JP2002277632A - Optical compensation sheet, method for manufacturing the same, polarizing plate and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display with few defects occurring on a display screen due to adhesion of dust and with excellent viewing angle characteristics. SOLUTION: The liquid crystal display utilizes an optical compensation sheet composed of a polymer film with an in-plane retardation value in 20-70 nm range, with a retardation value in the thickness direction in 70-400 nm range and with >=1 g scratch hardness of at least one surface thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical compensatory sheet and a method for producing the same, a polarizing plate, and a liquid crystal display.

[0002]

2. Description of the Related Art As an optical compensation sheet (retardation film) used in a liquid crystal display device, a synthetic polymer film having a high retardation value such as a polycarbonate film, a polysulfone film, a polystyrene film, a polyvinyl alcohol film, etc. is widely used. Have been. On the other hand, it is known that cellulose acetate film has higher optical isotropy than the above-mentioned polymer film, and it has been difficult to increase the retardation value. Therefore, it is common to use a cellulose acetate film for applications requiring optical isotropy, for example, for a polarizing plate. However, European patent 0
No. 911656A2 discloses a cellulose acetate film having a high retardation value that can be used in applications requiring optical anisotropy, contrary to conventional general principles. It is described that a liquid crystal display device having high display quality can be obtained by inserting the cellulose acetate film between a polarizing plate and a liquid crystal cell.

[0003]

In the production process of the polymer film used for such an optical compensatory sheet, there was a problem that the film was scratched. Further, there is another problem that dust derived from scratches is generated from the film, and the dust adheres to the film. In order to prevent the generation and adhesion of such scratches and dust, there is a problem that web handling is difficult. The optical compensatory sheet made of a polymer film is usually bonded to a polarizing plate and then to a liquid crystal display together with the polarizing plate. Even in such a bonding step, there is a problem that abrasion occurs or dust adheres when the film roll is transported. There has been a problem that abrasions and attached dust appear as defects on the liquid crystal display device. An object of the present invention is to provide an optical compensatory sheet capable of suppressing generation of scratches and generation and adhesion of dust, and a polarizing plate and a liquid crystal display device using the same.

[0004]

Means for Solving the Problems The present inventors have made it possible to prevent scratches occurring on a polymer film by making the surface of the polymer film used for an optical compensatory sheet have a scratching strength of 1 g or more, thereby preventing generation and adhesion of dust. We found that it could be prevented. Details of the method for setting the scratch strength to 1 g or more will be described later. An object of the present invention is to provide an optical compensatory sheet of the following (1) to (7), a method for producing an optical compensatory sheet of the following (8) and (9), a polarizing plate of the following (10), and a following (11).
This has been attained by the liquid crystal display device of (13). (1) A polymer film having an in-plane retardation value in the range of 20 to 70 nm and a thickness direction retardation value in the range of 70 to 400 nm, and scratching at least one surface of the polymer film. An optical compensation sheet having a strength of 1 g or more. The in-plane retardation and the retardation in the thickness direction of the polymer film are defined by the following formulas (I) and (II), respectively. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d where nx and ny are in-plane refractive indices of the transparent film, and nz is thickness. Index of refraction in the direction, and d is
This is the thickness of the transparent film. And the value of the scratching strength is
It means the weight (g) when the surface of the optical compensatory sheet is scratched using a sapphire needle having a cone apex angle of 90 degrees and a tip diameter of 0.25 mm, and the scratch mark is visually observed.

(2) The optical compensatory sheet according to (1), wherein the dynamic friction coefficient of the surface of the polymer film is 0.40 or less. (3) A transparent conductive layer having a surface resistivity of 10 ¹² Ω / □ or less is provided on at least one surface of the polymer film, and the haze of the polymer film having the transparent conductive layer is 2.0% or less. The optical compensation sheet according to (1) or (2), which is characterized in that: (4) The polymer film has an acetylation degree of 57.0 to 6
The optical compensatory sheet according to any one of (1) to (3), which is composed of cellulose acetate in a range of 1.5%.

(5) The method according to (4), wherein the aromatic compound having at least two aromatic rings is contained in an amount of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acetate. The optical compensation sheet according to the above. (6) The optical compensation sheet according to (4), wherein the polymer film is a stretched product stretched at a magnification of 3 to 100%. (7) The aromatic compound has at least one 1,3,5-
The optical compensatory sheet according to (5), having a triazine ring.

(8) A polymer film having an in-plane retardation value in the range of 20 to 70 nm and a retardation value in the thickness direction of 70 to 400 nm, and one surface of the polymer film. A method for producing an optical compensatory sheet having a scratch strength of 1 g or more, comprising forming the polymer film into a film by a co-casting method or a sequential casting method, thereby forming the polymer film from a polymer layer comprising a polymer. As a film composed of a polymer and a surface layer containing fine particles having an average particle diameter of 1.0 μm or less on at least one surface, the surface of the polymer film on which the surface layer is provided has a scratch strength of 1 g or more. Manufacturing method of optical compensation sheet. (9) Further, fine particles having an average particle diameter of 1.0 μm or less are added to the polymer layer, and the amount of the fine particles added to the polymer in the surface layer is larger than the amount of the fine particles added to the polymer in the polymer layer ( The method for producing an optical compensation sheet according to 8).

(10) A polarizing plate comprising a polarizing film and two transparent protective films disposed on both sides thereof, wherein one of the transparent protective films is described in any one of (1) to (7). The polarizing plate, wherein the slow axis of the optical compensating sheet and the transmission axis of the polarizing film are substantially parallel to each other. (11) A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein any one of (1) to (7) is provided between the liquid crystal cell and at least one polarizing plate. A liquid crystal display device, comprising: an optical compensation sheet according to any one of (1) to (3), wherein the slow axis of the optical compensation sheet and the transmission axis of the polarizing film are substantially parallel to each other. .

(12) A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein at least one of the polarizing plates is the polarizing plate according to (10). (13) The liquid crystal cell is an OCB mode, VA mode or TN mode liquid crystal cell (11) or (12).
3. The liquid crystal display device according to 1. In this specification, "substantially parallel" means that the angle is within a range of less than ± 3 ° from the strict angle. This range is preferably less than ± 2 °, and more preferably less than ± 1 °.

[0010]

The inventor of the present invention has set the polymer film used for the optical compensation sheet to have a scratching strength of 1 g or more, and more preferably by providing a transparent conductive layer, so that generation of scratches and generation and adhesion of dust can be prevented. The liquid crystal cell was optically compensated (without display defects caused by dust). By adjusting the type and amount of an additive (specifically, an aromatic compound having two aromatic rings) to a polymer film (preferably a cellulose acetate film) or manufacturing conditions (eg, film stretching conditions) , Re retardation value is from 20 to 70
A polymer film having an Rth retardation value in the range of 70 to 400 nm is obtained.
This polymer film has sufficient optical anisotropy to optically compensate the liquid crystal cell, and can be used as an optical compensation sheet. In the present invention, the polymer film used for the optical compensation sheet has a thickness of 1.0 μm.
m by adding fine particles having an average particle diameter of not more than
An optical compensatory sheet having a haze of 2.0% or less and a coefficient of kinetic friction of the surface of 0.40 or less, having excellent scratching strength and free from dust is obtained.

