JP2004300420A - Liquid crystal composition, polymer, retardation plate, and elliptic polarization plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxial liquid crystal composition which is very useful for making a retardation plate and has triaxial refractive indexes controlled, to provide a polymer obtained from the above biaxial liquid crystal composition, and to provide a retardation plate and an elliptic polarization plate by using the above biaxial liquid crystal composition. <P>SOLUTION: The biaxial liquid crystal composition, containing a liquid crystal compound and a refractive-index controlling agent and revealing a biaxial liquid crystal phase, is characterized in that, when letting the triaxial refractive indexes of the above biaxial liquid crystal composition be nx, ny and nz in decreasing order and letting the triaxial refractive indexes of the biaxial composition obtained by excluding the refractive index-controlling agent from the above biaxial liquid crystal composition be nx0, ny0 and nz0 in decreasing order, then the value of (nx-ny)/(ny-nz) and that of (nx0-ny0)/(ny0-nz0) are different. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a biaxial liquid crystal composition, and more particularly to a biaxial liquid crystal composition in which the refractive index in the triaxial direction is controlled and is very useful for producing a retardation plate.
The present invention also relates to a polymer obtained from the biaxial liquid crystal composition, and a retardation plate and an elliptically polarizing plate using the biaxial liquid crystal composition.

A biaxial film in which the refractive index in the triaxial direction is controlled is useful in the optical field using polarized light. In particular, in the field of liquid crystal displays, such a film capable of finely controlling the polarization is highly important.
When producing such an optical biaxial film, a method of obtaining a film obtained from a polymer by biaxial stretching is common (see, for example, Patent Document 1). Thus, when a biaxial film is obtained by biaxial stretching, the refractive index in the triaxial direction can be controlled by the stretching magnification, so that the desired refractive index can be controlled relatively easily.

On the other hand, recently, a method for obtaining a biaxial film using a biaxial liquid crystal has been proposed (see, for example, Patent Document 2 and Patent Document 3). A biaxial film using a biaxial liquid crystal has the merit that the film thickness can be made very thin compared to the biaxially stretched film that has been widely used so far. The use of conductive liquid crystal is a useful means for making the device thinner and lighter.
However, when a biaxial film is produced using a biaxial liquid crystal, there arises a problem that the refractive index in the triaxial direction cannot be arbitrarily controlled. This is because the refractive index in the triaxial direction of the obtained biaxial film is almost uniquely determined by the refractive index in the triaxial direction of the compound (liquid crystal compound) that exhibits a liquid crystal phase. That is, in order to make the refractive index in the three directions of the biaxial film the desired refractive index, there is only a method of synthesizing a liquid crystal compound having the desired refractive index. However, since the number of compounds expressing a biaxial liquid crystal phase is very small compared to a compound expressing a uniaxial liquid crystal (see, for example, Non-Patent Document 1), the refractive index in three directions can be arbitrarily set. It was very difficult to control.
JP-A-2-264905 Japanese Patent Laid-Open No. 2002-6138 JP 2002-174730 A D. Demus, J.M. Goodby et al., “Handbook of Liquid Crystals Vol. 2B: Low Molecular Weight Liquid Crystals II”, published by WILEY-VCH, p. 933-943

  Accordingly, an object of the present invention is to provide a biaxial liquid crystal composition capable of arbitrarily controlling the refractive index in the triaxial direction of the biaxial liquid crystal composition without changing the liquid crystal compound. Furthermore, an object of the present invention is to provide a polymer, a retardation plate, and an elliptically polarizing plate using the biaxial liquid crystal composition.

The above problem can be solved by adding an appropriate refractive index control agent to the biaxial liquid crystal composition and setting the refractive index in the triaxial direction to a desired value. Specifically, it is solved by the following inventions (1) to (14).
(1) A biaxial liquid crystal composition that includes a liquid crystal compound and a refractive index control agent and expresses a biaxial liquid crystal phase, and the refractive index in the triaxial direction of the biaxial liquid crystal composition is nx in descending order. , Ny, nz, and when the refractive index in the triaxial direction of the biaxial composition obtained by removing the refractive index control agent from the biaxial liquid crystal composition is nx0, ny0, nz0 in descending order, (nx -Ny) / (ny-nz) and (nx0-ny0) / (ny0-nz0) are different from each other in a biaxial liquid crystal composition.
(2) The value of (nx-ny) / (ny-nz) and (nx0-ny0) / (ny0-nz0) satisfies the following formula (I), described in (1) above Biaxial liquid crystal composition.

Formula (I)
(Nx-ny) / (ny-nz)> (nx0-ny0) / (ny0-nz0)

(3) The biaxial liquid crystal composition as described in (1) or (2) above, wherein the refractive index controlling agent contains a compound having a rod-like shape.
(4) The biaxial liquid crystal composition according to any one of (1) to (3), wherein the refractive index control agent is represented by the following general formula (IC).

General formula (IC)
Q1-L1-Cy1-L2- (Cy2-L3) n-Cy3-L4-Q2

  In general formula (IC), Q1 and Q2 are each independently a polymerizable group, L1 and L4 are each independently a divalent linking group, and L2 and L3 are each independently a single bond or a divalent linking group. Cy1, Cy2 and Cy3 are each independently a divalent cyclic group, and n is 0, 1 or 2.

(5) The values of (nx-ny) / (ny-nz) and (nx0-ny0) / (ny0-nz0) satisfy the following formula (II), and the two described in (1) Axial liquid crystal composition.

Formula (II)
(Nx-ny) / (ny-nz) <(nx0-ny0) / (ny0-nz0)

(6) The biaxial liquid crystal composition as described in (1) or (5) above, wherein the refractive index controlling agent contains a compound having a disc-like shape.
(7) The biaxial liquid crystal composition according to the above (1), (5) or (6), wherein the refractive index control agent is represented by the following general formula (ID).

General formula (ID)
D (-LQ) n

  In general formula (ID), D is a disk-shaped core, L is a divalent linking group, Q is a polymerizable group, and n is an integer of 4 to 12.

(8) The biaxial liquid crystal composition according to any one of the above (1) to (7), wherein the refractive index control agent exhibits a liquid crystal phase.
(9) The biaxial liquid crystal composition according to any one of (1) to (8), wherein the liquid crystal compound has a polymerizable group.
(10) The biaxial liquid crystal composition as described in any one of (1) to (9) above, wherein the refractive index control agent has a polymerizable group.
(11) The biaxial liquid crystal phase according to any one of (1) to (10) above, wherein the biaxial liquid crystal phase expressed by the biaxial liquid crystal composition is a biaxial nematic liquid crystal phase. Composition.
(12) A retardation plate having an alignment film and at least one optically anisotropic layer on a transparent support, wherein the optically anisotropic layer is any one of (1) to (11) above. A phase difference plate comprising a biaxial liquid crystal composition.
(13) An elliptically polarizing plate having the retardation plate as described in (12) above and a polarizing film.
(14) A polymer obtained by polymerizing the biaxial liquid crystal composition according to (9) or (10).

  ADVANTAGE OF THE INVENTION According to this invention, the biaxial liquid crystal composition which can control arbitrarily the refractive index of the triaxial direction of a biaxial liquid crystal composition, without changing a liquid crystal compound can be provided. Furthermore, according to the present invention, it is possible to provide a polymer, a retardation plate and an elliptically polarizing plate using a biaxial liquid crystal composition in which the refractive index in the triaxial direction is controlled.

Hereinafter, the present invention will be described in more detail.
[Liquid Crystal Compound]
The liquid crystal compound contained in the biaxial liquid crystal composition of the present invention is a liquid crystal compound that optically exhibits biaxiality alone or as a mixture with other compounds. In other words, it is a liquid crystal compound in which the refractive index nx1, ny1, and nz1 in the three-axis directions of the liquid crystal phase expressed by the compound or the mixture is different and satisfies, for example, the relationship of nx1>ny1> nz1.

