JP2002303722A - Optical compensation sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optically compensate a liquid crystal cell by combining an optically anisotropic layer composed of a liquid crystalline polymer and an optically anisotropic transparent supporting body. SOLUTION: In an optical compensation sheet having the optically anisotropic layer composed of the liquid crystalline polymer and the transparent supporting body composed of a cellulose acetate film, the liquid crystalline polymer is nematic-aligned or twisted-nematic-aligned in a glassy state and the cellulose acetate film with 0-20 nm Re retardation value and 30-70 nm Rth retardation value is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical compensatory sheet having an optically anisotropic layer comprising a liquid crystalline polymer and a transparent support comprising a cellulose acetate film.
Furthermore, the present invention relates to a method for producing an optical compensation sheet in which an optically anisotropic layer comprising a liquid crystalline polymer is provided on a cellulose acetate film.

[0002]

2. Description of the Related Art An optically anisotropic layer comprising a liquid crystalline polymer;
An optical compensation sheet (compensation plate for a liquid crystal display element) having a transparent support (transparent substrate) made of a plastic film having optical transparency and optical isotropy is disclosed in Japanese Patent No. 266060.
No. 1 and Japanese Patent No. 2743117. Further, in each publication, as a polymer constituting a plastic film, polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, polyphenylene sulfide, polyarylate, amorphous polyolefin, triacetyl cellulose, epoxy resin, or the like is used. (Polymethyl methacrylate, polycarbonate, polyether sulfone, polyarylate, and amorphous polyolefin are preferred).

Japanese Patent Application Laid-Open No. 8-278491 points out the problem of the optical compensatory sheet described in each of the above-mentioned publications in the durability of a transparent support made of a plastic film. It also points out that the optical function of the optically anisotropic layer made of a liquid crystalline polymer is deteriorated by mounting the transparent support. The invention described in Japanese Patent Application Laid-Open No. 8-278491 is composed of a liquid crystalline polymer without a plastic film in order to solve the problem of the durability of the transparent support and the problem of the deterioration of the optical function of the optically anisotropic layer. It is proposed to use only film-like layers.

[0004]

Problems to be Solved by the Invention Patent No. 2660601
No. 2,743,117 describe that polymethyl methacrylate, polycarbonate, polyether sulfone, polyarylate, and amorphous polyolefin are preferable as the polymer constituting the transparent support. When the present inventor conducted research,
Cellulose acetate film has excellent durability and optical properties, and when cellulose acetate film is used as a transparent support, the problem of durability and the problem of a decrease in the optical function of the optically anisotropic layer are reduced. Can be solved.

[0005] The present inventor has further studied and found that the patent No. 2
Using a transparent support having a certain optical anisotropy, instead of a transparent support having an optical isotropy described in 660601 and Japanese Patent No. 2743117,
An attempt was made to optically compensate a liquid crystal cell by combining an optically anisotropic layer composed of a liquid crystalline polymer and an optically anisotropic transparent support. An object of the present invention is to provide an optical compensation sheet comprising a combination of an optically anisotropic layer made of a liquid crystalline polymer and an optically anisotropic transparent support.

[0006]

An object of the present invention is to provide an optical compensatory sheet of the following (1) to (7) and the following (8):
This has been achieved by the method for producing an optical compensation sheet of (9). (1) An optical compensation sheet having an optically anisotropic layer made of a liquid crystalline polymer and a transparent support made of a cellulose acetate film, wherein the liquid crystalline polymer is in a nematic orientation or twisted nematic orientation in a glassy state. An optical compensation sheet, wherein the cellulose acetate film has a Re retardation value of 0 to 20 nm and an Rth retardation value of 30 to 70 nm.

(2) The cellulose acetate film is
The optical compensatory sheet according to (1), having a thickness of 10 to 70 μm. (3) The optical compensation sheet according to (1) or (2), wherein the cellulose acetate film comprises cellulose acetate having an acetylation degree of 59.0 to 61.5%. (4) The cellulose acetate film according to any one of (1) to (3), which contains 0.01 to 20 parts by mass of an aromatic compound having at least two aromatic rings based on 100 parts by mass of cellulose acetate. The optical compensation sheet according to the above.

(5) The aromatic compound is a compound having at least one 1,3,5-triazine ring.
4. The optical compensation sheet according to item 1. (6) The optical compensation sheet according to any one of (1) to (5), wherein the cellulose acetate film is a film manufactured by a co-casting method. (7) The cellulose acetate film has 2 carbon atoms.
A film prepared from a cellulose acetate solution in which cellulose acetate is dissolved in a solvent selected from the group consisting of ethers having 1 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 2 to 12 carbon atoms. The optical compensation sheet according to any one of (1) to (6).

(8) A step of applying a liquid crystalline polymer which becomes a glassy state at a temperature lower than the liquid crystal transition temperature on the alignment film; heating the liquid crystal polymer to a temperature higher than the liquid crystal transition temperature to convert the liquid crystal polymer into a nematic. A step of aligning or twisting nematic alignment; a step of maintaining the alignment of the liquid crystalline polymer and cooling it until it changes to a glass state, thereby forming an optically anisotropic layer made of the liquid crystalline polymer; A method for producing an optically compensatory sheet, comprising the steps of: peeling an active layer from an alignment film and transferring it onto a cellulose acetate film having a Re retardation value of 0 to 20 nm and an Rth retardation value of 30 to 70 nm. (9) The cellulose acetate film has an adhesive layer, the optically anisotropic layer is adhered to the adhesive layer, and the optically anisotropic layer is transferred onto the cellulose acetate film by peeling off the alignment film ( The method for producing an optical compensation sheet according to 8).

