JPH0850206A - Optical compensation sheet, liquid crystal display device and color liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide an optical compensation sheet, liquid crystal display device and color liquid crystal display device which are easily producible and are enlarged in visual field angle. CONSTITUTION:The optically anisotropic layer 23 of the optical compensation sheet consisting of a transparent base 21 and the optically anisotropic layer 23 disposed thereon is a layer consisting of a compd. having a discotic structural unit and having negative double refraction and the disk surface of the discotic structural unit inclines with the plane of the transparent base 21. In addition, the angle formed by the disk surface of the discotic structural unit and the plane of the transparent base 21 is changed in the depth direction of the optically anisotropic layer 23. This liquid crystal display device and color liquid crystal display device have such sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical compensation sheet, a liquid crystal display device having the optical compensation sheet, and a color liquid crystal display device.

[0002]

2. Description of the Related Art CRTs (cathode ray tubes) have been mainly used as display devices for office automation equipment such as desktop personal computers and word processors. 2. Description of the Related Art Recently, liquid crystal display devices (hereinafter, referred to as LCDs) are widely used instead of CRTs because of their thinness, light weight, and low power consumption. The LCD generally includes a liquid crystal cell and a pair of polarizing plates provided on both sides of the liquid crystal cell. Most of such LCDs use twisted nematic liquid crystals.

The LCD display system can be roughly classified into a birefringence mode and an optical rotation mode. A super twisted nematic liquid crystal display device (hereinafter referred to as STN-LCD) utilizing a birefringence mode uses a super twisted nematic liquid crystal having a twist angle of more than 90 degrees and steep electro-optical characteristics. . Therefore, such an STN-LCD can display a large amount of data by time-division driving. However, STN-LC
D has a problem that the response speed is slow (several hundreds of milliseconds) and gradation display is difficult. Therefore, D has a display characteristic of a liquid crystal display device (eg, TFT-LCD and MIM-LCD) using active elements. It is inferior in comparison. TFT-LCD and MIM-
In LCDs, twisted nematic liquid crystals with a twist angle of 90 degrees and positive birefringence are used to display images. In the display mode of TN-LCD,
High-speed response (tens of milliseconds) and high contrast can be obtained. Therefore, the optical rotation mode is advantageous in many points as compared with the birefringence mode and other modes. However, TN
-In LCDs, the display color and display contrast change depending on the angle at which the liquid crystal display device is viewed (viewing angle characteristics).
Its display characteristics have not reached the level of CRT.

In order to improve the above-mentioned viewing angle characteristics (that is, to enlarge the viewing angle), a proposal that a retardation plate (optical compensation sheet) is provided between a pair of polarizing plates and a liquid crystal cell is proposed in Japanese Patent Laid-Open Publication No. Hei 4 (1998).
No. 229828 and Japanese Patent Laid-Open No. 4-258923. The retardation plate proposed in the above publication has almost no retardation in the vertical direction with respect to the liquid crystal cell, and therefore does not exert any optical action from the front, but when retarded, the retardation appears. To compensate for the phase difference generated in the liquid crystal cell. This phase difference brings about unfavorable viewing angle characteristics such as coloring and disappearance of the displayed image.
As such an optical compensation sheet, a sheet having a negative birefringence so as to compensate the positive birefringence of the nematic liquid crystal and having an inclined optical axis is effective.

[0005] JP-A-6-75115 and EP05
76304A1 discloses an optical compensatory sheet having negative birefringence and an inclined optical axis. That is, the sheet is made by stretching a polymer such as polycarbonate or polyester, and has a principal refractive index direction that is tilted from the normal to the sheet. Since the production of the above-mentioned sheet by the stretching requires an extremely complicated stretching, it is extremely difficult to produce a large-area optical compensatory sheet by the disclosed method.

On the other hand, it is also known to use a liquid crystalline polymer. For example, JP-A-3-9326 and JP-A-3-9326
JP-2911601 discloses an optical compensation sheet obtained by applying a polymer having liquid crystallinity to the surface of an alignment film on a support film. However,
Since the polymer having liquid crystallinity does not show sufficient alignment on the alignment film, the viewing angle can hardly be increased in all directions. Further, JP-A-5-215921 discloses an optical compensation sheet (birefringence plate) comprising a support and a polymerizable rod-shaped compound having liquid crystallinity and positive birefringence. This optical compensation sheet is obtained by applying a solution of the polymerizable rod-like compound to a support and curing by heating. However, since this polymer having liquid crystallinity has no birefringence, the omnidirectional viewing angle can hardly be expanded.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical compensatory sheet which can be easily manufactured and has a wide viewing angle. Another object of the present invention is to provide an optical compensatory sheet which can be easily produced, has a negative negative refraction, and has a minimum value of retardation in a direction inclined from the sheet normal line. . Furthermore, an object of the present invention is to provide a liquid crystal display device having an optical compensatory sheet in which the viewing angle is enlarged and the contrast is not substantially reduced, the gradation or black-and-white inversion, and the hue change is hardly caused by the change in the viewing angle. It is in. Further, an object of the present invention is to provide a color liquid crystal display device having an optical compensation sheet which has a wide viewing angle and hardly causes a decrease in contrast, gradation or black-white inversion, and a change in hue due to a change in viewing angle. Is to do.

[0008]

The present invention provides an optical compensatory sheet comprising a transparent support and an optically anisotropic layer provided thereon, wherein the optically anisotropic layer is a compound having a discotic structural unit. And the disc surface of the discotic structural unit (hereinafter, also simply referred to as “surface”) is inclined with respect to the transparent support surface, and the discotic structural unit has a negative birefringence. An optical compensatory sheet characterized in that the angle between the disk surface and the transparent support surface changes in the depth direction of the optically anisotropic layer.

Preferred embodiments of the optical compensatory sheet are as follows. 1) The optical compensation sheet, wherein the angle increases in the depth direction of the optically anisotropic layer as the distance from the bottom surface of the optically anisotropic layer increases. 2) The optical compensation sheet, wherein the angle changes within a range of 5 to 85 degrees. 3) The optical compensation sheet wherein the minimum value of the angle is in the range of 0 to 85 degrees (preferably 5 to 40 degrees) and the maximum value is in the range of 5 to 90 degrees (preferably 30 to 85 degrees). . 4) The above optical compensation sheet, wherein the difference between the minimum value and the maximum value of the angle is in the range of 5 to 70 degrees (preferably 10 to 60 degrees). 5) The optical compensatory sheet wherein the angle 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. 6) The above optical compensation sheet, wherein the optically anisotropic layer further contains a cellulose ester. 7) The above optical compensation sheet, wherein the optically anisotropic layer further contains cellulose acetate butyrate. 8) The above optical compensation sheet wherein the haze of the optically anisotropic layer is 5.0 or less. 9) The above optical compensation sheet, wherein the optically anisotropic layer forms a monodomain or a large number of domains having a size of 0.1 μm or less. 10) The transparent support has an optically negative uniaxial property and has an optical axis in a direction normal to the surface of the transparent support, and the following condition: 20 ≦ {(nx + ny) / 2-nz} × d ≦ 400 (where nx and ny represent the in-plane principal refractive index, nz represents the principal refractive index in the thickness direction, d represents the thickness of the support, and the unit of the above formula) Is nm). 11) The above optical compensation sheet, wherein an alignment film (preferably a cured polymer film) is formed between the optically anisotropic layer and the transparent support. 12) The optical compensation sheet according to 10) above, wherein an undercoat layer is formed between the optically anisotropic layer and the alignment film. 13) The optical compensation sheet described above, wherein a protective layer is formed on the optically anisotropic layer. 14) The optical compensatory sheet, wherein the optically anisotropic layer has a minimum absolute retardation value other than 0 in a direction inclined from the normal line direction of the optical compensatory sheet. 15) The above-mentioned optical compensation sheet, wherein the transparent support has a light transmittance of 80% or more and has its optical axis in the normal direction of the support. 16) The optical compensation sheet as described in 11) above, wherein the alignment film is a rubbed polymer layer. 17) The optical compensation sheet according to the above 11), wherein the alignment film is a deposition film obtained by obliquely depositing an inorganic compound.

