JP2007057607A - Method for manufacturing optical compensating film, optical compensating film, polarizer, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably and continuously manufacturing an optical compensating film which has a superior optical compensating function for an OCB type liquid crystal display device and also has small optical unevenness, and to provide the optical compensating film obtained by the method, a polarizer using the same, and a liquid crystal display device. <P>SOLUTION: Disclosed are the method for manufacturing the optical compensating film having a stage of forming a liquid crystal compound layer by coating a base with coating liquid containing a polymerizable liquid crystal compound, a stage of forming an optical anisotropic layer by aligning the liquid crystal compound after drying the liquid crystal compound layer and then fixing the alignment, and a stage of further heating the optical anisotropic layer at heating temperature of 40 to 150°C for a heating time of 5 to 3,000 seconds after fixing the alignment of the liquid crystal compound, the optical compensating film obtained by the method, the polarizing plate using the same and the liquid crystal display device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical compensation film having an optically anisotropic layer in which a polymerizable liquid crystal compound is aligned and fixed, a method for producing the same, a polarizing plate using the same, and a liquid crystal display device.

  An optical film having a layer in which a liquid crystal compound is highly oriented and fixed is being developed in various applications in recent years, such as an optical compensation film for a liquid crystal display device, a brightness enhancement film, and an optical compensation film for a projection display device. In particular, the development of the liquid crystal display device as an optical compensation film is remarkable. Usually, the liquid crystal display device includes a polarizing plate and a liquid crystal cell. In the TN type TFT liquid crystal display device which is currently mainstream, an optical compensation film is inserted between the polarizing plate and the liquid crystal cell to realize a liquid crystal display device with high display quality. However, in this configuration, the thickness of the liquid crystal display device itself is increased, and it is not possible to sufficiently meet the demand for thickness reduction.

On the other hand, by using an elliptically polarizing plate having a retardation film (optical compensation film) on one side of the polarizing film and a protective film on the other side, the front contrast can be increased without increasing the thickness of the liquid crystal display device. The invention which can be performed is proposed (for example, refer patent document 1). However, the retardation film having the above-described structure has a problem that a sufficient viewing angle improvement effect cannot be obtained and the display quality of the liquid crystal display device is deteriorated.
Currently, an optical compensation film in which an optically anisotropic layer formed from a discotic compound is coated on a transparent support is directly used as a protective film for a polarizing plate, thereby thickening a liquid crystal display device. Therefore, the problem concerning the viewing angle is solved (see, for example, Patent Documents 2 and 3).

In recent years, demand for liquid crystal televisions has been increasing, and liquid crystal televisions have been increased in size and brightness, and subtle optical unevenness has become a problem. In particular, in an OCB type liquid crystal display device excellent in the suitability for moving images, which is an important factor for a television, since the display principle is a birefringence method, optical unevenness is expected to be a very big problem. For example, in Patent Documents 4 and 5, by applying an optical compensation film having a layer made of a liquid crystal compound to an OCB type liquid crystal display device, it is possible to deal with moving images and solve problems such as viewing angle.
JP-A-2-247602 Japanese Patent Laid-Open No. 7-191217 European Patent No. 0911656A2 JP-A-9-212444 JP 11-316378 A

INDUSTRIAL APPLICABILITY The present invention has an excellent optical compensation function for liquid crystal display devices, particularly OCB type liquid crystal display devices with a fast response speed and suitability for moving images, and an optical compensation film with small optical unevenness can be stably and continuously produced. It is an object of the present invention to provide a method that can be manufactured in general, and to provide an optical compensation film having an excellent optical compensation function and small optical unevenness.
In addition, the present invention has a polarizing function and an excellent optical compensation function for a liquid crystal display device, particularly an OCB type liquid crystal display device with a fast response speed and suitable for moving images, and has small optical unevenness. It is an object to provide a polarizing plate that can contribute to thinning of a liquid crystal display device.
It is another object of the present invention to provide a liquid crystal display device capable of displaying an image with high display quality, particularly an OCB type liquid crystal display device having a high response speed and suitable for moving images.

The object is achieved by the following means.
[1] The process of apply | coating the coating liquid containing a polymeric liquid crystal compound on the surface of a support body or a support body, and forming a liquid crystal compound layer;
Simultaneously or after drying the liquid crystal compound layer, orienting the liquid crystal compound at a temperature equal to or higher than the liquid crystal transition temperature, and fixing the orientation to form an optically anisotropic layer; and Heating the optically anisotropic layer after fixing the orientation;
A method for producing an optical compensation film having
A method for producing an optical compensation film, wherein the heating temperature in the step of heating the optically anisotropic layer is 40 ° C. to 150 ° C., and the heating time is 5 seconds to 3000 seconds.
[2] An optical compensation film having a support and an optically anisotropic layer formed on the support using a polymerizable liquid crystal compound, which is manufactured by the manufacturing method according to [1]. An optical compensation film characterized by the above.
[3] The optical compensation film as described in [2], wherein the polymerizable liquid crystal compound is a discotic liquid crystal compound having a polymerizable group.
[4] A polarizing plate comprising the optical compensation film according to [2] or [3] and a polarizing film.
[5] A liquid crystal display device comprising the optical compensation film according to [2] or [3] or the polarizing plate according to [4].
[6] The liquid crystal display device according to [5], wherein the display method is an OCB method.

In the present invention, the following modes are also preferable.
[7] A roll-shaped optical compensation film in which the optical compensation film according to [2] or [3] is elongated and wound into a roll, and the polymerizable liquid crystal in the optical anisotropic layer A roll-shaped optical compensation film, wherein the average direction of the molecular symmetry axis of the compound is 43 ° to 47 ° with respect to the longitudinal direction.
[8] The roll-shaped optical compensation film as described in [7] above, which has an alignment film between the support and the optically anisotropic layer.

[9] The roll-shaped optical compensation film according to [8], wherein the alignment film is made of polyvinyl alcohol or modified polyvinyl alcohol crosslinked by a reaction with a crosslinking agent.
[10] The roll-shaped optical compensation film according to any one of [7] to [9], wherein the polymerizable liquid crystal compound is a discotic liquid crystal compound having a polymerizable group.

According to the present invention, an optical compensation film having an excellent optical compensation function with respect to a liquid crystal display device, particularly an OCB-type liquid crystal display device having a fast response speed and suitable for moving images, and having a small optical unevenness stably and It can be manufactured continuously, and the optical compensation film can be easily manufactured even in the form of a roll.
In addition, according to the present invention, it is possible to provide a polarizing plate having a polarization function and an excellent optical compensation function for a liquid crystal display device, particularly an OCB type liquid crystal display device, and having small optical unevenness. . With the polarizing plate of the present invention, the liquid crystal display device can be reduced in thickness and weight.
Furthermore, according to the present invention, it is possible to provide a liquid crystal display device capable of displaying an image with high display quality, particularly an OCB-type liquid crystal display device having a high response speed and suitable for moving images.

Hereinafter, the present invention will be described in detail.
[Optical compensation film]
The optical compensation film of the present invention is an optical compensation film having a support and an optically anisotropic layer formed from a polymerizable liquid crystal compound (hereinafter sometimes simply referred to as a liquid crystal compound) on the support. In order to align the liquid crystal compound of the optically anisotropic layer, it is preferable to form an alignment film on the support or the support and to rub the surface.
As a result of diligent research by the present inventors, it has been found that the cause of the optical unevenness is a minute thickness unevenness of the optically anisotropic layer and a local and subtle shift in the alignment direction of the liquid crystal compound. Further, although the mechanism is not clear, it has been found that the optical unevenness is remarkably reduced by reducing the thickness of the liquid crystal compound.
One method for reducing the thickness while maintaining the optical compensation capability of the optically anisotropic layer is to cure the liquid crystal compound at a low temperature as much as possible. Specifically, the methods described in JP-A-10-293210 and JP-A-2000-9936 can be applied. However, according to this method, since the alignment of the liquid crystal compound is fixed at a low temperature, the strength of the liquid crystal compound layer itself is lowered, and the adhesion force to the alignment film (or support) is reduced. .
As a result of diligent research by the present inventors, it has been found that the above problem can be solved by a very simple method of heating the film after fixing the polymerizable liquid crystal compound. It is presumed that the radical generated by the external field at the time of immobilization remains after the immobilization, and the polymerization proceeds by heating before the radical is deactivated.
The alignment direction of the liquid crystal compound refers to the average direction of the molecular symmetry axis of the liquid crystal compound in the optically anisotropic layer, and usually coincides with the average direction of orthogonal projection of the molecular symmetry axis of the liquid crystal compound onto the support surface.