When a cellulose acetate film is used as the polymer film, the degree of acetylation is 57.0%.
When the cellulose acetate is less than the above, the above-mentioned optical anisotropy can be easily achieved, but the physical properties of the cellulose acetate film deteriorate. In the present invention, cellulose acetate having a degree of acetylation of 57.0 to 61.5% is used, and other means (adjustment of the above-mentioned additives and production conditions)
By achieving the above retardation value, a cellulose acetate film having both excellent optical anisotropy and physical properties is obtained. The protective film of the polarizing plate is generally made of a cellulose acetate film. When an optical compensatory sheet made of the above polymer film (preferably cellulose acetate film) is used as one protective film of the polarizing plate, an optical compensation function is added to the polarizing plate without increasing the number of components of the polarizing plate. be able to. An optical compensatory sheet made of the above-mentioned polymer film (preferably cellulose acetate film) and a polarizing plate using the above-mentioned cellulose acetate film as a protective film are made of V
A (Vertically Aligned) type, OCB (Optically Comp
The present invention can be particularly advantageously used for an ensated bend) or TN (Twisted Nematic) type liquid crystal display device.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Retardation of polymer film] Re retardation value and Rth of a film
The retardation values are defined by the following formulas (I) and (II), respectively. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d In the formulas (I) and (II), nx is a slow axis direction in the film plane ( (The direction in which the refractive index becomes the maximum). In the formulas (I) and (II), ny is the refractive index in the fast axis direction (direction in which the refractive index is minimum) in the film plane. In the formula (II), nz is a refractive index in the thickness direction of the film. In formulas (I) and (II), d
Is the film thickness in nm.

In the present invention, the Re retardation value of the polymer film is in the range of 20 to 70 nm, and R
The th retardation value is adjusted in the range of 70 to 400 nm. When two optically anisotropic polymer films are used in a liquid crystal display device, the Rth retardation value of the film is preferably from 70 to 250 nm. When one optically anisotropic polymer film is used for a liquid crystal display device, the Rth retardation value of the film is 150.
It is preferably from 400 to 400 nm. The birefringence (Δn: nx−ny) of the polymer film is 0.00
It is preferably from 025 to 0.00088. Further, the birefringence in the thickness direction of the polymer film ｛(nx +
ny) / 2-nz} is from 0.00088 to 0.005
It is preferred that Further, the refractive index nx in the in-plane slow axis direction, the refractive index ny in the direction perpendicular to the slow axis in the plane, and the refractive index nz in the thickness direction are 1 ≦ (nx−nz) / (n)
It is preferable that the retardation plate satisfies the relationship of (x-ny) ≦ 2.

[Slow axis angle of film] The angle of the slow axis in the plane of the polymer film is defined by the angle between the slow axis and the reference line with the width direction of the roll film as a reference line (0 °). . Clockwise is defined as +. The absolute value of the average value of the slow axis angle is preferably 3 ° or less, more preferably 2 ° or less, and most preferably 1 ° or less. The direction of the average value of the slow axis angle is defined as the average direction of the slow axis. The standard deviation of the slow axis angle is preferably 1.5 ° or less, more preferably 0.8 ° or less, and most preferably 0.4 ° or less.

[Polymer] As the polymer used in the polymer film of the present invention, a synthetic polymer such as polycarbonate, polysulfone, polystyrene, polyvinyl alcohol and the like and a cellulose derivative derived from a natural product are used. Among them, cellulose esters are preferred, and lower fatty acid esters of cellulose are more preferred. The lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. The degree of acetylation of cellulose acetate is preferably 57.0 to 61.5%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is ASTM: D-817
According to the measurement and calculation of the degree of acetylation in -91 (test method for cellulose acetate or the like). The viscosity average degree of polymerization (DP) of cellulose acetate is preferably 250 or more, more preferably 290 or more. Further, cellulose acetate used in the present invention,
Mw / by gel permeation chromatography
It is preferable that the molecular weight distribution of Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) is narrow. Specific Mw / Mn
As the value of, for example, in a chloroform solution,
It is preferably from 1.0 to 1.7, more preferably from 1.3 to 1.65, and even more preferably from 1.4 to 1.
Most preferably, it is 6.

[Retardation Raising Agent] In order to adjust the retardation of the polymer film (preferably, cellulose acetate film), it is preferable to use an aromatic compound having at least two aromatic rings as the retardation raising agent. The aromatic compound is used in an amount of 0.01 to 20 parts by mass based on 100 parts by mass of the polymer (preferably, cellulose acetate). The aromatic compound is used in an amount of 0.0
Preferably used in the range of 5 to 15 parts by mass,
More preferably, it is used in the range of 0.1 to 10 parts by mass. Two or more aromatic compounds may be used in combination.
The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

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

The number of aromatic rings in the aromatic compound is 2
To 20, preferably 2 to 12, more preferably 2 to 8, and most preferably 2 to 6. The bonding relationship between two aromatic rings is as follows: (a) when forming a condensed ring, (b)
It can be classified into a case where a single bond is directly bonded and a case where it is bonded via a (c) linking group (a spiro bond cannot be formed due to an aromatic ring). The connection relationship may be any of (a) to (c).

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

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

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

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

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

The number of carbon atoms of the alkylthio group is 1 to 1
It is preferably 2. Examples of the alkylthio group include methylthio, ethylthio and octylthio.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl. The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include acetamide. The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamide group include methanesulfonamide, butanesulfonamide and n-octanesulfonamide. The aliphatic substituted amino group preferably has 1 to 10 carbon atoms. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino. The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl. The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic-substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl. The aliphatic substituted ureido group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted ureido group include methyl ureide. Examples of the non-aromatic heterocyclic group include piperidino and morpholino. The molecular weight of the retardation increasing agent is preferably from 300 to 800. As an example of a retardation increasing agent, JP-A-200
0-1111014 and JP-A-2000-275434
Can be mentioned.

[Production of Polymer Film] The production of a polymer film will be described with reference to a cellulose acetate film which is preferable as a polymer film. It is preferable to produce a cellulose acetate film by a solvent casting method. In the solvent casting method, a film is manufactured using a solution (dope) in which a polymer is dissolved in an organic solvent. The organic solvent has 3 to 1 carbon atoms.
It is preferable to include a solvent selected from ethers having 2 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 that the halogenated hydrocarbon is not contained due to suitability for the production environment, and in that case, it is more preferable that the halogenated hydrocarbon contains ether, ketone, ester, or a mixed solvent of these organic solvents. Ethers, ketones and esters may have a cyclic structure. Compounds 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 is
It 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 range specified for the compound having any one of the functional groups.

Examples of the ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole and phenetole. Examples of the 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 functional groups include:
Includes 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol. The number of carbon atoms in the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogenated hydrocarbons in which hydrogen atoms are replaced by halogens is preferably 25 to 75 mol%, and preferably 3 to 75 mol%.
The content is more preferably 0 to 70 mol%, further preferably 35 to 65 mol%, and more preferably 40 to 60 mol%.
Most preferably, it is mol%. Methylene chloride is a typical halogenated hydrocarbon. Two or more organic solvents may be used as a mixture.

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 (normal temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a usual solvent casting method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly, methylene chloride) as the organic solvent. The amount of cellulose acetate is adjusted so that the obtained solution contains 10 to 40% by mass. More preferably, the amount of cellulose acetate is 10 to 30% by mass. In the organic solvent (main solvent), any additives described below may be added. The solution can be prepared by stirring cellulose acetate and an organic solvent at normal temperature (0 to 40 ° C.). The highly concentrated solution may be stirred under pressure and heating conditions. Specifically, the cellulose acetate and the organic solvent are put in a pressurized container and hermetically sealed, and the mixture is stirred while being heated under pressure 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., and more preferably 80 to 110 ° C.

