JP2002196146A - Optical compensation sheet, polarization plate and liquid crystal display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display having superior display quality. SOLUTION: An optical compensation sheet used for the liquid crystal display consists of a transparent support body and an optically anisotropic layer formed on the support body. The transparent support body shows 0 to 20 nm for retardation value Re and 70 to 400 nm retardation Rth. The optical anisotropic layer consists of a compound, having discotic structural units and shows negative birefringence. In the layer, the disk faces of the discotic structural units are tilted with respect to the face of the transparent support body and the angle between the disc face of the discotic structural units and the face of the transparent support body varies in the depth direction of the optical anisotropic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical compensation sheet,
The present invention relates to a liquid crystal display device having a polarizing plate and an optical compensation sheet and a color liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device comprises a polarizing plate and a liquid crystal cell. Currently the mainstream TN (Twisted Nemati
c) In a mode TFT (Thin Film Transistor) liquid crystal display device, as described in JP-A-8-50206, an optical compensation sheet is inserted between a polarizing plate and a liquid crystal cell to provide a liquid crystal display device with high display quality. Has been realized. But,
According to this method, there is a problem that the liquid crystal display device itself becomes thick. Japanese Patent Application Laid-Open No. 1-68940 discloses that an optical compensatory sheet (retardation plate) is used on one side of a polarizing film, and an elliptically polarizing plate having a protective film on the other side is used. There is a description that contrast can be increased. However, in the optical compensation sheet of the present invention, a phase difference easily occurs due to distortion such as heat,
It turned out that there was a problem in durability. To solve the problem of phase difference due to distortion, JP-A-7-191217 and EP0911656A2 disclose an optical compensatory sheet in which an optically anisotropic layer made of a discotic compound is coated on a transparent support. By directly using as a protective film of a polarizing plate, the above-mentioned problem relating to durability was solved without increasing the thickness of the liquid crystal display device.

[0003]

In recent years, a liquid crystal display device has been used in a television, and a minute unevenness of a display image which has not been noticed in a conventional application has been regarded as a problem.

An object of the present invention is to provide a liquid crystal display device having a high display quality without causing any problem by arranging an optical compensation sheet for optically compensating a liquid crystal cell on one side of a polarizing film. 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.

[0005]

The inventors of the present invention have made intensive studies and have found that minute unevenness of a display image in a liquid crystal display device is caused by the flatness of a support used for an optical compensation sheet. Furthermore, in order to improve the flatness of the support, changing the solvent when forming a solution on the transparent support,
Alternatively, it has been found that a film can be formed by a co-casting method.

The present invention comprises a transparent support and an optically anisotropic layer provided thereon, wherein the transparent support has the following formula (I):
Re retardation value defined by 0 to 20
Rth in the range of nm and defined by the following formula (II):
The retardation value is in the range of 70 to 400 nm, the optically anisotropic layer is a layer having a negative birefringence composed of a compound having a discotic structural unit, and the disc surface of the discotic structural unit is located on the transparent support surface. The optical compensation sheet is characterized in that the angle between the disc surface of the discotic structure unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. (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 plane of the transparent support; Is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support;
And d is the thickness of the transparent support. The retardation value is a value at a wavelength of 550 nm.

Preferred embodiments of the optical compensation sheet are as follows. (1) The transparent support has an acetylation degree of 59.0 to 61.5%.
The above-mentioned optical compensation sheet comprising a cellulose acetate film and a cellulose acetate film containing 0.01 to 20 parts by mass of an aromatic compound having at least two aromatic rings with respect to 100 parts by mass of cellulose acetate. Further, a cellulose acetate film is a film formed by a solution casting method, and the solvent used for the film formation is an ether having 3 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, or an ester having 3 to 12 carbon atoms. Is more preferable. It is also preferable that the cellulose acetate film contains cellulose acetate as a main component, in which the degree of substitution of the hydroxyl group at the 6-position is higher than that at the 2- and 3-positions. It is more preferable that the cellulose acetate film is a film formed by a co-casting method. (2) The optical compensation sheet described above, wherein an alignment film is formed between the optically anisotropic layer and the transparent support. The alignment film is preferably made of a polymer or a cured film of a polymer, and more preferably rubbed on the surface. It is also preferable that the orientation film is a deposition film obtained by obliquely depositing an inorganic compound. Further, it is more preferable to form an undercoat layer between these alignment films and the optically anisotropic layer. (3) The optical compensation sheet described above, wherein the transparent support has a light transmittance of 80% or more and has an optical axis in a normal direction of the support. (4) The optical compensation sheet described above, wherein the angle between the disk surface and the transparent support surface increases with increasing distance from the bottom surface of the optically anisotropic layer in the depth direction of the optically anisotropic layer. (5) The angle between the disk surface and the transparent support surface is 5 to 85.
The optical compensation sheet described above, which varies in a range of degrees. (6) The minimum value of the angle between the disk surface and the transparent support surface is
It is in the range of 0 to 85 degrees (preferably 5 to 40 degrees), and its maximum value is in the range of 5 to 90 degrees (preferably 30 to 85 degrees).
Optical compensation sheet as described in (1) above. (7) The difference between the minimum value and the maximum value of the angle between the disc surface and the transparent support surface is in the range of 5 to 70 degrees (preferably 10 to 6).
0 degree). (8) The angle between the disk surface and the transparent support surface continuously changes (preferably increases) in the depth direction of the optically anisotropic layer and as the distance from the bottom surface of the optically anisotropic layer increases. Optical compensation sheet. (9) The above-mentioned optical compensation sheet, wherein the optically anisotropic layer further contains a cellulose ester (preferably cellulose acetate butyrate). (10) The above optical compensation sheet wherein the haze of the optically anisotropic layer is 5.0 or less. (11) The optically anisotropic layer is mono-domain or 0.1 μm
The above optical compensatory sheet forming a number of domains of the following sizes: (12) The optical compensation sheet described above, wherein a protective layer is formed on the optically anisotropic layer. (13) The above optical compensation sheet, wherein the optically anisotropic layer has a minimum absolute value of retardation other than 0 in a direction inclined from the normal direction of the optical compensation sheet.

The present invention also provides a polarizing plate comprising a polarizing film and two transparent protective films disposed on both sides of the polarizing film,
One of the transparent protective films has an acetylation degree of 59.0 to 61.5%.
Acetate film containing 0.01 to 20 parts by mass of a cellulose acetate having at least two aromatic rings based on 100 parts by mass of cellulose acetate, and an optically anisotropic film provided thereon. The cellulose acetate film has a Re retardation value defined by the following formula (I) in the range of 0 to 20 nm, and an Rth retardation value defined by the following formula (II) of 70 to 400.
nm, the optically anisotropic layer is a layer having a negative birefringence made of a compound having a discotic structural unit, and the disc surface of the discotic structural unit is inclined with respect to the cellulose acetate film surface; and There is also a polarizing plate characterized in that the angle between the disc surface of the discotic structural unit and the cellulose acetate film surface changes in the depth direction of the optically anisotropic layer. (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. The retardation value is a value at a wavelength of 550 nm.

Preferred embodiments of the above polarizing plate are as follows. (1) A film in which a cellulose acetate film is formed by a solution casting method, and the solvent used for the film formation is ether having 3 to 12 carbon atoms, ketone having 3 to 12 carbon atoms, or 3 to 12 carbon atoms. The above-mentioned polarizing plate which is an ester. Further, the cellulose acetate film is more preferably a film formed by a co-casting method. (2) The polarizing plate described above, wherein an alignment film is formed between the optically anisotropic layer and the transparent support. The alignment film is preferably made of a polymer or a cured film of a polymer, and more preferably rubbed on the surface. It is also preferable that the orientation film is a deposition film obtained by obliquely depositing an inorganic compound. Further, it is more preferable to form an undercoat layer between these alignment films and the optically anisotropic layer. (3) The above-mentioned polarizing plate, wherein the transparent support has a light transmittance of 80% or more and has an optical axis in the normal direction of the support. (4) The above-mentioned polarizing plate, wherein the angle between the disk surface and the transparent support surface increases with increasing distance from the bottom surface of the optically anisotropic layer in the depth direction of the optically anisotropic layer. (5) The angle between the disk surface and the transparent support surface is 5 to 85.
The above-mentioned polarizing plate which varies in a range of degrees. (6) The minimum value of the angle between the disk surface and the transparent support surface is
It is in the range of 0 to 85 degrees (preferably 5 to 40 degrees), and its maximum value is in the range of 5 to 90 degrees (preferably 30 to 85 degrees).
The above-mentioned polarizing plate in degree). (7) The difference between the minimum value and the maximum value of the angle between the disc surface and the transparent support surface is in the range of 5 to 70 degrees (preferably 10 to 6).
0 degree). (8) The angle between the disk surface and the transparent support surface continuously changes (preferably increases) in the depth direction of the optically anisotropic layer and as the distance from the bottom surface of the optically anisotropic layer increases. Polarizing plate. (9) The above-mentioned polarizing plate, wherein the optically anisotropic layer further contains a cellulose ester (preferably cellulose acetate butyrate). (10) The above polarizing plate, wherein the haze of the optically anisotropic layer is 5.0 or less. (11) The optically anisotropic layer is mono-domain or 0.1 μm
The above-mentioned polarizing plate forming a number of domains having the following sizes. (12) The above-mentioned polarizing plate wherein a protective layer is formed on the optically anisotropic layer. (13) The above-mentioned polarizing plate, wherein the optically anisotropic layer has a minimum value of the absolute value of the retardation other than 0 in a direction inclined from the normal direction of the optical compensation sheet.

Further, the present invention provides a liquid crystal cell comprising a pair of substrates each having a transparent electrode and a twisted nematic liquid crystal sealed between the substrates, a pair of polarizing plates provided on both sides of the liquid crystal cell, and In a liquid crystal display device comprising an optical compensation sheet provided between a liquid crystal cell and a polarizing plate,
The optical compensation sheet is composed of a transparent support and an optically anisotropic layer provided thereon, and the transparent support has a Re retardation value defined by the following formula (I) in the range of 0 to 20 nm. An optically anisotropic layer having a negative birefringence comprising a compound having a discotic structural unit, wherein the Rth retardation value defined by (II) is in the range of 70 to 400 nm; A liquid crystal display device wherein the disk surface is inclined with respect to the transparent support surface, and the angle between the disk surface of the discotic structure unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. There is also. (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 plane of the transparent support; Is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support;
And d is the thickness of the transparent support. The retardation value is a value at a wavelength of 550 nm.

Further, the present invention comprises a liquid crystal cell comprising a pair of substrates with a transparent electrode and a twisted nematic liquid crystal sealed between the substrates, and a pair of polarizing plates provided on both sides of the liquid crystal cell. In a liquid crystal display device in which a polarizing plate includes a polarizing film and two transparent protective films disposed on both sides thereof, at least one of the two transparent protective films disposed between the liquid crystal cell and the polarizing film is provided. A transparent support and an optically anisotropic layer provided thereon, wherein the transparent support has a Re retardation value defined by the following formula (I) in the range of 0 to 20 nm, and the following formula (II) Rth retardation value defined by
0 nm, the optically anisotropic layer is a layer having a negative birefringence made of a compound having a discotic structural unit, and the discotic structure unit has a disc surface inclined with respect to the transparent support surface and has a discotic structure. There is also a liquid crystal display device characterized in that the angle between the disk surface of the tick structure unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. (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 plane of the transparent support; Is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support;
And d is the thickness of the transparent support. The retardation value is a value at a wavelength of 550 nm.

Preferred embodiments of the above two liquid crystal display devices are as follows. (1) The liquid crystal display device as described above, wherein the angle formed between the disk surface and the transparent support surface increases with increasing distance from the bottom surface of the optically anisotropic layer in the depth direction of the optically anisotropic layer. (2) The angle between the disk surface and the transparent support surface is 5 to 85.
The above-mentioned liquid crystal display device which varies in a range of degrees. (3) The minimum value of the angle between the disk surface and the transparent support surface is
It is in the range of 0 to 85 degrees (preferably 5 to 40 degrees), and its maximum value is in the range of 5 to 90 degrees (preferably 30 to 85 degrees).
The above liquid crystal display device. (4) The above-mentioned liquid crystal display device, wherein the optically anisotropic layer further contains a cellulose ester (preferably, cellulose acetate butyrate). (5) The liquid crystal display device described above, wherein an alignment film is formed between the optically anisotropic layer and the transparent support. (6) The liquid crystal display device described above, wherein the optically anisotropic layer has a minimum absolute value of retardation other than 0 in a direction inclined from the normal direction of the optical compensation sheet. (7) the substrate of the liquid crystal cell has an alignment surface that has been rubbed in one direction, and the optical compensatory sheet has a direction in which the direction of the minimum value of the retardation is orthogonally projected on the liquid crystal cell; The liquid crystal display device according to the above (6), wherein the liquid crystal cell is disposed on the liquid crystal cell such that an angle formed by the rubbing direction of the substrate surface of the liquid crystal cell near the optical compensation sheet is 90 to 270 degrees. (8) The liquid crystal display device described above, wherein one or two optical compensation sheets are provided on one side of the liquid crystal cell, or two sheets are provided on both sides of the liquid crystal cell.