  The optical compensation film of the present invention is preferably produced in a roll shape, and may be incorporated into a liquid crystal display device as an optical compensation film after being cut into a desired shape, or used as a protective film for a polarizing plate. It can also be incorporated into a liquid crystal display device after being integrated with other components of the device. It is preferably used for a horizontal alignment mode (particularly a reflection type liquid crystal display device) or a bend alignment mode liquid crystal display device. When the optical compensation film of the present invention is applied to a liquid crystal display device of these modes, the arrangement of the optically anisotropic layer, the support and the polarizing film is very important. A discotic compound is used as the liquid crystal compound. Details of the case are described in JP-A-11-316378, and can also be applied to the embodiment of the present invention.

Hereinafter, each component of the optical compensation film of the present invention will be described in detail.
<Support>
The support used in the present invention is preferably transparent, and specifically, the light transmittance is preferably 80% or more. A transparent polymer film is preferable in consideration of the necessity of being able to be wound into a cylindrical shape when producing a roll-shaped optical compensation film. Examples of the polymer film that can be used as a support include polymer films made of cellulose ester (eg, cellulose acetate, cellulose diacetate), norbornene-based polymer, polymethyl methacrylate, and the like. Commercially available polymers (for norbornene polymers, ARTON (manufactured by Nippon Synthetic Rubber Co., Ltd.) and ZEONEX (manufactured by Nippon Zeon Co., Ltd.) (both are trade names)) may be used. Among them, a film made of cellulose ester is preferable, and a film made of lower fatty acid ester of cellulose is more preferable. Lower fatty acid means a fatty acid having 6 or less carbon atoms. Particularly, the number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). A film made of cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate can also be used.

  In addition, even a conventionally known polymer such as polycarbonate or polysulfone, which easily develops birefringence, can exhibit birefringence by modifying the molecule as described in International Publication WO00 / 26705. Can be used as a support in the present invention.

When the optical compensation film of the present invention is used as a protective film for a polarizing plate or a retardation film, it is preferable to use cellulose acetate having an acetylation degree of 55.0 to 62.5% as the polymer film. . The acetylation degree is more preferably 57.0 to 62.0%. Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).
The viscosity average degree of polymerization (DP) of cellulose acetate is preferably 250 or more, and more preferably 290 or more. 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. The specific value of Mw / Mn is preferably 1.0 to 4.0, more preferably 1.0 to 1.65, and most preferably 1.0 to 1.6. preferable.

In 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. In the polymer film used as the support, it is preferable that the 6-position substitution degree of cellulose is the same as or higher than the 2-position and 3-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 is preferably 30 to 40%, more preferably 31 to 40%, and more preferably 32 to 40%. Most preferred. 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 described in 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. It can be synthesized with reference to the method of Synthesis Example 3.

  The Re retardation value and Rth retardation value of the support are defined by the following formulas (I) and (II), respectively.

  Formula (I) Re = (nx−ny) × d

  Formula (II) Rth = {(nx + ny) / 2−nz} × d

  In formulas (I) and (II), nx is the refractive index in the slow axis direction (the direction in which the refractive index is maximum) in the plane of the support, and ny is the fast axis direction (refractive index in the plane of the support). Is the refractive index in the thickness direction of the support, d is the thickness of the film with the unit of nm.

The Rth retardation value (measurement wavelength λ = 590 nm) of the support used in the present invention is preferably 40 nm to 400 nm, and the Re retardation value (measurement wavelength λ = 590 nm) is preferably 0 to 70 nm. .
When two optical compensation films of the present invention using a cellulose acetate film as a support are incorporated into a liquid crystal display device, the Rth retardation value of the cellulose acetate film is preferably 40 to 250 nm. On the other hand, when one optical compensation film of the present invention using a cellulose acetate film as a support is incorporated into a liquid crystal display device, the Rth retardation value of the cellulose acetate film is preferably 150 to 400 nm.
The birefringence (value obtained by dividing the Re retardation value by the thickness) of the cellulose acetate film is preferably 0.00025 to 0.00088. Moreover, it is preferable that the birefringence (Rth retardation value divided by thickness) of the cellulose acetate film in the thickness direction is 0.00088 to 0.005.

  When a cellulose acetate film is used for the support, it is preferable to include a retardation increasing agent in the film. Examples of preferred compounds and production methods thereof are disclosed in JP-A Nos. 2000-154261 and 2000-1111914. In the official gazette.

<< Optically anisotropic layer >>
The optical compensation film of the present invention has at least one optically anisotropic layer formed from a polymerizable liquid crystal compound. The optically anisotropic layer may be directly formed on the surface of the support, but it is more preferable to form an alignment film on the support and to form the alignment film on the alignment film.
Examples of the liquid crystal compound used for forming the optically anisotropic layer include a rod-like liquid crystal compound and a discotic liquid crystal compound. The rod-like liquid crystal compound and the discotic liquid crystal compound may be a polymer liquid crystal or a low-molecular liquid crystal, and further include those in which the low-molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity.

《Bar-shaped liquid crystal compound》
Examples of the rod-shaped 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. A liquid crystal polymer containing a rod-like liquid crystal compound in a repeating unit can also be used. In other words, the rod-like liquid crystal compound may be bonded to a (liquid crystal) polymer.
For rod-shaped liquid crystal compounds, see Chapter 4, Chapter 7 and Chapter 11 of the Chemistry of the Quarterly Chemistry Vol. Described in Chapter 3.

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 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 most preferably an ethylenically unsaturated polymerizable group.

《Discotic liquid crystal compound》
Examples of discotic liquid crystal compounds 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, page 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 has a linear alkyl group with respect to the mother nucleus at the center of the molecule,
Also included are compounds exhibiting liquid crystallinity having a structure in which an alkoxy group or a substituted benzoyloxy group is substituted radially as a side chain of the mother nucleus. 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 a 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, thereby increasing the molecular weight. In the case where 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 formula (III).

  Formula (III) D (-LQ) n

  In formula (III), 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.

  An example of the disk-shaped core (D) is 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 formula (III), the divalent linking group (L) is selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. A divalent linking group is preferred. The divalent linking group (L) is a divalent combination of at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO-, -NH-, -O-, and -S-. More preferably, it is a linking group. The divalent linking group (L) is most 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.

Examples of the divalent linking group (L) 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-AR-O-AL-CO-
L17: -O-CO-AR-O-AL-O-CO-
L18: -O-CO-AR-O-AL-O-AL-O-CO-
L19: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
L20: -S-AL-
L21: -S-AL-O-
L22: -S-AL-O-CO-
L23: -S-AL-S-AL-
L24: -S-AR-AL-

The polymerizable group (Q) of the formula (III) is determined according to the type of polymerization reaction. The polymerizable group (Q) is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group.
In formula (III), n is an integer of 4-12. A specific number 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.

Regarding the orientation of the liquid crystal compound in the optically anisotropic layer, the liquid crystal compound in the optically anisotropic layer is oriented so that the average direction of the molecular symmetry axis of the liquid crystal compound is 43 ° to 47 ° with respect to the longitudinal direction, for example.
In the hybrid alignment, the angle between the molecular symmetry axis of the liquid crystal compound and the surface of the support increases or decreases in the depth direction of the optically anisotropic layer and with increasing distance from the surface of the support. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction.
Even if the angle includes a region where the angle does not change, the angle only needs to increase or decrease as a whole. Furthermore, it is preferable that the angle changes continuously.

  The average direction of the molecular symmetry axis of the liquid crystal compound can be generally adjusted by selecting a liquid crystal compound or an alignment film material or by selecting a rubbing treatment method. Further, the molecular symmetry axis direction of the liquid crystal compound on the surface side (air side) can be generally adjusted by selecting the liquid crystal compound or the type of additive used together with the liquid crystal compound. Examples of the additive used together with the liquid crystal compound include a plasticizer, a surfactant, a polymerizable monomer and a polymer. Similar to the above, the degree of change in the orientation direction of the molecular symmetry axis can be adjusted by selecting the liquid crystal compound and the additive. In particular, regarding the surfactant, it is preferable that it is compatible with the control of the surface tension of the coating liquid described later.

The plasticizer, the surfactant and the polymerizable monomer used together with the liquid crystal compound are preferably compatible with the liquid crystal compound and can change the tilt angle of the liquid crystal compound or do not inhibit the alignment. A polymerizable monomer (eg, a compound having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) is preferred. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the liquid crystal 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.

When a discotic liquid crystal compound is used as the liquid crystal compound, it is preferable to use a polymer that has a certain degree of compatibility with the discotic liquid crystal compound and can change the tilt angle of the discotic liquid crystal compound.
A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose and cellulose acetate butyrate. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, and in the range of 0.1 to 8% by mass with respect to the discotic liquid crystal compound so as not to inhibit the orientation of the discotic liquid crystal compound. It is more preferable that it is in the range of 0.1 to 5% by mass.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystal compound is preferably 70 to 300 ° C, and more preferably 70 to 170 ° C.
The temperature at the time of fixing the orientation is preferably carried out at or below the discotic nematic liquid crystal phase-solid phase transition temperature.
The post-heating after the orientation fixing will be described below.