Further, the present invention provides 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 alignment 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 an alignment plate, the optical compensation sheet comprises a transparent support and an optically anisotropic layer provided thereon, and The layer is a layer having a negative birefringence made of a compound having a discotic structural unit, and further has a disc surface of the discotic structural unit, and is inclined with respect to a transparent support surface, and the discotic structural unit is There is also a liquid crystal display device characterized in that the angle between the disk surface and the transparent support surface changes in the depth direction of the optically anisotropic layer.

The preferred embodiments of the above liquid crystal display device are as follows. 1) The liquid crystal display device, wherein the angle increases in the depth direction of the optically anisotropic layer as the distance from the bottom surface of the optically anisotropic layer increases. 2) The liquid crystal display device, wherein the angle changes within a range of 5 to 85 degrees. 3) The liquid crystal display device wherein the minimum value of the angle is in a range of 0 to 85 degrees (preferably 5 to 40 degrees) and the maximum value is in a range of 5 to 90 degrees (preferably 30 to 85 degrees). . 4) The above liquid crystal display device, wherein the optically anisotropic layer further contains a cellulose ester (preferably, cellulose acetate butyrate). 5) The above liquid crystal display device, wherein an alignment film is formed between the optically anisotropic layer and the transparent support. 6) The liquid crystal display device, 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 rubbed in one direction, and the optical compensation sheet has a direction in which the minimum value of its retardation is orthographically projected onto the liquid crystal cell, The liquid crystal display device according to 6) above, which is arranged on the liquid crystal cell such that the angle formed by the rubbing direction of the substrate surface of the liquid crystal cell near the compensation sheet is 90 to 270 degrees. 8) A liquid crystal display device in which one or two optical compensation sheets are provided on one side of a liquid crystal cell, or two sheets are provided on both sides of a liquid crystal cell.

Further, according to the present invention, a pair of substrates each having a transparent electrode, a pixel electrode, and a color filter, and a liquid crystal cell composed of a twist-aligned nematic liquid crystal enclosed between the substrates and provided on both sides of the liquid crystal cell. In a color liquid crystal display device comprising a pair of alignment plates and an optical compensation sheet provided between a liquid crystal cell and the alignment plate, the optical compensation sheet comprises a transparent support and an optical anisotropic layer provided thereon. And 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 inclined with respect to the transparent support surface, Further, the angle formed by the disc surface of the discotic structural unit and the transparent support surface changes in the depth direction of the optically anisotropic layer. There is also the device.

Preferred embodiments of the above color liquid crystal display device are as follows. 1) The color liquid crystal display device, wherein the angle increases in the depth direction of the optically anisotropic layer with an increase in the distance from the bottom surface of the optically anisotropic layer. 2) The color liquid crystal display device, wherein the angle changes in the range of 5 to 85 degrees. 3) The color liquid crystal display in which the minimum value of the angle is in the range of 0 to 85 degrees (preferably 5 to 40 degrees) and the maximum value thereof is in the range of 5 to 90 degrees (preferably 30 to 85 degrees). apparatus. 4) The 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, wherein an alignment film is formed between the optically anisotropic layer and the transparent support. 6) The color liquid crystal display device, wherein one of the pair of substrates has a (transparent) pixel electrode and the other substrate has a counter transparent electrode and a color filter. 7) The (transparent) pixel electrode is a TFT as a nonlinear active element.
(thin-film-transistor) or MIM (metal-insulator
-color) liquid crystal display device of 6) having metal). 8) The above-mentioned color liquid crystal display device used in a normally white mode, in which two absorption axes of a pair of polarizing plates are at a right angle to 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, wherein the optically anisotropic layer has a minimum absolute value of the 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 optical compensatory sheet orthogonally projects the direction of the minimum value of the retardation onto the liquid crystal cell, The liquid crystal display device according to the above item 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 compensation sheet is 90 to 270 degrees.

The optical compensatory sheet of the present invention is an optical compensatory sheet comprising a transparent support and an optical anisotropic layer provided thereon, the optical anisotropic layer comprising a compound having a discotic structural unit. It is a layer having birefringence.
Examples of the compound having a discotic structural unit include a polymer obtained by polymerizing a low molecular weight discotic liquid crystalline compound such as a monomer or a polymerizable discotic liquid crystalline compound. The discotic compound can be generally classified into a compound having a discotic liquid crystal phase (that is, a discotic nematic phase) and a compound having no discotic liquid crystal phase. Discotic compounds generally have negative birefringence. The present invention utilizes the negative birefringence of a discotic compound, and determines the discotic structural unit such that the angle between the surface (disc surface) of the discotic structural unit and the transparent support surface is the depth of the optical anisotropic layer. This has been achieved by arranging them so that they change in direction.

The optical compensatory sheet of the present invention comprises a transparent support and an optically anisotropic layer comprising a compound having a discotic structural unit, which is provided on the transparent support, and further comprises an alignment film comprising the transparent support and the optically anisotropic layer. It is preferable to provide. 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.

As the material for 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. Examples of such materials include ZEONEX (manufactured by Zeon Corporation) and ARTO.
Commercially available products such as N (manufactured by Japan Synthetic Rubber Co., Ltd.) and Fujitac (manufactured by Fuji Photo Film Co., Ltd.) can be used. Furthermore, even for materials with a large intrinsic birefringence such as polycarbonate, polyarylate, polysulfone, and polyethersulfone, conditions such as solution casting and melt extrusion, as well as stretching conditions in the vertical and horizontal directions are set as appropriate. Can be obtained.

Assuming that the in-plane main refractive index is nx, ny, the thickness direction main refractive index is nz, and the film thickness is d, the triaxial main refractive index relationship is nz < ny
= Nx (negative uniaxiality) is satisfied, the expression {(nx + ny) /
The retardation represented by 2-nz｝ × d is 20 nm
To 400 nm (preferably 30 to 150 nm). However, the values of nx and ny do not have to be exactly the same, and it is sufficient if they are almost equal. In particular,
If | nx-ny | / | nx-nz | ≦ 0.2, there is no practical problem. The front retardation represented by | nx-ny | × d is preferably 50 nm or less,
More preferably, it is 20 nm or less. N above
FIG. 1 shows the relationship among x, ny, nz, and d.

It is preferable to provide an undercoat layer on the transparent support in order to increase the adhesive strength between the transparent support and the alignment film. The undercoat layer is generally formed by coating on the surface of a surface-treated transparent support. As the surface treatment,
Chemical treatment, mechanical treatment, corona discharge treatment, flame treatment, UV
Treatment, high-frequency treatment, glow discharge treatment, active plasma treatment, and ozone oxidation treatment. Glow discharge treatment is preferred. Various arrangements have been made as to the structure of the undercoat layer. A layer that adheres well to a polymer film (hereinafter referred to as the first undercoat layer) is provided as the first layer, and an alignment film as the second layer is formed thereon. A so-called multi-layer method of applying a hydrophilic resin layer (hereinafter, abbreviated as the second undercoat layer) that adheres well to a single-layer method of applying only one resin layer containing both a hydrophobic group and a hydrophilic group There is.