  When the liquid crystal compound used in the present invention is used for a phase difference plate, it is desirable to have the above properties and at the same time exhibit good monodomain properties for uniform alignment without defects. When the monodomain property is poor, the resulting structure becomes a polydomain, an orientation defect occurs at the boundary between domains, and light is scattered. This is undesirable because it leads to a decrease in the transmittance of the retardation plate.

  Examples of the biaxial liquid crystal phase exhibited by the liquid crystal compound used in the present invention include a biaxial nematic phase, a biaxial smectic A phase, and a biaxial smectic C phase. Among these liquid crystal phases, a biaxial nematic phase (Nb phase) exhibiting good monodomain properties is preferable. A biaxial nematic phase is a kind of liquid crystal phase that a nematic liquid crystal compound can take. When the space of the liquid crystal phase is defined by the x, y, and z axes, the liquid crystal compound is centered on the y axis. The free rotation of the xz plane and the free rotation of the xy plane around the z axis are also prohibited.

The liquid crystal compound used in the present invention may be a low molecular liquid crystal compound or a polymer liquid crystal compound.
The liquid crystal compound preferably has a polymerizable group. In particular, when a liquid crystal compound is used for the phase difference plate, a polymerizable compound is preferably used in order to fix the orientation of the low molecular compound. Moreover, if it is a high molecular compound, in order to fix orientation, it is preferable that it is a polymeric compound, However, When a glass transition point is 30 degreeC or more, it does not necessarily need to be polymeric. Examples of the polymerizable group include examples (Q-1) to (Q-17) of the polymerizable group that the refractive index control agent can have.

  In the present invention, as the liquid crystal compound, one type of compound that expresses a biaxial liquid crystal phase independently (hereinafter referred to as a biaxial liquid crystal compound) may be used, or two or more types of biaxial liquid crystal compounds may be used. You may use together. For example, a polymerizable biaxial liquid crystal compound and a non-polymerizable biaxial liquid crystal compound can be used in combination. It is also possible to use a low-molecular liquid crystal compound and a high-molecular liquid crystal compound in combination. In addition, a biaxial liquid crystal mixture (specifically, for example, a uniaxial discotic) that exhibits a biaxial liquid crystal phase by mixing two or more compounds that do not exhibit a biaxial liquid crystal phase alone. It is also possible to use a mixture of a liquid crystal compound and a rod-like liquid crystal compound. It is preferable to use at least one biaxial liquid crystal compound.

  Specific examples of the biaxial liquid crystal compound include, for example, compounds described in pages 124 to 143 of Synthetic Organic Chemistry, Vol. 49, No. 5 (1991), D.I. W. Bruce et al. [AN EU-SPONSORED'OXFORD WORKSHOP ON BIAXIAL NEMATICS '(St Benet's Hall, University of Oxford 20-22 December, 1996), p157-2. CHANDRASEKHAR et al. [A Thermotropic Biaxial Nematic Liquid Crystal; Mol. Cryst. Liq. Cryst. , 1988, Vol. 165, pp. 123-130], D.I. Demus, J.M. Goodby et al. [Handbook of Liquid Crystals Vol. 2B: Low Molecular Weight Liquid Crystals II, published by WILEY-VCH, pp 933-943], and the like. A polymerizable group may be introduced into the compound for use.

Specific examples of the low-molecular liquid crystal compound having a polymerizable group that can be used in the present invention include compounds described in JP-A-2002-174730.
In addition to the above, specific examples of the low-molecular liquid crystal compound that can be preferably used in the present invention are shown below, but the present invention is not limited thereto.

Specific examples of the polymer liquid crystal compound include, for example, H.P. F. Leube et al. [Optical investigations on a liquid-crystalline side-chain polymer with biaxial nematic and biaxial smectic A phase; Makromol. Chem., 1991, Vol.192, pp.1317-1328], [New bilaterally linked mesogens in macromolecules, 1998, Vol.31, pp. 3537-3541] etc., and the like can be mentioned as main-chain polymers with exhibition of biaxial fluctuation in nematic phase;
In addition to the above, specific examples of the polymer liquid crystal compound that can be preferably used in the present invention are shown below, but the present invention is not limited thereto.

[Refractive index control agent]
In the present invention, the refractive index control agent refers to a compound that can be added to the biaxial liquid crystal composition to change the refractive index in the triaxial direction of the composition. That is, by adding a refractive index control agent to the biaxial liquid crystal composition, the refractive index in the triaxial direction (nx0, ny0, nz0 in descending order) of the biaxial liquid crystal composition (with a refractive index control agent) The biaxial liquid crystal composition before adding the refractive index control agent can be changed in comparison with the refractive index in the triaxial direction (nx, ny, nz in descending order). Specifically, the values of (nx-ny) / (ny-nz) and (nx0-ny0) / (ny0-nz0) can be made different.
Further, by selecting the molecular structure of the refractive index control agent, it is possible to satisfy the following formula (I) or to satisfy the following formula (II).

The biaxial liquid crystal composition of the present invention functions as a biaxial liquid crystal when the refractive index in the triaxial direction, which is changed by the addition of the refractive index control agent, satisfies the following formula (I): It is preferable that the value of (ny−nz) does not approach 0. The value of (ny−nz) is more preferably 0.005 or more.
In addition, when the refractive index in the triaxial direction, which changes due to the addition of the refractive index control agent, satisfies the following formula (II), the value of (nx−ny) is 0 for functioning as a biaxial liquid crystal. It is preferable not to approach. The value of (nx−ny) is more preferably 0.005 or more.

Formula (I)
(Nx-ny) / (ny-nz)> (nx0-ny0) / (ny0-nz0)
Formula (II)
(Nx-ny) / (ny-nz) <(nx0-ny0) / (ny0-nz0)

  In the above formulas (I) and (II), nx, ny, and nz represent the refractive indexes in the triaxial direction of the biaxial liquid crystal composition containing the biaxial liquid crystal compound and the refractive index control agent, and nx> ny > Nz. Further, nx0, ny0, and nz0 indicate the refractive indexes in the triaxial direction of the biaxial composition obtained by excluding the refractive index control agent from the biaxial liquid crystal composition having a relationship of nx> ny> nz. , Nx0> ny0> nz0.

  In the biaxial liquid crystal phase, the values of nx, ny, nz and nx0, ny0, nz0 may change depending on the temperature depending on the additive added to the liquid crystal compound or the liquid crystal composition. In such a case, in the present invention, the above nx, ny, nz and nx0, ny0, nz0 are 20 ° C. lower than the upper limit temperature of the temperature range (liquid crystal temperature range) in which each composition exhibits a biaxial liquid crystal phase. It shall be the value measured in. When the liquid crystal temperature range of one of the compositions is 20 ° C. or less, the value measured at 10 ° C. from the upper limit temperature of the liquid crystal phase, and when the liquid crystal temperature range of either composition is 10 ° C. or less To a value measured at 5 ° C., or a value measured at 2 ° C. when the liquid crystal temperature range of either composition is 5 ° C. or lower.

The refractive index control agent that satisfies the formula (I) is preferably a compound having a rod-like shape.
A compound having a rod-like shape is a compound having a rod-like molecular structure having an aromatic ring or an aliphatic ring as a core, a compound in which a substituent is introduced into the rod-like molecule, and also the side chain portion of the rod-like molecule. A compound substituted with the above substituent may be used. Here, examples of the substituent include groups selected from the following substituent group A.

