JP2002207124A - Polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device restraining generation of bright spot malfunction and having excellent display quality by enlarging a favorably visible region extending over the total region of a display screen. SOLUTION: A polarizing plate comprising a birefringent layer, which is attached on at least one surface of a polarizing layer, of which the in-plane retardation (Re) defined by (ns-nf)×d is 0-200 nm where the refractive index of the birefringent layer in the slow axis direction, that in the fast axis direction, that in the thickness direction and the layer thickness are respectively expressed as ns, nf, nz and d, of which the retardation (Rth) in the thickness direction defined by d×[(ns+nf)/2-nz] is 0-200 nm, and of which Nz defined by (ns-nz)/(ns-nf) is >=1 and further which is a layer composed of a cellulose acetate film containing 0.1-30 mass % aromatic compound with at least two aromatic rings and further having the transmission axis of the polarizing layer and the slow axis of the birefringent layer in a relation parallel to each other is used for the liquid crystal display device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate and a liquid crystal display.

[0002]

2. Description of the Related Art A liquid crystal display device has many features such as low voltage, low power consumption, direct connection to an IC circuit, various display functions, and excellent lightness, etc., and OA equipment such as a word processor and a personal computer. It is widely used as various display means such as televisions, car navigation systems, and monitors for aircraft cockpits. However, the liquid crystal display device has a problem that the viewing angle range for good visibility is narrower than that of the CRT.

The narrow viewing angle range of a liquid crystal display device is caused by the optical anisotropy peculiar to the liquid crystal affecting the viewing angle characteristics of visibility.
It is considered that linearly polarized light incident on the liquid crystal cell via the polarizing layer is converted into elliptically polarized light or the azimuthal angle changes. That is, when the display light in the polarization state transmitted through the liquid crystal cell is directly incident on the polarizing layer on the viewing side, the transmittance decreases with an increase in the viewing angle, that is, the viewing angle with respect to the front (vertical) direction, and the display decreases. It is considered that the visibility is lowered, such as lack of brightness, inversion of gradation, and color change such as coloring.

Hitherto, as a method of enlarging a good viewing area of a liquid crystal display device, that is, a method of enlarging a viewing angle range, a method using a phase difference plate has been known, and various types of phase difference plates have been proposed. . However, the improvement effect is poor and unsatisfactory in terms of the expandability of the viewing angle range of good visibility, or the retardation plate is bonded with an adhesive layer or the like via the transparent protective layer of the polarizing plate to form a transparent protective layer. In addition, there is a problem that a separate film or the like is required, and the thickness and weight increase with the increase in size, and the yield decreases due to a change in characteristics due to adhesion. To solve these problems, a wide-field polarizing plate composed of a polarizing layer and a birefringent layer as disclosed in JP-A-10-153708 has been disclosed. A liquid crystal display device was manufactured using the polarizing plate. However,
In addition to the poor visibility of the edge of the display screen, a failure called a bright spot failure in which a bright spot occurs during black display has occurred, and improvement has been desired. There is still room for improvement in the viewing angle range.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the thickness and weight of a liquid crystal display device, expand a good viewing area (viewing angle range) over the entire area of a display screen, and prevent a bright spot failure. An object of the present invention is to provide a polarizing plate which is unlikely to be generated, and to provide a liquid crystal display device using the polarizing plate which is excellent in display quality (has a wide viewing area and has few bright spot failures).

[0006]

SUMMARY OF THE INVENTION A polarizing plate used in a liquid crystal display device comprises a polarizing layer and transparent protective layers disposed on both sides thereof. The present inventor has found that a polarizing plate that achieves excellent display quality of a liquid crystal display device can be provided by using a cellulose acetate film having adjusted optical characteristics as the transparent protective layer. The details of the adjustment of the optical properties of the cellulose acetate film will be described later. The object of the present invention has been achieved by the following polarizing plates (1) to (3) and the following liquid crystal display devices (4) to (9). (1) A birefringent layer serving also as a transparent protective layer of the polarizing layer is provided on at least one surface of the polarizing layer. The refractive index of the birefringent layer in the slow axis direction is ns, and the refractive index in the fast axis direction is ns. nf, the refractive index in the thickness direction is nz, and the layer thickness is d,
The in-plane retardation (Re) defined by (ns−nf) × d of the birefringent layer is in the range of 0 to 200 nm, and d ×
The phase difference (Rth) in the thickness direction defined by [(ns + nf) / 2｝ −nz] is in the range of 0 to 200 nm, and Nz defined by (ns−nz) / (ns−nf)
Is at least 1, and the birefringent layer is a layer composed of a cellulose acetate film containing an aromatic compound having at least two aromatic rings in the range of 0.1 to 30% by mass. And a slow axis of the birefringent layer is in a parallel relationship.

(2) The cellulose acetate film exhibits optical uniaxiality or optical biaxiality, and the in-plane retardation (Re) of the film varies in any direction along the film surface in any direction. The fluctuation of the retardation (Rth) in the thickness direction in any direction along the film surface is within a range of ± 5 nm with respect to the average value of Re in each direction. (1) The polarizing plate as described in (1), wherein the average value of Rth is within a range of ± 10 nm. (3) The cellulose acetate film has been subjected to a stretching treatment, and the breaking elongation in the stretching direction is 10 to 30%.
(2) The polarizing plate according to (2), wherein

(4) A liquid crystal display device comprising a liquid crystal cell having one side facing the incident light and two polarizing plates disposed on both sides thereof, wherein at least one of the polarizing plates is at least one of the polarizing layers. A birefringent layer also serving as a transparent protective layer of a polarizing layer is provided on one surface, and the refractive index of the birefringent layer in the slow axis direction is ns, the refractive index in the fast axis direction is nf, and the refractive index in the thickness direction. Is nz and the layer thickness is d, the in-plane phase difference (R) of the birefringent layer defined by (ns−nf) × d
e) is in the range of 0 to 200 nm, and d × [(ns +
nf) / 2 {-nz] is in the range of 0 to 200 nm in the thickness direction, and (n
Cellulose wherein Nz defined by (s-nz) / (ns-nf) is 1 or more, and the birefringent layer further contains an aromatic compound having at least two aromatic rings in a range of 0.1 to 30% by mass. A liquid crystal display device comprising a layer made of an acetate film, wherein the transmission axis of the polarizing layer and the slow axis of the birefringent layer are in a parallel relationship.

(5) The cellulose acetate film exhibits optical uniaxiality or optical biaxiality, and the in-plane retardation (Re) varies in any direction along the film surface in any direction. The fluctuation of the retardation (Rth) in the thickness direction in any direction along the film surface is within a range of ± 5 nm with respect to the average value of Re in each direction. The liquid crystal display device according to (4), wherein the average value of Rth is within a range of ± 10 nm. (6) The cellulose acetate film has been subjected to a stretching treatment, and the breaking elongation in the stretching direction is 10 to 30%.
(5) The liquid crystal display device according to (5), wherein

(7) The polarizing layer of the polarizing plate is an orthogonal linear polarizer, the birefringent layer exhibits optical biaxiality, and the axis of the minimum principal refractive index is parallel to the homeotropic direction. (4) The liquid crystal display device according to (4). (8) The product of the absolute value of the difference between the other two main refractive indices of the birefringent layer of the polarizing plate and the thickness of each layer of the birefringent layer is 90 to 150.
The liquid crystal display device according to (7), wherein the liquid crystal display device has a range of nm. (9) The liquid crystal display device according to (8), wherein the polarizing plate further has an optical reflection layer, and the optical reflection layer is disposed on a side of the cell opposite to a side facing the incident light. .

