JP2002071949A - Optical compensation sheet, polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optically compensate a liquid crystal cell with only a cellulose acetate film. SOLUTION: The optical compensation sheet composed of a sheet of a cellulose acetate film containing cellulose acetate having an acetylation degree within the range of 59.0-61.5%, having an Re retardation value within the range of 20-200 nm, having an Rth retardation value within the range of 70-400 nm and having an absolute value of the maximum curl value within the range of 0-20/m under 25 deg.C temperature and 65% relative humidity surroundings, is used for a 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 an optical compensatory sheet made of cellulose acetate, and a polarizing plate and a liquid crystal display using the same.

[0002]

2. Description of the Related Art Cellulose acetate films are used for various photographic materials and optical materials because of their toughness and flame retardancy. Cellulose acetate film is a typical support for photographic light-sensitive materials. Cellulose acetate films are also used in liquid crystal display devices. Cellulose acetate film is characterized by having higher optical isotropy (lower retardation value) than other polymer films. Therefore, for applications requiring optical isotropy, for example, a polarizing plate, it is common to use a cellulose acetate film. Conversely, the optical compensation sheet of the liquid crystal display device is required to have optical anisotropy (high retardation value). Therefore, it is common to use a synthetic polymer film having a high retardation value, such as a polycarbonate film or a polysulfone film, as the optical compensation sheet.

As described above, in the technical field of optical materials, when a polymer film is required to have optical anisotropy (high retardation value), a synthetic polymer film is used, and optical isotropy (low retardation value) is used. In general, the use of a cellulose acetate film was a general principle when the film thickness was required. European Patent 0911656
A2 discloses a cellulose acetate film having a high retardation value that can be used in applications requiring optical anisotropy, contrary to conventional general principles. It is described that a liquid crystal display device having high display quality can be obtained by inserting the cellulose acetate film between a polarizing plate and a liquid crystal cell.

Further, a λ / 4 plate to which an optical compensation sheet is applied has many uses related to an antireflection film and a liquid crystal display device. However, even if it is referred to as a λ / 4 plate, most achieve λ / 4 at a specific wavelength.
JP-A-5-27118 and JP-A-5-27119 disclose a birefringent film having a large retardation and a birefringent film having a small retardation.
There is disclosed a λ / 4 plate laminated such that their optical axes are orthogonal to each other. If the difference in retardation between the two films is λ / 4 over the entire visible light range, the film theoretically functions as a λ / 4 plate over the entire visible light range.

Japanese Patent Application Laid-Open No. 10-68816 discloses that a polymer film having a wavelength of λ / 4 at a specific wavelength and a polymer film of the same material and having a wavelength of λ / 2 at the same wavelength are laminated to form a wide film. A λ / 4 plate capable of obtaining λ / 4 in the wavelength region is disclosed. JP 1
Japanese Patent Application No. 0-90521 also discloses a λ / 4 plate capable of achieving λ / 4 in a wide wavelength region by laminating two polymer films. As the above polymer film, a stretched film of a synthetic polymer such as polycarbonate has been used.

[0006]

If the above-mentioned optical compensation sheet is used, the liquid crystal cell can be optically compensated to some extent, but there is room for further improving the display quality. In a conventional λ / 4 plate to which an optical compensation sheet is applied, λ / 4 can be achieved in a wide wavelength region by laminating two polymer films. However, for this purpose, it is necessary to laminate two polymer films while strictly adjusting the angle. A λ / 4 plate made of one polymer film has also been proposed. However, there is almost no single film that achieves λ / 4 in a wide wavelength range. Further, it has been found that the viewing angle of the liquid crystal display device is not improved as much as expected even when a λ / 4 plate composed of one polymer film is used in a liquid crystal display device.

[0007] When a cellulose acetate film is used as the optical compensation sheet, the cellulose acetate film may curl and cause various problems. It is considered that the curl is due to the presence of a density distribution, a plasticizer distribution, and a distribution of shrinkage strain generated in the solvent drying step in the thickness direction of the film. Optical compensatory sheets made of cellulose acetate are used in various environments. For example, it may be used under high temperature and high humidity, such as a liquid crystal display mounted on an automobile. Therefore, the cellulose acetate film is required to have a small deformation under various environments, that is, a small curl value. Furthermore, in the step of bonding cellulose acetate to a polarizing plate or in the step of bonding to a polarizing film in order to use it as a protective film of the polarizing plate, a large curl value tends to cause a failure such as air bubbles at the time of bonding. Therefore, the curl value is required to be small.

It is an object of the present invention to provide an optical compensatory sheet comprising only cellulose acetate film, and to optically compensate a liquid crystal cell only with cellulose acetate film. Another object of the present invention is to achieve λ / 4 over a wide wavelength range by using a single sheet of cellulose acetate film. Still another object of the present invention is to add an optical compensation function to a polarizing plate without increasing the number of components of the polarizing plate. Still another object of the present invention is to provide a liquid crystal display optically compensated by a cellulose acetate film. It is still another object of the present invention to provide a polarizing plate with less air bubbles and to provide a liquid crystal display device using the polarizing plate with less display defects.

[0009]

The object of the present invention is attained by the following optical compensation sheets (1) to (3), a polarizing plate (4) and a liquid crystal display device (5) to (7). Was done. (1) A cellulose acetate film containing cellulose acetate having a degree of acetylation in the range of 59.0 to 61.5%, wherein Re is defined by the following formula (I).
The retardation value is in the range of 20 to 200 nm, the Rth retardation value defined by the following formula (II) is in the range of 70 to 400 nm, and the maximum in an environment of a temperature of 25 ° C. and a relative humidity of 65%. An optical compensation sheet, wherein the absolute value of the curl value is in the range of 0 to 20 / m. The retardation value is 5
It is a measured value at 50 nm. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d where nx is the refractive index in the slow axis direction in the film plane; , Is the refractive index in the fast axis direction in the film plane; nz is the refractive index in the film thickness direction; and d is the film thickness. In general, curl is measured in two directions, the width direction and the longitudinal direction. In this specification, the curl value means a larger value of both. (2) The optical compensatory sheet according to (1), wherein at least one surface of the cellulose acetate film is subjected to a process of spraying steam.