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

[0011]

The present inventor has an optical anisotropy suitable for optically compensating a liquid crystal cell in cooperation with an optically anisotropic layer composed of a liquid crystalline polymer, and has properties as a support. (For example, durability) It succeeded in producing the cellulose acetate film which was also excellent. When used in combination with an optically anisotropic layer composed of a liquid crystalline polymer, the frontal retardation of the optically anisotropic transparent support is desirably as small as possible (0 to 20 nm). Requires a constant value (30 to 70 nm). The above optical anisotropy is achieved without impairing the excellent physical properties as a support of the cellulose acetate film by means such as the use of additives (retardation increasing agents) and adjustment of production conditions (stretching method). be able to. The optical compensatory sheet of the present invention has a STN (Super Twist) because the optically anisotropic layer composed of a liquid crystalline polymer and the optically anisotropic transparent support cooperate to optically compensate the liquid crystal cell.
Nematic) type, TN (Twisted Nematic) type, VA (vert
ical alignment) type or OCB (optical comp
It can be advantageously used for various liquid crystal display devices such as an ensate bend type.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION [Liquid Crystal Polymer]
It is preferably a thermotropic liquid crystalline polymer having a liquid crystal transition temperature. The liquid crystal phase has a nematic alignment or a twisted nematic alignment. In the case of nematic orientation,
It is desirable to show uniform and monodomain orientation. Further, it is preferable that the liquid crystalline polymer be in a glassy state at a temperature lower than the liquid crystal transition temperature. In a liquid crystalline polymer that becomes a crystalline phase at a temperature lower than the liquid crystal transition temperature, it is difficult to maintain an alignment state (nematic alignment or twisted nematic alignment) when cooled to a temperature lower than the liquid crystal transition temperature. If it is in a glassy state, nematic orientation or twisted nematic orientation can be easily maintained even after cooling.

The liquid crystalline polymer is classified into a polymer having a main chain having liquid crystallinity (main chain type liquid crystal polymer) and a polymer having a side chain having liquid crystallinity (side chain type liquid crystal polymer). Representative examples of the main chain type liquid crystal polymer include polyester, polycarbonate, polyamide, polyimide, and a copolymer thereof (eg, polyesterimide). As the side chain type liquid crystal polymer, polyacrylate, polymethacrylate, polymalonate and polysiloxane are typical. The main chain type liquid crystal polymer is more preferable than the side chain type liquid crystal polymer. Polyesters are particularly preferred.

[0014] Polyesters are generally synthesized by the reaction of a polyol with a polycarboxylic acid. Since the main chain type liquid crystal polymer generally has a linear molecular structure, the polyester used as the main chain type liquid crystal polymer is generally synthesized by a reaction between a diol and a dicarboxylic acid.
That is, the polyester used as the main chain type liquid crystal polymer generally has a repeating unit derived from a diol (A below).
And a repeating unit derived from dicarboxylic acid (B below) is alternately repeated. In addition, polyester
It may be composed of a repeating unit derived from hydroxycarboxylic acid (C1 or C2 below). (A) -O-LO- (B) -CO-L-CO- (C1) -CO-LO-, (C2) -OL-CO- The above (A), (B), In (C1) and (C2), L
Is a divalent aliphatic group, a divalent aromatic group, -O-, -CH
= N-, -N = N- and combinations thereof.
Note that -N = N- may be coordinated with an oxygen atom.

The divalent aliphatic group includes an alkylene group, a substituted alkylene group, an alkenylene group, a substituted alkenylene group, an alkynylene group and a substituted alkynylene group. The divalent aliphatic group preferably has 1 to 20 carbon atoms, more preferably 2 to 12 carbon atoms. The divalent aliphatic group may have a cyclic structure or a branch. Examples of the alkylene group include dimethylmethylene, ethylene, propylene, butylene, 2-methylbutylene, pentylene, hexylene, 1,4-cyclohexylene,
Methylhexylene, heptylene, octylene, 1,4-
Cyclooctylene, 1,5-cyclooctylene, nonylene, decylene, undecylene, dodecylene and 5,6
-Perhydro-4,7-methanoindenylene. Examples of alkenylene groups include vinylene.

The divalent aromatic group includes an arylene group and a substituted arylene group. The arylene group is preferably phenylene or naphthylene, and 1,2-phenylene, 1,
4-phenylene, 1,3-naphthylene, 1,4-naphthylene, 2,3-naphthylene and 2,6-naphthylene are more preferred, and 1,2-phenylene and 1,4-phenylene are most preferred. It is particularly preferable that the polyester contains 1,2-phenylene (or substituted 1,2-phenylene) in the repeating unit. The arylene part of the substituted arylene group is the same as the above-mentioned arylene group. Examples of the substituent of the substituted arylene group include a halogen atom (F,
Cl, Br), an alkyl group having 1 to 4 carbon atoms, a halogen-substituted alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and phenyl.

In the following, examples of L as a combination will be described. AL is a divalent aliphatic group, and AR is a divalent aromatic group. L1: -AR-AR- L2: -AR-AL-AR- L3: -AR-O-AR- L4: -AR-CH = N-AR- L5: -AR-AR-AR- L6: -AR- N = N-AR-

The molar ratio of dicarboxylic acid to diol is generally 1: 1. When hydroxycarboxylic acid is used, the molar ratio between carboxylic acid groups and hydroxyl groups is generally 1: 1. The polyester preferably has 5 to 40 mol%, and more preferably 10 to 35 mol%, of a repeating unit containing 1,2-phenylene (or substituted 1,2-phenylene).

The molecular weight of the liquid crystalline polymer is such that its logarithmic viscosity is 0.1.
It is preferably adjusted to be from 0.05 to 3.00, more preferably from 0.07 to 2.00. The logarithmic viscosity is a value obtained by dissolving a liquid crystalline polymer in a phenol / tetrachloroethane (mass ratio 60/40) mixed solvent and measuring at 30 ° C. The glass transition temperature of the liquid crystalline polymer is preferably 0 ° C. or higher,
More preferably, the temperature is 20 ° C. or higher.

The liquid crystalline polymer is prepared by a known polymer synthesis method,
For example, it can be synthesized according to an acid chloride method, a melt polymerization method or a solution polymerization method. In the synthesis of polyester by the acid chloride method, an acid chloride of dicarboxylic acid is used. In the melt polymerization method, it can be produced by polymerizing an acetylated product of a diol corresponding to a dicarboxylic acid at a high temperature under a high vacuum. In the solution polymerization method, a dicarboxylic acid dichloride and a diol are dissolved in a solvent and an acid acceptor (eg, pyridine) is dissolved.
By heating in the presence of a polyester, a polyester can be synthesized. The molecular weight of the liquid crystalline polymer can be easily adjusted by adjusting the polymerization time or the charge composition. A metal salt (eg, sodium acetate) may be added to accelerate the polymerization reaction.

In order to twist the liquid crystal polymer in a twisted nematic orientation, an optically active compound is generally used in addition to the liquid crystal polymer. In principle, any compound having an optically active asymmetric carbon atom can be used as an optically active compound. However, from the viewpoint of compatibility with the liquid crystalline polymer, it is preferable to use an optically active liquid crystalline compound.
Rod-like liquid crystalline compounds having a relatively low molecular weight and containing at least one asymmetric carbon atom are particularly preferred.