In the first undercoat layer in the multi-layer method, for example, a copolymer containing a monomer selected from vinyl chloride, vinylidene chloride, butadiene, methacrylic acid, acrylic acid, itaconic acid and maleic anhydride as a starting material is used. Combined; polyethyleneimine; 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-probylene copolymer, butadiene-acrylonitrile copolymer, and blends of these copolymers and halogen-containing resins 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-chloromethyl acrylate, polyacrylic acid methoxyethyl ester, polyacrylic acid glycidyl ester, polyacrylic acid butyl ester, polyacrylic acid methyl ester 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; Polyethylene methylene bis-4-phenyleneca Bonate; and bisphenol A-polycarbonate Can. For these oligomers or polymers, see E. H. Imager "P
oligomer Handbook ", IV, 187-2
31, Interscience Pub. New Y
Ork, 1966. As a material for the second layer of the undercoat, gelatin can be mentioned.

In the single layer method, the undercoat layer is formed such that the polymer film is expanded and mixed with the hydrophilic undercoat polymer at the interface to obtain good adhesion.
As the hydrophilic undercoat polymer used in the present invention, a water-soluble polymer, a cellulose ester, a latex polymer,
A water-soluble polyester or the like can be used. Examples of the water-soluble polymer include gelatin, gelatin derivatives, casein, agar, sodium alginate, starch, and polyvinyl alcohol.
Examples thereof include alcohol, polyacrylic acid copolymer and maleic anhydride copolymer, and 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. Of these, gelatin is the most preferable. As the gelatin, those commonly used 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-processed gelatin and acid-processed gelatin are most preferably used. These gelatins have various impurities in the production process, for example, 0.11 to 20,000 p.
pm metals (Na, K, Li, Rb, Ca, Mg, B
a, Ce, Fe, Sn, Pb, Al, Si, Ti, A
u, Ag, Zn, Ni and other metals, and their ions), and ions (F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , sulfate ions, nitrate ions, acetate ions, ammonium ions, etc.) Good. Particularly in lime-processed gelatin, it is common to contain ions of Ca and Mg, the content of which is generally 10 to 3000 ppm, preferably 1000 ppm or less from the viewpoint of undercoating performance, more preferably It is 500 ppm or less.

Specific examples of the compounds used in the adhesion improving layer of the present invention are shown below.

[0022]

Embedded image x: y: z = 25: 60: 25

[0023]

Embedded image x: y = 70: 30 average molecular weight: 45000

[0024]

[Chemical 3] x: y = 50: 50 Average molecular weight: 12000

[0025]

[Chemical 4] x: y = 30: 70 State: latex

[0026]

Embedded image Average molecular weight: 10,000

In addition, the coating liquid for forming the undercoat layer may contain various additives if 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-based compound, an amidinium salt-based compound, a carbodiimide compound, and a pyridinium salt-based 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 (TiO ₂ )
₂ ), calcium carbonate and magnesium carbonate can be used. Organic particulate matting agents include polymethylmethacrylate, cellulose acetate propionate, polystyrene and US Pat. No. 4,142,894.
And the like. The average particle size of these fine particle matting agents is 0.01 to 1
It is preferably 0 μm. More preferably, 0.05 to
5 μm. Moreover, the content is 0.5-600 m.
g / m ² is preferable, and 1 to 400 mg / m ² is more preferable.

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. And this orientation gives the optical axis inclined 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 rubbing layer of an organic compound (preferably a polymer), an oblique deposition layer of an inorganic compound, and a layer having microgrooves, and further ω-tricosanoic acid, dioctadecylmethylammonium chloride and stearyl. Examples thereof include a cumulative film formed by the Langmuir-Blodgett method (LB film) such as methyl acid, or a layer in which a dielectric is oriented by applying an electric field or a 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). The liquid crystal discotic compound can be obliquely aligned in the alignment film obtained by subjecting the layers of these polymers to the alignment treatment.

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 the strong interaction between the alkyl chains on the alignment film surface and the alkyl side chains of the discotic liquid crystal. Further, the alkyl group preferably has 6 to 14 carbon atoms, and further has -S- and-.
It is preferably bonded to polyvinyl alcohol via (CH ₃ ) C (CN)-or-(C ₂ H ₅ ) N-CS-S-. The alkyl-modified polyvinyl alcohol has an alkyl group at the end, and preferably has a saponification degree of 80% or more and a polymerization degree of 200 or more. Further, the polyvinyl alcohol having an alkyl group in the side chain is MP103 manufactured by Kuraray Co., Ltd.
Commercially available products such as MP203 and R1130 can be used.

Further, a polyimide film (preferably, a fluorine atom-containing polyimide) widely used as an alignment film for LCD is also preferable as the organic alignment film. This is obtained by applying polyamic acid (for example, LQ / LX series manufactured by Hitachi Chemical Co., Ltd., SE series manufactured by Nissan Kagaku Co., Ltd.) to the support surface and baked at 100 to 300 ° C. for 0.5 to 1 hour. After that, 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 obtaining orientation by rubbing the surface of the orientation film in a certain direction with paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. Generally, rubbing is performed several times using a cloth or the like on 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 represented as a representative, 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 vapor deposition film can be formed using a vapor deposition device. An inorganic oblique vapor deposition film can be formed by fixing a film (support) and performing vapor deposition, or by moving a long film and performing vapor deposition continuously.

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 polymer layer 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); Report of Destrade et al., Mol. Cr
yst. 122, 141 pages (1985), Phys
ics lett, A, Vol. 78, page 82 (1990); Kohne et al., Angew. Chem. Volume 96, page 70 (1
984) and the cyclohexane derivative described in J.
M. Lehn et al., J. Chem. Commu
n. , Pp. 1794 (1985), J. 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-mentioned discotic (discotic) compound generally has a structure in which these are the cores of the molecule center and linear alkyl groups, alkoxy groups, substituted benzoyloxy groups, etc. are radially substituted as the linear chains. , Which shows liquid crystallinity and includes what is generally called discotic liquid crystal. However, the molecule is not limited to the above description as long as the molecule itself has negative uniaxiality and can give 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,
Those that are polymerized or cross-linked by a reaction by light or the like to have a high molecular weight and lose liquid crystallinity are also included.

Preferred examples of the above discotic compound are shown below.

[0038]

[Chemical 6]

[0039]

[Chemical 7]

[0040]

Embedded image

[0041]

[Chemical 9]

[0042]

[Chemical 10]

[0043]

[Chemical 11]

[0044]

[Chemical 12]

[0045]

[Chemical 13]

[0046]

Embedded image

[0047]

[Chemical 15]

[0048]

Embedded image

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 made 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 changes 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. The tilt angle preferably 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 tilt 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.

A typical example of a cross section of the optically anisotropic layer of the present invention is schematically shown in FIG. The optically anisotropic layer 23 is provided on the alignment film 22 formed on the transparent support 21.
In the liquid crystal discotic compounds 23a, 23b and 23c forming the optically anisotropic layer 23, the discotic structural units Pa, Pb and Pc are planes 2 parallel to the plane of the transparent support 21.
1a, 21b, 21c, and their inclination angles θa, θb, θc (angles formed by the surface of the discotic structural unit and the surface of the transparent support) from the bottom of the optically anisotropic layer ( It increases in order as the distance in the (thickness) direction increases. 24 represents the normal line of the transparent support. The liquid crystalline discotic compound is a planar molecule, and therefore there is only one plane in the molecule, that is, a disc surface (eg, 21a, 21a).
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. 2, the tilt angle (eg, θa) of the discotic structural unit on the support side corresponds to almost the minimum value, and the tilt angle of the discotic structural unit (eg, θc) corresponds to the maximum value. There is. Further, it is preferable that the difference between the minimum value and the maximum value of the inclination angle is in the range of 5 to 70 degrees (particularly 10 to 60 degrees).