(3) The vapor is water, methylene chloride,
The optical compensatory sheet according to (2), which is a vapor obtained by evaporating methyl acetate, acetone, or a mixture thereof. (4) A polarizing plate comprising a polarizing film and two transparent protective films disposed on both sides thereof, wherein one of the transparent protective films contains cellulose acetate having an acetylation degree of 59.0 to 61.5%. It is composed of one sheet of cellulose acetate film and has a Re retardation value defined by the following formula (I) in the range of 20 to 200 nm, and the following formula (II)
And the absolute value of the maximum curl value in an environment of a temperature of 25 ° C. and a relative humidity of 65% is 0.
To 20 / m. The retardation value is a value measured at a wavelength of 550 nm. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d where nx is the refractive index in the slow axis direction in the film plane; , Is the refractive index in the fast axis direction in the film plane; nz is the refractive index in the film thickness direction; and d is the film thickness.

(5) A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein the polarizing plate comprises a polarizing film and two transparent protective films disposed on both sides thereof. One of the two transparent protective films disposed between the liquid crystal cell and the polarizing plate comprises one sheet of cellulose acetate film containing cellulose acetate having an acetylation degree of 59.0 to 61.5%, and has the following formula: The Re retardation value defined by (I) is in the range of 20 to 200 nm, the Rth retardation value defined by the following formula (II) is in the range of 70 to 400 nm, and the temperature is 25 ° C. and the relative humidity is A liquid crystal display device wherein the absolute value of the maximum curl value in an environment of 65% is in the range of 0 to 20 / m. The retardation value is a value measured at a wavelength of 550 nm. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d where nx is the refractive index in the slow axis direction in the film plane; , Is the refractive index in the fast axis direction in the film plane; nz is the refractive index in the film thickness direction; and d is the film thickness. (6) The liquid crystal cell is in VA mode, TN mode, or n-
The liquid crystal display device according to (5), which is an ASM mode liquid crystal cell.

(7) A reflection type liquid crystal display device in which a reflection plate, a liquid crystal cell and a polarizing film are laminated in this order, wherein the degree of acetylation is 59.0 to 61.5% between the reflection plate and the polarizing film. A cellulose acetate film containing cellulose acetate is disposed, and the cellulose acetate film has a Re retardation value defined by the following formula (I) in the range of 20 to 200 nm, and is defined by the following formula (II). Rth retardation value is 7
0-400 nm and at a temperature of 25 ° C.
A reflective liquid crystal display device, wherein the absolute value of the maximum curl value in an environment of a relative humidity of 65% is in the range of 0 to 20 / m. The retardation value is 550n.
It is a measured value in m. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d where nx is the refractive index in the slow axis direction in the film plane; , Is the refractive index in the fast axis direction in the film plane; nz is the refractive index in the film thickness direction; and d is the film thickness.

[0013]

The inventor of the present invention has disclosed in European Patent 0911656A.
By improving the cellulose acetate film disclosed in the specification of JP-A No. 2, the inventors succeeded in optically compensating the liquid crystal cell using only the film. By adjusting the type and amount of the additive (specifically, an aromatic compound having two aromatic rings) to the cellulose acetate film or the production conditions (for example, film stretching conditions), the wavelength of 550 is adjusted.
Re retardation value in nm of 20 to 200 nm
And the Rth retardation value is 70 to 400 n
m is obtained. This cellulose acetate film has sufficient optical anisotropy to optically compensate the liquid crystal cell. Therefore, an optical compensatory sheet consisting of only one cellulose acetate film can be obtained.

By adjusting the material and manufacturing method of the cellulose acetate film, an optical compensatory sheet (λ / 4 plate) capable of achieving λ / 4 in a wide wavelength range was successfully provided. Further, the optical compensation sheet (λ /
(4) is attached to a liquid crystal display device for use, thereby significantly improving the viewing angle. An optical compensatory sheet (λ / 4 plate) capable of achieving λ / 4 in a wide wavelength range using a single cellulose acetate film has been obtained, so that the angle of two conventional polymer films can be strictly adjusted. The step of stacking is no longer required.

The protective film of the polarizing plate generally comprises a cellulose acetate film. When the above-mentioned cellulose acetate film is used as one protective film of the polarizing plate, an optical compensation function can be added to the polarizing plate without increasing the number of components of the polarizing plate. By adjusting the curl value of the optical compensation sheet, it is possible to prevent air bubbles from being mixed into the polarizing plate and to obtain a polarizing plate with few defects. In addition,
When a cellulose acetate film having an acetylation degree of less than 59.0 is used, the above optical anisotropy can be easily achieved, but the physical properties of the cellulose acetate film deteriorate. In the present invention, a cellulose acetate film having a degree of acetylation of 59.0 to 61.5% is used, and the above-mentioned retardation value is achieved by other means (adjustment of the above additives and production conditions). Thus, a cellulose acetate film having both excellent optical anisotropy and physical properties has been obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Retardation of Film]
The Re retardation value and Rth retardation value of the film 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 this specification, a retardation value not particularly described is a wavelength of 550.
Means measurements in nm.

In the present invention, the cellulose acetate film has a Re retardation value of 20 to 200 nm.
Then, the Rth retardation value is set to 70 to 400 nm.
Adjust to. Further, it is more preferable to adjust the Re retardation value to 20 to 70 nm and the Rth retardation value to 70 to 400 nm. When two optically anisotropic cellulose acetate films are used in a liquid crystal display device, the Rth retardation value of the film is preferably from 70 to 200 nm. When one optically anisotropic cellulose acetate film is used for a liquid crystal display device, the Rth retardation value of the film is preferably 150 to 400 nm.

When the optical compensation sheet is used as a λ / 4 plate, the Re retardation value (Re450) measured at a wavelength of 450 nm is 100 to 125 nm, and the Re retardation value (Re590) measured at a wavelength of 590 nm. It is preferably from 120 to 160 nm, and the relationship of Re590-Re450 ≧ 2 nm is preferably satisfied. More preferably, Re590-Re450 ≧ 5 nm, and Re590-Re450 ≧ 1.
Most preferably, it is 0 nm.

