JPH09179125A - Supporting body with oriented film, optical compensation sheet formed by using the same and color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand a visual field angle and to prevent the degradation in contrast and the occurrence of inversion of gradation or black and white and a hue change, etc., by providing the surface of a transparent base with an oriented film and imparting knurling of a specific height to both ends. SOLUTION: The surface of the transparent base is provided with the oriented film and the knurling (also known as embossing) of >=1 to <=100μ height is imparted to both ends. The height of the knurling is preferably 2 to 50μ and is most preferably 3 to 30μ and the width thereof is 2 to 50mm, more preferably 3 to 30mm and further preferably 5 to 20mm. The position of the knurling may be any, insofar as the position is near the ends of the base and usually, the better result is obtd. in the yield of production in the positions nearer the ends. Weaving is liable to arise when the base is wound if the height of the knurling is too high. On the other hand, the effect of improving the smoothness is not obtainable if the knurling is too low. The production of the base with the oriented film having excellent uniform orientability is made possible if such knurling is imparted to the base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support provided with a knurled alignment film, an optical compensation sheet using the same, and a liquid crystal display device and a color liquid crystal display device having the optical compensation sheet.

[0002]

2. Description of the Related Art A CRT (cathode ray tube) has been mainly used as a display device of OA equipment such as a desktop personal computer and a word processor. 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. An LCD generally includes a liquid crystal cell and a pair of polarizing plates provided on both sides thereof. Most of such LCDs use a twisted nematic liquid crystal.

[0003] LCD display systems can be broadly divided into birefringence mode and optical rotation mode. 2. Description of the Related Art A super twisted nematic liquid crystal display device (hereinafter, referred to as an STN-LCD) using a birefringent mode uses a super twisted nematic liquid crystal having a twist angle exceeding 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 hundred milliseconds) and gray scale display is difficult. Therefore, the display characteristics of the liquid crystal display devices (eg, TFT-LCD and MIM-LCD) using the active elements are difficult. Inferior compared. TFT-LCD and MIM-
In LCDs, twisted nematic liquid crystals having a 90 degree twist angle and positive birefringence are used to display images. In the display mode of the TN-LCD,
High-speed response (several tens of milliseconds) and high contrast are obtained. Thus, the optical rotation mode has many advantages over the birefringence mode and other modes. However, TN
-LCDs have different display colors and display contrast depending on the viewing angle of the liquid crystal display device (viewing angle characteristics).
The display characteristics have not reached the level of the CRT.

To improve the viewing angle characteristics (ie, to increase the viewing angle), Japanese Patent Application Laid-Open No. Hei 4-1992 proposes providing a retardation plate (optical compensation sheet) between a pair of polarizing plates and a liquid crystal cell.
229828 and JP-A-4-258923. The retardation plate proposed in the above-mentioned publication does not exert any optical action from directly in front of the liquid crystal cell because the retardation in the vertical direction is almost 0, but the retardation appears when tilted. This compensates 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 compensatory sheet, a sheet having a negative uniaxial property and an optical axis inclined so as to compensate for the nematic liquid crystal having an optically positive uniaxial property is effective.

JP-A-6-75116 and EP05
The specification of 76304A1 discloses an optical compensation sheet having negative uniaxiality and an optical axis inclined. This optical compensation sheet significantly improved the viewing angle characteristic of contrast, but it was still insufficient as optical compensation in terms of gradation inversion and hue change.

On the other hand, the optical compensation sheet described in EP-0642869 using a discotic compound, in addition to improving the viewing angle characteristics, also provides gradation inversion,
It has many merits such as excellent improvement in hue change and continuous production of long products. However, when a long alignment film is produced by this production method, the discotic compound layer coated thereon has a case in which alignment unevenness is thought to be caused by the thickness unevenness of the support layer, resulting in a high yield. It was the cause of the decrease.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical compensatory sheet having a wide viewing angle and almost no deterioration of contrast, gradation or black / white inversion, and hue change due to a change in viewing angle. An object of the present invention is to provide a color liquid crystal display device having the above, and to provide a support with an alignment film in which the alignment unevenness of the discotic compound due to the thickness unevenness of the support does not occur.

[0008]

Means for Solving the Problems The above-mentioned problems are as follows: (1) An alignment film is provided on a transparent support, and both ends have a height of 1
A support with an alignment film, to which a knurl (also referred to as knurling or embossing) of μ or more and 100 μ or less is provided. (2) The support with an alignment film according to (1), wherein the alignment film is made of crosslinked polyvinyl alcohol or modified polyvinyl alcohol. (3) An alignment film is provided on the transparent support, and the height is 1 at both ends.
An optical compensation sheet, comprising an optically anisotropic layer made of at least one discotic compound on an alignment film of a support with an alignment film, to which a knurling of .mu. (4) 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, The optical compensation sheet according to (3), wherein 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. (5) 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 (4)
The optical compensation sheet according to item 1. (6) A pair of substrates each having a transparent electrode, a pixel electrode, and a color filter, and a liquid crystal cell including a nematic liquid crystal in a twisted orientation sealed between the substrates, a pair of polarizing plates provided on both sides of the liquid crystal cell, and In a color liquid crystal display device including an optical compensation sheet provided between a liquid crystal cell and a polarizing plate, the optical compensation sheet and the polarizing plate on the optical compensation sheet side can be laminated via an adhesive layer and attached to the liquid crystal display device. A color liquid crystal display device, which is cut into a size and mounted. Achieved by

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION 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 value. Examples of such materials include Zeonex (manufactured by Nippon Zeon Co., Ltd.) and ART.
Commercially available products such as ON (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 value such as polycarbonate, polyarylate, polysulfone, and polyethersulfone, the conditions such as solution casting and melt extrusion, as well as stretching conditions in the longitudinal and transverse directions, etc. are set appropriately. Can be obtained.