  In the present invention, the thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm.

《Alignment film》
The optical compensation film of the present invention preferably has an alignment film between the support and the optically anisotropic layer.
In the present invention, the alignment film is preferably a layer made of a crosslinked polymer. As the polymer used for the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. The alignment film is formed by reacting a polymer having a functional group or a polymer having a functional group introduced therein with light, heat, pH change, or the like; or a cross-linking agent that is a compound having high reaction activity Can be formed by introducing a linking group derived from a cross-linking agent between polymers to cross-link between the polymers.

The alignment film composed of a crosslinked polymer can be usually formed by applying a coating solution containing the polymer or a mixture of a polymer and a crosslinking agent on a support, followed by heating or the like.
In the rubbing process described later, it is preferable to increase the degree of cross-linking in order to suppress dust generation in the alignment film. The value (1- (Ma / Mb)) obtained by subtracting 1 from the ratio (Ma / Mb) of the amount (Ma) of the crosslinking agent remaining after crosslinking to the amount (Mb) of the crosslinking agent added to the coating solution. When Mb)) is defined as the degree of crosslinking, the degree of crosslinking is preferably 50% to 100%, more preferably 65% to 100%, and most preferably 75% to 100%.

In the present invention, the polymer used for the alignment film may be either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent. Of course, a polymer having both functions can also be used. Examples of the polymer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol acrylamide), styrene / vinyl toluene copolymer. , Polymers such as chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene and polycarbonate, and Examples of the compound include a silane coupling agent. Examples of preferred polymers are water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol and modified polyvinyl alcohol, with gelatin, polyvinyl alcohol and modified polyvinyl alcohol being preferred, especially polyvinyl alcohol and Mention may be made of modified polyvinyl alcohol.

Among the above polymers, polyvinyl alcohol or modified polyvinyl alcohol is preferable. The polyvinyl alcohol has, for example, a saponification degree of 70 to 100%, generally a saponification degree of 80 to 100%, and more preferably a saponification degree of 85 to 95%. As a polymerization degree, the range of 100-3000 is preferable. Examples of the modified polyvinyl alcohol include those modified by copolymerization (for example, COONa, Si (OX) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ COO, SO ₃ , Na, C ₁₂ H ₂₅ Etc.), modified by chain transfer (for example, COONa, SH, C ₁₂ H ₂₅ etc. are introduced as modifying groups), modified by block polymerization (modified groups, for example, COOH, CONH ₂ , COOR, C ₆ H _5, etc. are introduced). As a polymerization degree, the range of 100-3000 is preferable. Among these, unmodified or modified polyvinyl alcohol having a saponification degree of 80 to 100% is preferable, and unmodified or alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% is more preferable.

The modified polyvinyl alcohol used for the alignment film is preferably a reaction product of a compound represented by the following general formula (1) and polyvinyl alcohol.
General formula (1)

R ¹ represents an unsubstituted alkyl group, or an alkyl group substituted with an acrylolyl group, a methacryloyl group or an epoxy group, W represents a halogen atom, an alkyl group or an alkoxy group, X represents an active ester, an acid anhydride Alternatively, it represents an atomic group necessary for forming an acid halide, l represents 0 or 1, and n represents an integer of 0 to 4.

Moreover, as the modified polyvinyl alcohol used for the alignment film, a reaction product of a compound represented by the following general formula (2) and polyvinyl alcohol is also preferable.
General formula (2)

However, X ¹ represents an atomic group necessary to form an active ester, acid anhydride or acid halide, m is an integer of 2 to 24.

As the polyvinyl alcohol used for reacting with the compounds represented by the general formula (1) and the general formula (2), the unmodified polyvinyl alcohol and the copolymer-modified one, that is, modified by chain transfer. And modified products of polyvinyl alcohol such as those modified by block polymerization. Preferred examples of the specific modified polyvinyl alcohol are described in detail in JP-A-8-338913.
In the case of using a hydrophilic polymer such as polyvinyl alcohol for the alignment film, it is preferable to control the water content from the viewpoint of the degree of hardening, preferably 0.4% to 2.5%, 0.6% More preferably, it is -1.6%. The water content can be measured with a commercially available Karl Fischer moisture content measuring device.
The alignment film preferably has a thickness of 10 μm or less.

Next, the manufacturing method of the optical compensation film of this invention is demonstrated.
[Method for producing optical compensation film]
The method for producing an optical compensation film of the present invention includes, for example, the following steps (1) to (4):
(1) A step of rubbing the surface of the support or the surface of the alignment film formed on the support;
(2) A step of applying a coating liquid containing a polymerizable liquid crystal compound on the rubbed support or the alignment film surface to form a liquid crystal compound layer;
(3) The step of orienting the liquid crystal compound layer at a temperature equal to or higher than the liquid crystal transition temperature and fixing the orientation to form an optically anisotropic layer simultaneously with or after the liquid crystal compound layer is dried;
(4) The method further comprises a step of heating the optically anisotropic layer after fixing the orientation of the liquid crystal compound. The said process can be performed continuously.

  In the manufacturing method of the present invention, the film surface wind speed on the surface of the liquid crystal compound layer that blows in a direction other than the rubbing direction of the rubbing process during the orientation in the step (3) satisfies the following formula (1). It is preferable to make it.

Formula (1) 0.1 <V <5.0 × 10 ⁻³ × η

In the formula, V represents the film surface wind speed (m / sec) on the surface of the liquid crystal compound layer, and η represents the viscosity (cp) of the liquid crystal compound layer at the alignment temperature of the liquid crystal compound.
Furthermore, the film surface speed V is preferably 0.1 to 2.5 × 10 ⁻³ × η.

According to the production method of the present invention, since the wind speed and direction of the wind blown on the surface of the liquid crystal compound layer are controlled, the average direction of the molecular symmetry axis of the liquid crystal compound in the optically anisotropic layer is relative to the desired direction. The optical compensation film which is substantially 0 °, that is, preferably −2 ° to 2 °, more preferably −1 ° to 1 ° can be continuously and stably manufactured, and is suitable for mass production.
When an optical compensation film is applied to a liquid crystal display device, particularly an OCB mode liquid crystal display device, the average direction of the molecular symmetry axis of the liquid crystal compound in the optical anisotropic layer and the in-plane slow axis of the support are substantially In order to exhibit an excellent optical compensation function, it is desirable that the angle is 45 °, that is, preferably 43 ° to 47 °, more preferably 44 ° to 46 °. As described above, according to the production method of the present invention, since the average direction of the molecular symmetry axis can be produced so as to coincide with a desired direction, the average direction of the molecular symmetry axis and the in-plane slow axis of the support Can be easily made within the above range.
The in-plane slow axis of the support usually coincides with the longitudinal direction when the support is a long polymer film.

The production method of the present invention is also suitable for producing a roll-shaped optical compensation film. That is,
(1 ′) a step of rubbing the surface of the long support conveyed in the longitudinal direction or the surface of the alignment film formed on the support;
(2) A step of applying a coating liquid containing a polymerizable liquid crystal compound on the rubbed support or the alignment film surface to form a liquid crystal compound layer;
(3) The step of orienting the liquid crystal compound layer at a temperature equal to or higher than the liquid crystal transition temperature and fixing the orientation to form an optically anisotropic layer simultaneously with or after the liquid crystal compound layer is dried;
(4) A step of further heating the optically anisotropic layer after fixing the alignment of the liquid crystal compound; (5) a step of winding the elongated laminate on which the optically anisotropic layer is formed; The roll-shaped optical compensation film can be continuously and stably produced by continuously performing the above.

Moreover, the production method of the present invention comprises:
1) In the step (3), the coating layer is continuously irradiated with light, the polymerizable liquid crystal compound is cured by polymerization and fixed in an aligned state, and then the step (4) is continuously performed. And / or 2) In the step (1), rubbing with a rubbing roller while removing the surface of the support or the alignment film, and / or rubbing before the step (2). A step of removing dust from the surface of the treated support or the alignment film may be carried out; and / or 3) before the step (5), the optical properties of the formed optically anisotropic layer are continuously measured. An inspection step for inspecting by measuring may be included.
Details of each of these steps are described in JP-A-9-73081.

Hereinafter, each process will be described.
<< Step (1) >>
In the step (1), a rubbing treatment is applied to the surface of the support or the surface of the alignment film formed on the support.

  The rubbing treatment is preferably performed with a rubbing roller. The diameter of the rubbing roller to be used is preferably 100 mm to 500 mm, more preferably 200 mm to 400 mm, from the viewpoints of handling suitability and fabric life. The width of the rubbing roller needs to be wider than the width of the support, and is preferably at least film width × √2. The number of rotations of the rubbing roller is preferably set low from the viewpoint of dust generation, and depending on the orientation of the liquid crystal compound, it is preferably 100 rpm to 1000 rpm, and more preferably 250 rpm to 850 rpm.