Further, the present invention provides a liquid crystal cell comprising a pair of substrates having a transparent electrode, a pixel electrode and a color filter, and a twisted nematic liquid crystal sealed between the substrates, provided on both sides of the liquid crystal cell. In a color liquid crystal display device comprising a pair of polarizing plates and an optical compensation sheet provided between the liquid crystal cell and the polarizing plate, the optical compensation sheet comprises a transparent support and an optically anisotropic layer provided thereon. The transparent support has a Re retardation value defined by the following formula (I) in the range of 0 to 20 nm, an Rth retardation value defined by the following formula (II) in the range of 70 to 400 nm, The optically anisotropic layer is a layer having a negative birefringence made of a compound having a discotic structural unit. There is also a liquid crystal display device characterized in that it is inclined with respect to the transparent support surface and the angle between the disc surface of the discotic structure unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. . (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 plane of the transparent support; Is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support;
And d is the thickness of the transparent support. The retardation value is a value at a wavelength of 550 nm.

Further, the present invention provides a liquid crystal cell comprising a pair of substrates having a transparent electrode, a pixel electrode and a color filter, and a twisted nematic liquid crystal sealed between the substrates, provided on both sides of the liquid crystal cell. In a color liquid crystal display device comprising a pair of polarizing plates, the polarizing plate comprising a polarizing film and two transparent protective films disposed on both sides of the polarizing film, two transparent films disposed between the liquid crystal cell and the polarizing film. At least one of the protective films is composed of a transparent support and an optically anisotropic layer provided thereon, of the transparent support,
The Re retardation value defined by the following formula (I) is in the range of 0 to 20 nm, and the Rth retardation value defined by the following formula (II) is 70 to 400 nm.
Wherein the optically anisotropic layer is a layer having a negative birefringence comprising a compound having a discotic structural unit, wherein the disc surface of the discotic structural unit is inclined with respect to the transparent support surface and There is also a liquid crystal display device characterized in that the angle between the disk surface of the structural unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. (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 plane of the transparent support; Is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support;
And d is the thickness of the transparent support. The retardation value is a value at a wavelength of 550 nm.

Preferred embodiments of the above two color liquid crystal display devices are as follows. (1) The color liquid crystal display device described above, wherein the angle formed between the disk surface and the transparent support surface increases with increasing distance from the bottom surface of the optically anisotropic layer in the depth direction of the optically anisotropic layer. (2) The angle between the disk surface and the transparent support surface is 5 to 85.
The color liquid crystal display device described above, which varies in a range of degrees. (3) The minimum value of the angle between the disk surface and the transparent support surface is
It is in the range of 0 to 85 degrees (preferably 5 to 40 degrees), and its maximum value is in the range of 5 to 90 degrees (preferably 30 to 85 degrees).
The above color liquid crystal display device. (4) The above-mentioned color liquid crystal display device, wherein the optically anisotropic layer further contains a cellulose ester (preferably, cellulose acetate butyrate). (5) The color liquid crystal display device described above, wherein an alignment film is formed between the optically anisotropic layer and the transparent support. (6) One of the pair of substrates has a (transparent) pixel electrode,
The color liquid crystal display device described above, wherein the other substrate has a counter transparent electrode and a color filter. (7) The (transparent) pixel electrode is TF as a non-linear active element.
T (thin-film-transistor) or MIM (metal-insulat
(6) The color liquid crystal display device according to the above (6), comprising: (8) The above color liquid crystal display device used in a normally white mode, wherein two absorption axes of a pair of polarizing plates are in a right angle relationship with each other. (9) The color liquid crystal display device used in a normally black mode, in which two absorption axes of a pair of polarizing plates are parallel to each other. (10) The color liquid crystal display device described above, wherein the optically anisotropic layer has a minimum absolute value of retardation other than 0 in a direction inclined from the normal direction of the optical compensation sheet. (11) The substrate of the liquid crystal cell has an alignment surface that has been rubbed in one direction, and the direction of the optical compensation sheet when the direction of the minimum value of the retardation is orthogonally projected on the liquid crystal cell; The liquid crystal display device according to the above (10), wherein the liquid crystal cell is disposed on the liquid crystal cell such that an angle between the liquid crystal cell and the rubbing direction of the substrate surface near the optical compensation sheet is 90 to 270 degrees.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The optical compensatory sheet of the present invention is an optical compensatory sheet comprising a transparent support and an optically anisotropic layer provided thereon, wherein the optically anisotropic layer has discotic structural units. This is a layer made of a compound having negative birefringence. Examples of the compound having a discotic structural unit include a low molecular weight discotic liquid crystal compound such as a monomer or a polymer obtained by polymerization of a polymerizable discotic liquid crystal compound.
In general, discotic compounds can be broadly classified into compounds having a discotic liquid crystal phase (that is, a discotic nematic phase) and compounds having no discotic liquid crystal phase. Discotic compounds generally have negative birefringence. The present invention makes use of the negative birefringence of the discotic compound and converts the discotic structural unit into an optically anisotropic layer having an angle between the surface of the discotic structural unit (disc surface) and the transparent support surface. This is achieved by arranging them so as to change in the direction and adjusting the retardation value of the transparent support.

The optical compensatory sheet of the present invention comprises a transparent support and an optically anisotropic layer provided on the transparent support and comprising a compound having a discotic structural unit. It is preferable to provide them between them.
When a plurality of optically anisotropic layers are provided, the alignment film may be provided on the optically anisotropic layer. Further, it is preferable to provide an undercoat layer (adhesive layer) between the transparent substrate and the alignment film. A protective layer may be provided on the optically anisotropic layer and on the back surface of the substrate.

[Transparent Support] As the material of the transparent support of the present invention, any material can be used as long as it is transparent. A material having a light transmittance of 80% or more is preferable, and a material having optical isotropy when viewed from the front is particularly preferable. Therefore, the transparent support is preferably manufactured from a material having a small intrinsic birefringence. Such materials include ZEONEX (Zeon Corporation)
And commercial products such as ARTON (produced by Nippon Synthetic Rubber Co., Ltd.) and Fujitac (produced by Fuji Photo Film Co., Ltd.). Furthermore, even a material having a large intrinsic birefringence such as polycarbonate, polyarylate, polysulfone, and polyethersulfone can be used for solution casting,
It can be obtained by appropriately setting conditions such as melt extrusion and the like, and studying the stretching state in the vertical and horizontal directions. When used as a protective film for a polarizing film, it is most preferable to use a cellulose acetate film because of its moisture permeability. The thickness of the transparent support is preferably from 20 μm to 150 μm, more preferably from 30 μm to 120 μm, and most preferably from 35 μm to 100 μm. Less than,
The transparent support used in the present invention will be described by taking, as an example, the case where a cellulose acetate film is used.

[Retardation of Film] The Re retardation value and Rth retardation value of the cellulose acetate film (transparent support) are as follows:
It is defined by the following formulas (I) and (II). (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d In the formulas (I) and (II), nx is a slow axis direction in the film plane ( (The direction in which the refractive index becomes the maximum). In the formulas (I) and (II), ny is the refractive index in the fast axis direction (direction in which the refractive index is minimum) in the film plane. In the formula (II), nz is a refractive index in the thickness direction of the film. In formulas (I) and (II), d
Is the film thickness in nm.

In the present invention, the Re retardation value of the cellulose acetate film is adjusted to 0 to 20 nm, and the Rth retardation value is adjusted 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 250 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. The birefringence (Δn: nx−ny) of the cellulose acetate film is 0.00 to 0.002.
It is preferred that Further, the birefringence in the thickness direction of the cellulose acetate film ｛(nx + ny) / 2−n
z｝ is preferably 0.001 to 0.04.

[Cellulose Acetate] In the present invention, it is preferable to use cellulose acetate having an acetylation degree of 59.0 to 61.5%. The acetylation degree means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is
According to the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like). The viscosity average degree of polymerization (DP) of the cellulose ester is
It is preferably at least 250, more preferably at least 290. Further, the cellulose ester used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably from 1.0 to 1.7, more preferably from 1.3 to 1.65, and most preferably from 1.4 to 1.6. preferable. In general, the 2,3,6 hydroxyl groups of cellulose acetate are not evenly distributed to 1/3 of the total degree of substitution, and the degree of substitution of the 6-position hydroxyl group tends to decrease. In the present invention, it is preferable that the substitution degree of the hydroxyl group at the 6-position of cellulose acetate is larger than that at the 2- and 3-positions. It is preferable that the hydroxyl group at the 6-position is substituted with an acetyl group in an amount of 30% or more, more preferably 31% or more, particularly preferably 32% or more with respect to the whole degree of substitution. Further, the degree of substitution of the 6-position acetyl group of cellulose acetate is preferably 0.88 or more. The 6-position hydroxyl group may be substituted with an acyl group having 3 or more carbon atoms other than an acetyl group such as a propionyl group, a butyroyl group, a valeroyl group, a benzoyl group, and an acryloyl group. I can do it. The degree of substitution at each position is measured by N
It can be determined by MR. As the cellulose acetate of the present invention, Synthesis Example 1 described in paragraphs 0043 to 0044 of JP-A-11-5851, paragraph No. 00
Synthesis Example 2 described in Nos. 48 to 0049, and paragraph No. 00
Cellulose acetate obtained by the method of Synthesis Example 3 described in 51 to 0052 can be used.

[Retardation raising 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,
It includes a phenanthridine ring, a xanthene ring, a phenazine ring, a phenothiazine ring, a phenoxatiin ring, a phenoxazine ring and a thianthrene ring. Preferred are a naphthalene ring, an azulene ring, an indole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring, a benzotriazole ring and a quinoline ring. The single bond in (b) is preferably a bond between carbon atoms of two aromatic rings. By joining two aromatic rings with two or more single bonds,
An aliphatic ring or a non-aromatic heterocyclic ring may be formed between two aromatic rings.

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

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

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

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

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

[Production of Cellulose Acetate Film]
The cellulose acetate film is preferably produced by a solution casting method. It is more preferable to produce a cellulose acetate film by a solvent casting method using a solution used for solution casting as an organic solvent. 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 an ether having 3 to 12 carbon atoms,
It is preferable to include a solvent selected from ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and 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.

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

The solution can be prepared by 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 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 maintained at a temperature equal to or higher than the pseudo phase transition temperature, and 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. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. It is preferable that the surface of the drum or the band is finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. Nos. 2,336,310 and 23,676.
No. 03, No. 2492078, No. 2492977, No. 2492978, No. 2607704, No. 27390
Nos. 69 and 2739070; British Patent 640731
Nos. 736892 and JP-B-45-455.
No. 4, No. 49-5614, JP-A-60-176834.
And JP-A-60-203430 and JP-A-62-115035. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less.
After casting, it is preferable to dry by blowing on air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried with hot air having a temperature gradually changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in JP-B-5-17844. According to this method, the time from casting to stripping can be reduced. In order to carry out this method, it is necessary that the dope gels at the surface temperature of the drum or band during casting.

Using the prepared cellulose acetate solution (dope), a film can be formed by a co-casting method in which two or more layers are cast. In this case, it is preferable to produce a cellulose acetate film by a solvent casting method. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is in the range of 10 to 40%. It is preferable that the surface of the drum or the band is finished in a mirror state.

When two or more cellulose acetate solutions are cast, a plurality of cellulose acetate solutions can be cast, and a plurality of casting ports provided at intervals in the direction of travel of the support. Alternatively, a film containing cellulose acetate may be cast and laminated to form a film. For example, JP-A-61-158414
, JP-A-1-122419 and JP-A-11-1
The method described in each specification of No. 98285 can be used. The film can also be formed by casting a cellulose acetate solution from two casting ports. For example, Japanese Patent Publication No. 60-27562,
No. 94724, JP-A-61-947245, JP-A-6-94745
The methods described in JP-A-1-104813, JP-A-61-158413 and JP-A-6-134933 can be used. Also, Japanese Patent Application Laid-Open No. 56-16261
Wrapping the flow of the high-viscosity cellulose acetate solution described in the specification 7 with a low-viscosity cellulose acetate solution,
It is also possible to use a cellulose acetate film casting method in which the high and low viscosity cellulose acetate solutions are simultaneously extruded.

Further, 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. Films can also be made. For example, Japanese Patent Publication No. 44-2
No. 0235 can be mentioned.
The same cellulose acetate solution may be used for casting, or different cellulose acetate solutions may be used. In order to provide a function to a plurality of cellulose acetate layers, a cellulose acetate solution corresponding to the function may be extruded from each casting port. Furthermore, the cellulose acetate solution of the present invention can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, a polarizing layer, etc.).

