in combination. Further, the cellulose ester acylated with an acetyl group and an acyl group having 3 or 4 carbon atoms used in the present invention is also called a mixed fatty acid ester of cellulose.

Examples of the acyl group having 3 or 4 carbon atoms include a propionyl group and a butyryl group. Propionyl group or n-butyryl group is preferable from the viewpoint of mechanical strength and ease of dissolution when formed into a film,
Particularly, a propionyl group is preferable.

In the acylation of cellulose, when an acid anhydride or an acid chloride is used as an acylating agent, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent. You.

When the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and the acylating agent is an acid chloride (eg, CH ₃ C).
In the case of (H ₂ COCl), a basic compound is used.

The most common industrial synthesis method for mixed fatty acid esters of cellulose is to convert cellulose to fatty acids (acetic acid, propionic acid, acetic acid, propionic acid, etc.) corresponding to acetyl and other acyl groups.
This is a method of acylating with a mixed organic acid component containing valeric acid or the like or an acid anhydride thereof.

The cellulose ester used in the present invention can be synthesized, for example, by the method described in JP-A-10-45804.

The optical film of the present invention has a wavelength of 400 to 7
In the range of 00 nm, a longer wavelength shows a larger phase difference.

[0030] Here, Ritade in the plane of the film - Deployment R0 is calculated by _{R 0 = (Nx-Ny)} × d. Here, Nx represents the refractive index in the slow axis direction in the plane of the film, Ny represents the refractive index in the fast axis direction in the plane of the film, and d represents the film thickness (nm) of the film.

In the present invention, an optical film having an R ₀ of 30 to 200 nm can be obtained according to the intended use.
Optical films of １００100 nm are preferred.

[0032] In particular, Nx, if the wavelength of the light for obtaining the Ny is determined in 590nm and R _590, wavelength similarly 4
R ₄₅₀ , wavelength 650 nm when determined with 50 nm light
When it is assumed that _R650 is the value obtained by using the light of the formula (1), 0.5 < _R450 / _R590 <1.0 1.0 < _R650 / _R590 <1.5 It is preferable because it has an excellent function of making polarized light. More preferably, 0.7 < _R450 /
R ₅₉₀ <0.95, 1.01 <R ₆₅₀ / R ₅₉₀ <1.2, particularly preferably 0.8 <R ₄₅₀ / R ₅₉₀ <0.9
3,1.02 <is _{R 65 0 / R 590 <1.1} .

When the optical film of the present invention is used as a retardation film for a TN type or VA type liquid crystal display device, the in-plane retardation R _{0 at a} wavelength of 590 nm is 40.
~ 70 nm, in-plane retardation Rt in the thickness direction is 1
It is preferably from 20 to 150 nm, and particularly in the case of a TN type liquid crystal display device, _R0 is 60 ± 5 nm, Rt is 140 ± 5 nm, and VA
In the liquid crystal display device, R ₀ is 45 ± 5 nm and Rt is 130
A retardation film of ± 5 nm is preferably used.

[0034] When the optical film of the present invention is used as a quarter-wave plate, the phase difference R ₅₅₀ of the optical film at a wavelength of 550nm is 137.5 nm ± 20 nm is preferably further 137.5 nm ± 10 nm Is preferred. Also, R ₅₉₀ is preferably 147.5nm ± 20nm, preferably a further 147.5nm ± 10nm. With this range, a good function of a quarter-wave plate can be obtained.

In order to obtain the preferable optical characteristics as described above, the difference between the refractive index Nx in the slow axis direction and the refractive index Ny in the fast axis direction in the film plane of the optical film must be 0.00.
It is necessary to be not less than 05 and not more than 0.0050. A more preferred range is 0.0010 or more and 0.0030 or less.

The refractive index Nx in the slow axis direction, the refractive index Ny in the fast axis direction, and the refractive index N in the thickness direction in the plane of the film.
z, {(Nx + Ny) / 2−Nz} is 0.0
It is also effective to set it to 005 or more and 0.002 or less, and it is particularly preferable that it is 0.0010 or more and 0.0020 or less.

To make the refractive index of the film fall within the above range,
It can be achieved by stretching the film having the cellulose ester of the present invention, but the cellulose ester film generally has poor stretchability due to its high glass transition temperature and rigid molecular structure. Therefore, it was necessary to include a large amount of a plasticizer or to stretch at a high temperature. However, under such conditions, there were problems such as bleeding out of the plasticizer and deterioration and coloring of the resin.
However, the present inventors have developed a stretching method that does not have these problems by a method described later, and have completed the optical film of the present invention.

In the optical film of the present invention, the retardation Rt in the thickness direction is preferably from 70 nm to 300 nm, and particularly preferably from 75 to 200 nm, from the viewpoint of optical compensation effects such as expansion of the viewing angle. .

R _t = {(Nx + Ny) / 2−Nz} × d where the refractive index N in the slow axis direction at a wavelength of 590 nm
x, refractive index Ny in the fast axis direction, refractive index Nz in the thickness direction,
d is the film thickness (nm) of the film.

In the optical film of the present invention, the above N
x, Ny, and Nz have a relationship of Nx>Ny> Nz.

The haze of the optical film of the present invention is preferably 1.0% or less, more preferably 0.5% or less, and particularly preferably 0 to less than 0.1%. The transmittance is preferably 90% or more, particularly 92%.
It is desirable that this is the case.

The thickness of the optical film of the present invention is usually 5
Although it is in the range of from 500 to 500 μm, when it is also used as a polarizing plate protective film, the range of from 20 to 200 μm is preferable from the viewpoints of dimensional stability, water barrier property and the like of the polarizing plate. or,
The film thickness variation in the length and width directions of the roll film is preferably within ± 3%, particularly preferably within ± 1%, and more preferably within ± 0.1%.

In the optical film of the present invention, a plasticizer such as a phthalate or a phosphate, an ultraviolet absorber,
Additives such as antioxidants and matting agents can also be added.

The optical film of the present invention preferably contains a plasticizer. The plasticizer that can be used is not particularly limited, but in the case of a phosphate ester system, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, Phthalates such as diphenylbiphenyl phosphate, trioctyl phosphate and tributyl phosphate include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate and dibutyl phthalate. And glycol-2-esters such as di-2-ethylhexyl phthalate, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, and methyl phthalyl ethyl glycolate. Butyl phthalyl butyl glycolate and other acetyl citrate tribs Citrate plasticizers such as dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, 1,3-dibutylene glycol dibenzoate, tetraethylene glycol dibenzoate, trimethylolpropane triacetate, trimethylolpropane tribenzoate, etc. Polyhydric alcohol ester plasticizers and the like can be used alone or in combination. If necessary, two or more plasticizers may be used in combination.

By adding these plasticizers, the moisture content of the film can be reduced and the water barrier property can be improved.

