JP2007279271A - Optical compensation sheet, polarizing plate having optical compensation sheet, and liquid crystal display device - Google Patents

Abstract

（式中、Ｒ¹、Ｒ²、及びＲ³はそれぞれ独立に、水素、アルキル基またはアリール基を表すか、または、Ｒ¹、Ｒ²、及びＲ³のうちの２つが結合して、飽和またはオレフィン性不飽和の環を形成してもよい。）
The liquid crystal can be fixed even when the amount of photopolymerization initiator used is reduced and the exposure amount is low, and the alignment order of the liquid crystal is large, and the adhesion between the alignment film and the optically anisotropic layer is ensured. Provision of optical compensation sheets.
Optical anisotropy formed from a liquid crystalline composition comprising a liquid crystalline compound having two or more enol ether groups represented by the following general formula (I) and a photoacid generator on a transparent support: Compensation sheet having a conductive layer.

(Wherein R ¹ , R ² and R ³ each independently represent hydrogen, an alkyl group or an aryl group, or ^{two of} R ¹ , R ² and R ³ are bonded to form a saturated Or an olefinically unsaturated ring may be formed.)

Description

  The present invention relates to an optical compensation sheet having an optically anisotropic layer containing a cationically polymerizable liquid crystalline compound fixed using a photoacid generator, a polarizing plate having the optical compensation sheet, and a liquid crystal display device.

  The liquid crystal display device includes a liquid crystal cell, a polarizing element, and an optical compensation sheet (retardation plate). In a transmissive liquid crystal display device, two polarizing elements are attached to both sides of a liquid crystal cell, and at least one optical compensation sheet is disposed between the liquid crystal cell and the polarizing element. In a reflective liquid crystal display device, a reflector, a liquid crystal cell, at least one optical compensation sheet, and one polarizing element are arranged in this order. The liquid crystal cell includes a rod-like liquid crystalline compound, two substrates for encapsulating the rod-like liquid crystalline compound, and an electrode layer for applying a voltage to the rod-like liquid crystalline compound. The liquid crystal cell is different in the alignment state of the rod-like liquid crystal compound. As for the transmission type, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory B) Various display modes such as Super Twisted Nematic (VA), Vertically Aligned (VA), and reflection type, such as HAN (Hybrid Aligned Nematic), have been proposed.

Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and to widen the viewing angle. As an optical compensation sheet, a stretched polymer film has been conventionally used. However, in recent years, a liquid crystalline composition containing a liquid crystalline compound is applied on a transparent support instead of an optical compensation sheet made of a stretched polymer film. It has been proposed to use an optical compensation sheet having an optically anisotropic layer. Since liquid crystal compounds have various alignment forms, it has become possible to realize optical properties that cannot be obtained with conventional stretched polymer films by using liquid crystal compounds. As an optical compensation sheet using a liquid crystal compound, ones corresponding to various display modes of a liquid crystal cell have already been proposed. For example, Patent Documents 1 to 4 describe optical compensation sheets for TN mode liquid crystal cells. Patent Document 5 describes an optical compensation sheet for liquid crystal cells in IPS mode or FLC mode. Further, Patent Documents 6 and 7 describe optical compensation sheets for liquid crystal cells in OCB mode or HAN mode. Furthermore, an optical compensation sheet for an STN mode liquid crystal cell is described in Patent Document 8. A VA mode liquid crystal cell optical compensation sheet is described in Patent Document 9.
JP-A-6-214116 US Pat. No. 5,583,679 US Pat. No. 5,646,703 German Patent Application Publication No. 3911620 Japanese Patent Laid-Open No. 10-54982 US Pat. No. 5,805,253 International Publication No. 96/37804 Pamphlet JP-A-9-26572 Japanese Patent No. 2866372