Assuming that the main refractive indices in the plane of the transparent support (film) are nx, ny, the main refractive index in the thickness direction is nz, and the film thickness is d, the relationship of the triaxial main refractive indices is nz < ny
= Nx (negative uniaxiality), and the formula ｛(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 need to be exactly equal, but it is sufficient if they are approximately equal. In particular,
If | nx-ny | / | nx-nz | ≦ 0.3, 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.

An undercoat layer is preferably provided between the transparent support and the alignment film to increase the adhesive strength. The undercoat layer is generally formed by coating the surface of the transparent support and then coating the transparent support. Examples of the surface treatment method include chemical treatment, mechanical treatment, corona discharge treatment, flame treatment, UV treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and ozone oxidation treatment, but glow discharge treatment is the most preferable. preferable. Various contrivances have been made for the structure of the undercoat layer. A layer (hereinafter, abbreviated as the first undercoat layer) that adheres well to the polymer film is provided as a first layer, and an alignment film is formed thereon as a second layer. A so-called multi-layer method of applying a hydrophilic resin layer (hereinafter abbreviated as an undercoating second layer) which 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 undercoating layer in the multi-layer method, a copolymerization starting material is a monomer selected from vinyl chloride, vinylidene chloride, butadiene, methacrylic acid, acrylic acid, itaconic acid, maleic anhydride, etc. 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-propylene copolymer, butadiene-acrylonitrile copolymer, and blends of these copolymers with halogen-containing resins Products: Acrylic acid methyl ester-acrylonitrile copolymer, acrylic acid ethyl ester-styrene copolymer, methacrylic acid methyl ester-acrylonitrile copolymer, polymethacrylic acid methyl ester, methacrylic acid methyl ester-styrene copolymer, methacrylic acid Butyl ester-styrene copolymer, polymethyl acrylate, poly-α-methyl acrylate, methoxyethyl acrylate, glycidyl polyacrylate, butyl polyacrylate, methyl acrylate And acrylic resins such as polyacrylic acid ethyl ester, acrylic acid-butyl acrylate copolymer, acrylate-butadiene-styrene copolymer and methacrylic acid ester-butadiene-styrene copolymer; polystyrene, poly-α-methyl Styrene, styrene-dimethyl fumarate copolymer, styrene
Maleic anhydride copolymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer and styrene-
Styrene resins such as butadiene-acrylonitrile copolymer; poly-2,6-dimethylphenylene oxide;
Polyvinyl carbazole; poly-p-xylylene; polyvinyl formal; polyvinyl acetal; polyvinyl butyral; polyvinyl phthalate; cellulose triacetate; cellulose butyrate; cellulose butyrate; cellulose phthalate; nylon 6;
Methoxymethyl-6-nylon; nylon-6,10-
Polycapramide; poly-N-butyl-nylon-6-polyethylene sebacate; polybutylene glutarate; polyhexamethylene adipate; polybutylene isophthalate; polyethylene terephthalate; polyethylene adipate; polyethylene adipate terephthalate; polyethylene-2,6-naphthalate; poly Diethylene glycol terephthalate; polyethyleneoxy benzoate; bisphenol A-isophthalate; polyacrylonitrile; bisphenol A-adipate; polyhexamethylene-m-benzenedisulfonamide; polytetramethylenehexamethylene carbonate; polydimethylsiloxane; polyethylenemethylenebis-4-phenyleneca Bonate; and materials such as bisphenol A-polycarbonate It is possible. These oligomers or polymers are described in E.I. H. Immergu
t "Polymer Handbook", IV, 18
7-231, Interscience Pub. Ne
w York, 1966. Examples of the material for the second undercoat layer include gelatin.

In the single layer method, the undercoat layer is formed by expanding the polymer film and interfacially mixing with the hydrophilic undercoat polymer so that good adhesion can be obtained.
As the hydrophilic undercoat polymer used in the present invention, a water-soluble polymer, a cellulose ester, a latex polymer,
A water-soluble polyester or the like can be used. Examples of the water-soluble polymer include gelatin, gelatin derivatives, casein, agar, sodium alginate, starch, and polyvinyl alcohol.
Alcohol, a polyacrylic acid copolymer, a maleic anhydride copolymer, and the like. Examples of the cellulose ester include carboxymethyl cellulose and hydroxyethyl cellulose. Examples of the latex polymer include a vinyl chloride-containing copolymer, a vinylidene chloride-containing copolymer, an acrylate-containing copolymer, a vinyl acetate-containing copolymer, and a butadiene-containing copolymer. Among these, gelatin is most preferred. As the gelatin, generally used ones such as so-called lime-treated gelatin, acid-treated gelatin, enzyme-treated gelatin, gelatin derivatives and modified gelatin can be used. Among these gelatins, lime-treated gelatin and acid-treated gelatin are most preferably used. These gelatins contain various impurities such as 0.11 to 20000 in the production process.
ppm metals (Na, K, Li, Rb, Ca, Mg,
Ba, Ce, Fe, Sn, Pb, Al, Si, Ti, A
u, Ag, Zn, Ni, and other metals, and their ions), ions (F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , sulfate ions,
Nitrate ion, acetate ion, ammonium ion, etc.). Especially in lime-processed gelatin, it is common to contain Ca and Mg ions,
The content is generally 10 to 3000 ppm, preferably 1000 ppm or less from the viewpoint of coating performance of the undercoat,
More preferably, it is 500 ppm or less.

