JP2008164921A - Optical compensation film and method of manufacturing the same, polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical compensation film the durability of which under high temperature and high humidity is improved without spoiling alignment property and optical compensation function, and also to provide: a polarizing plate on which the optical compensation film and a polarizer are stuck; and a liquid crystal display having an excellent viewing angle characteristic without spoiling display quality even under high temperature and high humidity. <P>SOLUTION: The optical compensation film is characterized by having an alignment layer for aligning a liquid crystal compound and an optically anisotropic layer composed of the liquid crystal compound on a supporting body, wherein the alignment layer contains at least one of an epoxy compound, isocyanate compound and aziridine compound in an amount of 0.10 to 30.0 mass% with respect to the total solid part of the alignment layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical compensation film in which a liquid crystal compound is aligned and fixed, and a method for producing the same, which are preferably used for a polarizing plate and a liquid crystal display device having the same.

Optical films in which liquid crystal compounds are highly oriented and fixed are being developed in various applications such as optical compensation films for liquid crystal display devices, brightness enhancement films, and optical correction films for projection display devices. The development of the device as an optical compensation film is remarkable.
Here, the liquid crystal display device mainly includes a polarizing plate and a liquid crystal cell. For example, in a currently used Twisted Nematic mode (TN mode) thin film transistor (TFT) liquid crystal display device, an optical compensation sheet is used. Is inserted between the polarizing plate and the liquid crystal cell to realize a liquid crystal display device with high display quality. However, this method has a problem that the liquid crystal display device itself becomes thick.

In order to solve the problem that the liquid crystal display device becomes thick, in Patent Document 1, the liquid crystal display device is made thicker by using an elliptically polarizing plate having a retardation film on one side of the polarizing film and a protective film on the other side. However, it has been proposed to increase the front contrast. However, the proposed retardation film (optical compensation sheet) has a problem that a sufficient viewing angle improvement effect cannot be obtained and the display quality of the liquid crystal display device is lowered.
Therefore, in order to solve the problem relating to the viewing angle without increasing the thickness of the liquid crystal display device, that is, to prevent deterioration in display quality, in Patent Document 2 and Patent Document 3, a discotic (discotic) compound is formed on a transparent support. An optical compensation sheet coated with an optically anisotropic layer formed from the above has been proposed to be used directly as a protective film for a polarizing plate.

However, in these proposals, an optical compensation sheet has been developed mainly assuming a small-sized or medium-sized liquid crystal display device of 15 inches or less, so that a large liquid crystal having a large size of 17 inches or more and high brightness in recent years. Even if it is mounted on a polarizing plate of a display device, there is a problem that unevenness occurs on the panel and it cannot be applied. For this reason, it is necessary to further develop an optical film that copes with light leakage unevenness in response to an increase in size and brightness.
In order to improve this unevenness, Patent Document 4 proposes that a polymerizable liquid crystal contains a leveling agent. However, this proposal is effective only when the polymerizable liquid crystal is homogeneously aligned, and cannot be applied to complicated alignment including hybrid alignment.

Therefore, as an optical compensation film that can be applied to complicated alignment, a repeating unit derived from a liquid crystal compound, a fluoroaliphatic group-containing (meth) acrylate monomer, and a polyoxyalkylene (meth) acrylate monomer on a support. There has been proposed an optical compensation film having an optically anisotropic layer containing a fluoroaliphatic group-containing copolymer containing (see Patent Document 5).
However, in the optical compensation film, since the alignment film provided for aligning the liquid crystal compound of the optically anisotropic layer easily absorbs moisture, the polarizing plate on which the optical compensation film and the polarizer are bonded is mounted. When the liquid crystal display device is placed under high temperature and high humidity, the polarizing plate absorbs water, expands and contracts, and distortion occurs between the liquid crystal cell and the glass substrate.
Further, the optically anisotropic layer that is thinner and harder than the support or the polarizer cannot withstand the distortion, and thus cracks, resulting in the deterioration of display quality, so there is room for improvement in improving durability. was there.

  Therefore, an optical compensation film having a high durability when the polarizing plate is prepared and placed under high humidity and having good orientation, a method for producing the same, a polarizing plate using the optical compensation film, and At present, it is strongly desired to develop a liquid crystal display device using the polarizing plate.

JP-A-2-247602 Japanese Patent Laid-Open No. 7-191217 European Patent No. 91656 JP-A-11-148080 JP 2004-198511 A

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention is an optical compensation film having improved durability under high temperature and high humidity without impairing the orientation and optical compensation function, a polarizing plate having the optical compensation film of the present invention and a polarizer attached thereto, Another object of the present invention is to provide a liquid crystal display device having good viewing angle characteristics without deteriorating display quality even under high temperature and high humidity.

As a result of intensive studies, the inventors of the present invention include a predetermined amount of a compound that reacts with a radical polymerizable group of a polymer compound contained in the alignment film layer and has two or more vinyl groups in order to solve the above problem. Thus, it has been found that, under high temperature and high humidity, the phenomenon that cracks occur in the optically anisotropic layer can be reduced and durability can be improved.
This invention is based on the said knowledge by the present inventors, and the means for solving the said subject are as follows. That is,
<1> An alignment film layer for aligning a liquid crystal compound and an optically anisotropic layer composed of a liquid crystal compound are provided on a support, and the alignment film layer includes an epoxy compound, an isocyanate compound, and An optical compensation film comprising 0.10 to 30.0% by mass of at least one of an aziridine compound with respect to the total solid content of the alignment layer.
<2> A method for producing an optical film, comprising producing the optical compensation film according to <1>.
<3> A polarizing plate comprising the optical compensation film according to <1>.
<4> A liquid crystal display device comprising the polarizing plate according to <3>.

  According to the present invention, the above-mentioned problems in the prior art can be solved, and the optical compensation film having improved durability under high temperature and high humidity without impairing the orientation and the optical compensation function, the optical compensation film and the polarization It is possible to provide a polarizing plate to which a child is attached and a liquid crystal display device having good viewing angle characteristics without deteriorating display quality even under high temperature and high humidity.

  Hereinafter, the optical compensation film according to the present invention, the production method thereof, the polarizing plate, and the liquid crystal display device will be described in detail.

(Optical compensation film)
The optical compensation film of the present invention comprises, on a support, an alignment film layer containing at least one of an epoxy compound, an isocyanate compound and an aziridine compound, and an optical anisotropic layer containing a liquid crystal compound, at least in this order. Laminated.

[Support]
The support is preferably glass or a transparent polymer film, and preferably has a light transmittance of 80% or more.
Examples of the polymer constituting the polymer film include cellulose ester, norbornene-based polymer, polymethyl methacrylate, and the like. Examples of the cellulose ester include cellulose acetate and cellulose diacetate.
A commercially available polymer may be used as the polymer. Examples of the commercially available polymer include norbornene-based polymers such as Arton and Zeonex (both are trade names).
Among the polymers exemplified above, cellulose ester is preferable, and cellulose lower fatty acid ester is more preferable. Here, the lower fatty acid means a fatty acid having 6 or less carbon atoms, and is cellulose acetate (2 carbon atoms), cellulose propionate (3 carbon atoms), or cellulose butyrate (4 carbon atoms). Is preferred, and cellulose acetate is particularly preferred.

The support may be a conventionally known polymer such as polycarbonate or polysulfone that easily develops birefringence, for example, as described in WO '00 / 26705. Thus, if the expression of birefringence is controlled, it can be used for the optical compensation film of the present invention.
When the optical compensation film of the present invention is used for a protective film used for a polarizing plate or a retardation film, the polymer film of the support is cellulose having an acetylation degree of 55.0 to 62.5%. Acetate is preferably used, more preferably 57.0 to 62.0% cellulose acetate.

Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose, and is determined, for example, by measuring and calculating the degree of acetylation in ASTM: D-817-91 (testing method for cellulose acetate and the like).
The viscosity average degree of polymerization (DP) of cellulose acetate is preferably 250 or more, and more preferably 290 or more. The cellulose acetate preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. Specifically, the value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.0 to 1.65, and 1.0 to 1.6. Particularly preferred.

In the cellulose acetate, the hydroxyl groups at the 2-position, 3-position and 6-position of cellulose are not evenly substituted, but the substitution degree at the 6-position tends to be small. For this reason, in the polymer film used for this invention, it is preferable that the 6th-position substitution degree of a cellulose is the same or more compared with 2nd-position and 3rd-position.
The ratio of the substitution degree at the 6-position to the total substitution degree at the 2-position, the 3-position, and the 6-position of the cellulose acetate is preferably 30 to 40%, more preferably 31 to 40%, It is especially preferable that it is 32 to 40%. The substitution degree at the 6-position is preferably 0.88 or more. The degree of substitution at each position can be measured by NMR.
Cellulose acetate having a high degree of substitution at the 6-position is, for example, Synthesis Example 1 described in Paragraph Nos. 0043 to 0044, Synthesis Example 2 described in Paragraph Nos. 0048 to 0049 and Paragraph Nos. 0051 to 0052 of JP-A No. 11-5851. It can be synthesized with reference to the method of Synthesis Example 3 described in 1.

<Alignment film layer>
The alignment film (layer) of the present invention is preferably a layer composed of a crosslinked polymer compound. For example, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. A plurality of these combinations can also be used. Examples of the polymer include compounds described in paragraph No. [0022] of JP-A-8-338913.

Examples of the polymer compound include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol, and modified polyvinyl alcohol, poly (N-methylolacrylamide), styrene / vinyltoluene. Copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene, polycarbonate, etc. And polymers such as silane coupling agents.
Among the above-mentioned polymer compounds, water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol described later are preferable, and gelatin, polyvinyl alcohol, and modified polymers are preferable. Polyvinyl alcohol is more preferable, polyvinyl alcohol is more preferable, and modified polyvinyl alcohol is particularly preferable.

  In the present invention, as a cross-linking agent for the polymer compound (preferably polyvinyl alcohol) that forms the alignment film layer, at least one of an epoxy compound, an isocyanate compound, and an aziridine compound can be used. It is preferable that 0.10-30.0 mass% is contained with respect to the polymer total solid of the said alignment film layer.

  Moreover, crosslinking agents other than an epoxy-type compound, an isocyanate type compound, and an aziridine type compound can also be used together. Specific examples include aldehyde compounds, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxy groups, active vinyl compounds, active halogen compounds, isoxazole and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraph numbers [0023] to [0024] of JP-A-2002-62426.

  As the epoxy compound, an epoxy compound having at least two glycidyl groups in the molecule is preferable. Specific examples of the epoxy compound having two or more glycidyl groups in the molecule include polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, and diglycerin diester. Glycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F Diglycidyl ether, resorcin diglycidyl ether, glycerin triglycidyl ether, trimethylol group Pantriglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxy Examples include silane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane.

  As the isocyanate compound, an isocyanate compound having at least two isocyanate groups in the molecule is preferable. Specific examples of the isocyanate compound having two or more isocyanate groups in the molecule include tris [3- (1-aziridinyl) propionic acid] trimethylolpropane, 2,4-tolylene diisocyanate, phenylene diisocyanate, 4,4 Examples thereof include monomers such as' -diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, oligomers thereof, and a reaction product of these compounds with a polyol. Examples of the polyol used for this purpose include 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and the like. The isocyanate compound is sold, for example, by Dainippon Ink & Chemicals, Inc. under the trademark “Hydran Assister”.

  The aziridine-based compound is a compound having a three-membered skeleton composed of one nitrogen atom and two carbon atoms, also called ethyleneimine, and is preferably an aziridine-based compound having at least two aziridine rings in the molecule. . Specific examples of the aziridine compound having two or more aziridine rings in the molecule include diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate. , Tetramethylolmethane tri-β-aziridinylpropionate, toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, isophthaloylbis-1- (2-methylaziridine), tris Examples include -1- (2-methylaziridine) phosphine, tris-1- (2-methylaziridine) phosphine oxide, trimethylolpropane tri-β- (2-methylaziridine) propionate.

  The epoxy compound, isocyanate compound and aziridine compound are most preferably epoxy compound from the viewpoint of ease of dissolution in water and good pot life, specifically ethylene glycol diglycidyl ether, diethylene glycol diglycidyl. Examples include ether, triethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, and tripropylene glycol diglycidyl ether. Among these, low chlorine type EX810 and EX920 sold by Nagase ChemteX Corporation are preferable.

  The alignment film layer preferably contains 0.1 to 30.0% by mass of at least one of the epoxy compound, the isocyanate compound, and the aziridine compound with respect to the total solid content of the alignment film layer. More preferably, it is contained in a proportion of 1.0% by mass or more and less than 25.0% by mass, particularly preferably in a proportion of 3.0% by mass or more and less than 20.0% by mass. When the content is less than 0.1% by mass, the alignment layer film swells with moisture under high temperature and high humidity, and an optical compensation film having good durability cannot be obtained. If it is 30% by mass or more, poor orientation occurs, and the optical compensation function of the optical compensation film is impaired.

―Degree of saponification―
Examples of the polyvinyl alcohol and the modified polyvinyl alcohol include those having a saponification degree of 70 to 100%, generally those having a saponification degree of 80 to 100%, and more preferably those having a saponification degree of 85 to 95%. The degree of polymerization is preferably in the range of 100 to 3,000.

  The modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of modifying groups include hydrophilic groups (carboxy groups, sulfo groups, phosphono groups, amino groups, ammonium groups, amide groups, mercapto groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, and carbon atoms substituted with fluorine atoms. Examples thereof include a hydrogen group, sulfide group, polymerizable group (unsaturated polymerizable group, epoxy group, aziridinyl group, etc.), alkoxysilyl group (trialkoxy, dialkoxy, monoalkoxy) and the like. Specific examples of these modified polyvinyl alcohol compounds include, for example, paragraph numbers [0071] to [0095] of JP-A-9-152509, paragraph number [0074] of JP-A 2000-56310, 2000-155216. Examples include the compounds described in paragraph numbers [0022] to [0145] of the publication and paragraph numbers [0018] to [0022] of the publication 2002-62426.

  Moreover, when performing alignment by light irradiation, it is necessary to have a photo-alignment group which expresses a photo-alignment function in the molecule. Examples of these photo-alignment groups include “Liquid Crystal” written by Masaki Hasegawa, Volume 3 (1) p. 3-16 (1999), a photo-alignment group having a C = C bond and exhibiting a photo-alignment function by a photodimerization reaction (for example, polyene group, stilbene group, stilbazole group, stilbazolium group, cinnamoyl group) , Hemithioindigo group, chalcone group, and the like) and photo-alignable groups having a C═O bond and exhibiting a photo-alignment function by a photodimerization reaction (for example, groups having a structure such as a benzophenone group and a coumarin group). Specific examples include those described in paragraphs [0021] and the like of JP-A Nos. 2000-122069 and 2002-317013.