[Curl value] The curl value is determined by a measurement method (ANSI / ASCPH1.2) specified by the American National Standards Institute.
9-1985, Method-A). Polymer film 35mm in width direction, 2m in longitudinal direction
After being cut to the size of m, it is set on a curl plate. The curl value is read after controlling the humidity for 1 hour in an environment at a temperature of 25 ° C. and a relative humidity of 65%. Then, similarly, the polymer film is cut into a size of 2 mm in the width direction and 35 mm in the longitudinal direction, and then placed on a curl plate. This is at 25 ° C,
The curl value is read after humidity control for 1 hour in an environment with a relative humidity of 65%. In general, curl is measured in two directions, the width direction and the longitudinal direction. In this specification, the curl value means a larger value of both. The curl value is represented by the reciprocal of the radius of curvature (m). The curl of which the surface in contact with the support (drum or band, etc.) at the time of casting the film is inwardly wound is indicated by + (plus), and the curl which is outwardly wound is indicated by-(minus). The absolute value of the curl value of the polymer film is 0 to 2
It is preferably in the range of 0 / m, and more preferably in the range of 0 to 15 / m. An optical compensatory sheet having the above properties or a λ / 4 plate to which the optical compensatory sheet is applied can be manufactured by the following materials and methods.

[Cellulose Acetate] In the present invention, cellulose acetate having an acetylation degree of 59.0 to 61.5% is used. The acetylation degree means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is ASTM: D-
The measurement and calculation of the degree of acetylation in 817-91 (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,
Mw / by gel permeation chromatography
It is preferable that the molecular weight distribution of Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) is narrow. Specific Mw / Mn
Is preferably from 1.0 to 1.7, more preferably from 1.3 to 1.65,
Most preferably, it is 1.4 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 is used as a retardation increasing agent. The aromatic compound is
0.01 parts by mass relative to 100 parts by mass of cellulose acetate
It is used in the range of 20 to 20 parts by mass. The aromatic compound is preferably used in an amount of 0.05 to 15 parts by mass with respect to 100 parts by mass of cellulose acetate.
More preferably, it is used in the range of 10 to 10 parts by mass. Two or more aromatic compounds may be used in combination. In the aromatic ring of the aromatic compound, in addition to the aromatic hydrocarbon ring,
Including aromatic heterocycle.

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,
Phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxatiin ring, phenoxazine ring and thianthrene ring are 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. 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-OC
O-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.

[Infrared absorber] An infrared absorber can be added to the polymer film in order to adjust the retardation value at each wavelength. The infrared absorber is preferably used in an amount of 0.01 to 5 parts by weight, more preferably 0.02 to 2 parts by weight, and more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the polymer. It is more preferably used in the range of 1 part by weight, and most preferably used in the range of 0.1 to 0.5 part by weight.
Two or more infrared absorbers may be used in combination. The infrared absorber preferably has a maximum absorption in a wavelength range of 750 to 1100 nm, and more preferably has a maximum absorption in a wavelength range of 800 to 1000 nm. It is preferred that the infrared absorber has substantially no absorption in the visible region.

It is preferable to use an infrared absorbing dye or an infrared absorbing pigment as the infrared absorbing agent, and it is particularly preferable to use an infrared absorbing dye. The infrared absorbing dye includes an organic compound and an inorganic compound. It is preferable to use an infrared absorbing dye which is an organic compound. Organic infrared absorbing dyes include cyanine compounds, metal chelate compounds, aminium compounds, diimonium compounds, quinone compounds, squarylium compounds and methine compounds. For the infrared absorbing dye, coloring material, 61 [4] 2
15-226 (1988), and Chemical Industry, 43-5.
3 (1986, May).

When examining the types of dyes from the viewpoint of infrared absorption function or absorption spectrum, infrared absorption dyes developed in the technical field of silver halide photographic materials are excellent. Infrared absorbing dyes developed in the technical field of silver halide photographic light-sensitive materials include dihydroperimidine squarylium dyes (described in US Pat. No. 5,380,635 and Japanese Patent Application No. 8-189817) and cyanine dyes (JP-A No. No. 62-123454, No. 3-138640, No. 3
-21542, 3-226736, 5-31
Nos. 3305 and 6-43583, Japanese Patent Application No. 7-435.
269097 and EP 0430244), pyrylium dyes (JP-A-3-13864).
Nos. 0 and 3-21542) and diimmonium dyes (JP-A-3-138640 and JP-A-3-2115).
No. 42), pyrazolopyridone dyes (described in JP-A-2-282244), indoaniline dyes (described in JP-A-5-323500 and JP-A-5-323501), polymethine dyes (described in JP-A-3-26765). Nos. 4,190,343 and EP 37796.
No. 1), oxonol dyes (JP-A-3-93)
No. 46), anthraquinone dyes (Japanese Unexamined Patent Publication No.
13654), a naphthalocyanine dye (described in US Pat. No. 5,099,899) and a naphtholactam dye (described in European Patent 568,267).

[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 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 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 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 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, 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 dissolution 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 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, 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. It is preferable to add the above-mentioned retardation increasing agent to the dope. The dope is cast on a drum or band and the solvent is evaporated to form a film. The dope before casting has a solid content of 1
It is preferable to adjust the concentration so as to be 8 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 US Pat. No. 2,336,310.
No. 2367603, No. 2492078, No. 24
No. 92977, No. 2492978, No. 2607704
Nos. 2739069 and 2739070, British Patent Nos. 640731 and 736892, JP-B-45-4554, JP-A-49-5614, and JP-A-6060.
-176834, 60-203430, 62-
It is described in each publication of No. 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.