An optical compensation sheet comprising an optically anisotropic layer made of a liquid crystalline composition can be usually produced by providing an optically anisotropic layer containing an alignment film and a liquid crystalline compound on a transparent support. As a manufacturing method thereof, a solution containing at least a liquid crystal compound and a photopolymerization initiator is usually applied onto an alignment film, dried, and the liquid crystal compound is aligned at a relatively high temperature, and then UV light (ultraviolet light) is applied. In general, a method in which a liquid crystalline compound is radically polymerized in air to cure an optically anisotropic layer is generally performed. In this method in which radicals generated by UV light are likely to receive the effect of inhibiting the polymerization of oxygen, it is necessary to contain a large amount of photopolymerization initiator and to irradiate with strong UV light in order to reliably fix the liquid crystal compound. When the amount of the photopolymerization initiator is small or when a sufficient amount of irradiation light cannot be ensured due to high-speed coating or the like, the liquid crystal is not sufficiently fixed, and a desired optical compensation sheet cannot be obtained. In addition, fixing liquid crystals by radical photopolymerization has the advantage of being highly versatile and can be applied to a wide range of existing technologies. However, there is a problem that the degree of orientation of the liquid crystals tends to be lowered due to volume shrinkage as the essence of the reaction. It was. Furthermore, if the photopolymerization reaction is insufficient, the adhesion between the alignment film and the optically anisotropic layer becomes insufficient, causing delamination in the bonding process with the polarizing film and the bonding process with the liquid crystal cell. Therefore, improvement was desired.
Accordingly, the first object of the present invention is to reduce the amount of photopolymerization initiator used to enable high-speed production at low cost, and optical anisotropy capable of fixing liquid crystal even at a low exposure amount. Is to provide a sheet. A second problem is to provide an optically anisotropic layer having a high degree of alignment order of liquid crystals. The third problem of the present invention is to secure the adhesion between the alignment film and the optically anisotropic layer and improve the yield of this step.

  In order to solve the above problems, the present inventor conducted various studies on the technique for fixing an optically anisotropic layer, and as a result, introduced an enol ether group having cationic polymerization property into a part of the structure of the liquid crystalline compound. It has been found that the above-mentioned problems can be solved by using this liquid crystalline compound and a photoacid generator in combination.

（式中、Ｒ¹、Ｒ²、およびＲ³はそれぞれ独立に、水素、アルキル基またはアリール基を表すか、または、Ｒ¹、Ｒ²、及びＲ³のうちの２つが結合して、飽和またはオレフィン性不飽和の環を形成してもよい。） That is, the present invention provides the following [1] to [6].
[1] Optical anisotropy formed on a transparent support from a liquid crystalline composition containing a liquid crystalline compound having two or more enol ether groups represented by the following general formula (I) and a photoacid generator An optical compensation sheet having a layer.

(Wherein R ¹ , R ² , and R ³ each independently represents hydrogen, an alkyl group, or an aryl group, or ^{two of} R ¹ , R ² , and R ³ are bonded to form a saturated Or an olefinically unsaturated ring may be formed.)

[2] The content of the photoacid generator in the liquid crystal composition is 0.1% by mass to 10% by mass with respect to the total mass of the liquid crystal compound having two or more enol ether groups. 1].
[3] The optical compensation sheet according to [1] or [2], which includes an alignment film between the transparent support and the optically anisotropic layer.
[4] The optical compensation sheet according to any one of [1] to [3], wherein the transparent support is a cellulose acylate film.
[5] A polarizing plate having the optical compensation sheet according to any one of [1] to [4].
[6] A liquid crystal display device having the polarizing plate according to [5].

  The optical compensatory sheet of the present invention is an optical compensatory sheet in which a liquid crystalline compound is fixed by utilizing photocationic polymerization that does not inhibit the polymerization of oxygen in the air, so that a small amount of photopolymerization initiator is necessary for production. Therefore, low-cost production is possible, and high-speed production is also possible. Also, unlike an optical compensation sheet having an optically anisotropic layer formed by radical polymerization reaction, an optical compensation sheet having an optically anisotropic layer having a high degree of orientational order of liquid crystals is produced because the volume shrinkage is not large. Is possible.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at a wavelength λ, respectively. Re (λ) is measured by making light with a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotating axis) (if there is no slow axis, any in-plane The light is incident at a wavelength of λ nm from the tilted direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction of KOBRA 21ADH or WR calculates based on the measured retardation value, the assumed average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing the sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the case where there is no slow axis, the arbitrary direction in the film plane is the rotation axis), Rth can also be calculated from the following formula (1) and formula (2) based on the value, the assumed value of the average refractive index, and the input film thickness value.

Note:
The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In formula (1), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. .

Rth = ((nx + ny) / 2-nz) xd --- Formula (2)

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optic axis, Rth (λ) is calculated by the following method.

Rth (λ) is from −50 degrees to +50 degrees with respect to the normal direction of the film, with Re (λ) as the slow axis (indicated by KOBRA 21ADH or WR) in the plane and the tilt axis (rotation axis). Measured at 11 points with light of wavelength λ nm from each inclined direction in 10 degree steps, and KOBRA 21ADH or based on the measured retardation value, average refractive index assumption and input film thickness value Calculated by WR.
In the above measurement, the assumed value of the average refractive index may be the value in the polymer handbook (JOHN WILEY & SONS, INC) and various optical film catalogs. 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). By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz.