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 alignment film is generally provided on the transparent support or on the undercoat layer. The alignment film functions to define the alignment direction of the liquid crystalline discotic compound provided thereon. The orientation film may be any layer as long as it can impart orientation to the optically anisotropic layer. Preferred examples of the alignment film include a rubbed layer of an organic compound (preferably a polymer), an obliquely-deposited layer of an inorganic compound, and a layer having microgrooves. Examples include a cumulative film formed by a Langmuir-Blodgett method (LB film) of methyl acid or the like, or a layer in which a dielectric is oriented by applying an electric or magnetic field.

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

Of these, alkyl-modified polyvinyl alcohol is particularly preferable, and is excellent in the ability to uniformly align the liquid crystalline discotic compound. This is presumed to be due to strong interaction between the alkyl chains on the alignment film surface and the alkyl side chains of the discotic liquid crystal. 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.
Commercial products such as MP203 and R1130 can be used.

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

Further, the present inventor attaches knurls to both ends of the alignment film support in order to equalize the surface pressure on the alignment film (in the rolled state) due to the uneven thickness of the support. Then, it was found that the above-mentioned alignment unevenness disappears. The width of the knurling is 2 to 50 mm, more preferably 3 to 30 mm,
More preferably, it is 5 to 20 mm and the height is 1 to 1.
00μ is preferable, 2 to 50μ is more preferable, and 3 to
30μ is most preferred. The position of the knurl may be anywhere near the edge of the support, and normally, the closer to the edge, the better from the manufacturing efficiency. Generally, the knurl is formed so that the end of the knurl is 0 to 20 mm inward from the end of the support. Preferably,
It is 0 to 10 mm. If the height of the knurling is too high, winding deviation tends to occur when it is wound, while if it is too low, the effect of improving flatness cannot be obtained. It does not matter whether the knurling is pressed on one side or both sides, but it is possible to prevent crushing of the knurling during heat treatment by applying at a temperature of Tg or higher.
preferable. Such a knurled wheel is disclosed in Japanese Examined Patent Publication No. 57-36.
No. 129 publication. By providing such knurls, it becomes possible to produce a support with an alignment film having excellent uniform alignment.

For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment process for LCD can be used. That is, a method of rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber, or the like can be used to obtain the alignment. 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.

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

Preferred examples of the above discotic compound are shown below.

[0023]

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[0024]

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[0025]

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[0026]

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

The optically anisotropic layer of the present invention is a layer having a negative birefringence composed of a compound having a discotic structural unit, and the surface of the discotic structural unit is inclined with respect to the transparent support surface, and The angle formed by the surface of the discotic structural unit and the surface of the transparent support changes in the depth direction of the optically anisotropic layer. Here, the layer having negative birefringence also includes a layer in which a discotic compound, which is a negative uniaxial molecule, continuously changes in the layer.

The surface angle (tilt angle) of the discotic structural unit generally increases or decreases in the depth direction of the optically anisotropic layer and as the distance from the bottom surface of the optically anisotropic layer increases. Preferably, the angle of inclination increases with increasing distance. Further, as the change of the inclination angle, a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including the continuous increase and the continuous decrease, and an intermittent change including the increase and the decrease may be cited. it can. The intermittent change includes a region where the inclination angle does not change in the thickness direction. It is preferable that the 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.
The liquid crystalline discotic compounds 23a, 23b, and 23c constituting the optically anisotropic layer 23 have a discotic structural unit Pa, Pb, and Pc whose surface 2 is parallel to the surface of the transparent support 21.
1a, 21b, 21c, and their inclination angles θa, θb, θc (the angles formed by the plane of the discotic structural unit and the plane of the transparent support) are equal to the depth from the bottom of the optically anisotropic layer ( It increases in order with the increase in the distance in the thickness direction. 24 represents the normal line of the transparent support. The liquid crystalline discotic compound is a planar molecule, and therefore has only one plane in the molecule, ie, a disk surface (eg, 21a, 21a).
b, 21c).

It is preferable that the inclination angle (angle) is changed within a range of 5 to 85 degrees (particularly within 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 structure unit on the support side substantially corresponds to the minimum value, and the tilt angle (eg, θc) of the discotic structure unit substantially corresponds to the maximum value. I have. Further, the difference between the minimum value and the maximum value of the inclination angle is preferably in the range of 5 to 70 degrees (particularly, 10 to 60 degrees).

The above-mentioned optically anisotropic layer is generally prepared by applying a solution prepared by dissolving a discotic compound and another compound in a solvent onto the alignment film, drying it, and then heating it to a discotic nematic phase forming temperature, and then adjusting the alignment state ( It is obtained by maintaining and cooling the discotic nematic phase). Alternatively, the optically anisotropic layer is formed by applying a solution in which a discotic compound and other compounds (for example, a polymerizable monomer and a photopolymerization initiator) are dissolved in a solvent onto an alignment film, drying, and then discotic nematic It is obtained by heating to a phase forming temperature, polymerizing (by irradiation with UV light or the like), and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably from 70 to
300 ° C is preferable, and 70 to 170 ° C is particularly preferable.