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 include phthalic esters and citric esters. Examples of phthalate esters include dimethyl phthalate (DM
P), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include O-acetyl triethyl citrate (OACT
E) and tributyl O-acetylcitrate (OACT
B) is included. Examples of other carboxylic esters include butyl oleate, methylacetyl ricinoleate,
It includes dibutyl sebacate and various trimellitate esters. Phthalate ester plasticizers (DMP, DE
P, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The amount of the plasticizer added is 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.

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
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 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 retardation of the cellulose acetate film can be adjusted by a stretching treatment. The stretching ratio is preferably 3 to 100%. The thickness of the cellulose acetate film is preferably 40 to 140 μm, more preferably 70 to 120 μm.
Is more preferable.

[Curl Control Treatment of Cellulose Ester Film] A desired curl value can be obtained by spraying steam on the surface of the cellulose ester film to be curled. Specifically, steam may be sprayed on the outer surface of the generated curl. The sprayed steam is preferably water, methylene chloride, methyl acetate, acetone, or steam obtained by evaporating a mixture thereof. When steam is used as the steam, the temperature of the steam is preferably in the range of 100 to 150 ° C.
An example of a preferred vapor is a vapor in which the main components of the vapor are methylene chloride and methyl acetate.
In this case, it is more preferable that the sum of methylene chloride and methyl acetate is in the range of 100 to 50% by mass, and more preferably in the range of 0 to 50% by mass of acetone, based on the entire vapor.

[Polarizing Plate] The polarizing plate comprises a polarizing film and two transparent protective films disposed on both sides thereof. As one protective film, the above-mentioned cellulose acetate film can be used. For the other protective film, a normal cellulose acetate film may be used. The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. The cellulose acetate film is disposed so that the slow axis of the cellulose acetate film and the transmission axis of the polarizing film are substantially parallel to each other.
When a cellulose acetate film is used as a λ / 4 plate, the film is arranged so that the angle between the slow axis in the plane of the λ / 4 plate and the transmission axis of the polarizing film is substantially 45 °.
Substantially 45 ° means 40 to 50 °. The angle between the slow axis in the plane of the λ / 4 plate and the transmission axis of the polarizing film is preferably 41 to 49 °, more preferably 42 to 48 °, and 43 to 47 °. Is more preferable, and most preferably 44 to 46 °. A circularly polarizing plate can be formed by arranging such that the angle between the in-plane slow axis of the λ / 4 plate and the transmission axis of the polarizing film is substantially 45 °.

[Use of λ / 4 Plate] A λ / 4 plate or a circularly polarizing plate can be used as a λ / 4 plate used in a writing pickup of an optical disk or as an antireflection film. In various display devices, a λ / 4 plate or a circularly polarizing plate can be used. A display device that can use a λ / 4 plate or a circularly polarizing plate includes a cathode ray tube (CR
T), a plasma display panel (PDP), a field emission display (FED), an inorganic EL device, an organic EL device, and a liquid crystal display device. By using a λ / 4 plate or a circularly polarizing plate according to the present invention,
Reflection of external light on the display surface can be reduced. In a liquid crystal display device, a retardation plate can be used for optical compensation. A λ / 4 plate or a circularly polarizing plate can be advantageously used in a liquid crystal display device, particularly in a reflection type liquid crystal display device.

[Liquid crystal display device] An optical compensation sheet comprising the above-mentioned cellulose acetate film or a polarizing plate using the above-mentioned cellulose acetate film is preferably used for a liquid crystal display device. An appropriate value is determined for the retardation of the optically anisotropic cellulose acetate film (optical compensation sheet) depending on the characteristics of the liquid crystal display device. [Transmissive liquid crystal display device] The transmissive liquid crystal display device is composed of a liquid crystal cell and two polarizing plates disposed on both sides thereof.
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 compensating sheets are provided between the liquid crystal cell and both of the polarizing plates. When two cellulose acetate films are used, the Rth retardation of the film is preferably 70 to 200 nm. When one sheet of cellulose acetate film is used, the Rth retardation value of the film is 150 to 400.
It is preferably nm. In a polarizing plate, the above-mentioned cellulose acetate film is used as a transparent protective film disposed between a liquid crystal cell and a polarizing film. Either the above-mentioned cellulose acetate film is used only for the transparent protective film (between the liquid crystal cell and the polarizing film) of one polarizing plate, or two transparent films (between the liquid crystal cell and the polarizing film) of both polarizing plates are used. The above-mentioned cellulose acetate film is used for the protective film. The liquid crystal cell is preferably in a VA mode or a TN mode.

In a VA mode liquid crystal cell, rod-like liquid crystal molecules are oriented substantially vertically when no voltage is applied. VA
The liquid crystal cell of the mode includes (1) a VA mode liquid crystal cell in a narrow sense in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. 2-176625). And JP-B-7-69536), and (2) a liquid crystal cell in which the VA mode is multi-domain for expanding the viewing angle. Specifically, MVA (SID97, Digest of tech. Papers (Preliminary Collection) 28 (1997) 845, SID99, Digest o
f tech. Papers (Preliminary Collection) 30 (1999) 206 and JP-A-11-258605), SURVAI
VAL (Monthly Display, Vol. 6, No. 3 (199
9) 14)), PVA (Asia Display 9)
^{8, Proc.of the 18 th Inter.} Display res. Conf. ( Proceedings) (1998) 383 described), Para-A (LCD /
PDP International'99)
DDVA (SID98, described in Digest of tech. Papers (Preliminary Collection) 29 (1998) 838), EOC (SID9
8. Digest of tech. Papers 29 (199)
8) 319), PSHA (SID98, Digest of
tech. Papers (preliminary collection) 29 (1998) 1081), RFFMH (Asia Display 98, Pro
^{c.of the 18 th Inter. Display res} . Conf. ( Proceedings)
(1998) 375), HMD (SID98, Dige)
st of tech. Papers 29 (1998) 702
Description) is included. Other (3) rod-like liquid crystal molecules are oriented substantially vertically when no voltage is applied, the liquid crystal cell of mode in the twisted multi-domain alignment when voltage is applied (n-ASM mode) (IWD'98, Proc.of ^the 5 ^th Int
er. Display Workshop. (Preprints) (1998) 143))).