  In the present specification, the degree of orientation order (hereinafter sometimes referred to as S) is used as a use indicating the degree of orientation of a polymer film and the degree of liquid crystal orientation, and is defined in the range of 0 ≦ S ≦ 1. If S = 0, a completely random state such as a liquid state is indicated. If S = 1, there is no molecular fluctuation like a crystal, and the film is perfectly oriented in one direction. In general, the orientation degree of the crystalline polymer film is measured by an X-ray diffraction pattern. However, when a film having nematic liquid crystallinity is measured, this method is not preferable as a measuring method because the sensitivity is low. The degree of orientation in this specification is measured by “Nanofinder” manufactured by Tokyo Instruments Co., Ltd. with an excitation laser wavelength of 532 nm, an excitation laser output of about 400 uW at the sample portion, and a depolarizer attached in front of the spectrometer. went. The measuring method cut | disconnected the film diagonally at about 1-2 degree | times, and performed the polarization Raman measurement of the surface or interface vicinity among the liquid-crystal material layers in a film. Rotate the film, change the angle between the orientation of the film surface and the electric field direction of the incident laser polarization, and measure at several angles. Of the scattered light components, the polarization component I parallel to the incident laser polarization electric field I parallel and perpendicular Each polarized component I perpendicular was detected spectroscopically using an analyzer. Furthermore, a fitting analysis based on the least square method was performed on the band having a peak derived from the skeleton of the liquid crystalline compound by using a theoretically derived equation with the alignment order parameters P2 and P4 as parameters, and the degree of alignment order was obtained.

  The optical compensation sheet of the present invention has a configuration in which an optically anisotropic layer containing a liquid crystalline compound is provided on a transparent support, and an alignment film may be further provided between the transparent support and the optically anisotropic layer. preferable. When providing a plurality of optically anisotropic layers, an alignment film may be provided on the optically anisotropic layer. In addition, an undercoat layer may be provided between the transparent support and the alignment film, and a protective film may be provided on the optically anisotropic layer for the purpose of surface protection. The optically anisotropic layer is composed mainly of a liquid crystalline compound that exhibits optical anisotropy, a polymer binder, and a photoacid generator, but if necessary, a monomer, a surfactant, an alignment temperature lowering agent, An additive such as a chiral agent may be added. The thickness of the optically anisotropic layer is preferably 0.5 to 100 μm, and more preferably 0.5 to 30 μm.

[Liquid crystal compounds]
In the optical compensation sheet of the present invention, an optically anisotropic layer is formed from a liquid crystalline composition containing a liquid crystalline compound having two or more enol ether groups represented by the following general formula (I).

式中、Ｒ¹、Ｒ²、およびＲ³はそれぞれ独立に、水素、アルキル基またはアリール基を表すか、または、Ｒ¹、Ｒ²、及びＲ³のうちの２つが結合して、飽和またはオレフィン性不飽和の環を形成してもよい。

In the formula, each of R ¹ , R ² , and R ³ independently represents hydrogen, an alkyl group, or an aryl group, or ^{two of} R ¹ , R ² , and R ³ are bonded to be saturated or An olefinically unsaturated ring may be formed.

As an alkyl group, Preferably it is C1-C20, More preferably, it is C1-C12, Most preferably, a C1-C8 alkyl group is mentioned, For example, a methyl group, an ethyl group, isopropyl group, tert- A butyl group, n-octyl group, n-decyl group, n-hexadecyl group, cyclopropyl group, cyclopentyl group, cyclohexyl group and the like can be mentioned.
The aryl group is preferably an aryl group having 6 to 30 carbon atoms, and examples thereof include a phenyl group and a naphthyl group.
Examples of the saturated or olefinically unsaturated ring formed by combining two of R ¹ , R ² , and R ³ include a cyclohexene ring and a cyclopentene ring.
Specific examples of the liquid crystalline compound having two or more enol ether groups represented by the following general formula (I) include two or more of n polymerizable groups (P) of the formula (II) described later, preferably n Examples include compounds in which all the polymerizable groups (P) are enol ether groups represented by the following general formula (I).