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

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

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

The (color) liquid crystal display device having the optically anisotropic layer (optical compensation sheet) having the variable tilt angle shown in FIG. 2 has a very wide viewing angle, and inversion of a black and white image. Or, the gradation or coloring of the displayed image is hardly generated.

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

The haze of the optically anisotropic layer is generally 5.0.
% Or less. 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
1003-52. When the haze of the optically anisotropic layer is high, light leakage which is considered to be caused by scattering occurs in the black display portion, and as a result, the contrast is reduced. This tendency is remarkable when the incident light is inclined in the normal direction and in the upward direction of the image. Therefore, in order to prevent this, the haze is preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less.

The optically anisotropic layer of the present invention has a minimum absolute retardation value other than 0 in the direction inclined from the normal line of the optical compensation sheet (no optical axis). FIG. 4 shows a typical configuration example of the optical compensation sheet including the optically anisotropic layer of the present invention. In FIG. 4, a transparent support 41 and an alignment film 4 are shown.
2 and discotic compound layer (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 are
The refractive index in the triaxial direction of the optical compensation sheet is expressed, and when viewed from the front, the relationship of n ₁ ≦ n ₃ ≦ n ₂ is satisfied. β is R
It is the inclination from the normal line 44 of the optically anisotropic layer in the direction showing the minimum value of e (retardation). TN-LCD and TF
In order to improve the viewing angle characteristics of the T-LCD, the direction in which the absolute value of Re is the minimum is 5 to 5 from the normal line 44 of the optically anisotropic layer.
~ 50 degrees (average of inclination) It is preferable that the inclination
Furthermore, 10 to 40 degrees is preferable (β above). Furthermore, the above-mentioned 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 the following conditions are further satisfied: 100 ≦ [(n ₃ + n ₂ ) / 2−n ₁ ] × D ≦ 400 (n
m)

The solution for forming the optically anisotropic layer can be prepared by dissolving the discotic compound and the above-mentioned other compound 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, butyl acetate and propylene glycol monomethyl ether; 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 method for applying the above solution includes curtain coating, extrusion coating, roll coating,
Examples include dip coating, spin coating, print coating, spray coating and slide coating. In the present invention, in the case of a mixture of only discotic compounds, a vapor deposition method can also be used. In the present invention, continuous coating is preferred. Therefore, curtain coating, extrusion coating, roll coating and slide coating are preferred. As described above, the 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 liquid crystal phase transition temperature or higher (afterwards 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, R ₄₅₀ / R ₅₅₀ value representing the chromatic dispersion 1.
It is preferably 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.
Only one of the optical compensation sheets may be arranged (that is, RF.
₁ or RF ₂ ). R ₁ indicates the rubbing direction of the optical compensation sheet RF ₁ when viewed from the front, and R ₂ indicates the rubbing direction of the optical compensation sheet RF ₂ . The solid line arrow of the liquid crystal cell TNC indicates the rubbing direction of the substrate on the polarizing plate B side of the liquid crystal cell, and the dotted arrow of the liquid crystal cell TNC indicates the rubbing direction of the substrate on the polarizing plate A side of the liquid crystal cell. PA and P
B represents the polarization axes of the polarizing plates A and B, respectively.

In the liquid crystal display device 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
Represents the rubbing direction of the upper substrate of the liquid crystal cell 61;
Rb represents the rubbing direction of the lower substrate of the liquid crystal cell 61.

The angle (α) between the direction 62M when the direction of the minimum absolute value of retardation is orthographically projected onto the liquid crystal cell and the rubbing direction 61Ra of the upper substrate of the liquid crystal cell is
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 be applied to the case where two optical compensation sheets are used. 1
When two optical compensation sheets are used, the orthogonal projection direction 62M indicating the minimum value of the retardation is the main viewing angle direction (when the sheet is provided above the cell) or the opposite viewing angle direction (the sheet). Is provided below the cell)
Is preferred. The main viewing angle direction is the average twist direction of the liquid crystal molecules in the liquid crystal cell.
When it is twisted 90 degrees counterclockwise as viewed from the direction of the z-axis, it is the minus direction of the x-axis. The opposite viewing angle direction is a direction opposite to the main viewing angle direction.

In the liquid crystal display device of the present invention, as shown in 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, and an optical compensation sheet 82a is arranged between the polarizing plate 83a and the liquid crystal cell 81, and the optical compensation sheet 82b
Are disposed between the polarizing plate 83b and the liquid crystal cell 81. 82Ma is the direction when the direction of the minimum absolute value of the retardation of the optical compensation sheet 82a is orthogonally projected onto the liquid crystal cell, and 82Mb is the direction of the minimum value of the absolute value of the retardation of the optical compensation sheet 82b. Is the direction when orthographically projected on 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.

The angle (α1) 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 to
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. Angle (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 orthogonal projection direction 82Mb showing the minimum value of the retardation and the rubbing direction 81Rb of the lower substrate. The angle (β1) between the orthogonal projection directions 82Ma and 82Mb indicating the minimum value of the retardation is 90 to 18
A range of 0 degrees is preferred.