(Substituent group A)
Hydrogen atom, alkyl group (for example, methyl group, ethyl group, isopropyl group, tert-butyl group), alkenyl group (for example, vinyl group, allyl group, 2-butenyl group, 3-pentenyl group, etc.), alkynyl Group (for example, propargyl group, 3-pentynyl group, etc.), aryl group (for example, phenyl group, p-methylphenyl group, naphthyl group, etc.), substituted or unsubstituted amino group (for example, no Substituted amino group, methylamino group, dimethylamino group, diethylamino group, anilino group, etc.), alkoxy group (eg, methoxy group, ethoxy group, butoxy group etc.), aryloxy group (eg, phenyloxy) Group, 2-naphthyloxy group and the like), acyl group (for example, acetyl group, Azoyl group, formyl group, pivaloyl group, etc.), alkoxycarbonyl group (for example, methoxycarbonyl group, ethoxycarbonyl group, etc.), aryloxycarbonyl group (for example, phenyloxycarbonyl group, etc.), Acyloxy group (for example, acetoxy group, benzoyloxy group and the like), acylamino group (for example, acetylamino group, benzoylamino group and the like), alkoxycarbonylamino group (for example, methoxycarbonylamino group and the like) , Aryloxycarbonylamino group (for example, phenyloxycarbonylamino group and the like), sulfonylamino group (for example, methanesulfonylamino group, benzenesulfonylamino group and the like), Rufamoyl group (for example, sulfamoyl group, methylsulfamoyl group, dimethylsulfamoyl group, phenylsulfamoyl group and the like), carbamoyl group (for example, unsubstituted carbamoyl group, methylcarbamoyl group, diethylcarbamoyl group, Phenylcarbamoyl group, etc.), alkylthio group (eg, methylthio group, ethylthio group etc.), arylthio group (eg, phenylthio group etc.), sulfonyl group (eg, mesyl group, tosyl group etc.) ), Sulfinyl group (for example, methanesulfinyl group, benzenesulfinyl group, etc.), ureido group (for example, unsubstituted ureido group, methylureido group, phenylureido group, etc.), phosphoric acid amide group (For example, , Diethylphosphoric acid amide group, phenylphosphoric acid amide group etc.), hydroxy group, mercapto group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, A nitro group, a hydroxamic acid group, a sulfino group, a hydrazino group, an imino group, a heterocyclic group (for example, a heterocyclic group having a heteroatom such as a nitrogen atom, an oxygen atom, a sulfur atom, such as an imidazolyl group, a pyridyl group, A quinolyl group, a furyl group, a piperidyl group, a morpholino group, a benzoxazolyl group, a benzimidazolyl group, a benzthiazolyl group, etc.) and a silyl group (for example, a trimethylsilyl group, a triphenylsilyl group, etc.).
These substituents may be further substituted with these substituents. Moreover, when it has two or more substituents, they may be the same or different. If possible, they may be bonded to each other to form a ring.

  Further, the side chain portion of the rod-like molecule is a substituent substituted with an aromatic ring or an aliphatic ring, and examples of the substituent include a group selected from the following substituent group B.

(Substituent group B)
An alkyl group (for example, methyl group, ethyl group, isopropyl group, tert-butyl group), alkenyl group (for example, vinyl group, allyl group, 2-butenyl group, 3-pentenyl group, etc.), alkynyl group (for example, , Propargyl group, 3-pentynyl group and the like), amino group (for example, unsubstituted amino group, methylamino group, dimethylamino group, diethylamino group, anilino group and the like), alkoxy group (for example, methoxy group) , An ethoxy group, a butoxy group, etc.), an acyl group (eg, an acetyl group, a benzoyl group, a formyl group, a pivaloyl group, etc.), an alkoxycarbonyl group (eg, a methoxycarbonyl group, an ethoxycarbonyl group, etc.) Acyloxy group (for example, acetoxy group, benzoy Oxy group etc.), acylamino group (eg acetylamino group, benzoylamino group etc.), carbamoyl group (eg unsubstituted carbamoyl group, methylcarbamoyl group, diethylcarbamoyl group, phenylcarbamoyl group etc.) Hydroxy group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, carboxyl group, silyl group (for example, trimethylsilyl group, triphenylsilyl group, etc.).

The refractive index control agent is preferably a compound having a rod-like shape and capable of developing a liquid crystal phase, that is, a rod-like liquid crystal compound.
Examples of the rod-like liquid crystal compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles.
The liquid crystal phase that the rod-like liquid crystal compound develops is described in detail in Chapter 2 of the Liquid Crystal Handbook (published by Maruzen Co., Ltd. 2000), and examples thereof include a nematic phase, a cholesteric phase, and a smectic phase. As the rod-like liquid crystal phase, a nematic phase is particularly preferable.

The refractive index control agent preferably has a polymerizable group, particularly a rod-like liquid crystal compound having a polymerizable group, in order to fix the alignment of the liquid crystal compound contained in the biaxial liquid crystal composition of the present invention. .
As rod-like liquid crystal compounds having a polymerizable group, Makromol. Chem., 190, 2255 (1989), Advanced Materials, 5, 107 (1993), US Pat. Nos. 4,683,327, 5,622,648 and 5,770,107. World Patents (WO) 95/22586, 95/24455, 97/00600, 98/23580, 98/52905, JP-A-1-272551, 6-16616, 7 No. 110469, 11-80081, and JP-A No. 2001-328773 can be used.

  The refractive index controlling agent is particularly preferably a rod-like liquid crystal compound represented by the following general formula (I-C).

General formula (IC)
Q1-L1-Cy1-L2- (Cy2-L3) n-Cy3-L4-Q2

  In general formula (IC), Q1 and Q2 are each independently a polymerizable group, L1 and L4 are each independently a divalent linking group, and L2 and L3 are each independently a single bond or a divalent linking group. Cy1, Cy2 and Cy3 are each independently a divalent cyclic group, and n is 0, 1 or 2.

Hereinafter, the polymerizable rod-like liquid crystal compound represented by the general formula (IC) will be further described.
In general formula (IC), Q1 and Q2 are each independently a polymerizable group. The polymerization reaction of the polymerizable group is preferably addition polymerization (including ring-opening polymerization) or condensation polymerization. In other words, the polymerizable group is preferably a functional group capable of addition polymerization reaction or condensation polymerization reaction. Examples of polymerizable groups are shown below.

  In general formula (I-C), L1 and L4 are each independently a divalent linking group. L 1 and L 4 are each independently selected from the group consisting of —O—, —S—, —C (═O) —, —NR 1 —, a divalent chain group, a divalent cyclic group, and combinations thereof. A divalent linking group is preferred. R1 is an alkyl group having 1 to 7 carbon atoms or a hydrogen atom.

  Preferred examples of the divalent linking group comprising the above combination are shown below. Here, the left side is coupled to Q (Q1 or Q2), and the right side is coupled to Cy (Cy1 or Cy3).

L-1: —CO—O—divalent chain group—O—
L-2: —CO—O—divalent chain group —O—CO—
L-3: —CO—O—divalent chain group —O—CO—O—
L-4: -CO-O-divalent chain group -O-divalent cyclic group-
L-5: —CO—O—divalent chain group—O—divalent cyclic group—CO—O—
L-6: -CO-O-divalent chain group -O-divalent cyclic group -O-CO-
L-7: -CO-O-divalent chain group-O-divalent cyclic group-divalent chain group-
L-8: -CO-O-divalent chain group-O-divalent cyclic group-divalent chain group-CO-O-
L-9: -CO-O-divalent chain group-O-divalent cyclic group-divalent chain group-O-CO-
L-10: —CO—O—divalent chain group—O—CO—divalent cyclic group—
L-11: -CO-O-divalent chain group-O-CO-divalent cyclic group-CO-O-
L-12: -CO-O-divalent chain group -O-CO-divalent cyclic group -O-CO-
L-13: —CO—O—Divalent chain group—O—CO—Divalent cyclic group—Divalent chain group—
L-14: -CO-O-divalent chain group-O-CO-divalent cyclic group-divalent chain group-CO-O-
L-15: -CO-O-divalent chain group-O-CO-divalent cyclic group-divalent chain group-O-CO-
L-16: —CO—O—divalent chain group—O—CO—O—divalent cyclic group—
L-17: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -CO-O-
L-18: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -O-CO-
L-19: —CO—O—divalent chain group—O—CO—O—divalent cyclic group—divalent chain group—
L-20: -CO-O-divalent chain group-O-CO-O-divalent cyclic group-divalent chain group-CO-O-
L-21: -CO-O-divalent chain group-O-CO-O-divalent cyclic group-divalent chain group-O-CO-

  The divalent chain group means an alkylene group, a substituted alkylene group, an alkenylene group, a substituted alkenylene group, an alkynylene group, or a substituted alkynylene group. An alkylene group, a substituted alkylene group, an alkenylene group and a substituted alkenylene group are preferred, and an alkylene group and an alkenylene group are more preferred.