Further, an optically active liquid crystalline polymer having an asymmetric carbon atom introduced into the molecular structure of the liquid crystalline polymer may be used alone or in combination with an optically inactive liquid crystalline polymer. When an asymmetric carbon atom is introduced into the molecular structure of the liquid crystalline polymer described above, the divalent aliphatic group (AL) preferably contains an asymmetric carbon atom, and the alkylene group or the substituted alkylene group has an asymmetric carbon atom. More preferably,
Examples of (substituted) alkylene groups containing asymmetric carbon atoms include 1
-Methylethylene, 1-methylpropylene, 1-methylbutylene, 2-methylbutylene, 2-chlorobutylene,
2-trifluoromethylbutylene, 2,3-dimethylbutylene, 2-methylpentylene, 3-methylhexylene, and 3-chlorohexylene are included. An alkyl group or an alkoxy group as a substituent of the substituted arylene group may contain an asymmetric carbon atom. Examples of the alkyl group containing an asymmetric carbon atom include 2-methylbutyl. Examples of alkoxy groups containing an asymmetric carbon atom include 2-methylbutoxy and 1-methylheptyloxy.

The proportion of the optically active repeating unit in the liquid crystalline polymer is preferably 0.1 to 80 mol%, more preferably 0.5 to 60 mol%, and more preferably 1 to 50 mol%. %, More preferably 5%.
Most preferably, it is from about 30 mol% to about 30 mol%. The molecular weight of the optically active liquid crystalline polymer has a logarithmic viscosity of 0.05 to 5.
It is preferable to adjust so as to be 00. When the optically inactive liquid crystal polymer and the optically active compound are used in combination, the amount of the optically active compound is preferably in the range of 0.1 to 60% by mass of the liquid crystal polymer, and 0.5 to 40% by mass. % Is more preferable.

Specific examples of the liquid crystalline polymer are described in Japanese Patent Nos. 2660601, 2743117 and JP-A-8-278491.

[Retardation of Cellulose Acetate Film] The Re retardation value and the Rth retardation value 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 the 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 cellulose acetate film has a Re retardation value of 0 to 20 nm,
Then, the Rth retardation value is adjusted to 30 to 70 nm. Rth retardation value is 35-60n
m, more preferably 40 to 50 nm. The birefringence (Δn: nx−ny) of the cellulose acetate film is preferably 0.00 to 0.002. Further, the birefringence in the thickness direction of the cellulose acetate film ｛(nx + n
y) / 2-nz} is preferably 0.001 to 0.04.

[Cellulose Acetate] The cellulose acetate preferably has an acetylation degree of 59.0 to 61.5%. The degree of acetylation means the amount of bound acetic acid per unit weight of cellulose. The degree of acetylation is ASTM: D-81
The measurement and calculation of the degree of acetylation in 7-91 (test method for cellulose acetate and the like) are performed. The viscosity average degree of polymerization (DP) of the cellulose ester is preferably 250 or more, more preferably 290 or more. Further, the cellulose ester used in the present invention has a Mw / M by gel permeation chromatography.
It is preferable that the molecular weight distribution of n (Mw is a weight average molecular weight, Mn is a number average molecular weight) is narrow. The specific value of Mw / Mn is preferably 1.0 to 1.7,
More preferably, it is 1.3 to 1.65.
Most preferably, it is 4 to 1.6.

[Retardation increasing agent] In order to adjust the retardation of the cellulose acetate film,
An aromatic compound having at least two aromatic rings can be used as a retardation increasing agent. The aromatic compound is preferably used in an amount of 0.01 to 20 parts by mass, more preferably 0.05 to 15 parts by mass, based on 100 parts by mass of cellulose acetate. Most preferably, it is used in the range of 10 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 six-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. Preferred are 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. 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
l, 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 connection relationships (a) to (c) may be combined. For example, a single bond of (b) connects two aromatic rings, and a connecting group of (c) also connects two aromatic rings, and an aliphatic ring or a non-aromatic ring is formed between the two aromatic rings. May form a heterocyclic ring. The molecular weight of the retardation increasing agent is preferably from 300 to 800.

[Production of Cellulose Acetate 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 cellulose acetate is dissolved in an organic solvent. The organic solvent is
It may contain a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. preferable. Ethers, ketones and esters may have a cyclic structure. Functional groups of ether, ketone and ester (i.e., -O
-, -CO-, and -COO-) can also be used as the organic solvent.
The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any 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 types of functional groups include
Includes 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol. The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen atoms in halogenated hydrocarbons is preferably 25 to 75 mol%, and preferably 3 to 75 mol%.
The content is more preferably 0 to 70 mol%, still more preferably 35 to 65 mol%, and 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.

The components 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. Alternatively, 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. At the end of the stirring blade, a scraping blade is preferably provided to renew the liquid film on the container wall. 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 vessel 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 to adjust the amount of cellulose acetate so that the mixture contains 10 to 40% by mass. 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 heated 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 the cooling is started and the final cooling temperature by the time from when the cooling is started to when the final cooling temperature is reached.

Further, this is heated 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 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 the heating is started until 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 and dissolving method, it is desirable to use a closed container in order to avoid water contamination due to dew 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 polymerization degree: 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 near 3 ° C., and below this temperature, the gel state becomes uniform. Therefore,
This solution must be maintained at a temperature equal to or higher than the pseudo phase transition temperature, preferably at a temperature of about 10 ° C. plus the gel phase transition temperature. However, the pseudo phase transition temperature varies depending on the acetylation degree of cellulose acetate, the viscosity average polymerization degree, the solution concentration, and the organic solvent used.

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 high-temperature air whose temperature is 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.

Using the prepared cellulose acetate solution (dope), two or more layers can be cast to form a film. In this case, it is preferable to produce a cellulose acetate film 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 10 to 40%. It is preferable that the surface of the drum or the band is finished in a mirror state.

When casting a plurality of cellulose acetate solutions of two or more layers, a plurality of cellulose acetate solutions can be cast, and a plurality of cellulose acetate solutions can be cast from a plurality of casting ports provided at intervals in the traveling direction of the support. A film may be produced while casting and laminating a solution containing cellulose acetate, respectively (Japanese Patent Application Laid-Open No. 61-158414, Japanese Patent Application Laid-Open No.
Nos. 122419 and 11-198285). Further, a cellulose acetate solution may be cast from two casting ports (Japanese Patent Publication Nos. 60-27562, JP-A-61-94724, JP-A-61-947245, and JP-A-61-947245).
Nos. 1-104813, 61-158413 and JP-A-6-134933. A cellulose acetate film casting method comprising wrapping a flow of a high-viscosity cellulose acetate solution with a low-viscosity cellulose acetate solution and simultaneously extruding the high- and low-viscosity cellulose acetate solution (described in JP-A-56-162617).
Can also be adopted.