The optically anisotropic layer is generally formed by applying a solution of a discotic compound and another compound in a solvent onto an alignment film, drying the solution, and then heating the solution to a temperature for forming a discotic nematic phase. (Discotic nematic phase) is obtained by cooling. Alternatively, the optically anisotropic layer may be prepared by applying a solution prepared by dissolving a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) in a solvent onto the alignment film, drying the disc, and then applying the discotic nematic. It is obtained by heating to a phase forming temperature, polymerizing (by irradiation with UV light, etc.), 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
300 degreeC is preferable and 70-170 degreeC is especially 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 treatment method. Further, the inclination angle of the discotic unit on the surface side (air side) is generally selected from a discotic compound or another compound (eg, a plasticizer, a surfactant, a polymerizable monomer and a polymer) used together with the discotic compound. It can be adjusted. Further, the degree of change in the tilt angle can be adjusted by the above selection.

The above-mentioned 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 crystal discotic compound or does not hinder the alignment. Of these, polymerizable monomers (eg, compounds having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) are preferable.
The above compounds are generally used in an amount of 1 to 50% by weight (preferably 5 to 30% by weight) based on the discotic compound.

As the polymer, any polymer can be used as long as it is compatible with the discotic compound and can change the tilt angle of the liquid crystalline discotic compound. Cellulose ester can be mentioned as an example of a polymer. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose and cellulose acetate butyrate. The above-mentioned polymer is generally 0.1 to 10% by weight (preferably 0.1 to 8% by weight, particularly 0.1 to 5% by weight) based on the discotic compound so as not to disturb the alignment of the liquid crystalline discotic compound. ) Amount used. The degree of butyrylation of cellulose acetate butyrate (cellulose acetate butyrate) is preferably 30% or more, particularly preferably 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 the optically anisotropic layer (optical compensatory sheet) having the changing inclination angle shown in FIG. 2 has a very wide viewing angle, and inverts the black and white image. Or the display image has almost no gradation or coloring.

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 the normally white mode in which the transmission axes of the polarizer and the analyzer are substantially orthogonal to each other (the mode that is widely adopted in TN-LCD), the portion in the black display state Is a state in which a voltage is applied to the liquid crystal, and the transmittance of light from the black display portion remarkably increases as the viewing angle increases, resulting in 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. Therefore, the phase difference caused by the tilt of the liquid crystal molecules inside the TN liquid crystal cell when a voltage is applied is compensated by the change of the tilt angle of the discotic structure unit surface of the optically anisotropic layer and the negative birefringence of the present invention. 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. Therefore, 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
Measured according to 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 lowered. This tendency is remarkable when the incident light is inclined in the normal direction and 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. Generally, haze has a rough surface (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 may 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 adhesive layer is not particularly limited, and a transparent adhesive such as an acrylic, SBR, or silicone rubber adhesive or an adhesive can be used. From the viewpoint of preventing the deterioration of the optical properties of the constituent members, those that do not require a high temperature process at the time of curing or drying are preferable, and those that 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 types and amounts of other compounds used in combination). The conditions include a heating temperature or heating time for forming a discotic nematic layer, a cooling rate after heating, a layer thickness, a coating method, and the like. In addition, 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 may be made into a monodomain, or even if a plurality of domains are formed, each of the domains may be reduced to 0.1 μm or less, preferably 0.08 μm.
By setting m or less, it is possible to prevent the visible light from being affected.

The optically anisotropic layer of the present invention has a minimum retardation absolute value other than 0 (has no optical axis) in a direction inclined from the normal direction of the optical compensation sheet. FIG. 4 shows a typical configuration example of the optical compensation sheet including the optically anisotropic layer of the present invention. In FIG. 4, the transparent support 41 and the alignment film 4
2 and layer of discotic compound (optically anisotropic layer) 4
3 are sequentially laminated to form an optical compensation sheet.
R indicates the rubbing direction of the alignment film. n ₁ n ₂ and n ₃
Represents the triaxial refractive index of the optical compensation sheet, and satisfies the relationship of n ₁ ≦ n ₃ ≦ n ₂ when viewed from the front. β
Is the inclination from the normal line 44 of the optically anisotropic layer in the direction showing the minimum value of Re (retardation). In order to improve the viewing angle characteristics of TN-LCD and TFT-LCD, Re
The direction showing the minimum value of the absolute value of
From 5 to 50 degrees (the average value of the inclination), and more preferably from 10 to 40 degrees (the above β). Furthermore,
The sheet has the following conditions: 50 ≦ [(n ₃ + n ₂ ) / 2−n ₁ ] × D ≦ 400 (n
m) (where D is the thickness of the sheet), and further, the following condition: 100 ≦ [(n ₃ + n ₂ ) / 2−n ₁ ] × D ≦ 400
(Nm)

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; non-polar solvents such as benzene and hexane; alkyl halides such as chloroform and dichloromethane; acetic acid. Mention may be made of 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,
Mention may be made of dip coating, spin coating, printing coating, spray coating and slide coating. In the present invention, a vapor deposition method can also be used in the case of a mixture of only discotic compounds. In the present invention, continuous coating is preferred. Therefore, curtain coating, extrusion coating, roll coating and slide coating are preferred. As described above, the above-mentioned optically anisotropic layer is obtained by applying the above-mentioned coating solution on the alignment film, drying it, then heating it to a glass transition temperature or higher (then curing it if desired) and cooling it.

Since the optical compensatory sheet of the invention compensates the birefringence of the liquid crystal cell in the liquid crystal display device, it is preferable that the wavelength dispersion of the optically anisotropic element is 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.

FIG. 5 shows a typical configuration example of the liquid crystal display device of the present invention. In FIG. 5, a liquid crystal cell TNC composed of a pair of substrates having a transparent electrode and a twisted 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 The optical compensation sheets RF ₁ , RF ₂ and the backlight BL arranged between the liquid crystal display device and the polarizing plate constitute a liquid crystal display device. The optical compensatory sheet may be disposed on only one side (that is,
RF ₁ or RF ₂ ). R ₁ is the optical compensation sheet RF ₁
Of indicates the rubbing direction when viewed from the front, R ₂ represents a rubbing direction of the optical compensatory sheet RF _2. Liquid crystal cell T
The solid arrow of NC 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 is shown.
PA and PB represent the polarization axes of the polarizing plates A and B, respectively.

In the liquid crystal display of the present invention, the optical compensation sheet and the liquid crystal cell are preferably arranged as follows. FIG. 6 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 minimum 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
Shows 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 absolute 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. 7 is a diagram obtained when FIG. 6 is viewed from the z-axis direction.
In FIG. 7, 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 also be applied when using two optical compensation sheets. 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 FIGS. 8 and 9, it is preferable that a pair of optical compensation sheets are provided on both sides of the liquid crystal cell. In FIG. 8, a pair of polarizing plates 83a and 83b are arranged on both sides of the liquid crystal cell 81, an optical compensation sheet 82a is arranged between the polarizing plate 83a and the liquid crystal cell 81, and an optical compensation sheet 82b.
Are arranged between the polarizing plate 83b and the liquid crystal cell 81. 82 Ma is the direction when the direction of the minimum absolute value of the retardation of the optical compensation sheet 82a is orthographically projected onto the liquid crystal cell, and 82Mb is the direction of the minimum absolute value of the retardation of the optical compensation sheet 82b. Is the direction when orthographically projected onto the liquid crystal cell. 81Ra is the liquid crystal cell 8
1 represents the rubbing direction of the upper substrate, and 81Rb represents the rubbing direction of the lower substrate of the liquid crystal cell 81. 84 represents a light source.

An angle (α1) formed between the direction 82Ma when the direction of the minimum absolute value of retardation is orthographically 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-
It is preferably in the range of 225 degrees. That is, the angles (α1 and α2) can be defined as shown in FIG. FIG. 9 is a diagram obtained when FIG. 8 is viewed from the z-axis direction. In FIG. 9, 81Ra, 81Rb, 82Ma and 82Mb have the same meaning as in FIG. Corner (α1)
Is the orthogonal projection direction 82M indicating the minimum value of the retardation.
a and the rubbing direction 81Ra of the upper substrate.
The angle (α2) is the angle between the orthographic projection direction 82Mb indicating the minimum value of retardation and the rubbing direction 81Rb of the lower substrate. The angle (β1) formed between the orthographic projection directions 82Ma and 82Mb, which shows the minimum value of retardation, is 90 to 18
A range of 0 degrees is preferred.