[0011]

The polarizing plate used in the liquid crystal display device comprises a polarizing layer and transparent protective layers disposed on both sides of the polarizing layer. In a conventional liquid crystal display device, a polarizing plate and a retardation plate are bonded to each other to expand a region with good visibility. In the present invention,
A birefringent layer is formed from a cellulose acetate film having adjusted optical characteristics, and this birefringent layer is used as a transparent protective layer of the polarizing layer. This makes it possible to omit the separate transparent protective layer and its bonding process, to reduce the thickness and weight even when the polarizing layer is large, and to prevent a decrease in yield due to a change in characteristics due to the bonding process. Also, by setting the transmission axis of the polarizing layer and the slow axis of the birefringent layer in a parallel relationship, it is possible to prevent a decrease in brightness and contrast in the front direction perpendicular to the polarizing layer surface without being affected by the phase difference of the birefringent layer. In addition, by compensating for the change in the state of linearly polarized light due to the birefringence of the liquid crystal cell via the birefringent layer, there is no color change such as coloring or gradation inversion, and the area of good visibility with excellent contrast and brightness is expanded. Thus, a liquid crystal display device having a wide viewing angle range can be obtained. In the present invention, the in-plane retardation is in the range of 0 to 200 nm by adjusting the production conditions of the cellulose acetate film (the type and amount of the additive, the conditions of the stretching treatment, etc.), and the retardation in the thickness direction is controlled. Is in the range of 0 to 200 nm. By using a polarizing plate in which the birefringent layer is integrated with the polarizing layer, the area of good visibility of the liquid crystal display device is expanded. Further, by adjusting the stretching treatment conditions of the cellulose acetate film (detailed conditions such as the amount of residual solvent contained in the film at the start of stretching),
Variations in optical characteristics in the plane direction of the film (birefringent layer) can be made uniform, and even in a large-sized liquid crystal display device, the visible region is enlarged over the entire region of the display screen, there is no chromaticity defect, and all wavelengths A liquid crystal display device having high extinction capability over a range can be obtained. Further, by adjusting the stretching conditions, the breaking elongation in the stretching direction of the film can be reduced by 10%.
By setting the content to 30% or less, generation of chips generated when the film is cut (or punched) and used can be suppressed, and a bright spot failure occurring in the liquid crystal display device can be prevented.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate of the present invention is provided with a birefringent layer provided on at least one surface of a polarizing layer, which also serves as a transparent protective layer of the polarizing layer, and a transmission axis of the polarizing layer and a birefringent layer. Has a parallel relationship with the slow axis. One example is shown in FIG.
Reference numeral 1 denotes a polarizing layer, 3 denotes a birefringent layer, and arrows indicate directions of a transmission axis and a slow axis. Reference numeral 2 denotes an adhesive layer. The birefringent layer is made of a cellulose acetate film containing an aromatic compound having at least two aromatic rings in a range of 0.1 to 30% by mass. By using a cellulose acetate film to which an aromatic compound is added, the in-plane retardation and the retardation in the thickness direction of the birefringent layer can be strictly adjusted, and the area of good visibility of the liquid crystal display device is expanded. I can do it.

As the polarizing layer, an appropriate layer capable of obtaining light of a predetermined polarization state can be used. As the polarizing layer, a layer that can obtain transmitted light in a linearly polarized state is preferable.
Examples of the polarizing layer, a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or a hydrophilic polymer film such as an ethylene-vinyl acetate copolymer-based partially saponified film, iodine, a dichroic dye, or the like. Examples thereof include a film stretched by adsorbing both films, and a polarizing film composed of a polyene oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride.

The polarizing layer may be of a reflection type having a reflection layer. The reflective polarizing layer is used to form a liquid crystal display device or the like that reflects and reflects incident light from the viewing side (display side). There is an advantage that the display device can be thinned.

The reflective polarizing layer can be formed by, for example, providing a reflective layer made of metal or the like on one side of the polarizing layer via a transparent resin layer or the like, if necessary. Specific examples of the reflective layer include a transparent resin layer such as a protective film that has been matted as necessary, and a foil or a vapor-deposited film made of a reflective metal such as aluminum provided on one surface of the transparent resin layer. Examples thereof include those in which a metal reflective layer is provided on a fine surface uneven structure by a method such as an evaporation method or a plating method.

The polarizing plate of the present invention has a birefringent layer disposed as a transparent protective layer on one or both sides of a polarizing layer (preferably a polarizing film). Therefore, at least one side of the polarizing layer has a birefringent layer also serving as a transparent protective layer, and has no transparent protective layer other than the birefringent layer.

As the birefringent layer, a cellulose acetate film exhibiting a phase difference due to birefringence is used. The cellulose acetate film contains an aromatic compound having at least two aromatic rings in a range of 0.1 to 30% by mass. The light transmittance of the cellulose acetate film is
It is preferably at least 70%, more preferably at least 80%, even more preferably at least 85%.

The cellulose acetate film is formed from cellulose acetate. The degree of acetyl substitution of cellulose acetate is preferably in the range of 2.4 to 3.0, and more preferably in the range of 2.5 to 2.9. Degree of polymerization of cellulose acetate (viscosity average)
Is preferably in the range of 200 to 700, and 25
It is more preferably in the range of 0 to 550, and 250
More preferably, it is in the range of 350 to 350. The viscosity average degree of polymerization can be measured with an Ostwald viscometer,
It is determined from the measured intrinsic viscosity [η] of cellulose acylate by the following equation. DP = [η] / Km (where D is
P is the viscosity average degree of polymerization, and Km is a constant of 6 × 10 ⁻⁴ ).
Cellulose acetate may use only unused (virgin) flakes, but more preferably 3 to 95% by mass of cellulose acetate film waste formed, more preferably 6 to 80% by mass, and It is preferable to use a mixture of 10% by mass or more and 70% by mass or less.

In the present invention, in order to adjust the retardation value (retardation) of the birefringent layer, an aromatic compound having at least two aromatic rings is used as a retardation increasing agent in the range of 0.1 to 30% by mass. To the cellulose acetate film. The retardation increasing agent is preferably used in an amount of 0.1 to 30 parts by mass, more preferably 0.3 to 10 parts by mass, based on 100 parts by mass of cellulose acetate.
It is more preferably used in the range of 0.5 to 10 parts by mass, and most preferably used in the range of 0.5 to 3 parts by mass. Two or more retardation increasing agents may be used in combination. The retardation enhancer is 230-36
It preferably has a maximum absorption wavelength in a wavelength region of 0 nm. Further, it is preferable that the retardation increasing agent has substantially no absorption in the visible region.

An aromatic compound having at least two aromatic rings is used as a retardation increasing agent. This “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle, and is a 5-membered ring, a 6-membered ring.
It is preferably a 5- or 6-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, an oxazole ring,
Includes 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 1,3,5-triazine ring. Specific examples of the aromatic ring include a 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 rings are preferred. The number of these aromatic rings is preferably 2 to 20, more preferably 2 to 12, and most preferably 2 to 6.
The bonding relationship between two aromatic rings can be classified into (a) a case where a condensed ring is formed, (b) a case where they are directly connected by a single bond, and (c) a case where they are bonded via a linking group. ,
(A spiro bond cannot be formed), but the bonding relationship is (a)-
Any of (c) may be used.