Each component may be roughly mixed in advance and then placed in a container. Moreover, you may put in a container sequentially. The container must be configured to be able to stir. The container can be pressurized by injecting an inert gas such as nitrogen gas. Further, an increase in the vapor pressure of the solvent due to heating may be used.
Alternatively, each component may be added under pressure after the container is sealed. When heating, it is preferable to heat from outside the container. For example, a jacket-type heating device can be used. Further, a plate heater may be provided outside the container, and the entire container may be heated by circulating the liquid through piping. It is preferable to provide a stirring blade inside the container and stir using the stirring blade. The stirring blade preferably has a length reaching the vicinity of the container wall. It is preferable to provide a scraping blade at the end of the stirring blade to renew the liquid film on the wall of the container. Instruments such as a pressure gauge and a thermometer may be installed in the container. Dissolve each component in the solvent in the container.
The prepared dope is taken out of the container after cooling, or is taken out and then cooled using a heat exchanger or the like.

The solution can be prepared by the cooling dissolution method. In the cooling dissolution method, cellulose acetate can be dissolved even in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can dissolve cellulose acetate by an ordinary dissolution method, the cooling dissolution method has an effect that a uniform solution can be obtained quickly. In the cooling dissolution method, first, cellulose acetate is gradually added to an organic solvent at room temperature while stirring. It is preferable that the amount of cellulose acetate is adjusted to be 10 to 40% by mass in the mixture. More preferably, the amount of cellulose acetate is 10 to 30% by mass. Further, an optional additive described below may be added to the mixture.

Next, the mixture is cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -10 ° C).
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.). Upon such cooling, the mixture of cellulose acetate and the organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more.
Most preferably, the temperature is at least ° C / min. The cooling rate is preferably as fast as possible, but 10,000 ° C./sec is the theoretical upper limit, 1000 ° C./sec is the technical upper limit, and
00 ° C / sec is a practical upper limit. The cooling rate is
This is a value obtained by dividing the difference between the temperature at which cooling is started and the final cooling temperature by the time from when cooling is started to when the temperature reaches the final cooling temperature.

Further, the temperature is raised to 0 to 200 ° C (preferably 0 to 150 ° C, more preferably 0 to 120 ° C,
When heated to the temperature (most preferably 0 to 50 ° C.), the cellulose acetate dissolves in the organic solvent. The temperature may be raised only by leaving it at room temperature or may be heated in a warm bath. The heating rate is preferably 4 ° C./min or more, and 8 ° C./min.
Minutes or more, and most preferably 12 ° C./minute or more. The heating rate is preferably as high as possible, but the theoretical upper limit is 10,000 ° C./sec.
0 ° C./sec is a technical upper limit, and 100 ° C./sec is a practical upper limit. Note that the heating rate is a value obtained by dividing the difference between the temperature at which heating is started and the final heating temperature by the time from when heating is started to when the final heating temperature is reached. . As described above, a uniform solution is obtained. If the dissolution is insufficient, the operation of cooling and heating may be repeated. Whether or not the dissolution is sufficient can be determined only by visually observing the appearance of the solution.

In the cooling dissolution method, it is desirable to use a closed container in order to avoid water contamination due to condensation during cooling. Also, in the cooling and heating operation, pressurization during cooling,
By reducing the pressure during the heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container. According to differential scanning calorimetry (DSC), a 20% by mass solution of cellulose acetate (degree of acetylation: 60.9%, viscosity average degree of polymerization: 299) dissolved in methyl acetate by a cooling dissolution method was 3%.
A pseudo phase transition point between the sol state and the gel state exists at around 3 ° C., and below this temperature, the gel state becomes uniform. Therefore,
This solution must be stored at a temperature equal to or higher than the quasi phase transition temperature, preferably at a temperature of about 10 ° C. plus the gel phase transition temperature. However, this pseudo phase transition temperature differs depending on the acetylation degree of cellulose acetate, the viscosity average polymerization degree, the solution concentration and the organic solvent used.

The prepared cellulose acetate solution (dope) is preferably filtered using a filter before film production in order to remove dust and insolubles. For filtration, any filter made of a material that does not dissolve in a solvent with a filter having a smaller pore diameter than foreign substances that can be confirmed when used as an optical compensation sheet, such as filter paper or a metal sintered filter, can be preferably used. Preferably, the filter has a retention particle size of 20 μm or less, more preferably 1 μm or less.
0 μm or less. When the filter is filter paper, the filter paper preferably has a drainage time of 20 seconds or more.

From the prepared cellulose acetate solution (dope), a cellulose acetate film is produced by a solvent casting method. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. It is preferable that the surface of the drum or the band is finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. Nos. 2,336,310 and 23,676.
No. 03, No. 2492078, No. 2492977, No. 2492978, No. 2607704, No. 27390
Nos. 69 and 2739070, British Patent 640731
Nos. 736892 and JP-B-45-455.
No. 4, No. 49-5614, JP-A-60-176834.
And JP-A-60-203430 and JP-A-62-115035. 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 by blowing on air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried with hot air having a temperature gradually changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in JP-B-5-17844. According to this method, the time from casting to stripping can be reduced. In order to carry out this method, it is necessary that the dope gels at the surface temperature of the drum or band during casting.

As the dope, a material obtained by crushing the cellulose acetate film is mixed as a raw material, and the cost can be reduced by reusing the raw material. By reusing the filtered film with reduced foreign matter as a raw material, the life of the filter can be advantageously extended. The mixing ratio with respect to the raw material can be suitably set at any of 0 to 100% by mass, but as a continuous process, 10 to 70% by mass is more preferable.

[Plasticizer] A plasticizer can be added to the polymer film in order to improve mechanical properties or to increase the drying speed. As a plasticizer,
Phosphate or carboxylate esters are used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCC).
P) is included. Representative carboxylic esters include phthalic esters and citric esters. Examples of phthalate esters include dimethyl phthalate (DM
P), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include O-acetyl triethyl citrate (OACT
E) and tributyl O-acetylcitrate (OACT
B) is included. Examples of other carboxylic esters include butyl oleate, methylacetyl ricinoleate,
It includes dibutyl sebacate and various trimellitate esters. Phthalate ester plasticizers (DMP, DE
P, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The amount of the plasticizer added is preferably 5 to 30% by mass, more preferably 5 to 20% by mass, and most preferably 5 to 15% by mass of the amount of the polymer.

[Deterioration inhibitor] The polymer film may be added with a degradation inhibitor (eg, antioxidant, peroxide decomposer, radical inhibitor, metal deactivator, acid scavenger, amine). Good. Regarding the deterioration inhibitor, see JP-A-3-1992
No. 01, 5-1907073, 5-194789
And JP-A-5-271471 and JP-A-6-107854. The amount of the deterioration inhibitor to be added is preferably 0.01 to 1% by mass, more preferably 0.01 to 0.2% by mass of the solution (dope) to be prepared. When the addition amount is less than 0.01% by mass, the effect of the deterioration inhibitor is hardly recognized. 1% by mass
Exceeding the limit may cause bleed-out (bleeding out) of the deterioration inhibitor onto the film surface. Particularly preferred examples of the deterioration inhibitor include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

[Stretching Treatment] The retardation of the polymer film can be adjusted by stretching treatment by further applying tension in the stretching direction. The stretching ratio is preferably 3 to 100%. In the cellulose ester film, the refractive index (refractive index nx in the in-plane slow axis direction, refractive index ny in the direction perpendicular to the in-plane slow axis, and refractive index nz in the thickness direction) is further adjusted by stretching treatment. Is preferred. When the intrinsic birefringence is positive, the refractive index increases in the direction in which the polymer chains are oriented. When such a polymer having a positive intrinsic birefringence is stretched, the refractive index usually becomes nx> ny ≧ nz. This is because the polymer component oriented in the in-plane direction has increased x component by stretching,
This is because the z component becomes the smallest. Thereby, 1 ≦
The relationship (nx-nz) / (nx-ny) can be satisfied. Further, (nx−nz) / (nx−ny) ≦
In order to satisfy the relationship of 2, the stretching ratio of uniaxial stretching may be controlled, or the refractive index may be adjusted by performing unbalanced biaxial stretching. Specifically, uniaxial stretching or unbalanced biaxial stretching is performed so that the maximum stretching ratio SA and the stretching ratio SB in the direction perpendicular to the stretching direction satisfy the relationship of 1 <SA / SB ≦ 3. What is necessary is just to implement. The stretching ratio is a relative value when the length before stretching is set to 1. SB may be a value less than 1 (in other words, contract). If the relationship of the above expression is satisfied, SB
May be a value less than 1. The stretching process may be a simultaneous process or a sequential process.

