JP2000105316A - Optical compensating sheet, stn type liquid crystal display device and aligning method of discotic liquid crystalline molecule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably align discotic liquid crystalline molecules in a substantially perpendicular and uniform direction and to obtain an optical compensation sheet suitable for an STN type liquid crystal display device. SOLUTION: A polymer or fluorine-contg. polymer having >10C hydrocarbon groups on the side chains is added to an alignment film 22 to align the discotic liquid crystalline molecules at the average tilt angle of 50 deg. to 90 deg.. The discotic liquid crystalline molecules are twisted, and a twisted angle range is preferably between 90 deg. and 360 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical compensatory sheet having, in this order, an alignment film and an optically anisotropic layer formed from discotic liquid crystalline molecules on a transparent support.
The present invention also relates to an STN liquid crystal display device. Furthermore, the present invention relates to a method for aligning discotic liquid crystalline molecules at an average tilt angle in the range of 50 to 90 degrees.

[0002]

2. Description of the Related Art An STN type liquid crystal display device comprises an STN type liquid crystal cell, two polarizing plates, and one or two optical compensation sheets (retardation plates) provided between the STN type liquid crystal cell and the polarizing plate. Consists of The liquid crystal cell is composed of rod-like liquid crystal molecules, two substrates for enclosing the same, and an electrode layer for applying a voltage to the rod-like liquid crystal molecules. In the STN type liquid crystal cell, an alignment film for aligning rod-like liquid crystal molecules is provided on two substrates. Further, using a chiral agent, the rod-like liquid crystalline molecules are twisted at 180 to 360 degrees. In an STN type liquid crystal display device without an optical compensation sheet,
The display image is colored blue or yellow due to the birefringence of the rod-like liquid crystal molecules. Coloring of the displayed image is inconvenient in both monochrome display and color display. The optical compensation sheet is used to eliminate such coloring and obtain a bright and clear image. In some cases, the optical compensation sheet may be provided with a function of expanding the viewing angle of the liquid crystal cell. As the optical compensation sheet, a stretched birefringent film has been conventionally used. An optical compensatory sheet for an STN type liquid crystal display device using a stretched birefringent film is disclosed in
Nos. 104284 and 7-13021.

It has been proposed to use an optical compensatory sheet having an optically anisotropic layer containing discotic liquid crystal molecules on a transparent support instead of an optical compensatory sheet comprising a stretched birefringent film. The optically anisotropic layer is formed by aligning discotic liquid crystal molecules and fixing the alignment state. Discotic liquid crystalline molecules generally have a large birefringence. The discotic liquid crystal molecules have various alignment forms. The use of discotic liquid crystal molecules makes it possible to produce an optical compensatory sheet having optical properties that cannot be obtained with a conventional stretched birefringent film. An optical compensatory sheet using discotic liquid crystal molecules is disclosed in JP-A-6-214116, US Pat.
679, 5646703 and German Patent Publication 391
It is described in each specification of No. 1620A1. However, these optical compensation sheets are designed assuming a TN type liquid crystal display device as a main use.

It is conceivable that an optical compensation sheet using discotic liquid crystal molecules is used for an STN type liquid crystal display device. In the STN-type liquid crystal display device, rod-like liquid crystal molecules having a super-twist orientation larger than 90 ° are used in the birefringence mode. The STN-type liquid crystal display device has a feature that even in a simple matrix electrode structure having no active element (thin film transistor or diode), a large capacity clear display is possible by time division driving. In order to optically compensate an STN-type liquid crystal cell using discotic liquid crystal molecules, it is necessary to align the discotic liquid crystal molecules substantially vertically (homogeneous alignment). Preferably, the discotic liquid crystalline molecules are further twisted. Japanese Patent Application Laid-Open No. 9-26572 discloses an optical compensation sheet in which discotic liquid crystal molecules are twisted and aligned. Further, the drawings of the publication show a state where the discotic liquid crystalline molecules are substantially vertically aligned.

[0005]

Problems to be Solved by the Invention
According to the technique disclosed in Japanese Patent Application Laid-Open Publication No. H11-146, it is difficult to uniformly align the discotic liquid crystal molecules from the interface of the alignment film to the air interface (monodomain alignment). If the discotic liquid crystal molecules are not uniformly aligned, light scattering occurs due to disclination, and the contrast ratio of a displayed image decreases. Research is also being conducted on a technique for aligning rod-like liquid crystal molecules used in a liquid crystal cell substantially vertically (homeotropic alignment). For example, vertical alignment (vertical alignment) in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when voltage is applied.
ent) In a liquid crystal cell of a liquid crystal mode, an alignment film for aligning rod-like liquid crystalline molecules substantially vertically is required. Various alignment films have been proposed for rod-like liquid crystal molecules. The rod-shaped liquid crystal molecules and the discotic liquid crystal molecules have completely different molecular structures and optical properties. Regarding the vertical alignment, discotic liquid crystal molecules are different from rod-shaped liquid crystal molecules in that not only the liquid crystal molecules need to be vertically aligned but also the discotic liquid crystal molecules need to be aligned in a certain direction (the directionality is necessary). As a result of research conducted by the present inventors, most of alignment films known as vertical alignment films of rod-like liquid crystal molecules did not show a function of aligning discotic liquid crystal molecules in a vertical and uniform direction.