In order to maintain the orientation of the liquid crystal compound even when the number of rotations of the rubbing roll is lowered, it is preferable to heat the support or the alignment film during rubbing. The heating temperature is the film surface temperature of the support or the alignment film, and is preferably (material Tg−50 ° C.) to (material Tg + 50 ° C.). When using an alignment film made of polyvinyl alcohol, it is preferable to control the environmental humidity of rubbing, and it is preferable that the relative humidity at 25 ° C. is 25% RH to 70% RH, and 30% RH to 60% RH. More preferably, it is most preferably 35% RH to 55% RH.

Even when the optical compensation film to be manufactured is not in the form of a roll, it is preferable from the viewpoint of productivity to perform the rubbing treatment while conveying the support.
The conveyance speed of the support is preferably 10 m / min to 100 m / min, more preferably 15 m / min to 80 m / min, from the viewpoints of productivity and liquid crystal orientation. The conveyance can be performed using various apparatuses conventionally used for film conveyance, and the conveyance method is not particularly limited.

  The alignment film can be produced by applying a coating solution prepared by dissolving the above-described material such as polyvinyl alcohol in water and / or an organic solvent on the surface of the support and drying it. The alignment film can be produced before the series of steps described above, and the alignment film may be continuously produced on the surface of the support to be conveyed.

<< Step (2) >>
In the step (2), a coating liquid containing a liquid crystal compound (hereinafter also referred to as a coating liquid for forming an optically anisotropic layer) is applied to the rubbing surface. As the solvent used for preparing the coating liquid for forming the optically anisotropic layer, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

In order to produce a highly uniform optically anisotropic layer, the surface tension of the coating liquid for forming the optically anisotropic layer is preferably 25 mN / m or less, more preferably 22 mN / m or less. preferable.
In order to realize this low surface tension, a coating liquid for forming an optically anisotropic layer is used in a surfactant or a fluorine compound, particularly a repeating unit corresponding to the monomer (1) below and a monomer (2) below. It is preferable to contain a fluorine-based polymer such as a fluoroaliphatic group-containing copolymer containing a repeating unit corresponding to.
(1) Fluoroaliphatic group-containing monomer represented by the following general formula (3) (2) Poly (oxyalkylene) acrylate and / or poly (oxyalkylene) methacrylate General formula (3)

In the general formula (3), R ² represents a hydrogen atom or a methyl group, X represents an oxygen atom, a sulfur atom or —N (R ³ ) —, p is an integer of 1 to 6, q is 2 or 3 Represents an integer. R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

  The mass average molecular weight of the fluoropolymer added to the coating liquid for forming the optically anisotropic layer is preferably 3000 to 100,000, and more preferably 6,000 to 80,000. Furthermore, the addition amount of the fluorine-based polymer is preferably 0.005 to 8% by mass, and 0.01 to 1% by mass with respect to the coating liquid composition (coating component excluding the solvent) mainly comprising a liquid crystal compound. More preferably, 0.05-0.5 mass% is further more preferable. When the addition amount of the fluorine-based polymer is less than 0.005% by mass, the effect is insufficient, and when it exceeds 8% by mass, the coating film is not sufficiently dried or performance as an optical compensation film (for example, Retardation uniformity, etc.).

  Application of the coating liquid for forming the optically anisotropic layer to the rubbing surface is performed by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method). Can be implemented. The coating amount can be appropriately determined based on the desired thickness of the optically anisotropic layer.

<< Step (3) >>
In the step (3), the optically anisotropic layer is formed by fixing the orientation of the liquid crystal compound from the liquid crystal compound layer comprising the applied coating solution. That is, simultaneously or after drying the applied coating solution, the liquid crystal compound of the coating solution is aligned at a temperature equal to or higher than the liquid crystal transition temperature, and the alignment is fixed to produce an optically anisotropic layer. . The liquid crystal compound has a desired orientation by a polymerization reaction. The drying temperature can be determined in consideration of the boiling point of the solvent used in the coating solution and the materials of the support and the alignment film. The alignment temperature of the liquid crystal compound can be determined according to the liquid crystal phase-solid phase transition temperature of the liquid crystal compound used. When a discotic liquid crystal compound is used as the liquid crystal compound, the alignment temperature is preferably 70 to 300 ° C, and more preferably 70 to 170 ° C.

Further, when the liquid crystal compound is in a liquid crystal state, the viscosity of the liquid crystal compound layer is preferably 10 cp to 10000 cp, and more preferably 100 cp to 1000 cp. If the viscosity is too low, it is easily affected by wind during orientation, and very accurate wind speed / wind direction control is required for continuous production. On the other hand, if the viscosity is high, it is difficult to be affected by the wind, but the alignment of the liquid crystal becomes slow and the productivity is very deteriorated.
The viscosity of the liquid crystal compound layer can be appropriately controlled by the molecular structure of the liquid crystal compound. Moreover, the method of adjusting to a desired viscosity by using an appropriate amount of the above-mentioned additive (especially cellulose polymer etc.), a gelatinizer, etc. is used preferably.

Heating can be carried out by blowing hot air at a predetermined temperature or by conveying in a heating chamber maintained at a predetermined temperature.
The wind speed and direction of the warm air at this time are controlled so that the wind speeds other than the rubbing direction impinging on the liquid crystal compound layer are expressed by the formula (1).

The alignment state of the aligned liquid crystal compound is maintained and fixed, and the liquid crystal compound is fixed when forming the optically anisotropic layer by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. 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 ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).
The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

It is preferable to use ultraviolet rays for light irradiation for proceeding and fixing the polymerization of the liquid crystal compound. The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, 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 light irradiation can be carried out by passing the support on which the coating liquid for forming the optically anisotropic layer is applied through a conveyance path in which one or more light sources are arranged at any one of the upper and lower and left and right positions. .

<< Step (4) >>
The step (4) is a step of further heating the optically anisotropic layer after fixing the alignment of the liquid crystal compound.
(4) In a process, heating temperature is 40 to 150 degreeC, and 50 to 130 degreeC is more preferable. The upper limit temperature is preferably not higher than the glass transition point of the support used.
The heating time is preferably 5 seconds to 3000 seconds, more preferably 10 seconds to 2800 seconds. Furthermore, the shorter the time from the orientation fixing to the post-heating, the more effective, and it is preferable to carry out between 0.1 seconds and 6000 seconds. However, even if the film that has passed the above time is heated, there is no particular limitation because a certain effect is recognized.
The present inventor has found that the strength of the polymerizable liquid crystal layer or the adhesion between the liquid crystal layer and the alignment film is remarkably improved by post-heating after fixation. Although the cause is not accurately separated, it is presumed that the polymerization reaction proceeds even after the radicals generated during the alignment fixation are activated by post-heating and the alignment of the liquid crystal layer is fixed. These factors will be clarified in the near future by the present inventors.
When the heating temperature is less than 40 ° C., the strength of the liquid crystal layer and the adhesion with the alignment film are not sufficiently improved. When the heating temperature exceeds 150 ° C., when a support having a relatively low Tg is used, the characteristics of the support Changes and the like may be induced, which is not preferable. Further, if the heating time is less than 5 seconds, the strength of the liquid crystal layer and the adhesion with the alignment film are not sufficiently improved, and if it exceeds 3000 seconds, it is not preferable from the viewpoint of productivity.

  In the case of producing a roll-shaped optical compensation film, the step (5) is performed following the step (4). Before shifting to the step (5), a protective layer may be provided on the optically anisotropic layer produced in the step (4). For example, a protective layer film prepared in advance may be continuously laminated on the surface of the optically anisotropic layer prepared in a long shape.

In the step (5), the long laminate on which the optically anisotropic layer is formed is wound up. The winding may be performed, for example, by winding a support having an optically anisotropic layer that is continuously conveyed around a cylindrical core.
Since the optical compensation film obtained by the step (5) is in the form of a roll, it can be easily handled even when manufactured in large quantities. It can be stored and transported as it is.

  The conditions and apparatuses described in JP-A-9-73081 can be applied to the details of the conditions of each step of the production method of the present invention and the usable apparatus.

[Polarizer]
The polarizing plate of the present invention has the optical compensation film of the present invention and a polarizing film. In the case of using a roll-shaped optical compensation film, the roll-shaped optical compensation film may be bonded to a polarizing film after being cut into a desired shape such as a rectangular shape. After bonding, it can also be cut into a desired shape. In the case of a roll-shaped optical compensation film, it can be bonded to a long polarizing film by roll-to-roll, which is advantageous in terms of productivity.
The polarizing plate of the present invention has not only a polarizing function but also an excellent optical compensation function, and can be easily incorporated into a liquid crystal display device. Moreover, the aspect which used the said optical compensation film as the protective film of a polarizing film contributes also to thickness reduction of a liquid crystal display device.

