JP2007147966A - Optical compensation film, polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical compensation film which has satisfactory optical compensation ability and, moreover, has improved productivity. <P>SOLUTION: The optical compensation film has an optical anisotropic layer formed by curing a liquid crystalline composition which comprises at least a liquid crystalline compound having a polymerizable group and a polymerization initiator. Melting point T<SB>mp</SB>of the polymerization initiator and transition temperature T<SB>iso-lc</SB>of isotropic phase-nematic liquid crystal phase of the crystalline composition satisfy the following relation; relation 1 Δ=T<SB>mp</SB>-T<SB>iso-lc</SB>≥-30°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical compensation film having an optically anisotropic layer formed from a liquid crystalline composition, a polarizing plate including the optical compensation film, and a liquid crystal display device.

  A liquid crystal display device usually has a liquid crystal cell, a polarizing element, and an optical compensation sheet (retardation plate). In the transmissive liquid crystal display device, two polarizing elements are attached to both sides of the liquid crystal cell, and at least one optical compensation sheet is disposed between the liquid crystal cell and the polarizing element. Generally, a liquid crystal cell, at least one optical compensation sheet, and one polarizing element are arranged in this order. A liquid crystal cell is usually composed of a rod-like liquid crystalline substance, two substrates for enclosing it, and an electrode layer for applying a voltage to the rod-like liquid crystalline substance. The liquid crystal cell is different in the alignment state of the rod-like liquid crystalline substance. As for the transmission type, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optical Compensatory N) (OCB). 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 films are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As an optical compensation film, a stretched polymer film has been conventionally used. It has been proposed to use an optical compensation film having an optically anisotropic layer formed by applying a liquid crystalline composition containing a liquid crystalline substance on a transparent support instead of the optical compensation film made of a stretched polymer film. . There are various alignment forms for liquid crystal substances. By using a liquid crystalline substance, it has become possible to realize optical properties that cannot be obtained with conventional stretched polymer films. As an optical compensation film using a liquid crystal substance, 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 films for TN mode liquid crystal cells. Moreover, the optical compensation film for liquid crystal cells of IPS mode or FLC mode has description in patent document 5. FIG. Further, optical compensation films for liquid crystal cells in OCB mode or HAN mode are described in Patent Documents 6 and 7. Furthermore, an optical compensation film for an STN mode liquid crystal cell is described in Patent Document 8. A VA mode liquid crystal cell optical compensation film 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

The optical compensation film can be prepared by applying an alignment film and an optical anisotropic layer, which is a liquid crystal composition, on a transparent support, while the alignment film, the transparent support, the alignment film, and the alignment film are optically different. If the adhesion between the two layers is not sufficient, there is a problem that delamination occurs in the bonding process with the polarizing film and the bonding process with the liquid crystal cell. After the optical anisotropic layer is aged for a period of time necessary for the orientation of the liquid crystalline composition (that is, a temperature slightly lower than the transition temperature of the isotropic phase-nematic liquid crystal phase of the optical anisotropic layer before curing). Generally, it is formed by curing with light, heat, or both, but the problem that the adhesion between the alignment film and the optically anisotropic layer described above greatly fluctuates as the process conditions change. was there.
The present invention improves the productivity of an optical compensation film having a good optical compensation capability by improving the adhesion between the alignment film and the optical anisotropic layer, and attaches the optical compensation film to the polarizing film. The purpose is to make the bonding step and the bonding step with the liquid crystal cell easier than before, and to improve the productivity of the polarizing plate and the liquid crystal display device.