Here, the alkylene group may have a branch. The alkylene group preferably has 1 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkylene part of the substituted alkylene group is the same as the above alkylene group. Examples of the substituent include a halogen atom.
The alkenylene group may have a branch. The alkenylene group preferably has 2 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkylene part of the substituted alkylene group is the same as the above alkylene group. Examples of the substituent include a halogen atom.
The alkynylene group may have a branch. The alkynylene group preferably has 2 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkynylene part of the substituted alkynylene group is the same as the above alkynylene group. Examples of the substituent include a halogen atom.
Specific examples of the divalent chain group include ethylene, trimethylene, propylene, butamethylene, 1-methyl-butamethylene, pentamethylene, hexamethylene, octamethylene, 2-butenylene, 2-butynylene and the like.

The definitions and examples of the divalent cyclic group are the same as those of Cy1, Cy2 and Cy3 described later.
R1 is preferably an alkyl group having 1 to 4 carbon atoms or a hydrogen atom, more preferably a methyl group, an ethyl group or a hydrogen atom, and most preferably a hydrogen atom.

  In general formula (I-C), L2 and L3 are each independently a single bond or a divalent linking group. L 2 and L 3 are each independently a divalent linkage selected from the group consisting of —O—, —S—, —CO—, —NR 2 —, a divalent chain group, a divalent cyclic group, and combinations thereof. It is preferably a group or a single bond. R2 is an alkyl group having 1 to 7 carbon atoms or a hydrogen atom, preferably an alkyl group having 1 to 4 carbon atoms or a hydrogen atom, and more preferably a methyl group, an ethyl group or a hydrogen atom. Preferably, it is a hydrogen atom. The divalent chain group and the divalent cyclic group have the same definitions as L1 and L4.

  In the general formula (I-C), n is 0, 1 or 2. When n is 2, the two L3s may be the same or different, and the two Cy2s may be the same or different. n is preferably 1 or 2, and more preferably 1.

In general formula (IC), Cy1, Cy2 and Cy3 are each independently a divalent cyclic group.
The ring contained in the cyclic group is preferably a 5-membered ring, a 6-membered ring, or a 7-membered ring, more preferably a 5-membered ring or a 6-membered ring, and most preferably a 6-membered ring. The ring contained in the cyclic group may be a condensed ring. However, it is more preferably a monocycle than a condensed ring.
The ring contained in the cyclic group may be any of an aromatic ring, an aliphatic ring, and a heterocyclic ring. Examples of the aromatic ring include a benzene ring and a naphthalene ring. Examples of the aliphatic ring include a cyclohexane ring. Examples of the heterocyclic ring include a pyridine ring and a pyrimidine ring.

As the cyclic group having a benzene ring, 1,4-phenylene is preferable. As the cyclic group having a naphthalene ring, naphthalene-1,5-diyl and naphthalene-2,6-diyl are preferable. The cyclic group having a cyclohexane ring is preferably 1,4-cyclohexylene. As the cyclic group having a pyridine ring, pyridine-2,5-diyl is preferable. The cyclic group having a pyrimidine ring is preferably pyrimidine-2,5-diyl.
The cyclic group may have a substituent. Examples of the substituent include a halogen atom, a cyano group, a nitro group, an alkyl group having 1 to 5 carbon atoms, a halogen-substituted alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. An alkylthio group having 1 to 5 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, a carbamoyl group, and an alkyl-substituted carbamoyl group having 2 to 6 carbon atoms And an acylamino group having 2 to 6 carbon atoms.

  Examples of the polymerizable rod-like liquid crystal compound represented by the general formula (I-C) are shown below, but the present invention is not limited thereto.

The refractive index control agent satisfying the formula (II) is preferably a compound having a disk shape.
A compound having a discoid shape is a compound having a discotic molecular structure having an aromatic ring or an aliphatic ring as a core, a compound in which a substituent is introduced into the discotic molecule, and the side of the discotic molecule. A compound in which the chain portion is replaced with another substituent may be used. Here, examples of the substituent include groups exemplified in the substituent group A. Each group of the substituent group A may be further substituted with a group exemplified in the substituent group A. Moreover, when it has two or more substituents, they may be the same or different. If possible, they may be bonded to each other to form a ring.

  The side chain portion of the discotic molecule is a substituent substituted with an aromatic ring or an aliphatic ring, and examples of the substituent include the groups listed in the substituent group B.

The refractive index control agent is preferably a compound having a disk shape and capable of developing a liquid crystal phase, that is, a discotic liquid crystal compound.
As the discotic liquid crystal compound, 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, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhanget al., J. Am. Chem. Soc., Vol. 116, page 2655 (1994)) can be used.
Examples of the liquid crystal phase expressed by the discotic liquid crystal compound include a columnar phase, a columnar lamellar phase, a columnar nematic phase, and a discotic nematic phase. Among these, a discotic nematic phase is particularly preferable.

  The refractive index control agent preferably has a polymerizable group in order to fix the alignment of the liquid crystal compound, and is particularly preferably a discotic liquid crystal compound having a polymerizable group. In particular, a compound represented by the following general formula (ID) is preferable.

General formula (ID)
D (-LQ) n

  In general formula (ID), D is a disk-shaped core, L is a divalent linking group, Q is a polymerizable group, and n is an integer of 4 to 12.

  Examples of the disk-shaped core (D) of the general formula (I-D) are shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).

  In the general formula (ID), the divalent linking group (L) is an alkylene group, an alkenylene group, an arylene group, —C (═O) —, —NH—, —O—, —S— and combinations thereof. A divalent linking group selected from the group consisting of The divalent linking group (L) is at least a divalent group selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —C (═O) —, —NH—, —O—, and —S—. More preferably, the two groups are combined. The divalent linking group (L) is a group obtained by combining at least two divalent groups selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, -C (= O)-and -O-. Is most preferred.

  Here, 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 to 10. The alkylene group, alkenylene group and arylene group may have a substituent (eg, alkyl group, halogen atom, cyano, alkoxy group, acyloxy group).

  Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (Q). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group.

L1: -AL-C (= O) -O-AL-
L2: -AL-C (= O) -O-AL-O-
L3: -AL-C (= O) -O-AL-O-AL-
L4: -AL-C (= O) -O-AL-OC (= O)-
L5: -C (= O) -AR-O-AL-
L6: -C (= O) -AR-O-AL-O-
L7: -C (= O) -AR-O-AL-OC (= O)-
L8: -C (= O) -NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-OC (= O)-
L11: -O-AL-
L12: -O-AL-O-
L13: -O-AL-OC (= O)-

L14: -O-AL-OC (= O) -NH-AL-
L15: -O-AL-S-AL-
L16: -OC (= O) -AL-AR-O-AL-OC (= O)-
L17: -OC (= O) -AR-O-AL-C (= O)-
L18: -OC (= O) -AR-O-AL-OC (= O)-
L19: -OC (= O) -AR-O-AL-O-AL-OC (= O)-
L20: -OC (= O) -AR-O-AL-O-AL-O-AL-OC (= O)-
L21: -S-AL-
L22: -S-AL-O-
L23: -S-AL-OC (= O)-
L24: -S-AL-S-AL-
L25: -S-AR-AL-

The polymerizable group (Q) of the general formula (ID) is not particularly limited, and can be determined according to the type of polymerization reaction when the biaxial liquid crystal composition of the present invention is polymerized.
Examples of the polymerizable group (Q) include examples (Q-1) to (Q-17) of the polymerizable group that the rod-like liquid crystal compound represented by the general formula (IC) has. Among these, the polymerizable group (Q) is preferably an unsaturated polymerizable group (Q-1) to (Q-7), an epoxy group (Q-8) or an aziridinyl group (Q-9). A saturated polymerizable group is more preferable, and an ethylenically unsaturated polymerizable group (Q-1) to (Q-6) is most preferable.