In the production of the optical film of the present invention, a residual solvent in the film as described below is used for control.
By stretching, stretching can be performed even at a low temperature, but when this method is not used, stretching can be performed at a high temperature. When stretching at a high temperature, the stretching temperature is preferably stretched at a temperature equal to or higher than the glass transition temperature of cellulose ester. However, with a plasticizer as described above, the effect is weakened and stretchability is not sufficiently obtained. There are cases. It is necessary to use a plasticizer capable of imparting sufficient stretchability even at a high temperature. However, it has been found that a non-volatile plasticizer can be preferably used as such a plasticizer. Non-volatile plasticizers have a vapor pressure of 1333 at 200 ° C.
It is a compound having a pressure of Pa or less, having a very low vapor pressure and a low volatility. More preferably, the vapor pressure is 667 Pa or less, and still more preferably 133 Pa or less. For example, allylene bis (diaryl phosphate) ester is preferred. In addition, tricresyl phosphate (39 Pa, 200 ° C.), tris (2-ethylhexyl) trimellitate (67 Pa, 200 ° C.) and the like are also preferably used. Alternatively, Tokuhyo 6-501040
The non-volatile phosphate described in the above item is also preferably used.

Specific examples of the non-volatile plasticizer are shown below.

[0048]

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In addition, polyester, acrylic resin,
High molecular weight plasticizers such as polymers or oligomers such as copolymers containing polyvinyl acetate can also be preferably used.

In this case, the content of the plasticizer is preferably from 0.1 to 30% by mass, more preferably from 0.5 to 15% by mass, based on the cellulose ester. If necessary, the plasticizer may have a concentration distribution in the thickness direction of the film, and the amount of the plasticizer near the surface of one surface may be increased or the amount of the plasticizer near the surface of both surfaces may be reduced. Can be. For example, when the average amount of plasticizer is 1, the amount of plasticizer near both surfaces can be independently set to 0.1 to 10. By using a plasticizer in this way, the stretchability of cellulose ester at a high temperature can be improved, and in particular, an optical film having excellent surface quality and flatness can be manufactured with high productivity.

In the present invention, it is preferable that an ultraviolet absorber is contained in the cellulose ester film. The ultraviolet absorber has an excellent ability to absorb ultraviolet light having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal. From the viewpoint of good liquid crystal display properties, those which absorb as little as possible visible light having a wavelength of 400 nm or more are preferably used. In particular, the transmittance at a wavelength of 370 nm is desirably 10% by mass or less, preferably 5% by mass or less, and more preferably 2% by mass or less. For example, oxybenzophenone-based compounds, benzotriazo-
Compounds, salicylic acid ester compounds, triazine compounds, benzophenone compounds, cyanoacrylates
G compounds and nickel complex salt compounds, but are not limited thereto. Two or more ultraviolet absorbers may be used. Doping of UV absorber) In the present invention, the cellulose ester solution used for solution casting is sometimes referred to as a dope. ) May be added after dissolving in an organic solvent such as alcohol, methylene chloride or dioxolane, or may be added directly to the dope composition. Those which do not dissolve in an organic solvent such as inorganic powder are dispersed in an organic solvent and a cellulose ester using a dissolver or a sand mill, and then added to the dope. In the present invention, the amount of the ultraviolet absorber used is 0.1 to 5.0% by mass, preferably 0.5 to 2.0% by mass, based on the cellulose ester.
0 mass%, more preferably 0.8 to 2.0 mass%.

An optical film has a strict quality level against surface defects such as foreign matters and scratches. It is preferable to use an ultraviolet absorber having a distribution coefficient of 9.2 or more, since an optical film having few such surface defects can be obtained. The distribution coefficient of the ultraviolet absorber is more preferably 10.0 or more,
0.3 or more is most preferable. The partition coefficient represents the partition ratio between octanol and water defined by the following equation.

(Partition coefficient) = Log (Po / w) where Po / w = So / Sw where So represents the solubility of the ultraviolet absorbent in n-octanol at 25 ° C., and Sw represents 25 It represents the solubility of the ultraviolet absorber in pure water at ° C.

Examples of the ultraviolet absorber having a preferable distribution coefficient include compounds represented by the following general formula 1. Among them, the compound represented by the following general formula 2 is particularly preferable. General formula 1

[0055]

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In the formula, R1, R2, R3, R4, and R5 are monovalent organic groups, which may be the same or different. However, at least R1, R2, R3
Is an unsubstituted branched or straight-chain alkyl group having 10 to 20 carbon atoms. Further, it preferably has 11 to 18 carbon atoms, and particularly preferably has 12 to 15 carbon atoms. When the carbon number is within this range, the compatibility with the cellulose ester is excellent.

Here, the monovalent organic group includes a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, an alkoxy group, an acyloxy group, an aryloxy group, an alkylthio group. , An arylthio group, a mono- or dialkylamino group, an acylamino group or a 5- to 6-membered heterocyclic group.

Specific examples of the general formula 1 are shown below, but the present invention is not limited thereto.

[0059]

[0060]

Embedded image

General formula 2

[0062]

Embedded image

In the formula, R1, R2, R4, and R5 are monovalent organic groups, and have the same meanings as R1 to R5 in Formula 1. R6 is a branched alkyl group, such as an isopropyl group or an isobutyl group, having 3 to 20, preferably 3 to 15 carbon atoms.

Hereinafter, specific examples of the general formula 2 will be described, but the present invention is not limited thereto.

[0065]

Embedded image

In addition to the above-mentioned ultraviolet absorbers, for example,
JP-A-6-148430, Japanese Patent Application No. 12-156039
The polymer ultraviolet absorber described in (1) can also be preferably used for this purpose.

Further, the cellulose ester film of the present invention preferably contains an antioxidant. As the antioxidant, a hindered phenol compound is preferably used. Di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,
5-di-t-butyl-4-hydroxyphenyl) propionate], triethyleneglycol-bis [3- (3
-T-butyl-5-methyl-4-hydroxyphenyl)
Propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio)- 6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-
4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'hexamethylenebis (3,5-di-t- Butyl-4-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4,6
-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-crezo-
Pentaerythrityl-tetrakis [3- (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t
-Butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, a hydrazine-based metal deactivator such as N, N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine or tris (2,4-di-t- A phosphorus-based processing stabilizer such as (-butylphenyl) phosphite may be used in combination. The addition amount of these compounds is preferably 1 ppm to 1.0% by mass relative to the cellulose ester,
0-1000 ppm is more preferred. Further, in the present invention, in the cellulose ester film, in order to improve the handleability, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate And inorganic fine particles such as aluminum silicate, magnesium silicate, and calcium phosphate, and a matting agent such as a crosslinked polymer. Among them, silicon dioxide is preferable because the haze of the film can be reduced. The average particle size of the secondary particles of the fine particles is in the range of 0.01 to 1.0 μm,
Its content is 0.005 to 5% of cellulose ester.
0.3 mass% is preferred. Fine particles such as silicon dioxide are often surface-treated with an organic substance, but such particles are preferable because the haze of the film can be reduced. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes, and the like, and a treatment in which a methyl group is present on the surface is preferable. The larger the average particle size of the fine particles, the greater the matting effect, and the smaller the average particle size, the more excellent the transparency. Therefore, the average particle size of the primary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 16 nm. . These fine particles are usually present in the film as agglomerates, and it is preferable to form irregularities of 0.01 to 1.0 μm on the film surface.