As the liquid crystal compound, a rod-like liquid crystal compound or a discotic liquid crystal compound is preferable.
Examples of rod-like liquid crystalline compounds 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. These rod-like liquid crystalline compounds are fixed by introducing a polymerizable group into the terminal structure of the rod-like liquid crystalline compound (similar to the disk-like liquid crystal described later) and utilizing this polymerization / curing reaction. Moreover, not only the above-mentioned low molecular liquid crystalline compound but also a high molecular liquid crystalline compound can be used. The high molecular liquid crystalline compound is a polymer having a side chain corresponding to the above low molecular liquid crystalline compound. An optical compensation sheet using a polymer liquid crystalline compound is described in JP-A-5-53016.

Regarding discotic liquid crystalline compounds, various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by the Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J. Chem. Am. Chem. Soc., Vol. 116, page 2655 (1994)). The polymerization of discotic liquid crystalline compounds is described in JP-A-8-27284.
In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline 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. Therefore, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula (II).

(II) D (-LP) n
Where D is a discotic core; L is a divalent linking group; P is a polymerizable group; and n is an integer from 4 to 12.
An example of the disk-shaped core (D) is shown below. In each of the following examples, LP (or PL) means a combination of a divalent linking group (L) and a polymerizable group (P).

In the formula (II), 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 number of carbon atoms in the arylene group is preferably 6-10.
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 (P). 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-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L10: -NH-AL-O-CO-
L11: -O-AL-
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-
L22: -S-AL-O-CO-
L23: -S-AL-S-AL-
L24: -S-AR-AL-

  The polymerizable group (P) of the general formula (II) is preferably an enol ether group represented by the above general formula (I), and examples of the other polymerizable group (P) include the following examples. .

In formula (II), 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 P may differ, it is preferable that it is the same. Moreover, it is preferable that all P is an enol ether group shown by the said general formula (I). The liquid crystalline compound is used in the range of 50% by mass to 99.9% by mass with respect to the total amount of the optically anisotropic layer, the preferable range is 70% by mass to 99.9% by mass, and the more preferable range is 80%. It is mass%-99.5 mass%.
Further, 50% by mass or more, preferably 70% by mass or more of the liquid crystalline compound used for forming the optically anisotropic layer of the optical compensation sheet of the present invention contains two or more enol ether groups represented by the general formula (I). The liquid crystal compound is preferably a liquid crystal compound, and the total amount of the liquid crystal compound used for forming the optically anisotropic layer of the optical compensation sheet of the present invention is a liquid crystal having two or more enol ether groups represented by the general formula (I) It is more preferable that it is an ionic compound.

[Polymer binder]
The polymer binder is used for the purpose of adjusting the layer transition temperature of the liquid crystal layer, adjusting the optical properties, improving the coating property, and the like. Specific polymer compounds include, for example, polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene, vinyl toluene copolymer, chlorosulfonated. Polyethylene, nitrocellulose, cellulose esters, polyvinyl chloride, chlorinated polyethylene, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, silicone polymer, fluorine-containing Polymers. As these polymer compounds, those that do not affect the optical characteristics are easy to use, but those that affect the optical characteristics can also be positively used as a material for adjusting the optical characteristics. JP-A-8-50206 reports that a cellulose ester is suitable for adjusting the tilt angle of a discotic liquid crystalline compound and obtaining desired optical characteristics. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate petitate. The degree of butyrylation of cellulose acetate butyrate is preferably in the range of 30% to 80% and the degree of acetylation is preferably in the range of 30 to 80%. These polymer compounds are used in the range of 0.1 to 30% by mass, preferably 0.1 to 10% by mass, based on the total amount of the optically anisotropic layer.

[Photoacid generator]
The optical compensation sheet of the present invention uses, as a photopolymerization initiator for forming an optically anisotropic layer, a photoacid generator that decomposes upon irradiation with actinic rays and generates an acid. The photoacid generator includes a photoinitiator for photocationic polymerization, a photoinitiator for photoradical polymerization, a photodecoloring agent for dyes, a photochromic agent, or light that is used in known microresists. The resulting compounds and mixtures thereof can be appropriately selected and used. For example, diazonium salts, ammonium salts, phosphonium salts, iodonium salts, sulfonium salts, onium salts such as arsonium salts described in JP-A-6-148889, organic halogen compounds, organic metal / organic halides, o-nitrosobenzyl type A photoacid generator having a protecting group, a compound that generates sulfonic acid by photolysis represented by iminosulfonates, a disulfone compound and a group that generates these acids, or a compound that is a main chain or a side chain of a polymer It can be used by selecting from the compounds introduced in the above.
Among these, as the acid generator, those having a photosensitive region in the range of 330 nm to 450 nm and being decomposed by 30% or more with an energy amount of 100 mJ / cm ² are preferable. However, the present invention is not limited to this.