In the liquid crystal display device of the present invention, 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 103a and 103b are arranged on both sides of the liquid crystal cell 101, and optical compensation sheets 102a and 102b are arranged between the polarizing plate 103a and the liquid crystal cell 101. 102Ma is the direction when the direction of the minimum absolute value of the retardation of the optical compensation sheet 102a is orthogonally projected onto the liquid crystal cell, and 102Mb is the optical compensation sheet 1
The direction of the absolute value of the absolute value of the retardation of 02b is the direction when orthogonally projected onto 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. 104 denotes 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) 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 direction 102Ma indicating the minimum value of the retardation and the rubbing direction 101Ra of the upper substrate, and the angle (α4) is the angle lower than the orthographic direction 102Mb indicating the minimum value of the retardation. This is an 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 retardation and the rubbing direction of the substrate of the liquid crystal cell can be applied to the 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, 128b and a pair of optical compensatory sheets 127a, 127b disposed between the liquid crystal cell and the polarizer constitute 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 filter having high color purity, dimensional accuracy and 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 Japan Society for the Promotion of Science, 142th Committee (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 approximately 90 ° C. between the upper and lower substrates of the liquid crystal cell, the incident linearly polarized light has a 90 ° C. polarization direction due to the optical rotation of the liquid crystal cell in the absence of an 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 is applied, the long axis of the liquid crystal molecules changes its direction in the electric field and is arranged perpendicular to the electrode surface, so that the optical rotation 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 the defects (disclination) in the alignment of the liquid crystal molecules due to this electric field, it is preferable to give the liquid crystal molecules a pretilt angle in advance. The pretilt angle is preferably 5 ° C or less, and more preferably 2 ° C to 4 ° C.
Is preferred. Regarding the twist angle and pretilt angle, see “Liquid Crystal Application” edited by Koji Okano and Shunsuke Kobayashi (Baifukan,
Pages 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 in (p. 7), as d increases, the contrast is improved, but the response speed is slow and the viewing angle is also small. Therefore, the range of 0.3 to 1.0 μm is preferable. The range of 3 to 0.6 μm is more preferable.

The signal applied to the color liquid crystal display device of the present invention is, for example, “Liquid Crystal Device Handbook” edited by Japan Society for the Promotion of Science, 142th Committee (Nikkan Kogyo Shimbun, page 387-
465 pages) or Koji Okano and Shunsuke Kobayashi, "Liquid Crystals"
As described in “Applied Edition” (Baifukan, pp. 85-105), etc., the alternating current of 5-100 Hz and the voltage of 20
V or less, preferably 8 V or less. For example, in the normally white mode, the applied voltage is 0 to 1.5 V
For bright display, 1.5V to 3.0V for halftone display, 3.0V
The dark display is generally performed as described above.

The material of the polarizing plate which 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 is defined by ｛(nx + n
y) / 2−nz｝ × d. In general, the optical compensation sheet is mounted by laminating the polarizing plate on the optical compensation sheet side via an adhesive layer and cutting it into a size that can be mounted in a liquid crystal display device. At this time, it is necessary to stack and cut so that the optical axes of the optical compensation sheet, the polarizing plate and the liquid crystal cell have optimum viewing angle characteristics.

[0057]

【Example】

Example 1 <Preparation of support with alignment film> Gelatin thin film (0.1 μm)
Was coated on a triacetyl cellulose film having a thickness of 100 μm (manufactured by Fuji Photo Film Co., Ltd.) with a bar coater to apply an alignment film-forming coating solution having the following composition to 90 ° C. After drying with warm air, under this temperature atmosphere, the edges of the knurls were placed 2 mm inward from the sides of the support so that both ends of the support had a height of 20 μ and a width of 7 m.
By applying m rollet and winding it around the core,
A support with an alignment film having a length of 1000 m was produced. <Coating liquid for forming alignment film> Polyvinyl alcohol derivative (below) 10 kg Water 371 kg Gthanol 119 kg Glutaraldehyde (crosslinking agent) 500 g

[0058]

Embedded image

When the in-plane main refractive index is nx, ny, the thickness direction refractive index nz, and the thickness is d, | nx-ny | xd, {(nx + ny) /
2-nz} * d was determined (see FIG. 1). The thickness was measured using a micrometer, and the Re value from the normal direction and from the direction of 40 ° in the MD direction to the normal direction and 40 ° in the opposite direction was measured using an ellipsometer (AEP-100,
Measured by Shimadzu Corporation, and calculated above |
nx-ny | xd, {(nx + ny) / 2-nz} xd
It was determined. Of the above triacetyl cellulose film
nx−ny | × d is 3 nm, and {(nx + ny) / 2−
nz} xd was 40 nm. Therefore, the triacetyl cellulose film was almost negatively uniaxial, and the optical axis was almost in the direction of the film normal.

After rubbing the alignment film, 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.) 0.4 g, cellulose acetate butyrate (CAB531-1; manufactured by Eastman Chemical Co.) 0.
A coating solution obtained by dissolving 05 g and 0.01 g of a photopolymerization initiator (Irgacure-907; manufactured by Ciba Geigy) in 3.65 g of methyl ethyl ketone was applied with a wire bar (# 4 bar), After sticking to a metal frame and fixing and heating in a high temperature bath at 120 ° C. for 3 minutes to orient the discotic compound, it is allowed to cool to room temperature and the thickness is 1.
A layer (optically anisotropic layer) containing a discotic compound having a thickness of 8 μm was formed. Thus, the optical compensation sheet (OCS-A) of the present invention having the optically anisotropic layer 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). The sample was left to stand in an OsO ₄ atmosphere for 48 hours and stained. The obtained dyed film was observed with a transmission electron microscope (TEM), and a micrograph was obtained. In the dyed film, the discotic compound TE-
Eight (8, m = 4) acryloyl groups were stained and recognized as photographic images. From this photograph, the discotic compound of the optically anisotropic layer was inclined from the surface of the transparent support, and the inclination angle was increased from 5 to 65 degrees with increasing distance in the depth direction from the bottom of the optically anisotropic layer. A continuous increase was observed.