Means for solving the problems of the present invention are as follows.
[1] An optical compensation film having an optically anisotropic layer formed by curing a liquid crystalline composition containing at least a liquid crystalline compound having a polymerizable group and a polymerization initiator, and having a melting point T of the polymerization initiator An optical compensation film, wherein _mp and an isotropic phase-nematic liquid crystal phase transition temperature T _{iso-lc of the} liquid crystalline composition satisfy the following formula (1):
Formula (1): (DELTA) = _Tmp - _Tiso-lc > =-30 _degreeC .
[2] The melting point _Tmp of the polymerization initiator and the transition temperature _Tiso-lc of the isotropic phase-nematic liquid crystal phase of the liquid crystalline composition satisfy the following formula (1): Optical compensation film:
Formula (2): (DELTA) = _Tmp - _Tiso-lc > = 0 _degreeC .
[3] The optical compensation film according to [1] or [2], wherein the liquid crystalline compound is a discotic liquid crystal.
[4] The optical compensation film according to any one of [1] to [3], further comprising a support and an alignment film between the support and the optically anisotropic layer.
[5] The optical compensation film according to any one of [1] to [4], wherein the alignment film contains an organic compound having a polymerizable group.
[6] The optical compensation film according to any one of [1] to [5], wherein the transparent support is a cellulose acylate film.
[7] A polarizing plate having a transparent protective film, a polarizing film, and the optical compensation film of any one of [1] to [6].
[8] A TN liquid crystal display device having at least a TN liquid crystal cell and a polarizing plate of [7].
[9] A bend alignment mode type liquid crystal display device having at least a bend alignment mode liquid crystal cell and a polarizing plate of [7].
[10] at least contains a liquid crystalline compound and a polymerization initiator having a polymerizable group, an isotropic phase - liquid crystal composition transition temperature of a nematic liquid crystal phase is a T _iso-lc, 5 ℃ than T _iso-lc Maintaining the temperature at ˜50 ° C., aligning the molecules of the liquid crystalline compound, and irradiating the liquid crystalline composition with light to fix the molecules of the liquid crystalline compound in an aligned state, thereby optically anisotropic A melting point T _mp of the polymerization initiator and an isotropic phase-nematic liquid crystal phase transition temperature T _{iso-lc of the} liquid crystal composition satisfy the following formula (1): An optical compensation film manufacturing method:
Formula (1): (DELTA) = _Tmp - _Tiso-lc > =-30 _degreeC .
[11] An optical compensation film produced by the method of [10].

  According to the present invention, when forming an optically anisotropic layer from a liquid crystalline composition, it is possible to stably and satisfactorily maintain the adhesion between the alignment film and the optically anisotropic layer even if process factors fluctuate. became. As a result, the productivity of the optical compensation film having a good optical compensation capability is improved, and the bonding process between the optical compensation film and the polarizing film and the bonding process with the liquid crystal cell are made easier than before. Productivity of the liquid crystal display device can be improved.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail below. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
[Optical compensation film]
The optical compensation film of the present invention has an optically anisotropic layer formed from a liquid crystalline composition. One aspect of the optical compensation film of the present invention further includes a support that supports the optical anisotropic layer, and an alignment film between the support and the optical anisotropic layer.
First, the optical anisotropic layer included in the optical compensation film of the present invention will be described.
[Optically anisotropic layer]
In the present invention, the optically anisotropic layer is a layer formed by curing a liquid crystalline composition containing at least a liquid crystalline compound having a polymerizable group and a polymerization initiator. The liquid crystalline composition may be prepared as a liquid coating composition, and in such a case, a solvent is used. For example, the prepared coating composition is wet-coated on a roll film having an alignment film described later, and the solvent is dried by applying wind at a predetermined temperature and wind speed, and then cured by heat and / or light. Can be formed. The composition contains a liquid crystalline compound having a polymerizable group and a polymerization initiator as essential components, and further includes a polymerizable compound having no liquid crystallinity, a low molecule or a polymer for adjusting the alignment state of the liquid crystalline molecules. It is preferable to contain a leveling agent that reduces unevenness due to coating.

[Liquid Crystalline Composition]
The liquid crystalline composition used for forming the optically anisotropic layer must satisfy the following formula (1), and preferably satisfies the following formula (2).
Formula (1): (DELTA) = _Tmp - _Tiso-lc > =-30 _degreeC
Formula (2): Δ = T _mp −T _iso-lc ≧ 0 ° C.
Where T _mp is the melting point of the polymerization initiator and T _iso-lc is the transition temperature of the isotropic phase-nematic liquid crystal phase of the liquid crystal composition. The T _iso-lc of the liquid crystal composition is applied to the surface of a glass plate having a thickness of 1.0 mm so that the liquid crystal composition has a thickness of 1.5 μm to 2.0 μm. / Min) while observing with a polarizing microscope. As described above, the liquid crystalline composition may be prepared as a liquid coating composition. In such a case, after applying the liquid liquid crystalline composition to the surface of a glass plate or the like, the solvent is dried. From the above, the transition temperature of the isotropic phase-nematic liquid crystal phase obtained by the above method is used. In the present invention, by forming an optically anisotropic layer using the liquid crystalline composition satisfying the above formula (1), the temperature in the ripening step that promotes the alignment of the molecules of the liquid crystalline compound, during drying and during heating Even if various conditions such as the amount of hot air fluctuate, the curing of the liquid crystalline composition proceeds stably. As a result, defects such as peeling due to a decrease in adhesion between the optically anisotropic layer and its lower layer (usually an alignment film) can be reduced, and productivity can be improved.

[Liquid crystal compounds]
In the present invention, a liquid crystal compound having a polymerizable group is used. As the liquid crystal compound, a rod-like liquid crystal compound or a discotic liquid crystal compound is preferable, and a discotic liquid crystal compound is particularly 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. Not only the above low-molecular liquid crystalline compounds but also high-molecular liquid crystalline compounds 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 film produced using a polymer liquid crystalline compound is described in JP-A-5-53016.