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

[Reflective Liquid Crystal Display Element] FIG. 1 is a schematic diagram showing a basic configuration of a reflective liquid crystal display device. The reflective liquid crystal display device shown in FIG. 1 includes, in order from the bottom, a lower substrate (1), a reflective electrode (2), a lower alignment film (3), a liquid crystal layer (4), an upper alignment film (5), and a transparent electrode ( 6), an upper substrate (7), a λ / 4 plate (8), and a polarizing film (9). The lower substrate (1) and the reflection electrode (2) constitute a reflection plate. The lower alignment film (3) to the upper alignment film (5) constitute a liquid crystal cell. The λ / 4 plate (8) can be arranged at an arbitrary position between the reflection plate and the polarizing film (9). In the case of color display, a color filter layer is further provided. The color filter layer is preferably provided between the reflective electrode (2) and the lower alignment film (3) or between the upper alignment film (5) and the transparent electrode (6). A reflective plate may be separately attached using a transparent electrode instead of the reflective electrode (2) shown in FIG. A metal plate is preferable as the reflector used in combination with the transparent electrode. If the surface of the reflector is smooth, only the specular reflection component may be reflected and the viewing angle may be narrowed. Therefore, it is preferable to introduce an uneven structure (described in Japanese Patent No. 275620) on the surface of the reflector. When the surface of the reflection plate is flat (instead of introducing an uneven structure on the surface), a light diffusion film may be attached to one side (cell side or outside) of the polarizing film.

The liquid crystal cell is TN (Twisted Ne).
magnetic) type, STN (Super Twist)
ed Nematic) type or HAN (Hybrid)
(Aligned Nematic) type is preferable. The twist angle of the TN type liquid crystal cell is 40 to 10
It is preferably 0 °, more preferably 50 to 90 °, and most preferably 60 to 80 °. The value of the product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is 0.1 to 0.5 · μ.
m, more preferably 0.2 to 0.4 μm. The twist angle of the STN type liquid crystal cell is
It is preferably 180 to 360 °, more preferably 220 to 270 °. The product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer
Is preferably 0.3 to 1.2 μm,
More preferably, it is 0.5 to 1.0 μm. HA
In the N-type liquid crystal cell, it is preferable that the liquid crystal is substantially vertically aligned on one substrate and the pretilt angle on the other substrate is 0 to 45 °. The value of the product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.1 to 1.0 μm, and 0.3
More preferably, the thickness is from 0.8 to 0.8 μm. The substrate on which the liquid crystal is vertically aligned may be a substrate on the reflection plate side or a substrate on the transparent electrode side. The reflection type liquid crystal display device can be used in a normally white mode in which the display is bright when the applied voltage is low and a dark display when the applied voltage is high, or in a normally black mode in which the display is dark when the applied voltage is low and bright when the applied voltage is high. . Normally white mode is preferred.

[Guest-host reflective liquid crystal display device] FIG.
FIG. 1 is a schematic cross-sectional view showing a typical mode of a guest-host reflection type liquid crystal display element. The guest-host reflection type liquid crystal display device shown in FIG. 2 includes a lower substrate (11), an organic interlayer insulating film (1).
2), metal reflector (13), λ / 4 plate (14), lower transparent electrode (15), lower alignment film (16), liquid crystal layer (17), upper alignment film (18), upper transparent electrode (19) ), Light diffusion plate (2
0), an upper substrate (21) and an antireflection layer (22) are laminated in this order. The lower substrate (11) and the upper substrate (21) are made of a glass plate or a plastic film. Lower substrate (11) and organic interlayer insulating film (12)
A TFT (23) is attached between the two. The liquid crystal layer (17) is composed of a mixture of a liquid crystal and a dichroic dye. The liquid crystal layer is obtained by injecting a mixture of liquid crystal and a dichroic dye into the cell gap formed by the spacer (24). Instead of providing the light diffusion plate (20), the metal reflection plate (13) may have a light diffusion function by making the surface of the metal reflection plate (13) uneven. The antireflection layer (22) preferably has an antiglare function in addition to the antireflection function.

FIG. 3 is a schematic sectional view showing another typical embodiment of the guest-host reflection type liquid crystal display device. The guest-host reflection type liquid crystal display device shown in FIG.
1), organic interlayer insulating film (32), cholesteric color reflector (33), λ / 4 plate (34), lower transparent electrode (3)
5) A structure in which a lower alignment film (36), a liquid crystal layer (37), an upper alignment film (38), an upper transparent electrode (39), an upper substrate (41), and an antireflection layer (42) are laminated in this order. Having. The lower substrate (31) and the upper substrate (41) are made of a glass plate or a plastic film. Lower substrate (31)
A TFT (43) is provided between the TFT and the organic interlayer insulating film (32).
Is attached. The λ / 4 plate (34) may also function as a light diffusion plate. The liquid crystal layer (37) is composed of a mixture of a liquid crystal and a dichroic dye. The liquid crystal layer is obtained by injecting a mixture of liquid crystal and a dichroic dye into the cell gap formed by the spacer (44). A black matrix (45) is attached between the upper transparent electrode (39) and the upper substrate (41). Anti-reflection layer (4
2) preferably has an antiglare function in addition to the antireflection function.

The λ / 4 plate according to the present invention includes the λ / 4 plate (8) of the reflection type liquid crystal display device described with reference to FIG. 1, and FIG.
And it can be used as the λ / 4 plates (24) and (34) of the guest-host reflection type liquid crystal display device described in FIG.
Japanese Patent Application Laid-Open Nos. 6-222350 and 8-36174 disclose a guest-host reflection type liquid crystal display device having a λ / 4 plate.
No., No. 10-268300, No. 10-292175
No. 10-293301, No. 10-319776
Nos. 10-319442 and 10-325595
And JP-A-10-333138 and JP-A-11-38410. The λ / 4 plate according to the present invention can also be used for the guest-host reflection type liquid crystal display device described in each of the above publications.