In the stretching process, the solvent content of the film is preferably 70% by mass or less. If the content is too high, it is difficult to handle, and it is difficult to carry out stretching orientation, and the stretching efficiency deteriorates. On the other hand, when the content is small, the apparent elastic modulus and the stretching stress at the time of stretching become large, so a large-scale facility is required, which is disadvantageous in terms of equipment cost, and is also easy to cut at the time of stretching, which is disadvantageous. Specifically, the solvent content of the film at the time of stretching is from 1% by mass to 70% by mass at the start of stretching, and from 0.1% by mass to 20% at the end of stretching.
It is preferable that the amount is not more than mass%. The stretching tension is preferably such that the load per width is 1 t / m or less.

[Thickness] The thickness of the polymer film is 40
To 140 μm, preferably 70 to 120 μm.
More preferably, it is μm.

[Fine Particles] It is preferable to add fine particles having an average particle diameter of 1.0 μm or less to the polymer film (preferably, cellulose acetate film). There is no particular limitation on the form in which the fine particles are contained in the polymer film, and the fine particles may be uniformly contained in the polymer film. It may have a surface layer containing fine particles.

The fine particles function as a slip agent to improve the coefficient of kinetic friction of the film and improve the scratching strength. It is preferable to use an inorganic compound as the fine particles. Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate And calcium phosphate. Preferred are silicon dioxide, titanium dioxide and zirconium oxide, with silicon dioxide being particularly preferred. In the fine particles of the inorganic compound, a methyl group can be introduced to the particle surface by surface treatment. For example, fine particles of silicon oxide may be treated with dichlorodimethylsilane or bis (trimethylsilyl) amine.

Fine particles of silicon dioxide are already commercially available (eg, Aerosil R972 ™, R972D ™, R9
74TM, R812TM, manufactured by Nippon Aerosil Co., Ltd.). Also, there are commercially available zirconium oxide fine particles (eg,
Aerosil R976TM, R811TM, manufactured by Nippon Aerosil Co., Ltd.). The average particle size of the fine particles is preferably 1.0 μm or less. The average particle size is more preferably from 0.1 to 1.0 μm, and most preferably from 0.1 to 0.5 μm. The fine particles are preferably used in an amount of 0.001 to 0.3% by mass based on the polymer (preferably, cellulose acetate).
More preferably, it is used in an amount of 1 to 0.1% by mass.

The polymer film having a surface layer containing fine particles is formed by forming the polymer film into a film by a co-casting method or a sequential casting method. And a surface layer containing fine particles having an average particle diameter of 1.0 μm or less. Further, fine particles having an average particle diameter of 1.0 μm or less are added to the polymer layer, and the amount of the fine particles added to the polymer in the surface layer is preferably larger than the amount of the fine particles added to the polymer in the polymer layer. Further, a surface layer containing fine particles may be provided by applying a solution containing a polymer and fine particles. As a device for casting, in the case of the co-casting method, an internal joining die, a tip joining die, or the like can be used. In the case of the sequential casting method, an extrusion die or the like can be used. . The haze of the film in the present invention is preferably 2.0% or less.

When a surface layer is provided on the polymer layer, fine particles may not be added to the polymer layer as long as fine particles are added to the surface layer. The addition amount of the fine particles in the polymer layer is determined by the polymer (preferably cellulose acetate).
Is preferably in the range of 0.001 to 0.05% by mass, and more preferably in the range of 0.001 to 0.01% by mass, with respect to the amount of. It is preferable that the addition amount of the fine particles in the surface layer is larger than the addition amount of the fine particles in the polymer layer. The addition amount of the fine particles in the surface layer is preferably in the range of 0.001 to 0.05% by mass based on the amount of the polymer (preferably, cellulose acetate).
More preferably, it is in the range of 0.01 to 0.02% by mass. The types of the polymer of the polymer layer and the surface layer may be the same or different. The thickness of the surface layer is preferably in the range of 0.2 to 50 μm, more preferably in the range of 0.5 to 20 μm, and particularly preferably in the range of 0.5 to 5 μm.

[Coefficient of Dynamic Friction] The coefficient of dynamic friction of at least one surface of the polymer film is preferably 0.40 or less. The dynamic friction coefficient is more preferably 0.35 or less, further preferably 0.30 or less, and most preferably 0.25 or less. The dynamic friction coefficient is preferably as low as possible, but the lower limit is about 0.10. The dynamic friction coefficient can be easily measured using a steel ball according to a method specified by JIS or ASTM.

[Scratch Strength] The scratch strength of at least one surface of the polymer film of the present invention takes a value of 1 g or more. Thus, various problems such as generation of scratches and generation of dust when handling the film can be solved. The larger the value of the scratching strength is, the more preferable it is. However, the value is generally 100 g or less. More preferably, the value of the scratch strength is in the range of 1.5 to 50 g. The value of the scratching strength is the weight (g) when the surface of the optical compensatory sheet is scratched with a sapphire needle having a cone apex angle of 90 degrees and a tip diameter of 0.25 mm, and the scratches are visually observed. To evaluate.

[Transparent Conductive Layer] The polymer film may be provided with a transparent conductive film by using a surfactant, a dispersion of conductive fine particles, or the like. No problem. In order to impart antistatic properties, it is more preferable to provide a transparent conductive film. The transparent conductive film may be provided by coating,
It may be provided by co-casting at the time of film casting. Further, a transparent conductive film may be formed by a vacuum film formation method such as sputtering, vacuum evaporation, or ion plating. A transparent conductive film may be provided on one side of the film, or may be provided on both sides. Also, these methods can be used in combination. Further, it may be used in combination with (or shared with) the above-mentioned surface layer containing fine particles. Conductive fine particles may be added to the polymer layer or the surface layer. There is no particular limitation on the order of lamination of the surface layer containing the fine particles and the transparent conductive film, but it is preferable to provide a surface layer containing the fine particles on the outermost layer in order to impart scratching strength. The present invention is characterized in that a transparent conductive film is formed as an adhesive layer or an easy-adhesion layer, whereby an optical compensatory sheet with less adhesion of dust and good adhesiveness can be obtained.

As the surfactant, any of nonionic and ionic (anion, cation, betaine) can be used. Further, a fluorine-based surfactant is also preferably used as a coating agent in an organic solvent or as an antistatic agent. The surfactant used in the present invention is described in Application of Surfactant (Koshobo, Takao Karimei, published on September 1, 1980). In the present invention, a preferred surfactant is not particularly limited in its use amount, and any surfactant may be used as long as desired surfactant properties can be obtained. In addition, the coating amount of these surfactants is preferably 0.02 to 1000 mg, and more preferably 0.05 to 200 mg per 1 m ² .