The discotic compounds are disclosed in various literatures (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, Chemistry of Liquid Crystal). 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J. Am. Soc., Vol.116, page 2655 (1994)). The polymerization of discotic compound molecules is described in JP-A-8-27284.
In order to fix the discotic compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic 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 compound having a polymerizable group is preferably a compound represented by the following formula (3).

Formula (3) 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 (3), 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 linking in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO-, -NH-, -O-, and S- are combined. More preferably, it is a 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-
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 (P) of the formula (3) is determined according to the type of polymerization reaction. Examples of the polymerizable group (P) are shown below.

The polymerizable group (P) is preferably an unsaturated polymerizable group (P1, P2, P3, P7, P8, P15, P16, P17) or an epoxy group (P6, P18). More preferably, it is most preferably an ethylenically unsaturated polymerizable group (P1, P7, P8, P15, P16, P17).
In Formula (3), 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.

[Polymerization initiator]
The liquid crystal composition contains at least one polymerization initiator. The polymerization initiator used in the present invention is any of a photopolymerization initiator that generates radicals and the like by light irradiation, a thermal polymerization initiator that generates radicals and the like by supply of heat, and a polymerization initiator belonging to both. Also good. Of these, a photopolymerization initiator is preferred. In the present invention, the polymerization initiator is used in combination with the liquid crystallinity based on the relative relationship between the melting point (T _mp ) and the transition temperature (T _iso-lc ) of the isotropic phase-nematic liquid crystal phase of the liquid crystal composition. It is appropriately selected according to the type of compound and other additives.
Moreover, it is preferable to select a preferable one from the absorption spectrum of the photopolymerization initiator so that radicals are efficiently generated with respect to the emission spectrum of the ultraviolet lamp used for photopolymerization.

  Although the preferable range of the amount of the polymerization initiator used varies depending on the type of the polymerization initiator, etc., it is generally 0.01 to 20% by mass of the composition (solid content when prepared as a coating solution). It is preferable that it is 0.5-5 mass%.

As the photopolymerization initiator that can be used in the present invention, the following compounds or a mixture thereof can be used. When a mixture of two or more kinds of compounds is selected, the material may be selected so as to satisfy the above formula (1), where T _mp is the melting point of the component exceeding 50% by mass. When a mixture of three or more kinds of compounds is used and the content of a single component is less than 50% by mass, the melting points of all the compound types from the compound having a high content up to more than 50% by mass are within the scope of the present invention. You may choose so that it is within.

As described above, in the present invention, the polymerization initiator has a melting point (T _mp ) and an isotropic phase-nematic liquid crystal phase transition temperature (T _iso-lc ) satisfying the above relational expression. Thus, it is appropriately selected according to the type of liquid crystal compound used in combination. For example, as the polymerization initiator used together with the liquid crystalline compound represented by the following structural formula, the exemplified compound A-11, A-3 or B-4 is preferable. However, by using an additive such as a polyfunctional monomer in combination and adjusting the amount of addition, etc., other polymerization initiators and a liquid crystal compound having the following structure are used in combination, and the above relational expression is satisfied. Of course, it is also possible to prepare a liquid crystal composition.

[Other additives]
In order to assist curing, it is preferable to add a monofunctional or polyfunctional curable (polymerizable) compound to the liquid crystalline composition for forming the optically anisotropic layer of the present invention. The functional group of the curable (polymerizable) compound is preferably highly reactive with the functional group of the liquid crystal compound contained. For example, when the functional group of the liquid crystal compound is acrylate or methacrylate, a commercially available Monofunctional and polyfunctional (2-6 functional) acrylate monomers and methacrylate monomers (hereinafter collectively referred to as (meth) acrylate monomers), hexafunctional or higher oligomers, etc. are preferred, and highly reactive acrylate monomers are preferred, especially A polyfunctional monomer having two or more functional groups in one molecule is preferred.

  Specifically, esters of polyhydric alcohol and (meth) acrylic acid [for example, ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate, hexanediol di (meth) acrylate, 1,4-cyclohexane ( (Meth) diacrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipenta Erythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, pentaerythritol hexa (meth) acrylate, 1,2,3-cyclohexanetetramethacrylate Polyurethane polyacrylate, polyester polyacrylate], ethylene oxide-modified and caprolactone-modified products, etc. of said esters. Two or more of these monomers may be used in combination. Among the above, as described above, a tri- or higher functional (meth) acrylate monomer is preferable, and trimethylolpropane triacrylate, an ethylene oxide modified product of trimethylolpropane triacrylate, dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate. And a mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate are preferably used.