In the liquid crystal display device of the present invention, FIG.
As shown in FIGS. 11 and 12, two optical compensation sheets may be provided on one side of the liquid crystal cell. In FIG. 10, a pair of polarizing plates 103 a and 103 b are arranged on both sides of the liquid crystal cell 101, and optical compensation sheets 102 a and 102 b are arranged between the polarizing plate 103 a and the liquid crystal cell 101. 102 Ma is the direction when the direction of the minimum absolute value of the retardation of the optical compensation sheet 102 a is orthographically projected on the liquid crystal cell, and 102 Mb is the optical compensation sheet 1.
The direction of the minimum absolute value of retardation 02b is the direction when orthographically projected on the liquid crystal cell. 101Ra is
Represents the rubbing direction of the upper substrate of the liquid crystal cell 101,
01Rb represents the rubbing direction of the lower substrate of the liquid crystal cell 101. Reference numeral 104 represents a light source.

The angle between the direction 102Ma when the direction of the minimum absolute value of retardation is orthographically projected onto the liquid crystal cell and the rubbing direction 101Ra of the upper substrate of the liquid crystal cell (α
3) It is preferably in the range of 135 to 225 degrees, and 1
The angle (α4) formed 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. 11 is a diagram obtained when FIG. 10 is viewed from the z-axis direction. In FIG. 11, 101Ra, 101Rb, 102
Ma and 102Mb have the same meaning as in FIG.
The angle (α3) is the angle between the orthographic projection direction 102Ma showing the minimum retardation value and the rubbing direction 101Ra of the upper substrate, and the angle (α4) is the orthographic projection direction 102Mb showing the minimum retardation value and the lower side. This is the angle with the rubbing direction 101Rb of the substrate. The angle (β1) formed by 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 direction of the minimum value of the retardation and the rubbing direction of the substrate of the liquid crystal cell can be applied to a color liquid crystal display device. FIG. 12 shows a typical configuration example of the color liquid crystal display device of the present invention. 12, 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 and 128b and a pair of optical compensation sheets 127a and 127b arranged between the liquid crystal cell and the polarizing plate are combined to form a color liquid crystal display device. The optical compensatory sheet may be disposed on only one side (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 237-251) 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.

As the liquid crystal used in the (color) liquid crystal display device of the present invention, 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. Since the major axis of the liquid crystal molecules is twisted at about 90 ° C. between the upper and lower substrates of the liquid crystal cell, the incident linearly polarized light is polarized at 90 ° C. due to the optical rotatory power of the liquid crystal cell when there is no applied electric field. Instead, the light is emitted from the liquid crystal cell. When a sufficiently high electric field equal to or higher than the threshold value is applied, the long axes of the liquid crystal molecules turn in the direction of the electric field and are aligned perpendicularly to the electrode surface, so that the optical rotatory power is almost lost. Therefore,
In order to sufficiently exhibit the effect of the optical rotation, the twist angle is preferably from 70 to 100C, more preferably from 80C to 90C.

In order to reduce defects (disclination) in 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. Regarding the above twist angle and pretilt angle, "LCD application" edited by Mitsuharu Okano and Shunsuke Kobayashi (Baifukan,
16 to 28).

Further, 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, for example, “Liquid Crystal Device” edited by Japan Society for the Promotion of Science, 142 Committee. Handbook "(Nikkan Kogyo Shimbun, pages 329-33)
As described on page 7), if d is increased, the contrast is improved, but the response speed is slow and the viewing angle is reduced. Therefore, the range of 0.3 to 1.0 μm is preferable, and The range of 3 to 0.6 μm is more preferable.

The 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 normally white mode, the applied voltage is 0 to 1.5V.
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. The protective film can be generally obtained by stretching triacetyl cellulose.
The protective film generally has a retardation (Re) of 0 to 200 nm, preferably Re of 0 to 100 nm. Re should be defined as {(nx + n
y) / 2−nz｝ × d.

[0080]

【Example】

[Example 1] Gelatin thin film (0.1 µm)
A linear alkyl-modified polyvinyl alcohol (MP203; manufactured by Kuraray Co., Ltd.) is coated on a 120 μm-thick triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.) coated with After drying,
A rubbing process was performed to form an alignment film. When the in-plane main refractive index is nx, ny, the refractive index nz in the thickness direction, and the thickness are d, | nx-ny of the triacetyl cellulose film
| × d, {(nx + ny) / 2−nz} × d were determined (see FIG. 1). The thickness was measured using a micrometer, and Re from various directions was measured using an ellipsometer (AEP-100, manufactured by Shimadzu Corporation), and the above-mentioned | nx-ny | × d, ｛(nx + ny) ) / 2
nz｝ × d was determined. | Nx−ny | × d of the triacetyl cellulose film is 3 nm, and ｛(nx + n
y) / 2-nz｝ × d was 60 nm. Therefore, the triacetyl cellulose film was almost uniaxial in the negative direction, and its optical axis was almost in the direction of the film line.

1.6 g of the above-mentioned liquid crystalline discotic compound TE-8 (8, m = 4) (the above compound example number) and phenoxydiethylene glycol acrylate (M101; manufactured by Toagosei Co., Ltd.) 0.4 g, cellulose acetate butyrate (CAB531-1; manufactured by Eastman Chemical Company) 0.05 g, and a photopolymerization initiator (Irgacure-907; manufactured by Ciba-Geigy Company)
The coating liquid obtained by dissolving 01 g in 3.65 g of methyl ethyl ketone was applied with a wire bar (# 4 bar).
Then, it is fixed by adhering it to a metal frame and heated in a high temperature bath at 120 ° C. for 3 minutes to orient the discotic compound and then allowed to cool to room temperature to obtain a discotic compound having a thickness of 1.8 μm. A layer containing (optically anisotropic layer) was formed. Thus, the optical compensatory sheet (OC) of the present invention having the optically anisotropic layer is formed.
S-A) was produced.

The obtained optical compensation sheet of the present invention (OCS)
-A) 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 for dyeing. The obtained dyed film was observed with a transmission electron microscope (TEM) to obtain a micrograph thereof. In the dyed film, the discotic compound TE-
8 (8, m = 4) acryloyl groups were stained and recognized as a photographic image. From this photograph, the discotic compound in the optically anisotropic layer is tilted from the surface of the transparent support, and the tilt angle is from 5 to 65 degrees as the distance from the bottom of the optically anisotropic layer increases in the depth direction. A continuous increase was observed.

Example 2 Gelatin thin film (0.1 μm)
A linear alkyl-modified polyvinyl alcohol (MP203; manufactured by Kuraray Co., Ltd.) is coated on a 120 μm-thick triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.) coated with After drying,
A rubbing process was performed to form an alignment film. | Nx-ny | xd of the above triacetyl cellulose film is 3 nm
And {(nx + ny) / 2-nz} × d was 70 nm. These values were determined in the same manner as in Example 1. Therefore, the triacetyl cellulose film,
It was almost negatively uniaxial, and its optical axis was almost in the direction of the film line.