[0056]

EXAMPLES (Measurement of Optical Properties) The prepared polymer film (optical compensation sheet) was measured using an ellipsometer (M
-150, manufactured by JASCO Corporation, at a wavelength of 450 n.
The retardation (Re) value and the Rth retardation at m, 550 nm and 590 nm were measured.

Example 1 (Preparation of Optical Compensation Sheet) The following composition was charged into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

<< Composition of Cellulose Acetate Solution >>セ ル ロ ー ス 100% by mass of cellulose acetate having a degree of acetylation of 60.9% triphenyl phosphate (plasticizer) 7 0.8 parts by mass Biphenyldiphenyl phosphate (plasticizer) 3.9 parts by mass Methylene chloride (first solvent) 300 parts by mass Methanol (second solvent) 54 parts by mass 1-butanol (third solvent) 11 parts by mass ────────────────────────────────

To another mixing tank, 16 parts by mass of the following retardation increasing agent, 80 parts by mass of methylene chloride and 20 parts by mass of methanol were added, and the mixture was stirred while heating to prepare a solution of the retardation increasing agent.
474 parts by mass of the cellulose acetate solution was mixed with 25 parts by mass of the retardation increasing agent solution, and the mixture was sufficiently stirred to prepare a dope. The addition amount of the retardation enhancer
It was 3.5 parts by mass with respect to 100 parts by mass of cellulose acetate.

[0060]

Embedded image

The obtained dope was cast using a band casting machine. A film having a residual solvent amount of 15% by mass
The film was transversely stretched at a stretching ratio of 25% using a tenter under the condition of 0 ° C., kept at 50 ° C. for 30 seconds while maintaining the stretched width, and then the clip was removed to produce a cellulose acetate film. The film thickness of the obtained film was 80 μm. Further, -curl occurred in the obtained polymer film. Water vapor at 125 ° C. was sprayed on the outer surface of the generated curl. The film temperature at this time is 90 ° C
The amount of steam to be sprayed was 5 kg / hour, and the spray time was 5 seconds. The optical characteristics and curl of the obtained polymer film (optical compensation sheet) TAC-1 were measured. The results are shown in Table 1.

Example 2 (Preparation of Optical Compensation Sheet) A cellulose acetate film was prepared in the same manner as in Example 1. Methylene chloride gas was used as the steam to be blown, and the temperature of the film was 40 ° C.
A curl control process was performed in the same manner as in Example 1 except that the amount of steam to be sprayed was 5 kg / hour and the spraying time was 5 seconds, to produce an optical compensation sheet. Optical characteristics and curl of the obtained polymer film (optical compensation sheet) TAC-2 were measured. The results are shown in Table 1.

Comparative Example 1 (Preparation of Optical Compensation Sheet) In the same manner as in Example 1, a cellulose acetate film was prepared. No curl control treatment was performed. The optical properties and curl of the obtained polymer film (optical compensation sheet) TAC-3 were measured. The results are shown in Table 1.

[0064]

[Table 1] Table 1 Film Re Rth Curl value (Measurement wavelength: 550 nm) 25 ° C., 65% RH──────────────────────────────────── Example 1 40 nm 130 nm-5 Example 2 40 nm 130 nm-4 Comparative Example 1 40 nm 130 nm-23 ────

Example 3 (Preparation of Polarizing Plate) A polarizing film was prepared by adsorbing iodine on a stretched polyvinyl alcohol film. The cellulose acetate film TAC-1 produced in Example 1 was saponified, and a polyvinyl alcohol-based adhesive was used.
Affixed to one side of the polarizing film. TAC-1 and the polarizing film were adhered so that the longitudinal direction became parallel, and the angle between the average direction of the slow axis of TAC-1 and the transmission axis of the polarizing film was 0 °. Commercially available cellulose triacetate film (Fujitac T
D80UF (manufactured by Fuji Photo Film Co., Ltd.) was saponified and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. Thus, a polarizing plate was produced.

Example 4 A polarizing plate was produced in the same manner as in Example 3 except that the cellulose acetate film TAC-2 produced in Example 2 was used.

Comparative Example 2 A polarizing plate was produced in the same manner as in Example 3 except that the cellulose acetate film TAC-3 produced in Comparative Example 1 was used.

[Evaluation of Polarizing Plate] (Confirmation of Bubbles in Polarizing Plate) Examples 3 and 4 and Comparative Example 2
The presence or absence of bubbles in the polarizing plate was visually inspected for the polarizing plate prepared in the above. The results are shown in Table 2. (Evaluation of durability of polarizing plate) The polarizing plates prepared in Examples 3 and 4 and Comparative Example 2 were adhered to a glass plate using an acrylic adhesive, aged at a constant temperature and under pressure, and then heated at a constant temperature of 90 ° C. And left for 1000 hours. Then, the presence / absence of peeling of the optical compensation sheet and the polarizing film and the presence / absence of bubbles were visually examined. The results are shown in Table 2.

[0069]

[Table 2] Table 2 ──────────────────────────────────── Polarizing plate Bubbles in the polarizing plate Endurance evaluation Peeling bubbles ──────────────────────────────────── Example 3 None None None Example 4 No No No Comparative Example 2 Yes Yes Yes ────────────────────────────────────

(Evaluation of Viewing Angle by Mounting on Vertical Alignment Type Liquid Crystal Cell) A pair of polarizing plates and a pair of polarizing plates provided in a liquid crystal display device (VL-1530S, manufactured by Fujitsu Limited) using the vertical alignment type liquid crystal cell. Peel off the optical compensation sheet of
Instead, the polarizing plates produced in Examples 3 and 4 and Comparative Example 2 were adhered one by one to the viewer side and the backlight side via an adhesive so that the optical compensation sheet was on the liquid crystal cell side. The crossed Nicols arrangement was such that the transmission axis of the polarizing plate on the viewer side was in the vertical direction, and the transmission axis of the polarizing plate on the backlight side was in the horizontal direction. For the manufactured liquid crystal display device, use a measuring device (EZ-Contrast 160D, ELD
(Manufactured by IM Co., Ltd.). Table 3 shows the results in the viewing angle region where the contrast is 10 and there is no gradation inversion. (Evaluation of viewing angle by mounting on TN type liquid crystal cell) A pair of polarizing plates provided in a liquid crystal display device (6E-A3, manufactured by Sharp Corporation) using the TN type liquid crystal cell was peeled off, and the example was replaced with an example. The polarizing plates prepared in 3, 4 and Comparative Example 2 were adhered one by one to the observer side and the backlight side via an adhesive so that the optical compensation sheet was on the liquid crystal cell side. The crossed Nicols arrangement was such that the transmission axis of the polarizing plate on the viewer side was in the vertical direction, and the transmission axis of the polarizing plate on the backlight side was in the horizontal direction. For the manufactured liquid crystal display device, use a measuring device (EZ-Contrast 160D, ELD
(Manufactured by IM Co., Ltd.). Table 3 shows the results in the viewing angle region where the contrast is 10 and there is no gradation inversion.