  Other additives preferably added to the liquid crystalline composition for forming the optically anisotropic layer of the present invention include fluorine-based and silicone-based leveling agents. The leveling agent is preferably used because it has an effect of reducing film thickness unevenness due to non-uniform drying in the step of volatilizing the solvent after applying the coating composition. In that case, since there is a thing which has a remarkable influence on the orientation of a liquid crystalline compound, it is necessary to select carefully.

An example of a method for producing the optical compensation film of the present invention is to apply a liquid crystalline coating composition containing at least a liquid crystalline compound having a polymerizable group, a polymerization initiator, and a solvent to the surface of an alignment film or the like. After heating and aging at a temperature to bring the molecules of the liquid crystalline compound into a predetermined alignment state, polymerization proceeds by light irradiation to fix the molecules of the liquid crystalline compound in such an alignment state to form an optically anisotropic layer It is a method to do.
The coating 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).

The heating / ripening temperature for the alignment of the liquid crystal compound is preferably performed for several minutes in a temperature range lower by about 5 ° C. to 50 ° C. than T _iso-lc . By heating and aging in such a temperature range, the molecules of the liquid crystalline compound can be stably brought into a desired alignment state, and the cured optically anisotropic layer and lower layer (generally an alignment film) Adhesion is further improved.

When the aligned liquid crystal compound molecules are fixed while maintaining the alignment state, the polymerization of the liquid crystal compound is preferably advanced by light irradiation, but the polymerization may be initiated only by heat. It is preferable to use ultraviolet rays for light irradiation. Irradiation energy is preferably 20~5000mJ / cm ^2, further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions, and light irradiation is performed while maintaining the aging temperature (preferably, a temperature range of about 5 ° C. to 50 ° C. lower than T _iso-lc ). It is preferable to do this.

The thickness of the optically anisotropic layer after curing is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and further preferably 0.3 to 10 μm.
A protective layer may be further provided on the optically anisotropic layer.

[Alignment film]
The optical compensation film of the present invention may have an 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). 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 display modes (eg, VA, OCB, HAN) in which many of the rod-like liquid crystalline molecules in the liquid crystal cell are oriented substantially perpendicularly (the director is parallel to the normal direction of the transparent support surface) An alignment film having a function of aligning the liquid crystal molecules of the 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 polymer types are described in the literature on optical compensation films using liquid crystalline molecules corresponding to the display mode of the liquid crystal cell. When an organic compound (preferably a polymer) having a crosslinkable group (polymerizable group) is used as a material for the alignment film, the strength of the alignment film is improved by the reaction of the crosslinkable group during the formation of the alignment film, and the alignment film and the optical film are optically aligned. It is possible to further improve the adhesion between the anisotropic layer and the interlayer. In addition, about the superposition | polymerization of the organic compound used for alignment film, Unexamined-Japanese-Patent No. 8-338913 has description.
Examples of polymers that can be used for the alignment film forming material include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, and poly (N-methylolacrylamide). , Styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene , Polymers such as polypropylene and polycarbonate, and compounds such as silane coupling agents.
Examples of preferred polymers are water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyville alcohol, and modified polyvinyl alcohol, and gelatin, polyville alcohol, and modified polyvinyl alcohol are preferred. Mention may be made of bil alcohol and 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%. The degree of polymerization is preferably in the range of 100 to 3000. 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). The degree of polymerization is preferably in the range of 100 to 3000. Among these, unmodified or modified polyvinyl alcohol having a saponification degree of 80 to 100%, more preferably unmodified or alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95%.

  The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

[Transparent support]
The optical compensation film of the present invention may have a support for supporting the optical anisotropic layer. The support is preferably transparent, and specifically, the light transmittance is preferably 80% or more. As the support, a polymer film with controlled optical anisotropy may be used. As a material for forming the support, cellulose ester, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, and norbornene resin are used. 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. The cellulose ester or synthetic polymer film is preferably formed by a solvent casting method.
The thickness of the support is preferably 20 to 500 μm, and more preferably 50 to 200 μm.

  In order to improve adhesion between the support and a layer provided thereon (for example, an adhesive layer, an alignment film or an optically anisotropic layer), the support is subjected to surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet ray ( (UV) treatment, flame treatment, saponification treatment). An adhesive layer (undercoat layer) may be provided on the support.

[Polarizer]
The present invention also relates to a polarizing plate having a transparent protective film, a polarizing film, and the optical compensation film of the present invention. The polarizing plate of the present invention is used in a liquid crystal display device or the like as an elliptically polarizing plate or a circularly polarizing plate. The polarizer used in the polarizing plate of the present invention is not particularly limited, and any known polarizer such as an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film may be used. it can. The iodine-based polarizing film and the dye-based polarizing film are generally produced by stretching a polyvinyl alcohol-based film and dyeing with iodine or a dye. The polarizing axis of the polarizing film produced by such a method corresponds to the direction perpendicular to the stretching direction of the film.