Hereinafter, specific examples of materials and manufacturing methods used for each member will be described.
<Polarizing film>
The polarizing film used for the polarizing plate of the present invention is preferably a coating type polarizing film represented by Optiva Inc., or a polarizing film comprising a binder and iodine or a dichroic dye. The iodine and the dichroic dye exhibit 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-assembly such as liquid crystal. A commercially available polarizing film is generally 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. . In addition, commercially available polarizing films have iodine or dichroic dye distributed about 4 μm from the polymer surface (about 8 μm on both sides), and a thickness of at least 10 μm is necessary to obtain sufficient polarization performance. is there. The penetrability can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the bath, and the immersion time.
As described above, the lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness 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. It is preferably not more than a commercially available polarizing plate (about 30 μm), preferably 25 μm or less, and more preferably 20 μm or less. When the thickness is 20 μm or less, the light leakage phenomenon is not observed on a 17-inch liquid crystal display device.

The binder of the polarizing film may be cross-linked. As the binder for the polarizing film, a polymer that can be crosslinked by itself may be used. A polarizing film can be formed by applying light, heat, or pH change to a polymer having a functional group or a polymer obtained by introducing a functional group into the polymer to react the functional group to crosslink between the polymers. it can. Moreover, you may introduce | transduce a crosslinked structure into a polymer with a crosslinking agent. It can be formed by cross-linking between binders by introducing a bonding group derived from the cross-linking agent between binders using a cross-linking agent which is a compound having high reaction activity.
In general, crosslinking can be performed by applying a coating solution containing a crosslinkable polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. Since it is only necessary to ensure durability at the final product stage, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained.

As described above, 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 polymers include polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, polystyrene, polyvinyl alcohol, modified polyvinyl alcohol, poly (N-methylol acrylamide), polyvinyl toluene, chlorosulfonated polyethylene, nitrocellulose, chlorinated polyolefin ( Eg, polyvinyl chloride), polyester, polyimide, polyvinyl acetate, polyethylene, carboxymethylcellulose, polypropylene, polycarbonate and copolymers thereof (eg, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, styrene / vinyl) Toluene copolymer, vinyl acetate / vinyl chloride copolymer, ethylene /
Vinyl acetate copolymer). A silane coupling agent may be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol and modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. .

The saponification degree of polyvinyl alcohol and modified polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%, and most preferably 95 to 100%. As for the polymerization degree of polyvinyl alcohol, 100-5000 are preferable.
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 chain transfer modification, COONa, SH, or C ₁₂ H ₂₅ can be introduced as a modifying group. The degree of polymerization of the modified polyvinyl alcohol is preferably 100 to 3000. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127.
Unmodified polyvinyl alcohol and alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% are particularly preferable.
Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

The crosslinking agent is described in US Reissue Patent 23297 and can be used in the present invention. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent.
When a large amount of the crosslinking agent for the binder is added, the heat and humidity 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. 0.1-20 mass% is preferable with respect to a binder, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. The binder contains 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 in the binder, and more preferably 0.5% by mass or less. 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 dichroic dye include azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, and anthraquinone dyes. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl). Examples of dichroic dyes 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 is included. As for the dichroic dyes, those described in JP-A-1-161202, 1-172906, 1-172907, 1-183602, 1-248105, 1-265205, 7-261024 are used. There are descriptions in each publication.

The dichroic dye is used as a free acid or a salt such as an alkali metal salt, ammonium salt or amine salt. By blending two or more kinds of dichroic dyes, polarizing films having various hues can be produced. A polarizing film using a compound (pigment) that exhibits a black color when the polarization axes are orthogonal to each other, or a polarizing film or a polarizing plate that is blended with various dichroic molecules so as to exhibit a black color, have both a single-plate transmittance and a polarizing coefficient. It is excellent and preferable.

<Manufacture of polarizing film>
From the viewpoint of yield, the polarizing film is stretched at an angle of 10 to 80 degrees with respect to the longitudinal direction (MD direction) of the polarizing film (stretching method) or rubbed (rubbing method). It is preferable to dye with a dichroic dye. The tilt angle is preferably stretched so as to match the angle formed between the transmission axis of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the LCD and the vertical or horizontal direction of the liquid crystal cell. A normal inclination angle is 45 °. Recently, however, devices that are not necessarily 45 ° have been developed for transmissive, reflective, and transflective LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted in accordance with the design of the LCD.

In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of 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 can be stretched more uniformly even at high magnification. Before the oblique stretching, a slight stretching (a degree to prevent shrinkage in the width direction) may be performed horizontally or vertically. 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. In biaxial stretching, stretching is performed at different speeds on the left and right, so that 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.
As described above, a binder film that is obliquely stretched by 10 to 80 degrees with respect to the conveyance direction of the polarizing film is manufactured.

In the rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, orientation is obtained by rubbing the surface of the film in a certain direction using paper, gauze, felt, rubber, nylon, or polyester fiber. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are planted on average. It is preferable to carry out using a rubbing roll in which the roundness, cylindricity, and deflection (eccentricity) of the roll itself 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 be obtained by winding 360 ° or more.
When rubbing a long film, the film is preferably transported at a speed of 1 to 100 m / min in a constant tension state by a transport device. The rubbing roll is preferably rotatable in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °. When used in a liquid crystal display device, the angle is preferably 40 to 50 °. 45 ° is particularly preferred.

It is preferable to arrange protective films on both sides of the polarizing film, and it is preferable to use the optical compensation film of the present invention as the protective film on one side. For example, a laminate in which a protective film / polarizing film / support / optically anisotropic layer and protective film / polarizing film / support / alignment film / optically anisotropic layer are laminated in this order is preferable. However, it is not limited to this configuration, and the polarizing film and the surface side of the optically anisotropic layer may be bonded together. Adhesives may be used for bonding, for example, polyvinyl alcohol resins (including modified polyvinyl alcohols with acetoacetyl groups, sulfonic acid groups, carboxyl groups, and oxyalkylene groups) and aqueous boron compound solutions are used as adhesives. Can do. Of these, polyvinyl alcohol resins are preferred.
The thickness of the adhesive layer is preferably in the range of 0.01 to 10 μm after drying, and particularly preferably in the range of 0.05 to 5 μm.

  Moreover, when using the polarizing plate of this invention for a liquid crystal display device, it is preferable to install an antireflection layer in the visual recognition side surface, and this antireflection layer may be combined with the protective layer of the visual recognition side of a polarizing film. From the viewpoint of suppressing a change in tint depending on the viewing angle of the liquid crystal display device, the internal haze of the antireflection layer is preferably 50% or more. Specific examples of these are described in JP-A Nos. 2001-33783, 2001-343646, and 2002-328228.

  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 of the present invention is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and in the range of 40 to 50% in light having a wavelength of 550 nm. Is most preferred. The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% in light having a wavelength of 550 nm.

[Liquid Crystal Display]
The optical compensation film of the present invention or the polarizing plate using the optical compensation film is advantageously used in a liquid crystal display device, particularly an OCB liquid crystal display device and an ECB reflective liquid crystal display device.
The transmissive liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates.
One optical compensation film is disposed between the liquid crystal cell and one polarizing plate, or two optical compensation films are disposed between the liquid crystal cell and both polarizing plates. When an optical compensation film is used as a protective film for a polarizing plate, the polarizing plate also serves as an optical compensation film, which is preferable in terms of reducing the thickness and weight of the liquid crystal display device.

The liquid crystal cell can be in VA mode, OCB mode, IPS mode, or TN mode.
In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied.
The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625) (2) Liquid crystal cell (SID97, Digest of tech. Papers (Preliminary Proceed) 28 (1997) 845 in which the VA mode is converted into a multi-domain (MVA mode) for widening the viewing angle. ), (3) A liquid crystal cell in a mode (n-ASM 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 (Preliminary collections 58-59 of the Japan Liquid Crystal Society) (1998)) and (4) SURVAVAL mode liquid crystal cells (announced at LCD International 98).
The OCB mode liquid crystal cell is a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell. Liquid crystal display devices using a bend alignment mode liquid crystal cell are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function.
For this reason, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed.
In the TN mode liquid crystal cell, rod-like liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and are twisted and aligned at 60 to 120 °.
The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.
The liquid crystal display device of the ECB system is a liquid crystal having the longest known configuration using a horizontal alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned in substantially the same direction at the top and bottom of the liquid crystal cell. It is a display device.