These photoacid generators are preferably 0.1% by mass to 10% by mass with respect to the total mass of the liquid crystal compound having two or more enol ether groups.
[Other additives]
In addition to the above components, the optically anisotropic layer includes components such as a plasticizer, a polysynthetic monomer, and a chiral agent as required for adjusting optical properties, ensuring flexibility of the coating, and supporting roles for polymerization and curing reactions. May be added. Among these, polymerizable monomers are used relatively frequently. The polymerizable monomer is a compound having a vinyl group, a vinyloxy group, an acryloyl group, a methacryloyl group, an allyl group or the like in the molecule, and is generally 1 to 50% by mass, preferably 5 to 30% by mass with respect to the liquid crystalline compound. Used in.

[Preparation of optically anisotropic layer]
The optically anisotropic layer is formed by applying a liquid crystalline composition containing the above components onto an alignment film described later, aligning it at a liquid crystal phase-solid phase transition temperature or lower, and then fixing the liquid crystalline compound by UV irradiation. To form. The liquid crystal composition can be applied by a known method (eg, bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).
As the photoreaction of the liquid crystalline compound, a photocationic polymerization reaction is performed. Irradiation for polymerizing the liquid crystalline compound is preferably performed using ultraviolet light, radiation energy is preferably 20~5000mJ / cm ^2, further preferably 100 to 800 mJ / cm ^2.
In order to accelerate the photocationic polymerization reaction, light irradiation may be performed under heating conditions.

[Alignment film]
The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). The alignment film in the optical compensation sheet of the present invention is preferably made of an organic compound having a polymerizable group. Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. The type of polymer used for the alignment film is determined according to the type of display mode of the liquid crystal cell. In a display mode (eg, VA, OCB, HAN) in which many rod-like liquid crystalline molecules in the liquid crystal cell are oriented substantially vertically (the director is parallel to the normal direction of the transparent support surface), the optically different characteristics are obtained. An alignment film having a function of aligning liquid crystal molecules of the isotropic layer substantially horizontally (in the case of discotic liquid crystal molecules, the director is parallel to the normal direction of the transparent support surface) is used. In a display mode in which many rod-like liquid crystal molecules in the liquid crystal cell are aligned substantially horizontally (eg, STN), the liquid crystal molecules of the optically anisotropic layer have a function of being substantially vertically aligned. An alignment film is used. In a display mode in which many rod-like liquid crystalline molecules in the liquid crystal cell are substantially obliquely aligned (eg, TN), the liquid crystalline molecules of the optically anisotropic layer have a function of substantially obliquely aligning. An alignment film is used.

Specific types of organic compounds used for the alignment film in the optical compensation sheet of the present invention are described in the literature on optical compensation sheets using liquid crystal molecules corresponding to the display mode of the liquid crystal cell. By introducing a crosslinkable group into the organic compound used for the alignment film and reacting the crosslinkable group, the strength of the alignment film can be increased and the adhesion between the layers can be improved. In addition, about the superposition | polymerization of the organic compound used for alignment film, Unexamined-Japanese-Patent No. 8-338913 has description. The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm. Examples of the organic compound used for the alignment film in the optical compensation sheet of the present invention include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, poly ( N-methylolacrylamide), styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer And polymers such as carboxymethylcellulose, polyethylene, polypropylene and polycarbonate, and compounds such as silane coupling agents.
Furthermore, examples of a polymer preferable as an organic compound used for the alignment film in the optical compensation sheet of the present invention include water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol. Of these, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are preferable, and polyvinyl alcohol and modified polyvinyl alcohol are particularly preferable.

Examples of the polyvinyl alcohol include those having a saponification degree of 70 to 100%, generally those having a saponification degree of 80 to 100%, and more preferably those having a saponification degree of 85 to 95%. 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 or the like is introduced as a modifying group), modified by block polymerization (for example, COOH as a modifying group) , 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.