  The transparent protective film for protecting the polarizer may be provided on both surfaces of the polarizer, or may be provided only on one surface of the polarizer. In the latter embodiment, it is preferable that the transparent support of the optical compensation film functions as a protective film on the surface on the other side of the polarizer. As the transparent protective film, it is preferable to use a cellulose ester film having high optical isotropy.

  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 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 values measured in three directions in total. Here, as the assumed value of the average refractive index, 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 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.

[Liquid Crystal Display]
The optical compensation film of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optical Compensation Bend), STN (Superied A Quantum V). It can be used for liquid crystal display devices in various display modes such as (Hybrid Aligned Nematic). Among them, it is preferable to use for a TN mode or OCB mode liquid crystal display device. For example, in the case of a TN mode transmissive liquid crystal display device, two polarizing plates of the present invention are arranged to face each other, and a TN mode liquid crystal cell is placed between the two polarizing plates arranged to face each other. Also, a pair of linearly polarizing plates are arranged opposite to each other, a TN mode liquid crystal cell is arranged between the pair of opposingly arranged linearly polarizing plates, and the optical compensation film of the present invention is placed between at least one of the linearly polarizing plates and the liquid crystal cell. You may arrange. The same applies to the OCB mode liquid crystal display device. In the case of a reflective liquid crystal display device, one polarizing plate may be used.

The present invention will be described more specifically with reference to the following 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 following examples.
[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 a 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, the retardation Rth in the thickness direction was 85 nm, and the in-plane retardation Re was 7 nm.

(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 mL / m ² and heated at 110 ° C. for 15 seconds under a steam far infrared heater manufactured by Noritake Co., Ltd. 3 mL / 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) ₂ 0H)
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 28 mL / m ² . A film was formed by drying 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, the surface of the formed film was rubbed in the longitudinal direction to obtain an alignment film.

(Formation of optically anisotropic layer)
A discotic liquid crystal coating liquid (OC-1: solid content concentration 32.6%; MEK solvent) having the following composition was heated in a thermostatic bath at 125 ° 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 produce an optical compensation film (CF-1).
When OC-1 was applied to the glass surface and the transition temperature (T _iso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured using a Mettler while raising the temperature with a polarizing microscope, T _iso was measured. _-lc was 130 ° C. On the other hand, since the melting point (T _mp ) of Irgacure 907, which is a photopolymerization initiator, is 77 ° C., it was found that Δ (= T _mp −T _iso-lc ) was −53 ° C. Moreover, considering the variation of the aging process, a thermostatic bath with a temperature of 120 ° C. and a temperature of 130 ° C. were separately prepared.
<Discotic liquid crystal coating liquid (OC-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 0.3 part by mass (Exemplary Compound G-1)
Kaya Cure DETX (Nippon Kayaku Co., Ltd.) 0.1 parts by mass (Exemplary Compound H-1)

[Comparative Example 2]
Except for using the discotic liquid crystal coating liquid (OC-2) prepared by replacing Irgacure 907 used in the preparation of the discotic liquid crystal coating liquid (OC-1) of Comparative Example 1 with Exemplified Compound F-1. An optical compensation film (CF-2) was produced in the same manner as in Example 1.
When OC-2 was applied to the glass surface and the transition temperature ( _Tiso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured in the same manner as in Comparative Example 1, it was 135 ° C. On the other hand, since the melting point (T _mp ) of Exemplified Compound F-1 that is a photopolymerization initiator is 44 ° C., Δ (= T _mp −T _iso-lc ) was found to be −91 ° C.

[Example 1]
A discotic liquid crystal coating liquid (OC-) prepared by replacing Irgacure 907, which is a photopolymerization initiator used for the preparation of the discotic liquid crystal coating liquid (OC-1) of Comparative Example 1, with Exemplified Compound A-11. An optical compensation film (CF-3) was produced in the same manner as in Comparative Example 1 except that 3) was used.
When OC-3 was applied to the glass surface and the transition temperature ( _Tiso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured in the same manner as in Comparative Example 1, it was 133 ° C. On the other hand, since the melting point (T _mp ) of Exemplified Compound A-11, which is a photopolymerization initiator, is 140 ° C., it was found that Δ (= T _mp −T _iso-lc ) was 7 ° C.