In the case of the conventional single-layer liquid, it is necessary to extrude a high-concentration and high-viscosity cellulose acetate solution in order to obtain a required film thickness. In such a case, the stability of the cellulose acetate solution was poor, and solid matter was generated, which often caused problems such as lumps and poor flatness. As a solution to this problem, by casting a plurality of cellulose acetate solutions from a casting port, it is possible to simultaneously extrude a high-viscosity solution onto a support, thereby improving the flatness and producing an excellent planar film. Not only can it be produced, but also by using a concentrated cellulose acetate solution, the drying load can be reduced, and the production speed of the film can be increased.

A plasticizer can be added to the cellulose acetate film in order to improve the mechanical properties or to increase the drying speed. As a plasticizer,
Phosphate or carboxylate esters are used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCC).
P) is included. Representative carboxylic esters 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 from 0.01 to 1% by mass, more preferably from 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 onto the film surface. Particularly preferred examples of the deterioration inhibitor include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

[Biaxial stretching] In order to reduce virtual distortion,
Preferably, the cellulose acetate film is stretched. By stretching, virtual strain in the stretching direction can be reduced, and therefore, biaxial stretching is more preferable to reduce strain in all directions in the plane. For biaxial stretching,
There are a simultaneous biaxial stretching method and a sequential biaxial stretching method, but a sequential biaxial stretching method is preferred from the viewpoint of continuous production, after casting the dope, peeling it off from a band or a drum, stretching it in the width direction, and then stretching it. Stretched in the direction. The stretching may be performed in the longitudinal direction and then in the width direction. The method of stretching in the width direction is described in, for example, JP-A-62-115035, JP-A-4-152125, JP-A-4-284221, and JP-A-4-284221.
Nos. -298310 and 11-48271. The stretching of the film is performed at normal temperature or under heating conditions. The heating temperature is preferably equal to or lower than the glass transition temperature of the film. The film can be stretched during the drying process, and is particularly effective when the solvent remains. In the case of stretching in the longitudinal direction, the film is stretched, for example, by adjusting the speed of the film transport roller so that the film winding speed is faster than the film peeling speed. In the case of stretching in the width direction, the film can be stretched by conveying the film while holding it with a tenter and gradually increasing the width of the tenter. After drying the film, the film can be stretched using a stretching machine (preferably, uniaxial stretching using a long stretching machine). The stretching ratio of the film (the ratio of the increase by stretching to the original length) is preferably 5 to 50%, more preferably 10 to 50%.
-40%, most preferably 15-35%.

The steps from the casting to the post-drying may be performed under an air atmosphere or under an inert gas atmosphere such as nitrogen gas. The winding machine relating to the production of the cellulose acetate film of the present invention may be a generally used one, and may be a winding method such as a constant tension method, a constant torque method, a taper tension method, and a program tension control method with a constant internal stress. Can be wound up.

[Hygroscopic Expansion Coefficient] The hygroscopic expansion coefficient indicates the amount of change in the length of the sample when the relative humidity is changed at a constant temperature. In order to prevent the frame-shaped transmittance from increasing on the display surface of the liquid crystal display device, the coefficient of hygroscopic expansion of the cellulose acetate film is preferably 30 × 10 ⁻⁵ /% RH or less, and more preferably 15 × 10 ⁻⁵ /%. % RH or less, more preferably 10 × 10 ⁻⁵ /% RH or less. The smaller the coefficient of hygroscopic expansion is, the more preferable it is, but usually it is 1.0 × 10 ⁻⁵ /% RH or more. The method for measuring the coefficient of hygroscopic expansion will be described below. 5 mm width from the prepared polymer film (retardation plate). Cut out a sample with a length of 20 mm and fix one end to 25
The sample was hung under an atmosphere of 20 ° C. and 20% RH (R ₀ ). A 0.5 g weight was hung on the other end, and left for 10 minutes to measure the length (L ₀ ). Next, while maintaining the temperature at 25 ° C., the humidity was set to 80% RH (R ₁ ), and the length (L ₁ ) was measured. The coefficient of hygroscopic expansion was calculated by the following equation. The measurement was performed for 10 samples for the same sample, and the average value was adopted. Hygroscopic expansion coefficient [/% RH] = {(L ₁ −L ₀ ) / L ₀ }
/ (R ₁ -R ₀ )

It has been found that the dimensional change due to moisture absorption can be achieved by reducing the free volume in the polymer film.
What largely affects the free volume is the amount of the residual solvent at the time of film formation. A common technique for reducing residual solvent is to dry at high temperature and for a long time, but if it is too long, the productivity naturally drops. Therefore, the amount of the residual solvent with respect to the cellulose acetate film is preferably in the range of 0.01 to 1% by mass, more preferably in the range of 0.02 to 0.07% by mass, and more preferably in the range of 0.03 to 0. Most preferably, it is in the range of 05% by mass. By controlling the amount of the residual solvent, a polarizing plate having optical compensation ability can be manufactured at low cost and with high productivity.

Further, as another method for reducing the dimensional change due to moisture absorption, it is preferable to add a compound having a hydrophobic group. The material having a hydrophobic group is not particularly limited as long as the material has a hydrophobic group such as an alkyl group or a phenyl group in the molecule. The corresponding material is particularly preferably used. Examples of these preferred materials include triphenyl phosphate (TPP),
Tribenzylamine (TBA) and the like can be mentioned. The addition amount of these compounds having a hydrophobic group is preferably in the range of 0.01 to 10% by mass, more preferably in the range of 0.1 to 5% by mass, based on the solution (dope) to be adjusted. It is most preferably in the range of 1 to 3% by mass.

[Surface Treatment of Cellulose Acetate Film] The cellulose acetate film is preferably subjected to a surface treatment. Specific methods include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. In addition, Japanese Patent Application Laid-Open
As described in JP-A-333433, it is also preferable to provide an undercoat layer. From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film in these treatments is preferably set to Tg or lower, specifically 150 ° C. or lower. When used as a transparent protective film for a polarizing plate, it is particularly preferable to perform an acid treatment or an alkali treatment, that is, a saponification treatment on cellulose acetate, from the viewpoint of adhesion to the polarizing film. The surface energy is preferably at least 55 mN / m,
/ M or more and 75 mN / m or less.

Hereinafter, a specific description will be given of an alkali saponification treatment as an example. The alkali saponification treatment is preferably performed in a cycle of immersing the film surface in an alkaline solution, neutralizing the film with an acidic solution, washing with water, and drying. Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution. The specified concentration of hydroxide ions is preferably in the range of 0.1 to 3.0 N, and more preferably in the range of 0.5 to 2.
More preferably, it is in the range of 0N. The alkali solution temperature is preferably in the range of room temperature to 90 ° C,
More preferably, it is in the range of 40 to 70 ° C. The surface energy of the solid can be determined by the contact angle method, the heat of wetting method, and the adsorption method as described in “Basic and Applied Wetting” (Realize Inc., issued on Dec. 10, 1989). In the case of a cellulose acetate film, it is preferable to use a contact angle method. Specifically, two types of solutions whose surface energies are known are dropped on a cellulose acetate film, and at the intersection between the surface of the droplet and the film surface, the angle between the tangent drawn on the droplet and the film surface is determined. The angle containing the drop is defined as the contact angle, and the surface energy of the film can be calculated by calculation.

[Undercoat layer] In order to increase the adhesive strength between the transparent support and the alignment film, it is preferable to provide an undercoat layer on the transparent support. The undercoat layer is generally formed by coating on the surface of a surface-treated transparent support. Various contrivances have been made also for the composition of the undercoat layer, and a layer (hereinafter, referred to as a first layer) which adheres well to a polymer film (transparent support).
An undercoating first layer), and a multilayer method of applying a hydrophilic resin layer (hereinafter, abbreviated as an undercoating second layer) which adheres well to the alignment film as a second layer thereon, and a hydrophobic group and a hydrophilic layer. There is a single-layer method in which only one resin layer containing both a functional group and a functional group is applied.

In the first layer of the undercoat in the multilayer method, for example, a copolymer prepared from a monomer selected from vinyl chloride, vinylidene chloride, butadiene, methacrylic acid, acrylic acid, itaconic acid, maleic anhydride and the like is used. Coalescing; polyethylene imine; epoxy resin; grafted gelatin; nitrocellulose; polyvinyl bromide, polyvinyl fluoride,
Polyvinyl acetate, chlorinated polyethylene, chlorinated polypropylene, brominated polyethylene, chlorinated rubber, vinyl chloride
Ethylene copolymer, vinyl chloride-propylene copolymer,
Vinyl chloride-styrene copolymer, isobutylene chloride copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-styrene-maleic anhydride terpolymer, vinyl chloride-styrene-acrylonitrile copolymer, vinyl chloride- Butadiene copolymer, vinyl chloride-isoprene copolymer, vinyl chloride-chlorinated propylene copolymer, vinyl chloride-vinylidene chloride-vinyl acetate terpolymer, vinyl chloride-acrylate copolymer, vinyl chloride- Maleic acid ester copolymer, vinyl chloride-methacrylic acid ester copolymer, vinyl chloride-acrylonitrile copolymer, internally plasticized polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinylidene chloride, vinylidene chloride-methacrylic acid Ester copolymer, vinylidene chloride-acrylonitrile copolymer Halogen-containing synthetic resins such as vinylidene chloride-acrylate copolymer, chloroethyl vinyl ether-acrylate copolymer, and polychloroprene; polyethylene, polypropylene, polybutene, poly-3-methylbutene, and poly-1,2- Α-olefin copolymers such as butadiene; ethylene-propylene copolymers, ethylene-vinyl ether copolymers,
Ethylene-propylene-1,4-hexadiene copolymer, ethylene-vinyl acetate copolymer, butene-1-propylene copolymer, butadiene-acrylonitrile copolymer, and blends of these copolymers with halogen-containing resins Products: Acrylic acid methyl ester-acrylonitrile copolymer, acrylic acid ethyl ester-styrene copolymer, methacrylic acid methyl ester-acrylonitrile copolymer, polymethacrylic acid methyl ester, methacrylic acid methyl ester-styrene copolymer, methacrylic acid Butyl ester-styrene copolymer, polymethyl acrylate, poly-α-methyl acrylate, methoxyethyl acrylate, glycidyl polyacrylate, butyl polyacrylate, methyl acrylate And acrylic resins such as polyacrylic acid ethyl ester, acrylic acid-butyl acrylate copolymer, acrylate-butadiene-styrene copolymer and methacrylic acid ester-butadiene-styrene copolymer; polystyrene, poly-α-methyl Styrene, styrene-dimethyl fumarate copolymer, styrene
Maleic anhydride copolymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer and styrene-
Styrene resins such as butadiene-acrylonitrile copolymer; poly-2,6-dimethylphenylene oxide;
Polyvinyl carbazole; poly-p-xylylene; polyvinyl formal; polyvinyl acetal; polyvinyl butyral; polyvinyl phthalate; cellulose triacetate; cellulose butyrate; cellulose butyrate; cellulose phthalate; nylon 6;
Methoxymethyl-6-nylon; nylon-6,10-
Polycapramid; poly-N-butyl-nylon-6-polyethylene sebacate; polybutylene glutarate; polyhexamethylene adipate; polybutylene isophthalate; polyethylene terephthalate; polyethylene adipate; polyethylene adipate terephthalate; Polyethylene oxybenzoate; Bisphenol A-isophthalate; Polyacrylonitrile; Bisphenol A-adipate; Polyhexamethylene-m-benzenedisulfonamide; Polytetramethylene hexamethylene carbonate; Polydimethylsiloxane; Bonate; and bisphenol A-polycarbonate Can. These oligomers or polymers are described in E.I. H. Immergut "P
oligomer Handbook ", IV, 187-2
31, Interscience Pub. New Y
ork, 1966. Gelatin can be used as a material for the second layer of the undercoat.

In the single-layer method, a polymer film (transparent support) is expanded and mixed with an interface with a hydrophilic primer polymer to form an undercoat layer so that good adhesion can be obtained. As the hydrophilic undercoat polymer used in the present invention, a water-soluble polymer, a cellulose ester, a latex polymer, a water-soluble polyester and the like can be used. Examples of the water-soluble polymer include gelatin, gelatin derivatives, casein, agar, sodium alginate, starch, polyvinyl alcohol, polyacrylic acid copolymer and maleic anhydride copolymer, and the like.
Examples of the cellulose ester include carboxymethyl cellulose and hydroxyethyl cellulose. Examples of the latex polymer include a vinyl chloride-containing copolymer, a vinylidene chloride-containing copolymer, an acrylate-containing copolymer, a vinyl acetate-containing copolymer, and a butadiene-containing copolymer. Among these, gelatin is most preferred. As the gelatin, generally used ones such as so-called lime-processed gelatin, acid-processed gelatin, enzyme-processed gelatin, gelatin derivatives and modified gelatin can be used. Among these gelatins, lime-treated gelatin and acid-treated gelatin are most preferably used. These gelatins have various impurities in the production process, for example, 0.1%.
1 to 20000 ppm of metals (Na, K, Li, R
b, Ca, Mg, Ba, Ce, Fe, Sn, Pb, A
1, metals such as Si, Ti, Au, Ag, Zn, Ni,
And its ions), ions (F ⁻ , Cl ⁻ , B
r ⁻ , I ⁻ , sulfate ion, nitrate ion, acetate ion, ammonium ion, etc.). In particular, lime-treated gelatin generally contains Ca and Mg ions, and the content is 10 to 3000 p.
pm in general, and 1000 in terms of undercoating performance.
ppm or less, more preferably 500 ppm or less. Specific examples of the compounds used in the adhesion improving layer (undercoat second layer in the multilayer method and undercoat layer in the single layer method) used in the invention are shown below.