―Crosslinking agent―
Examples of cross-linking agents for polymers (preferably water-soluble polymers, more preferably polyvinyl alcohol or modified polyvinyl alcohol) used in the alignment film include aldehydes, N-methylol compounds, dioxane derivatives, and carboxy groups by activating them. Compounds that act, active vinyl compounds, active halogen compounds, isoxazoles and dialdehyde starches are included. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraph numbers [0023] to [0024] of JP-A No. 2002-62426. Aldehydes having high reaction activity, particularly glutaraldehyde are preferred.

―Amount of crosslinking agent added―
0.1-20 mass% is preferable with respect to a polymer, and, as for the addition amount of the said crosslinking agent, 0.5-15 mass% is still more preferable. The amount of the unreacted crosslinking agent remaining in the alignment film is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. If the remaining amount of the crosslinking agent in the alignment film is not more than the upper limit, it is preferable because sufficient durability can be obtained. When such an alignment film is used in a liquid crystal display device, it is preferable that reticulation does not occur even when used for a long time or when left in a high temperature and high humidity atmosphere for a long time.

-Carboxylic acid compound-
The composition for forming an alignment film in the present invention preferably contains a specific carboxylic acid compound. Thereby, after aligning the formed alignment film by an aligning means, the coated surface shape of the optical compensation sheet obtained by coating the optically anisotropic layer is good, reducing optical defects such as white spots, Or the improvement effect which eliminates is expressed.
This is because the specific carboxylic acid compound contained in the alignment film has an effect on the alignment state of the liquid crystal molecules when the film surface hydrogen ion concentration of the alignment film is stabilized and the optically anisotropic layer is applied. It is presumed that one of the factors is to reduce the value of.
In addition, when the surface of the transparent support is hydrophilized by alkali saponification treatment, an alignment film having a good optical performance can be stably formed even if a slight amount of treatment liquid remains on the film surface. It is. At this time, since the effect varies depending on the amount added, it is necessary to adjust the amount appropriately. Specific examples of the specific carboxylic acid compound include those described in paragraph numbers [0162] to [0176] of JP-A-2005-115341.

  The alignment film is basically formed by applying a coating solution containing the polymer, a crosslinking agent, and a specific carboxylic acid, which is a composition for forming an alignment film, onto a transparent support, followed by drying by heating (crosslinking). It is a cured film that can be formed by orientation treatment. That is, the alignment film is preferably a cured film obtained by applying an alignment film forming composition containing polyvinyl alcohol and / or modified polyvinyl alcohol as a main component and drying. The cross-linking reaction may be performed at any time after coating on the transparent support.

  When a water-soluble polymer such as polyvinyl alcohol is used as the composition for forming an alignment film, the coating solution should be a mixed solvent of an organic solvent (for example, methanol, ethanol, isopropanol, etc.) having a defoaming action and water. preferable. The ratio of water: organic solvent (for example, methanol) is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9 in terms of mass ratio. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the layer surface of an orientation film and also an optically anisotropic layer reduces remarkably.

The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above.
For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment process of a liquid crystal display device can be applied. That is, a method is used in which the orientation is obtained by rubbing the surface of the orientation film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are flocked on average.

In the case of photo-alignment by light irradiation, the light source as the light irradiation device can be an ultra-high pressure mercury lamp, a xenon lamp, a fluorescent lamp, a laser, or the like. A light source and a polarizing film are combined (through the polarizing film) to convert the ultraviolet light into linearly polarized light and irradiate the photo alignment film.
As the polarizing film, stretched dyeing PVA (polyvinyl alcohol) is mainly used. Examples of this linearly polarized ultraviolet irradiation device include those disclosed in JP-A-10-90684.
The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm.

<Optically anisotropic layer>
The optically anisotropic layer is preferably designed so as to compensate for the liquid crystal compound in the liquid crystal cell in the black display of the liquid crystal display device. The alignment state of the liquid crystal compound in the liquid crystal cell in black display varies depending on the mode of the liquid crystal display device. The alignment state of the liquid crystal compound in the liquid crystal cell is described in IDW'00, FMC7-2, P411 to 414.

The optically anisotropic layer is formed from liquid crystalline molecules through the alignment film. The liquid crystalline molecules used in the optically anisotropic layer include rod-like liquid crystalline compounds and discotic liquid crystal compounds.
The rod-like liquid crystal molecules and discotic liquid crystal compounds may be high molecular liquid crystals or low molecular liquid crystals, and further include those in which the low molecular liquid crystals are not crosslinked to exhibit liquid crystallinity.
The optically anisotropic layer can be formed by applying a coating liquid containing liquid crystalline molecules, if necessary, a polymerizable initiator and other components on the alignment film.

[Bar-shaped liquid crystal compound]
Examples of the rod-like liquid crystal compound that can be used in the present invention include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, Alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.
The rod-like liquid crystal compound includes a metal complex. Moreover, the liquid crystal polymer which contains a rod-shaped liquid crystal compound in a repeating unit is mentioned. In other words, the rod-like liquid crystal compound may be bonded to a (liquid crystal) polymer.
For rod-shaped liquid crystal compounds, Chapters 4, 7, and 11 of the Quarterly Review of Chemical Review Vol. 22, “Chemicals of Liquid Crystal (1994), Chemical Society of Japan”, and the 142nd Committee of the Japan Society for the Promotion of Science It is described in Chapter 3 of the volume.

The birefringence of the rod-like liquid crystal compound used in the present invention is preferably in the range of 0.001 to 0.7.
The rod-like liquid crystal compound preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group.

[Discotic liquid crystal compound]
Examples of the discotic liquid crystal compound include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

The discotic liquid crystal compound exhibits liquid crystallinity with a structure in which a linear alkyl group, an alkoxy group, or a substituted benzoyloxy group is radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. Also included are compounds. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation.
When an optically anisotropic layer is formed from the discotic liquid crystal compound, the compound finally contained in the optically anisotropic layer no longer needs to exhibit liquid crystallinity.
For example, a low-molecular discotic liquid crystal compound has a group that reacts with heat or light, and the group reacts with heat or light to polymerize or crosslink to increase the molecular weight. When a layer is formed, the compound contained in the optically anisotropic layer may no longer have liquid crystallinity.
Preferred examples of the discotic liquid crystal compound are described in JP-A-8-50206. The polymerization of discotic liquid crystal compounds is described in JP-A-8-27284.

In order to fix the discotic liquid crystal compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystal compound. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group.
Accordingly, the discotic liquid crystal compound having a polymerizable group is preferably a compound represented by the following general formula (I).

In the above general formula (I), D is a discotic core, L is a divalent linking group, Q is a polymerizable group, and n is an integer of 4 to 12.

  As examples of the disk-shaped core (D), (D1) to (D15) are shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).

In the general formula (I), the divalent linking group (L) is composed of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. A divalent linking group selected from the group is preferred.
The divalent linking group (L) is a divalent group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, —CO—, —NH—, —O—, and —S— are combined. More preferably, it is a linking group.
The divalent linking group (L) is particularly preferably a divalent linking group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO- and -O- are combined. .
The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The arylene group preferably has 6 to 10 carbon atoms.

  As examples of the divalent linking group (L), (L1 to L24) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (Q). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group).

L1: -AL-CO-O-AL-
L2: -AL-CO-O-AL-O-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L6: -CO-AR-O-AL-O-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-O-CO-

L11: -O-AL-
L12: -O-AL-O-
L13: -O-AL-O-CO-
L14: -O-AL-O-CO-NH-AL-
L15: -O-AL-S-AL-
L16: -O-CO-AL-AR-O-AL-O-CO-
L17: -O-CO-AR-O-AL-CO-
L18: -O-CO-AR-O-AL-O-CO-
L19: -O-CO-AR-O-AL-O-AL-O-CO-
L20: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
L21: -S-AL-
L22: -S-AL-O-
L23: -S-AL-O-CO-
L24: -S-AL-S-AL-
L25: -S-AR-AL-

  The polymerizable group (Q) of the general formula (I) is determined according to the kind of the polymerization reaction. Examples of the polymerizable group (Q) are shown below.