The transparent conductive film using the conductive fine particle dispersion is basically formed by a method such as coating a layer containing fine particles of at least one kind of metal and / or metal oxide or metal nitride. Can be formed. Fine particles composed of one or more metals include gold, silver, copper, aluminum,
Metals such as iron, nickel, palladium, and platinum or alloys thereof are exemplified. Particularly, silver is preferable, and an alloy of palladium and silver is more preferable from the viewpoint of weather resistance. The content of palladium is preferably 5 to 30% by mass,
When the amount of palladium is small, the weather resistance is poor, and when the amount of palladium is large, the conductivity decreases. Examples of a method for preparing metal fine particles include a method for preparing fine particles by a low vacuum evaporation method and a method for preparing a metal colloid in which an aqueous solution of a metal salt is reduced with a reducing agent such as iron (II), hydrazine, boron hydride, or hydroxyethylamine. No. Metal oxides include In ₂ O ₃ -based (including doped products such as Sn), SnO ₂ -based (including doped products such as F and Sb), and ZnO-based (including Al and Ga).
TiO ₂ , Al ₂ O ₃ , SiO
₂ , MgO, BaO, MoO ₃ , V ₂ O ₅ , or a composite thereof. Ti as metal nitride
N and the like.

The average particle size of these conductive fine particles is 1.0 to
700 nm is preferred, 2.0 to 300 nm is more preferred, and 5.0 to 100 nm is most preferred. If the particle size is too large, light absorption by the conductive fine particles increases,
For this reason, the light transmittance of the particle layer is reduced, and at the same time, the haze is increased. When the average particle diameter of these conductive fine particles is less than 1 nm, dispersion of the fine particles becomes difficult,
Since the surface resistance of the fine particle layer rapidly increases, it is not possible to obtain a coating having a low resistance value that can prevent the adhesion of dust.

When a film is formed on a polymer film by sputtering or the like, the surface thereof is made of a fluororesin, an acrylic resin,
Polymers such as silicon-based resins, propylene-based resins, and vinyl-based resins, and SiO ₂ , TiO ₂ , ZrO ₂ , and SnO ₂
It is preferable to coat with an inorganic substance such as. The coating thickness is preferably 10 nm or more and 100 μm or less,
It is more preferably 10 nm or more and 50 μm or less, particularly preferably 10 nm or more and 10 μm or less. It is preferable to cool the substrate during sputtering or the like. It is preferably -30 ° C or more and 30 ° C or less, more preferably -30 ° C or more and 20 ° C or less, and particularly preferably -30 ° C or less.
It is not less than 10 ° C and not more than 10 ° C. As a method for forming a film mainly containing indium oxide by a sputtering method, reactive sputtering using a metal target containing indium as a main component or a target which is a sintered body mainly containing syndium oxide is used. it can. The latter is preferred for controlling the reaction. In the reactive sputtering method, an inert gas such as argon is used as a sputtering gas, and oxygen is used as a reactive gas. As a discharge type, DC magnetron sputtering, RF magnetron sputtering, or the like can be used. As a method for controlling the flow rate of oxygen, it is preferable to use a plasma emission monitor method.

The light transmittance of the polymer film is 50%.
Or more, more preferably 60% or more, particularly preferably 70% or more,
Most preferably, it is at least 80%. Haze is preferably 2% or less, more preferably 1.5% or less, and 1.0% or less.
The following are most preferred. The lower the haze value, the better, but generally it is 0.5% or more.

[Surface Treatment of Polymer Film] When a polymer film is used as a transparent protective film of a polarizing plate, it is preferable to treat the surface of the polymer film. As the surface treatment, a corona discharge treatment, a glow discharge treatment, a flame treatment, an acid treatment, an alkali treatment, or an ultraviolet irradiation treatment is performed. It is particularly preferable to carry out an acid treatment or an alkali treatment, that is, a saponification treatment for cellulose acetate.

[Polarizing Plate] The polarizing plate comprises a polarizing film and two transparent protective films disposed on both sides thereof. As one protective film, the above-mentioned polymer film can be used. For the other protective film, a normal cellulose acetate film may be used. The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. It is preferable to arrange the polymer film such that the slow axis of the polymer film is substantially parallel to the transmission axis of the polarizing film. That is, the angle between the slow axis of the polymer film and the transmission axis of the polarizing film is preferably 3 ° or less, more preferably 2 ° or less, and more preferably 1 ° or less. It is most preferable to arrange them in such a manner.

[Liquid Crystal Display Device] The optical compensatory sheet made of the above polymer film or the polarizing plate using the above polymer film is advantageously used for a liquid crystal display device, especially for a transmission type liquid crystal display device. The transmission type liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides of the liquid crystal cell. The polarizing plate includes a polarizing film and two transparent protective films disposed on both sides of the polarizing film. A liquid crystal cell carries a liquid crystal between two electrode substrates. One optical compensation sheet is provided between the liquid crystal cell and one polarizing plate, or two optical compensation sheets are provided between the liquid crystal cell and both polarizing plates. It is preferable that the slow axis of the optical compensation sheet and the transmission axis of the polarizing film are arranged substantially parallel to each other. In a polarizing plate, the above-mentioned polymer film is used as a transparent protective film disposed between a liquid crystal cell and a polarizing film. Either use the above polymer film only for the transparent protective film (between the liquid crystal cell and the polarizing film) of one polarizing plate, or use two transparent protective films (between the liquid crystal cell and the polarizing film) of both polarizing plates The above-mentioned polymer film is used for the film. It is preferable that the slow axis of the optical compensation sheet and the transmission axis of the polarizing film are arranged substantially parallel to each other. The liquid crystal cell is preferably in an OCB mode, a VA mode, or a TN mode.

In a VA mode liquid crystal cell, rod-like liquid crystal molecules are oriented substantially vertically when no voltage is applied. VA
The liquid crystal cell of the mode includes (1) a VA mode liquid crystal cell in a narrow sense in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. 2-176625). In addition, (2) VA mode is multi-domain (M) for widening the viewing angle.
Liquid crystal cell (VA mode) (SID97, Digest of tec)
h. Papers (Preprints) 28 (1997) 845),
(3) A liquid crystal cell (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 voltage is applied (Preprints 58 to 59 (1998). ))) And (4)
Includes SURVAIVAL mode liquid crystal cells (presented 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 crystal molecules are substantially (symmetrically) aligned in upper and lower directions of the liquid crystal cell. And disclosed in U.S. Pat. Nos. 4,583,825 and 5,410,422. 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 OCB
(Optically Compensatory Bend) Also called liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage that the response speed is high. In the case of an OCB mode liquid crystal display device, the optical compensation sheet of the present invention may have an optically anisotropic layer containing a disc-shaped compound or a rod-shaped liquid crystal compound on a polymer film (preferably a cellulose acetate film). . The optically anisotropic layer is formed by aligning a discotic compound (or a rod-like liquid crystal compound) and fixing the alignment state. Discotic compounds generally have a large birefringence. In addition, the discotic compound has various orientation forms. Therefore, by using a discotic compound, an optical compensatory sheet having optical properties that cannot be obtained by a conventional stretched birefringent film can be produced. An optical compensation sheet using a discotic compound is disclosed in JP-A-6-214116, US Pat.
Nos. 679, 5646703 and West German Patent Publication 3911
No. 620A1.

In the TN mode liquid crystal cell, the rod-like liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and further twist-aligned at 60 to 120 °. TN mode liquid crystal cells are most frequently used as color TFT liquid crystal display devices, and are described in many documents.