  Hereinafter, the present invention will be described more specifically with reference to examples. The materials, reagents, ratios, operations and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[Example 1]
-Optical compensation film for OCB-

(Production of optical compensation film)
(Production of support)
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)
Cellulose acetate with an acetylation degree of 60.9% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (No. 1) 2 solvents) 45 parts by mass Dye (360FP, manufactured by Sumika Finechem Co., Ltd.) 0.0009 parts by mass

In another mixing tank, 16 parts by mass of the following retardation increasing agent, 80 parts by mass of methylene chloride and 20 parts by mass of methanol were added and stirred while heating to prepare a retardation increasing agent solution.
A dope was prepared by mixing 464 parts by mass of the cellulose acetate solution having the above composition with 36 parts by mass of the retardation increasing agent solution and 1.1 parts by mass of silica fine particles (R972 manufactured by Irosil) and stirring sufficiently. The addition amount of the retardation increasing agent was 5.0 parts by mass with respect to 100 parts by mass of cellulose acetate. Moreover, the addition amount of silica fine particles was 0.15 mass part with respect to 100 mass parts of cellulose acetate.

The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., it was dried for 1 minute, peeled off, and then stretched 28% in the width direction using a tenter with a drying air of 140 ° C. Then, it dried for 20 minutes with 135 degreeC dry air, and manufactured the support body (PK-1) whose residual solvent amount is 0.3 mass%.
The obtained support (PK-1) had a width of 1340 mm and a thickness of 92 μm. It was 38 nm when the retardation value (Re) in wavelength 590nm was measured using the ellipsometer (M-150, JASCO Corporation make). Moreover, it was 175 nm when the retardation value (Rth) in wavelength 590nm was measured.

A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is formed on the band surface side of the produced support (PK-1). the 10 cc / m ² was applied, after holding for 30 seconds in a state of about 40 ° C., scraped alkali solution, then washed with pure water, and remove the water droplets in the air knife. Then, it dried at 100 degreeC for 15 second. The contact angle of PK-1 with respect to pure water was found to be 42 °.

(Preparation of alignment film)
On this PK-1 (alkali-treated surface), an alignment film coating solution having the following composition was applied at 28 ml / m ² with a # 16 wire bar coater. 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.

(Orientation film coating solution composition)
Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight Citrate ester (AS3 manufactured by Sankyo Chemical) 0.35 parts by weight

(Rubbing process)
PK-1 is transported at a speed of 20 m / min, a rubbing roll (300 mm diameter) is set so as to be rubbed at 45 ° with respect to the longitudinal direction, rotated at 650 rpm, and an alignment film installation surface of PK-1 The rubbing process was given to. The contact length between the rubbing roll and PK-1 was set to 18 mm.

(Formation of optically anisotropic layer)
On the alignment film, 41.01 kg of the following discotic liquid crystal compound, 4.06 kg of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB531-1, yeast) Manchemical Co., Ltd.) 0.35 Kg, Photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 1.35 Kg, Sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 0.45 Kg, Citrate (Three AS3) Kyo Kagaku AS3) 0.1 kg of fluoroaliphatic group-containing copolymer (Megafac F780 manufactured by Dainippon Ink, Inc.) was added to a coating solution in which 0.45 kg was dissolved in 102 kg of methyl ethyl ketone, and # 3. Rotate the 0 wire bar in 391 rotations in the same direction as the film transport direction, It was continuously coated on the orientation film surface of PK-1, which is conveyed by the m / min.

In the process of continuously heating from room temperature to 100 ° C., the solvent is dried, and then the film surface wind speed of the discotic liquid crystal compound layer is 2.5 m / sec parallel to the film transport direction in the 130 ° C. drying zone. And heated for about 90 seconds to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 40 ° C., and an ultraviolet ray with an illuminance of 600 mW is applied by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) with the surface temperature of the film being about 60 ° C. Irradiation was carried out for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound was fixed to the orientation. After that, it was passed through a zone at 60 ° C. for about 1 minute, allowed to cool to room temperature, and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film (KH-1) was produced.
The discotic liquid crystal compound has a liquid crystal transition temperature of 115 ° C., the film surface temperature of the discotic liquid crystal compound layer in the 130 ° C. drying zone is 127 ° C., and the viscosity of the layer at this temperature is It was 695 cp. The viscosity was measured with a heating E-type viscosity system for a liquid crystal layer (excluding the solvent) having the same composition ratio as the layer.

A part of the produced roll-shaped optical compensation film (KH-1) was cut out and used as a sample to measure optical characteristics. The Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm was 31 nm. In addition, the angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface continuously changed in the depth direction of the layer, and was 28 ° on average. Furthermore, when only the optically anisotropic layer was peeled from the sample and the average direction of the molecular symmetry axis of the optically anisotropic layer was measured, it was 45 ° with respect to the longitudinal direction of the optical compensation film (KH-1). It was.
Furthermore, when the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation film was observed, no unevenness was detected even when viewed from the front and the direction inclined to 60 ° from the normal.
The thickness of the discotic liquid crystal layer was 1.28 μm as measured with a film thickness sensor Z5FM-200 manufactured by OMRON Corporation.

[Comparative Example 1]
In the same manner as in Example 1, a rubbed alignment film was produced on the support.
(Formation of optically anisotropic layer)
On this alignment film, a coating solution similar to that in Example 1 was prepared, and the wire bar # 3.4 was rotated 391 times in the same direction as the film conveying direction, and the PK being conveyed at 20 m / min. The film was continuously applied to the alignment film surface of -1.

In the process of continuously heating from room temperature to 100 ° C., the solvent is dried, and then the film surface wind speed of the discotic liquid crystal compound layer is 2.5 m / sec parallel to the film transport direction in the 130 ° C. drying zone. And heated for about 90 seconds to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 80 ° C., and an ultraviolet ray irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) is irradiated with ultraviolet rays having an illuminance of 600 mW with the film surface temperature being about 120 ° C. Irradiation was carried out for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound was fixed to the orientation. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film (KH-H1) was produced.
The film surface temperature of the discotic liquid crystal compound layer in the 130 ° C. drying zone was 127 ° C.

A part of the produced roll-shaped optical compensation film (KH-H1) was cut out and used as a sample to measure optical characteristics. That is, using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), the light incident angle dependency of Re of the manufactured film is measured, and the contribution of the support measured in advance is subtracted. Thus, when the optical properties of only the optically anisotropic layer were calculated, the Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm was 33 nm. In addition, the angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface continuously changed in the depth direction of the layer, and was 29 ° on average. Furthermore, when only the optically anisotropic layer was peeled from the sample and the average direction of the molecular symmetry axis of the optically anisotropic layer was measured, it was 45 ° with respect to the longitudinal direction of the optical compensation film (KH-H1). It was.
Furthermore, when the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation film was observed, no unevenness was recognized in the front, but when viewed from a direction tilted to 70 ° from the normal, very thin optical Unevenness (film transport direction) was detected.
The thickness of the discotic liquid crystal layer was 1.45 μm as measured by a film thickness sensor Z5FM-200 manufactured by OMRON Corporation.

In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at wavelength λ, respectively. Re (λ) is measured in KOBRA 21ADH (manufactured by Oji Scientific Instruments) by making light having a wavelength of λ nm incident in the normal direction of the film. Rth (λ) is the light of wavelength λnm from the direction inclined by + 40 ° with respect to the normal direction of the film, with Re (λ) and the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotation axis) And a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH calculates based on the retardation value measured in three directions, the assumed value of the average refractive index, and the input film thickness value. Here, as the assumed value of the average refractive index, the values in the polymer handbook (JOHN WILEY & SONS, INC) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer.
The average refractive index values of the main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). KOBRA 21ADH calculates nx, ny, and nz by inputting these assumed values of average refractive index and film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

[Comparative Example 2]
In the same manner as in Example 1, a rubbed alignment film was produced on the support.
(Formation of optically anisotropic layer)
On this alignment film, a coating solution similar to that in Example 1 was prepared, and a # 3.0 wire bar was rotated 391 times in the same direction as the film conveying direction, and the PK being conveyed at 20 m / min. -1 was continuously applied to the alignment film surface.
In the process of continuously heating from room temperature to 100 ° C., the solvent is dried, and then the film surface wind speed of the discotic liquid crystal compound layer is 2.5 m / sec parallel to the film transport direction in the 130 ° C. drying zone. And heated for about 90 seconds to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 40 ° C., and an ultraviolet ray with an illuminance of 600 mW is applied by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) with the surface temperature of the film being about 60 ° C. Irradiation was performed for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound was fixed to the orientation, allowed to cool to room temperature, wound into a cylindrical shape, and formed into a roll shape. In this way, a roll-shaped optical compensation film (KH-H2) was produced.

A part of the produced roll-shaped optical compensation film (KH-H2) was cut out and used as a sample to measure optical characteristics. The Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm was 31 nm. In addition, the angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface continuously changed in the depth direction of the layer, and was 28 ° on average. Furthermore, only the optically anisotropic layer was peeled from the sample, and the average direction of the molecular symmetry axis of the optically anisotropic layer was measured. As a result, it was 45 ° with respect to the longitudinal direction of the optical compensation film (KH-H2). It was.
Furthermore, when the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation film was observed, no unevenness was detected even when viewed from the front and the direction inclined to 60 ° from the normal. The thickness of the discotic liquid crystal layer was 1.28 μm as measured with a film thickness sensor Z5FM-200 manufactured by OMRON Corporation.