  The polymerizable group (Q) of the general formula (I) is preferably an unsaturated polymerizable group (Q1, Q2, Q3, Q7, Q8, Q15, Q16, Q17) or an epoxy group (Q6, Q18). More preferably an unsaturated polymerizable group, and still more preferably an ethylenically unsaturated polymerizable group (Q1, Q7, Q8, Q15, Q16, Q17). A specific value of n is determined according to the type of the disk-shaped core (D). In addition, although the combination of several L and Q may differ, it is preferable that it is the same.

In the hybrid orientation, the angle between the major axis (disc surface) of the discotic compound and the surface of the support, that is, the tilt angle, increases in the depth direction of the optically anisotropic layer and increases with increasing distance from the surface of the polarizing film. Or it is decreasing. The angle preferably decreases with increasing distance.
Examples of changes in the inclination angle include continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, or intermittent change including increase and decrease. . The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if such a region where the angle does not change is included, it may be increased or decreased as a whole. However, it is preferable that the inclination angle changes continuously.

The average direction of the major axis (disk surface) of the discotic compound (average of the major axis direction of each molecule) is generally determined by selecting the discotic compound or the material of the alignment film, or by selecting the rubbing treatment method. Can be adjusted.
The major axis (disk surface) direction of the discotic compound on the surface side (air side) can generally be adjusted by selecting the discotic compound or the type of additive used together with the discotic compound.
Examples of the additive used together with the discotic compound include a plasticizer, a surfactant, a polymerizable monomer, and a polymer.
The degree of change in the orientation direction of the major axis can be adjusted by selecting liquid crystal molecules and additives as described above.

The plasticizer, surfactant and polymerizable monomer used together with the discotic compound are preferably compatible with the discotic compound and can change the tilt angle of the discotic compound or do not inhibit the orientation. . Therefore, a polymerizable monomer is preferable among these additive components.
Examples of the polymerizable monomer include compounds having a vinyl group, a vinyloxy group, an acryloyl group, or a methacryloyl group.
The addition amount of these additive components is usually 1 to 50% by mass and preferably 5 to 30% by mass with respect to the discotic compound. In addition, when a monomer having 4 or more polymerizable reactive functional groups is mixed and used, the adhesion between the alignment film and the optically anisotropic layer can be improved.

The optically anisotropic layer may contain a polymer together with the discotic compound. Such a polymer preferably has a certain degree of compatibility with the discotic compound and can change the tilt angle of the discotic compound.
Examples of the polymer include cellulose esters. Preferable examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, cellulose acetate butyrate and the like.
The addition amount of the polymer is preferably 0.1 to 10% by mass, more preferably 0.1 to 8% by mass, more preferably 0.1 to 5% by mass with respect to the discotic compound so as not to inhibit the orientation of the discotic compound. Mass% is particularly preferred.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic compound is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

[Fixing the alignment state of liquid crystalline molecules]
The aligned liquid crystal molecules can be fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. This polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is preferred.
Examples of the photopolymerization initiator include α-carbonyl compounds described in US Pat. Nos. 2,367,661 and 2,367,670, acyloin ethers described in US Pat. No. 2,448,828, and US Pat. Α-hydrocarbon substituted aromatic acyloin compounds described in US Pat. Nos. 3,056,127, and polynuclear quinone compounds described in US Pat. Nos. 2,951,758, US Pat. No. 3,549,367 Combinations of triarylimidazole dimer and p-aminophenyl ketone, acridine compounds and phenazine compounds described in JP-A-60-105667, US Pat. No. 4,239,850, and US Pat. No. 4,221,970 Oxadiazole compound Such as things.

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution.
The light irradiation for the polymerization of the liquid crystalline molecules preferably uses ultraviolet rays. The irradiation energy is preferably in the range of 20~50J / cm ^2, more preferably in the range of 20~5,000mJ / cm ^2, and still more preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

The optically anisotropic layer is prepared by preparing a coating solution containing at least one of the liquid crystalline compounds and, optionally, an additive such as a polymerizable initiator and a fluorine-based polymer, and applying the coating solution to the alignment film surface. It is formed by drying.
Examples of the fluorine compound include conventionally known compounds, and specific examples include the fluorine compounds described in paragraph numbers [0028] to [0056] of JP-A No. 2001-330725.

As the solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of the organic solvent include amide (eg, N, N-dimethylformamide), sulfoxide (eg, dimethyl sulfoxide), heterocyclic compound (eg, pyridine), hydrocarbon (eg, benzene, hexane), alkyl halide ( For example, chloroform (dichloromethane, tetrachloroethane), ester (for example, methyl acetate, butyl acetate), ketone (for example, acetone, methyl ethyl ketone), ether (for example, tetrahydrofuran, 1,2-dimethoxyethane) can be mentioned. Among these, alkyl halides and ketones are preferable. Also, what are these organic solvents? You may use individually by 1 type and may use 2 or more types together.
When producing an optical compensation film having very high uniformity as in the present invention, the surface tension is preferably 25 mN / m or less, and more preferably 22 mN / m or less.
The coating solution can be applied by a known method, and examples thereof include a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method.
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and still more preferably 1 to 10 μm. The optically anisotropic layer may be provided with a protective layer thereon.

(Method for producing optical compensation film)
Next, a method for continuously producing a preferable optical compensation film of the present invention will be described.
In the method for producing an optical compensation film of the present invention, for example, the following steps (1) to (4) are continuously performed.

(1) Support production process While stirring the cellulose ester acetate solution composition, each component is dissolved to prepare a cellulose acetate solution, while cellulose acetate (linter), letter is prepared in another tank or the like. A retardation increasing agent solution is prepared by stirring while heating the retardation increasing agent.
The dope is prepared by mixing the retardation increasing agent solution with the cellulose acetate solution and stirring sufficiently. This dope is cast using a band casting machine to produce a support.

(2) Alignment film preparation step On the support obtained in the support preparation step, an alignment film coating solution containing a compound that can react with the radical polymerizable group and has two or more vinyl groups is applied. And drying to produce an alignment film. The alignment film is rubbed in a predetermined axial direction of the support.

(3) Optically anisotropic layer preparation step The fluoroaliphatic group-containing copolymer is further added to a solution in which a discotic liquid crystalline compound, a photopolymerization initiator and the like are dissolved, and a coating solution for forming an optically anisotropic layer To prepare.
This coating solution is continuously applied onto the alignment film, and heated to align the discotic liquid crystalline compound, and irradiate it to polymerize the discotic liquid crystalline compound, allow to cool to room temperature, An optical compensation film with an anisotropic layer is prepared.

(Polarizer)
The polarizing plate of the present invention includes at least the optical compensation film of the present invention and a polarizing film.
As described above, the optical compensation film of the present invention exhibits its function remarkably by being bonded to a polarizing film to produce a polarizing plate.