In the general formula (ID), n is an integer of 4 to 12. A specific number is determined according to the type of discotic core (D).
In the general formula (ID), a plurality of combinations of L and Q may be different but are preferably the same. Two or more kinds of discotic liquid crystalline compounds may be used in combination. For example, a molecule having a polymerizable group (Q) and a molecule not having it may be used in combination.

  The non-polymerizable discotic liquid crystal compound is preferably a compound in which the polymerizable group (Q) of the polymerizable discotic liquid crystal compound described above is changed to a hydrogen atom or an alkyl group. That is, the non-polymerizable discotic liquid crystal compound is preferably a compound represented by the following formula.

    D (-LR) n

In the formula, D is a discotic core, L is a divalent linking group, R is a hydrogen atom or an alkyl group, and n is an integer of 4 to 12.
The example of the discotic core (D) of the above formula is the same as the example of the polymerizable discotic liquid crystal compound except that LQ (or QL) is changed to LR (or RL). Examples of the divalent linking group (L) are the same as the examples of the polymerizable discotic liquid crystal compound.
The alkyl group for R preferably has 1 to 40 carbon atoms, and more preferably 1 to 30 carbon atoms. A chain alkyl group is preferred to a cyclic alkyl group, and a linear alkyl group is preferred to a branched chain alkyl group. R is particularly preferably a hydrogen atom or a linear alkyl group having 1 to 30 carbon atoms.

[Liquid crystal composition]
The liquid crystal temperature range of the biaxial liquid crystal composition of the present invention is not particularly limited, but it is preferably within the range of 10 to 250 ° C. from the viewpoint of application of the liquid crystal composition, such as the production suitability of the retardation plate, More preferably, it exists in the range of 10-150 degreeC. When the temperature is lower than 10 ° C., a cooling step or the like may be required to lower the temperature to a temperature range exhibiting a liquid crystal phase. Further, when the temperature exceeds 200 ° C., a high temperature is required to make the isotropic liquid state higher than the temperature range once exhibiting the liquid crystal phase, which is disadvantageous from waste of heat energy, deformation of the substrate, and alteration.

The biaxial liquid crystal composition of the present invention can be fixed without impairing the alignment form in the liquid crystal state by once heating to the liquid crystal phase formation temperature and then cooling while maintaining the alignment state. .
Further, when at least one of the liquid crystal compound and the refractive index control agent has a polymerizable group, a polymerization initiator described later may be added as necessary, and the composition may be polymerized to obtain a polymer. It is preferable for fixing the alignment state. The polymer can be obtained by heating the composition to the liquid crystal phase formation temperature and polymerizing it, and then cooling it, so that it can be obtained as a polymer maintaining the biaxiality of the liquid crystal state, and as a layer having optical anisotropy. It can be used for various optical films such as a phase difference plate.
In the present invention, the state in which the orientation state is fixed is a state in which the orientation is maintained, which is the most typical and preferred embodiment, but is not limited thereto. Specifically, the state is usually 0 ° C. to 50 ° C. Under more severe conditions, in a temperature range of −30 ° C. to 70 ° C., there is no fluidity, and there is no change in the orientation form due to an external field or external force, and the immobilized orientation form is kept stable. It refers to a state that can be done.
When the alignment state is finally fixed, the liquid crystal composition of the present invention no longer needs to exhibit liquid crystallinity. For example, a low-molecular biaxial liquid crystal compound has a group that reacts with heat, light, etc., resulting in polymerization or crosslinking by reaction with heat, light, etc., resulting in a high molecular weight and loss of liquid crystallinity. Also good.

[Phase difference plate]
The retardation plate of the present invention can be produced by forming an optically anisotropic layer on the alignment film provided on the transparent support, using the biaxial liquid crystal composition of the present invention.
Here, the optically anisotropic layer is added with other additives as necessary to the biaxial liquid crystal composition of the present invention, and the composition is applied on the alignment film, and then in the liquid crystal state as described above. It can be obtained by fixing in an oriented state.
The thickness of the optically anisotropic layer formed from the biaxial liquid crystal composition is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and 1 to 10 μm. Is most preferred.
When the optically anisotropic layer is formed, the ratio (mass ratio) between the liquid crystal compound and the refractive index control agent in the biaxial liquid crystal composition is preferably 1: 2 to 100: 1, and 2: 1 to 2: 1. More preferably, it is 20: 1.

[Additive for optically anisotropic layer]
Examples of additives that can be added to the biaxial liquid crystal composition in forming the optically anisotropic layer include an air interface alignment controller, a repellency inhibitor, a polymerization initiator, and a polymerizable monomer.

[Air interface alignment control agent]
The liquid crystal compound is aligned at the air interface at the pretilt angle of the air interface. There are three types of pretilt angles: a pretilt angle formed by the nx refractive index direction and the air interface, a pretilt angle formed by the ny refractive index direction and the air interface, and a pretilt angle formed by the nz refractive index direction and the air interface. Since the degree of this pretilt angle varies depending on the type of compound, it is necessary to arbitrarily control the pretilt angle at the air interface according to the purpose.
For controlling the pretilt angle, for example, an external field such as an electric field or a magnetic field or an additive can be used, but an additive is preferably used.
Examples of such an additive include a substituted or unsubstituted aliphatic group having 6 to 40 carbon atoms, or a substituted or unsubstituted aliphatic substituted oligosiloxanoxy group having 6 to 40 carbon atoms in the molecule. A compound having at least two is preferred, and a compound having at least two in the molecule is more preferred.

  The addition amount of the alignment control additive on the air interface side is preferably 0.001% by mass to 20% by mass, more preferably 0.01% by mass to 10% by mass, and 0.1% by mass with respect to the liquid crystal compound. % To 5% by mass is most preferred.

[Anti-repellent agent]
As a material for adding to the biaxial liquid crystal composition and preventing repelling at the time of application of the composition, generally, a polymer compound can be suitably used.
The polymer to be used is not particularly limited as long as the tilt angle change and orientation of the liquid crystal compound are not significantly inhibited.
Examples of the polymer are described in JP-A-8-95030, and particularly preferred specific polymer examples include cellulose esters. Examples of cellulose esters include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. The addition amount of the polymer used for the purpose of preventing repellency is generally in the range of 0.1 to 10% by mass with respect to the liquid crystal compound so as not to disturb the alignment of the compound exhibiting the biaxial liquid crystal. More preferably, it is in the range of 8% by mass, and even more preferably in the range of 0.1-5% by mass.

[Polymerization initiator]
In the present invention, the liquid crystal compound is preferably fixed in a monodomain alignment, that is, in a substantially uniformly aligned state. Therefore, when a polymerizable liquid crystal compound is used, the liquid crystal compound is converted by a polymerization reaction. It is preferable to fix.
The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator, a photopolymerization reaction using a photopolymerization initiator, and a polymerization reaction by electron beam irradiation. In order to prevent the support and the like from being deformed or altered by heat. Also, a photopolymerization reaction and a polymerization reaction by electron beam irradiation are preferable.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).
The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the optically anisotropic layer coating solution.
It is preferable to use ultraviolet rays for light irradiation for polymerization. The irradiation energy is preferably 10mJ~50J / cm ^2, further preferably 50mJ~800mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. Further, since the oxygen concentration in the atmosphere is related to the degree of polymerization, when the desired degree of polymerization is not reached in the air, it is preferable to reduce the oxygen concentration by a method such as nitrogen substitution. A preferable oxygen concentration is preferably 10% or less, more preferably 7% or less, and most preferably 3% or less.