As the fine particles of silicon dioxide, AEROSIL 200, 200V, 30
0, R972, R972V, R974, R202, R8
12, OX50, TT600, etc., preferably AEROSIL R972, R972V, R9
74, R202 and R812. Two or more of these matting agents may be used in combination. When two or more kinds are used in combination, they can be used in a mixture at an arbitrary ratio. In this case, a matting agent having a different average particle size or material, for example, AEROSIL
200 V and R972 V in a mass ratio of 0.1: 99.9 to
It can be used in the range of 99.9: 0.1.

Since the optical film of the present invention has a water barrier property and a low water content, it can be preferably used for a polarizing plate as a polarizing plate protective film for a polarizing plate. As described above, the polarizing plate is formed by bonding and laminating a polarizing plate protective film for a polarizing plate on at least one surface of a polarizer. As the polarizer, a conventionally known polarizer can be used. For example, a polarizer is obtained by treating a hydrophilic polymer film such as a polyvinyl alcohol film with a dichroic dye such as iodine and stretching. Lamination of the cellulose ester film and the polarizer is not particularly limited, but can be performed with an adhesive comprising an aqueous solution of a water-soluble polymer. As the water-soluble polymer adhesive, a completely saponified aqueous solution of polyvinyl alcohol is preferably used.

The polarizing plate thus obtained can be used for various display devices. Examples of the display device include a liquid crystal display device, an organic electroluminescent device, an organic EL display, a plasma display, and the like. For example, in the case of a single polarizing plate reflective liquid crystal display device, the configuration is such that the polarizing plate is protected from the front side. Film / polarizer / optical film of the present invention / glass substrate / ITO transparent electrode / alignment film / TN type liquid crystal / alignment film / metal electrode / reflection film / glass substrate. In the conventional case, the polarizing plate protective film / polarizer / polarizing plate protective film / retardation plate / glass substrate / ITO transparent electrode / alignment film / TN type liquid crystal /
It has a configuration of alignment film / metal electrode / reflection film / glass substrate.
In the conventional configuration, coloring is observed due to insufficient retardation characteristics with respect to the wavelength of the retardation plate. However, by using the optical film of the present invention, a good liquid crystal display device without coloring can be obtained. In addition, the optical film of the present invention can be preferably used by being bonded to a polarizing plate as a retardation film.In addition, by using the optical film of the present invention, a polarizing plate protective film conventionally used separately and The retardation plate can be made of a single film, so that the time-consuming laminating process can be shortened.

The optical film of the present invention can be preferably used in the constitution of polarizing plate protective film / polarizer / optical film of the present invention / liquid crystal cell / optical film of the present invention / polarizer / polarizing plate protective film. In particular, a polarizing plate having the optical film of the present invention can be used by being attached to both sides of a liquid crystal cell such as a TN type, a VA type, and an OCB type.
Further, it was possible to provide a display device having an excellent viewing angle and little coloring and excellent visibility. In particular, the polarizing plate using the optical film of the present invention was less deteriorated under high temperature and high humidity conditions, and could maintain stable performance for a long time.

The method for producing the optical film of the present invention is not particularly limited, but the following method can be preferably used. First, a cellulose ester is dissolved in an organic solvent capable of dissolving to form a dope. A cellulose ester flake or powder is mixed with an organic solvent and dissolved with stirring to form a dope. The dissolution may be carried out at normal pressure, at a temperature below the boiling point of the main solvent, or at a pressure above the boiling point of the main solvent, as disclosed in JP-A-9-95544, JP-A-9-95557 or JP-A-9-95538. There are various dissolving methods such as a cooling dissolving method as described and a high-pressure dissolving method as described in JP-A-11-21379. After dissolution, the dope is filtered with a filter medium, defoamed, and sent to the next step by a pump. The concentration of cellulose ester in the dope is 10-3.
It is preferably about 5% by mass, and particularly preferably 20 to 35% by mass.

As the cellulose ester used in the present invention, those having little bright spot foreign matter are preferably used. The bright spot foreign matter is a phenomenon in which cellulosic material is present between polarizing plates arranged in crossed Nicols.
When a sester film sample is placed, illuminated from one side, and observed from the other, a point that looks shining when light from a light source is transmitted is called a bright spot foreign matter. Optical films for display devices are required to have a small number of them, and one or more bright spot foreign substances having a size of 10 μm or more are required.
00 / cm < ² > or less, particularly preferably substantially no, and a bright spot foreign matter having a size of 5 to 10 [mu] m is 200
Pieces / cm ² or less, more preferably 50 pieces / cm ² or less,
Preferably, it is substantially absent. It is desirable that the number of bright spot foreign matters less than 5 μm is also small. The bright spot foreign matter of the optical film can be reduced by selecting the raw material cellulose ester having less bright spot foreign matter and by filtering the cellulose ester solution used for casting. Organic solvents that can dissolve the cellulose ester include methyl acetate, ethyl acetate, amyl acetate, ethyl formate, acetone, cyclohexanone, methyl acetoacetate, tetrahydrofuran,
1,3-dioxolan, 1,4-dioxane, 2,2
2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2
-Propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,1
3,3,3-hexafluoro-2-propanol, 2,
2,3,3,3-pentafluoro-1-propanol,
Examples thereof include 1,3-dimethyl-2-imidazolidinone, nitroethane, and methylene chloride. Chlorine-based organic solvents such as methylene chloride may not be used in recent severe environmental problems, and non-chlorine-based organic solvents are more preferable. Among them, methyl acetate and acetone can be preferably used. Also, when a lower alcohol such as methanol, ethanol or butanol is used in combination with these organic solvents, the solubility of the cellulose ester in the organic solvent can be improved or the dope viscosity can be reduced. It is preferable because it can improve peelability when peeled off from the support. Particularly, ethanol having a low boiling point and low toxicity is preferable. These lower alcohols are 2% based on the total organic solvent.
It is preferable that the content is not less than 50% by mass and not more than 50% by mass. In the solution casting film forming method, the above-mentioned dope is filtered, sent to a die by a metering pump, and the dope is cast from the die onto a stainless belt or a metal drum whose surface is polished, and the metal is supported. On the body, the organic solvent is evaporated or cooled to solidify, the web is peeled off before the metal support goes around, and dried in a drying step to form a film.

The cellulose ester solution (hereinafter also referred to as “dope”) prepared as described above is passed through a pressurized type fixed gear pump, for example, through a pressurized type fixed gear pump which can send a fixed amount of liquid with high precision by the number of rotations. Sent. The dope sent from the gear pump to the pressurizing die is uniformly cast from a die (slit) of the pressurizing die onto a support that is rotating endlessly. When the support has completed one round, it is peeled off from the support as a freshly dried film (web), dried while being passed through a rotating roll group, and the dried film is taken up to a predetermined length by a winder. It is wound up.