[0060]

EXAMPLES (Measurement of Optical Properties) The prepared cellulose acetate film (optical compensation sheet) was measured using an ellipsometer (M-150, manufactured by JASCO Corporation).
The Re retardation value and the Rth retardation value at a wavelength of 550 nm were measured. (Scratch strength) The scratch strength was measured under conditions of temperature and humidity of 25 ° C and 60% RH. Of these, those that can withstand practical use have a scratching strength exceeding 1 g.

Example 1 The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution. The solution was filtered using a filter paper (No. 63, manufactured by Advantech) having a retention particle size of 4 μm and a drainage time of 35 seconds at 5 kg / cm ² or less.

<< Composition of Cellulose Acetate Solution >>セ ル ロ ー ス Cellulose acetate having a degree of acetylation of 60.9% (degree of polymerization: 300, Mn / Mw = 1. 5) 100 parts by mass triphenyl phosphate (plasticizer) 7.8 parts by mass biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass methylene chloride (first solvent) 300 parts by mass methanol (second solvent) 54 parts by mass 1- Butanol (third solvent) 11 parts by mass ────────────────────────────────────

To another mixing tank, 16 parts by mass of the following retardation increasing agent, 0.28 parts by mass of silicon dioxide fine particles (average particle size: 0.1 μm), 80 parts by mass of methylene chloride, and 20 parts by mass of methanol were charged. The mixture was stirred while heating to prepare a retardation increasing agent solution (and a fine particle dispersion). 25 parts by mass of the retardation increasing agent solution was mixed with 474 parts by mass of the cellulose acetate solution, and the mixture was sufficiently stirred to prepare a dope. The addition amount of the retardation increasing agent is cellulose acetate 1
With respect to 00 parts by mass, 3.5 parts by mass and the amount of added fine particles was also 0.0175 parts by mass.

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The obtained dope was cast using a band casting machine. A film having a residual solvent amount of 15% by mass
The film was laterally stretched at a stretching ratio of 25% using a tenter under the condition of 0 ° C., held at 50 ° C. for 30 seconds while maintaining the stretched width, and then the clip was removed to prepare a cellulose acetate film. The residual solvent amount at the end of the stretching was 5% by mass, and the film was further dried to make the residual solvent amount less than 0.1% by mass to prepare a film.

1) Coating of Back First Layer (Transparent Conductive Film) The following formulation was applied on one side of the obtained film so that the dry film thickness became 0.2 μm, and dried at 115 ° C. for 30 seconds. . In addition, the following mass parts show solid content mass.

組成 Transparent conductive film coating liquid composition ─────分散 Conductive fine particle dispersion (SnO ₂ / Sb ₂ O ₃ , 0.05 μm) 7 Parts by mass Polyoxyethylene sorbitan monolaurate (number of oxyethylenes: 20) 0.3 parts by mass Water 89 parts by mass Gelatin 1 part by mass Sorbitol / polyglycidyl ether 1 part by mass ──────────── ────────────────────────

The thickness of the film (optical compensation sheet) thus obtained was 80 μm. The haze was 1.2%. The coefficient of kinetic friction of the film on the side opposite to the transparent conductive film was 0.38. Prepared cellulose acetate film (optical compensation sheet) X-1
, The Re retardation value and the Rth retardation value at a wavelength of 550 nm were measured using an ellipsometer (M-150, manufactured by JASCO Corporation), and the surface of the film opposite to the transparent conductive film was scratched. When the strength was measured, Re = 40 nm and Rth = 13.
0 nm and a scratch strength of 1.5 g. The surface resistivity of the film on the transparent conductive film side was 0.6 × 10 ¹² Ω / □. A solution was prepared in the same manner as in Example 1 except that 50% by mass of the film prepared in Example 1 was used as a film raw material, and each component contained in the film was reduced by the amount of the mass. The obtained Re retardation value and Rth retardation value, scratching strength, and surface resistivity were the same as those in Example 1.

Example 2 Cellulose Acetate Solution 4
A dope was prepared by mixing 56 parts by mass of a retardation increasing agent solution with 74 parts by mass of a dope (cellulose acetate 100).
Cellulose acetate film (having a transparent conductive film) in the same manner as in Example 1 except that 7.8 parts by mass of a retardation increasing agent was used with respect to parts by mass and the stretching ratio was changed to 14%. Compensation sheet). The haze of the produced optical compensatory sheet was 1.2%, and the coefficient of kinetic friction on the surface of the film opposite to the transparent conductive film was 0.1%.
38. The optical characteristics of the produced cellulose acetate film (optical compensation sheet) X-2 were measured, and the scratch strength of the film on the side opposite to the transparent conductive film was measured. As a result, Re = 50 nm and Rth = 24.
0 nm and a scratch strength of 1.7 g. The surface resistivity of the film on the transparent conductive film side was 0.7 × 10 ¹² Ω / □.

Example 3 A cellulose acetate film was produced in the same manner as in Example 2, except that the transparent conductive film was not applied and the stretching ratio was changed to 8%. On one surface of the cellulose acetate film, a transparent conductive film (gelatin undercoat layer) was applied in the same manner as in Example 1. Further, 7 cc of a coating solution having the following composition is coated on the gelatin undercoat layer.
/ M ^{2 and} dried. Thus, a transparent conductive film was applied to the film.

<< Composition of anionic copolymer coating solution >> ───────────────────────────────── The following anionic copolymer 0.079 parts by mass monoethyl citrate 1.01 parts by mass Acetone 20 parts by mass Methanol 87.7 parts by mass Water 4.05 parts by mass ───────────────────────────── ───────

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The thickness of the thus obtained film X-3 was 80 μm. The haze was 1.7%, and the coefficient of kinetic friction on the surface of the film opposite to the transparent conductive film was 0.37. The surface resistivity of the film on the transparent conductive film side was 0.8 × 10 ¹² Ω / □. The optical properties of the produced cellulose acetate film (optical compensation sheet) were measured, and the scratch strength of the surface opposite to the transparent conductive film was measured.
th = 220 nm, and the scratch strength was 1.6 g. A coating solution having the following composition was applied to the surface of the cellulose acetate film opposite to the transparent conductive film at a rate of 28 ml / m ² using a # 16 wire bar coater. 60 ° C with warm air
And dried with warm air of 90 ° C. for 150 seconds. Next, the slow axis (wavelength 632.8) of the cellulose acetate film was used.
Rubbing treatment was performed on the formed film in the direction of 45 °.

<< Composition of Alignment Film Coating Solution >>変 性 The following modified polyvinyl alcohol 10 parts by mass Water 371 parts by mass Methanol 119 parts by mass Glutaraldehyde (crosslinked Agent) 0.5 parts by mass ────────────────────────────────────

[0075]

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(Formation of Optically Anisotropic Layer) On the alignment film, the following discotic (discotic) liquid crystalline compound 41.01 was formed.
g, ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.)
4.06 g, cellulose acetate butyrate (CAB)
551-0.2, manufactured by Eastman Chemical Company) 0.90
g, cellulose acetate butyrate (CAB531-
1. Eastman Chemical Co., Ltd.) 0.23 g, photopolymerization initiator (Irgacure 907, Ciba-Geigy).
A coating solution prepared by dissolving 35 g of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) in 102 g of methyl ethyl ketone was applied using a # 3 wire bar. This was attached to a metal frame and heated in a thermostat at 130 ° C. for 2 minutes to orient the discotic compound. Then, 1
Using a 120 W / cm high pressure mercury lamp at 30 ° C. for 1 minute
V irradiation was performed to polymerize the discotic compound. Then, it was left to cool to room temperature. Thus, an optically anisotropic layer was formed.
This optical compensation sheet is designated as X-6. The Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm is 38.
nm. The angle (tilt angle) between the disk surface and the first transparent support surface was 40 ° on average.