On the alignment film, 1.6 g of the above-mentioned liquid crystalline discotic compound TE-8 (8, m = 4) (the above compound example number) and phenoxydiethylene glycol acrylate (M101; manufactured by Toagosei Co., Ltd.) 0.4 g, cellulose acetate butyrate (CAB531-1; manufactured by Eastman Chemical Company) 0.05 g, and a photopolymerization initiator (Irgacure-907; manufactured by Ciba-Geigy).
The coating liquid obtained by dissolving 01 g in 3.65 g of methyl ethyl ketone was applied with a wire bar (# 4 bar).
Then, it is fixed on a metal frame and heated in a high-temperature bath at 120 ° C. for 3 minutes to orient the discotic compound, and then irradiated with UV light at 120 ° C. for 1 minute using a high-pressure mercury lamp to room temperature. After cooling, an optical compensation sheet (OCS-B) of the present invention having a layer (optically anisotropic layer) containing a discotic compound having a thickness of 1.8 μm was produced.

With respect to the optical compensation sheet (OCS-B) of the present invention thus obtained, the retardation values from all directions were measured on the surface including the rubbing axis and perpendicular to the retardation plate surface by an ellipsometer (AEP- 100; manufactured by Shimadzu Corporation), and further, the optical characteristics of the support after removing the discotic compound in the measurement portion were similarly measured. From these measurements, the optical properties (R
The relationship between e and the measurement angle) is as shown in FIG. When the result of FIG. 13 was simulated, the obtained optically anisotropic layer had negative birefringence, and the surface of the discotic compound was tilted from the support surface, and the tilt (tilt angle) was 20 degrees. From 50 to 50 degrees.

Example 3 Gelatin thin film (0.1 μm)
A linear alkyl-modified polyvinyl alcohol (MP203; manufactured by Kuraray Co., Ltd.) is coated on a 100 μm-thick triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.) coated with After drying,
A rubbing process was performed to form an alignment film. | Nx-ny | xd of the above triacetyl cellulose film is 6 nm
Then, {(nx + ny) / 2-nz} × d was 40 nm. These values were determined in the same manner as in Example 1. Therefore, the triacetyl cellulose film,
It was almost negatively uniaxial, and its optical axis was almost in the direction of the film line.

1.8 g of the above-mentioned liquid crystalline discotic compound TE-8 (8, m = 4) (the above compound example number) and ethylene glycol-modified trimethylolpropane triacrylate (V # 360; Osaka) 0.2 g of cellulose acetate butyrate (CAB551-0.2; manufactured by Eastman Chemical Company) 0.04 g, photopolymerization initiator (Irgacure-90)
7; Ciba Geigy) and 0.02 g of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.)
The coating solution obtained by dissolving in 3.43 g of methyl ethyl ketone was applied with a wire bar (# 3 bar), fixed on a metal frame and fixed, and heated in a high temperature bath at 120 ° C for 3 minutes. After orienting the tick compound, 120 ° C
For 1 second using a high pressure mercury lamp (120 W / cm)
Irradiated with V and allowed to cool to room temperature to prepare an optical compensation sheet (OCS-C) of the present invention having a layer (optically anisotropic layer) containing a discotic compound having a thickness of 1.8 μm.

With respect to the optical compensation sheet (OCS-C) of the present invention obtained as described above, the retardation value from any direction on the plane including the rubbing axis and perpendicular to the plane of the retardation plate was measured using an ellipsometer (AEP-A). 100; manufactured by Shimadzu Corporation), and the optical properties of the support after removing the discotic compound in the measurement portion were measured in the same manner. According to these measurements, 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 20 degrees.
It was found that the temperature changed continuously from 70 degrees to 70 degrees.

Example 4 Gelatin thin film (0.1 μm)
A linear alkyl-modified polyvinyl alcohol (MP203; manufactured by Kuraray Co., Ltd.) was applied onto a film of triacetyl cellulose having a thickness of 110 μm (manufactured by Fuji Photo Film Co., Ltd.) coated with 40 ° C. hot air. After drying
A rubbing process was performed to form an alignment film. | Nx-ny | × d of the triacetyl cellulose film is 3 nm,
{(Nx + ny) / 2-nz} × d was 50 nm. These values were determined in the same manner as in Example 1.
Therefore, the triacetyl cellulose film was almost negatively uniaxial, and the optical axis was almost in the direction of the film normal.

On this alignment film, 1.75 g of the above-mentioned liquid crystalline discotic compound TE-8 (8, m = 4) (the above compound example number) and α-acrolein-ω-phenoxy-polyoxyethylene (AMP60G; 0.25 g of Shin-Nakamura Chemical Co., Ltd., cellulose acetate butyrate (CAB500-5; manufactured by Eastman Chemical Company)
0.05 g, and a photopolymerization initiator (Irgacure-90)
7; Ciba Geigy Co., Ltd.) 0.01 g was dissolved in 3.43 g of methyl ethyl ketone to apply a coating solution with a wire bar (# 3 bar), which was fixed by sticking it on a metal frame and fixing it. After heating for 3 minutes in a high-temperature bath at ℃ to orient the discotic compound, UV irradiation was continued for 1 second using a high pressure mercury lamp (120 W / cm) at 120 ℃, and the temperature was allowed to cool to room temperature, and the thickness was 1 An optical compensation sheet (OCS-D) of the present invention having a layer (optically anisotropic layer) containing a discotic compound of 0.8 μm was produced.

With respect to the optical compensation sheet (OCS-D) of the present invention thus obtained, the retardation values from all directions on the plane including the rubbing axis and perpendicular to the retardation plate surface were measured by an ellipsometer (AEP- 100; manufactured by Shimadzu Corporation), and further, the optical characteristics of the support after removing the discotic compound in the measurement portion were similarly measured. According to these measurements, 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 20 degrees.
It was found that the temperature continuously changed from 40 degrees to 40 degrees.

Example 5 Gelatin Thin Film (0.1 μm)
A linear alkyl-modified polyvinyl alcohol (MP203; manufactured by Kuraray Co., Ltd.) is coated on a 100 μm-thick triacetyl cellulose film (Fuji Photo Film Co., Ltd.) coated with After drying,
A rubbing process was performed to form an alignment film. | Nx-ny | xd of the above triacetyl cellulose film is 3 nm
Then, {(nx + ny) / 2-nz} × d was 40 nm. These values were determined in the same manner as in Example 1. Therefore, the triacetyl cellulose film,
It was almost negatively uniaxial, and its optical axis was almost in the direction of the film line.

On this alignment film, 1.6 g of the above-mentioned liquid crystalline discotic compound TE-8 (8, m = 4) (the above compound example number), phenoxydiethylene glycol acrylate (M101; manufactured by Toagosei Co., Ltd.) 0 0.4 g, cellulose acetate butyrate (CAB531-1; Eastman Chemical Co., Ltd.) 0.05 g, and a photopolymerization initiator (Irgacure-907; Ciba Geigy Co., Ltd.)
A coating solution obtained by dissolving 01 g in 3.65 g of methyl ethyl ketone is applied with a wire bar (# 4 bar).
Then, it is fixed by sticking it on a metal frame and heating it in a high temperature bath at 120 ° C for 3 minutes to orient the discotic compound and then UV irradiation for 1 minute at 120 ° C using a high pressure mercury lamp until room temperature. After allowing to cool, an optical compensation sheet (OCS-F) of the present invention having a layer (optically anisotropic layer) containing a discotic compound having a thickness of 1.0 μm was produced.

With respect to the optical compensatory sheet (OCS-F) of the present invention thus obtained, the retardation values from all directions are measured on the plane including the rubbing axis and perpendicular to the retardation plate surface by an ellipsometer (AEP- 100; manufactured by Shimadzu Corporation), and further, the optical characteristics of the support after removing the discotic compound in the measurement portion were similarly measured. Based on these measurements, the Re of the obtained optically anisotropic layer was
The direction of the minimum value of is inclined 33 degrees from the normal of the sheet,
The minimum value was found to be 10 nm and Re in the thickness (depth) direction was found to be 110 nm. Further, the optically anisotropic layer obtained by the above measurement has a negative birefringence, the surface of the discotic compound is inclined from the surface of the support, and the inclination (tilt angle) is from 20 degrees to 50 degrees. It turns out that it is changing continuously.