<Polarizer>
Examples of the polarizer (hereinafter also referred to as “polarizing film”) include a coating type polarizing film typified by those manufactured by Optiva, a polarizing film comprising a binder and iodine or a dichroic dye. Etc. are preferable.
The iodine and the dichroic dye in the polarizer exhibit a deflection performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-organization like liquid crystal.
Here, a general-purpose polarizer is produced by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing the iodine or dichroic dye to penetrate into the binder. It is common.
In the general-purpose polarizer, iodine or a dichroic dye is distributed about 4 μm (about 8 μm on both sides) from the polymer surface. For this reason, in order to obtain sufficient polarization performance, the thickness of the binder is preferably 10 μm or more. On the other hand, the upper limit of the thickness is not particularly limited, but it is preferably as thin as possible from the viewpoint of the light leakage phenomenon that occurs when the polarizing plate is used in a liquid crystal display device. For this reason, it is preferable that it is 30 micrometers or less, 25 micrometers or less are more preferable, and 20 micrometers or less are especially preferable. When the thickness is 20 μm or less, the light leakage phenomenon is not observed on a 17-inch liquid crystal display device. The penetrability can be controlled by the solution concentration, bath temperature, and immersion time of iodine or dichroic dye.

The binder of the polarizing film may be cross-linked. Crosslinked binders include polymers that are themselves crosslinkable. Specifically, a polarizing film can be formed by reacting a polymer having a functional group or a binder obtained by introducing a functional group into the polymer between the binders by light, heat, or pH change.
Further, a crosslinked structure may be introduced into the polymer by a crosslinking agent. The cross-linked structure can be formed by using a cross-linking agent that is a highly reactive compound, introducing a bonding group derived from the cross-linking agent between the binders, and cross-linking the binders.
In general, the crosslinking is performed by applying a coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. The crosslinking treatment may be performed at any stage until the final polarizing plate is obtained as long as the durability can be ensured at the stage of the final product.

As the binder of the polarizing film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Examples of the polymer include polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, polystyrene, gelatin, polyvinyl alcohol, modified polyvinyl alcohol, poly (N-methylolacrylamide), polyvinyltoluene, chlorosulfonated polyethylene, nitrocellulose, and chlorine. Polyolefins (for example, polyvinyl chloride), polyester, polyimide, polyvinyl acetate, polyethylene, carboxymethylcellulose, polypropylene, polycarbonate, and copolymers thereof. Examples of the copolymer include acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, styrene / vinyl toluene copolymer, vinyl acetate / vinyl chloride copolymer, and ethylene / vinyl acetate copolymer. Can be mentioned.
Among these, as the polymer, for example, water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol are preferable, and gelatin, polyvinyl alcohol, and modified polyvinyl alcohol are more preferable. Polyvinyl alcohol and modified polyvinyl alcohol are particularly preferred.

The saponification degree of the polyvinyl alcohol and modified polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%, and particularly preferably 95 to 100%. The degree of polymerization of the polyvinyl alcohol is preferably 100 to 5,000.
The modified polyvinyl alcohol is obtained by introducing a modifying group into polyvinyl alcohol by copolymerization modification, chain transfer modification or block polymerization modification. In the copolymerization modification, COONa, Si (OH) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ COO, SO ₃ Na, C ₁₂ H ₂₅ can be introduced as modifying groups. In the chain transfer modification, COONa, SH, or SC ₁₂ H ₂₅ can be introduced as a modifying group.
The degree of polymerization of the modified polyvinyl alcohol is preferably 100 to 3,000. Examples of the modified polyvinyl alcohol are described in JP-A-8-338913, JP-A-9-152509, JP-A-9-316127, and the like.
Among these, the polyvinyl alcohol and the modified polyvinyl alcohol are particularly preferably unmodified polyvinyl alcohol having a saponification degree of 85 to 95% and alkylthio-modified polyvinyl alcohol. In addition, the said polyvinyl alcohol and modified polyvinyl alcohol may be used individually by 1 type, and may use 2 or more types together.

When a large amount of the crosslinking agent for the binder is added, the wet heat resistance of the polarizing film can be improved. However, when 50 mass% or more of a crosslinking agent is added to the binder, the orientation of iodine or the dichroic dye is lowered. For this reason, 0.1-20 mass% is preferable with respect to a binder, and, as for the addition amount of the said crosslinking agent, 0.5-15 mass% is more preferable.
The binder may contain some crosslinking agent that has not reacted even after the crosslinking reaction has been completed. However, the amount of the remaining crosslinking agent is preferably 1.0% by mass or less and more preferably 0.5% by mass or less in the binder. When the crosslinking agent is contained in the binder in an amount exceeding 1.0% by mass, there may be a problem in durability. That is, when a polarizing film having a large amount of residual crosslinking agent is incorporated in a liquid crystal display device and used for a long time or left in a high-temperature and high-humidity atmosphere for a long time, the degree of polarization may decrease.
Examples of the crosslinking agent are described in US Reissue Patent 23297. For example, boron compounds such as boric acid and borax can also be used as a crosslinking agent.

Examples of the dichroic dye include azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, anthraquinone dyes, and the like. The dichroic dye is preferably water-soluble. Further, it preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl).
Examples of the dichroic dye include C.I. I. Direct Yellow 12, C.I. I. Direct Orange 39, C.I. I. Direct Orange 72, C.I. I. Direct Red 39, C.I. I. Direct Red 79, C.I. I. Direct Red 81, C.I. I. Direct Red 83, C.I. I. Direct Red 89, C.I. I. Direct Violet 48, C.I. I. Direct Blue 67, C.I. I. Direct Blue 90, C.I. I. Direct Green 59, C.I. I. Acid Red 37 and the like.
Examples of the dichroic dye include, for example, JP-A-1-161202, 1-172906, 1-172907, 1-183602, 1-248105, 1-265205, 7-261024, and the like.
The dichroic dye is used as a free acid, an alkali metal salt, an ammonium salt, or an amine salt. Moreover, the polarizing film which has various hues can be manufactured by mix | blending two or more types of dichroic dyes.
Among these, as the dichroic dye, a polarizing film using a compound (pigment) that exhibits black when the polarization axes are orthogonal to each other, a polarizing film containing various dichroic molecules so as to exhibit black, or polarized light A plate is preferable because both the single plate transmittance and the polarization rate are excellent.

Here, in order to increase the contrast ratio of the liquid crystal display device, the transmittance of the polarizing plate is preferably higher and the degree of polarization is preferably higher. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and particularly in the range of 40 to 50% in light having a wavelength of 550 nm. preferable. The maximum value of the single plate transmittance of the polarizing plate is 50%.
The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and particularly preferably in the range of 99 to 100% in light having a wavelength of 550 nm.

The polarizing film and the optically anisotropic layer can also be disposed via an adhesive. Examples of the adhesive include polyvinyl alcohol resins and boron compound aqueous solutions. Among these, polyvinyl alcohol resins are preferable. In addition, as said polyvinyl alcohol-type resin, the modified polyvinyl alcohol by an acetoacetyl group, a sulfonic acid group, a carboxyl group, or an oxyalkylene group is included.
The thickness of the adhesive layer is preferably in the range of 0.01 to 10 μm after drying, and more preferably in the range of 0.05 to 5 μm.

[Production method of polarizer]
From the viewpoint of yield, the polarizing film is stretched at an angle of 10 to 80 ° with respect to the longitudinal direction (MD direction) of the polarizing film (stretching method), or after rubbing (rubbing method), iodine, It is preferable to dye with a dichroic dye. The inclination angle is preferably stretched so as to match the transmission axis of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the liquid crystal display (LCD) and the angle formed by the vertical or horizontal direction of the liquid crystal cell. .
The tilt angle is usually 45 °, but in recent years, transmissive LCDs, reflective LCDs, and transflective LCDs have not been developed with a device that is not necessarily 45 °, and the stretching direction is arbitrary according to the design of the LCD. It is preferable that it can be adjusted.