[0071]

Table 3 ────────────────────────────────────Polarizing plate vertical alignment type liquid crystal cell Viewing angle of TN type liquid crystal cell Viewing angle up / down left / right up / down left / right ──────────────────────────────────── Example 3> 160 °> 160 ° 45 ° 160 ° Example 4> 160 °> 160 ° 45 ° 160 ° Comparative Example 2> 160 °> 160 ° 45 ° 160 ° 比較─────────────────────────

Example 5 (Preparation of Optical Compensation Sheet) A cellulose acetate solution (dope) having the following composition was prepared.

<< Composition of Cellulose Acetate Solution >>セ ル ロ ー ス Cellulose acetate having a degree of acetylation of 59.7% 117.87 parts by mass Retardation of Example 1 Raising agent 1.18 parts by mass Triphenyl phosphate (plasticizer) 9.19 parts by mass Biphenyldiphenyl phosphate (plasticizer) 4.60 parts by mass Tribenzylamine 2.36 parts by mass Methylene chloride (first solvent) 609.37 parts by mass Parts methanol (second solvent) 53.00 parts by mass 1-butanol (third solvent) 11 parts by mass ─────────

The obtained dope was cast on a glass plate,
After drying at room temperature for 1 minute, it was dried at 45 ° C. for 5 minutes. The residual solvent amount after drying was 25% by mass. The cellulose acetate film was peeled off from the glass plate,
After drying for 120 minutes, it was dried at 120 ° C. for 20 minutes. The amount of residual solvent after drying was 2.1%. After the dried film was cut into an appropriate size, it was stretched at 130 ° C. by 1.4 times in a direction parallel to the casting direction. The direction perpendicular to the stretching direction was allowed to shrink freely. After stretching, the film was taken out in an atmosphere at room temperature and cooled. The film thickness of the obtained film was 102 μm. The residual amount of the solvent was 0.1% by mass. Further, 125 ° C. was applied to the outer surface of the curl generated in the obtained polymer film.
Of water vapor was sprayed. The film temperature at this time is 9
At 0 ° C., the amount of steam sprayed was 5 kg / hour, and the time of spraying was 5 seconds. The optical properties and curl of the obtained polymer film (optical compensation sheet) TAC-4 were measured. The results are shown in Table 4.

Example 6 (Preparation of Optical Compensation Sheet) Example 1 was repeated except that methylene chloride gas was used as the vapor to be sprayed, the temperature of the film was 40 ° C., the amount of steam to be sprayed was 5 kg / hour, and the spray time was 5 seconds. In the same manner as in 5, a polymer film was produced. Obtained polymer film (optical compensation sheet) T
For AC-5, the optical characteristics and curl were measured. The results are shown in Table 4.

Comparative Example 3 (Preparation of Optical Compensation Sheet) A polymer film was prepared in the same manner as in the preparation of Example 5 except that the spraying of steam was not performed. The optical properties and curl of the obtained polymer film (optical compensation sheet) TAC-6 were measured. The results are shown in Table 4.

[0077]

TABLE 4 Optical Compensation Re Rth Curl Value Sheet 450 nm 550 nm 550 nm 25 ° C., 65% RH {Example 5 116 nm 137 nm 137 nm-7 Example 6 116 nm 137 nm 137 nm-5 Comparative Example 3 116 nm 137 nm 137 nm-25 ─────

Example 7 (Preparation of Circular Polarizing Plate) A polarizing film was prepared by adsorbing iodine on stretched polyvinyl alcohol. The cellulose acetate film (TAC-4) produced in Example 5 was saponified and attached to one side of a polarizing film using a polyvinyl alcohol-based adhesive. The angle between the slow axis and the polarization axis of TAC-4 was adjusted to 45 °. A commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was saponified and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. Thus, a circularly polarizing plate of Example 3 was produced. When the optical properties of the obtained circularly polarizing plates were examined, almost perfect circularly polarized light was achieved in a wide wavelength range (450 to 590 nm).

Example 8 (Production of Circularly Polarizing Plate) A circularly polarizing plate was produced in the same manner as in Example 7 except that the cellulose acetate film (TAC-5) produced in Example 6 was used. When the optical properties of the obtained circularly polarizing plates were examined, almost perfect circularly polarized light was achieved in a wide wavelength range (450 to 590 nm).

Comparative Example 4 (Production of Circularly Polarizing Plate) A circularly polarizing plate was produced in the same manner as in Example 7, except that the cellulose acetate film (TAC-6) produced in Comparative Example 3 was used.

(Evaluation of Circularly Polarizing Plate) (1) Confirmation of Bubbles in Circularly Polarizing Plate The circularly polarizing plates produced in Examples 7 and 8 and Comparative Example 4 were visually inspected for the presence of bubbles in the circularly polarizing plate. Was. The results are shown in Table 5. (2) Evaluation of Durability of Circularly Polarizing Plate The circularly polarizing plates produced in Examples 7 and 8 and Comparative Example 4 were adhered to a glass plate using an acrylic adhesive, and after aging under high temperature and pressure, 90%. Place in a thermostat at
Left for 00 hours. Then, the presence / absence of peeling of the optical compensation sheet and the polarizing film and the presence / absence of bubbles were visually examined. The results are shown in Table 5. (3) Evaluation of Viewing Angle by Mounting The circularly polarizing plates prepared in Examples 7 and 8 and Comparative Example 4 were mounted on a reflection-type liquid crystal panel, and were measured using a measuring instrument (EZ Contrast 160D, E
(Manufactured by LDIM) was used to measure the viewing angle characteristics. Table 5 shows the results in the viewing angle region of contrast 3.