[0056]

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[0057]

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[0058]

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[0059]

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[0060]

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In addition, the coating solution for forming the undercoat layer may contain various additives as necessary. For example, surfactants, antistatic agents, pigments, coating aids and the like can be mentioned. In the undercoat layer of the present invention, various known gelatin hardeners can be used. Gelatin hardeners include chromium salts (chromium alum, etc.), aldehydes (formaldehyde, glutaraldehyde, etc.), isocyanates, epichlorohydrin resins and polyamide-epichlorohydrin resins, cyanuric chloride compounds, vinyl sulfone or sulfonyl compounds, carbamoyl Examples thereof include an ammonium salt compound, an amidinium salt compound, a carbodiimide compound, and a pyridinium salt compound.

The undercoat layer of the present invention may contain inorganic or organic fine particles as a matting agent to such an extent that transparency is not substantially impaired. As a matting agent for inorganic fine particles, silica (SiO ₂ ), titanium dioxide (Ti)
O ₂ ), calcium carbonate and magnesium carbonate can be used. As organic fine particle matting agents,
Polymethyl methacrylate, cellulose acetate propionate, polystyrene and US Pat.
For example, the polymer described in No. 4 can be used. The average particle size of these fine particle matting agents is 0.01 to 1
Those having a thickness of 0 μm are preferred. More preferably, 0.05 to
5 μm. The content is 0.5 to 600 m
g / m ² is preferable, and 1 to 400 mg / m ² is more preferable.

[Alignment Film] The alignment film is generally provided on a transparent support or on the undercoat layer. The alignment film functions to define the alignment direction of the liquid crystalline discotic compound provided thereon. This orientation gives the optical axis tilted from the optical compensation sheet. The orientation film may be any layer as long as it can impart orientation to the optically anisotropic layer. Preferred examples of the alignment film include a rubbed layer of an organic compound (preferably a polymer), an obliquely deposited layer of an inorganic compound, and a layer having microgrooves, ω-tricosanoic acid, dioctadecylmethylammonium chloride, and stearyl. Langmuir such as methyl acid
Examples include a cumulative film formed by a blow jet method (LB film), and a layer in which a dielectric is oriented by applying an electric or magnetic field.

Examples of the organic compound for the alignment film include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol, poly (N-methylolacrylamide),
Styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene,
Examples include polymers such as polypropylene and polycarbonate, and compounds such as silane coupling agents. Preferred examples of the polymer include polyimide, polystyrene, polymers of styrene derivatives, gelatin, polyvinyl alcohol, and alkyl-modified polyvinyl alcohol having an alkyl group (preferably having 6 or more carbon atoms). An alignment film obtained by performing an alignment treatment on these polymer layers can align a liquid crystalline discotic compound obliquely.

Among them, alkyl-modified polyvinyl alcohol is particularly preferable, and has excellent ability to uniformly align the liquid crystalline discotic compound. This is presumed to be due to strong interaction between the alkyl chains on the alignment film surface and the alkyl side chains of the discotic liquid crystal. The alkyl group preferably has 6 to 14 carbon atoms, and further has -S- and-.
_{(CH 3) C (CN)} - or _{- (C 2 H 5) N} -CS
It is preferably bonded to polyvinyl alcohol via -S-. The alkyl-modified polyvinyl alcohol has an alkyl group at the end, and has a saponification degree of 80.
% Or more, and the degree of polymerization is preferably 200 or more. As the polyvinyl alcohol having an alkyl group in the side chain, commercially available products such as MP103, MP203, and R1130 manufactured by Kuraray Co., Ltd. can be used.

Also, a polyimide film (preferably, a fluorine atom-containing polyimide), which is widely used as an alignment film for LCD, is preferable as the organic alignment film. For this, a polyamic acid (for example, LQ / LX series manufactured by Hitachi Chemical Co., Ltd., SE series manufactured by Nissan Chemical Co., Ltd.) is applied to the surface of the support, and baked at 100 to 300 ° C. for 0.5 to 1 hour. Later, it is obtained by rubbing. Furthermore, the alignment film of the present invention can be obtained by introducing a reactive group into the polymer or by using the polymer together with a crosslinking agent such as an isocyanate compound and an epoxy compound to cure the polymer. Preferably, it is a membrane.

For the rubbing treatment, a treatment method widely used as a liquid crystal alignment treatment step for LCD can be used. That is, a method of rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like to obtain the alignment can be used. Generally, rubbing is performed about several times using a cloth or the like in which fibers having a uniform length and thickness are planted on average.

Further, as a deposition material of the inorganic oblique deposition film, SiO is a representative, and a metal oxide such as TiO ₂ and ZnO ₂ , a fluoride such as MgF ₂ , and further, Au, A
1 and the like. Note that the metal oxide can be used as an oblique deposition material as long as it has a high dielectric constant, and is not limited to the above. The inorganic oblique deposition film can be formed using a deposition device. An inorganic oblique deposition film can be formed by fixing a film (support) and vapor-depositing the film, or by moving a long film and continuously vapor-depositing the film.

As a method of aligning the optically anisotropic layer without using an alignment film, a method of applying an electric field or a magnetic field while heating the optically anisotropic layer on the support to a temperature at which a discotic liquid crystal layer can be formed. Can be mentioned.

The optically anisotropic layer of the present invention is formed on a transparent support or an alignment film. The optically anisotropic layer of the present invention is a layer having a negative birefringence made of a compound having a discotic structural unit. That is, the optically anisotropic layer is a layer of a low molecular weight liquid crystalline discotic compound such as a monomer or a layer of a polymer obtained by polymerization (curing) of a polymerizable liquid crystalline discotic compound. Examples of the discotic (disk-shaped) compound of the present invention include C.I. Destr
ade et al., Mol. Cryst. 71 volumes, 1
Benzene derivatives described on page 11 (1981); Destrade et al., Mol. Cr
yst. 122, 141 pages (1985), Phys
ics lett, A, vol. 78, p. 82 (1990); Kohne et al., Angew. Chem. 96 volumes, 70 pages (1
984) and the cyclohexane derivative described in J.
M. J. Lehn et al. Chem. Commu
n. , P. 1794 (1985); Research report by Zhang et al. Am. Chem. Soc. 116 volumes, 2
Examples thereof include azacrown-based and phenylacetylene-based macrocycles described on page 655 (1994). The above discotic (disc-like) compounds generally have a structure in which these are used as a core of a molecular center, and linear alkyl groups, alkoxy groups, substituted benzoyloxy groups and the like are radially substituted as the linear chains. , Which exhibit liquid crystallinity and are generally called discotic liquid crystals. However, the present invention is not limited to the above description as long as the molecule itself has negative uniaxiality and can impart a certain orientation. In addition, in the present invention, the term "formed from a discotic compound" does not mean that the final product need be the compound. For example, the low-molecular-weight discotic liquid crystal has a group that reacts with heat, light, or the like. Heat, resulting in heat,
It also includes those which are polymerized or crosslinked by a reaction with light or the like to increase the molecular weight and lose liquid crystallinity.

Preferred examples of the discotic compound are shown below.

[0072]

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[0073]

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[0074]

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[0075]

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[0076]

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[0077]

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[0078]

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[0079]

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[0080]

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[0081]

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[0082]

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As described above, the optical compensation sheet of the present invention is preferably prepared by providing an alignment film on a transparent support and then forming an optically anisotropic layer on the alignment film.

The optically anisotropic layer of the present invention is a layer having a negative birefringence composed of a compound having a discotic structural unit, and the surface of the discotic structural unit is inclined with respect to the transparent support surface, and The angle between the surface of the discotic structural unit and the surface of the transparent support varies in the depth direction of the optically anisotropic layer.

The angle (tilt angle) of the surface of the discotic structure unit generally increases or decreases in the depth direction of the optically anisotropic layer and as the distance from the bottom surface of the optically anisotropic layer increases. Preferably, the angle of inclination increases with increasing distance. Further, as the change of the inclination angle, a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including the continuous increase and the continuous decrease, and an intermittent change including the increase and the decrease may be cited. it can. The intermittent change includes a region where the inclination angle does not change in the thickness direction. It is preferable that the inclination angle increases or decreases as a whole, even if it includes a region that does not change. Further, the inclination angle is preferably increased as a whole, and is particularly preferably changed continuously.

FIG. 1 schematically shows a typical example of a cross section of the optically anisotropic layer of the present invention. The optically anisotropic layer 23 is provided on the alignment film 22 formed on the transparent support 21.
The liquid crystal discotic compounds 23a, 23b, and 23c constituting the optically anisotropic layer 23 have a discotic structural unit Pa, Pb, and Pc whose surface 2 is parallel to the surface of the transparent support 21.
1a, 21b, 21c, and their inclination angles θa, θb, θc (the angles formed by the plane of the discotic structural unit and the plane of the transparent support) are the depths from the bottom of the optically anisotropic layer ( It increases in order with the increase in the distance in the (thickness) direction. 24 represents the normal line of the transparent support. The liquid crystalline discotic compound is a planar molecule, and therefore, has only one plane, ie, a disk surface (eg, 21a, 21a) in the molecule.
b, 21c).

It is preferable that the inclination angle (angle) changes in a range of 5 to 85 degrees (particularly, in a range of 10 to 80 degrees). The minimum value of the inclination angle is preferably in the range of 0 to 85 degrees (particularly 5 to 40 degrees), and the maximum value is preferably in the range of 5 to 90 degrees (particularly 30 to 85 degrees). In FIG. 1, the tilt angle (eg, θa) of the discotic structure unit on the support side substantially corresponds to the minimum value, and the tilt angle (eg, θc) of the discotic structure unit substantially corresponds to the maximum value. I have. Further, the difference between the minimum value and the maximum value of the inclination angle is preferably in the range of 5 to 70 degrees (particularly, 10 to 60 degrees).

In general, the optically anisotropic layer is formed by applying a solution in which a discotic compound and another compound are dissolved in a solvent to an orientation film, drying the solution, and then heating the solution to a discotic nematic phase formation temperature, and then, in an orientation state ( It is obtained by cooling while maintaining the discotic nematic phase). Alternatively, the optically anisotropic layer is formed by applying a solution in which a discotic compound and another compound (for example, a polymerizable monomer and a photopolymerization initiator) are dissolved in a solvent to an orientation film, drying the solution, and then discotic nematic It is obtained by heating to a phase formation temperature, polymerizing (by irradiation with UV light or the like), and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is 70 to 70.
300 ° C is preferable, and 70 to 170 ° C is particularly preferable.

For example, the tilt angle of the discotic unit on the support side can be generally adjusted by selecting a discotic compound or a material of an alignment film, or by selecting a rubbing method. In addition, for the tilt angle of the discotic unit on the surface side (air side), a discotic compound or another compound (eg, a plasticizer, a surfactant, a polymerizable monomer and a polymer) to be used together with the discotic compound is generally selected. Can be adjusted. Further, the degree of change of the inclination angle can be adjusted by the above selection.

The plasticizer, surfactant and polymerizable monomer are compatible with the discotic compound.
Any compound can be used as long as it can change the tilt angle of the liquid crystalline discotic compound or does not hinder the alignment. Among these, a polymerizable monomer (eg, a compound having a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group) is preferable.
The above compounds are generally used in an amount of 1 to 50% by mass (preferably 5 to 30% by mass) based on the discotic compound.

As the polymer, any polymer can be used as long as it has compatibility with the discotic compound and can change the tilt angle of the liquid crystalline discotic compound. Examples of the polymer include a cellulose ester. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropylcellulose and cellulose acetate butyrate. The polymer is generally 0.1 to 10% by mass (preferably 0.1 to 8% by mass, particularly 0.1 to 5% by mass, based on the discotic compound so as not to hinder the alignment of the liquid crystalline discotic compound. ). The butyrylation degree of cellulose acetate butyrate (cellulose acetate butyrate) is preferably 30% or more, particularly preferably in the range of 30 to 80%. The degree of acetylation is 3
0% or more, especially the range of 30 to 80% is preferable. Viscosity of cellulose acetate butyrate (ASTM D-81
7-72) is from 0.01 to
A range of 20 seconds is preferred.

The (color) liquid crystal display device having an optically anisotropic layer (optical compensatory sheet) having a variable inclination angle shown in FIG. Or, there is almost no gradation or coloring of the displayed image.