[Example 2]
A discotic liquid crystal coating liquid (OC-) prepared by replacing Irgacure 907, which is a photopolymerization initiator used in the preparation of the discotic liquid crystal coating liquid (OC-1) of Comparative Example 1, with Exemplified Compound A-3. An optical compensation film (CF-4) was produced in the same manner as in Comparative Example 1 except that 4) was used.
When OC-4 was applied to the glass surface and the transition temperature (T _iso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured in the same manner as in Comparative Example 1, it was 133 ° C. On the other hand, since the melting point (T _mp ) of Exemplified Compound A-3, which is a photopolymerization initiator, is 145 ° C., Δ (= T _mp −T _iso-lc ) was found to be 12 ° C.

[Example 3]
A discotic liquid crystal coating liquid (OC-) prepared by replacing Irgacure 907, which is a photopolymerization initiator used in the preparation of the discotic liquid crystal coating liquid (OC-1) of Comparative Example 1, with Exemplified Compound B-4. An optical compensation film (CF-5) was produced in the same manner as in Comparative Example 1 except that 5) was used.
When OC-5 was applied on the glass surface and the transition temperature (T _iso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured in the same manner as in Comparative Example 1, it was 133 ° C. On the other hand, since the melting point (T _mp ) of Exemplified Compound B-4, which is a photopolymerization initiator, is 110 ° C., Δ (= T _mp −T _iso-lc ) was found to be −23 ° C.

[Comparative Example 3]
(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 a 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, the in-plane slow axis coincided with the width direction, and the retardation Re was 36 nm. there were.

(Saponification and alignment film formation)
Next, as in Comparative Example 1, CA-2 was saponified to form an alignment film. However, the rubbing treatment at the time of forming the alignment film was carried out by rotating the rubbing roll axis 45 degrees counterclockwise with respect to the longitudinal direction of the surface and in the direction 45 degrees counterclockwise with respect to the longitudinal direction.

(Formation of optically anisotropic layer)
A discotic liquid crystal coating solution (OC-6: solid content concentration 35.5%; MEK solvent) having the following composition was heated for 3 minutes in a high-temperature bath at 125 ° C. 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 film (CF-6). Moreover, considering the variation of the aging process, a thermostatic bath with a temperature of 120 ° C. and a temperature of 130 ° C. were separately prepared.
<Discotic liquid crystal coating solution (OC-6)>
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 0.15 parts by weight
(CAB531-1 Eastman Chemical)
Irgacure 907 0.3 part by mass (Exemplary Compound G-1)
Kaya Cure DETX (manufactured by Nippon Kayaku Co., Ltd.) 0.1 parts by mass (Exemplary Compound H-1)

[Comparative Example 4]
A discotic liquid crystal coating liquid (OC-) prepared by replacing Irgacure 907, which is a photopolymerization initiator used for the preparation of the discotic liquid crystal coating liquid (OC-6) of Comparative Example 3, with Exemplified Compound F-1. An optical compensation film (CF-7) was produced in the same manner as in Comparative Example 3 except that 7) was used.
When OC-7 was applied to the glass surface and the transition temperature (T _iso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured in the same manner as in Comparative Example 1, it was 140 ° C. On the other hand, since the melting point (T _mp ) of Exemplified Compound F-1 which is a photopolymerization initiator is 44 ° C., Δ (= T _mp −T _iso-lc ) was found to be −96 ° C.

[Example 4]
A discotic liquid crystal coating liquid (OC-) prepared by replacing Irgacure 907, which is a photopolymerization initiator used for the preparation of the discotic liquid crystal coating liquid (OC-6) of Comparative Example 3, with Exemplified Compound A-11. An optical compensation film (CF-8) was produced in the same manner as in Comparative Example 1 except that 8) was used.
When OC-8 was applied to the glass surface and the transition temperature (T _iso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured in the same manner as in Comparative Example 1, it was 138 ° C. On the other hand, since the melting point (T _mp ) of Exemplified Compound A-11, which is a photopolymerization initiator, is 140 ° C., it was found that Δ (= T _mp −T _iso-lc ) was 2 ° C.

[Example 5]
For the preparation of the discotic liquid crystal coating liquid (OC-6) of Comparative Example 3, a discotic liquid crystal coating liquid (OC-) prepared by replacing Irgacure 907, which is a road plate photopolymerization initiator, with Exemplified Compound A-3 in this amount. An optical compensation film (CF-9) was produced in the same manner as in Comparative Example 1 except that 9) was used.
When OC-9 was applied to the glass surface and the transition temperature (T _iso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured in the same manner as in Comparative Example 1, it was 138 ° C. On the other hand, since the melting point (T _mp ) of Exemplified Compound A-3 which is a photopolymerization initiator is 145 ° C., it was found that Δ (= T _mp −T _iso-lc ) was 7 ° C.