In the case of the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, more preferably 3.0 to 10.0 times. Stretching may be performed by dry stretching in air, or wet stretching in a state of being immersed in water. The stretch ratio of the dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of the wet stretching is preferably 3.0 to 10.0 times.
The stretching step may be performed in several steps including oblique stretching. By dividing into several times, it is possible to stretch more uniformly even at high magnification. Further, before the oblique stretching, the stretching may be performed horizontally or vertically to prevent shrinkage in the width direction.
Stretching can be performed by performing tenter stretching in biaxial stretching in different steps. The biaxial stretching is the same as the stretching method performed in normal film formation. Since the biaxial stretching is performed at different speeds on the left and right, the thickness of the binder film before stretching needs to be different on the left and right. In casting film formation, the flow rate of the binder solution can be differentiated between the left and right sides by tapering the die.
In the stretching method, a binder film that is obliquely stretched by 10 to 80 ° with respect to the MD direction of the polarizing film is produced as described above.

In the rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, the orientation is obtained by rubbing the surface of the film in a certain direction using, for example, paper, gauze, felt, rubber, nylon, polyester fiber or the like. Generally, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are planted on average.
The rubbing is preferably performed using a rubbing roll whose roundness, cylindricity, and runout (eccentricity) are all 30 μm or less. The film wrap angle on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can also be obtained by winding 360 ° or more.
When rubbing a long film, it is preferable to transport the film at a speed of 1 to 100 m / min with a constant tension by a transport device. At this time, the rubbing roll is preferably rotatable in a horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle, and specifically, an appropriate rubbing angle within a range of 0 to 60 °. It is preferable to select. The rubbing angle is preferably 40 to 50 ° and particularly preferably 45 ° when used in a liquid crystal display device.
It is preferable that a polymer film is disposed on the surface of the polarizing film on the side opposite to the optically anisotropic layer so that the optically anisotropic layer / polarizing film / polymer film is disposed.

[Surface treatment of optical compensation film]
When an optical compensation film is used instead of the transparent protective film of the polarizing plate, adhesion between the optical compensation film and the transparent protective film of the polarizing plate becomes a problem. In the present invention, adhesion between the optical compensation film and the polarizing film can be improved by surface-treating the surface of the optical compensation film on the polarizing film side.
As the surface treatment, corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, ozone treatment, acid treatment or alkali treatment is performed.
The processing methods such as corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, ozone treatment, acid treatment, and alkali treatment are described in, for example, pages 30 to 31 of published technical bulletin number 2001-1745. Can be mentioned. In the present invention, it is preferable to perform an alkali treatment, and examples thereof include the same contents as described in the saponification treatment of the above-described film.

(Liquid crystal display device)
The liquid crystal display device of the present invention has the polarizing plate of the present invention. A preferable form in each liquid crystal mode will be described below.

[TN mode liquid crystal display]
TN (Twisted Nematic) mode liquid crystal cells are most frequently used as color thin film transistor array (TFT) liquid crystal display devices, and are described in many documents.
The alignment state in the liquid crystal cell in the black display of the TN mode is an alignment state in which the rod-like liquid crystalline molecules rise at the center of the cell and the rod-like liquid crystalline molecules lie in the vicinity of the cell substrate.

The rod-like liquid crystalline molecules in the center of the cell can be compensated with a homeotropic alignment discotic compound that is a horizontal alignment in which the disk surface lies, or a (transparent) support, and in the vicinity of the substrate of the cell This rod-like liquid crystalline molecule can be compensated by a hybrid alignment discotic compound in which the inclination of the major axis changes with the distance from the polarizing film.
Further, for the rod-like liquid crystalline molecules in the center of the cell, it can be compensated with a homogeneously oriented rod-like liquid crystalline molecule whose horizontal axis is lying, or a (transparent) support. The rod-like liquid crystalline molecules in the vicinity of the substrate can be compensated with a discotic compound having a hybrid orientation.

The homeotropic alignment liquid crystal molecules are aligned in a state where the angle between the average alignment direction of the major axis of the liquid crystal molecules and the plane of the polarizing film is 85 to 95 °.
The homogeneously aligned liquid crystal molecules are aligned in a state where the angle between the average alignment direction of the major axes of the liquid crystal molecules and the plane of the polarizing film is less than 5 °.
In the hybrid alignment liquid crystal molecules, the angle between the average alignment direction of the long axes of the liquid crystal molecules and the plane of the polarizing film is preferably larger than 15 °, and more preferably 15 to 85 °.

An optically anisotropic layer in which the (transparent) support or discotic compound is homeotropically oriented, an optically anisotropic layer in which the rod-like liquid crystalline molecules are homogeneously oriented, and the homeotropically oriented discotic compound; The optically anisotropic layer composed of a mixture with homogeneously oriented rod-like liquid crystal molecules preferably has a thickness direction retardation value (Rth) of 40 nm to 200 nm and an in-plane retardation value (Re) of 0 to 70 nm. . Here, Rth is a value defined by the following formula (A), and Re is a value defined by the following formula (B).
Rth = {(nx + ny) / 2−nz} × d (Equation (A))
Re = (nx−ny) × d... Formula (B)
In the above formulas (A) and (B), nx represents the refractive index in the slow axis direction in the film plane, ny represents the refractive index in the fast axis direction in the film plane, and nz represents the thickness of the film. Represents the refractive index in the direction. d represents the thickness of the film.
The discotic compound layer having homeotropic alignment (horizontal alignment) and the rod-like liquid crystalline molecular layer having homogeneous alignment (horizontal alignment) are described in JP-A Nos. 12-304931 and 12-304932. Has been. The hybrid liquid crystal discotic liquid crystalline molecular layer is described in JP-A-8-50206.

[OCB mode liquid crystal display]
An OCB (Optically Compensatory Bend) mode liquid crystal cell is a bend alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned symmetrically in substantially opposite directions at the upper and lower portions of the liquid crystal cell. The liquid crystal display device using the bend alignment mode liquid crystal cell is described in, for example, US Pat. Nos. 4,583,825 and 5,410,422.
The bend alignment mode liquid crystal cell has a self-optical compensation function because rod-like liquid crystalline molecules are symmetrically aligned between the upper and lower portions of the liquid crystal cell. Therefore, this liquid crystal mode is called an OCB liquid crystal mode.
In the OCB mode liquid crystal cell as well as the TN mode, in the black display, the alignment state in the liquid crystal cell is an alignment state in which the rod-like liquid crystalline molecules rise at the center of the cell and the rod-like liquid crystalline molecules lie in the vicinity of the cell substrate. It is in.

Thus, in black display, since the alignment of the TN mode and the liquid crystal is in the same state, the preferred mode is also the same as in the TN mode. However, since the OCB mode has a larger range in which the liquid crystal compound rises in the center of the cell than the TN mode, the optically anisotropic layer in which the discotic compound is homeotropically aligned, or the rod-like liquid crystal molecule It is necessary to slightly adjust the retardation value of the optically anisotropic layer that is homogeneously oriented.
Specifically, an optically anisotropic layer in which a discotic compound on a (transparent) support is homeotropically aligned, or an optically anisotropic layer in which rod-like liquid crystalline molecules are homogeneously aligned has an Rth of 150. It is preferable that it is -500nm and Re is 20-70nm.

[VA mode liquid crystal display]
In a VA (Vertically Aligned) mode liquid crystal cell, rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied. In the VA mode liquid crystal cell, for example, (1) rod-like liquid crystal molecules described in JP-A-2-176625 are aligned substantially vertically when no voltage is applied, and substantially when a voltage is applied. VA mode liquid crystal cell in a narrow sense oriented horizontally, (2) SID97, Digest of tech. Papers (Preliminary Proceedings) 28 (1997) 845, MVA mode liquid crystal cell in which the VA mode is multi-domained for widening the viewing angle. (3) Proc. 58-59 (1998) And (4) LCD International 98 in a mode in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied, and (4) LCD International 98 Examples include the SURVAVAL mode liquid crystal cells that have been announced.