[Example 2]
-Optical compensation film for IPS-
(Film formation of cellulose acylate film)
Cellulose acylate having an acetyl substitution degree of 2.785 (6-position acetyl substitution degree of 0.910) was prepared. In this, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid was added, and an acylation reaction was performed at 40 ° C. Thereafter, the total substitution degree and the 6-position substitution degree were adjusted by adjusting the amount of sulfuric acid catalyst, the amount of water, and the aging time. The aging temperature was 40 ° C. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.
Dope preparation 11.7 parts by mass of a plasticizer (2: 1 mixture of triphenyl phosphate and biphenyl diphenyl phosphate) and 6.5 parts by mass of a retardation developer having the following structure were added to the above cellulose acylate, The mixture was stirred and dissolved in dichloromethane / methanol (87/13 parts by mass) with stirring so that the mass concentration of the solid content was 19% by mass. At the same time, 0.05 parts by mass of fine particles (silicon dioxide (primary particle size 20 nm, Mohs hardness of about 7)) and UV absorber B (manufactured by TINUVIN327 Ciba Specialty Chemicals) 0 parts per 100 parts by mass of cellulose acylate 375 parts by mass, 0.75 part by mass of UV absorber C (manufactured by TINUVIN328 Ciba Specialty Chemicals) were added and stirred while heating. The addition ratio of the plasticizer and the retardation developer is part by mass when the cellulose acylate amount is 100 parts by mass. PK-2 was produced from the dope thus produced by the following method.
Retardation agent

(Casting)
The above dope was cast using a band casting machine. A film peeled off from the band with a residual solvent amount of 25 to 35% by mass was stretched in the width direction at a stretch rate of 15% using a tenter to produce a cellulose acylate film. The tenter was stretched in the width direction while being dried by applying hot air, and then contracted by about 5%, then transferred from the tenter conveyance to the roll conveyance, further dried, knurled and wound up.
The obtained support (PK-2) had a width of 1340 mm and a thickness of 80 μm. When the retardation value (Re) at a wavelength of 590 nm was measured using an ellipsometer (M-150, manufactured by JASCO Corporation), it was 63 nm. Moreover, it was 223 nm when the retardation value (Rth) in wavelength 590nm was measured.

On the band surface side of the cellulose acylate film (PK-2), a 1.0 N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts / 15 parts by weight / 15.8 parts by weight) ) Was applied at 10 cc / m ² and held at a temperature of about 40 ° C. for 30 seconds, then the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second.
The contact angle of the alkali-treated surface with pure water was measured and found to be 42 °.

(Formation of alignment film)
On this cellulose acylate film (alkali-treated surface), a commercially available vertical alignment film (JALS-204R, manufactured by Nippon Synthetic Rubber Co., Ltd.) was diluted 1: 1 with methyl ethyl ketone, and then 2.4 ml / ml with a wire bar coater. m ^{2 was} applied. Immediately, it was dried with warm air of 120 ° C. for 120 seconds.

Next, 3.8 g of the following rod-like liquid crystalline compound, 0.06 g of photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy), 0.02 g of sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.), A solution prepared by dissolving 0.002 g of the air interface side vertical alignment agent in 9.2 g of methyl ethyl ketone was prepared. This solution was applied to the alignment film side of the film on which the alignment film was formed, using a # 5.2 wire bar. This was attached to a metal frame and heated in a constant temperature bath at 100 ° C. for 2 minutes to align the rod-like liquid crystal compound. The liquid crystal transition temperature of the rod-like liquid crystal compound was 80 ° C. Next, UV irradiation is performed for 20 seconds with a 120 W / cm high-pressure mercury lamp at 30 ° C. to crosslink the rod-like liquid crystalline compound, and after that, after heating at 70 ° C./30 seconds, it is allowed to cool to room temperature to produce an optically anisotropic layer. did. In this way, an optical compensation film (KH-2) was produced.
When the viscosity of the optically anisotropic layer was measured at a film surface temperature of 90 ° C., it was 495 cp. The viscosity is a result of measuring a liquid crystal layer (excluding the solvent) having the same composition as the optically anisotropic layer with a heating E-type viscosity system.

The support body which measured the light incident angle dependence of Re of the produced optical compensation film (KH-2) using the automatic birefringence meter (KOBRA-21ADH, Oji Scientific Instruments Co., Ltd.), and measured beforehand. When the optical properties of the optically anisotropic layer alone were calculated by subtracting the contribution of the optically anisotropic layer, the Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm was 0 nm and Rth was −260 nm. It was confirmed that the rod-like liquid crystal was aligned substantially vertically.
Furthermore, when the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation film was observed, no unevenness was detected even when viewed from the front and the direction inclined to 60 ° from the normal.
The thickness of the discotic liquid crystal layer was 2.07 μm as measured by a film thickness sensor Z5FM-200 manufactured by OMRON Corporation.

[Comparative Example 3]
In the same manner as in Example 2, a coating liquid for forming a rod-like liquid crystal layer was prepared, and this solution was applied to the alignment film side of the film on which the alignment film was formed with a wire wire # 5.2. This was attached to a metal frame and heated in a constant temperature bath at 100 ° C. for 2 minutes to align the rod-like liquid crystal compound. Next, UV irradiation was performed at 30 ° C. with a 120 W / cm high-pressure mercury lamp for 20 seconds to crosslink the rod-like liquid crystalline compound and allowed to cool to room temperature to prepare an optically anisotropic layer.
Furthermore, when the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation film was observed, no unevenness was detected even when viewed from the front and the direction inclined to 60 ° from the normal.
The thickness of the discotic liquid crystal layer was 2.07 μm as measured by a film thickness sensor Z5FM-200 manufactured by OMRON Corporation.

[Example 3]
(Preparation of polarizing plate)
A PVA film (thickness 80 μm, width 2500 mm) having an average polymerization degree of 1700 and a saponification degree of 99.5 mol% was longitudinally uniaxially stretched 8 times in warm water at 40 ° C., and the iodine 0.2 g / l, potassium iodide 60 g / was immersed in an aqueous solution of 1 at 30 ° C. for 5 minutes, and then immersed in an aqueous solution of boric acid 100 g / l and potassium iodide 30 g / l. At this time, the film width was 1300 mm and the thickness was 17 μm.
The film was further immersed in a washing layer at 20 ° C. for 10 seconds, and then immersed in an aqueous solution of iodine 0.1 g / l and potassium iodide 20 g / l at 30 ° C. for 15 seconds. It dried for a time and obtained the iodine type polarizer (HF-1).

Using a polyvinyl alcohol-based adhesive, KH-1 (optical compensation film) produced in Example 1 was attached to one side of the polarizer (HF-1) on the support (PK-1) surface. Moreover, the saponification process was performed to the 80-micrometer-thick triacetylcellulose film (TD-80U: Fuji Photo Film Co., Ltd. product), and it affixed on the other side of the polarizer using the polyvinyl alcohol-type adhesive agent.
The longitudinal direction of the polarizer and the longitudinal direction of the support (PK-1), and further the longitudinal direction of the commercially available triacetyl cellulose film were all arranged in parallel. In this way, a polarizing plate (HB-1BR) was produced.

Moreover, KH-1 (optical compensation film) produced in Example 1 was affixed on one side of the polarizer (HF-1) on the support (PK-1) surface using a polyvinyl alcohol-based adhesive. Further, a film with an antireflection function (Fuji Film CV Clearview UA: manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to the opposite side of the polarizer using a polyvinyl alcohol-based adhesive.
The longitudinal direction of the polarizer and the longitudinal direction of the support (PK-1), and further, the longitudinal direction of the commercially available film with an antireflection function were all arranged in parallel. In this way, the polarizing plate (HB-
1BF) was produced.

[Comparative Examples 4 and 5]
In Example 3, instead of the optical compensation film KH-1, KH-H1 produced in Comparative Example 1 was used to produce polarizing plates (HB-H1BR) and (HB-H1BF), and the optical compensation film KH- In place of 1, KH-H2 produced in Comparative Example 2 was used to produce polarizing plates (HB-H2BR) and (HB-H2BF).

[Example 4]
<Production of Polarizing Plate Protective Film 1>
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose acetate solution A was prepared.
<Composition of cellulose acetate solution A>
Cellulose acetate having a substitution degree of 2.86 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (second solvent) ) 54 parts by mass 1-butanol 11 parts by mass

  The following composition was charged into another mixing tank, stirred while heating to dissolve each component, and an additive solution B-1 was prepared.