Using two casting ports, the film formed on the support by the first casting port is peeled off, and the second casting is performed on the side in contact with the support surface, whereby the film is formed. (Described in JP-B-44-20235). The plurality of cellulose acetate solutions to be cast may have the same composition. In order to give a function to a plurality of cellulose acetate layers, a cellulose acetate solution according to the function can be extruded from each casting port. The cellulose acetate solution may be simultaneously cast with other functional layers (eg, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, and a polarizing layer).

In the conventional monolayer liquid, it is necessary to extrude a high-concentration and high-viscosity cellulose acetate solution in order to obtain a required film thickness. In this case, the stability of the cellulose acetate solution is poor, and In many cases, an object was generated, resulting in a bump failure or poor flatness, which was a problem in many cases. As a solution to this, by casting a plurality of cellulose acetate solutions from the casting port, a high-viscosity solution can be simultaneously extruded onto the support, and the flatness is improved and an excellent planar film can be produced. Not only
By using a concentrated cellulose acetate solution, a reduction in the drying load can be achieved, and the production speed of the film can be increased.

A plasticizer can be added to the cellulose acetate film in order to improve the 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 are 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 0.1 to 25 times the amount of the cellulose ester.
%, More preferably 1 to 20% by mass, most preferably 3 to 15% by mass.

The cellulose acetate film may contain a deterioration inhibitor (eg, an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, an amine). Regarding the deterioration inhibitor, see JP-A-3-19920.
No. 1, 5-1907073, 5-194789
And JP-A-5-271471 and JP-A-6-107854. The amount of the deterioration inhibitor 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 to the film surface. Particularly preferred examples of the deterioration inhibitor include butylated hydroxytoluene (BHT) and tribenzylamine (TBA). The thickness of the cellulose acetate film is preferably 10 to 70 μm, more preferably 20 to 60 μm, and more preferably 30 to 50 μm.
m is most preferred. The elastic modulus of the cellulose acetate film is preferably 3000 MPa or less, more preferably 2500 MPa or less.

[High Thermal Conductive Particles] The thermal conductivity of the cellulose acetate film is preferably 1 W / m · K or more. In order to improve the thermal conductivity of the cellulose acetate film, high thermal conductive particles can be added. The high thermal conductive particles can be formed from aluminum nitride, silicon nitride, boron nitride, magnesium nitride, silicon carbide, aluminum oxide, silicon oxide, zinc oxide, magnesium oxide, carbon (including diamond), or metal. The particles are preferably transparent so as not to impair the transparency of the film. The amount of the high thermal conductive particles is preferably in the range of 5 to 100 parts by mass, more preferably 5 to 50 parts by mass, per 100 parts by mass of cellulose acetate. The average particle size of the high thermal conductive particles is preferably 0.05 to 80 μm, and 0.1 to 10 μm
Is more preferred. The shape of the particles is generally spherical or acicular.

[Biaxial stretching] The cellulose acetate film is preferably stretched in order to reduce virtual distortion. By stretching, virtual distortion in the stretching direction can be reduced. To reduce distortion in all directions in the plane,
Biaxial stretching is more preferred. The biaxial stretching includes a simultaneous biaxial stretching method and a sequential biaxial stretching method. From the viewpoint of continuous production, a sequential biaxial stretching method is preferable. After casting the dope, the dope is peeled off from a band or a drum, and the width direction is removed. After stretching in the (longitudinal method), the film is stretched in the longitudinal direction (width direction). The method of stretching in the width direction is described in JP-A-62-15033.
No. 5, JP-A-4-152125, JP-A-4-284221
Nos. 4-298310 and 11-48271. The stretching of the film is performed at normal temperature or under heating conditions. The heating temperature is preferably equal to or lower than the glass transition temperature of the film. The film can be stretched during the drying process, and is particularly effective when the solvent remains. In the case of stretching in the longitudinal direction, for example, the film is stretched by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed. In the case of stretching in the width direction, the film can be stretched by conveying the film while holding it with a tenter and gradually increasing the width of the tenter. After drying the film, the film can be stretched using a stretching machine (preferably, uniaxial stretching using a long stretching machine). The stretching ratio of the film (ratio of increase by stretching to the original length) is preferably 5 to 50%, more preferably 10 to 40%, and most preferably 15 to 35%. .

The steps from casting to drying are generally performed in an air atmosphere, but may be performed in a relatively inert gas (eg, nitrogen gas) atmosphere. A general winding machine for cellulose acetate film can be used.
As a winding method, a constant tension method, a constant torque method, a taper tension method, or a program tension control method with constant internal stress can be adopted.

[Coefficient of hygroscopic expansion] The coefficient of hygroscopic swelling of the cellulose acetate film is 30 × 10 ⁻⁵ / cm ² /% RH.
And preferably 15 × 10 ⁻⁵ / cm ² /%
RH or less, more preferably 10 × 10 ⁻⁵ /
Most preferably, it is not more than cm ² /% RH. The hygroscopic expansion coefficient is the amount of change in the length of the sample when the relative humidity is changed at a constant temperature. Specifically, the prepared cellulose acetate film was 5 mm wide and 20 m long.
m, cut out at 25 ° C, 20
Hang under an atmosphere of% RH. A 0.5 g weight is hung on the other end and left for a certain period of time. Next, while keeping the temperature constant, the humidity is set to 80% RH, and the length deformation is measured. The measurement is performed for 10 samples of the same sample, and the average value is adopted.

The dimensional change due to moisture absorption may be achieved by reducing the free volume in the cellulose acetate film. What greatly affects the free volume is the amount of residual solvent during film formation,
The smaller the size, the smaller the dimensional change. A common approach to reduce residual solvent is to dry at high temperature and for a long time.
The amount of the residual solvent is preferably 0.01% by mass to 1% by mass, more preferably 0.02% by mass to 0.07% by mass, and most preferably 0.03% by mass to 0.05% by mass. By controlling the amount of residual solvent, a cellulose acetate film having a small coefficient of hygroscopic expansion can be produced. In order to reduce the dimensional change due to moisture absorption, a hydrophobic compound can be added to the cellulose acetate film. The hydrophobic group of the hydrophobic compound is preferably an alkyl group or phenyl. A hydrophobic compound may be used as a plasticizer or a deterioration inhibitor (described later). The amount of the hydrophobic compound added is
0.01 to 1 of cellulose acetate solution (dope)
It is preferably 0% by mass, more preferably 0.1 to 5% by mass, and most preferably 1 to 3% by mass.