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 biphenylene ring, Naphthacene ring, pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline Ring, isoquinoline ring,
A quinolidine ring, a quinazoline ring, a cinnoline ring, a quinoxaline ring, a phthalazine ring, a pteridine ring, a carbazole ring, an acridine ring, a phenanthridine ring, a xanthene ring, a phenazine ring, a phenothiazine ring, a phenoxatiin ring, a phenoxazine ring and a thianthrene ring; included. 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. Two aromatic rings may be linked by two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings. The connecting group (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, alkenylene group, alkynylene group, -CO-, -O-, -NH-, -S-, or a combination thereof. 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 molecular weight of the retardation increasing agent is preferably from 300 to 800. Specific examples of the retardation increasing agent include JP-A-2000-111914 and JP-A-2000-275434.
And PCT / JP00 / 02619.

[Production of Cellulose Acetate Film]
It is preferable to produce a cellulose acetate film by a solvent casting (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.
Organic solvents include ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and 3 to 12 carbon atoms.
And a solvent selected from halogenated hydrocarbons having 1 to 6 carbon atoms. Ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, -O-, -CO- and -COO-) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any 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.

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. 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 is preferably long enough to reach near the wall of the container. It is preferable to provide a scraping blade at the end of the stirring blade 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 a 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 a usual 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 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 mixing of water 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 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 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.

From the prepared cellulose acetate solution (dope), a cellulose acetate film is produced by a solvent casting method. It is preferable to add the above-mentioned retardation increasing agent to the dope. In the present invention, the obtained cellulose acetate solution may be cast in a single layer on a smooth band or a drum, or may be cast in a plurality of layers using a plurality of cellulose acetate solutions. When casting a plurality of cellulose acetate solutions, the cellulose acetate solution may be cast from a plurality of casting ports provided at intervals in the traveling direction of the support, and a film may be produced while being laminated, For example, JP-A-61-158414, JP-A-1-122419
And the methods described in each specification of JP-A-11-198285 can be used. Alternatively, a film may be produced by casting a cellulose acetate solution from two casting ports, for example, Japanese Patent Publication No. 60-2756.
No. 2, JP-A-61-94724, JP-A-61-947
No. 245, Japanese Unexamined Patent Application Publication No.
158413 and JP-A-6-134933 can be used. Further, a method of casting a polymer film in which a flow of a high-viscosity polymer solution described in the specification of JP-A-56-162617 is wrapped with a low-viscosity polymer solution and the high- and low-viscosity polymer solutions are simultaneously extruded is used. To form a film.

Alternatively, by 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.
A film may be produced, for example, Japanese Patent Publication No. 44-202.
The method described in the specification of No. 35 can be used. The polymer solution to be cast may be the same solution,
A different polymer solution may be used and is not particularly limited. In order to give a function to a plurality of polymer layers, a polymer solution corresponding to the function can be extruded from each casting port. In order to achieve the optical suitability and mechanical suitability of the birefringent layer in the invention, a laminate is more preferable, and the number of layers is preferably 2 to 10, more preferably 2 to 6.
Layer, more preferably 2 to 4 layers. Further, the polymer solution of the present invention can simultaneously cast other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, and a polarizing layer). The cellulose acetate film may be provided with a matting layer containing a matting agent and a polymer on one or both sides to improve the handleability during production. As the matting agent and the polymer, the materials described in the specification of JP-A-10-44327 can be suitably used.

In order to improve the mechanical properties of the cellulose acetate film or to increase the drying speed,
Plasticizers can be added. As the plasticizer, a phosphoric acid ester or a carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP)
Is included. Representative carboxylic esters include phthalic esters and citric esters. Examples of phthalates include dimethyl phthalate (DMP),
Includes 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 (OACTE)
And O-acetyltributyl citrate (OACTB)
Is included. Examples of other carboxylic esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic esters. Phthalate ester plasticizers (DMP, DEP, DB
P, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. Since the amount of the plasticizer added may affect the wavelength dispersion, it needs to be adjusted together with the amount of the retarder. The amount of the plasticizer added is preferably in the range of 0.1 to 25% by mass of the amount of the cellulose acetate.
And more preferably in the range of 20 to 20% by mass.
Most preferably, it is in the range of 15 to 15% by mass.

A deterioration inhibitor (eg, an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, an amine) may be added to the cellulose acetate film. Regarding the deterioration inhibitor, see JP-A-3-19920.
No. 1, 5-1907073, 5-194789
No. 5-271471 and No. 6-107854
There is a description in each gazette of the issue. The amount of the deterioration inhibitor added is preferably in the range of 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably in the range of 0.01 to 0.2% by mass. When the amount is less than 0.01% by mass, the effect of the deterioration inhibitor is hardly recognized. If the amount exceeds 1% by mass, bleed out (bleeding out) of the deterioration inhibitor onto the film surface may be observed. Particularly preferred examples of the deterioration inhibitor include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

It is preferable to perform an orientation treatment to impart birefringence to the cellulose acetate film. Examples of the orientation treatment include a uniaxial or biaxial stretching treatment at a free end or a fixed end. When producing an optically uniaxial support, a uniaxial stretching treatment or a biaxial stretching treatment may be performed. When producing an optically biaxial support, it is preferable to carry out an unbalanced biaxial stretching treatment. In unbalanced biaxial stretching, a polymer film is stretched in a certain direction at a constant magnification, and then stretched in a direction perpendicular thereto to a higher magnification. The bidirectional stretching may be performed simultaneously. In the present invention, a liquid crystal cell having uniform optical characteristics over the entire width and a wide visible region of the entire region, hardly causing a bright spot failure in a liquid crystal cell, having no chromaticity defect, and having a high extinction capability over the entire wavelength range is achieved. For this purpose, the film is stretched by the following method. High Residual Solvent Stretching Stretching after solvent film formation, but with solvent remaining
Stretching (with insufficient drying) is preferred. Stretching is started when the amount of the residual solvent relative to the cellulose acetate film is in the range of 5 to 50% by mass, more preferably in the range of 10 to 46% by mass, and still more preferably in the range of 15 to 40% by mass. Heat treatment before stretching 60 to 160 ° C, more preferably 70 to 1 before stretching
At 50 ° C, more preferably in the range of 80 to 140 ° C,
The heat treatment is preferably performed for 5 seconds to 10 minutes, more preferably for 10 seconds to 8 minutes, and still more preferably for 15 seconds to 5 minutes. These heat treatments are preferably performed while holding both ends of the cellulose acetate film. Further, it is more preferable to carry out the following stretching online after these heat treatments.

The stretching ratio is preferably in the range of 1.05 to 1.6 times, more preferably in the range of 1.1 to 1.5 times, and more preferably in the range of 1.1 to 1 times. More preferably, it is in the range of .4 times. Compared to a stretching process applied to a general polymer film to obtain birefringence of 3 times or more, the film is stretched at an extremely small ratio. The stretching speed is preferably in the range of 5 to 100% / min, more preferably in the range of 10 to 80% / min, and even more preferably in the range of 15 to 70% / min. The stretching speed of the stretching treatment applied to a general polymer film to obtain birefringence is 500% /
Min. Temperature Difference During Stretching The temperature at both ends of the cellulose acetate film in the stretching zone is made 1 to 10 ° C., more preferably 1 to 8 ° C. lower than the center. Thereby, uniform optical characteristics (Re, Rth) can be achieved in the width direction of the film. Normally, the optical characteristics in the longitudinal direction of the film are uniform unless the manufacturing conditions change over time. Accordingly, by making the optical characteristics in the width direction uniform, a cellulose acetate film having uniform in-plane optical characteristics can be obtained. In addition, in a normal stretching treatment, after the stretching, heat setting is performed at a temperature exceeding 200 ° C., but in the present invention, it is more preferable not to perform the heat setting.

A transparent support having optical uniaxiality or optical biaxiality and a transparent support having optical isotropy (eg,
Cellulose acetate film).
The thickness of the transparent support is preferably from 10 to 500 μm, more preferably from 50 to 200 μm.