Comparative Example 1 The above-mentioned liquid crystalline discotic compound TE-was formed on the alignment film provided on the triacetylcellulose film prepared in the same manner as in Example 1.
Methyl ethyl ketone was added to 8- (3) (the above compound example number), and a solution having a total of 10 wt% was applied by spin coating at 2,000 rpm. Then
The coating layer is heated to 180 ° C., heat-treated, and then cooled to room temperature, and the optical compensation sheet (OCS-
G) was prepared.

With respect to the optical compensation sheet (OCS-G) thus obtained, the retardation values from all directions are measured on the plane including the rubbing axis and perpendicular to the retardation plate surface by an ellipsometer (AEP-100; Shimadzu). (Manufactured by Seisakusho Co., Ltd.), and the optical characteristics of the support after removing the discotic compound in the measurement portion were also measured in the same manner.
From these measurements, it was found that the obtained optically anisotropic layer had negative birefringence, and the surface of the discotic compound was inclined from the surface of the support.

[Comparative Example 2] The above-mentioned liquid crystalline discotic compound TE-was formed on the alignment film provided on the triacetyl cellulose film prepared in the same manner as in Example 3.
6 (the above compound example number) was added with methyl ethyl ketone,
A solution of 10 wt% as a whole was applied by spin coating at 2000 rpm. Next, the coating layer is heated to 170 ° C., heat-treated, and then cooled to room temperature,
An optical compensation sheet (OCS-H) having a layer (optically anisotropic layer) containing a discotic compound having a thickness of 1.0 μm was produced.

With respect to the optical compensation sheet (OCS-H) obtained as described above, the retardation values from all directions on the plane including the rubbing axis and perpendicular to the retardation plate surface were measured using an ellipsometer (AEP-100; Shimadzu). (Manufactured by Seisakusho Co., Ltd.), and the optical characteristics of the support after removing the discotic compound in the measurement portion were measured in the same manner.
From these measurements, it was found that the obtained optically anisotropic layer had negative birefringence, and the surface of the discotic compound was inclined from the surface of the support.

[Evaluation of Optical Compensation Sheet]
5 and the optical characteristics of the optical compensation sheets obtained in Comparative Examples 1 and 2 were evaluated as follows. (1) The angle change of the discotic compound surface of the optically anisotropic layer and the inclination angle in the direction of the minimum value of Re were determined as described above. (2) Haze Haze was determined based on ASTN-D 1003-52. That is, it was measured using a turbidimeter (NDH-1001DO; manufactured by Nippon Denshoku Industries Co., Ltd.). (3) Size of domain The size of the domain formed in the optically anisotropic layer was measured using a polarizing microscope. The results are shown in Table 1.

[0101]

[Table 1] Table 1 ──────────────────────────────────── Seat haze ^* Optical axis inclination angle Re Minimum direction domain server No. (%) Change (degree) Angle (degree) is (μm) ──────────────────────────────────── -Example 1 OCS-A 1.0 None 5-65 30 ^** --- Example 2 OCS-B 1.0 None 20-50 35 ^** --- Example 3 OCS-C 0.3 None 20-70 40 ^** --- Example 4 OCS-D 0.3 None 20-40 25 ^** --- Example 5 OCS-F --- None 20-50 33 ^** --- ─────────── ────────────────────────── Comparative Example 1 OCS-G 8.1 Yes --37 10 10 Example 2 OCS-H 7.9 Yes −− 38 ^** −− ──────────────────────────────────── Remark) ^* : Re is 0 Direction ^** : " ^--- " indicates mono domain

[Examples 6 to 8 and Comparative Examples 3 to 5] (Preparation of Liquid Crystal Display) A liquid crystal cell in which a nematic liquid crystal was sandwiched so as to have a twist angle of 90 ° C. and a gap size of 4.5 μm. On one surface, two optically compensatory sheets prepared in Examples 2 to 4 (Examples 6 to 8) and Comparative Examples 1 to 2 (Comparative Examples 3 to 4) are laminated and attached, and a liquid crystal display device is provided. (See FIG. 10). However,
The angle (α3) formed by the projection direction (rubbing direction, 102Ma in FIG. 11) showing the minimum retardation of the lower optical compensation sheet and the rubbing direction (101Ra in FIG. 11) of the upper substrate is 180 degrees, and The angle (α4) formed by the projection direction (rubbing direction, 102 Mb in FIG. 11) showing the minimum retardation of the upper optical compensation sheet and the rubbing direction (101 Rb in FIG. 11) of the upper substrate is 0 degree. The above laminate was placed on the liquid crystal cell. Further, a pair of polarizing plates were attached to both sides of the liquid crystal cell having the optical compensation sheet so that the two polarization axes were orthogonal to each other. The protective film of the polarizing plate has a retardation of 40 nm (as in the above, {(nx + ny) / 2-nz} × d
A film of triacetyl cellulose having a value defined by 1) was used. The obtained TN-LCD was set for a normally white mode. As Comparative Example 5, a TN-LCD without the above optical compensation sheet was also manufactured.

A rectangular wave voltage of 55 Hz is applied from 0 to 5 V to the obtained TN-LCD, and the contrast from the front direction and from the direction inclined upward / downward and left / right is calculated as follows.
The measurement was performed using a spectrometer (LCD-5000, manufactured by Otsuka Electronics Co., Ltd.), and the front contrast (T _0V / T _5V ) and the upper / lower and left / right viewing angles at which the contrast was 10 or more were obtained. The results obtained are shown in Table 2.

[0104]

[Table 2] Table 2 シ ー ト Sheet Front contrast viewing angle (degree ) No. Up, down, left, right ──────────────────────────────────── Example 6 OCS-B 100 or more 130 125 Example 7 OCS-C 100 or more 130 130 Example 8 OCS-D 100 or more 120 120 ──────────────────────────────── Comparative Example 3 OCS-G 50 64 70 Comparative Example 4 OCS-H 59 61 66 Comparative Example 5 None 100 or more 61 95 ──────────────────── ────────────────

As is clear from Tables 1 and 2, the optical compensatory sheet of the present invention has the effect of widening the viewing angle, and can widen the viewing angle without lowering the front contrast.

Example 9 (Production of Liquid Crystal Display) Nematic liquid crystal (Δn: 0.
8), two optical compensation sheets prepared in Example 5 were adhered to both sides of a liquid crystal cell sandwiched so as to have a twist angle of 90 ° C. and a gap size of 4.5 μm, thereby producing a liquid crystal display device. (See FIG. 8). However, the angle (α1) formed by the projection direction (rubbing direction, 82Ma in FIG. 9) showing the minimum retardation of the upper optical compensation sheet and the rubbing direction (81Ra in FIG. 9) of the upper substrate is 180 degrees, Then, the projection direction showing the minimum value of the retardation of the lower optical compensation sheet (rubbing direction, 82M in FIG. 9).
The optical compensation sheet was placed on the liquid crystal cell so that the angle (α2) formed by b) and the rubbing direction of the lower substrate (81Rb in FIG. 9) was 180 degrees. Further, a pair of polarizing plates were attached to both sides of the liquid crystal cell having the optical compensation sheet so that the two polarization axes were orthogonal to each other.

A 1 kHz rectangular wave voltage of 1 to 5 V was applied to the obtained TN-LCD, and the contrast from the front direction and from the direction inclined upward / downward and left / right direction was calculated as follows.
The measurement was performed using a spectrometer (LCD-5000, manufactured by Otsuka Electronics Co., Ltd.), and the front contrast (T _0V / T _5V ) and the upper / lower and left / right viewing angles at which the contrast was 10 or more were obtained. FIG. 14 shows the obtained viewing angle characteristics. 14
Solid lines and dotted lines represent iso-contrast lines. Contrast ( _T1V / _T5V ) in black and white display is 10 or 10
The angle with respect to the normal line when 0 was indicated was the viewing angle.