[Example 6]
A discotic liquid crystal coating liquid (OC-10) prepared by replacing Irgacure 907, which is a photopolymerization initiator used in the preparation of the discotic liquid crystal coating liquid (OC-6) of Comparative Example 3, with Exemplified Compound B-4. An optical compensation film (CF-9) was produced in the same manner as in Comparative Example 1 except that the above was used.
When OC-9 was applied to the glass surface and the transition temperature (T _iso-lc ) of the isotropic phase-nematic liquid crystal phase after solvent drying was measured in the same manner as in Comparative Example 1, it was 138 ° C. On the other hand, since the melting point (T _mp ) of Exemplified Compound B-4 as a photopolymerization initiator is 110 ° C., it was found that Δ (= T _mp −T _iso-lc ) was −28 ° C.

[Example 7]
The dope obtained in Comparative Example 3 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 with a cellulose acetate film (CA-3) having a residual solvent amount of 0.3 mass% (thickness). 80 μm) was produced.
When the retardation of the produced cellulose acetate film (CA-3) was measured, the thickness direction retardation Rth was 83 nm, and the in-plane retardation Re was 6 nm.
(Saponification and alignment film formation)
In the same manner as in Comparative Example 1, the cellulose acetate film (CA-3) was subjected to saponification treatment, formation of an alignment film, and rubbing treatment.

(Formation of optically anisotropic layer)
A discotic liquid crystal coating solution (OC-11: solid content concentration 34.0%; MEK solvent) having the following composition was heated in a high-temperature bath at 125 ° 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 produce an optical compensation film (CF-11). Moreover, considering the variation of the aging process, a thermostatic bath with a temperature of 120 ° C. and a temperature of 130 ° C. were separately prepared.
<Discotic liquid crystal coating liquid (OC-11)>
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 (CAB551-0.2, manufactured by Eastman Chemical Co.) 0.08 parts by weight Cellulose acetate butyrate (CAB531-1, Eastman) 0.03 parts by mass Fluoroaliphatic group-containing polymer exemplary compound (P-1) 0.05 parts by mass Fluoroaliphatic group-containing polymer exemplary compound (P-2) 0.005 parts by mass Exemplary Compound A-11 3.0 parts by mass Kayacure DETX (manufactured by Nippon Kayaku Co., Ltd.) 0.1 parts by mass (Exemplary Compound H-1)

  About the optical compensation film obtained in Examples 1-7 and Comparative Examples 1-4, peeling evaluation of the optical compensation film was performed by the following method. The results of peel stability are shown in Table 1.

(Evaluation of peeling of optical compensation film)
The peeling of the optical compensation film was evaluated by preparing a test piece according to the JIS K 5400 8.5.2 base tape method. However, polyester adhesive tape NO31RH manufactured by Nitto Denko was used for evaluation. In consideration of the stability to fluctuations in the aging process, for each sample, the temperature of the constant temperature bath was set to 120 ° C., and the same was evaluated for those set to 130 ° C. Used to score.
Moreover, the same evaluation was performed using the polyester adhesive tape NO31B made from Nitto Denko as a tape with higher adhesive force as forced peeling conditions, and it was set as peeling evaluation (forced).

  Table 1 shows that in the sample of the comparative example of the present invention, the temperature in the aging process varies ± 5 ° C., so that tens of percent peeling occurs in the peeling test, whereas the sample of the example of the present invention does not peel at all. It is clear that delamination can be stably prevented against process variations.

(Evaluation of optical properties of optical compensation film)
With respect to the optical compensation film produced in Example 1, the Re (550) was measured with KOBRA 21ADH and light having a wavelength of 550 nm. As a result, it was 30.6 nm. Similarly, Re (550) of the optical compensation film produced in Example 4 was measured and found to be 30.0 nm.

(Production of polarizer)
PVA having an average polymerization degree of 4000 and a saponification degree of 99.8 mol% was dissolved in water to obtain a 4.0% aqueous solution. This solution was band-cast using a die having a taper and dried to form a film so that the width before stretching was 110 mm, the thickness was 120 μm at the left end, and 135 μm at the right end.
The film was peeled from the band, stretched in the longitudinal direction in a dry state, and immersed in an aqueous solution of 0.5 g / L iodine and 50 g / L potassium iodide for 1 minute at 30 ° C., and then boric acid 100 g / L. It was immersed in an aqueous solution of L and potassium iodide 60 g / L at 70 ° C. for 5 minutes, further washed with water at 20 ° C. for 10 seconds, and then dried at 80 ° C. for 5 minutes to obtain an iodine polarizer. The polarizer had a width of 660 mm and a thickness of 20 μm.