By adjusting the stretching conditions, the in-plane retardation (Re) of the cellulose acetate film measured at a wavelength of 550 nm varies in any direction along the film surface. ± 5 nm or less based on the average value of Re;
In addition, the fluctuation of the retardation (Rth) in the thickness direction in any direction along the film surface is ± 1 with respect to the average value of Rth in each direction in any direction.
Preferably, the thickness is 0 nm or less. Fluctuation in in-plane retardation (Re) of the in-plane retardation (Re) measured at a wavelength of 550 nm of the transparent film in any direction along the film surface should be ± 4 nm or less in any direction based on the average value of Re in each direction. Is more preferred. The variation in the in-plane retardation (Rth) of the transparent film measured at a wavelength of 550 nm in any direction along the film surface is the same as the Rth in any direction.
Is more preferably ± 8 nm or less based on the average value of By suppressing the fluctuation of the optical characteristics in the plane of the cellulose acetate film, it is possible to make the viewing angle characteristics uniform over the entire area of the display screen when used in a liquid crystal display device.

By adjusting the stretching conditions, the elongation at break in the stretching direction of the cellulose acetate film (in the case of stretching in two or more axes, the stretching axis direction at a high magnification) is 10 to 30.
%, More preferably 15 to 30%, even more preferably 20 to 30%. By adjusting the breaking elongation, the plane orientation of the cellulose acetate film is promoted, the generation of chips generated from the transparent film when the optical compensation sheet is cut can be suppressed, and the bright spot failure can be reduced. The deviation from the stretching axis of the slow axis (in the case of stretching in two or more axes, indicates the high-magnification stretching axis) is ±
It is preferably 5 degrees or less, more preferably ± 4 degrees or less, and still more preferably ± 3 degrees or less. If the slow axis is delayed with respect to the stretching axis,-is displayed, and if it is advanced, + is displayed.

The thickness of the cellulose acetate film (birefringent layer) thus obtained is preferably in the range of 5 to 500 μm, and is preferably in the range of 10 to 35 μm.
It is more preferably in the range of 0 μm,
More preferably, it is in the range of 0 μm.

In order to improve the adhesion between the cellulose acetate film and a layer provided thereon (such as an adhesive layer),
A surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment) may be performed on the cellulose acetate film. An ultraviolet absorber may be added to the cellulose acetate film. An adhesive layer (undercoat layer) may be provided on the cellulose acetate film. The adhesive layer is described in JP-A-7-333433. The thickness of the adhesive layer is preferably in the range of 0.1 to 2 μm, more preferably in the range of 0.2 to 1 μm. In the present invention, a film oriented in the thickness direction or a film whose main refractive index in the thickness direction is inclined with respect to the normal direction of the film can be used for forming the birefringent layer. The retardation characteristics can also be adjusted by controlling the orientation treatment conditions such as the stretching method and the stretching conditions, and changing the forming material.

The birefringent layer that can be preferably used is arranged so that the transmission axis of the polarizing layer and the slow axis of the birefringent layer are in a parallel relationship, and when the viewing angle deviates from the front direction, the birefringent layer is retarded. Since the phase axis direction changes and the parallel relation shifts, and the optical anisotropy of the birefringent layer develops in accordance with the shift amount, the retardation is determined based on the in-plane retardation of the birefringent layer and Nz. The amount of change in the phase axis is controlled to adjust the amount of expression of optical anisotropy in the birefringent layer.

Note that the in-plane retardation (Re = △ nd) is such that the refractive index in the slow axis direction is ns and the refractive index in the fast axis direction is nf.
When (ns> nf), the refractive index in the thickness direction is nz, and the layer thickness is d, it is defined by the formula: (ns−nf) × d. The thickness direction retardation (Rth) is d × [(ns + nf) / 2} −
nz]. Nz is calculated by the formula: (ns-nz)
/ (Ns-nf). Each refractive index has a wavelength of 55
Based on 0 nm.

In other words, optimizing the in-plane retardation and Nz of the birefringent layer can reduce the influence of the phase difference of the birefringent layer in the front direction due to the parallel arrangement of the polarizing layer transmission axis and the birefringent layer slow axis. This means that it is advantageous for avoiding a decrease in the luminance and contrast that have been prevented, and for expanding the viewing angle range for good visibility in directions other than the front.

The optimum value of the birefringent layer in the present invention is such that the in-plane retardation is in the range of 0 to 200 nm, and the retardation in the thickness direction is in the range of 0 to 200 nm. The in-plane retardation is more preferably in the range of 30 to 170 nm, and even more preferably in the range of 60 to 140 nm. Further, Nz of the birefringent layer is 1 or more, more preferably in the range of 1.2 to 4, and preferably 1.5 to 3.
More preferably, it is in the range of 5. In-plane retardation is 2
In a birefringent layer having a thickness of more than 00 nm or a birefringent layer having an Nz of less than 1, gradation inversion is likely to occur, and the power for enlarging the viewing angle range for good visibility is poor.

The thickness of the birefringent layer can be appropriately determined depending on the intended retardation characteristics and the like because it is related to the in-plane retardation as described above, but is generally in the range of 5 to 500 μm and 10 to 350 μm. And more preferably in the range of 20 to 200 μm. In addition, the birefringent layer obtained in the present invention can be preferably used as a compensation medium layer used in a liquid crystal cell utilizing an electrically controlled birefringent effect described in JP-B-7-69536. Further, a polarizing plate can be formed by integrating the birefringent layer with the polarizing means described in the publication.

[Polarizing Plate] The polarizing plate of the present invention is preferably used for compensating viewing angle characteristics due to birefringence of a liquid crystal cell. In the process of manufacturing a liquid crystal display device, a birefringent layer and a polarizing layer are sequentially laminated separately to form a polarizing plate, or a birefringent layer and a polarizing layer are laminated in advance to form a polarizing plate. Can also be used for the production of The latter method of forming a polarizing plate in advance has an advantage that the stability of quality and laminating workability are excellent and the manufacturing efficiency of the liquid crystal display device can be improved.

The birefringent layer is laminated on the polarizing layer so that the transmission axis of the polarizing layer and the slow axis of the birefringent layer are in a parallel relationship, and the parallel relationship is strictly parallel. The state is not limited to the state, and a work placement error or the like is allowed. If there is a variation in the direction of the transmission axis or the slow axis, for example, they are arranged in a parallel relationship based on the average direction as a whole.

The lamination of the polarizing layer and the birefringent layer can be fixed using an adhesive or the like as necessary. It is preferable to adhere and fix it from the viewpoint of preventing displacement of the axial relationship. For the bonding, for example, a suitable adhesive such as a transparent pressure-sensitive adhesive such as a polyvinyl alcohol-based adhesive, an acrylic-based or silicone-based, a polyester-based or a polyurethane-based, a polyether-based or a rubber-based adhesive can be used. Is not particularly limited. From the viewpoint of preventing a change in optical characteristics, it is preferable that a high-temperature process is not required for curing or drying, and a material that does not require a long curing treatment or drying time is preferable. Further, a material that does not cause peeling or the like under heating or humidifying conditions is preferable.

The adhesive has a weight average molecular weight of at least 100,000 containing a monomer such as butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate or (meth) acrylic acid as a component. Glass transition temperature is 0 ℃
Acrylic pressure-sensitive adhesives comprising the following acrylic polymers are particularly preferred. Acrylic pressure-sensitive adhesives are preferred because they are excellent in transparency, weather resistance, heat resistance and the like. When layers having different refractive indices are laminated, an adhesive or the like having an intermediate refractive index is preferably used from the viewpoint of suppressing reflection loss.