[Transparent support]
As the transparent support of the optical compensation sheet, a polymer film with controlled optical anisotropy can be preferably used. That the support is transparent means that the light transmittance is 80% or more.
As a material for forming the transparent support, cellulose ester, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, and norbornene resin are used, and optical anisotropy is obtained by stretching the polymer film. In addition, a cellulose ester film having high optical anisotropy can be produced by adding a retardation increasing agent (described in the specification of European Patent Application No. 0911656) to the cellulose ester film. As the transparent support in the optical compensation sheet of the present invention, a cellulose acylate film is particularly preferable.

  The cellulose ester or synthetic polymer film is preferably formed by a solvent casting method. The thickness of the transparent support is preferably 20 to 500 μm, and more preferably 50 to 200 μm. In order to improve the adhesion between the transparent support and the layer (adhesive layer, alignment film or optically anisotropic layer) provided thereon, surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet ( UV) treatment, flame treatment, saponification treatment) may be carried out, and an adhesive layer (undercoat layer) may be provided on the transparent support.

[Protective film]
The protective film is provided for the purpose of protecting the surface of the optically anisotropic layer and improving smoothness. The compound to be used is not particularly limited, but a polymer compound that is soluble in a solvent that does not dissolve the optically anisotropic layer and has a film forming ability is preferable. Specific examples include water-soluble polymers such as gelatin, methyl cellulose, alginic acid, pectin gum arabic, pullulan, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid amide, polyvinyl benzene sulfonic acid soda, carrageenan, and polyethylene glycol.
[Liquid Crystal Display]
The optical compensatory sheet of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensated HN), STN (Superied A Quantitative V). It can be used for liquid crystal display devices in various display modes such as (Hybrid Aligned Nematic). The liquid crystal display device includes a liquid crystal cell and a polarizing plate. A polarizing plate consists of a protective film, a polarizing film, and an optical compensation sheet (retardation plate). Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally manufactured using a polyvinyl alcohol film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. The protective film can be provided on both surfaces of the polarizing film, and the transparent support of the optical compensation sheet can also function as a protective film on one side of the polarizing film. As the protective film on the other side, a cellulose ester film having high optical isotropy is preferably used.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Comparative Example 1]
(Preparation of transparent 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 having 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 band casting machine. After the film surface temperature on the band reached 40 ° C., the film was dried for 1 minute, peeled off, and then dried using a cellulose acetate film (CA-1) (thickness of 0.3% by mass of residual solvent). 109 μm) was produced.
When the retardation of the produced cellulose acetate film (CA-1) was measured by KOBRA 21ADH (measurement wavelength 589 nm, manufactured by Oji Scientific Instruments), the retardation Rth in the thickness direction was 85 nm, and the in-plane retardation Re was 7 nm. Met.

(Saponification and alignment film formation)
A cellulose acetate film (CA-1) is passed through a dielectric heating roll having a temperature of 60 ° C. and heated to a film surface temperature of 40 ° C., and then an alkali solution (S-1) having the composition shown below is attached to a rod coater. It was applied at a coating amount of 15 cc / m ² and heated at 110 ° C. for 15 seconds under a steam far infrared heater manufactured by Noritake Co., Ltd. 3 cc / m ^{2 was} applied. The film temperature at this time was 40 degreeC. Next, washing with a fountain coater and draining with an air knife were repeated three times, and then the film was retained in a drying zone at 70 ° C. for 5 seconds and dried.
<Alkaline solution (S-1) composition>
Potassium hydroxide 8.55% by mass
23.235% by weight of water
Isopropanol 54.20% by mass
Surfactant (K-1: C ₁₄ H ₂₉ O (CH ₂ CH ₂ O) ₂₀ H)
1.0% by mass
Propylene glycol 13.0% by mass
Antifoaming agent Surfinol DF110D (manufactured by Nissin Chemical Industry Co., Ltd.)
0.015% by mass
On this surface-treated film, an alignment film coating solution having the following composition was coated with a load coater at a coating amount of 283 l / m ² . Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds.
<Alignment film coating solution>
20% by mass of the following modified polyvinyl alcohol
360% by weight of water
Methanol 120% by mass
Glutaraldehyde 0.5% by mass

  Next, rubbing treatment was performed in the longitudinal direction of the surface on which the alignment film was formed.