An object of the present invention is to provide an optical compensation sheet particularly suitable for an STN type liquid crystal display device. Another object of the present invention is to provide an STN-type liquid crystal display device in which coloring of a display image is eliminated and a clear image with high contrast is obtained. Further, the object of the present invention is
Another object is to provide a method for stably aligning discotic liquid crystal molecules in a vertical and uniform direction.

[0007]

An object of the present invention is to provide an optical compensatory sheet of the following (1) to (4) and (7) to (10) and an STN type liquid crystal display of the following (5) and (11). And the following (6) and (7) methods for aligning discotic liquid crystalline molecules. (1) An optical compensation sheet having, in this order, an alignment film and an optically anisotropic layer formed from discotic liquid crystalline molecules on a transparent support, wherein the alignment film has 10 or more carbon atoms in a side chain. An optical compensatory sheet comprising a polymer having a hydrocarbon group, wherein the discotic liquid crystalline molecules are oriented at an average tilt angle in the range of 50 to 90 degrees. (2) The main chain of the polymer has a polyimide structure (1)
4. The optical compensation sheet according to item 1. (3) The optical compensation sheet according to (1), wherein the polymer has a steroid structure in a main chain or a side chain. (4) The optical compensatory sheet according to (1), wherein the discotic liquid crystal molecules are twisted and the twist angle is in a range of 90 to 360 degrees.

(5) STN liquid crystal cell, two polarizing plates disposed on both sides thereof, and one or two optical compensation sheets disposed between the STN liquid crystal cell and one or both polarizing plates An STN type liquid crystal display device comprising:
The optical compensation sheet has a transparent support, an alignment film, and an optically anisotropic layer formed from discotic liquid crystalline molecules in this order from the polarizing plate side, and the alignment film has 1 carbon atom in a side chain.
A discotic liquid crystalline molecule is oriented at an average tilt angle in the range of 50 to 90 degrees, further twisted, and has a twist angle of 9;
An STN-type liquid crystal display device characterized by being in a range of 0 to 360 degrees. (6) A method of aligning discotic liquid crystal molecules at an average tilt angle of 50 to 90 degrees using an alignment film containing a polymer having a hydrocarbon group having 10 or more carbon atoms in a side chain.

(7) An optical compensatory sheet having, in this order, an alignment film and an optically anisotropic layer formed from discotic liquid crystal molecules on a transparent support, wherein the alignment film contains a fluorine-containing polymer, An optical compensation sheet, wherein discotic liquid crystal molecules are oriented at an average inclination angle in the range of 50 to 90 degrees. (8) The optical compensation sheet according to (7), wherein the main chain of the fluoropolymer has a polyimide structure. (9) The optical compensation sheet according to (7), wherein the fluoropolymer contains 0.05 to 80% by weight of fluorine atoms. (10) The discotic liquid crystal molecules are twist-aligned, and the twist angle is in the range of 90 to 360 degrees. (7)
4. The optical compensation sheet according to item 1.

(11) STN type liquid crystal cell, two polarizing plates disposed on both sides thereof, and one or two optical compensation sheets disposed between the STN type liquid crystal cell and one or both polarizing plates An optical compensation sheet comprises a transparent support, an alignment film, and an optically anisotropic layer formed from discotic liquid crystal molecules in this order from the polarizing plate side, wherein the alignment film is An STN comprising a fluorine-containing polymer, wherein the discotic liquid crystalline molecules are oriented at an average tilt angle in the range of 50 to 90 degrees, are further twisted, and have a twist angle in the range of 90 to 360 degrees. Liquid crystal display device. (12) Using an alignment film containing a fluoropolymer, 50
A method of aligning discotic liquid crystalline molecules at an average tilt angle in a range of from 90 to 90 degrees. In this specification, the average tilt angle of the discotic liquid crystalline molecules means the average angle between the disc surface of the discotic liquid crystalline molecules and the surface of the support (or the surface of the alignment film). Then, the discotic liquid crystalline molecules are 50 to 9
A state in which the liquid crystal molecules are aligned at an average tilt angle in a range of 0 degrees is referred to as a state in which the discotic liquid crystal molecules are substantially vertically aligned.