The adhesive may be, if necessary, for example, a filler or pigment comprising natural or synthetic resin, glass fiber or glass beads, metal powder or other inorganic powder, a coloring agent or an antioxidant. Can be added.
Further, an adhesive layer exhibiting light diffusing properties can be formed by incorporating fine particles.

Each of the polarizing layer, the birefringent layer and the adhesive layer is made of an ultraviolet absorbent such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex salt compound, or the like. UV-absorbing ability can be imparted by a method of treating with UV light.

[Liquid Crystal Display Device] A liquid crystal display device can be manufactured as follows using the polarizing plate of the present invention comprising a polarizing layer and a birefringent layer. The polarizing plate of the present invention can be preferably used for a liquid crystal display device utilizing an electrically controlled birefringence effect. Taking such a liquid crystal display device as an example,
A liquid crystal display device using the polarizing plate of the present invention will be described. A liquid crystal display device utilizing the electrically controlled birefringence effect has a liquid crystal cell with one side facing incident light. The liquid crystal cell is formed by sandwiching a nematic liquid crystal layer having positive optical anisotropy between two substrates. At least two electrodes are arranged on both sides of the nematic liquid crystal layer, and the electrodes arranged on one side facing the incident light are transparent. When no voltage is applied between the electrodes, the molecules of the nematic liquid crystal layer are oriented substantially in the homeotropic direction. Outside the liquid crystal cell, at least one polarizing layer for polarizing incident light and at least one birefringent layer for compensating for birefringence of the nematic liquid crystal layer are arranged. At least one polarizing layer is arranged on the side facing the incident light. The polarizing layer is an orthogonal linear polarizer, at least one birefringent layer is a homeotropic structure for improving oblique observation, and at least one birefringent layer has three main refractive indexes. Each of the principal indices has a corresponding axis, one of the principal indices is smaller than the other two principal indices, and the axis corresponding to the minimum principal index is parallel to the homeotropic direction. It is preferred that it is. The product of the absolute value of the difference between the other two main refractive indices and the thickness of each of the birefringent layers is 90 to 15
More preferably, it is in the range of 0 nm. The polarizing layer and the birefringent layer are integrated to constitute the polarizing plate of the present invention. The birefringent layer is a layer made of a cellulose acetate film containing an aromatic compound having at least two aromatic rings in a range of 0.1 to 30% by mass.

If this birefringent layer is used in order to compensate for the birefringence of the nematic liquid crystal layer having a homeotropic structure for oblique observation of the cell, a high contrast can be ensured even at a large angle of up to 70 degrees. it can. Furthermore, the liquid crystal display device of the present invention has no chromaticity defect described above,
Effectively compensates for birefringence on any light incident surface,
A cell having an arbitrary liquid crystal thickness can be obtained, including a very large thickness required for manufacturing a composite screen. (The thickness of the birefringent layer is adjusted to ensure optimal compensation as a function of the thickness of the liquid crystal layer). Further, the liquid crystal display device of the present invention has an advantage that it is compatible with any polarizing layer (linear, circular or elliptically polarized light). In the present invention, the thickness of the liquid crystal is considerably large, so that the multiplicity is high, and there is no chromatic aberration,
Therefore, a liquid crystal display device that can maintain the purity and stability of the displayed color when viewed obliquely can be manufactured.

In a liquid crystal display device according to an embodiment of the present invention, the two electrodes are transparent, have two complementary polarizing layers disposed on both sides of the electrodes, and the birefringent layer is a polarizing layer. And at least one of the liquid crystal cells.
The term "complementary polarizing layer" means, for example, two orthogonal linear polarizers, or two complementary elliptical polarizers, circular polarizers, which may be relative to each other with respect to the incident plane lightwave in the homeotropic direction, or to the left and right Are complementary to each other. When the liquid crystal display device of the present invention is used for a color display, the birefringent layer may further include a substrate provided with at least one color filter. This substrate may be fixed to the birefringent layer. According to another embodiment, the two polarizing layers are orthogonal linear polarizers, the birefringent layer exhibits optical biaxiality, and the axis of its minimum principal refractive index is parallel to the homeotropic direction. It is. In one embodiment of the invention in which the electrodes are transparent, the birefringent layer further comprises an optically reflective layer, which is arranged on the side of the cell opposite to the side facing the incident light. Is preferred.

Hereinafter, the measuring method used in the present invention will be described. Retardation, Refractive Index The prepared cellulose acetate film (birefringent layer) was measured for retardation at a wavelength of 550 nm using an ellipsometer (M-150, manufactured by JASCO Corporation). In order to evaluate the variation in the width direction of the transparent film (or the optical compensation sheet), the retardation values were measured at intervals of 30 mm over the entire width in the width direction. Also, the refractive index measurement by Abbe refractometer,
From the measurement of the angle dependence of the retardation, the wavelength was 550.
The refractive index ns in the in-plane slow axis direction, the refractive index nf in the fast axis direction and the refractive index nz in the thickness direction in nm are obtained,
The value (Nz) of (ns-nz) / (ns-nf) was calculated. Measurement of misalignment The angle between the direction of the slow axis and the stretching direction of the cellulose acetate film is determined by an automatic birefringence meter (KOBRA-21AD).
H, Oji Scientific Instruments). Each measurement is performed at any 10 points in the film, the average direction is determined,
The difference between this and the stretching axis was determined. Elongation at break Sampling is performed to a length of 15 cm and a width of 1 cm along the stretching direction (in the case of stretching in both MD / TD, the higher stretching ratio). Using a tensile tester, the distance between chucks was 10 cm.
At a temperature of 25 ° C. and a relative humidity of 60% to determine the elongation at break.

[0061]

[Example 1 and Comparative Example 1] (Preparation of birefringent layer) A dope having the following composition was cast on a band by a solution casting method to form a film, and subjected to the following stretching treatment. A cellulose triacetate film (birefringent layer) having a width of 1.5 m and a thickness of 70 μm was produced. The degree of acetyl substitution was measured from the 13C-NMR spectrum by the method described in Polymer Journal 17.1065-1069 (1985).組成 Composition of cellulose acetate solution (dope) ─────── ───────────────────────────── Cellulose acetate (degree of substitution: 2.8) 118 parts by mass Triphenyl phosphate 9.19 parts by mass Biphenyl 4.60 parts by mass of diphenyl phosphate 2.36 parts by mass of tribenzylamine 530 parts by mass of methyl acetate 99.4 parts by mass of ethanol 33.1 parts by mass of butanol The following retardation increasing agent 1.20 parts by mass ─────── ─────────────────────────────

[0062]

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Thereafter, the film was uniaxially stretched in the machine direction under the following conditions. In addition, the residual solvent amount in the film before stretching,
After precisely weighing about 1 g of the cellulose acetate film sampled immediately before stretching (referred to as X (g)),
And then weighed again (Y (g)),
It is expressed as 100 × (XY) / X (%).

──────────────────────────────────── Stretching conditions Example 1 Comparative example 1 延伸残留 Residual solvent in film 30% by mass 3% by mass Heat treatment before stretching / temperature 155 C. Not performed Time 17 seconds Not performed Stretching ratio 1.20 times 1.20 times Stretching temperature 130 ° C. 130 ° C. Stretching temperature difference (center-both ends) 3 ° C. 0 ° C. Stretching speed 20% / min 300% / min ── ──────────────────────────────────

The cellulose acetate film (birefringent layer) thus obtained had the following characteristics. Further, a transparent support prepared according to Example 1 of JP-A-10-153708 was used as Comparative Example 2 and also showed characteristics.