Further, in the (color) liquid crystal display device of the present invention, the reason why the viewing angle has been expanded to a higher degree is presumed as follows. For example, in the color liquid crystal display device of the present invention, in a normally white mode in which the transmission axes of the polarizer and the analyzer are substantially orthogonal to each other (mode widely used in TN-LCD), a portion in a black display state is provided. Is a state in which a voltage is applied to the liquid crystal, and as the viewing angle is increased, the transmittance of light from the black display portion is significantly increased, causing a sharp decrease in contrast.
In this black display state (when voltage is applied), the liquid crystal molecules inside the TN liquid crystal cell are arranged as shown in FIG.
The TN liquid crystal molecules 33 existing near the substrate surface are
a, and the TN liquid crystal molecules 33 gradually incline and become perpendicular to the surface as the distance from the surface of the substrate 31a increases. Further away from the surface of the substrate 31a, the TN liquid crystal molecules 33 are gradually inclined in the opposite direction, and finally become almost parallel to the surface of the substrate 31b. Therefore, the liquid crystal cell of the TN-LCD in black display has two positive optically anisotropic bodies having optical axes (directions in which Re shows the minimum value) gradually inclined from the cell surface and a liquid crystal cell parallel to the normal of the cell surface. It can be considered as a laminate of two positive optical anisotropic bodies having an optical axis. For this reason, the change in the tilt angle of the discotic structure unit surface of the optically anisotropic layer of the present invention and the negative birefringence compensate for the phase difference generated by the tilt of the liquid crystal molecules inside the TN liquid crystal cell when voltage is applied. be able to. Therefore, a color liquid crystal display device provided with an optically anisotropic layer (optical compensation sheet) having a changing inclination angle can invert a black-and-white image or display a display image even when the display device is viewed obliquely with a large viewing angle. There is almost no gradation or coloring.

The haze of the optically anisotropic layer is generally 5.0.
% Or less. Accordingly, the optically compensatory sheet having the optically anisotropic layer also generally has 5.0% or less because the haze of the transparent support is low. The haze is ASTN-D
1003-52. When the haze of the optically anisotropic layer is high, light leakage which is considered to be caused by scattering occurs in the black display portion, and as a result, the contrast is reduced. This tendency is remarkable when the incident light is inclined in the normal direction and in the upward direction of the image. Therefore, in order to prevent this, the haze is preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. In general, haze means that the surface is rough (fine irregularities, scratches)
Alternatively, it is caused by internal non-uniformity (existence of minute portions having different refractive indexes). In order to reduce the unevenness, the surface of the optical compensatory sheet is smoothed, and the internal refractive index non-uniformity is reduced. It is necessary to make it smaller. The optical compensatory sheet of the present invention has a low haze because the optically anisotropic layer having a smooth surface and a uniform inside is formed. In order to further reduce the haze, for example, it is preferable to form a protective layer or an adhesive layer on the optically anisotropic layer, or to appropriately select conditions for forming the optically anisotropic layer. The smooth surface of the optical compensation sheet or the optically anisotropic layer can be easily obtained as described above.

The compound used as the protective layer is not particularly limited, but is preferably a polymer from the viewpoint of film forming ability, and is preferably soluble in a solvent which does not dissolve the discotic compound. Specific examples of the polymer include water-soluble polymers such as gelatin, methylcellulose, alginic acid, pectin gum arabic, pullulan, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, sodium polyvinylbenzenesulfonate, carrageenan, and polyethylene glycol. The adhesive layer can be provided on the optically anisotropic layer instead of the protective layer.
The adhesive layer is generally formed when the optical compensation sheet is incorporated into a liquid crystal display. The material of the pressure-sensitive adhesive layer is not particularly limited, and a transparent adhesive or pressure-sensitive adhesive such as acrylic, SBR, or silicone rubber can be used. From the viewpoint of preventing the deterioration of the optical characteristics of the constituent members, those which do not require a high-temperature process for curing and drying are preferable, and those which do not require a long curing treatment or drying time are preferable. The smooth surface of the optical compensation sheet can be obtained by applying a coating solution for forming an adhesive layer or a protective layer on the surface of the optically anisotropic layer so as to have a smooth surface, thereby reducing haze. it can. In the present invention, it is preferable to apply an adhesive layer rather than a protective layer from the viewpoint of productivity. The conditions for forming the optically anisotropic layer are appropriately selected depending on the composition containing the discotic compound (combination of discotic compounds, and the types and amounts of other compounds used together). The conditions include a heating temperature or a heating time for forming a discotic nematic layer, a cooling rate after heating, a layer thickness, a coating method, and the like. Further, the discotic compound may form a plurality of different domains depending on the properties of the compound, the conditions for forming the compound, and the like, and this causes haze due to non-uniformity inside the layer. In order to reduce such haze, the discotic compound is converted into a monodomain,
Alternatively, even if a plurality of domains are formed, each domain size is set to 0.1 μm or less, preferably 0.08 μm or less.
When the thickness is not more than μm, it is possible to prevent the visible light from being affected.

The solution for forming the optically anisotropic layer can be prepared by dissolving the discotic compound and the other compound described above in a solvent. Examples of the solvent include polar solvents such as N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO) and pyridine; nonpolar solvents such as benzene and hexane; alkyl halides such as chloroform and dichloromethane; Esters such as methyl and butyl acetate; ketones such as acetone and methyl ethyl ketone; and ethers such as tetrahydrofuran and 1,2-dimethoxyethane. Alkyl halides and ketones are preferred. The solvents may be used alone or in combination.

The solution can be applied by curtain coating, extrusion coating, roll coating,
Examples include dip coating, spin coating, print coating, spray coating and slide coating. In the present invention, in the case of a mixture of only discotic compounds, a vapor deposition method can also be used. In the present invention, continuous coating is preferred. Therefore, curtain coating, extrusion coating, roll coating and slide coating are preferred. As described above, the optically anisotropic layer is obtained by applying the coating solution on the alignment film, drying the coating solution, heating it to a temperature equal to or higher than the glass transition temperature (then, if necessary, hardening), and cooling.

Since the optical compensatory sheet of the present invention compensates for birefringence caused by a liquid crystal cell in a liquid crystal display device, the wavelength dispersion of the optically anisotropic element is preferably equal to that of the liquid crystal cell. That is, the optically anisotropic elements 450 and 55
The retardation due to 0 μm light is R ₄₅₀ , R
If _550, the R ₄₅₀ / R ₅₅₀ value representing the chromatic dispersion,
It is preferably 1.0 or more.

[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. As the other protective film, a normal cellulose acetate film may be used. The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. By using the optical compensation sheet of the present invention as a protective film of the polarizing film, without increasing the number of components of the polarizing plate,
An optical compensation function can be added to the polarizing plate. It is preferable that the slow axis of the cellulose acetate film and the transmission axis of the polarizing film are arranged substantially in parallel. Substantially parallel means within ± 5 ° of the exact angle. This range is preferably less than ± 4 °, more preferably less than ± 3 °, and most preferably less than ± 2 °.

It was also found that the moisture permeability of the protective film was important for the productivity of the polarizing plate. The polarizing film and the protective film are adhered with an aqueous adhesive, and the adhesive solvent is dried by diffusing in the protective film. The higher the moisture permeability of the protective film, the faster the drying and the higher the productivity. The higher the moisture permeability, the more the moisture enters the polarizing film due to the usage environment (high humidity) of the liquid crystal display device. The polarizing ability decreases. Therefore, when the optical compensatory sheet of the present invention is used as a protective film for a polarizing film, the optical compensatory sheet has a moisture permeability of 100.
To 1000 (g / m ² ) / 24 hrs, and preferably 300 to 700 (g / m ² ) / 24 h
More preferably, it is in the range of rs. The moisture permeability of the optical compensation sheet is determined by the thickness, free volume, hydrophilic / hydrophobic property, etc. of the transparent support (and the polymerizable liquid crystal compound).

The thickness of the transparent support can be adjusted by adjusting the flow rate of the lip and the line speed, or the stretching and compression of the film when forming a cellulose acetate film. By adjusting the thickness of the film according to the main material to be used, the moisture permeability can be set in a preferable range. The free volume of the transparent support can be adjusted by the drying temperature and time during film formation. Also in this case, by adjusting the free volume according to the main material to be used, the moisture permeability can be set in a preferable range.
The hydrophilicity / hydrophobicity of the transparent support can be adjusted by additives. By adding a hydrophilic additive to the free volume, the moisture permeability increases, and conversely, by adding a hydrophobic additive, the moisture permeability can be reduced. By adjusting the moisture permeability of the optical compensatory sheet, it becomes possible to manufacture a polarizing plate having optical compensatory ability at low cost and with high productivity.

[Liquid Crystal Display Device] FIG. 3 shows a typical configuration example of the liquid crystal display device of the present invention. In FIG. 3, a liquid crystal cell TNC comprising a pair of substrates provided with transparent electrodes and a twist-aligned nematic liquid crystal sealed between the substrates, a pair of polarizing plates A and B provided on both sides of the liquid crystal cell, and a liquid crystal cell Optical compensatory sheets RF ₁ , RF arranged between
₂ and the backlight BL constitute a liquid crystal display device in combination. Only one optical compensation sheet may be provided (ie, RF ₁ or RF ₂ ). R ₁ indicates the rubbing direction of the optical compensation sheet RF ₁ when viewed from the front, and R ₂ indicates the rubbing direction of the optical compensation sheet RF ₂ . The solid arrow of the liquid crystal cell TNC indicates the rubbing direction of the substrate on the polarizing plate B side of the liquid crystal cell, and the dotted arrow of the liquid crystal cell TNC indicates the rubbing direction of the substrate on the polarizing plate A side of the liquid crystal cell. PA and PB are polarizing plates A and B, respectively.
Represents the polarization axis.

In the liquid crystal display of the present invention, the optical compensation sheet and the liquid crystal cell are preferably arranged as follows. FIG. 4 is a diagram showing the relationship between the direction of the minimum value of the retardation and the rubbing direction of the substrate of the liquid crystal cell.
A pair of polarizing plates 63a and 63b are arranged on both sides of the liquid crystal cell 61, and an optical compensation sheet 62 is arranged between the polarizing plate 63a and the liquid crystal cell 61. The optical compensation sheet is generally arranged so that the optically anisotropic layer is in contact with the surface of the liquid crystal cell. 62M is the direction when the direction of the absolute value of the absolute value of the retardation of the optical compensation sheet 62 is orthogonally projected on the liquid crystal cell. This direction generally corresponds to the rubbing direction of the alignment film of the optical compensation sheet. 61Ra is
Represents the rubbing direction of the upper substrate of the liquid crystal cell 61;
Rb represents the rubbing direction of the lower substrate of the liquid crystal cell 61.

The angle (α) between the direction 62M when the direction of the minimum value of the absolute value of the retardation is orthogonally projected onto the liquid crystal cell and the rubbing direction 61Ra of the upper substrate of the liquid crystal cell is as follows.
It is preferably in the range of 90 to 270 degrees. That is, the angle (α) can be defined as shown in FIG. FIG. 5 is a diagram obtained when FIG. 4 is viewed from the z-axis direction.
In FIG. 5, 61Ra, 61Rb and 62M correspond to FIG.
Is synonymous with The angle (α) indicates the angle between the orthogonal projection direction 62M indicating the minimum value of the retardation and the rubbing direction 61Ra of the upper substrate. This arrangement can be applied to the case where two optical compensation sheets are used. 1
When two optical compensation sheets are used, the orthogonal projection direction 62M indicating the minimum value of the retardation is the main viewing angle direction (when the sheet is provided above the cell) or the opposite viewing angle direction (the sheet). Is provided below the cell)
Is preferred. The main viewing angle direction is the average twist direction of the liquid crystal molecules in the liquid crystal cell.
When it is twisted 90 degrees counterclockwise as viewed from the direction of the z-axis, it is the minus direction of the x-axis. The opposite viewing angle direction is a direction opposite to the main viewing angle direction.

In the liquid crystal display device of the present invention, as shown in FIG. 6, it is preferable that a pair of optical compensation sheets are provided on both sides of the liquid crystal cell. In FIG. 6, a pair of polarizing plates 8
3a and 83b are arranged on both sides of the liquid crystal cell 81, and the optical compensation sheet 82a is
And an optical compensation sheet 82b is disposed between the polarizing plate 83b and the liquid crystal cell 81. 82M
a is the direction when the direction of the minimum absolute value of the retardation of the optical compensation sheet 82a is orthogonally projected onto the liquid crystal cell, and 82Mb is the direction of the minimum value of the absolute value of the retardation of the optical compensation sheet 82b. Is the direction when the image is orthogonally projected on the liquid crystal cell. 81Ra represents the rubbing direction of the upper substrate of the liquid crystal cell 81, and 81Rb represents the rubbing direction of the liquid crystal cell 81.
Represents the rubbing direction of the lower substrate. 84 represents a light source.