[Examples 10 and 11] (Production of color liquid crystal display device) TF manufactured by Sharp Corporation
Peel off the polarizing plate of the T-type liquid crystal color television 6E-C3,
Two optical compensatory sheets used in Examples 2 and 3 (Examples 10 and 11, respectively) were mounted so as to sandwich the liquid crystal cell. Thereafter, two polarizing plates were adhered so that the polarizing axes were orthogonal to each other, with the whole being sandwiched on the outermost side, thereby producing a color liquid crystal display device of the present invention.

Comparative Example 6 The polarizing plate of a TFT type liquid crystal color television 6E-C3 manufactured by Sharp Corporation was peeled off, and Example 1 was performed.
The same two polarizing plates as those used in No. 0 were stuck so as to sandwich the liquid crystal cell so that the polarization axes were orthogonal to each other, thereby producing a color liquid crystal display device.

With the obtained color liquid crystal display device, white display and black display were carried out, and the contrast ratio in up, down, left and right was 1
A visual angle of 0: 1 was measured. That is, a rectangular wave voltage is applied to the obtained color liquid crystal display device, and the contrast from the front direction and the direction inclined upward / downward and left / right is measured by a spectrometer (LCD-5000, Otsuka Electronics Co., Ltd.). And the left / right viewing angles at which the contrast is 10 were determined. The results obtained are shown in Table 3.

[0111]

[Table 3] Table 3 ──────────────────────────────────── Seat viewing angle (degree) No ． Up / Down / Left / Right ──────────────────────────────────── Example 10 OCS-B 123 115 Example 11 OCS -C 130 120 ──────────────────────────────────── Comparative Example 6 None 50 70 ────────────────────────────────

As is clear from Table 3, the color liquid crystal display devices of Examples 10 and 11 have a greatly widened viewing angle as viewed from the contrast in black-and-white display as compared with that of Comparative Example 6. Recognize. When a video signal is input to the color liquid crystal display device of Comparative Example 6 to display a full-color image, the image is whitish when viewed from above and yellowish as a whole, and when viewed from below, the black display portion is immediately visible. Flipped. When viewed from the left and right, there is no inversion in the black display portion, but the contrast is reduced as a whole and it is yellowish, and the image quality is significantly degraded when the viewing angle is increased. On the other hand, in the color liquid crystal display devices obtained in Examples 10 and 11, when viewed from below, inversion was observed in the black display portion when the viewing angle was increased, but when viewed from above and from the left and right, No reversal was observed in the black display portion, yellowing of the image was slight, and deterioration of the image quality due to an increase in the viewing angle was small.

[0113]

INDUSTRIAL APPLICABILITY The liquid crystal display device and the color liquid crystal display device having the TN type liquid crystal cell using the optical compensation sheet of the present invention have a wide viewing angle, and the black display portion is inverted as the viewing angle increases. In addition, the occurrence of gradation reversal, image coloring, etc. is greatly reduced, and excellent viewing angle characteristics are exhibited. Especially T
A viewing angle characteristic of a liquid crystal display device having a non-linear active element such as FT can be remarkably improved, and a high-quality liquid crystal display device with excellent visibility can be provided. It goes without saying that excellent effects can be obtained even when the optical compensation sheet of the present invention is applied to an active matrix liquid crystal display device using a three-terminal device such as a MIM or a two-terminal device such as a TFD.

[Brief description of drawings]

FIG. 1 is a view schematically showing a relationship between a main refractive index nx, ny in a plane of a transparent support (film) and a main refractive index nz in a thickness direction.

FIG. 2 is a diagram showing a typical structure of an optically anisotropic layer of the present invention.

FIG. 3 is a diagram showing a typical structure of a liquid crystal layer of a liquid crystal display device.

FIG. 4 is a diagram schematically showing a typical configuration of an optical compensation sheet of the present invention and a relationship between triaxial main refractive indices.

FIG. 5 is a diagram showing a typical structure of a liquid crystal display device of the present invention.

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 an optical compensation sheet.

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

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

FIG. 10 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 an optical compensation sheet in which two sheets are laminated.

FIG. 11 is a diagram obtained when FIG. 10 is viewed from the z-axis direction.

FIG. 12 is a diagram showing a typical structure of a color liquid crystal display device of the present invention.

FIG. 13 is an optical compensation sheet (OCS) of the present invention.
6 is a graph showing the relationship between Re and the viewing angle of the optically anisotropic layer of −B).

FIG. 14 is a graph showing viewing angle characteristics with respect to contrast of the liquid crystal display device obtained in Example 9 of the present invention.

[Explanation of symbols]

21, 41 Transparent support 22, 42 Alignment film 23, 43 Optical 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 molecule

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Kamada 210, Nakanuma, Minamiashigara, Kanagawa Prefecture, Fuji Photo Film Co., Ltd. (72) Yosuke Nishiura, 210, Nakanuma, Minamiashigara, Kanagawa Prefecture, Fuji Photo Film Co., Ltd.

Claims (8)

[Claims] 1. An optical compensation sheet comprising a transparent support and an optically anisotropic layer provided thereon, wherein the optically anisotropic layer has a negative birefringence comprising a compound having a discotic structural unit. And the disc surface of the discotic structural unit is inclined with respect to the transparent support surface, and the angle formed between the disc surface of the discotic structural unit and the transparent support surface is the depth of the optically anisotropic layer. An optical compensatory sheet, characterized in that the optical compensatory sheet changes in the vertical direction. 2. The optical compensatory sheet according to claim 1, wherein the angle increases in the depth direction of the optically anisotropic layer as the distance from the bottom surface of the optically anisotropic layer increases. 3. The optical compensation sheet according to claim 1, wherein the optically anisotropic layer further contains a cellulose ester. 4. The transparent support has an optically negative uniaxial property and an optical axis in a direction normal to the surface of the transparent support, and further has the following condition: 20 ≦ ｛(nx + ny) / 2 -Nz｝ × d ≦ 400 (where nx and ny represent the in-plane principal refractive index, nz represents the principal refractive index in the thickness direction, d represents the thickness of the support, and The optical compensatory sheet according to claim 1, wherein a unit of the formula is nm. 5. The optical compensation sheet according to claim 1, wherein an alignment film is formed between the optically anisotropic layer and the transparent support. 6. The optical compensation sheet according to claim 5, wherein the alignment film comprises a cured polymer film. 7. A liquid crystal cell consisting of a pair of substrates with transparent electrodes and a twist-aligned nematic liquid crystal enclosed between the substrates, a pair of alignment plates provided on both sides of the liquid crystal cell, and a liquid crystal cell and alignment. In a liquid crystal display device comprising an optical compensation sheet provided between the plate and the plate, the optical compensation sheet comprises a transparent support and an optically anisotropic layer provided thereon, and the optically anisotropic layer is a disc A layer having a negative birefringence composed of a compound having a tick structural unit, wherein the disc surface of the discotic structural unit is inclined with respect to the transparent support surface and is transparent to the disc surface of the discotic structural unit. A liquid crystal display device, wherein an angle formed with a support surface is changed in a depth direction of the optically anisotropic layer. 8. A liquid crystal cell comprising a pair of substrates each having a transparent electrode, a pixel electrode and a color filter, and a twist-aligned nematic liquid crystal enclosed between the substrates, and a pair of alignment plates provided on both sides of the liquid crystal cell. , And a color liquid crystal display device comprising an optical compensation sheet provided between a liquid crystal cell and an alignment plate, wherein the optical compensation sheet comprises a transparent support and an optically anisotropic layer provided thereon, and 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 inclined with respect to the transparent support surface, and A color liquid crystal display device characterized in that an angle formed by a disk surface of a structural unit and a transparent support surface is changed in a depth direction of an optically anisotropic layer.