[Polymerizable monomer]
The polymerizable monomer that can be used in the present invention is not particularly limited as long as it is compatible with the liquid crystal compound and does not significantly change the tilt angle of the liquid crystal compound or inhibit alignment. Among these, compounds having a polymerization active ethylenically unsaturated group such as a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group are preferably used.
The addition amount of the polymerizable monomer is generally in the range of 0.5 to 50% by mass and preferably in the range of 1 to 30% by mass with respect to the liquid crystal compound. In addition, it is particularly preferable to use a monomer having two or more reactive functional groups because an effect of improving the adhesion between the alignment film and the optically anisotropic layer can be expected.

[Coating solvent]
As the solvent used for the preparation of the biaxial liquid crystal composition, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, toluene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides, esters and ketones are preferred. Two or more organic solvents may be used in combination.

[Application method]
The optically anisotropic layer is formed by preparing a biaxial liquid crystal composition coating solution using the above solvent, coating the alignment film on the alignment film, and orienting the biaxial liquid crystal compound. The coating liquid can be applied by a known method (for example, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, or a die coating method).

[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). , 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.
As long as the desired orientation can be imparted to the liquid crystal compound of the optically anisotropic layer provided on the alignment film, the alignment film may be any layer, but in the present invention, it is formed by rubbing treatment or light irradiation. An alignment film is preferred. An alignment film formed by a polymer rubbing treatment is particularly preferable. The rubbing treatment can be generally carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. In the present invention, in particular, by the method described in the liquid crystal manual (Maruzen Co., Ltd.). Preferably it is done. The thickness of the alignment film is preferably 0.01 to 10 μm, and more preferably 0.05 to 3 μm.
The polymer used for the alignment film is described in many documents, and many commercially available products can be obtained. For the alignment film used in the retardation plate of the present invention, polyvinyl alcohol and its derivatives are preferably used. Particularly preferred is a modified polyvinyl alcohol to which a hydrophobic group is bonded. As the alignment film, an alignment film used for a discotic liquid crystal can be used as an alignment film for a biaxial liquid crystal. As such an alignment film, reference can be made to the description on page 43, line 24 to page 49, line 8 of WO01 / 88574A1.

(Rubbing density of alignment film)
Since there is a relationship between the rubbing density of the alignment film and the pretilt angle of the liquid crystal compound at the interface of the alignment film, the pretilt angle decreases as the rubbing density increases, and the pretilt angle increases as the rubbing density decreases. By changing the rubbing density, the pretilt angle can be adjusted.
As a method for changing the rubbing density of the alignment film, a method described in Liquid Crystal Handbook (Maruzen Co., Ltd.) can be used. The rubbing density (L) is quantified by the formula (A).

  Formula (A) L = Nl (1 + 2πrn / 60v)

  In the formula (A), N is the number of rubbing, l is the contact length of the rubbing roller, r is the radius of the roller, n is the number of rotations (rpm) of the roller, and v is the stage moving speed (second speed).

  In order to increase the rubbing density, the rubbing frequency should be increased, the contact length of the rubbing roller should be increased, the radius of the roller should be increased, the rotation speed of the roller should be increased, and the stage moving speed should be decreased, while the rubbing density should be decreased. To do this, you can reverse this.

[Transparent support]
The transparent support of the retardation plate of the present invention is not particularly limited as long as it is mainly optically isotropic and has a light transmittance of 80% or more, but a polymer film is preferred.
Specific examples of the polymer include cellulose esters (eg, cellulose diacetate, cellulose triacetate), norbornene polymers, poly (meth) acrylate ester films, etc., and many commercially available polymers are preferably used. Is possible. Among these, cellulose esters are preferable from the viewpoint of optical performance, and lower fatty acid esters of cellulose are more preferable. The lower fatty acid is a fatty acid having 6 or less carbon atoms, and the number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose triacetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. In addition, even a conventionally known polymer such as polycarbonate or polysulfone, which easily develops birefringence, should have a decreased expression by modifying the molecule described in WO00 / 26705. You can also.

Hereinafter, the cellulose ester (especially cellulose) preferably used as the transparent support will be described in detail.
As the cellulose ester, it is preferable to use cellulose acetate having an acetylation degree of 55.0 to 62.5%. In particular, the acetylation degree is preferably 57.0 to 62.0%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM D-817-91 (test method for cellulose acetate and the like).
The viscosity average polymerization degree (DP) of the cellulose ester is preferably 250 or more, and more preferably 290 or more. The cellulose ester used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, and most preferably 1.4 to 1.6. preferable.
In cellulose ester, the hydroxyl groups at the 2nd, 3rd, and 6th positions of cellulose are not evenly distributed by 1/3 of the total substitution degree, and the substitution degree of the 6th hydroxyl group tends to be small. It is preferable that the substitution degree of the 6-position hydroxyl group of cellulose is larger than the 2-position and 3-position. The hydroxyl group at the 6-position with respect to the total substitution degree is preferably 30% or more and 40% or less and is preferably substituted with an acyl group, more preferably 31% or more, and particularly preferably 32% or more. The substitution degree at the 6-position is preferably 0.88 or more. The 6-position hydroxyl group may be substituted with an acyl group having 3 or more carbon atoms (eg, propionyl, butyryl, valeroyl, benzoyl, acryloyl) in addition to the acetyl group. The degree of substitution at each position can be determined by NMR. Cellulose esters having a high degree of substitution at the 6-position hydroxyl group are described in Synthesis Example 1 described in paragraph Nos. 0043 to 0044 of JP-A No. 11-5851, Synthesis Example 2 described in paragraph Nos. 0048 to 0049, and paragraph numbers 0051 to 0052. It can be synthesized with reference to the method of Synthesis Example 3 described.

In order to adjust the retardation of a polymer film used as a transparent support, particularly a cellulose acetate film, an aromatic compound having at least two aromatic rings can be used as a retardation increasing agent. When using such a retardation increasing agent, a retardation increasing agent is used in 0.01-20 mass parts with respect to 100 mass parts of cellulose acetate. The retardation increasing agent is preferably used in a range of 0.05 to 15 parts by mass, and more preferably in a range of 0.1 to 10 parts by mass with respect to 100 parts by mass of cellulose acetate. Two or more aromatic compounds may be used in combination.
The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, More preferred are a benzene ring and a 1,3,5-triazine ring. It is particularly preferred that the aromatic compound has at least one 1,3,5-triazine ring.

The number of aromatic rings that the aromatic compound has is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. .
The bonding relationship between two aromatic rings can be classified into (a) when forming a condensed ring, (b) when directly connecting with a single bond, and (c) when connecting via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c). Such retardation increasing agents are described in WO01 / 88574A1, WO00 / 2619A1, JP-A Nos. 2000-1111914, 2000-275434, 2002-363343 and the like.

The cellulose acetate film is preferably produced by a solvent cast method from the prepared cellulose acetate solution (dope). The above-mentioned retardation increasing agent may be added to the dope.
The dope is cast on a drum or band, and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. Regarding casting and drying methods in the solvent casting method, U.S. Pat. Nos. 2,336,310, 2,367,603, 2,429,078, 2,429,297, 2,429,978, 2,607,704, 2,37,069, 2,273,070, British Patent 6,407,331, No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.
The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried by high-temperature air whose temperature is successively changed from 100 ° C. to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

The prepared cellulose acetate solution (dope) can be used to form a film by casting two or more layers of the dope. The dope is cast on a drum or band, and the solvent is evaporated to form a film. The dope before casting is preferably adjusted in concentration so that the solid content is 10 to 40%. The surface of the drum or band is preferably finished in a mirror state.
When casting a plurality of cellulose acetate solutions, a solution containing cellulose acetate is cast from a plurality of casting openings provided at intervals in the traveling direction of the support, and a film is produced while laminating them. May be. For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be used. Alternatively, the cellulose acetate solution may be cast from two casting ports to form a film. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-61-104413, JP-A-61-158413, and JP-A-6-134933. The method described in the publication can be used. Also, a cellulose acetate film casting method in which a flow of a high-viscosity cellulose acetate solution is wrapped in a low-viscosity cellulose acetate solution and the high-viscosity and low-viscosity cellulose acetate solutions are simultaneously extruded as described in JP-A-56-162617. A method may be used.