(Formation of optically anisotropic layer)
A discotic liquid crystal coating solution (DAH-1: solid content concentration 32.6%; MEK solvent) having the following composition was heated in a thermostatic bath at 130 ° C. for 3 minutes using a # 3.2 wire bar coater. After aligning the discotic liquid crystalline molecules, UV was irradiated at 500 mJ / cm ² using a high-pressure mercury lamp and allowed to cool to room temperature to prepare an optical compensation sheet (KSH-1).
<Discotic liquid crystal coating solution (DAH-1)>
9.1 parts by mass of the following discotic liquid crystal DLC-A ethylene oxide-modified trimethylolpropane acrylate
(V # 360, Osaka Organic Chemical Co., Ltd.) 0.9 parts by weight Cellulose acetate butyrate 0.2 parts by weight
(CAB551-0.2 Eastman Chemical)
Cellulose acetate butyrate 0.05 parts by mass
(CAB531-1 Eastman Chemical)
Irgacure 907 (manufactured by Ciba-Geigy) 0.3 parts by mass Kayacure DETX (manufactured by Nippon Kayaku Co., Ltd.) 0.1 parts by mass Fluorosurfactant Megafac M-1176 (manufactured by DIC): 0.02 parts by mass Methyl ethyl ketone 21.95 parts by mass

[Examples 1 to 8]
(Preparation of transparent support)
A cellulose acetate film (CA-1) was produced in the same manner as in Comparative Example 1.
(Saponification and alignment film formation)
In the same manner as in Comparative Example 1, the cellulose acetate film (CA-1) was saponified to form an alignment film and rubbed.
(Formation of optically anisotropic layer)
Irgacure 907 and Kayacure DETX, which are photopolymerization initiators (radical polymerization initiators) of the discotic liquid crystal coating liquid (DAH-1) of Comparative Example 1, were replaced with the photoacid generators listed in Table 1, and further DLC. A coating liquid (DA-1 to 8) was prepared by replacing -A with the discotic liquid crystal shown in Table 1. Coating conditions and drying conditions were the same as in Comparative Example 1, and optical compensation sheets (KS-1 to 8) were produced.

[Comparative Example 2]
(Preparation of transparent 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 having 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 above-mentioned 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 band casting machine. After the film surface temperature on the band reached 40 ° C., the film was dried for 1 minute, peeled off, stretched in the width direction in a dry air, and a cellulose acetate film having a residual solvent amount of 0.3 mass% (CA -2) (thickness 88 μm) was produced.
When the retardation of the produced cellulose acetate film (CA-2) was measured, the retardation Rth in the thickness direction was 175 nm, and the in-plane retardation Re was 36 nm.
(Saponification and alignment film formation)
The same treatment as in Comparative Example 1 was performed.

(Formation of optically anisotropic layer)
A discotic liquid crystal coating solution (DAH-2) having the following composition: solid content concentration of 35.5%; MEK solvent) is used in a thermostatic bath at the temperature shown in Table 1 using a # 3.2 wire bar coater. Was heated for 3 minutes to orient the discotic liquid crystalline molecules, and then irradiated with 300 mJ / cm 2 of UV using a high-pressure mercury lamp, and allowed to cool to room temperature, to produce an optical compensation sheet (KSH-2).
<Discotic liquid crystal coating solution (DAH-2)>
9.1 parts by mass of the above discotic liquid crystal DLC-A ethylene oxide modified trimethylolpropane acrylate
(V # 360, Osaka Organic Chemical Co., Ltd.) 0.9 parts by weight Cellulose acetate butyrate 0.15 parts by weight
(CAB531-1 Eastman Chemical)
Irgacure 907 (manufactured by Ciba-Geigy) 0.3 parts by mass Kayacure DETX (manufactured by Nippon Kayaku Co., Ltd.) 0.1 parts by mass Fluorosurfactant Megafac M-1176 (manufactured by DIC): 0.02 parts by mass Methyl ethyl ketone 19.03 parts by mass

[Examples 9 to 11]
(Preparation of transparent support)
A cellulose acetate film (CA-2) was produced in the same manner as in Comparative Example 2.
(Saponification and alignment film formation)
In the same manner as in Comparative Example 2, the cellulose acetate film (CA-2) was saponified to form an alignment film and rubbed.
(Formation of optically anisotropic layer)
Irgacure 907 and Kayacure DETX, which are photopolymerization initiators of the discotic liquid crystal coating solution (DAH-2) of Comparative Example 1, were replaced with the photoacid generators listed in Table 1, and further DLC-A was converted to Table 1. It replaced with the discotic liquid crystal of description, and produced the coating liquid (DA-9-11). Coating conditions and drying conditions used the same method as in Comparative Example 1, and optical compensation sheets (KS-9 to 11) were produced.