The casting method useful in the present invention includes a method in which the adjusted dope is uniformly extruded from a pressing die onto a support, and a method in which the dope once cast on the support is braided. A method using a doctor blade to adjust the film thickness by a method, a method using a reverse roll coater to adjust the film thickness by a roll that rotates a dope once cast on a support in the reverse direction, etc. However, a method using a pressing die is preferable. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. In addition to the above,
For example, JP-A-61-94724 and JP-A-61-1480.
No. 13, JP-A-4-85011 and JP-A-4-286611
No. 5-185443, No. 5-185445, No. 6-278149, and conventionally known methods described in No. 8-207210 can be preferably used,
By setting each condition in consideration of the difference in the boiling point of the solvent to be used, the same effects as those described in the respective publications can be obtained. As the endless support, a drum whose surface is mirror-finished by chromium plating or a stainless belt (also referred to as a band) whose surface is mirror-finished by surface polishing is preferably used. One or two or more press dies may be provided. Preferably it is one or two. When two or more units are installed, the amount of the dope to be cast may be divided into various ratios for the respective dies, and the dopes are supplied to the dies at respective ratios from a plurality of precision metering gear pumps. The dope cast on the support may be, for example, a method in which hot air is blown from the front side of the drum or belt, that is, a web side on the support, a method in which hot air is blown from the back of the drum or belt, or a temperature control. Contact the backside of the belt or drum
Although the drum or belt can be heated by heat transfer and dried by a liquid heat transfer method for controlling the surface temperature, it is preferable to use a back liquid heat transfer method. The surface temperature of the support before the dope is cast
Any number may be used as long as it is lower than the boiling point of the solvent used in the pump. However, in order to promote drying and to lose the fluidity of the dope on the support, the temperature should be set to 1 to 10 ° C. lower than the boiling point of the solvent having the lowest boiling point among the solvents used. Is preferred. The production speed varies depending on the diameter of the drum or the length of the belt, the drying method, the composition of the dope solvent, etc., but the amount of the residual solvent at the time when the formed web is peeled off from the drum or the belt is also affected. I do. That is, if the solvent concentration in the vicinity of the surface of the drum or belt in the thickness direction of the dope film is too high, the dope remains on the drum or belt when the formed web is peeled off, and the next casting occurs. This is because the formed web needs to be strong enough to withstand the peeling force. The amount of residual solvent at the time of peeling differs depending on the drying method, and the method of transferring heat from the belt or the back of the drum reduces the amount of residual solvent more effectively than the method of drying by blowing air from the surface of the dope. can do. A method for drying a web that has been dried and peeled on a drum or belt will be described. The web peeled at the peeling position immediately before the drum or belt makes one round is transported by alternately passing through a group of rolls arranged in a staggered manner, or by gripping both ends of the peeled web with a clip or the like. It is transported by a non-contact transport method or the like. Drying is performed by a method in which air at a predetermined temperature is applied to both surfaces of the web (film) being conveyed, or a method using a heating means such as a microwave. Since rapid drying may impair the planarity of the film to be formed, it is preferable to dry at a temperature at which the solvent does not foam at the initial stage of drying, and to dry at a high temperature after the drying has progressed. In the drying step after peeling from the support, the film tends to shrink in the longitudinal direction or the width direction due to evaporation of the solvent. Shrinkage increases with drying at higher temperatures. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the resulting film. From this point, for example, Japanese Patent Application Laid-Open No. 62-4662.
As shown in No. 5, a method (tenter method) in which all or some of the drying steps are performed in the width direction while holding both ends of the width of the web with a clip or a pin is preferable. The drying temperature in the drying step is 40 to 250.
C., especially 70 to 180.degree. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, but may be appropriately selected according to the type and combination of the solvents used. In the method for producing an optical film of the present invention, the web (film) peeled from the support is preferably stretched when the residual solvent amount in the web is less than 120% by mass, and particularly preferably from 10 to 1%.
While being in the range of 00% by mass, at least one direction is not less than 1.
It is preferable to stretch by 2-4.0 times.

The residual solvent amount can be represented by the following equation.

Residual solvent amount (% by mass) = {(M−N) / N} × 100 Here, M is the mass of the web at an arbitrary point, and N is the web obtained by measuring M at 110 ° C. for 3 hours. It is the mass at the time. If the residual solvent amount in the web is too large, the effect of stretching cannot be obtained, and if it is too small, stretching becomes extremely difficult,
Web breakage may occur. The more preferable range of the amount of the residual solvent in the web is from 10% by mass to 50% by mass, particularly preferably from 12% by mass to 30% by mass. Also, if the stretching ratio is too small, a sufficient retardation cannot be obtained,
If it is too large, stretching may be difficult and breakage may occur. The more preferable range of the stretching ratio is 1.2 times or more.
2.0 times, more preferably 1.3 times to 1.times.
5 times. A solution cast film formed using the cellulose ester of the present invention can be stretched without heating to a high temperature if the residual solvent amount is within a specific range. It is preferable because it can be short. However, if the temperature of the web is too high, the plasticizer volatilizes, so the range of room temperature (15 ° C) to 160 ° C or less is preferable. Stretching in biaxial directions orthogonal to each other is an effective method for keeping the refractive indexes Nx, Ny, and Nz of the film within the scope of the present invention. For example, when the film is stretched in the casting direction, if the shrinkage in the width direction is too large, the value of Nz becomes too large. In this case, the width shrinkage of the film is suppressed or
It can be improved by stretching in the width direction. In the case of stretching in the width direction, a distribution may occur in the refractive index due to the width. This may be seen, for example, when a tenter method is used.However, when the film is stretched in the width direction, a contraction force is generated at the center of the film, and the phenomenon is caused by the fact that the end is fixed. This is considered to be a so-called bowing phenomenon. Even in this case, the boring is performed by stretching in the casting direction.
Thus, it is possible to reduce the distribution of the phase difference in the width direction. Further, the film thickness variation of the film obtained by stretching in biaxial directions perpendicular to each other can be reduced. If the fluctuation of the film thickness of the optical film is too large, the phase difference becomes uneven, which causes a problem such as coloring when used as a circularly polarizing plate. The variation in the thickness of the optical film is ± 3%, and further ± 1%.
% Is preferable. For the purpose as described above, the method of stretching in the biaxial directions orthogonal to each other is effective, and the stretching ratios in the biaxial directions orthogonal to each other are 1.2 to 2.0 times and 0.7 to 1.0 times, respectively. It is preferable that the range be twice as large. Here, 1.2 to 2..
Stretching 0 times and making the other orthogonal 0.7 to 1.0 times means reducing the interval between the clips and pins supporting the film to a range of 0.7 to 1.0 times. are doing. For example, 1. using a biaxial stretching tenter in the width direction.
This means that when the film is stretched so as to have an interval of 2 to 2.0 times, the interval in the longitudinal direction is reduced to a range of 0.7 to 1.0 times. At this time, a tension that is weaker than the tension that is applied in the width direction is applied in the longitudinal direction, and it is preferable that the gap in the length direction be reduced in accordance with the stretching in the width direction. Thereby, the in-plane retardation Rt,
The retardation R _{0 in the} thickness direction or the ratio thereof can be adjusted, and a desired phase difference can be obtained. For example,
A retardation film having an Rt / _R0 ratio of 1.5 to 3.0 can be obtained. The method for stretching the web is not particularly limited. For example, a method is used in which a plurality of rolls are provided with a peripheral speed difference, and the roll is stretched in the longitudinal direction by using the roll peripheral speed difference, and both ends of the web are fixed with clips or pins, and the intervals between the clips and pins are reduced. A method of spreading in the traveling direction and stretching in the vertical direction, a method of similarly spreading in the horizontal direction and stretching in the horizontal direction, and a method of simultaneously spreading vertically and horizontally and stretching in both the vertical and horizontal directions are included. Of course, these methods may be used in combination. Also, in the case of the so-called tenter method, it is preferable to drive the clip portion by the linear drive method since smooth stretching can be performed and the risk of breakage can be reduced.