  The retardation of the cellulose acetate film can be further adjusted by stretching treatment. The draw ratio is preferably in the range of 0 to 100%. When stretching the cellulose acetate film of the present invention, tenter stretching is preferably used, and in order to control the slow axis with high accuracy, the difference between the left and right tenter clip speeds, the separation timing, etc. can be made as small as possible. preferable.

  A plasticizer can be added to the cellulose ester film in order to improve mechanical properties or increase the drying speed. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalate esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and di-2-ethylhexyl phthalate (DEHP). . Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The addition amount of the plasticizer is preferably 0.1 to 25% by mass of the amount of cellulose ester, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass.

Degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) and UV inhibitors may be added to the cellulose ester film. The deterioration inhibitors are described in JP-A-3-199201, JP-A-597073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the added amount exceeds 1% by mass, bleeding-out (bleeding) of the deterioration preventing agent to the film surface may be observed.
As a particularly preferred example of the deterioration preventing agent, butylated hydroxytoluene (BHT) can be mentioned. The ultraviolet ray preventing agent is described in JP-A-7-11056.

The cellulose acetate film is preferably subjected to a surface treatment. Specific examples include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. In addition, as described in JP-A-7-333433, it is preferable to provide an undercoat layer.
From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film in these treatments is preferably Tg (glass transition temperature) or less, specifically 150 ° C. or less.

As for the surface treatment of the cellulose acetate film, it is particularly preferable to carry out an acid treatment or an alkali treatment, that is, a saponification treatment for cellulose acetate, from the viewpoint of adhesion to an alignment film or the like.
Hereinafter, the alkali saponification treatment will be specifically described as an example.
The alkali saponification treatment is preferably performed in a cycle in which the film surface is immersed in an alkali solution, neutralized with an acidic solution, washed with water and dried. Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution. The specified concentration of hydroxide ions is preferably in the range of 0.1 to 3.0N, and more preferably in the range of 0.5 to 2.0N. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 to 70 ° C.

  The surface energy of the cellulose acetate film is preferably 55 mN / m or more, and more preferably in the range of 60 to 75 mN / m.

  The thickness of the cellulose acetate film is usually preferably in the range of 5 to 500 μm, preferably in the range of 20 to 250 μm, more preferably in the range of 30 to 180 μm, and particularly preferably in the range of 30 to 110 μm.

[Use of retardation plate]
The retardation plate of the present invention can be used for an elliptically polarizing plate in combination with a polarizing film. Furthermore, by applying to a transmission type liquid crystal display device in combination with a polarizing film, it contributes to an increase in viewing angle.
The elliptically polarizing plate and liquid crystal display device using the retardation plate of the present invention will be described below.

[Elliptically polarizing plate]
An elliptically polarizing plate can be produced by laminating the retardation plate of the present invention and a polarizing film. By using the retardation plate of the present invention, an elliptically polarizing plate capable of expanding the viewing angle of a liquid crystal display device can be provided.
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 produced using a polyvinyl alcohol film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the film stretching direction.

  The polarizing film is laminated on the optically anisotropic layer side of the retardation plate. It is preferable to form a transparent protective film on the surface opposite to the side on which the retardation film of the polarizing film is laminated. The transparent protective film preferably has a light transmittance of 80% or more. As the transparent protective film, generally a cellulose ester film, preferably a triacetyl cellulose film is used. The cellulose ester film is preferably formed by a solvent cast method. The thickness of the transparent protective film is preferably 20 to 500 μm, and more preferably 50 to 200 μm.

[Liquid Crystal Display]
By using the retardation plate of the present invention, a liquid crystal display device with an enlarged viewing angle can be provided. TN mode liquid crystal cell retardation plates (optical compensation sheets) are described in JP-A-6-214116, US Pat. Nos. 5,583,679, 5,646,703, and German Patent 3,911,620A1. Further, an optical compensation sheet for liquid crystal cells in IPS mode or FLC mode is described in JP-A-10-54982. Furthermore, OCB mode or HAN mode liquid crystal cell optical compensation sheets are described in US Pat. No. 5,805,253 and International Publication No. WO96 / 37804. Furthermore, an optical compensation sheet for an STN mode liquid crystal cell is described in JP-A-9-26572. A VA mode liquid crystal cell optical compensation sheet is described in Japanese Patent No. 2866372.

In the present invention, liquid crystal cell retardation plates (optical compensation sheets) of various modes can be prepared with reference to the above-mentioned publications. The retardation plate of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Super Twisted Nematic), VA (Vertically Aligned), and HAN. It can be used for liquid crystal display devices of various display modes such as (Hybrid Aligned Nematic) mode.
The liquid crystal display device includes a liquid crystal cell, a polarizing element, and a phase difference plate (optical compensation sheet). A polarizing element generally comprises a polarizing film and a protective film. As the polarizing film and the protective film, those described for the elliptically polarizing plate can be used.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these specific examples.

Example 1 Effect of Refractive Index Control Agent Satisfying Formula (I) (Preparation of Liquid Crystal Composition)
A biaxial liquid crystal composition is obtained by dissolving 1 g of the biaxial liquid crystal compound (m-3) and 0.2 g of the refractive index control agent (I-1) in acetone and then removing the acetone under reduced pressure.

(Confirmation of biaxiality)
This biaxial liquid crystal composition is put into an alignment cell in which the rubbing direction is assembled in antiparallel, and conoscopic observation is performed under a polarizing microscope at the liquid crystal temperature. In addition, when only the biaxial liquid crystal compound (m-3) is placed in an alignment cell assembled in antiparallel, conoscopic observation is performed under a polarizing microscope at the liquid crystal temperature, and the patterns obtained from both are compared biaxially. It can be confirmed that there is a difference in sex, and the relationship is (nx−ny) / (ny−nz)> (nx0−ny0) / (ny0−nz0).

[Example 2] Production of retardation plate (production of transparent support)
The following components are put into a mixing tank and heated and stirred to prepare a cellulose acetate solution (dope).

(Cellulose acetate solution composition)
Cellulose acetate having an acetylation degree of 60.9% 100 parts by mass Triphenyl phosphate 6.5 parts by mass Biphenyl diphenyl phosphate 5.2 parts by mass The following retardation increasing agent (1) 0.1 part by mass The following retardation increasing agent ( 2) 0.2 parts by mass Methylene chloride 310.25 parts by mass Methanol 54.75 parts by mass 1-butanol 10.95 parts by mass

  The dope is cast from a casting port onto a drum cooled to 0 ° C. The film is peeled off in a state where the solvent content is 70% by mass, both ends in the width direction of the film are fixed with a pin tenter, and the stretch rate in the width direction (direction perpendicular to the longitudinal direction) in the region where the solvent content is 3 to 5% by mass. Is dried while maintaining an interval of 3%. Then, it is further dried by transporting between the rolls of the heat treatment apparatus, and the stretch ratio in the longitudinal direction is substantially 0% in a region exceeding 120 ° C. (in consideration of stretching by 4% in the longitudinal direction when stripping) A cellulose acetate film having a thickness of 100 μm is prepared by adjusting the ratio of the stretching ratio in the width direction to the stretching ratio in the machine direction to be 0.75. When the retardation of the produced film was measured at a wavelength of 632.8 nm, the retardation in the thickness direction was 40 nm and the in-plane retardation was 4 nm. The produced cellulose acetate film is used as a transparent support.

(Formation of first undercoat layer)
On the transparent support, a coating solution having the following composition is coated at 28 ml / m ² and dried to form a first undercoat layer.

(First undercoat layer coating solution composition)
Gelatin 5.42 parts by mass Formaldehyde 1.36 parts by mass Salicylic acid 1.60 parts by mass Acetone 391 parts by mass Methanol 158 parts by mass Methylene chloride 406 parts by mass Water 12 parts by mass

(Formation of second undercoat layer)
On the first undercoat layer, 7 ml / m ² of a coating solution having the following composition is applied and dried to form a second undercoat layer.