The angle (α1) between the direction 82Ma when the direction of the absolute value of the absolute value of the retardation is orthogonally projected onto the liquid crystal cell and the rubbing direction 81Ra of the upper substrate of the liquid crystal cell.
And the angle (α2) between 82Mb and 81Rb is 135 to 135Mb.
It is preferably in the range of 225 degrees. That is, the angles (α1 and α2) can be defined as shown in FIG. FIG. 7 is a diagram obtained when FIG. 6 is viewed from the z-axis direction. 7, 81Ra, 81Rb, 82Ma and 82Mb have the same meaning as in FIG. Angle (α1)
Is the orthogonal projection direction 82M indicating the minimum value of the retardation.
a and the angle between the rubbing direction 81Ra of the upper substrate,
The angle (α2) is the angle between the orthogonal projection direction 82Mb indicating the minimum value of the retardation and the rubbing direction 81Rb of the lower substrate. The angle (β1) between the orthogonal projection directions 82Ma and 82Mb showing the minimum value of the retardation is 90 to 18
A range of 0 degrees is preferred.

In the liquid crystal display device of the present invention, as shown in FIG. 8, two optical compensation sheets may be provided on one side of the liquid crystal cell. In FIG. 8, a pair of polarizing plates 103a,
103b are arranged on both sides of the liquid crystal cell 101, and the optical compensation sheets 102a, 102b are
And the liquid crystal cell 101. 102Ma
Is the direction when the direction of the minimum value of the absolute value of the retardation of the optical compensation sheet 102a is orthogonally projected onto the liquid crystal cell, and 102Mb is the direction of the minimum value of the absolute value of the retardation of the optical compensation sheet 102b. This is the direction when orthographic projection is performed on the liquid crystal cell. 101Ra is the liquid crystal cell 101
Represents the rubbing direction of the upper substrate, and 101Rb represents the rubbing direction of the lower substrate of the liquid crystal cell 101. 10
4 represents a light source.

The angle (α) between the direction 102Ma when the direction of the absolute value of the absolute value of the retardation is orthogonally projected onto the liquid crystal cell and the rubbing direction 101Ra of the upper substrate of the liquid crystal cell.
3) It is preferably in the range of 135 to 225 degrees, and 1
The angle (α4) between 02Mb and 101Rb is −45 to 4
It is preferably in the range of 5 degrees. That is, the angle (α3
And α4) can be defined as shown in FIG. FIG.
FIG. 9 is a diagram obtained when FIG. 8 is viewed from the z-axis direction. 9, 101Ra, 101Rb, 102Ma, and 102Mb have the same meaning as in FIG. Angle (α3)
Is the orthogonal projection direction 102 indicating the minimum value of the retardation.
Ma is the angle between the rubbing direction 101Ra of the upper substrate and the angle (α4) is the orthographic projection direction 102Mb showing the minimum value of the retardation and the rubbing direction 101R of the lower substrate.
This is the angle with b. Angle (β1) between the orthogonal projection directions 102Ma and 102Mb indicating the minimum value of the retardation
Is preferably in the range of 0 to 120 degrees.

The relationship between the minimum retardation direction and the rubbing direction of the liquid crystal cell substrate can be applied to a color liquid crystal display device. FIG. 10 shows a typical configuration example of the color liquid crystal display device of the present invention. In FIG. 10, a glass substrate 124a provided with a counter transparent electrode 122 and a color filter 125, a pixel electrode 123 and a TFT 126
, A liquid crystal cell including a twisted-aligned nematic liquid crystal 121 sealed between the two substrates, and a pair of polarizing plates 1 provided on both sides of the liquid crystal cell.
28a, 128b and a pair of optical compensatory sheets 127a, 127b disposed between the liquid crystal cell and the polarizing plate constitute a color liquid crystal display device in combination. Only one optical compensatory sheet may be provided (ie, 127).
a or 127b).

As the color filter used in the color liquid crystal display device of the present invention, any color filters having high color purity, high dimensional accuracy and high heat resistance can be used. Preferred examples include a dyeing filter, a printing filter, an electrodeposition filter, and a pigment dispersion filter. These are described in "Color LCD Display" edited by Shunsuke Kobayashi (Sangyo Tosho, 172-173).
Pages 237 to 251) or “Flat Panel Display 1994” edited by Nikkei Microdevice (Nikkei BP, page 216). For example, a dyeing filter can be obtained by adding a dichromate to a substrate such as gelatin, casein, or PVA to impart photosensitivity, patterning the substrate by a fatrigrafy method, and then dyeing it.

The liquid crystal used in the (color) liquid crystal display device of the present invention is, for example, “Liquid Crystal Device Handbook” edited by the 142nd Committee of the Japan Society for the Promotion of Science (Nikkan Kogyo Shimbun,
Nematic liquid crystals described on pages 107 to 213) are preferred. The liquid crystal cell is preferably of a TN mode or an OCB mode. In the case of the TN mode, the major axis of the liquid crystal molecules is twisted at approximately 90 ° C. between the upper and lower substrates of the liquid crystal cell. When there is no applied electric field, the polarization direction is changed by 90 ° C. due to the optical rotation of the liquid crystal cell, and the light is emitted from the liquid crystal cell. When a sufficiently high electric field higher than the threshold value is applied, the long axis of the liquid crystal molecules changes in the direction of the electric field and is arranged perpendicular to the electrode surface, so that the optical rotation almost disappears. Therefore, in order to sufficiently exhibit the effect of the optical rotation, the twist angle is preferably from 70 to 100 ° C, more preferably from 80 to 90 ° C.

In order to reduce defects (disclination) in the alignment of liquid crystal molecules due to the electric field, it is preferable to give a pretilt angle to the liquid crystal molecules in advance. The pretilt angle is preferably 5 ° C or less, and more preferably 2 ° C to 4 ° C.
Is preferred. For the above twist angle and pretilt angle, see “Liquid Crystal Application” edited by Koji Okano and Shunsuke Kobayashi (Baifukan,
Pages 16 to 28). In the case of the OCB mode, the OCB mode liquid crystal cell is a liquid crystal using a bend alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned (symmetrically) in substantially opposite directions at the upper and lower portions of the liquid crystal cell. A display device, which is disclosed in U.S. Pat.
No. 10422 is disclosed in each specification. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is OCB (Option
Also called liquid crystal mode.
The bend alignment mode liquid crystal display device has an advantage that the response speed is high.

The value of the product (Δn · d) of the refractive index anisotropy Δn of the liquid crystal cell and the thickness d of the liquid crystal layer in the liquid crystal cell is described in, for example, “Liquid crystal device” edited by the 142nd Committee of the Japan Society for the Promotion of Science. Handbook ”(Nikkan Kogyo Shimbun, pp. 329-33)
As described in (p. 7), as d increases, the contrast is improved, but the response speed is slow and the viewing angle is also small. Therefore, the range of 0.3 to 1.0 μm is preferable. The range of 3 to 0.6 μm is more preferable.

Signals applied to the color liquid crystal display device of the present invention are described in, for example, “Liquid Crystal Device Handbook” edited by the 142nd Committee of the Japan Society for the Promotion of Science (Nikkan Kogyo Shimbun, p.
465 pages) or Koji Okano and Shunsuke Kobayashi, "Liquid Crystals"
As described in “Applied Edition” (Baifukan, pp. 85-105), etc., the alternating current of 5-100 Hz and the voltage of 20
V or less, preferably 8 V or less. For example, in the normally white mode, the applied voltage is 0 to 1.5 V
For bright display, 1.5V to 3.0V for halftone display, 3.0V
The dark display is generally performed as described above.

The material of the polarizing plate that can be used in the color liquid crystal display device and the liquid crystal display device of the present invention is not particularly limited, and any material can be used. Generally, a polarizing plate comprises a polarizer and protective films provided on both sides thereof. The polarizer is obtained, for example, by treating a hydrophilic polymer such as stretched polyvinyl alcohol with iodine or a dye.

In the above description of the liquid crystal display device, an example was shown in which an optical compensation sheet was disposed between a commercially available polarizing plate and a liquid crystal cell. The polarizing plate of the present invention in which an optical compensation sheet and a polarizing film are laminated can be used in place of the commercially available polarizing plate and optical compensation sheet of the above-described liquid crystal display device. In this case, the components of the liquid crystal display device (in the above example, the protective film between the liquid crystal cell and the polarizing film of the polarizing plate) can be reduced, the thickness of the liquid crystal display device can be reduced, and the manufacturing cost can be reduced. Can be lowered.

[0117]

EXAMPLES Example 1 The following composition was put into a mixing tank, and stirred while heating to dissolve each component.
A cellulose acetate solution was prepared.

<< 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 ────────────────────────────────

In a separate 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 retardation increasing agent solution.
25 parts by mass of a retardation increasing solution was mixed with 474 parts by mass of the cellulose acetate solution, and the mixture was sufficiently stirred to prepare a dope. The addition amount of the retardation enhancer
It was 3.5 parts by mass with respect to 100 parts by mass of cellulose acetate.

[0120]

Embedded image

The obtained dope was cast using a band casting machine. After the film surface temperature on the band reached 40 ° C., the film was dried with a drying air at 60 ° C. for 1 minute and peeled off.
After drying for 10 minutes with a drying air at 0 ° C., a cellulose acetate film having a residual solvent amount of 0.3% by mass (thickness: 50 μm)
m) was prepared. About the produced cellulose acetate film (CAF-01), an ellipsometer (M-
150, manufactured by JASCO Corporation, at a wavelength of 550 nm.
And the Re retardation value and Rth retardation value were measured. The results are shown in Table 1. After immersing the prepared cellulose acetate film in a 2.0 N potassium hydroxide solution (25 ° C.) for 2 minutes, neutralized with sulfuric acid,
Washed with pure water and dried. When the surface energy of this cellulose acetate film was determined by the contact angle method,
It was 63 mN / m. A coating solution having the following composition was applied to the cellulose acetate film using a # 16 wire bar coater at 28 ml / m ² . 6 with 60 ° C warm air
It dried for 0 second, and also for 150 second with 90 degreeC warm air. next,
A rubbing treatment was performed on the formed film in a direction parallel to the longitudinal direction of the cellulose acetate film.

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

[0123]

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(Formation of Optically Anisotropic Layer) The following discotic (discotic) liquid crystal compound 41.01 was formed on the alignment film.
g, ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.)
4.06 g, cellulose acetate butyrate (CAB)
551-0.2, manufactured by Eastman Chemical Company) 0.90
g, cellulose acetate butyrate (CAB531-
1. Eastman Chemical Co., Ltd.) 0.23 g, photopolymerization initiator (Irgacure 907, Ciba-Geigy).
A coating solution prepared by dissolving 35 g of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) in 102 g of methyl ethyl ketone was applied using a # 3.6 wire bar. This was heated in a constant temperature zone of 130 ° C. for 2 minutes to orient the discotic compound. Next, in an atmosphere of 60 ° C.,
UV irradiation was performed for 5 seconds using a 20 W / cm high pressure mercury lamp to polymerize the discotic compound. Then, it was left to cool to room temperature.
Thus, an optically anisotropic layer was formed, and an optical compensation sheet (KH-01) was produced. The Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm was 43 nm. The angle (tilt angle) between the disk surface and the transparent support surface (cellulose acetate film surface) was 42 ° on average.

[0125]

Embedded image

The obtained optical compensatory sheet of the present invention (KH-
01) was cut along the depth in the rubbing direction using a microtome to produce an extremely thin film (sample). This sample was left to stand in an atmosphere of OsO ₄ for 48 hours and stained. The obtained stained film was observed with a transmission electron microscope (TEM) to obtain a micrograph thereof. In the stained film, the acryloyl group of the discotic (liquid crystalline) compound was stained and recognized as an image of a photograph. From this photograph, the discotic compound of the optically anisotropic layer is inclined from the surface of the transparent support, and the angle of inclination is 5 to 5 with increasing distance in the depth direction from the bottom of the optically anisotropic layer.
A continuous increase over 75 degrees was observed.

[Example 2] First, a cellulose triacetate solution having the following composition was prepared. Cellulose triacetate powder (average size: 2 mm) was gradually added to a solution in which the following solvents were previously mixed, with good stirring. After the addition, the mixture was left at room temperature (25 ° C.) for 3 hours. After cooling the obtained heterogeneous gel-like solution at -70 ° C for 6 hours, 5
The mixture was heated to 0 ° C and stirred to obtain a cellulose triacetate solution.組成 Composition of cellulose triacetate solution ──────────セ ル ロ ー ス 20 parts by mass of cellulose triacetate (average degree of acetylation 60.5%, viscosity average degree of polymerization 300) methyl acetate 48 Parts by mass cyclohexanone 20 parts by mass methanol 5 parts by mass ethanol 5 parts by mass triphenylphosphate / biphenyldiphenylphosphate (mass ratio: 1/2) 2 parts by mass silica (particle size 20 nm) 0.1 parts by mass 2,4-bis 0.2 parts by mass of-(n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine ────────────────── ────

In another mixing tank, 16 parts by mass of the retardation increasing agent used in Example 1, 80 parts by mass of methylene chloride and 20 parts by mass of methanol were charged.
The mixture was stirred while heating to prepare a retardation increasing agent solution. 25 parts by mass of a retardation increasing solution was mixed with 474 parts by mass of the cellulose acetate solution, and the mixture was sufficiently stirred to prepare a dope. The addition amount of the retardation increasing agent was 3.5 parts by mass with respect to 100 parts by mass of cellulose acetate. Next, the obtained dope was
At 0 ° C., the solution was filtered with a filter paper (# 63, manufactured by Toyo Roshi Kaisha Ltd.) having an absolute filtration accuracy of 0.01 mm.
The mixture was filtered with a 025 mm filter paper (FH025, manufactured by Pall Corporation).