In the film obtained as described above, the amount of the residual solvent in the final film is preferably 2% by mass or less, more preferably 0.4% by mass or less, in order to obtain a film having good dimensional stability. Is preferred. Furthermore, when the amount of residual solvent is 10
It is preferable to treat the film dried to less than 5% by mass, preferably less than 5% by mass, at a temperature of 130 to 200 ° C. for 10 seconds or more, preferably for 30 seconds or more, since a film having further excellent dimensional stability can be obtained. Once from room temperature to 100
It is more preferred that the film cooled to below ° C be treated again at this temperature. Especially 10 ° C higher than the temperature at the time of stretching
It is effective to make the above lower. These steps from casting to post-drying may be performed under an air atmosphere or under an inert gas atmosphere such as nitrogen gas. As the winding machine for winding the obtained cellulose ester film, a generally used winding machine can be used, and a constant tension method, a constant torque method, a taper tension method, and a constant internal stress. It can be wound by a winding method such as a program tension control method. In the optical film roll obtained as described above, the slow axis direction of the film is preferably ± 2 degrees with respect to the winding direction (length direction of the film), and more preferably ± 1 degrees. Is preferably within the range. Alternatively, it is preferable that the angle is ± 2 degrees with respect to the direction perpendicular to the winding direction (the width direction of the film),
More preferably, it is within the range of ± 1 degree. In particular, the slow axis direction of the film is the winding direction (length direction of the film)
Is preferably within ± 0.1 degrees. Alternatively, it is preferably within ± 0.1 degrees with respect to the width direction of the film.

The optical film thus obtained is preferably used as a polarizing plate protective film having a retardation, and the optical film is arranged so that the slow axis of the optical film and the absorption axis of the polarizer are orthogonal to each other. preferable. To be orthogonal is to intersect at an angle of 80 to 100 degrees, preferably to intersect at an angle of 85 to 95 degrees, and particularly preferably to intersect at 90 ± 1 degrees. The thickness of the finished optical film (after drying) of the present invention is adjusted to a desired thickness so that the solid content contained in the dope, the slit gap of the die, the extrusion pressure from the die, and the support It can be performed by adjusting the body speed and the like. Another method preferably used in the method for producing an optical film of the present invention will be described. In the present invention, as described above, by controlling the amount of the residual solvent in the film, the film can be stretched without increasing the temperature. However, the stretching can be similarly performed by the following method. That is, when the substituent has an acyl group having 2 to 4 carbon atoms, the degree of substitution of an acetyl group is A, and the degree of substitution of a propionyl group or a butyryl group is B, the following formulas (XII) and (XIII) A solution in which a cellulose ester satisfying at the same time and a plasticizer having a vapor pressure at 200 ° C. of 1333 Pa or less are dissolved in an organic solvent is cast on a support, and the solvent is evaporated to form a cellulose ester film. At a temperature of 130 to 200 ° C. in at least one direction so as to satisfy the following formula (XIV). (XII) 2.0 ≦ A + B ≦ 3.0 (XIII) A <2.4 (XIV) 0.0005 ≦ Nx−Ny ≦ 0.0050 The plasticizer having a specific vapor pressure and the stretching method are described above. It is on the street. Stretching can be carried out at a peeling residual solution amount of 10% by mass or less, but it is particularly preferred that the film be stretched at less than 2% by mass. The optical film thus obtained is TN
It is useful as a retardation film used in various liquid crystal display devices such as a liquid crystal display, a VA type, and an OCB type.

[0080]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. The moisture content measurement film sample is dried at 120 ° C. for 1 hour, and the mass M0 (g) of the film at this time is measured. Next, after leaving this sample at 23 ° C. and 55% RH for 3 days,
At this time, the mass M (g) of the film is measured. The moisture percentage is determined by the following equation. Water content (%) = (M−M0) / M × 100 Example 1 Cellulose acetate propionate 100 having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.80 and a viscosity average polymerization degree of 350 Parts by mass, tricresyl phosphate 10 parts by mass, methylene chloride 300 parts by mass, ethanol 6
0 parts by mass was placed in a closed container, and the mixture was gradually heated while slowly stirring to 45 ° C. over 60 minutes to dissolve. The pressure in the container was 1.2 atm. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope. Separately from the above, cellulose acetate propionate 5
Parts by mass, 3 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), 3 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals), and 171 (manufactured by Ciba Specialty Chemicals)
3 parts by mass), 94 parts by mass of methylene chloride and 8 parts by mass of ethanol were mixed and dissolved by stirring to prepare an ultraviolet absorbent solution. The ultraviolet absorbent solution was added at a ratio of 2 parts by mass to 100 parts by mass of the above dope, and the mixture was sufficiently mixed with a static mixer. It was cast at 0.6 m. After drying for 1 minute on a temperature-controlled stainless steel belt by contacting warm water at a temperature of 35 ° C. from the back surface of the stainless steel belt, further contacting cold water of 10 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Peeled from stainless steel belt. The residual solvent amount in the web at the time of peeling was 100% by mass. Then, both ends of the peeled web are gripped with clips using a simultaneous biaxial stretching tenter, and the clip interval in the width direction is changed. 1. In the extending direction (longitudinal direction)
It was stretched 0 times. After the stretching is completed, the film temperature is temporarily set to 80
After cooling to 125 ° C.,
After drying at 20 ° C. for 20 minutes, a cellulose ester film (optical film 1) having a thickness of 80 μm was obtained. The optical film 1 was wound around a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 3 m and a length of 2000 m by a tape tension method. At this time, an embossing ring at a temperature of 250 ° C. was pressed against the end of the film, and a 10 μm thickness embossing process was performed to prevent adhesion between the films. Sampling is performed from the obtained film roll from the end in the width direction, the center, and the end on the opposite side of the film, and the refractive index Nx in the slow axis direction, the refractive index Ny in the fast axis direction, and the refraction in the thickness direction. The rate Nz was measured as follows, and Nx−Ny, (Nx
+ Ny) / 2-Nz, R _{0 , and} Rt were calculated. As a result, at the end, the center, and the end on the opposite side, all were 0.00056, 0.00163, 45 nm, and 130n.
m, both of which are within the scope of the present invention, and it has been confirmed that the film has preferable characteristics as a retardation film. Here, R ₀ = (Nx−Ny) × d, where d is the thickness of the film (nm). The direction of the slow axis is within ± 0.5 degrees with respect to the width direction of the film for each sample. It was settled. (Measurement of refractive index in slow axis direction, refractive index in fast axis direction, refractive index in thickness direction and slow axis direction) Automatic birefringence meter KOB
Using RA-21ADH (manufactured by Oji Scientific Instruments),
Under an environment of 23 ° C. and 55% RH, a three-dimensional refractive index is measured at a wavelength of 590 nm, and the refractive indices Nx, Ny, N
z was determined. As a result of measuring the moisture content by the method described above, 1.7 was obtained.
%Met.