[Comparative Example 3]
(Preparation of transparent support)
A cellulose acetate film (CA-2) was produced in the same manner as in Comparative Example 2.
(Saponification and alignment film formation)
The cellulose acetate film (CA-2) was saponified by the same method as in Comparative Example 2 to form an alignment film (no rubbing).
(Formation of optically anisotropic layer)
A rod-shaped liquid crystal coating solution (DAH-3 to 4) having the following composition is heated at the temperature shown in Table 1 for 2 minutes to orient the rod-shaped liquid crystal compound, and then irradiated with UV at 500 mJ / cm ² using a high-pressure mercury lamp. The product was allowed to cool to prepare an optical compensation sheet (KSH-3).
<Bar-shaped liquid crystal coating liquid (DA-11 to 13, DAH-3 to 4)>
9.1 parts by mass of the following rod-shaped liquid crystal BLC-A 0.5 parts by weight of the following F-containing binder BT-A 1.0 parts by weight of the following alignment accelerator HA-A 1.0 part by weight Irgacure 907 0.3 parts by mass Kayacure DETX (Japan) 0.1 parts by mass of Kayaku Co., Ltd.

[Examples 12 to 14]
(Preparation of transparent support)
A cellulose acetate film (CA-2) was produced in the same manner as in Comparative Example 2.
(Saponification and alignment film formation)
The cellulose acetate film (CA-2) was saponified by the same method as in Comparative Example 2 to form an alignment film. The rubbing treatment was not performed.
(Formation of optically anisotropic layer)
Irgacure 907 and Kayacure DETX, which are photopolymerization initiators of the discotic liquid crystal coating liquid (DAH-3) of Comparative Example 3, were replaced with the photoacid generators described in Table 1, and further BLC-A was converted to Table 1. A coating liquid (DA-12 to 14) was prepared by replacing the discotic liquid crystal described. Coating conditions and drying conditions used the same method as in Comparative Example 1, and optical compensation sheets (KS-12-14) were produced.

(Evaluation of orientation order of optically anisotropic layer)
The degree of orientation order was calculated using “Nanofinder” manufactured by Tokyo Instruments Co., Ltd. with reference to the method described on pages 651 to 654 of Proceedings of IDW'04, 651 (2004). The results are shown in Table 1.
(Measurement of polymerization degree of optically anisotropic layer)
The degree of polymerization of the optically anisotropic layer was measured using a 710 FT-IR SPECTROMETER manufactured by Nicolet. The reaction amount (degree of polymerization) was calculated from the peak derived from the acrylate group or vinyl ether group and the height of the peak derived from the aromatic ring. The results are shown in Table 1.

(Evaluation of peeling of optical compensation film)
The orientation of liquid crystals of the optical compensation films obtained in Examples 1 to 14 and Comparative Examples 1 to 5 and evaluation of peeling were evaluated. Orientation was evaluated by visual observation through a polarizing film and peeling evaluation (adhesion evaluation) of the optical compensation film in accordance with JIS K 5400 8.5.2 base tape method. However, polyester adhesive tape NO31RH manufactured by Nitto Denko was used for evaluation. If the effect of photopolymerization is insufficient, it is easy to peel off. Table 1 shows the results expressed in the residual ratio. 100% indicates no peeling, and 0% indicates a state of full peeling.

Comparing Examples 1 to 14 and Comparative Examples 1 to 3, all the examples of the present invention show high sensitivity even when the amount of the photoacid generator (photopolymerization initiator) is small, and the degree of orientation order and adhesion Is clearly superior.

Claims (6)

On a transparent support, it has an optically anisotropic layer formed from a liquid crystalline composition containing a liquid crystalline compound having two or more enol ether groups represented by the following general formula (I) and a photoacid generator Optical compensation sheet.

(Wherein R ¹ , R ² , and R ³ each independently represents hydrogen, an alkyl group, or an aryl group, or ^{two of} R ¹ , R ² , and R ³ are bonded to form a saturated Or an olefinically unsaturated ring may be formed.) The content of the photoacid generator in the liquid crystal composition is 0.1% by mass to 10% by mass with respect to the total mass of the liquid crystal compound having two or more enol ether groups. The optical compensation sheet as described. The optical compensation sheet according to claim 1, comprising an alignment film between the transparent support and the optically anisotropic layer. The optical compensation sheet according to claim 1, wherein the transparent support is a cellulose acylate film. The polarizing plate which has an optical compensation sheet as described in any one of Claims 1-4. A liquid crystal display device comprising the polarizing plate according to claim 5.