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Comparative Example 1 A cellulose acetate film (optical compensation sheet) Y-1 was produced in the same manner as in Example 1, except that the cellulose acetate solution was used as a dope as it was and the stretching treatment was not carried out. No fine particles were added. The evaluation results are shown in Table 1.

[Evaluation of Optical Compensation Sheet]
Table 1 shows the evaluation results of the optical compensation sheet produced in Comparative Example 1.

[0080]

[Table 1] Table 1 剤 Film retardation increasing agent Stretching ratio 2. Re Rth scratching strength X-1 (Example 1) 5 parts by mass 25% 40 nm 130 nm 1.5 g X-2 (Example 2) 7.8 parts by mass 14% 50 nm 240 nm 1.7 g X-3 (Example 3) 7.8 parts by mass 8% 20 nm 220 nm 1.6 g Y-1 (Comparative Example 1) None No stretching 4 nm 48 nm 0.8 g───────────────────────────────── ───

Example 4 A polarizing film was prepared by adsorbing iodine on a stretched polyvinyl alcohol film, and the cellulose triacetate film X-1 prepared in Example 1 was applied to the polarizing film using a polyvinyl alcohol-based adhesive. Pasted on one side. A commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to a saponification treatment, and affixed to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the cellulose acetate film produced in Example 1 were arranged in parallel. The transmission axis of the polarizing film and the slow axis of the commercially available cellulose triacetate film were arranged so as to be orthogonal to each other. Thus, a polarizing plate was produced.

Example 5 Example 4 was repeated except that the cellulose acetate film X-2 produced in Example 2 was used.
In the same manner as described above, a polarizing plate was produced.

Example 6 A polarizing film was produced by adsorbing iodine on a stretched polyvinyl alcohol film, and the cellulose triacetate film X with an optically anisotropic layer produced in Example 3 was produced using a polyvinyl alcohol-based adhesive. -6 was attached to one side of the polarizing film. At this time, the optically anisotropic layer was arranged so as to be on the side opposite to the polarizing film. Commercially available cellulose triacetate film (Fujitack TD
80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to a saponification treatment, and was attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the cellulose acetate film X-3 produced in Example 3 were arranged in parallel. The transmission axis of the polarizing film and the slow axis of the commercially available cellulose triacetate film were arranged so as to be orthogonal to each other. Thus, a polarizing plate was produced.

[Embodiment 7] A liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.) using a vertical alignment type liquid crystal cell.
Peel a pair of polarizing plates and a pair of optical compensation sheets provided in the, instead of the polarizing plate produced in Example 4,
Cellulose acetate film X- produced in Example 1
One was attached to the observer side and one to the backlight side via an adhesive so that 1 was on the liquid crystal cell side. The crossed Nicols arrangement was such that the transmission axis of the polarizing plate on the viewer side was in the vertical direction, and the transmission axis of the polarizing plate on the backlight side was in the horizontal direction. The viewing angle of the prepared liquid crystal display device was measured in eight stages from black display (L1) to white display (L8) using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 2.

Example 8 A liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.) using a vertical alignment type liquid crystal cell.
Peel a pair of polarizing plates and a pair of optical compensation sheets provided in the, instead of the polarizing plate produced in Example 5,
Cellulose acetate film X- produced in Example 2
One sheet was adhered to the viewer side via an adhesive so that 2 was on the liquid crystal cell side. One commercially available polarizing plate (HLC2-5618HCS, manufactured by Sanritz Co., Ltd.) was attached to the backlight side. The crossed Nicols arrangement was such that the transmission axis of the polarizing plate on the viewer side was in the vertical direction, and the transmission axis of the polarizing plate on the backlight side was in the horizontal direction. About the manufactured liquid crystal display device, a measuring machine (EZ-Contrast 1)
(D, 60D, manufactured by ELDIM), the viewing angle was measured in eight steps from black display (L1) to white display (L8). The results are shown in Table 2.

[Comparative Example 2] A liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.) using a vertical alignment type liquid crystal cell.
About the measuring machine (EZ-Contrast 160D, ELDI
(M company), from black display (L1) to white display (L8)
The viewing angle was measured in eight steps up to. The results are shown in Table 2.

[0087]

[Table 2] Table 2 液晶 Liquid crystal viewing angle (contrast ratio Range of 10 or more and no black-side gradation inversion) Display device Direction of transmission axis 45 ° from transmission axis ───────────────────────── ─────────── Example 7> 80 ゜> 80 ゜ Example 8> 80 ゜> 80 ゜ Comparative Example 2> 80 ゜ 44 ゜─────────────────────── (Note) Inversion of black side: Inversion between L1 and L2

Example 9 (Preparation of Bend Alignment Liquid Crystal Cell) A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and the alignment film was subjected to a rubbing treatment. The two glass substrates thus obtained were opposed to each other in an arrangement in which the rubbing directions were parallel, and the cell gap was set to 6 μm. Δn is 0.13 in the cell gap
96 liquid crystal compounds (ZLI1132, manufactured by Merck Ltd.) were injected to prepare bend alignment liquid crystal cells. Two elliptically polarizing plates produced in Example 6 were attached so as to sandwich the produced bend alignment cell. The optically anisotropic layer of the elliptically polarizing plate was arranged so as to face the cell substrate, and the rubbing direction of the liquid crystal cell was antiparallel to the rubbing direction of the optically anisotropic layer facing the cell substrate. A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally white mode of 2 V for white display and 5 V for black display was set. The transmittance ratio (white display / black display) is defined as a contrast ratio, and a measuring device (EZ-Contrast 160D, ELD
IM display) from black display (L1) to white display (L
The viewing angle was measured in eight steps up to 8). The results are shown in Table 3.

[0089]

[Table 3] Table 3 液晶 Liquid crystal viewing angle (contrast ratio Range of 10 or more without black side gradation inversion) Display device Upper Lower Left / Right ──────────────────────────────── ──── Example 9 80 ゜ 80 ゜ 80 ゜ ──────────────────────────────────── ( Note) Black side tone inversion: Inversion between L1 and L2

[Example 10] 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 was peeled off, and the polarized light produced in Example 4 was used instead. The plates were adhered one by one to the observer side and the backlight side via an adhesive so that the cellulose acetate film X-1 produced in Example 1 was on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged to be orthogonal to each other.
About the manufactured liquid crystal display device, a measuring machine (EZ-Contra
st160D, manufactured by ELDIM) to display black (L
The viewing angle was measured in eight steps from 1) to white display (L8). The results are shown in Table 4.

Comparative Example 3 A liquid crystal display (6E-A3, manufactured by Sharp Corporation) using a TN type liquid crystal cell was displayed in black (L1) using a measuring machine (EZ-Contrast 160D, manufactured by ELDIM). ) To white display (L8) in eight steps. The results are shown in Table 4.

[0092]

[Table 4] Table 4 視野 Liquid crystal viewing angle (contrast ratio Range of 10 or more without black side gradation inversion) Display device Upper Lower Left / Right ──────────────────────────────── ──── Example 10 18 ゜ 23 ゜ 77 ゜ Comparative Example 3 15 ゜ 25 ゜ 37 ゜──────── (Note) Inversion of black side: Inversion between L1 and L2

Example 11 (Preparation of Optical Compensation Sheet) At room temperature, the average acetylation degree was 6
120 parts by mass of 0.9% cellulose acetate, 4 parts by mass of the retardation increasing agent of Example 1, 11.7 parts by mass of triphenyl phosphate, 5.85 parts by mass of biphenyldiphenyl phosphate, 538.2 methylene chloride
A solution (dope A) was prepared by mixing parts by mass and 46.8 parts by mass of methanol.