As a cellulose ester film (polarizing plate protective film 1), Konica Cat KC8UX2MW
(Film thickness: 80 μm) Konica Corporation was used. Separately from the above, the degree of acetyl group substitution is 2.92 and the viscosity average degree of polymerization is 3
100 parts by mass of cellulose triacetate, 2 parts by mass of ethyl phthalylethyl glycolate, 10 parts by mass of triphenyl phosphate, 350 parts by mass of methylene chloride,
50 parts by mass of ethanol was placed in a closed container, and the mixture was gradually heated while slowly stirring, and then heated to 45 ° C. over 60 minutes to dissolve. The pressure in the container was 1.2 atm. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope. Separately, the cellulostriacete
5 parts by mass, Tinuvin 326 (Chiba Specialty
3 parts by mass of Chemicals, 7 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals), 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals), and AEROSIL 200V
1 part by weight (manufactured by Nippon Aerosil Co., Ltd.)
0 parts by mass and 10 parts by mass of ethanol are mixed and dissolved by stirring.
A UV absorber solution was prepared. The ultraviolet absorber solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the above-mentioned dope, and the mixture was sufficiently mixed by a static mixer. It was cast at 6 m. The hot water of 35 ° C is brought into contact with the back of the stainless steel belt and the temperature is controlled on the stainless steel belt.
After drying for 15 minutes, apply
After being kept in contact with cold water of 15 ° C. for 15 seconds, it was peeled off from the stainless steel belt. The residual solvent amount in the web at the time of peeling was 70% by mass. Then, the web was dried at 120 ° C. for 10 minutes while fixing both ends of the peeled web, and the film thickness was 80 μm.
To obtain a cellulose ester film (protective film for polarizing plate 1).

Each of the obtained cellulose ester films (polarizing plate protective film 1 and optical film 1) was treated with 6
It was immersed in a 2 mol / l aqueous solution of sodium hydroxide at 0 ° C. for 2 minutes, washed with water, and dried at 100 ° C. for 10 minutes to obtain an alkali saponified cellulose ester film.
Also, a polyvinyl alcohol film having a thickness of 120 μm was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to form a polarizing film (polarizer 1). . The optical film 1 was bonded to one surface of the polarizer 1 and the polarizing plate protective film 1 was bonded to the other surface of the polarizer 1 using a fully saponified 5% aqueous solution of polyvinyl alcohol as an adhesive to prepare a polarizing plate. Board 1). For the optical film 1, film samples were cut out from both ends and the center in the width direction of the film roll, and two polarizing plates were prepared for each (a total of six). Lamination was performed so that the angle between the absorption axis of the polarizer and the slow axis (width direction) of the optical film was 45 degrees. Next, of the above-mentioned six polarizing plates, a total of three polarizing plates each having a different width position of the optical film are used.
Exposure was performed for 1000 hours under the condition of 90 ° C. and 90% RH. The three polarizing plates without moist heat treatment and the three polarizing plates with moist heat treatment obtained as described above were incorporated into a VA liquid crystal display device and evaluated. The configuration was the polarizing plate 1 / VA type liquid crystal cell of the present invention / polarizing plate 1 of the present invention. The polarizing plate was arranged so that the optical film 1 of the present invention was on the liquid crystal cell side. Visual observation from a laterally oblique direction shows a good contrast, and a very good visibility compared to a polarizing plate (a polarizing plate protective film 1 / a polarizer / a polarizing plate protective film 1) produced as a comparison. It was confirmed that the corner was enlarged. Those subjected to the wet heat treatment also exhibited excellent visibility. Example 2 100 parts by mass of cellulose acetate propionate having a degree of substitution of an acetyl group of 2.30, a degree of substitution of a propionyl group of 0.5, and a viscosity average degree of polymerization of 400, 10 parts by mass of trimethylolpropane tribenzoate, and 290 of methylene chloride Parts by mass and 60 parts by mass of ethanol were placed in a closed container, and the temperature of the mixture was gradually increased while slowly stirring the mixture.
C. and dissolved. The pressure in the container was 1.2 atm. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope. Separately, 5 parts by mass of the above cellulose acetate propionate, 3 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), and Tinuvin 109 (manufactured by Ciba Specialty Chemicals)
3 parts by mass, 3 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and AEROSIL R9
One part by mass of 72V (manufactured by Nippon Aerosil Co., Ltd.) was mixed with 94 parts by mass of methylene chloride and 8 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution. 2 parts by mass of the ultraviolet absorber solution was added to 100 parts by mass of the above dope, and the mixture was sufficiently mixed by a static mixer. The mixture was placed on a stainless belt from a die at a dope temperature of 33 ° C. and a width of 1.6 m.
Was cast. After drying for 1 minute on a temperature-controlled stainless steel belt by contacting hot water at a temperature of 33 ° C. from the back surface of the stainless steel belt,
After contact with cold water of 10 ° C. and holding for 10 seconds, the film was separated from the stainless steel belt. The residual solvent amount in the web at the time of peeling was 90% by mass. Then, both ends of the peeled web are gripped with clips using a simultaneous biaxial stretching tenter, and the intervals between the clips are simultaneously changed in the width direction and the casting direction (length direction). The film was stretched twice and shrunk 0.9 times in the casting direction (length direction). Thereafter, the film temperature is once cooled to 90 ° C., and then dried at 125 ° C. for 20 minutes while being conveyed by a roller.
Was obtained as a cellulose ester film (optical film 2). The optical film 2 was wound around a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 1.3 m and a length of 2000 m by a tape tension method. At this time, an emboss ring at a temperature of 230 ° C. was pressed against the end of the film, and a 10-μm thickness embossing process was performed to prevent adhesion between the films. Sampling is performed from the obtained film roll from the end in the width direction, the center, and the end on the opposite side of the film, and the refractive index Nx in the slow axis direction, the refractive index Ny in the fast axis direction, and the refraction in the thickness direction. The rate Nz is measured as follows,
When Nx−Ny, (Nx + Ny) / 2−Nz, R _{0 , and} Rt were calculated, 0.0007 at the end in order.
5, 0.00175, _R0 60 nm, Rt140n
m, in the center, 0.00075, 0.0017
5, R ₀ 60nm, Rt140nm, at the opposite end, 0.00075,0.00175, R ₀ 60n
m, Rt 140 nm, and both were within the scope of the present invention.