特性 Characteristics of Transparent Support Example 1 Comparative Example 1 Comparative Example 2 Ｒｅ Re / average value (nm) 25 25 100 fluctuation Range (nm) -1 to +1 -8 to +9 -16 to +20 Rth / average value (nm) 50 60 300 Variation range (nm) -3 to +3 -12 to +14 -25 to +30 Nz 1.5 0.8 2.0 Axis misalignment (゜) 1 15 20 Elongation at break (%) 28 8 90 ───── (Preparation of polarizing plate) A polyvinyl alcohol film having a thickness of 80 μm is stretched 5 times in an aqueous iodine solution and then dried to prepare a polarizing film (polarizing layer). did. The birefringent film (birefringent layer) prepared as described above was placed on one side of the obtained polarizing film via an acrylic adhesive layer having a thickness of 20 μm, and the transmission axis of the polarizing layer and the slow axis of the birefringent film were used. Were bonded in parallel so that a polarizing plate was obtained.

[Example 2] (Preparation of birefringent layer) A dope having the following composition was prepared, and a dope was cast on a band by a solution monolayer method or a laminating method to form a film. Then, the following stretching treatment was performed to prepare a cellulose triacetate film (birefringent layer) having a width of 1 m and a thickness of 100 μm. (1) Dope composition

<< Composition of Cellulose Acetate Solution (Dope) >>セ ル ロ ー ス Cellulose acetate (degree of substitution 2.6) 87 parts by mass Triphenyl phosphate 10 parts by mass Retardation increasing agent (UV absorber: TM165, manufactured by Sumitomo Chemical Co., Ltd.) 3 parts by mass Methylene chloride 510 parts by mass Methanol 44 parts by mass ────────────────

(2) Membrane-forming method Single-layer method The solution (dope) obtained by the above method was applied to filter paper (No. 24).
After filtering through a filter cloth made by Azumi Filter Paper Co., Ltd.) and flannel, the solution was fed to a pressure die by a fixed-quantity gear pump, and cast using a band casting machine having an effective length of 6 m. The band temperature was 0 ° C. Using a three-layer co-casting die, dope of the above composition from the inner layer,
The dope diluted by increasing the amount of solvent to 10% on both sides was simultaneously discharged onto a metal support and cast in a multilayer manner, and then the casting film was peeled off from the support and dried to obtain a three-layer cellulose acetate. A film laminate (inner layer thickness: thickness of each surface layer = 8: 1) was produced. This was band-cast in the same manner as in the single-layer method. (3) Stretching method The film obtained under the following conditions was stretched.

延伸 Stretching conditions Example 2-1 Example 2- 2 Comparative Example 3 膜 Film forming method Single layer method Laminating method Laminating method Residual solvent in film 25% by mass 35% by mass 55% by mass Heat treatment before stretching / Temperature 100 ° C 130 ° C No time 60 seconds 30 seconds No time Stretch ratio 1.10 1.30 1.20 120 ° C 140 ° C 130 ° C Stretching temperature difference (center-ends) 5 ° C 1 ° C 0 ° C Stretching rate 10% / min 40% / min 300% / min ──────────────── ────────────────────

The cellulose acetate film (birefringent layer) thus obtained exhibited the following characteristics.

特性 Characteristics of the transparent support Example 2-1 Example 2-2 Comparative Example 3 Re / average value (nm) 20 30 35 Fluctuation range (nm) −2 to +2 −4 to +4 −10 to +12 Rth / average value (nm) 30 20 68 Fluctuation range (nm) −8 to +8 −6 to +6 −15 to +19 Nz 8 2.0 0.7 Axis misalignment (゜) 0 2 19 Elongation at break (%) 14 21 33 ─────────────────────────── ─────────

(Preparation of Polarizing Plate) A polarizing plate was prepared in the same manner as in Example 1 except that the obtained cellulose acetate film (birefringent layer) was used.

[Example 3] (Preparation of birefringent layer) A dope having the following composition was prepared, and a dope was cast on a band by the following single layer method by a solution film forming method to form a film. Stretching, width 1m, thickness 8
A 0 μm cellulose triacetate film (birefringent layer) was produced. (1) Dope composition

組成 Composition of Cellulose Acetate Solution (Dope) ──── ──────────────────────────────── Cellulose acetate (degree of substitution 2.7) 85 parts by mass Triphenyl phosphate 10 parts by mass Retardation increasing agent used in Example 1 5 parts by mass Methylene chloride 510 parts by mass Methanol 44 parts by mass ────────

(2) Film Forming Method The solution (dope) obtained by the above method was applied to filter paper (No. 24).
After filtering through a filter cloth made by Azumi Filter Paper Co., Ltd.) and flannel, the solution was fed to a pressure die by a fixed-quantity gear pump, and cast using a band casting machine having an effective length of 6 m. The band temperature was 0 ° C. (3) Stretching method The obtained film was stretched under the following conditions.

延伸 Stretching conditions─────────膜 Film forming method Single layer method Residual solvent in film 25% by mass Heat treatment before stretching / Temperature 110 ° C Time 120 Second Stretching magnification 1.10 times Stretching temperature 120 ° C Stretching temperature difference (center-both ends) 5 ° C Stretching speed 10% / min ─────────────────────── ─────────────

The cellulose acetate film (birefringent layer) thus obtained exhibited the following characteristics.

<< Characteristics of Transparent Support Example 3 >> Ｒｅ Re / average value (nm) 70 Fluctuation range (nm) −2 to +3 Rth / average value (nm) 100 Fluctuation range (nm) -3 to +4 Nz 2.2 Axis misalignment (゜) 4 Elongation at break (%) 24２４ ───────────────────

(Preparation of Polarizing Plate) A polarizing plate was prepared in the same manner as in Example 1 except that the obtained cellulose acetate film (birefringent layer) was used.

[Example 4] (Preparation of birefringent layer) A dope having the following composition was prepared, and a dope was cast on a band by the following single layer method by a solution film forming method to form a film. Stretched, width 1m, thickness 6
A 0 μm cellulose triacetate film (birefringent layer) was produced. (1) Dope composition

<< Composition of Cellulose Acetate Solution (Dope) >>セ ル ロ ー ス Cellulose acetate (degree of substitution: 2.9) 85 parts by mass Triphenyl phosphate 10 parts by mass Biphenyl diphenyl phosphate 5 parts by weight Methylene chloride 510 parts by weight Methanol 44 parts by weight The following retardation increasing agent 0.4 parts by weight ─────────────────────── ─────────────

[0083]

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(2) Film Forming Method The solution (dope) obtained by the above method was applied to filter paper (No. 24).
After filtering through a filter cloth made by Azumi Filter Paper Co., Ltd.) and flannel, the solution was fed to a pressure die by a fixed-quantity gear pump, and cast using a band casting machine having an effective length of 6 m. The band temperature was 0 ° C. (3) Stretching method The obtained film was stretched under the following conditions.

────────────────────────────────────Stretching conditions─────────膜 Film forming method Single layer method Residual solvent in film 40% by mass Heat treatment before stretching / Temperature 130 ° C Time 90 Seconds Stretching magnification 1.53 times Stretching temperature 140 ° C Stretching temperature difference (center-both ends) 8 ° C Stretching speed 70% / min 分─────────────

The thus obtained transparent support exhibited the following characteristics.

<< Characteristics of Transparent Support >> Ｒｅ Re / average value (nm) 40 Fluctuation range (nm) -3 to +4 Rth / average Value (nm) 86 Fluctuation range (nm) -4 to +6 Axis shift (゜) 2 Nz 1.7 Break elongation (%) 19 ──────────────────── ────────────────

(Preparation of Polarizing Plate) A polarizing plate was prepared in the same manner as in Example 1 except that the obtained cellulose acetate film (birefringent layer) was used.