The dope obtained was cast using a band casting machine. After the film surface temperature on the band reached 40 ° C., the film was dried with a drying air at 60 ° C. for 1 minute and peeled off.
After drying for 10 minutes in a drying air at 0 ° C., a cellulose acetate film having a residual solvent amount of 0.3% by mass (thickness: 70 μm)
m) was prepared. About the produced cellulose acetate film (CAF-02), an ellipsometer (M-
150, manufactured by JASCO Corporation, at a wavelength of 550 nm.
And the Re retardation value and Rth retardation value were measured. The results are shown in Table 1. The prepared cellulose acetate film was immersed in a 1.5 N potassium hydroxide solution (25 ° C.) for 30 seconds, and then washed with pure water.
Dried. When the surface energy of this cellulose acetate film was determined by the contact angle method, it was 58 mN / m
Met. An alignment film was provided on the cellulose acetate film in the same manner as in Example 1, and an optically anisotropic layer was provided in the same manner as in Example 1 except that a coating solution having the following composition was used. -02).

<< Composition of Optical Anisotropic Layer Coating Solution >>円 Discotic liquid crystalline compound used in Example 1 36.00 parts by mass ethylene oxide Modified acrylate (M101) 9.00 parts by mass Cellulose acetate butyrate (CAB551-0.2) 0.90 parts by mass Cellulose acetate butyrate (CAB531-1.0) 0.23 parts by mass Photopolymerization initiator (Irgacure 907) 1.35 parts by mass Sensitizer (Kayacure DETX) 0.45 parts by mass Methyl ethyl ketone 102.00 parts by mass ──────────

When the optically anisotropic layer was observed by a transmission electron microscope in the same manner as in Example 1, the discotic compound in the optically anisotropic layer was tilted from the surface of the transparent support, and the tilt angle was changed. Was continuously increased from 20 to 50 degrees with an increase in the distance in the depth direction from the bottom of the optically anisotropic layer.

Example 3 A cellulose acetate solution (dope) for an inner layer having the following composition was prepared. The adjustment of the dope was performed as follows. First, a cellulose triacetate powder (average size: 2 mm) was gradually added to a solution in which the following solvents were previously mixed, with sufficient stirring. The resulting solution was left at room temperature (25 ° C.) for 3 hours. Next, this heterogeneous gel-like solution is placed in a stainless steel closed container for 1 hour.
After heating at 180 ° C. for 5 minutes at MPa, the whole container was put into a 50 ° C. water bath and cooled to obtain a 50 ° C. solution. Then 5
At 0 ° C., the resulting solution is filtered with an absolute filtration accuracy of 0.01 mm
(# 63, manufactured by Toyo Roshi Kaisha, Ltd.). Thus, an inner layer cellulose acetate solution (inner layer dope) was prepared. The viscosity of the dope at 45 ° C.
It was 160 Pa · S.

<< Composition of Cellulose Acetate Solution for Inner Layer >>セ ル ロ ー ス Cellulose triacetate with 59.5% acetylation 20 parts by weight 2 parts by weight sorbitol hexaacetate Methyl acetate 48 parts by mass Cyclohexanone 20 parts by mass Methanol 5 parts by mass Ethanol 5 parts by mass Silica (particle diameter 20 nm) 0.1 part by mass 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5 -Di-tert-butylanilino) -1,3,5-triazine 0.2 part by mass ──────

A filter having the following composition was used for filtering the solution.
A cellulose acetate solution for a surface layer (a dope for a surface layer) was prepared in the same manner as in the cellulose acetate solution for an inner layer except for using. The viscosity of the dope at 45 ° C.
It was 110 Pa · S.

<< Composition of Cellulose Acetate Solution for Surface Layer >>セ ル ロ ー ス 19 parts by weight of cellulose triacetate having a degree of acetylation of 59.5% 2 parts by weight of sorbitol hexaacetate Parts Methyl acetate 49 parts by weight Cyclohexanone 20 parts by weight Methanol 5 parts by weight Ethanol 5 parts by weight Silica (particle size 20 nm) 0.1 parts by weight 2,4-bis- (n-octylthio) -6- (4-hydroxy-3, 5-di-tert-butylanilino) -1,3,5-triazine 0.2 part by mass ───────

In another mixing tank, 16 parts by mass of the retardation increasing agent used in Example 1, 80 parts by mass of methylene chloride and 20 parts by mass of methanol were charged.
The mixture was stirred while heating to prepare a retardation increasing agent solution.

25 parts by mass of a retardation increasing solution was mixed with 474 parts by mass of the cellulose acetate solution for the inner layer, and the mixture was sufficiently stirred to prepare a dope. The addition amount of the retardation increasing agent was 3.6 parts by mass with respect to 100 parts by mass of cellulose acetate. 25 parts by mass of the retardation increasing solution was mixed with 474 parts by mass of the cellulose acetate solution for the surface layer, and the mixture was sufficiently stirred to prepare a dope. The addition amount of the retardation increasing agent was 3.8 parts by mass with respect to 100 parts by mass of cellulose acetate.

Using a three-layer co-casting die, the inner layer dope was set inside and the surface layer dope was set on both outer sides of the inner layer dope. After the three layers of dope are simultaneously discharged onto a metal support and cast in a multi-layer manner, the casting film is peeled off from the support, dried, and a cellulose acetate film having a three-layer structure (inner layer thickness: 80 μm, Thickness of each surface layer: 10
μm). After drying the cast dope at 70 ° C. for 3 minutes and 130 ° C. for 5 minutes, the film was peeled off from the metal support and dried at 160 ° C. for 30 minutes to evaporate the solvent. The residual solvent amount of the film after drying was 0.3% by mass.

The prepared cellulose acetate film (CAF-03) was subjected to an ellipsometer (M-1).
50, manufactured by JASCO Corporation, the Re retardation value and the Rth retardation value at a wavelength of 550 nm were measured. The results are shown in Table 1. The prepared cellulose acetate film was immersed in a 1.5 N sodium hydroxide solution (25 ° C.) for 30 seconds, and then washed with pure water.
Dried. When the surface energy of this cellulose acetate film was determined by the contact angle method, it was 55 mN / m
Met. An alignment film was provided on the cellulose acetate film in the same manner as in Example 1, and an optically anisotropic layer was provided in the same manner as in Example 1 except that a coating solution having the following composition was used. -03).

<< Composition of Optical Anisotropic Layer Coating Solution >>円 Discotic liquid crystalline compound used in Example 1 45.00 parts by mass Cellulose acetate Butyrate (CAB551-0.2) 0.90 parts by mass Cellulose acetate butyrate (CAB531-1.0) 0.23 parts by mass Photopolymerization initiator (Irgacure 907) 1.35 parts by mass Sensitizer (Kayacure DETX) ) 0.45 parts by mass Methyl ethyl ketone 102.00 parts by mass

With respect to the thus obtained optical compensation sheet (KH-03) of the present invention, the Re retardation value from any direction on the surface including the rubbing axis and perpendicular to the optical compensation sheet surface was measured using an ellipsometer (AEP). -1
00; manufactured by Shimadzu Corporation), and the optical properties of the support after removing the discotic compound in the measurement portion were also measured in the same manner. As a result of these measurements, the optical characteristics of the optically anisotropic layer (the relationship between Re and the measurement angle) are as shown in FIG. When the result of FIG. 11 is simulated, the obtained optically anisotropic layer has negative birefringence, and the surface of the discotic compound is inclined from the support surface, and the inclination (tilt angle) is from 20 degrees. It turned out that it changes continuously to 40 degrees.

[0142]

[Table 1] Table 1 { Film Re Rth } ──────────────────────────────── Example 1 CAF-01 7 nm 80 nm Example 2 CAF-02 5 nm 75 nm Example 3 CAF-03 12 nm 100 nm ────────────────────────────────────

(Evaluation of Optical Compensation Sheet) The optical characteristics and surface condition of the optical compensation sheets obtained in Examples 1 to 3 were evaluated as follows. The results are shown in Table 2. (1) Optical Characteristics For the optical compensation sheets of Examples 1 to 3, the Re retardation values from all directions on the surface including the rubbing axis and perpendicular to the optical compensation sheet surface were measured using an ellipsometer (A).
(EP-100; manufactured by Shimadzu Corporation), and the direction in which the Re retardation value was minimized was determined. The results are shown in Table 2. Table 2 shows the change in the inclination angle between the discotic compound surface and the support surface measured in the examples. (2) Film surface state The film was visually observed, and the surface state was evaluated as follows. A: The film surface is smooth. B: The film surface is smooth, but some foreign matter is observed. C: Weak irregularities are seen on the film surface, and the presence of foreign matter is clearly observed. D: Irregularities are seen on the film, and many foreign matters are seen.

[0144]

[Table 2] Table ──────────────────────────────────── Sheet inclination angle Re minimum direction No . Change (degrees) angle (degrees) planar ──────────────────────────────────── Example 1 KH -01 5-75 30 C Example 2 KH-02 20-50 35 A Example 3 KH-03 20-40 40 A ───────────────────── ───────────────

Example 4 Iodine was adsorbed on a stretched polyvinyl alcohol film to produce a polarizing film. On one side of the polarizing film, the optical compensation sheet (K
H-01) was attached using a polyvinyl alcohol-based adhesive such that the transparent support (CAF-01) was on the polarizing film side. On the other side of the polarizing film, a commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to a saponification treatment, and was adhered using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the optical compensation sheet (KH-01) were arranged in parallel. Thus, a polarizing plate was produced.

Example 5 Iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizing film. On one side of the polarizing film, the optical compensation sheet (K
H-02) was attached using a polyvinyl alcohol-based adhesive such that the transparent support (CAF-02) was on the polarizing film side. On the other side of the polarizing film, a commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to a saponification treatment, and was adhered using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the optical compensation sheet (KH-02) were arranged in parallel. Thus, a polarizing plate was produced.

Example 6 Iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizing film. On one side of the polarizing film, the optical compensation sheet (K
H-03) was attached using a polyvinyl alcohol-based adhesive so that the transparent support (CAF-03) was on the polarizing film side. On the other side of the polarizing film, a commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to a saponification treatment, and was adhered using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the optical compensation sheet (KH-03) were arranged in parallel. Thus, a polarizing plate was produced.

[Example 7] A pair of polarizing plates provided in a liquid crystal display device (6E-A3, manufactured by Sharp Corporation) using a TN type liquid crystal cell was peeled off, and the polarized light produced in Example 4 was used instead. The plates were adhered one by one to the observer side and the backlight side via an adhesive so that the optical compensation sheet (KH-01) was on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged to be orthogonal to each other. About the manufactured liquid crystal display device,
The viewing angle was measured in eight stages from black display (L1) to white display (L8) using a measuring machine (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 3.

[Example 8] A pair of polarizing plates provided in a liquid crystal display device (6E-A3, manufactured by Sharp Corporation) using a TN type liquid crystal cell was peeled off, and the polarized light produced in Example 5 was used instead. The plates were adhered one by one to the observer side and the backlight side via an adhesive so that the optical compensation sheet (KH-02) was on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged to be orthogonal to each other. About the manufactured liquid crystal display device,
The viewing angle was measured in eight stages from black display (L1) to white display (L8) using a measuring machine (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 3.

Example 9 A pair of polarizing plates provided in a liquid crystal display device (6E-A3, manufactured by Sharp Corp.) using a TN type liquid crystal cell was peeled off, and the polarized light produced in Example 6 was used instead. The plates were adhered one by one to the observer side and the backlight side via an adhesive so that the optical compensation sheet (KH-03) was on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged to be orthogonal to each other. About the manufactured liquid crystal display device,
The viewing angle was measured in eight stages from black display (L1) to white display (L8) using a measuring machine (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 3.

[Comparative Example 2] A liquid crystal display (6E-A3, manufactured by Sharp Corporation) using a TN type liquid crystal cell was displayed in black (L1) using a measuring machine (EZ-Contrast 160D, manufactured by ELDIM). ) To white display (L8), the viewing angle was measured in eight steps. The results are shown in Table 3.

[0152]

[Table 3] Table 3 視野 Liquid crystal viewing angle (contrast ratio ≧ 10: range without grayscale inversion) Display device Upper Lower Left / Right ──────────────────────────────────── Example 7 70 ゜ 45 ゜ 160 ゜ Example 8 75 ゜ 45 ゜ 160 ゜ Example 9 30 ゜ 55 ゜ 120 ゜ Comparative Example 2 15 ゜ 25 ゜ 37 ゜────────────────────── (Note) Black side gradation inversion: Inversion between L1 and L2

Example 10 The following composition was placed in a mixing tank, and each component was cooled and dissolved (−70 ° C.) to prepare a cellulose acetate solution.