The direction of the slow axis was ± 0.3 degrees with respect to the width direction of the film. As a result of measuring the moisture content by the method described above, it was 1.9%. The obtained cellulose ester film (optical film 2) and the polarizing plate protective film 1 used in Example 1 were immersed in a 2 mol / l aqueous solution of sodium hydroxide at 60 ° C. for 2 minutes, washed with water, and then washed with water. After drying at 10 ° C. for 10 minutes, an alkali saponified cellulose ester film (optical film 2) was obtained. The optical film 2 described above was used on one side of the polarizer 1 obtained in Example 1, and the polarizing plate protective film 1 used in Example 1 was used on the other side with a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive. Each was used to produce a laminated polarizing plate (polarizing plate 2). For the optical film 2, film samples were cut out from both ends and the center in the width direction of the film roll, and two films were obtained for each (a total of six films).
A polarizing plate was manufactured. Lamination was performed so that the angle between the absorption axis of the polarizer and the slow axis (width direction) of the optical film was 90 degrees. In the cellulose ester film of the present invention, the alkaline solution in the saponification treatment was not significantly contaminated, and there was no failure due to adhesion of foreign matter. Next, of the above-mentioned six polarizing plates, a total of three polarizing plates each having a different position in the width direction of the optical film were obtained at 80 ° C. and 90% RH.
Exposure for 000 hours. Using the three polarizing plates without moist heat treatment and the three polarizing plates with moist heat treatment obtained as described above,
It was incorporated into a TN type liquid crystal display and evaluated. The structure was: polarizing plate 2 of the present invention / TN liquid crystal cell / polarizing plate 2 of the present invention. The polarizing plate was arranged so that the optical film 2 of the present invention was on the liquid crystal cell side. As a result of visual observation from a laterally oblique direction, none of the polarizing plates showed a good contrast and did not appear to be colored yellow. Those subjected to the wet heat treatment also exhibited excellent visibility. It was confirmed that in the polarizing plate (polarizing plate protective film 1 / polarizer / polarizing plate protective film 1) produced as a comparison, the gradation was inverted in the oblique horizontal direction and the viewing angle was considerably narrow. Comparative Example 1 Cellulose Acetate Propionate 100 of Example 1
The same procedure as in Example 1 was carried out except that the parts by mass were changed to 100 parts by mass of cellulose acetate having a degree of substitution of acetyl group of 2.6, and 10 parts by mass of tricresyl phosphate was changed to 10 parts by mass of triphenyl phosphate. A comparative optical film 1 having a thickness of 80 μm was produced. As a result of measuring the moisture content by the method described above, the result was 3.4%, and the result that the moisture content was large was obtained. Using this comparative optical film 1, a polarizing plate was prepared and evaluated in the same manner as in Example 1. When the same evaluation as in Example 1 was performed, an effect of widening the viewing angle was recognized. However, when the polarizing plate was subjected to a long-time wet heat treatment, the contrast when viewed from an oblique direction was reduced, and the visibility was reduced.

Comparative Example 2 The same as Comparative Example 1 except that 100 parts by mass of cellulose acetate having a degree of substitution of acetyl group of 2.6 of Comparative Example 1 was changed to 100 parts by mass of cellulose acetate having a degree of substitution of acetyl group of 2.90. Thus, a comparative optical film 2 having a thickness of 80 μm was produced. As a result, for the comparative optical film 2, Nx−Ny, (Nx + Ny) / 2−Nz, R ₀ , and Rt were determined.
0.00092, R ₀ 18 nm, Rt 75 nm, and at the center, 0.00019, 0.00088, R ₀
15 nm, Rt 70 nm, 0.005 at the opposite end
023,0.00092, R ₀ 19nm, Rt74n
m. The moisture content was measured by the method described above. As a result, it was 2.9%. Using this comparative optical film 1, a polarizing plate was prepared and evaluated in the same manner as in Example 1. When the same evaluation as in Example 1 was performed, the effect of expanding the viewing angle in the horizontal direction was not recognized, and gradation inversion was recognized in the horizontal direction.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 11:00 11:00 C08L 1:10 C08L 1 : 10 F term (reference) 2H049 BA02 BA06 BA07 BA42 BB02 BB13 BB49 BC02 BC22 2H091 FA08X FA08Z FA11X FA11Z FB02 FC01 LA12 LA30 4F071 AA09 AF31 AF35 BA02 BB02 BB07 BC01 BC12 4F210 AA01 AB07 Q01 Q11 Q07 AR06

Claims (24)