Example 2 After rubbing the 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; Toa) Synthetic Co., Ltd.) 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.) 0.01 g were dissolved in 3.65 g of methyl ethyl ketone to obtain a wire. Apply with a bar (# 4
Bar), and fix it by sticking it to a metal frame and heating it in a high temperature bath at 120 ° C for 3 minutes to orient the discotic compound, and then at 120 ° C for 1 minute using a high pressure mercury lamp.
It was irradiated with V and allowed to cool to room temperature to prepare 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.

Regarding the optical compensation sheet (OCS-B) of the present invention thus obtained, in a plane including the rubbing axis and perpendicular to the surface of the retardation plate, in the normal direction ± 55 °, at intervals of 5 °. , Letterization value to ellipsometer (A
EP-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 characteristics of the optically anisotropic layer (relationship between Re and the measurement angle) were as shown in FIG. When the result of FIG. 13 is simulated, the obtained optical anisotropic layer has negative birefringence, the surface of the discotic compound is tilted from the surface of the support, and the tilt (tilt angle) is from 20 degrees to 50 degrees. It turned out that it changed continuously up to the degree.

Example 3 After rubbing the alignment film, 1.8 g of the above-mentioned liquid crystalline discotic compound TE-8 (8, m = 4) (the above compound example number), ethylene glycol-modified trimethylolpropane tri Acrylate (V # 360; manufactured by Osaka Organic Chemical Industry Co., Ltd.) 0.2 g, cellulose acetate butyrate (CAB551-0.2; manufactured by Eastman Chemical Co.) 0.04 g, photopolymerization initiator (Irgacure-907; Ciba)・ Geigy Co., Ltd.) 0.06 g and sensitizer (Kayakyu DETX, Nippon Kayaku Co., Ltd.) 0.02
Coating solution obtained by dissolving g in 3.43 g of methyl ethyl ketone is applied with a wire bar (# 3 bar), stuck on a metal frame and fixed, and heated in a high temperature bath at 120 ° C for 3 minutes. Then, after orienting the discotic compound, 1
1 at high temperature mercury lamp (120W / cm) at 20 ℃
It was irradiated with UV for 2 seconds 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 thus obtained, the retardation value of the ellipsometer (in the plane perpendicular to the retardation plate surface including the rubbing axis) was measured in the same manner as in Example 2. 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. As a result of these measurements, the obtained optically anisotropic layer had negative birefringence, the discotic compound surface was tilted from the surface of the support, and the tilt (tilt angle) was continuous from 20 degrees to 70 degrees. It turned out that it was changing.

Example 4 After rubbing the alignment film, 1.75 g of the above-mentioned liquid crystalline discotic compound TE-8 (8, m = 4) (Example number of the compound), α-acrolein-ω-phenoxy was used. -0.25 g of polyoxyethylene (AMP60G; manufactured by Shin-Nakamura Chemical Co., Ltd.), 0.05 g of cellulose acetate butyrate (CAB500-5; manufactured by Eastman Chemical Company), and a photopolymerization initiator (Irgacure-9)
07; manufactured by Ciba Geigy) 0.01 g, 3.43 g
The coating solution obtained by dissolving in methyl ethyl ketone of No. 3 is applied with a wire bar (# 3 bar), fixed on a metal frame and heated for 3 minutes in a high temperature bath at 120 ° C to orient the discotic compound. Then, UV irradiation is performed for 1 second at 120 ° C. using a high pressure mercury lamp (120 W / cm),
After cooling to room temperature, an optical compensation sheet (OCS-D) of the present invention having a layer (optically anisotropic layer) containing a discotic compound having a thickness of 1.8 μm was produced.

The retardation value of the thus obtained optical compensation sheet (OCS-D) of the present invention (OCS-D) on the plane including the rubbing axis and perpendicular to the retardation plate surface was measured in the same manner as in Example 2. 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. By these measurements, the obtained optically anisotropic layer has negative birefringence, the discotic compound surface is inclined from the surface of the support, and the inclination (tilt angle) is continuous from 20 degrees to 40 degrees. It turned out that it was changing.

Example 5 After rubbing the alignment film, 1.6 g of the above-mentioned liquid crystalline discotic compound TE-8 (8, m = 4) (the above compound example number), ethylene glycol-modified trimethylolpropane tri Acrylate (V # 360; manufactured by Osaka Organic Chemical Industry Co., Ltd.) 0.16 g, cellulose acetate butyrate (CAB531-1.0; manufactured by Eastman Chemical Co.) 0.009 g, cellulose acetate butyrate (CAB551-0.2). Eastman Chemical Co., Ltd.) 0.036 g, photopolymerization initiator (Irgacure
907; manufactured by Ciba Geigy) 0.005 g and a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.00
2 g was added with 2.95 g of methyl ethyl ketone and 0.155
g of propylene glycol monomethyl ether (MF
G: A coating solution obtained by dissolving in Japan Emulsifier Co., Ltd.
Apply it with a wire bar (# 3 bar), attach it to a metal frame, fix it, and heat for 3 minutes in a high-temperature bath at 120 ° C to orient the discotic compound, and then keep the high-pressure mercury lamp (120W) at 120 ° C. / Cm) for 1 second and then allowed to cool to room temperature, and an optical compensation sheet (OCS-F) of the present invention having a layer (optically anisotropic layer) containing a discotic compound having a thickness of 2.0 μm. Was produced.