[Surface Treatment of Cellulose Acetate Film] The cellulose acetate film is preferably subjected to a surface treatment. Specific methods include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. In addition, Japanese Patent Application Laid-Open
As described in JP-A-333433, it is also preferable to provide an undercoat layer. From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film is set to be equal to or lower than the glass transition temperature in these treatments.
The temperature is preferably set to 50 ° C. or lower. When the optical compensatory sheet and the polarizing plate are bonded and used, it is particularly preferable to perform an acid treatment or an alkali treatment, that is, a saponification treatment on cellulose acetate, from the viewpoint of adhesion to the polarizing film. The surface energy is preferably 55 mN / m or more, more preferably 60 mN / m or more and 75 mN / m or less. The surface energy of a solid is
"Basics and Application of Wetting" (Realize Inc. 1989.1)
2.10), the contact angle method, the wet heat method or the adsorption method (preferably the contact angle method). Specifically, two types of solutions whose surface energies are known are dropped on a cellulose acetate film, and at the intersection between the surface of the droplet and the film surface, the angle between the tangent drawn to the droplet and the film surface is determined. The angle containing the drop is defined as the contact angle,
The surface energy of the film can be calculated by the calculation.

An alkali saponification treatment is particularly preferred. The alkali saponification treatment is generally performed in a cycle in which a film is immersed in an alkaline solution, neutralized with an acidic solution, washed with water, and dried. As the alkaline solution, an aqueous solution of potassium hydroxide or an aqueous solution of sodium hydroxide is generally used. The prescribed concentration of potassium ion or sodium ion is preferably 0.1 N to 3.0 N, and 0.1 N to 3.0 N.
More preferably, it is 5N to 2.0N. The temperature of the alkaline aqueous solution is preferably in the range of room temperature to 90 ° C,
40 ° C to 70 ° C is more preferred.

[Alignment Film] The alignment film is generally provided on a support. A typical example of the alignment film is a rubbed polyimide film, a rubbed polyvinyl alcohol film, or an oblique deposition film of an inorganic substance (eg, silicon oxide). The support may be a metal (eg, aluminum, iron,
A (copper) plate or a glass plate is used. In addition, plastics whose surfaces are directly rubbed (eg, polyimide, polyamide imide, polyamide, polyether imide, polyether ketone, polyether ether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate) , Polybutylene terephthalate, polyacetal, polycarbonate, acrylic resin, polyvinyl alcohol, cellulosic plastic, epoxy resin, phenol resin) film can also be used as the alignment film. Plastic films made of highly crystalline polymers (eg, polyimide, polyetherimide, polyetherketone, polyetheretherketone, polyphenylene sulfide, polyethylene terephthalate) can be stretched uniaxially instead of rubbed. Is obtained.

Examples of the alignment film include a rubbed polyimide film provided on a support, a rubbed polyvinyl alcohol film provided on a support, a directly rubbed polyimide film, a directly rubbed polyethylene terephthalate film, and a direct rubbed film. Preferred are a treated polyphenylene sulfide film, a directly rubbed polyetheretherketone film, and a directly rubbed polyvinyl alcohol film.

[Adhesive] The optically anisotropic layer formed by orienting the liquid crystalline polymer is preferably transferred from the alignment film to a cellulose acetate film. In the transfer, it is preferable to use an adhesive. As the adhesive, a compound capable of adhering to both the optically anisotropic layer made of a liquid crystalline polymer and the cellulose acetate film is selected and used. The adhesive is desirably transparent and has optical isotropy. A photo-curing adhesive, an electron beam-curing adhesive or a thermosetting adhesive is preferable, and a photo-curing adhesive or an electron beam-curing adhesive containing an acrylic oligomer as a main component, and a light containing an epoxy resin as a main component. Curable adhesives or electron beam curable adhesives are particularly preferred. Since the liquid crystalline polymer is preferably in a glass state at a temperature lower than the liquid crystal transition temperature, as the adhesive, a photo-curable adhesive or an electron beam-curable adhesive is better than a thermosetting adhesive. Is also preferred.

The thickness of the adhesive layer made of the adhesive is 0.1
To 100 μm, preferably 1 to 30 μm
Is more preferable. An antioxidant or an ultraviolet absorber may be added to the adhesive layer in addition to the adhesive.

[Production of Optical Compensation Sheet] The optical compensation sheet is a step of applying a liquid crystalline polymer which becomes a glassy state at a temperature lower than the liquid crystal transition temperature on the alignment film; up to a temperature higher than the liquid crystal transition temperature. Heating and liquid crystal polymer in a nematic or twisted nematic orientation; maintaining the orientation of the liquid crystal polymer and cooling it to a glassy state, thereby forming an optically anisotropic layer composed of the liquid crystal polymer. Forming step; and peeling off the optically anisotropic layer from the alignment film and transferring the film onto a cellulose acetate film.

In the step of applying a liquid crystalline polymer on the alignment film, a liquid crystalline polymer solution or a liquid crystalline polymer in a molten state is used. It is preferable to use a liquid crystalline polymer solution.
Solvents for preparing the liquid crystalline polymer solution include halogenated hydrocarbons (eg, chloroform, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, orthodichlorobenzene), phenol, ketone, ether, amide (eg, dimethylformamide, Dimethylacetamide), sulfoxide (eg, dimethylsulfoxide), N-methylpyrrolidone, sulfolane, and hydrocarbon (eg, cyclohexane) can be used. Two or more solvents (for example, halogenated hydrocarbons and phenol) may be used as a mixture. The concentration of the solution is preferably 5 to 50% by mass, and 10 to 30% by mass.
Is more preferred. . The application of the liquid crystalline polymer solution is performed by a known coating method (eg, spin coating method, roll coating method,
(Gravure coating method, curtain coating method, slot coating method, immersion pulling method). When a solution of a liquid crystalline polymer is used, the solvent is removed by drying after application of the solution.

Next, the liquid crystalline polymer is heated to a temperature higher than the liquid crystal transition temperature for a certain period of time to form a uniform monodomain alignment (nematic alignment, twisted nematic alignment). In order to promote the alignment by the interface effect, it is preferable in principle to increase the alignment temperature to lower the viscosity of the liquid crystalline polymer. However, depending on the type of liquid crystalline polymer, the liquid crystalline polymer may have an isotropic phase at a higher temperature than the liquid crystal phase (nematic phase, twisted nematic phase).
Heating is performed at a temperature in a range where the liquid crystal phase is obtained. Heating temperature is 50
To 300 ° C., preferably 100 to 250 ° C.
It is more preferable that the temperature is ° C. The heating time is preferably from 10 seconds to 100 minutes, more preferably from 30 seconds to 60 minutes.