Example 5 (Preparation of Birefringent Layer) A dope having the following composition was prepared, and the dope was cast on the band by the following single layer method by a solution film forming method.
Then, the following stretching treatment is performed, and the width is 1 m and the thickness is 120 μm.
Cellulose triacetate film was prepared. (1) Dope composition

<< Composition of Cellulose Acetate Solution (Dope) >>セ ル ロ ー ス Cellulose acetate (degree of substitution: 2.9) 85 parts by mass Triphenyl phosphate 10 parts by mass Biphenyl diphenyl phosphate 5 parts by mass Methylene chloride 510 parts by mass Methanol 44 parts by mass Retardation increasing agent used in Example 1 24 parts by mass ───────────────────── ───────────────

(2) Film Forming Method The solution (dope) obtained by the above method was filtered with filter paper (No. 2).
44, manufactured by Azumi Filter Paper Co., Ltd.) and flannel filter cloth, and then sent to a pressure die by a fixed-quantity gear pump, and cast using a band casting machine having an effective length of 6 m. The band temperature was 0 ° C. (3) Stretching method The obtained film was longitudinally stretched and then stretched in the width direction under the following conditions to produce an optically biaxial cellulose acetate film (birefringent layer).

<< Stretching Conditions Example 5 >> ────────────────────────────── Longitudinal stretching Lateral stretching Residual solvent in the film 38% by mass 8% by mass Heat treatment / temperature before stretching 100 ° C 110 ° C Time 40 seconds 17 seconds Stretch ratio 1.15 times 1.07 times Stretching temperature 140 ° C 148 ° C Stretching temperature difference (center-both ends) 2 ° C 9 ° C Stretching speed 100% / min 20% / min ─────────────────────────────────

The cellulose acetate film (birefringent layer) thus obtained exhibited the following characteristics.

<< Characteristics of Transparent Support >> Ｒｅ Re / average value (nm) 40 Variation range (nm) -3 to +3 Rth / average Value (nm) 46 Fluctuation range (nm) -9 to +7 Nz 3.4 Axis misalignment (゜) 1 Elongation at break (%) 11──────────────────── ────────────────

[Production of Liquid Crystal Display] The production of the liquid crystal display of the present invention will be described in detail below with reference to the drawings. FIG. 2 is an exploded view of the liquid crystal display device corresponding to the first embodiment of the present invention. The liquid crystal cell used in this liquid crystal display has a liquid crystal layer 5 between a lower substrate 4 and an upper substrate 6, and the upper and lower substrates 4 and 6 are parallel and transparent, and are made of, for example, glass. Transparent electrodes 8 and 10 are provided on surfaces of the substrates 4 and 6 facing each other, respectively. The first and second polarizing layers 12 and 14 are orthogonal linear polarizers and are arranged on both sides of a liquid crystal cell constituted by a liquid crystal layer 5 and two substrates 4 and 6. The first polarizing layer 12 is on the substrate 6 side, and the second polarizing layer 14 is on the substrate 4 side. The liquid crystal cell is intended for light to enter from the first polarizing layer 12 and to be observed through the second polarizing layer 14. These two polarizing layers have a plate shape parallel to the substrates 4 and 6. When no voltage is applied between the electrodes, the liquid crystal molecules of the liquid crystal layer 5 are oriented in a direction D, which is called a homeotropic direction and is perpendicular to the substrates 4 and 6.
The axis of weak birefringence (minimum main refractive index) Ne1 of the birefringent layer is parallel to the homeotropic direction. The birefringent layer 16 is disposed between the lower substrate 4 and the second polarizing layer 14, and the polarizing layer 14
And the birefringent layer 16 are adhered to form the polarizing plate of the present invention. As this polarizing plate, the polarizing plate manufactured in the above-described embodiment is used. The liquid crystal layer 5 is made of MERCK to ZLI 1936 (NeCl-N
A liquid crystal layer having a thickness of 5 μm was made of a material sold under the trade name of oCl = 0.19). Table 1 shows viewing angle characteristics of the manufactured liquid crystal display device. The manufactured liquid crystal display device
Used in transmission mode.

Further, an optical reflection layer 18 is added in parallel with the birefringent layer 16 on the side opposite to the birefringent layer 16 with respect to the second polarizing layer 14, and the liquid crystal display device is reflected when viewed through the first polarizing layer 12. It can also be used in mode. Birefringent layer 1
The optimum thickness of 6 actually depends on the thickness of the liquid crystal layer to be used (in direct proportion), and is experimentally determined so that the thickness of the liquid crystal layer is set and the optimum contrast is obtained at a specific observation angle accordingly. . Note that the birefringent layer 16 can be provided between the substrate 6 and the polarizing layer 12 instead of between the substrate 4 and the polarizing layer 14. In this case, the polarizing layer 12 and the birefringent layer 16 form the polarizing plate of the present invention. Further, the birefringent layer 16 has a plurality of layers, and some of the
May be disposed between the substrate 4 and the polarizing layer 14, and the total thickness of those layers may be equal to the thickness of the birefringent layer 16.

FIG. 3 is an exploded view of a liquid crystal display device according to the second embodiment of the present invention. The liquid crystal cell used in this liquid crystal display device has a liquid crystal layer 5 between two glass plates 4 and 6 provided with transparent electrodes 8 and 10. The two polarizing layers 12 and 14 are orthogonal linear polarizers, and are disposed at the same positions as those shown in FIG. The liquid crystal display shown in FIG. 3 has a birefringent layer 20 between the substrate 6 and the polarizing layer 12.
Has a birefringent layer 22 between the substrate 4 and the polarizing layer 14, respectively, and the birefringent layers 20 and 22 are parallel to the substrates 4,6. The optical characteristics of the nematic liquid crystal layer 5 are the same as those in FIG. Each of the birefringent layers 20, 22 has two main refractive indices N1o, N2o, N1o,
It has a third refractive index N3e smaller than N2o and has optical biaxiality. The weak refractive index (minimum main refractive index) axis N3e is parallel to the homeotropic direction. Birefringent layers 20, 2
2 and the polarizing layers 12 and 14 are bonded to each other to form a polarizing plate. The polarizing plate manufactured as described above is used as the polarizing plate. The liquid crystal layer 5 is made of ZLI 1936 (NeCl-N
A liquid crystal layer having a thickness of 4 to 6 μm was made of a material sold under the trade name of oCl = 0.19). Table 1 shows viewing angle characteristics of the manufactured liquid crystal display device. Note that the manufactured liquid crystal display device was used in a transmission mode.

When the liquid crystal display device shown in FIG. 3 is used in the reflection mode, an optical reflection layer 18 is disposed, light is incident on the polarization layer 12, and observation is performed through the polarization layer 12. Further, the liquid crystal display device shown in FIG.
The thicknesses of the birefringent layers 20 and 22 are substantially equal, and Re is 0.1
It is selected to be very close to 25 μm (Condition 1), and this is configured as a quasi-quarter wave delay plate in the visible region. The value of 0.125 μm corresponds to the maximum luminance in the white state corresponding to the application of the excitation voltage to the cell in FIG. The optimal thickness of each of the birefringent layers 20 and 22 (to ensure optimal contrast at a specific viewing angle and a specific liquid crystal cell) is
It can be determined experimentally as a function of the set liquid crystal layer thickness. Between the substrate 6 and the polarizing layer 12 or the substrate 4
It is also possible to use only one birefringent layer located between the polarizing layer 14 and the single birefringent layer in that case,
Birefringent layers 20 and 2 determined as a function of liquid crystal layer thickness
2 to have a thickness equal to the sum of the thicknesses. However, in the embodiment shown in FIG. 3, since the thicknesses of the birefringent layers 20 and 22 are already fixed according to the condition 1, the optimal compensation of the birefringence of the liquid crystal layer requires the optimal extraordinary refractive index N3e for the compensation. It is performed by appropriately adjusting the optical characteristics of the birefringent layers 20 and 22 so as to have.