(Preparation of polarizing plate)
Using the polyvinyl alcohol-based adhesive, the transparent support surface side of the optical compensation film of Example 1 and Example 4 and the polarizer were bonded. In addition, triacetyl cellulose film: Fujitac TD-80U was subjected to surface saponification treatment in the same manner as described in Example 1 of WO02 / 46809, and using a polyvinyl alcohol-based adhesive, A polarizing plate was prepared by bonding to the opposite side. In that case, it arrange | positioned so that the longitudinal direction of a polarizer and the longitudinal direction of an optical compensation film and the said triacetyl cellulose film may become parallel.

(Production of TN liquid crystal cell)
An ellipse produced by peeling off a pair of polarizing plates provided in a liquid crystal display device (AQUAS LC20C1S, manufactured by Sharp Corporation) using a TN type liquid crystal cell, and bonding the optical compensation film produced in Example 1 instead. The polarizing plates were attached to the observer side and the backlight side one by one via an adhesive so that the optical compensation film was on the liquid crystal cell side. The transmission axis of the elliptical polarizing plate on the observer side and the transmission axis of the elliptical polarizing plate on the backlight side were arranged to be in the O mode.
About the produced liquid crystal display device, the viewing angle was measured in eight steps from black display (L1) to white display (L8) using the measuring machine (EZ-Contrast160D, ELDIM company make). The measurement results are shown in Table 2.

表２より、表示装置の視野角特性が良好であることがわかる。

Table 2 shows that the viewing angle characteristics of the display device are good.

(Preparation of bend alignment liquid crystal cell)
A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, 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 6 μm. A bend-aligned liquid crystal cell was prepared by injecting a liquid crystal compound (ZLI1132, manufactured by Merck & Co., Inc.) having a Δn (difference between the refractive indexes ne and no) of 0.1396. The size of the liquid crystal cell was 20 inches.
Two elliptical polarizing plates prepared by bonding the optical compensation film prepared in Example 4 were attached so as to sandwich the prepared bend alignment cell. The optically anisotropic layer of the elliptically polarizing plate was arranged so as to face the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer facing it were 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.
As an evaluation measure of the viewing angle, the contrast ratio of the visual field image is maintained at 10 or more, and gradation inversion on the black side does not occur (that is, inversion occurs between the black display (L1) and the next level (L2)). None) A range of open angle values was used. Table 3 shows the measurement results.

表３より、表示装置の視野角特性が良好であることがわかる。

Table 3 shows that the viewing angle characteristics of the display device are good.

Claims (10)

An optical compensation film having an optically anisotropic layer formed by curing a liquid crystal composition containing at least a liquid crystal compound having a polymerizable group and a polymerization initiator, the melting point T _{mp of the} polymerization initiator and the above An optical compensation film characterized in that the isotropic phase-nematic liquid crystal phase transition temperature T _{iso-lc of the} liquid crystal composition satisfies the following formula (1):
Formula (1): (DELTA) = _Tmp - _Tiso-lc > =-30 _degreeC . The optical system according to claim 1, wherein a melting point _Tmp of the polymerization initiator and a transition temperature _Tiso-lc of an isotropic phase-nematic liquid crystal phase of the liquid crystalline composition satisfy the following formula (1). Compensation film:
Formula (2): (DELTA) = _Tmp - _Tiso-lc > = 0 _degreeC .   The optical compensation film according to claim 1, wherein the liquid crystalline compound is a discotic liquid crystal.   The optical compensation film according to claim 1, further comprising a support and an alignment film between the support and the optical anisotropic layer.   The optical compensation film according to claim 1, wherein the alignment film contains an organic compound having a polymerizable group.   6. The optical compensation film according to claim 1, wherein the transparent support is a cellulose acylate film.   The polarizing plate which has a transparent protective film, a polarizing film, and the optical compensation film of any one of Claims 1-6.   A TN liquid crystal display device having at least a TN liquid crystal cell and the polarizing plate according to claim 7.   A bend alignment mode type liquid crystal display device comprising at least a bend alignment mode liquid crystal cell and the polarizing plate according to claim 7. At least contains a liquid crystalline compound and a polymerization initiator having a polymerizable group, an isotropic phase - liquid crystal composition transition temperature of a nematic liquid crystal phase is a _{T iso-lc, 5 ℃ ~50} ℃ than T _iso-lc A step of aligning the molecules of the liquid crystalline compound while maintaining a low temperature, and irradiating the liquid crystalline composition with light to fix the molecules of the liquid crystalline compound in an aligned state to form an optically anisotropic layer An optical compensation characterized in that the melting point _Tmp of the polymerization initiator and the transition temperature _Tiso-lc of the isotropic-nematic liquid crystal phase of the liquid crystalline composition satisfy the following formula (1): Film production method:
Formula (1): (DELTA) = _Tmp - _Tiso-lc > =-30 _degreeC .