Next, the liquid crystal polymer is cooled until it changes to a glass state while maintaining the orientation of the liquid crystal polymer, thereby forming an optically anisotropic layer made of the liquid crystal polymer. When a liquid crystalline polymer that is in a glassy state at a temperature lower than the liquid crystal transition temperature is aligned and then cooled to a temperature lower than the liquid crystal transition temperature (that is, glass transition temperature), the alignment can be fixed without impairing the alignment at all. When a liquid crystalline polymer having a crystal phase in a lower temperature portion than the liquid crystal phase is used, the orientation of the liquid crystal state may be broken by cooling. By using a liquid crystalline polymer that becomes a glassy state at a temperature lower than the liquid crystal transition temperature, destruction of the alignment state can be avoided. The cooling can be carried out simply by taking out from the heating atmosphere of the orientation treatment into an atmosphere having a glass transition temperature or lower. In order to increase the production efficiency, a forced cooling means such as air cooling or water cooling may be performed. The thickness of the formed optically anisotropic layer is preferably from 0.1 to 100 μm, more preferably from 0.5 to 50 μm. The twist angle of the twisted nematic orientation is preferably 30 to 5000 °, more preferably 40 to 5000 °.

The optically anisotropic layer is preferably transferred to a cellulose acetate film. The cellulose acetate film has the above-mentioned adhesive layer, and the optically anisotropic layer is adhered to the adhesive layer and peeled off from the alignment film to transfer the optically anisotropic layer onto the cellulose acetate film. Is preferred. When a curable adhesive is used, a process of curing the adhesive (light curing, electron beam curing, heat curing) is performed after lamination. It is preferable to use an adhesive tape for peeling the optically anisotropic layer from the alignment film. The peeling direction is preferably 90 to 180 °, more preferably about 180 °. Mechanical peeling can also be performed using a roll. Thus, an optical compensation sheet is manufactured. In order to protect the surface of the optically anisotropic layer, a protective layer may be provided or a surface protective film may be attached. The protective layer can be formed from a curable acrylic resin or a curable epoxy resin. The produced optical compensation sheet is placed on another support (for example, Japanese Patent No. 2660601).
No. 2,743,117 and JP-A-8-2784.
No. 91, a translucent substrate described in each publication).

[Polarizing Plate] The optical compensation sheet can be used in combination with a polarizing plate. The polarizing plate includes a polarizing film and two transparent protective films disposed on both sides of the polarizing film.
As one of the protective films, the above-described optical compensation sheet can be used. As 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.

The productivity of the polarizing plate depends on the moisture permeability of the protective film.
is important. Polarizing film and protective film are adhered with water-based adhesive
The adhesive solvent is used in the protective film.
To be dried. Protective film moisture permeability
The higher the drying, the faster the drying and the higher the productivity
However, if it is too high, the operating environment of the LCD
(Under high humidity), water enters the polarizing film
Decrease. The moisture permeability of the optical compensation sheet is
The thickness of the acetate film (and the polymerizable liquid crystal compound),
It is determined by free volume, hydrophilicity / hydrophobicity, and the like. Polarizer protection
When used as a protective film, the moisture permeability is 100 to 10
00g / m ^TwoIt is preferably 24 hours, and 30
0 to 700 g / m^Two・ It is even better to be 24 hours
Good. The thickness of the cellulose acetate film is
Lip flow and line speed, or
It can be adjusted by stretching and compression. Main material used
The moisture permeability varies depending on the
It is possible to enclose.

The free volume of the optical compensatory sheet can be adjusted by the drying temperature and time in the case of film formation. Also in this case, since the moisture permeability differs depending on the main material used, it is possible to adjust the free volume to a preferable range. The hydrophilicity / hydrophobicity of the optical compensation sheet can be adjusted by additives. By adding a hydrophilic additive to the above-mentioned free volume, the moisture permeability increases, and conversely, by adding a hydrophobic additive, the moisture permeability can be reduced. By independently controlling the moisture permeability, a polarizing plate having optical compensation capability can be manufactured at low cost and with high productivity.

[Liquid crystal display device] The optical compensatory sheet of the present invention or the polarizing plate combined therewith is advantageously used for a liquid crystal display device, particularly 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. 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 of the polarizing plates, or two optical compensation sheets are provided between the liquid crystal cell and both of the polarizing plates.

In the STN mode liquid crystal cell, the rod-like liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and furthermore, the voltage is more than 18%.
It is twist-oriented from 0 ° to 270 °. In the TN mode liquid crystal cell, the rod-like liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and are further twisted at 60 to 120 °. STN mode and TN mode liquid crystal cells are most frequently used as black and white and color liquid crystal display devices, and are described in many documents. In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied.

The VA mode liquid crystal cell includes (1) a VA mode liquid crystal cell in a narrow sense in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied and substantially horizontally when voltage is applied. In addition to (2) a liquid crystal cell (in the MVA mode) in which the VA mode is multi-domain (in the MVA mode) in order to enlarge the viewing angle.
7. Digest of tech. Papers (Preliminary Collection) 28 (199
7) 845), (3) a liquid crystal cell (n-ASM mode) in which rod-like liquid crystal molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (preliminary paper of the Japanese Liquid Crystal Symposium). Vol. 58-59 (1998)
And (4) SURVAIVEAL mode liquid crystal cell (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 in 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.

[0076]

EXAMPLES Example 1 (Preparation of Cellulose Acetate Film) Dopes for the inner layer and the surface layer having the following compositions were prepared.