Similarly, 120 parts by mass of cellulose acetate having an average acetylation degree of 60.9%, 4 parts by mass of the retardation increasing agent of Example 1, 0.021 parts by mass of fine particles of Example 1, and triphenyl phosphate. 7 parts by mass, 5.85 parts by mass of biphenyl diphenyl phosphate, 2.0 parts by mass of tribenzylamine, methylene chloride 538.
A solution (dope B) was prepared by mixing 2 parts by mass and 46.8 parts by mass of methanol. Each of the obtained dopes was co-cast with a dope A as an inner layer (polymer layer) and a dope B as an outer layer (surface layer) on a stainless steel band with an internal merging die, and outer layers were provided on both surfaces of the inner layer. The film was dried until self-supporting and then stripped from the band. The residual volatile matter at that time was 30% by mass. Thereafter, the film was stretched at 130 ° C. in a direction perpendicular to the casting direction. After stretching, the film was dried at 120 ° C. for 30 minutes as it was, and the stretched film was taken out. The residual solvent amount after stretching was 0.1% by mass. On the cellulose acetate film thus obtained, a coating solution having the following composition was applied at 28 cc / m ^{2 and} dried.
A 0.1 μm gelatin layer was applied.

{Composition of Gelatin Layer Coating Solution} ────────────────────────────── Gelatin 0.542 parts by mass Formaldehyde 0.136 parts by mass Salicylic acid 0.160 parts by mass Acetone 39 .1 part by mass Methanol 15.8 parts by mass Methylene chloride 40.6 parts by mass Water 1.2 parts by mass ─────────────────────────── ─────────

Further, 7 cc / m ^{2 of} the anionic copolymer coating solution used in Example 3 was applied and dried. Thus, a transparent conductive film was applied to the film. Further, a coating solution having the following composition was applied to the layer on the opposite side to the above and dried at 25 cc / m ² to form a back layer. ──────────────────────────────────── Back layer coating solution composition ─────────セ ル ロ ー ス Cellulose diacetate (acetylation degree 55%) 0.656 parts by mass Silica matting agent (average particle size 1μ) 0.065 parts by mass Acetone 67.9 parts by mass Methanol 10.4 parts by mass ─────────────────────────────── ─────

The total thickness of the obtained film (optical compensation sheet) is 80 μm, the thickness of the inner layer is 70 μm,
The thickness of each of the outer layers was 5 μm. The optical properties were measured, and the scratch strength and the like of the surface of the film opposite to the transparent conductive film were measured.
th = 120 nm, and the scratching strength was 1.9 g. The haze of the obtained film was 1.9%, and the coefficient of kinetic friction on the surface of the film opposite to the transparent conductive film was 0.3.
It was 4. The surface resistivity of the film on the transparent conductive film side was 0.5 × 10 ¹² Ω / □. A polarizing plate and a liquid crystal display device were produced in the same manner as in Examples 4 and 8, except that the obtained film was used as an optical compensation sheet. . Further, when producing the liquid crystal display devices produced in Examples 7 to 11, generation of scratches and generation and adhesion of dust were prevented. In addition, there was no defect derived from dust visually observable on the display screen of the manufactured liquid crystal display device.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/3492 C08K 5/3492 5G435 C08L 1/12 C08L 1/12 G02F 1/1335 510 G02F 1/1335 510 1/13363 1/13363 G09F 9/00 302 G09F 9/00 302 // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 F term (reference) 2H049 BA02 BA06 BA25 BA42 BB03 BB33 BB49 BC03 BC09 BC22 2H091 FA08X FA08Z FA11X FB02 KA10 LA02 LA07 LA12 4F071 AA09 AB01 AC12 AC19 AD02 AE11 AF25 AF25Y AF28 AF28Y AF30 AF30Y AF35 AF35Y AH16 BA02 BB02 BB07 BC01 4F205 AA01 AB11 AC05 AE03 AG01 GB03 DE07GC07 GE07 GB07 DE07 DJ017 DJ037 DJ047 EU186 FA087 FB097 FD020 FD030 FD177 FD206 GP00 5G435 AA08 BB12 FF01 FF05 HH02 HH 12 KK07

Claims (13)

[Claims] 1. An in-plane retardation value of 20 to 7
An optical film comprising a polymer film in a range of 0 nm and a retardation value in a thickness direction of 70 to 400 nm, wherein at least one surface of the polymer film has a scratching strength of 1 g or more. Compensation sheet. 2. The optical compensatory sheet according to claim 1, wherein the dynamic friction coefficient of the surface of the polymer film is 0.40 or less. 3. A transparent conductive layer having a surface resistivity of 10 ¹² Ω / □ or less is provided on at least one surface of the polymer film, and the polymer film having the transparent conductive layer has a haze of 2.0% or less. The optical compensatory sheet according to claim 1, wherein the optical compensatory sheet is provided. 4. The polymer film has an acetylation degree of 57.0.
The optical compensatory sheet according to any one of claims 1 to 3, wherein the optical compensatory sheet is made of cellulose acetate in the range of 1 to 61.5%. 5. The method according to claim 4, wherein the aromatic compound having at least two aromatic rings is contained in an amount of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acetate. Optical compensation sheet. 6. The optical compensation sheet according to claim 4, wherein the polymer film is a stretched product stretched at a magnification of 3 to 100%. 7. The method of claim 1, wherein the aromatic compound comprises at least one 1,
The optical compensation sheet according to claim 5, having a 3,5-triazine ring. 8. An in-plane retardation value of 20 to 7
A method for producing an optical compensatory sheet comprising a polymer film having a retardation value in the range of 70 to 400 nm in a range of 0 nm and a thickness direction of 70 to 400 nm, wherein one surface of the polymer film has a scratch strength of 1 g or more. By forming the polymer film into a film by co-casting or sequential casting, the polymer film is formed on the polymer layer of the polymer and at least one surface thereof with the polymer having an average particle diameter of 1.0 μm or less. The surface of the polymer film on the side where the surface layer is provided has a scratch strength of 1 g.
A method for producing an optical compensation sheet as described above. 9. The polymer layer having an average particle size of 1.
The method for producing an optical compensation sheet according to claim 8, wherein fine particles having a particle size of 0 µm or less are added, and the amount of the fine particles added to the polymer in the surface layer is larger than the amount of the fine particles added to the polymer in the polymer layer. 10. A polarizing plate comprising a polarizing film and two transparent protective films disposed on both sides of the polarizing film, wherein one of the transparent protective films according to any one of claims 1 to 7. A polarizing plate, which is an optical compensatory sheet, wherein the slow axis of the optical compensatory sheet and the transmission axis of the polarizing film are arranged substantially in parallel. 11. A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein a liquid crystal cell and at least one polarizing plate are provided between the liquid crystal cell and at least one of the polarizing plates. A liquid crystal, wherein the optical compensation sheet according to any one of the above items is arranged, and further, the liquid crystal is arranged so that the slow axis of the optical compensation sheet and the transmission axis of the polarizing film are substantially parallel to each other. Display device. 12. A liquid crystal display device comprising a liquid crystal cell and two polarizing plates arranged on both sides of the liquid crystal cell, wherein at least one of the polarizing plates is the polarizing plate according to claim 10. 13. The liquid crystal display device according to claim 11, wherein the liquid crystal cell is an OCB mode, VA mode, or TN mode liquid crystal cell.