<Additive solution B-1 composition>
Methylene chloride 80 parts by mass Methanol 20 parts by mass The following optical anisotropy reducing agent 40 parts by mass

To 477 parts by mass of the cellulose acetate solution A, 40 parts by mass of the additive solution B-1 was added and stirred sufficiently to prepare a dope. The dope was cast from a casting port onto a drum cooled to 0 ° C. The film is peeled off at a solvent content of 70% by mass, and both ends in the width direction of the film are fixed with a pin tenter (the pin tenter described in FIG. 3 of JP-A-4-1009), and the solvent content is 3-5% by mass. In this state, the film was dried while maintaining an interval at which the stretching ratio in the transverse direction (direction perpendicular to the machine direction) was 3%. Then, it further dried by conveying between the rolls of the heat processing apparatus, and produced the polarizing plate protective film 1 with a thickness of 80 μm.
Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments), the light incident angle dependence of Re was measured, and the optical characteristics were calculated. Re was 1 nm and Rth was 6 nm. This was confirmed (λ = 590 nm).

(Preparation of polarizing plate)
The above HF-1 was used as a polarizer.
Using a polyvinyl alcohol-based adhesive, the optical compensation film (KH-2) was attached so that the transparent support surface was on the polarizer side. Further, the antireflection film (Fuji Film CV Clearview UA, manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive.
The longitudinal direction of the polarizer, the longitudinal direction of the transparent support, and the longitudinal direction of the antireflection film were all arranged in parallel. In this way, a polarizing plate (HB-2BF) was produced.
Further, after polarizing plate protective film 1 was saponified, it was attached to one side of polarizer HF-1 using a polyvinyl alcohol-based adhesive. Further, a commercially available triacetylcellulose film (TD-80U: manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. (HB-2BR). The longitudinal direction of the polarizer, the longitudinal direction of the polarizing plate protective film 1, and the longitudinal direction of the commercially available triacetyl cellulose film were all arranged in parallel.

Using a spectrophotometer (UV3100PC), 380 nm to 780 nm single plate transmittance TT, parallel transmittance PT, and orthogonal transmittance CT of polarizing plate HB-2BR at 25 ° C. and 60% RH were measured, and 400 to 700 nm. When the average value and the degree of polarization P were determined, TT was 40.8 to 44.7, PT was 34 to 38.8, CT was 1.0 or less, and P was 99.98 to 99.99. Further, the orthogonal transmittances CT ₍₃₈₀₎ , CT ₍₄₁₀₎ and CT _{(700) at} wavelengths of 380 nm, 410 nm and 700 nm were 1.0 or less, 0.5 or less and 0.3 or less, respectively. Further, in the polarizing plate durability test at 60 ° C. and 95% RH for 500 hours, both are in the range of −0.1 ≦ ΔCT ≦ 0.2 and −2.0 ≦ ΔP ≦ 0, and at −60 ° C. and 90% RH, −0.05 ≦ ΔCT ≦ 0.15 and −1.5 ≦ ΔP ≦ 0.

[Comparative Example 6]
In Example 4, polarizing plates (HB-H3BR) and (HB-H3BF) were produced using KH-H3 produced in Comparative Example 3 instead of the optical compensation film KH-2.

(Evaluation of reworkability)
The polarizing plates obtained in Examples 3 and 4 and Comparative Examples 4, 5, and 6 were bonded to the glass surface, and the reworkability was evaluated. Specifically, the polarizing plates obtained in Examples 3 and 4 and Comparative Examples 4, 5, and 6 are bonded together with an adhesive so that the optical compensation film is on the glass surface side, and is 50 ° C., 5 atm. Aging was performed for 6 hours.
After completion of aging, the polarizing plate was peeled off from the glass surface at 25 ° C. and 60% RH. The number of sheets remaining on the glass surface without being partly peeled off was examined. The results are shown in Table 1.

[Example 5]
(Preparation of bend alignment liquid crystal cell)
A polyimide film was provided as an alignment film on two glass substrates with ITO electrodes, and the alignment film was rubbed. The obtained two glass substrates were faced to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 4.5 μm. A liquid crystal compound having a Δn of 0.1396 (ZLI1132, manufactured by Merck & Co., Inc.) was injected into the cell gap to prepare a bend alignment liquid crystal cell. The size of the liquid crystal cell was 20 inches.
The polarizing plate (HB-1BF) prepared in Example 3 was attached to the viewing side and the polarizing plate (HB-1BR) was attached to the backlight side so as to sandwich the manufactured bend alignment cell. The optically anisotropic layer of the elliptically polarizing plate faces the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer facing the liquid crystal cell are arranged to be antiparallel.

  A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally white mode of 2V white display and 5V black display was set. Using the measurement ratio (EZ-Contrast 160D, manufactured by ELDIM) with the transmittance ratio (white display / black display) as the contrast ratio, the viewing angle can be adjusted in 8 steps from black display (L1) to white display (L8). It was measured. Further, the front contrast (CR: white display brightness / black display brightness) was obtained. The results are shown in Table 2.

(Evaluation of unevenness on the panel)
The liquid crystal display device of Example 5 was adjusted to a halftone on the entire surface, and unevenness was evaluated. No unevenness was observed from any direction.

[Example 6]
<Production of IPS mode liquid crystal cell>
As shown in FIG. 1, electrodes (2 and 3 in FIG. 1) are arranged on one glass substrate so that the distance between adjacent electrodes is 20 μm, and a polyimide film is used as an alignment film on it. A rubbing process was performed. The rubbing process was performed in the direction 4 shown in FIG. A polyimide film was provided on one surface of a separately prepared glass substrate, and a rubbing treatment was performed to obtain an alignment film. The two glass substrates are stacked and bonded so that the alignment films face each other, the distance between the substrates (gap; d) is 3.9 μm, and the rubbing directions of the two glass substrates are parallel. A nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.0769 and a dielectric anisotropy (Δε) of 4.5 was enclosed. The value of d · Δn of the liquid crystal layer was 300 nm.

(Production of liquid crystal display device)
A polarizing plate (HB-2BR) and a polarizing plate (HB-2BF) were attached so as to sandwich the produced cell. The polarizing plate (HB-2BF) is the viewing side.

Pasting is performed on one of the IPS mode liquid crystal cells prepared above so that the slow axis of the cellulose acylate film is parallel to the rubbing direction of the liquid crystal cell (that is, the slow axis of the cellulose acylate film is black). A polarizing plate was attached so that the rod-shaped compound layer was on the liquid crystal cell side (in parallel with the slow axis of the liquid crystal molecules of the liquid crystal cell during display).
Subsequently, the liquid crystal display device is attached to the other side of the IPS mode liquid crystal cell 1 so that the polarizing plate protective film 1 side is on the liquid crystal cell side and in a crossed Nicol arrangement with the polarizing plate 1. Produced. The leakage light of the liquid crystal display device thus manufactured was measured.
Light leakage when observed from the left oblique direction of 60 ° was 0.1% or less.
Incidentally, the leakage light without using the optical compensation film was 0.6%.

Further, the viewing angle characteristics in a state of being left at 25 ° C. 80% RH and 25 ° C. 10% RH for one week were investigated.
The results are shown in Table 3.

It is the schematic which shows the pixel area example of the liquid crystal display device of this invention. It is the schematic which shows an example of the liquid crystal display device of this invention. It is the schematic which shows the other example of the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal element pixel area 2 Pixel electrode 3 Display electrode 4 Rubbing direction 5a, 5b Director of liquid crystalline compound at the time of black display 6a, 6b Director of liquid crystalline compound at the time of white display 7a, 7b, 19a, 19b For polarizing film Protective film 8, 20 Polarizing film 9, 21 Polarization transmission axis 10 of polarizing film First retardation region 11 Slow axis 12 of first retardation region Second retardation region 13, 17 Cell substrate 14, 18 Cell substrate rubbing direction 15 Liquid crystal layer 16 Slow axis direction of liquid crystal layer

Claims (6)

Applying a coating liquid containing a polymerizable liquid crystal compound on the surface of the support or on the support to form a liquid crystal compound layer;
Simultaneously or after drying the liquid crystal compound layer, orienting the liquid crystal compound at a temperature equal to or higher than the liquid crystal transition temperature, and fixing the orientation to form an optically anisotropic layer; and Heating the optically anisotropic layer after fixing the orientation;
A method for producing an optical compensation film having
A method for producing an optical compensation film, wherein the heating temperature in the step of heating the optically anisotropic layer is 40 ° C. to 150 ° C., and the heating time is 5 seconds to 3000 seconds.   An optical compensation film comprising a support and an optically anisotropic layer formed using a polymerizable liquid crystal compound on the support, wherein the optical compensation film is manufactured by the manufacturing method according to claim 1. Optical compensation film.   The optical compensation film according to claim 2, wherein the polymerizable liquid crystal compound is a discotic liquid crystal compound having a polymerizable group.   A polarizing plate comprising the optical compensation film according to claim 2 or 3 and a polarizing film.   A liquid crystal display device comprising the optical compensation film according to claim 2 or 3 or the polarizing plate according to claim 4.   6. The liquid crystal display device according to claim 5, wherein the display method is an OCB method.

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