──────────────────────────────────── Dope composition For inner layer For surface layer ───セ ル ロ ー ス Cellulose acetate with a degree of acetylation of 60.5% 100 parts by mass 100 parts by mass Phenyl phosphate 7.8 parts by mass 7.8 parts by mass Biphenyldiphenyl phosphate 3.9 parts by mass 3.9 parts by mass Retardation enhancer described below 1.0 part by mass 1.0 part by mass Methylene chloride 450 parts by mass 481 parts by mass Methanol 39 parts by mass 42 parts by mass ────────────────────────────────────

[0078]

Embedded image

The obtained dope for a surface layer was filtered at 50 ° C. with a filter paper (FH025, manufactured by Pall Corporation) having an absolute filtration accuracy of 0.0025 mm. The internal layer dope was filtered at 50 ° C. with a filter paper (# 63, manufactured by Toyo Roshi Kaisha, Ltd.) having an absolute filtration accuracy of 0.01 mm. Using a three-layer co-casting die, the dope for the inner layer was placed inside and the dope for the surface layer was placed on both sides, and the mixture was discharged onto a metal support at the same time to carry out multilayer casting. At this time, the thickness of the inner layer was 45 μm, and the surface layer was 5 μm each.
It was set to be μm and cast. The cast film was dried at 70 ° C. for 3 minutes and at 120 ° C. for 5 minutes, peeled off from the support, and further dried at 130 ° C. for 30 minutes to obtain a cellulose acetate film. The residual solvent amount was 0.5% by mass.

When the optical properties of the obtained cellulose acetate film were examined, the Re retardation value was 4
The nm and Rth retardation values were 40 nm. When the film surface state was observed, the film surface was smooth. 2.0N cellulose acetate film
After immersion in potassium hydroxide aqueous solution at 25 ° C for 2 minutes,
Neutralized with sulfuric acid, washed with pure water and dried. When the surface energy of the film was determined by the contact angle method, it was 63 mN /
m.

(Formation of Optically Anisotropic Layer) A repeating unit (terephthaloyl) derived from terephthalic acid (49 mol%) and a repeating unit derived from 2-methyl-1,4-benzenediol hydroquinone (2-methylphenylene- Liquid crystalline polymer (logarithmic viscosity: 0.20) 97 comprising a non-optically active polyester having 25 mol% of 1,4-dioxy) and 26 mol% of repeating units (phenylene-1,2-dioxy) derived from catechol .2 mass%
And a repeating unit (4,4′-biphenyldicarbonyl) 5 derived from 4,4′-biphenyldicarboxylic acid
0 mol%, a repeating unit derived from 2-methylbutane-1,4-diol (2-methylbutylene-1,4-diol)
Repeating unit (octylene-1,8-diol) derived from 25 mol% of dioxy) and octane-1,8-diol.
A mixture of 2,8% by mass of a liquid crystalline polymer (logarithmic viscosity: 0.14) composed of an optically active polyester having 25% by mol of dioxy) is dissolved in a phenol / tetrachloroethane mixed solvent (60/40% by mass). Thus, an 18% by mass solution was prepared.

The liquid crystalline polymer is dissolved in deuterated chloroform or deuterated trifluoroacetic acid,
MHz 1H-NMR (JEOL JNM-GX40
0) to confirm the composition. The logarithmic viscosity of the liquid crystalline polymer was measured using a Ubbelohde viscometer,
In a mixed solvent of tetotachloroethane (60/40 mass ratio),
It was measured at 30 ° C.

A long film of polyetheretherketone having a thickness of 100 μm and a width of 30 cm was rubbed to form an alignment film. The solution of the liquid crystalline polymer was applied on the alignment film using a roll coater and dried. A heat treatment was performed at 200 ° C. for 45 minutes, followed by cooling to produce an optical compensation sheet (length 100 m) in which the orientation of the liquid crystalline polymer was fixed. The twist angle of the optically anisotropic layer made of a liquid crystalline polymer was -240 °. Δn · d was 0.82 μm.

(Preparation of Optical Compensation Sheet) A bar coater was used on an optically anisotropic layer composed of a liquid crystalline polymer.
An adhesive made of a commercially available ultraviolet-curable acrylic oligomer was applied in a thickness of 5 μm. After the cellulose acetate film was bonded to the surface to which the adhesive was applied with a laminator, the adhesive was cured by irradiating ultraviolet rays. After sticking, hold the end of the polyetheretherketone film and peel in 180 ° direction to peel at the interface with the optically anisotropic layer, transfer the optically anisotropic layer to cellulose acetate film, Was prepared.

(Preparation of Polarizing Plate) A polarizing film was prepared by adsorbing iodine on a stretched polyvinyl alcohol film. Using a polyvinyl alcohol-based adhesive, an optical compensation sheet was attached to one side of the polarizing film such that the cellulose acetate film was on the polarizing film side. A commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to a saponification treatment, and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. Thus, a polarizing plate was produced.

(Preparation of Liquid Crystal Display Device) The polarizing plate on the viewer side provided in a liquid crystal display device (MN-320-X13, manufactured by Sharp Corporation) using an STN type liquid crystal cell was peeled off, and the liquid crystal display device was prepared instead. The obtained polarizing plate was attached to the viewer side via an adhesive so that the optical compensation sheet was on the liquid crystal cell side. The directions of the polarization axis and the rubbing axis of the liquid crystalline polymer were adjusted to maximize the contrast. About the manufactured liquid crystal display device, a measuring machine (EZ-Contrast16)
(OD, manufactured by ELDIM), the viewing angle was measured in eight steps from black display (L1) to white display (L8). As a result, the angle at which the contrast ratio is 2 or more and there is no black-side gradation inversion (inversion between L1 and L2) is 2 degrees in the upward direction.
0 °, 30 ° in the downward direction, and 70 ° in the left-right direction, and a wide viewing angle was obtained. In a similar manner, 20
A polarizing plate was attached to an inch liquid crystal television (manufactured by Sharp Corporation), and the backlight was continuously turned on at normal temperature and normal humidity for 5 hours. Then, the entire black display state was visually evaluated in a dark room. As a result, no light leakage when the backlight was turned on was observed.

Example 2 (Preparation of Cellulose Acetate Film) Dopes for the inner layer and the surface layer each having the following composition were prepared by a cooling dissolution method. That is, mixing the composition,
It was left at room temperature (25 ° C.) for 3 hours. After cooling the obtained heterogeneous gel at -70 ° C for 6 hours, it was heated to 50 ° C and stirred to obtain a solution.