With respect to the optical compensation sheet (OCS-F) of the present invention thus obtained, the retardation value was measured on the surface including the rubbing axis and perpendicular to the retardation plate surface in the same manner as in Example 2 by the 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, the discotic compound surface is tilted from the support surface, and the tilt (tilt angle) is continuous from 20 degrees to 50 degrees. It turned out that it was changing.

<Preparation of Support with Alignment Film> On a triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 100 μm coated with a gelatin thin film (0.1 μm), the same as in the example was carried out. A coating solution for forming an alignment film having a composition is applied with a bar coater, dried with hot air at 90 ° C., and then wound on a winding core to give a length of 1000.
A support with an alignment film of m was prepared.

Comparative Example 1 After rubbing the 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; Toa) Synthetic Co., Ltd.) 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.) 0.01 g were dissolved in 3.65 g of methyl ethyl ketone to obtain a wire. Apply with a bar (# 4
Bar), and fix it by sticking it to a metal frame and heating it in a high temperature bath at 120 ° C for 3 minutes to orient the discotic compound, and then at 120 ° C for 1 minute using a high pressure mercury lamp.
It was irradiated with V and allowed to cool to room temperature to prepare an optical compensation sheet (OCS-G) 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-B) of the present invention thus obtained, the retardation value was measured on the plane including the rubbing axis and perpendicular to the surface of the retardation plate by the ellipsometer (as in Example 2). 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. By these measurements, the optical characteristics (Re
And the measurement angle) are exactly the same as in Example 1 (see FIG. 1).
3), the obtained optically anisotropic layer has negative birefringence, the discotic compound surface is inclined from the support surface, and the inclination (tilt angle) continuously changes from 20 degrees to 50 degrees. I found out that

Comparative Example 2 Similar to Comparative Example 1, after rubbing the alignment film, the above-mentioned liquid crystalline discotic compound TE-8 was used.
Methyl ethyl ketone was added to (8, m = 6) (the above compound example number) to make a total solution of 10 wt%, and the solution was applied by spin coating at 2000 rpm. Then, the coating layer is heated to 180 ° C. and heat-treated, and then 18
UV irradiation for 1 minute at 0 ° C. using a high pressure mercury lamp, cooling to room temperature, and an optical compensation sheet (O 2) having a layer (optically anisotropic layer) containing a discotic compound having a thickness of 1.0 μm.
CS-G) was prepared.

With respect to the optical compensation sheet (OCS-G) thus obtained, the retardation value was measured on the surface including the rubbing axis and perpendicular to the retardation plate surface in the same manner as in Example 2 by using an ellipsometer (AEP-100). (Manufactured by Shimadzu Corporation), 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 tilted from the surface of the support.

[Evaluation of Optical Compensation Sheet] Examples 1 to 1 above
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) Alignment unevenness A pair of polarizing plates are arranged in a crossed Nicol pattern, and an optical compensation sheet is formed.
The film was sandwiched between the pair of polarizing plates so that the coating direction intersected with the polarizing axis of the polarizing plate at 45 °, and the unevenness of orientation was visually evaluated.

Table 1 ──────────────────────────────────── Sheet ^* Optical axis Inclination angle Re Minimum direction ^** Alignment unevenness No. Change (degree) Angle (degree) ───────────────────────────────────── Example 1 OCS-A None 5-65 30 None Example 2 OCS-B None 20-50 35 None Example 3 OCS-C None 20-70 40 None Example 4 OCS-D None 20-40 25 None Example 5 OCS-F None 20 -50 33 None ──────────────────────────────────── Comparative Example 1 OCS-G None 20-50 35 Yes Comparative Example 2 OCS-H Yes --38 Yes Yes ───────────────────────────────────── Remarks ) ^* : Re is in the direction of 0 ^** : “None” means that there is no alignment unevenness in all 1000 m of the alignment film support. “Available” means that, in 1000 m of the alignment film support, alignment unevenness occurs in several hundred m on the winding core side.

Examples 6 to 8 and Comparative Examples 3 to 4 (Production of Liquid Crystal Display Device) One of the liquid crystal cells in which a nematic liquid crystal was sandwiched at a twist angle of 90 ° C. and a gap size of 4.5 μm. On the surface, Examples 2, 3 and 5
(Comparative Examples 6 to 8) and Comparative Example 2 (Comparative Example 3), the two optical compensation sheets were laminated and adhered to each other to manufacture a liquid crystal display device (see FIG. 10;
The part where there is no unevenness in the orientation was pasted). However, the angle (α3) formed by the projection direction (rubbing direction, 102 Ma in FIG. 11) showing the minimum retardation of the lower optical compensation sheet and the rubbing direction (101 Ra in FIG. 11) of the upper substrate.
Is 180 degrees and the projection direction (rubbing direction,
102Mb in FIG. 11) and the rubbing direction of the upper substrate (see FIG. 1).
The above laminate was placed on the liquid crystal cell so that the angle (α4) formed by 1 and 101 Rb) was 0 degree. Further, a pair of polarizing plates was attached to both sides of a liquid crystal cell having an optical compensation sheet so that two polarizing axes were orthogonal to each other. As the protective film for the polarizing plate, a triacetyl cellulose film having a retardation of 40 nm (a value defined by {(nx + ny) / 2-nz} × d as described above) was used. The obtained TN-LCD was set for a normally white mode. As Comparative Example 4, a TN-LCD without the above optical compensation sheet was also manufactured.