In the black display of the VA mode liquid crystal display device, since most of the rod-like liquid crystalline molecules in the liquid crystal cell are in an upright state, the optically anisotropic layer in which the discotic compound is homeotropically aligned, or In addition, the liquid crystal compound is compensated by the optically anisotropic layer in which the rod-like liquid crystalline molecules are homogeneously oriented. Separately, the rod-like liquid crystalline molecules are homogeneously oriented, and the average orientation direction of the major axis of the rod-like liquid crystalline molecules and the transmission of the polarizing film It is preferable to compensate the viewing angle dependency of the polarizing plate with an optically anisotropic layer having an angle with the axial direction of less than 5 °.
The optically anisotropic layer having homeotropic alignment or the optically anisotropic layer having rod-like liquid crystalline molecules homogeneously aligned preferably has Rth of 150 to 500 nm and Re of 20 to 70 nm.

[Other liquid crystal display devices]
In addition, liquid crystal display devices in ECB (Electrically Controlled Bend) mode and STN (Super Twisted Nematic) mode can be optically compensated in the same way as described above.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Example 1)
(Preparation of optical compensation film (KH-1))
<Preparation of support (PK-1)>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

[Cellulose acetate solution composition]
・ Acetylation degree 60.9% cellulose acetate (Linter) ・ ・ ・ ・ ・ ・ 80.0 parts by mass ・ Acetylation degree 60.8% cellulose acetate (Linter) ・ ・ ・ ・ ・ ・ 20.0 Parts by mass, triphenyl phosphate (plasticizer) ... 7.8 parts by mass, biphenyl diphenyl phosphate (plasticizer) ... -3.9 parts by mass-Methylene chloride (first solvent) ... 300.0 parts by mass-Methanol (second solvent) ... ... 54.0 parts by mass
-1-butanol (third solvent) ... 11.0 parts by mass

In another mixing tank, 4 parts by mass of cellulose acetate (linter) having an acetylation degree of 60.9%, 16 parts by mass of a retardation increasing agent represented by the following general formula (II), silica fine particles (particle size 20 nm, Mohs hardness about 7) ) 0.5 parts by mass, 87 parts by mass of methylene chloride, and 13 parts by mass of methanol were added and stirred while heating to prepare a retardation increasing agent solution.
Next, 36 parts by mass of the retardation increasing agent solution was mixed with 464 parts by mass of the cellulose acetate solution, and the dope was prepared by sufficiently stirring. In addition, the addition amount of the retardation increasing agent was 5.0 mass parts with respect to 100 mass parts of cellulose acetate.

The obtained dope was cast using a band casting machine. The dope was dried for 1 minute after the film surface temperature on the band reached 40 ° C., peeled off the film having a residual solvent amount of 43% by mass, and then dried using a tenter with a drying air of 140 ° C. Stretched 28% in the direction.
Then, it dried for 20 minutes with 135 degreeC dry air, and produced the support body (PK-1) whose residual solvent amount is 0.3 mass%.
The obtained support (PK-1) had a width of 1,340 mm and a thickness of 92 μm. Using an ellipsometer (M-150, manufactured by JASCO Corporation), the in-plane retardation value (Re) at a wavelength of 590 nm was measured and found to be 43 nm. The retardation value (Rth) in the thickness direction at a wavelength of 590 nm was measured and found to be 175 nm.
The support (PK-1) thus produced was immersed in a 2.0N potassium hydroxide solution (25 ° C.) for 2 minutes, neutralized with sulfuric acid, washed with pure water and dried. It was 63 mN / m when the surface energy of this support body (PK-1) was calculated | required by the contact angle method.

<< Preparation of alignment film layer >>
An alignment film layer-forming composition having the following composition was prepared so that the liquid specific gravity was 0.968, and 31.5 mL with a # 18 wire bar coater on the alkali-treated surface of the support (PK-1). / M ^{2 was} applied.
Thereafter, the film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film layer.

[Composition for alignment layer formation]
・ Modified polyvinyl alcohol as shown below ... 100,000 parts by mass, water ... ··· 2,360.00 parts by mass · Methanol ·················· 75.00 parts by mass · Ethylene glycol diglycidyl ether ( Cross-linking agent)
EX810 (manufactured by Nagase Chemtech) ... 5.40 parts by mass
-Carboxylic acid compound (additive) shown below ... 1.75 parts by mass

<Formation of optically anisotropic layer>
A composition for forming an optically anisotropic layer having the following composition was prepared so that the liquid specific gravity was 0.912, and rubbed on the alignment film with a # 3.2 wire bar coater at 5.4 mL / m ^{2 was} applied. Then, UV irradiation was performed for 4 seconds using a 160 W / cm high-pressure mercury lamp in an atmosphere of 90 ° C. for 90 seconds, and in an atmosphere of 90 ° C., thereby polymerizing the discotic compound. Then, it cooled to room temperature, the optically anisotropic layer was formed, and the optical compensation film (KH-1) was produced.

[Composition for forming optically anisotropic layer]
· Discotic liquid crystalline compound represented by the following general formula (III) ··· 41.01 parts by mass · Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) ··· ······ 4.06 parts by mass · Cellulose acetate butyrate (CAB551-0.2, manufactured by Eastman Chemical Co., Ltd.) ······ 0.34 parts by mass · Cellulose acetate butyrate ( CAB531-1 manufactured by Eastman Chemical Co., Ltd.) ... 0.11 parts by mass-Fluoroaliphatic group-containing polymer 1 represented by the following general formula (IV): 0.56 parts by mass・ Fluoroaliphatic group-containing polymer 2 represented by the following general formula (V): 0.06 parts by mass ・ Photopolymerization initiator (Irgacure 907, manufactured by Ciba-Geigy Corporation) 1.35 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co.) ........ 0.45 parts by weight
・ Methyl ethyl ketone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 97.00 parts by mass

(Preparation of polarizing plate HB-1)
<Production of polarizer>
Polyvinyl alcohol (PVA) having an average polymerization degree of 4,000 and a saponification degree of 99.8 mol% was dissolved in water to obtain a 4.0% aqueous solution. This solution was band-cast using a taper die and dried to prepare a film having a width of 110 mm before stretching, a thickness of 120 μm at the left end, and 135 μm at the right end.
The film is peeled off from the band, obliquely stretched in a 45 ° direction in a dry state, and immersed in an aqueous solution of 0.5 g / L iodine and 50 g / L potassium iodide for 1 minute at 30 ° C., and then 100 g boric acid. / L, immersed in an aqueous solution of 60 g / L of potassium iodide at 70 ° C. for 5 minutes, further washed with water at 20 ° C. for 10 seconds and then dried at 80 ° C. for 5 minutes to obtain a polarizer (HF-01) Got. The obtained polarizer (HF-01) had a width of 660 mm and a thickness of 20 μm on both the left and right sides.

<Attaching optical compensation film>
The optical compensation film (KH-1) was attached to one surface of the polarizer (HF-01) with the support (PK-1) surface using a polyvinyl alcohol-based adhesive.
Further, a saponification treatment is performed on a 80 μm thick triacetyl cellulose film (TD-80U: manufactured by Fuji Film Co., Ltd.), and is attached to the other surface of the polarizer (HF-1) using a polyvinyl alcohol adhesive. I attached.
In addition, it arrange | positioned so that the longitudinal direction of polarizer (HF-01), the longitudinal direction of a support body (PK-1), and also the longitudinal direction of a commercially available triacetylcellulose film might all become parallel. In this way, a polarizing plate (HB-1) was produced.