──────────────────────────────────── Dope Composition For Inner Layer For Surface Layer ド ー プセ ル ロ ー ス Cellulose acetate with a degree of acetylation of 59.5% 100 parts by mass 100 parts by mass Phenyl phosphate 7.8 parts by mass 7.8 parts by mass Biphenyldiphenyl phosphate 3.9 parts by mass 3.9 parts by mass Retardation increasing agent used in Example 1 1.5 parts by mass 1.5 parts by mass Methyl acetate 306 parts by mass 327 parts by mass Cyclohexanone 122 parts by mass 131 parts by mass Methanol 30.5 parts by mass 30.5 parts by mass Ethanol 30.5 parts by mass 30.5 parts by mass Silica fine particles having a particle diameter of 20 nm 1.0 part by mass 1.0 part by mass ─────────────── ──────────────────

The resulting dope for a surface layer was filtered at 50 ° C. with a filter paper (FH025, manufactured by Pall Corporation) having an absolute filtration accuracy of 0.0025 mm. The internal layer dope was filtered at 50 ° C. with a filter paper (# 63, manufactured by Toyo Roshi Kaisha, Ltd.) having an absolute filtration accuracy of 0.01 mm. Using a three-layer co-casting die, the dope for the inner layer was placed inside and the dope for the surface layer was placed on both sides, and the mixture was discharged onto a metal support at the same time to carry out multilayer casting. At this time, the thickness of the inner layer was 45 μm, and the surface layer was 5 μm each.
It was set to be μm and cast. The cast film was dried at 70 ° C. for 3 minutes and at 140 ° C. for 5 minutes, and peeled off from the support.
The residual solvent amount at the stripping stage was 30% by mass.

The peeled film was uniaxially stretched by 10% in a tenter stretching machine in an atmosphere of 130 ° C., and when the amount of the residual solvent became 5% by mass or less, 10% by a roll stretching machine.
A longitudinal uniaxial stretching process was performed. The roll surface of the roll stretching machine was mirror-finished. The temperature of the roll was adjusted by circulating heated oil, and the stretching temperature was 140 ° C. After stretching, the film was dried at 130 ° C. for 30 minutes and wound up. The measured stretch ratio was 1.47 times. The thickness was 45 μm.

When the optical characteristics of the obtained cellulose acetate film were examined, the Re retardation value was 4
The nm and Rth retardation values were 45 nm. When the film surface state was observed, the film surface was smooth. 2.0N cellulose acetate film
After immersion in potassium hydroxide aqueous solution at 25 ° C for 2 minutes,
Neutralized with sulfuric acid, washed with pure water and dried. When the surface energy of the film was determined by the contact angle method, it was 63 mN /
m.

(Preparation of Optical Compensation Sheet and Polarizing Plate) Except for using the prepared cellulose acetate film,
In the same manner as in Example 1, an optical compensation sheet and a polarizing plate were produced.

(Preparation of Liquid Crystal Display Device) The polarizing plate on the viewer side provided in a liquid crystal display device (MN-320-X13, manufactured by Sharp Corporation) using an STN type liquid crystal cell was peeled off, and the liquid crystal display device was prepared instead. The obtained polarizing plate was adhered to the viewer side via an adhesive so that the optical compensation sheet was on the liquid crystal cell side. The directions of the polarization axis and the rubbing axis of the liquid crystalline polymer were adjusted to maximize the contrast. About the manufactured liquid crystal display device, a measuring device (EZ-Contrast16) was used.
(OD, manufactured by ELDIM), the viewing angle was measured in eight steps from black display (L1) to white display (L8). As a result, the angle at which the contrast ratio is 2 or more and there is no black-side gradation inversion (inversion between L1 and L2) is 2 degrees in the upward direction.
5 °, 35 ° in the downward direction, and 85 ° in the left-right direction, and a wide viewing angle was obtained. In a similar manner, 20
A polarizing plate was attached to an inch liquid crystal television (manufactured by Sharp Corporation), and the backlight was continuously turned on at normal temperature and normal humidity for 5 hours. Then, the entire black display state was visually evaluated in a dark room. As a result, no light leakage when the backlight was turned on was observed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13363 G02F 1/13363 // B29K 1:00 B29K 1:00 B29L 9:00 B29L 9: 00F Term (reference) 2H049 BA06 BA42 BB20 BB33 BB49 BC02 BC04 BC09 2H091 FA11 FB02 FB12 FC09 FC22 FC25 FD06 FD15 GA06 GA17 KA02 KA10 LA30 4F071 AA09 AC19 AF35Y AH16 BA02 BB02 BC01 4F205 AA73 GA02 GB02 A0273

Claims (9)

[Claims] 1. An optically anisotropic layer comprising a liquid crystalline polymer,
An optical compensatory sheet having a transparent support comprising a cellulose acetate film, wherein the liquid crystalline polymer is in a nematic orientation or a twisted nematic orientation in a glassy state, and the cellulose acetate film has a thickness of 0 to 20 nm.
An optical compensation sheet having a Re retardation value of R and a Rth retardation value of 30 to 70 nm. 2. A cellulose acetate film comprising:
The optical compensatory sheet according to claim 1, which has a thickness of from 70 to 70 µm. 3. A cellulose acetate film comprising:
The optical compensatory sheet according to claim 1, comprising cellulose acetate having an acetylation degree of 9.0 to 61.5%. 4. The cellulose acetate film contains an aromatic compound having at least two aromatic rings in an amount of 0.01 to 20 parts by mass per 100 parts by mass of cellulose acetate.
The optical compensatory sheet according to claim 1, wherein the optical compensatory sheet contains parts by mass. 5. An aromatic compound comprising at least one 1,1
The optical compensation sheet according to claim 4, which is a compound having a 3,5-triazine ring. 6. The optical compensation sheet according to claim 1, wherein the cellulose acetate film is a film produced by a co-casting method. 7. The cellulose acetate film is prepared by dissolving cellulose acetate in a solvent selected from the group consisting of ethers having 2 to 12 carbon atoms, ketones having 3 to 12 carbon atoms and esters having 2 to 12 carbon atoms. The optical compensation sheet according to any one of claims 1 to 6, which is a film produced from a cellulose acetate solution. 8. A step of applying a liquid crystalline polymer which becomes a glass at a temperature lower than the liquid crystal transition temperature on the alignment film; heating the liquid crystal polymer to a temperature higher than the liquid crystal transition temperature to nematic align the liquid crystal polymer. Or a step of twisting nematic alignment; a step of maintaining the orientation of the liquid crystalline polymer and cooling until the liquid crystalline polymer changes to a glassy state, thereby forming an optically anisotropic layer composed of the liquid crystalline polymer; A method for producing an optical compensatory sheet, comprising a step of peeling a layer from an alignment film and transferring the layer onto a cellulose acetate film having a Re retardation value of 0 to 20 nm and an Rth retardation value of 30 to 70 nm. 9. The cellulose acetate film has an adhesive layer, and the optically anisotropic layer is adhered to the adhesive layer and peeled off from the alignment film, whereby the optically anisotropic layer is transferred onto the cellulose acetate film. The method for producing an optical compensation sheet according to claim 8.