A rectangular wave voltage of 55 Hz was applied to the obtained TN-LCD at 0 to 5 V, and the contrast from the front direction and the directions tilted in the up / down and left / right directions were measured.
Using a spectrometer (LCD-5000, manufactured by Otsuka Electronics Co., Ltd.), the front contrast (T _0V / T _5V ) and the upper / lower and left / right viewing angles at which the contrast is 10 or more were determined. Table 2 shows the obtained results.

Table 2 ──────────────────────────────────── Seat Front Contrast Visual Angle (degree) No. Up and down Left and right ──────────────────────────────────── Example 6 OCS-B 100 or more 130 125 Example 7 OCS-C 100 or higher 130 130 Example 8 OCS-F 100 or higher 120 120 ───────────────────────────────── Comparative Example 3 OCS-G 100 or more 85 100 Comparative Example 4 None 100 or more 61 95 ───────────────────────────── ────────

As is clear from Tables 1 and 2, the support with an alignment film of the present invention enables highly uniform alignment of the discotic compound, and the optical compensation sheet using the same has the effect of widening the viewing angle. Therefore, the viewing angle can be expanded without lowering the front contrast.

Examples 9 and 10 (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,
The optical compensation sheet 2 used in Examples 3 and 5 (Examples 9 and 10, respectively) so as to sandwich the liquid crystal cell.
I put on one. 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 5 TFT type liquid crystal color television 6E-C3 manufactured by Sharp Corporation.
The polarizing plate of 1 was peeled off, and two sheets of the same polarizing plate used in Example 9 were attached so as to sandwich the liquid crystal cell so that the polarization axes thereof were orthogonal to each other, to produce a color liquid crystal display device.

With the obtained color liquid crystal display device, white display and black display are performed, and the contrast ratio in up, down, left and right is 1
A viewing 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. Table 3 shows the obtained results.

Table 3 ──────────────────────────────────── Seat visual angle (degree) No. Up and down left and right ──────────────────────────────────── Example 9 OCS-C 123 115 Example 10 OCS -E 130 120 ──────────────────────────────────── Comparative Example 5 None 50 70 70 ──── ────────────────────────────────

As is apparent from Table 3, Examples 9 and 1
The color liquid crystal display device of No. 0, compared with that of Comparative Example 5,
It can be seen that the viewing angle seen from the contrast in monochrome display is greatly expanded. When a video signal is input to the color liquid crystal display device of Comparative Example 5 to display a full-color image, the image is whitish when viewed from above, and the image is yellowish in its entirety, and when viewed from below, the black display portion is short. Flipped over. When viewed from the left and right, there is no reversal in the black display portion, but the contrast is reduced as a whole and the image is yellowish, and the image quality is significantly reduced when the viewing angle is increased. On the other hand, in the color liquid crystal display devices obtained in Examples 9 and 10, 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, the yellowing of the image was slight, and the deterioration of the image quality due to the increase in the viewing angle was small.

[0086]

As described above, the use of the support with an alignment film of the present invention makes it possible to obtain an optical compensation sheet with a high yield. 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 part is reversed and the gradation is reversed with the increase of the viewing angle. The occurrence of coloring of the image is greatly reduced, and excellent viewing angle characteristics are exhibited. In particular, the viewing angle characteristics of a liquid crystal display device having a non-linear active element such as a TFT 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 the 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 compensatory sheet of the present invention and a relationship between triaxial principal 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.
3B is a graph showing the relationship between Re and the viewing angle of the optically anisotropic layers of (B) and (OCS-G).

[Explanation of symbols]

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

Claims (6)

[Claims] 1. A support with an alignment film, wherein an alignment film is provided on a transparent support, and knurls having a height of 1 μ or more and 100 μ or less are provided on both ends. 2. The support with an alignment film according to claim 1, wherein the alignment film is made of crosslinked polyvinyl alcohol or modified polyvinyl alcohol. 3. At least one discotic compound on the alignment film of the support with an alignment film, in which an alignment film is provided on a transparent support, and knurls having a height of 1 μ or more and 100 μ or less are provided on both ends. An optical compensation sheet having an optically anisotropic layer of 4. 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. The optical compensation sheet according to claim 3, wherein 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. 5. The optical compensation sheet according to claim 4, 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. 6. A liquid crystal cell comprising a pair of substrates each having a transparent electrode, a pixel electrode and a color filter, and a nematic liquid crystal in a twisted orientation enclosed between the substrates, and a pair of polarizing 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 a polarizing plate, the optical compensation sheet and the polarizing plate on the optical compensation sheet side are laminated via an adhesive layer to form a liquid crystal display device. A color liquid crystal display device, which is cut into a size that can be mounted and then mounted.