[0082]

[Table 5] Table 5 ──────────────────────────────────── circularly polarizing plate circularly polarizing plate in Evaluation of bubble durability at a viewing angle Peeling bubble Up, down, left, right ──────────────────────────────────── Example 7 No No No 131 ゜ 121 ゜ Example 8 No No No 131 ゜ 121 ゜ Comparative Example 4 Yes Yes Yes 131 ゜ 120 ゜ ─────────────────────── ─────────────

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a reflective liquid crystal display device.

FIG. 2 is a schematic cross-sectional view showing a typical mode of a guest-host reflection type liquid crystal display element.

FIG. 3 is a schematic cross-sectional view showing another typical embodiment of a guest-host reflection type liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 lower substrate 2 reflective electrode 3 lower alignment film 4 liquid crystal layer 5 upper alignment film 6 transparent electrode 7 upper substrate 8 λ / 4 plate 9 polarizing film 11 lower substrate 12 organic interlayer insulating film 13 metal reflector 14 λ / 4 plate 15 lower Transparent electrode 16 Lower alignment film 17 Liquid crystal layer 18 Upper alignment film 19 Upper transparent electrode 20 Light diffusing plate 21 Upper substrate 22 Antireflection layer 23 TFT 24 Spacer 31 Lower substrate 32 Organic interlayer insulating film 33 Cholesteric color reflector 34 λ / 4 plate 35 lower transparent electrode 36 lower alignment film 37 liquid crystal layer 38 upper alignment film 39 upper transparent electrode 41 upper substrate 42 antireflection layer 44 spacer 45 black matrix

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08L 1:10 C08L 1:10 F-term (Reference) 2H049 BA02 BA03 BA07 BA26 BA27 BB03 BB33 BB43 BB51 BB62 BC02 BC14 BC22 2H091 FA08X FA08Z FA11X FA14Z FB02 HA07 HA10 HA12 KA02 KA03 KA10 LA04 LA11 LA12 4F071 AA09 AA80 AC03 AC05 AC15 AC19 AE04 AE19 AF13 AF31 AF31Y AF35 AF35Y AF47 AH19 BA02 BB02 BB07 ABC4A

Claims (7)

[Claims] 1. A cellulose acetate film containing cellulose acetate having a degree of acetylation in the range of 59.0 to 61.5%, and having a Re retardation value defined by the following formula (I) of 20 to 60: The Rth retardation value defined by the following formula (II) is in the range of 70 to 400 nm, and the absolute value of the maximum curl value in an environment at a temperature of 25 ° C. and a relative humidity of 65% is: An optical compensation sheet characterized by being in the range of 0 to 20 / m: (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d nx is the refractive index in the slow axis direction in the film plane; ny is the refractive index in the fast axis direction in the film plane; nz is the refractive index in the thickness direction of the film; Is a file The thickness of the film]. 2. The optical compensation sheet according to claim 1, wherein at least one surface of the cellulose acetate film is subjected to a process of spraying steam. 3. The optical compensation sheet according to claim 2, wherein the vapor is water, methylene chloride, methyl acetate, acetone, or a vapor obtained by evaporating a mixture thereof. 4. A polarizing plate comprising a polarizing film and two transparent protective films disposed on both sides thereof, wherein one of the transparent protective films has a degree of acetylation of 59.0 to 61.5%. And a Retardation value defined by the following formula (I) is in the range of 20 to 200 nm, and an Rth retardation value defined by the following formula (II) is 7:
0-400 nm and at a temperature of 25 ° C.
A polarizing plate characterized in that the absolute value of the maximum curl value in an environment of 65% relative humidity is in the range of 0 to 20 / m: (I) Re = (nx-ny) × d (II) Rth = {(Nx + ny) / 2-nz} × d where nx is the refractive index in the slow axis direction in the film plane; ny is the refractive index in the fast axis direction in the film plane; nz Is the refractive index in the thickness direction of the film; and d is the film thickness]. 5. A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein the polarizing plate comprises a polarizing film and two transparent protective films disposed on both sides thereof. One of the two transparent protective films disposed between the cell and the polarizing plate comprises one sheet of cellulose acetate film containing cellulose acetate having an acetylation degree of 59.0 to 61.5%, and has the following formula ( R defined by I)
e The retardation value is in the range of 20 to 200 nm, the Rth retardation value defined by the following formula (II) is in the range of 70 to 400 nm, and the maximum in an environment of a temperature of 25 ° C. and a relative humidity of 65%. (I) Re = (nx-ny) × d (II) Rth = ｛(nx + ny) / 2−nz ｝ × d where nx is the refractive index in the slow axis direction in the film plane; ny is the refractive index in the fast axis direction in the film plane; nz is the refraction in the thickness direction of the film. And d is the thickness of the film]. 6. The liquid crystal display device according to claim 5, wherein the liquid crystal cell is a VA mode, TN mode, or n-ASM mode liquid crystal cell. 7. A reflective liquid crystal display device in which a reflector, a liquid crystal cell and a polarizing film are laminated in this order, wherein an acetylation degree of 59.0 to 61.5% is provided between the reflector and the polarizing film. A cellulose acetate film containing a certain cellulose acetate is disposed, and the cellulose acetate film has a Re retardation value defined by the following formula (I) in the range of 20 to 200 nm, and the following formula (II)
And the absolute value of the maximum curl value in an environment of a temperature of 25 ° C. and a relative humidity of 65% is 0.
(I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d [wherein , Nx is the refractive index in the slow axis direction in the film plane; ny is the refractive index in the fast axis direction in the film plane; nz is the refractive index in the thickness direction of the film; d is the thickness of the film].