[Claims] When a substituent having an acyl group having 2 to 4 carbon atoms as a substituent, a degree of substitution of an acetyl group as A, and a degree of substitution of a propionyl group or a butyryl group as B, the following formula (I) and ( II) An optical film containing a cellulose ester which satisfies the formula at the same time, wherein the refractive index Nx in the slow axis direction and the refractive index Ny in the fast axis direction at a wavelength of 590 nm satisfy the following formula (III). An optical film, which satisfies and has an in-plane retardation R ₀ of 30 nm or more and 200 nm or less. (I) 2.0 ≦ A + B ≦ 3.0 (II) A <2.4 (III) 0.0005 ≦ Nx−Ny ≦ 0.0050 2. A compound having an acyl group having 2 to 4 carbon atoms as a substituent, wherein the degree of substitution of an acetyl group is A and the degree of substitution of a propionyl group or a butyryl group is B, the following (IV)
An optical film containing cellulose ester which satisfies the formulas (V) and (V) at the same time, and further has a refractive index Nx in the in-plane slow axis direction and a refractive index Ny in the fast axis direction at a wavelength of 590 nm in the following formula (VI) ) An optical film satisfying the formula and having an in-plane retardation R ₀ of 30 nm or more and 200 nm or less. (IV) 2.4 ≦ A + B ≦ 2.8 (V) 1.4 ≦ A ≦ 2.0 (VI) 0.0010 ≦ Nx−Ny ≦ 0.0030 3. The refractive index Nx in the slow axis direction, the refractive index Ny in the fast axis direction, and the refractive index Nz in the thickness direction at a wavelength of 590 nm satisfy the following formula (VII). The optical film according to any one of 1 and 2. (VII) 0.0005 ≦ (Nx + Ny) / 2−Nz ≦
0.002 4. The optical film according to claim 1, wherein the viscosity average polymerization degree of the cellulose ester is from 250 to 700. 5. The optical film according to claim 1, wherein the film has a thickness of 20 to 200 μm. 6. The vapor pressure at 200 ° C. is 1333 Pa.
The optical film according to any one of claims 1 to 5, comprising the following plasticizer. 7. The optical film according to claim 1, further comprising an ultraviolet absorber having a distribution coefficient of 9.2 or more. 8. A polarizing plate, wherein the optical film according to claim 1 is adhered to at least one surface of a polarizer or a polarizing plate. 9. A reflective polarizer comprising the optical film according to claim 1. Description: 10. The polarizing plate according to claim 8 or 9, and / or
A display device using the optical film according to any one of claims 1 to 7. 11. Assuming that the compound has an acyl group having 2 to 4 carbon atoms as a substituent, the degree of substitution of an acetyl group is A, and the degree of substitution of a propionyl group or a butyryl group is B, the following (VI)
A film roll obtained by rolling an optical film containing a cellulose ester satisfying the formulas II) and (IX) simultaneously and having an in-plane retardation R _{0 at} a wavelength of 590 nm of 30 nm or more and 200 nm or less. And
An optical film roll wherein the slow axis direction of the optical film is ± 2 degrees with respect to the length direction of the film roll or ± 2 degrees with respect to the width direction of the film roll.
Le. (VIII) 2.0 ≦ A + B ≦ 3.0 (IX) A <2.4 12. When X has an acyl group having 2 to 4 carbon atoms as a substituent, the degree of substitution of an acetyl group is A, and the degree of substitution of a propionyl group or a butyryl group is B, the following (X)
A film roll containing a cellulose ester satisfying the formulas (XI) and (XI) and having an in-plane retardation R _{0 at} a wavelength of 590 nm of more than 30 nm and not more than 100 nm in a roll form. Wherein the slow axis direction of the optical film is ± 2 degrees with respect to the longitudinal direction of the film roll or ± 2 degrees with respect to the width direction of the film roll. Film roll. (X) 2.4 ≦ A + B ≦ 2.8 (XI) 1.4 ≦ A ≦ 2.0 13. When X has an acyl group having 2 to 4 carbon atoms as a substituent, the degree of substitution of an acetyl group is A, and the degree of substitution of a propionyl group or a butyryl group is B, the following (XI
A method for producing an optical film, wherein a solution in which a cellulose ester satisfying both the formulas (I) and (XIII) is simultaneously dissolved in an organic solvent is cast on a support and the solvent is evaporated to form a cellulose ester film. The method for producing an optical film, wherein the cellulose ester film is stretched so as to satisfy the following formula (XIV). (XII) 2.0 ≦ A + B ≦ 3.0 (XIII) A <2.4 (XIV) 0.0005 ≦ Nx−Ny ≦ 0.0050 14. When the compound has an acyl group having 2 to 4 carbon atoms as a substituent, the degree of substitution of an acetyl group is A, and the degree of substitution of a propionyl group or a butyryl group is B, the following (X
A method for producing an optical film in which a solution obtained by dissolving cellulose ester satisfying the formulas (V) and (XVI) simultaneously in an organic solvent is cast on a support and the solvent is evaporated to form a cellulose ester film. The method for producing an optical film, wherein the cellulose ester film is stretched so as to satisfy the following formula (XVII). (XV) 2.4 ≦ A + B ≦ 2.8 (XVI) 1.4 ≦ A ≦ 2.0 (XVII) 0.0010 ≦ Nx−Ny ≦ 0.0030 15. The cellulose ester solution is a cellulose ester solution.
14. A cellulose ester solution having a sester concentration of 20% by mass or more and 35% by mass or less.
15. The method for producing an optical film according to any one of items 14 to 14. 16. When the amount of residual solvent in the cellulose ester film is in the range of 10 to 100% by mass in the step of casting and evaporating the solvent to form the cellulose ester film, the temperature is 15 to 160. The film is stretched in at least one direction at 1.2 ° C. by 1.2 to 2.0 times.
16. The method for producing an optical film according to any one of claims 15 to 15. 17. The method for producing an optical film according to claim 12, wherein the optical film is stretched in two axial directions orthogonal to each other. 18. The method according to claim 13, wherein the stretching ratios in biaxial directions orthogonal to each other are 1.2 to 2.0 times and 0.7 to 1.0 times, respectively. Item 13. The method for producing an optical film according to item 9. 19. The method for producing an optical film according to claim 13, wherein the organic solvent contains at least one organic solvent selected from methyl acetate and acetone. 20. The method according to claim 1, wherein the amount of residual solvent is less than 10% by mass.
The method for producing an optical film according to any one of claims 13 to 19, wherein the heat treatment is performed at a temperature of 30 to 200C for 10 seconds or more. 21. A film which has been cooled to 100 ° C. or less and has a residual solvent content of less than 10% by mass is heat treated again at a temperature of 130 to 200 ° C. for 10 seconds or more.
20. The method for producing an optical film according to any one of claims 19 to 19. 22. A cellulose ester solution at 200 ° C.
The method for producing an optical film according to any one of claims 13 to 21, further comprising a plasticizer having a vapor pressure of 1333 Pa or less. 23. When the compound has an acyl group having 2 to 4 carbon atoms as a substituent, the degree of substitution of an acetyl group is A, and the degree of substitution of a propionyl group or a butyryl group is B, the following (XV
A solution containing at least a cellulose ester satisfying the formulas (III) and (XIX) at the same time, a plasticizer having a vapor pressure of 1333 Pa or less at 200 ° C., and an organic solvent is cast on a support, peeled off, and further separated. Was evaporated to form a cellulose ester film, and the amount of residual solvent was 10
A method for producing an optical film, comprising stretching at a temperature of from 130 to 200 ° C. to satisfy the following formula (XX) when the amount is less than mass%. (XVIII) 2.0 ≦ A + B ≦ 3.0 (XIX) A <2.4 (XX) 0.0005 ≦ Nx−Ny ≦ 0.0050 24. When the compound has an acyl group having 2 to 4 carbon atoms as a substituent, the degree of substitution of an acetyl group is A, and the degree of substitution of a propionyl group or a butyryl group is B, the following (XX)
A solution containing at least a cellulose ester satisfying the formulas (I) and (XXII) at the same time, a plasticizer having a vapor pressure at 200 ° C. of 1333 Pa or less, and an organic solvent is cast on a support, peeled off, and further solvent removed. Is evaporated to form a cellulose ester film, and when the residual solvent amount is less than 2% by mass, at a temperature of 130 to 200 ° C., the following (XX)
III) A method for producing an optical film, wherein the film is stretched so as to satisfy the formula. (XXI) 2.0 ≦ A + B ≦ 2.8 (XXII) 1.4 ≦ A ≦ 2.0 (XXIII) 0.0010 ≦ Nx−Ny ≦ 0.0030