(Second undercoat layer coating solution composition)
The following anionic polymer 0.79 parts by mass Citric acid monoethyl ester 10.1 parts by mass Acetone 200 parts by mass Methanol 877 parts by mass Water 40.5 parts by mass

(Formation of back layer)
On the surface of the transparent support opposite to the surface on which the undercoat layer is provided, a coating solution having the following composition is applied at 25 ml / m ² and dried to form a back layer.

(Back layer coating solution composition)
Cellulose diacetate with an acetylation degree of 55% 6.56 parts by mass Silica matting agent (average particle size: 1 μm) 0.65 parts by mass Acetone 679 parts by mass Methanol 104 parts by mass

(Formation of alignment film)
The following modified polyvinyl alcohol and glutaraldehyde (5% by mass of modified polyvinyl alcohol) are dissolved in a methanol / water mixed solvent (volume ratio = 20/80) to prepare a 5% by mass solution.

  This solution is applied onto the second undercoat layer, dried with hot air at 100 ° C. for 120 seconds, and then rubbed to form an alignment film. The obtained alignment film has a thickness of 0.5 μm. The rubbing direction of the alignment film is parallel to the casting direction of the transparent support.

(Formation of optically anisotropic layer)
An optically anisotropic layer coating solution having the following composition is applied onto the alignment film subjected to the rubbing treatment as described above using a # 4 wire bar.

(Optically anisotropic layer coating solution)
Biaxial liquid crystalline compound m-3 100 parts by mass Refractive index control agent I-1 20 parts by mass The following air interface alignment controller V- (1) 0.2 part by mass The following photopolymerization initiator HJ-1 2.0 Parts by mass Lucirin TPO-L (BASF (manufactured)) 2.0 parts by mass methyl ethyl ketone 300 parts by mass

The film coated with the above optically anisotropic layer is placed in a thermostatic bath at 60 ° C., heated until the film temperature reaches 50 ° C. over about 20 seconds, held as it is for 1 minute, and then oxygen concentration 2 % Is placed in a constant temperature bath at 60 ° C., and after 30 seconds, ultraviolet light of 600 mJ / cm ² is irradiated to fix the orientation state of the optically anisotropic layer. Then, it cools to room temperature and produces a phase difference plate. The thickness of the optically anisotropic layer is 1.82 μm.
Bipolarity and tilt angle in the optically anisotropic layer of the resulting retardation plate are determined with a polarizing microscope equipped with a free pedestal. The optically anisotropic layer exhibits biaxiality and is most refracted. It can be confirmed that the direction in which the rate is small substantially coincides with the normal direction of the transparent support and that the direction hardly changes in the thickness direction of the transparent support.

Example 3 Effect of Refractive Index Control Agent Satisfying Formula (II) (Preparation of Liquid Crystal Composition)
A biaxial liquid crystal composition is obtained by dissolving 1 g of the biaxial liquid crystal compound (m-3) and 0.2 g of the refractive index control agent (D-1) in acetone and then removing the acetone under reduced pressure.

[Confirmation of biaxiality]
This biaxial liquid crystal composition is put into an alignment cell in which the rubbing direction is assembled in antiparallel, and conoscopic observation is performed under a polarizing microscope at the liquid crystal temperature. In addition, when only the biaxial liquid crystal compound (m-3) is placed in an alignment cell assembled in antiparallel, conoscopic observation is performed under a polarizing microscope at the liquid crystal temperature, and the patterns obtained from both are compared biaxially. It can be confirmed that there is a difference in sex, and the relationship is (nx−ny) / (ny−nz) <(nx0−ny0) / (ny0−nz0).

Example 4 Production of Retardation Plate On the alignment film produced in Example 2, an optically anisotropic layer coating solution having the following composition is applied using a # 4 wire bar.

(Optically anisotropic layer coating solution)
Biaxial liquid crystalline compound m-3 100 parts by mass Refractive index control agent D-1 20 parts by mass The air interface alignment controller V- (1) 0.2 parts by mass The photopolymerization initiator HJ-1 2.0 parts by mass Part Lucirin TPO-L (BASF (made)) 2.0 parts by mass Methyl ethyl ketone 300 parts by mass

The film coated with the above optically anisotropic layer is placed in a thermostatic bath at 60 ° C., heated until the film temperature reaches 50 ° C. over about 20 seconds, held as it is for 1 minute, and then oxygen concentration 2 % Is placed in a constant temperature bath at 60 ° C., and after 30 seconds, ultraviolet light of 600 mJ / cm ² is irradiated to fix the orientation state of the optically anisotropic layer. Then, it cools to room temperature and produces a phase difference plate. The thickness of the optically anisotropic layer is 1.82 μm.
Bipolarity and tilt angle in the optically anisotropic layer of the resulting retardation plate are determined with a polarizing microscope equipped with a free pedestal. The optically anisotropic layer exhibits biaxiality and is most refracted. It can be confirmed that the direction in which the rate is small substantially coincides with the normal direction of the transparent support and that the direction hardly changes in the thickness direction of the transparent support.

Claims (14)

  A biaxial liquid crystal composition that includes a liquid crystal compound and a refractive index control agent and expresses a biaxial liquid crystal phase, wherein the refractive index in the triaxial direction of the biaxial liquid crystal composition is nx, ny, When the refractive index in the triaxial direction of the biaxial composition obtained by excluding the refractive index control agent from the biaxial liquid crystal composition is nx0, ny0, nz0 in descending order, (nx−ny) A biaxial liquid crystal composition having different values of / (ny-nz) and (nx0-ny0) / (ny0-nz0). The biaxial liquid crystal according to claim 1, wherein the values of (nx-ny) / (ny-nz) and (nx0-ny0) / (ny0-nz0) satisfy the following formula (I): Composition.
Formula (I)
(Nx-ny) / (ny-nz)> (nx0-ny0) / (ny0-nz0)   The biaxial liquid crystal composition according to claim 1 or 2, wherein the refractive index control agent contains a compound having a rod-like shape. The biaxial liquid crystal composition according to claim 1, wherein the refractive index control agent is represented by the following general formula (IC).
General formula (IC)
Q1-L1-Cy1-L2- (Cy2-L3) n-Cy3-L4-Q2
In general formula (IC), Q1 and Q2 are each independently a polymerizable group, L1 and L4 are each independently a divalent linking group, and L2 and L3 are each independently a single bond or a divalent linking group. Cy1, Cy2 and Cy3 are each independently a divalent cyclic group, and n is 0, 1 or 2. The biaxial liquid crystal composition according to claim 1, wherein the values of (nx-ny) / (ny-nz) and (nx0-ny0) / (ny0-nz0) satisfy the following formula (II): Stuff.
Formula (II)
(Nx-ny) / (ny-nz) <(nx0-ny0) / (ny0-nz0)   The biaxial liquid crystal composition according to claim 1 or 5, wherein the refractive index control agent contains a compound having a disc-like shape. The biaxial liquid crystal composition according to claim 1, wherein the refractive index control agent is represented by the following general formula (ID).
General formula (ID)
D (-LQ) n
In general formula (ID), D is a discotic core, L is a divalent linking group, Q is a polymerizable group, and n is an integer of 4 to 12.   The biaxial liquid crystal composition according to claim 1, wherein the refractive index control agent exhibits a liquid crystal phase.   The biaxial liquid crystal composition according to claim 1, wherein the liquid crystal compound has a polymerizable group.   The biaxial liquid crystal composition according to claim 1, wherein the refractive index control agent has a polymerizable group.   The biaxial liquid crystal composition according to any one of claims 1 to 10, wherein the biaxial liquid crystal phase expressed by the biaxial liquid crystal composition is a biaxial nematic liquid crystal phase.   A biaxial liquid crystal composition according to any one of claims 1 to 11, which is a retardation plate having an alignment film and at least one optically anisotropic layer on a transparent support. A phase difference plate, which is a layer formed from a material.   An elliptically polarizing plate comprising the retardation plate according to claim 12 and a polarizing film.   A polymer obtained by polymerizing the biaxial liquid crystal composition according to claim 9.