(Production of liquid crystal display device)
Remove the pair of polarizing plates installed on both sides of the TN type liquid crystal cell used in the liquid crystal display device (AQUAS LC20C1S, manufactured by Sharp Corporation), and replace the polarizing plate (HB-1) with The optical compensation film (KH-1) was attached to the viewer side and the backlight side one by one through an adhesive so that the liquid crystal cell side would be on the liquid crystal cell side. At this time, the transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged so as to be orthogonal to each other.

(Evaluation of optical compensation film, polarizing plate, and liquid crystal display device)
-Evaluation of durability crack-
A sample in which the polarizing plate (HB-1) produced in Example 1 was attached to glass was used as a sample. After being allowed to stand for 24 hours under conditions of a temperature of 60 ° C. and a relative humidity of 90%, the sample was returned to room temperature. The crack (durability crack) of the sample was observed visually and with a stereomicroscope. The degree of durability cracking was determined according to the following criteria.

(Double-circle): The crack did not generate | occur | produce at all.
○: A minute crack that cannot be visually observed is generated, but this is not a problem as a product.
X: A crack that can be observed visually is generated and cannot be used as a product.

-Evaluation of orientation-
The optical compensation film (KH-1) produced in Example 1 was observed with a polarizing microscope to observe the alignment state. The evaluation of orientation was judged according to the following criteria.

(Double-circle): Shrilane does not generate | occur | produce at all and it distributes light uniformly.
○: Slightly minute shrelane is generated, but this is not a problem as a product.
X: Shrilane occurs and cannot be used as a product.

-Evaluation of unevenness on the panel-
The liquid crystal display device using the polarizing plate (HB-1) produced in Example 1 was adjusted to a halftone on the entire surface, and unevenness was visually evaluated from a direction inclined 60 ° from the front and normal. The evaluation results are shown in Table 1. In the liquid crystal display device of this example, no unevenness was observed from any direction.

A: No unevenness occurred at all.
○: Slight unevenness that is not noticeable is generated, but this is not a problem as a product.
X: Conspicuous unevenness occurs and cannot be used as a product.

(Example 2)
As shown in Table 1, Example 1 except that the crosslinking agent in the alignment film layer forming composition of Example 1 was changed from ethylene glycol diglycidyl ether to tripropylene glycol diglycidyl ether (EX920 manufactured by Nagase Chemtech). In the same manner as above, an optical compensation film and a polarizing plate were prepared, and durability cracks, orientation, and unevenness were evaluated. The evaluation results are shown in Table 1.

(Examples 3 to 5)
As shown in Table 1, in the same manner as in Example 2 except that the addition amount of the crosslinking agent (tripropylene glycol diglycidyl ether) in the composition for forming an alignment layer in Example 2 was changed, an optical compensation film, and A polarizing plate was prepared, and durability cracks, orientation, and unevenness were evaluated. The evaluation results are shown in Table 1.

(Example 6)
As shown in Table 1, the same procedure as in Example 1 was performed except that the cross-linking agent in the composition for forming an alignment film layer of Example 1 was changed from ethylene glycol diglycidyl ether to sorbitol polyglycidyl ether (EX614B manufactured by Nagase Chemtech). Then, an optical compensation film and a polarizing plate were prepared, and durability cracks, orientation, and unevenness were evaluated. The evaluation results are shown in Table 1.

(Example 7)
As shown in Table 1, the same procedure as in Example 1 was performed except that the cross-linking agent in the composition for forming an alignment film layer in Example 1 was changed from ethylene glycol diglycidyl ether to glycerol polyglycidyl ether (EX521 manufactured by Nagase Chemtech). Then, an optical compensation film and a polarizing plate were prepared, and durability cracks, orientation, and unevenness were evaluated. The evaluation results are shown in Table 1.

(Example 8)
As shown in Table 1, Example 1 except that the crosslinking agent in the composition for forming an alignment film layer of Example 1 was changed from ethylene glycol diglycidyl ether to 1,6-hexamethylene diisocyanate (manufactured by Wako Pure Chemical Industries). In the same manner as above, an optical compensation film and a polarizing plate were prepared, and durability cracks, orientation, and unevenness were evaluated. The evaluation results are shown in Table 1.

Example 9
As shown in Table 1, the crosslinking agent in the composition for forming an alignment layer of Example 1 was changed from ethylene glycol diglycidyl ether to tris [3- (1-aziridinyl) propionic acid] trimethylolpropane (manufactured by Wako Pure Chemical Industries). An optical compensation film and a polarizing plate were produced in the same manner as in Example 1 except that the change was changed to, and durability cracks, orientation, and unevenness were evaluated. The evaluation results are shown in Table 1.

(Comparative Example 1)
As shown in Table 1, an optical compensation film and a polarizing plate were prepared in the same manner as in Example 1 except that the crosslinking agent in the alignment film layer forming composition of Example 1 was not added. The property and unevenness were evaluated. The evaluation results are shown in Table 1.

(Comparative Example 2)
As shown in Table 1, the optical compensation film and the polarizing plate were prepared in the same manner as in Example 1 except that the crosslinking agent in the composition for forming an alignment film layer of Example 1 was changed from ethylene glycol diacrylate to glutaraldehyde. Fabricated and evaluated for durability cracks, orientation, and unevenness. The evaluation results are shown in Table 1.

(Comparative Example 3)
As shown in Table 1, an optical compensation film and a polarizing plate were produced in the same manner as in Example 1 except that the crosslinking agent in the composition for forming an alignment film layer in Example 1 was changed from ethylene glycol diacrylate to formaldehyde. Then, durability cracks, orientation, and unevenness were evaluated. The evaluation results are shown in Table 1.

(Comparative Examples 4-5)
As shown in Table 1, an optical compensation film and a polarizing plate were produced in the same manner as in Example 2 except that the addition amount of the crosslinking agent in the composition for forming an alignment film layer in Example 2 was changed. Cracks, orientation, and unevenness were evaluated. The evaluation results are shown in Table 1.

From the results in Table 1, the composition for forming an alignment film layer contains the epoxy compound, the isocyanate compound, and the aziridine compound at a ratio of 0.10 to 30.00% by mass with respect to the total solid content of the alignment layer film. In Examples 1 to 10, there was no problem in orientation, and good durability was observed. In particular, in Examples 1 to 4 in which the content of the epoxy compound was 1.0 to 10.0% by mass, results showing superior durability and orientation were shown.
On the other hand, the optical compensation films and polarizing plates of Comparative Examples 1 to 4 do not contain the epoxy compound, isocyanate compound, or aziridine compound, or less than 0.10% by mass, so the orientation is good. However, the durability was poor. Since Comparative Example 5 was included at a rate exceeding 30.00% by mass, the orientation was poor.

  Moreover, in the panel observation of the liquid crystal display device of Examples 1-10, it was recognized that favorable display quality is maintained without unevenness.

  The optical compensation film of the present invention has a high durability when a polarizing plate is prepared and placed under high temperature and high humidity, and can maintain good orientation, so that the polarizing plate and a liquid crystal display having the same It can use suitably for an apparatus.

Claims (4)

  An alignment film layer for aligning the liquid crystal compound and an optically anisotropic layer made of the liquid crystal compound are provided on the support, and the alignment film layer includes an epoxy compound, an isocyanate compound, and an aziridine compound. 0.10-30.0 mass% is contained with respect to the total solid of the said alignment film layer, The optical compensation film characterized by the above-mentioned.   A method for producing an optical compensation film, comprising producing the optical compensation film according to claim 1.   A polarizing plate comprising the optical compensation film according to claim 1.   A liquid crystal display device comprising the polarizing plate according to claim 3.