──────────────────────────────────── cellulose triacetate (degree of substitution 2.82, viscosity average Polymerization degree 320, water content 0.4% by mass, viscosity of 6% by mass in methylene chloride solution, viscosity 305 mPa · s, powder having an average particle diameter of 1.5 mm and a standard deviation of 0.5 mm) 20 parts by mass Methyl acetate 58 Parts by mass acetone 5 parts by mass methanol 5 parts by mass ethanol 5 parts by mass butanol 5 parts by mass plasticizer A (ditrimethylolpropanetetraacetate) 1.2 parts by mass plasticizer B (triphenyl phosphate) 1.2 parts by mass UV agent a 0.2 parts by mass of (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5 triazine) UV agent b (2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole) 0.2 parts by mass UV agent c (2 (2′-hydroxy-3 ′, 5′-di- tert- amyl phenyl) -5-chloro-benzotriazole) 0.2 part by weight _{C 12 H 25 OCH 2 CH 2} O-P (= O) - (OK) 2 ( releasing agent) 0.02 part by weight of citric acid (peeling Agent) 0.02 parts by mass Fine particles (silica (particle diameter 20 nm), Mohs hardness about 7) 0.05 parts by mass ──────────────────────── ────────────

The cellulose triacetate used here had an acetylation degree of 60.9%, the residual acetic acid content was 0.01% by mass or less, Ca was 0.05% by mass, and Mg was 0.0% by mass.
07% by mass, and Fe was 5 ppm. The acetyl group at the 6-position is 0.95, which is 3% of the total acetyl.
2.2%. The acetone extractables were 11% by mass, the ratio between the weight average molecular weight and the number average molecular weight was 0.5, and the distribution was uniform. The yellowness index was 0.3, the haze was 0.08, the transparency was 93.5%, the Tg was 160 ° C., and the heat of crystallization was 6.2 J / g. In the same manner as in Example 1, the retardation increasing agent was adjusted so as to be 4.0 parts by mass with respect to 100 parts by mass of cellulose acetate, thereby producing a cellulose acetate film (CAF-04). Hereinafter, the surface treatment (saponification), the alignment film, and the optically anisotropic layer are described in Example 1.
An optical compensation sheet (KH-04) was produced in exactly the same manner as described above. The prepared cellulose acetate film (CAF
-04), the optical characteristics were measured. The results are shown in Table 4.

[0156]

TABLE 4 Film Retardation Elevator Re Rth Example 10 CAF-04 4.0 parts by mass 5 nm 85 nm ───────────────────────────────────

(Evaluation of Optical Compensation Sheet) The optical characteristics and surface state of the optical compensation sheet obtained in Example 10 were evaluated in the same manner as in Examples 1 to 3. The results are shown in Table 5.

[0158]

[Table 5] Table ──────────────────────────────────── Sheet inclination angle Re minimum direction No . Change (degrees) angle (degrees) planar ──────────────────────────────────── Example 10 KH −04 5-75 30 A ────────────────────────────────────

Example 11 Example 4 was repeated except that the optical compensation sheet (KH-04) produced in Example 10 was used.
A polarizing plate was produced in the same manner as described above.

Example 12 A liquid crystal display device was manufactured in the same manner as in Example 7, except that the polarizing plate manufactured in Example 11 was used. The viewing angle of the prepared liquid crystal display device was measured in eight stages from black display (L1) to white display (L8) using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 6.

[0161]

Table 6 Table 6 ──────────────────────────────────── Liquid crystal viewing angle (contrast ratio Range of 10 or more without gradation inversion on the black side) Display device Upper Lower Left / Right ──────────────────────────────── ──── Example 12 78 ゜ 43 ゜ 160 ゜ ( Note) Black side tone inversion: Inversion between L1 and L2

[0162]

[Brief description of the drawings]

FIG. 1 is a diagram showing a typical structure of an optically anisotropic layer of the present invention.

FIG. 2 is a diagram showing a typical structure of a liquid crystal layer of a liquid crystal display device.

FIG. 3 is a diagram showing a typical structure of a liquid crystal display device of the present invention.

FIG. 4 is a diagram illustrating a relationship between a direction of a minimum value of retardation and a rubbing direction of a substrate of a liquid crystal cell in a liquid crystal display device using an optical compensation sheet.

FIG. 5 is a diagram obtained when FIG. 4 is viewed from the z-axis direction.

FIG. 6 is a diagram illustrating a relationship between a direction of a minimum value of retardation and a rubbing direction of a substrate of a liquid crystal cell in a liquid crystal display device using a pair of optical compensation sheets.

FIG. 7 is a diagram obtained when FIG. 6 is viewed from the z-axis direction.

FIG. 8 is a diagram showing a relationship between a direction of a minimum value of retardation and a rubbing direction of a substrate of a liquid crystal cell in a liquid crystal display device using two laminated optical compensation sheets.

FIG. 9 is a diagram obtained when FIG. 8 is viewed from the z-axis direction.

FIG. 10 is a diagram showing a typical structure of a color liquid crystal display device of the present invention.

FIG. 11 is an optical compensation sheet (KH-) of the present invention.
It is a graph which shows the relationship of Re of the optically anisotropic layer of 03), and a viewing angle.

[Explanation of symbols]

21, 41 Transparent support 22, 42 Orientation film 23, 43 Optically anisotropic layer 23a, 23b, 23c Liquid crystalline discotic compound Pa, Pb, Pc Surface of discotic structural unit 21a, 21b, 21c Surface of transparent support 21 Θa, θb, θc Inclination angle 24 Normal line of transparent support 31a, 31b Substrate 33 TN liquid crystal molecules

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/1335 510 G02F 1/1335 510 1/13363 1/13363 F term (Reference) 2H049 BA02 BA06 BA42 BA42 BB03 BB33 BB49 BC04 BC09 BC22 2H091 FA02Y FA08X FA08Z FA11X FB02 FB12 GA13 KA10 LA04 LA11 4F006 AA02 AB64 BA00 DA04 4F071 AA09 AC10 AC10 AC12 AF29Y AF31Y BB02 BC01 4J002 AB021 EH126 EL076 EQ016 EU026

Claims (12)

[Claims] 1. A transparent support comprising an optically anisotropic layer provided thereon, wherein the transparent support has a Re retardation value defined by the following formula (I) in the range of 0 to 20 nm. An optically anisotropic layer having a negative birefringence comprising a compound having a discotic structural unit, wherein the Rth retardation value defined by the formula (II) is in the range of 70 to 400 nm; Optical compensation characterized in that the disc surface is inclined with respect to the transparent support surface and the angle between the disc surface of the discotic structure unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. Sheet: (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 plane of the transparent support] Yes; y is fast-axis refractive index of the transparent support in the body surface; nz is a refractive index thickness direction of the transparent support; and, d is the thickness of the transparent support. 2. The transparent support having an acetylation degree of 59.0.
To 61.5% of cellulose acetate, and 100 parts by mass of cellulose acetate, 0.01% of an aromatic compound having at least two aromatic rings.
2. The optical compensatory sheet according to claim 1, wherein the optical compensatory sheet comprises a cellulose acetate film containing from 20 to 20 parts by mass. 3. The cellulose acetate film is a film formed by a solution casting method, and the solvent used for the film formation is ether having 3 to 12 carbon atoms, ketone having 3 to 12 carbon atoms, or carbon The optical compensatory sheet according to claim 2, wherein the ester is an ester represented by Formulas 3 to 12. 4. The cellulose acetate film according to claim 1,
4. The optical compensation sheet according to claim 2, wherein the degree of substitution of the hydroxyl group at the 6-position is mainly composed of cellulose acetate as compared with the 2- and 3-positions. 5. 5. The optical compensatory sheet according to claim 2, wherein the cellulose acetate film is a film formed by a co-casting method. 6. An alignment film is formed between the optically anisotropic layer and the transparent support.
4. The optical compensation sheet according to item 1. 7. The optical compensatory sheet according to claim 6, wherein the alignment film comprises a cured polymer film. 8. 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 an acetylation degree in the range of 59.0 to 61.5%. Certain cellulose acetate and cellulose acetate 10
An aromatic compound having at least two aromatic rings with respect to 0 parts by mass is comprised of 0.01 to 20 parts by mass of a cellulose acetate-containing film and an optically anisotropic layer provided thereon. Formula (I)
Re retardation value defined by 0 to 20
Rth in the range of nm and defined by the following formula (II):
The retardation value is in the range of 70 to 400 nm, the optically anisotropic layer is a layer having a negative birefringence made of a compound having a discotic structural unit, and the disc surface of the discotic structural unit is on a cellulose acetate film surface. A polarizing plate which is inclined with respect to each other and has an angle formed between the disc surface of the discotic structure unit and the cellulose acetate film surface in the depth direction of the optically anisotropic layer: (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 film plane] Refractive index in the fast axis direction; nz is the refractive index in the film thickness direction; and d is the film thickness]. 9. A liquid crystal cell comprising a pair of substrates with a transparent electrode and a twisted nematic liquid crystal sealed between the substrates, a pair of polarizing plates provided on both sides of the liquid crystal cell, and a liquid crystal cell and polarized light. In a liquid crystal display device comprising an optical compensation sheet provided between a transparent support and an optically anisotropic layer provided thereon, the optical compensation sheet is formed by the following formula (I). Re defined
The retardation value is in the range of 0 to 20 nm, the Rth retardation value defined by the following formula (II) is in the range of 70 to 400 nm, and the optically anisotropic layer is formed of a compound having a discotic structural unit. A layer having birefringence, wherein the disc surface of the discotic structure unit is inclined with respect to the transparent support surface, and the angle formed between the disc surface of the discotic structure unit and the transparent support surface is the depth of the optically anisotropic layer. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d [where nx is: Ny is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support in the plane of the transparent support; and d is transparent A thickness of the lifting body. 10. A liquid crystal cell comprising a pair of substrates having a transparent electrode and a twisted nematic liquid crystal sealed between the substrates, and a pair of polarizing plates provided on both sides of the liquid crystal cell. In a liquid crystal display device comprising a polarizing film and two transparent protective films disposed on both sides thereof, at least one of the two transparent protective films disposed between the liquid crystal cell and the polarizing film has a transparent support. And an optically anisotropic layer provided thereon, wherein the transparent support has a Re retardation value defined by the following formula (I) in the range of 0 to 20 nm and defined by the following formula (II). An optically anisotropic layer having a Rth retardation value in the range of 70 to 400 nm, a layer having a negative birefringence comprising a compound having a discotic structural unit, and A liquid crystal display characterized in that the disk surface is inclined with respect to the transparent support surface and the angle between the disk surface of the discotic structure unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. Apparatus: (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 plane of the transparent support] Yes; ny is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support; and d is the thickness of the transparent support]. 11. A liquid crystal cell comprising a pair of substrates having a transparent electrode, a pixel electrode and a color filter, and a twisted nematic liquid crystal sealed between the substrates, and a pair of polarizing plates provided on both sides of the liquid crystal cell. In a color liquid crystal display device comprising an optical compensation sheet provided between a liquid crystal cell and a polarizing plate, the optical compensation sheet comprises a transparent support and an optically anisotropic layer provided thereon, The Re retardation value defined by the following formula (I) is in the range of 0 to 20 nm, and the Rth retardation value defined by the following formula (II) is 70 to 40.
0 nm, and the optically anisotropic layer is a layer having a negative birefringence made of a compound having a discotic structural unit, wherein the disc surface of the discotic structural unit is inclined with respect to the transparent support surface and A liquid crystal display device characterized in that the angle between the disk surface of the tick structure unit and the transparent support surface changes in the depth direction of the optically anisotropic layer: (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 plane of the transparent support; ny is the refractive index in the fast axis direction in the plane of the transparent support] Nz is the refractive index in the thickness direction of the transparent support; and d is the thickness of the transparent support]. 12. A liquid crystal cell comprising a pair of substrates each having a transparent electrode, a pixel electrode and a color filter, and a twisted nematic liquid crystal sealed between the substrates, and a pair of polarizing plates provided on both sides of the liquid crystal cell. In a color liquid crystal display device in which a polarizing plate comprises a polarizing film and two transparent protective films disposed on both sides of the polarizing film, of the two transparent protective films disposed between the liquid crystal cell and the polarizing film, At least one of the transparent support and the optically anisotropic layer provided thereon has a Re retardation value defined by the following formula (I) in the range of 0 to 20 nm. The Rth retardation value defined by (II) is in the range of 70 to 400 nm, and the optically anisotropic layer has a negative birefringence comprising a compound having a discotic structural unit. The disc surface of the discotic structure unit is inclined with respect to the transparent support surface, and the angle between the disc surface of the discotic structure unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d [where nx is in the plane of the transparent support] Ny is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support; and d is the transparent index of the transparent support. Support thickness].