[Evaluation Test] Using the liquid crystal cell prepared by the above-described method, the viewing angle range in the left-right direction and the up-down direction in which tone inversion does not occur was examined based on the viewing angle characteristics in 8-gradation display. For the bright spot failure, the entire screen was displayed in black, and the number of spots shining like stars in a dark room was counted. The size of each liquid crystal cell is 20 inches. Table 1 shows the evaluation results. The liquid crystal display device of the present invention exhibited a good viewing angle over the entire area of the display screen and was able to suppress the occurrence of a bright spot failure.

[0100]

[Table 1] Table 1: Evaluation of liquid crystal display device ──────────────────────────────────── Birefringence Layer Liquid crystal display device Configuration of FIG. 1 Configuration of FIG. 2 Example 1 Left / right viewing angle (center / edge) (degree) 150/145 160/150 Vertical viewing angle (center / edge) (degree) 85/80 85/85 Brightness Point failure 0 0 Example 2-1 Left and right viewing angle (center / edge) (degree) 155/150 150/145 Vertical viewing angle (center / edge) (degree) 85/80 80/80 Bright point failure 0 0 Example 2-2 Left / right viewing angle (center / edge) (degree) 153/148 158/152 Top / bottom viewing angle (center / edge) (degree) 83/81 84/83 Bright spot failure 0 0 Example 3 Left / right viewing angle (center) (Edge) (degree) 148/145 157/151 Vertical viewing angle (center / edge) (degree) 80/77 83/82 Bright spot failure 0 0 Example 4 Left / right viewing angle (center / edge) (degree) 151 / 146 155/148 Vertical viewing angle (center / edge) (degree) 83/81 84/83 Bright spot failure 0 0 Comparative Example 1 Left / right viewing angle (center / edge) (degree) 115/100 120/100 Vertical viewing angle (degree) (Center / edge) (Degree) 55/35 50/35 Bright spot failure 29 26 Comparative example 2 Left / right Viewing angle (center / edge) (degrees) 105/80 100/70 Vertical viewing angle (center / edge) (degrees) 55/45 50/40 Bright spot failure 56 60 Comparative Example 3 Left / right viewing angle (center / edge) ( (Degree) 122/105 110/93 Vertical viewing angle (center / edge) (degree) 55/43 50/40 Bright spot failure 25 18 ──────────────────── ────────────────

[0101]

[Brief description of the drawings]

FIG. 1 is a partial sectional perspective view of a polarizing plate of the present invention.

FIG. 2 is an exploded view of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is an exploded view of a liquid crystal display device according to a second embodiment of the present invention.

[Description of Signs] 1 polarizing layer 2 adhesive layer 3 birefringent layer 5 liquid crystal layer 4, 6 substrate (transparent glass plate) 8, 10 electrode 12, 14 polarizing layer 16, 20, 22 birefringent layer 18 optical reflecting layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 B29L 7:00 11:00 11:00 F term (Reference) 2H049 BA02 BA25 BA27 BB03 BB12 BB19 BB20 BB33 BB43 BB51 BB63 BB67 BC03 BC14 BC22 2H091 FA08X FA08Z FA11X FA11Z FA14Y FB02 FB12 FC07 FD10 KA10 LA02 LA15 LA17 LA19 LA20 4F210 AA01 AG01 AH73 QG01 QG18

Claims (9)

[Claims] A birefringent layer, which also functions as a transparent protective layer of the polarizing layer, is provided on at least one surface of the polarizing layer. The birefringent layer has a refractive index in the slow axis direction of ns and refraction in a fast axis direction. When the refractive index is nf, the refractive index in the thickness direction is nz, and the layer thickness is d, the in-plane retardation (Re) of the birefringent layer defined by (ns−nf) × d is 0 to 200 nm. , The thickness-direction retardation (Rth) defined by d × [(ns + nf) / 2｝ −nz] is in the range of 0 to 200 nm, and (ns−nz) / (ns−nf) Wherein Nz is 1 or more, and the birefringent layer has an aromatic compound having at least two aromatic rings in an amount of 0.1 to 30.
What is claimed is: 1. A polarizing plate, comprising a cellulose acetate film containing in a range of mass%, wherein the transmission axis of the polarizing layer and the slow axis of the birefringent layer are in a parallel relationship. 2. The cellulose acetate film exhibits optical uniaxiality or optical biaxiality, and the in-plane retardation (Re) varies in any direction along the film surface, and the fluctuation in any direction along the film surface is as follows. The variation of the phase difference (Rth) in the thickness direction in any direction along the film surface is within a range of ± 5 nm with respect to the average value of Re in each direction. The polarizing plate according to claim 1, wherein the value is within a range of ± 10 nm based on the average value of the polarizing plate. 3. The polarizing plate according to claim 2, wherein the cellulose acetate film has been subjected to a stretching treatment, and the breaking elongation in the stretching direction is in the range of 10 to 30%. 4. A liquid crystal display device comprising a liquid crystal cell having one side facing incident light and two polarizing plates disposed on both sides thereof, wherein at least one of the polarizing plates is at least one of the polarizing layers. Is provided with a birefringent layer also serving as a transparent protective layer of the polarizing layer, the refractive index of the birefringent layer in the slow axis direction is ns, the refractive index in the fast axis direction is nf, and the refractive index in the thickness direction is nz, and when the layer thickness is d, the birefringent layer
In-plane phase difference (Re) defined by (ns−nf) × d
Is in the range of 0 to 200 nm, and d × [(ns + n
f) / 2｝ −nz] in the thickness direction (R
th) is in the range of 0 to 200 nm, and (ns−
Nz defined by (nz) / (ns-nf) is 1 or more, and the birefringent layer further contains an aromatic compound having at least two aromatic rings in the range of 0.1 to 30% by mass. And a transmission axis of the polarizing layer and a slow axis of the birefringent layer are in a parallel relationship. 5. The cellulose acetate film exhibits optical uniaxiality or optical biaxiality, and the in-plane retardation (Re) varies in any direction along the film surface. The variation of the phase difference (Rth) in the thickness direction in any direction along the film surface is within a range of ± 5 nm with respect to the average value of Re in each direction. 5. The liquid crystal display device according to claim 4, wherein the value is within a range of ± 10 nm with respect to the average value of. 6. The liquid crystal display device according to claim 5, wherein the cellulose acetate film has been subjected to a stretching treatment, and the elongation at break in the stretching direction is in the range of 10 to 30%. 7. The polarizing plate according to claim 1, wherein the polarizing layer is an orthogonal linear polarizer, and the birefringent layer exhibits optical biaxiality, and the axis of the minimum principal refractive index is parallel to the homeotropic direction. The liquid crystal display device according to claim 4, characterized in that: 8. The product of the absolute value of the difference between the other two main refractive indices of the birefringent layer of the polarizing plate and the thickness of each layer of the birefringent layer is in the range of 90 to 150 nm. Item 8. A liquid crystal display device according to item 7. 9. The liquid crystal according to claim 8, wherein the polarizing plate further has an optical reflection layer, and the optical reflection layer is disposed on a side of the cell opposite to a side facing the incident light. Display device.