[0011]

As a result of the research, the present inventors have found that a discotic liquid crystal molecule is substantially vertically oriented by using a polymer having a hydrocarbon group having 10 or more carbon atoms in the side chain or a fluorine-containing polymer for the alignment film. And it succeeded in stably orienting in a uniform direction. Polymers having a hydrocarbon group having 10 or more carbon atoms in the side chain (for example, some of the specific examples of polyimide described in JP-A-5-27244) and fluorine-containing polymers are used for the alignment film of rod-like liquid crystal molecules. (For example, polyimide described in JP-A-6-346055). However, most of the alignment film of rod-like liquid crystal molecules does not function as an alignment film of discotic liquid crystal molecules. As a means for stably aligning discotic liquid crystal molecules in a substantially vertical and uniform direction has been obtained, it has become possible to manufacture an optical compensation sheet suitable for an STN liquid crystal display device. By using an optical compensation sheet in which discotic liquid crystal molecules are substantially vertically aligned (preferably, further twisted), ST
Coloring of the display image of the N-type liquid crystal display device is eliminated, and a clear image with high contrast can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an alignment state of rod-like liquid crystal molecules in a liquid crystal cell and a discotic liquid crystal in an optically anisotropic layer in a pixel portion of an STN type liquid crystal display device when no voltage is applied (off). FIG. 3 is a cross-sectional view schematically illustrating an orientation state of a hydrophilic molecule. As shown in FIG. 1, the liquid crystal cell includes an upper substrate (1
1) Between the lower alignment film (12) and the upper alignment film (14) of the lower substrate (15), rod-like liquid crystal molecules (13a to 13a)
e) having a liquid crystal layer formed by encapsulation. Alignment film (1
Due to the function of 2,14) and the chiral agent added to the liquid crystal layer, the rod-like liquid crystal molecules (13a to 13e) are twisted as shown in FIG. Although omitted in FIG. 1,
The upper substrate (11) and the lower substrate (15) of the liquid crystal cell each have an electrode layer. The electrode layer is composed of rod-like liquid crystal molecules (13
It has a function of applying a voltage to a to e). When the applied voltage of the STN type liquid crystal cell is 0 (when no voltage is applied), as shown in FIG. 1, the rod-like liquid crystalline molecules (13a to 13e) are substantially parallel to the plane of the alignment films (12, 14) ( (Horizontally). Then, the rod-like liquid crystal molecules (13a to 13e) form a spiral in a horizontal plane while being twisted along the thickness direction (in FIG. 1, approximately 2 counterclockwise from 13a to 13e).
40 °). When a voltage is applied (on) to the STN-type liquid crystal cell, the rod-like liquid crystal molecules (13b to 13d) in the center of the liquid crystal cell are more vertically aligned (electric field) than when no voltage is applied (off). Rearrange parallel to the direction). The alignment state of the rod-like liquid crystal molecules (13a, 13e) near the alignment films (12, 14) does not substantially change even when a voltage is applied.

An optical compensation sheet is disposed below the liquid crystal cell. The optical compensation sheet shown in FIG. 1 has an alignment film (22) and an optically anisotropic layer on a transparent support (23) in this order. The optically anisotropic layer is a layer obtained by aligning the discotic liquid crystal molecules (21a to 21e) and fixing the molecules in the aligned state. In the present invention, as shown in FIG. 1, discotic liquid crystal molecules (21a to 21a) are used.
e) The disk surface is oriented substantially perpendicular to the surface of the alignment film (22). Then, as shown in FIG. 1, the discotic liquid crystal molecules (21a to 21e) form a spiral in a horizontal plane while being twisted along the thickness direction (in FIG. 1,
It is preferred to orient in a direction such as approximately 240 ° clockwise from 21a to 21e. In FIG. 1, rod-like liquid crystal molecules and discotic liquid crystal molecules are represented by 13a and 2a.
1e, 13b and 21d, 13c and 21c, 13d and 21
b, and 13e and 21a have a corresponding relationship. That is, the discotic liquid crystal molecules 21e optically compensate the rod-like liquid crystal molecules 13a, and similarly, the discotic liquid crystal molecules 21a optically compensate the rod-like liquid crystal molecules 13e. Each correspondence will be described with reference to FIG.

FIG. 2 is a schematic diagram showing the refractive index ellipsoids of rod-shaped liquid crystal molecules of a liquid crystal cell and discotic liquid crystal molecules of an optical compensation sheet which has a relationship of optically compensating the same. The refractive index ellipsoid (13) of the rod-like liquid crystal molecules of the liquid crystal cell has a refractive index (1) in a plane parallel to the alignment film.
3x, 13y) and the refractive index (13) in the thickness direction of the liquid crystal cell.
z). In the STN type liquid crystal cell, the refractive index (13x) in one direction in a plane parallel to the alignment film has a large value, and the refractive index (13y) in the plane perpendicular to the direction and the refractive index (13x) in the thickness direction of the liquid crystal cell (13x). 13z) is a small value. Therefore, the refractive index ellipsoid (13) has a shape in which a rugby ball is laid horizontally as shown in FIG. In such a liquid crystal cell having a non-spherical refractive index ellipsoid,
Angle dependence of birefringence occurs. This angle dependency is eliminated by using an optical compensation sheet.

The refractive index ellipsoid (21) of the discotic liquid crystalline molecules of the optical compensatory sheet which has a relationship of optically compensating the rod-like liquid crystalline molecules also has a refractive index (21x, 21y) in a plane parallel to the alignment film. It is formed by the refractive index (21z) in the thickness direction of the optically anisotropic layer. In the present invention, by aligning the discotic liquid crystal molecules substantially vertically, the refractive index (21x) in one direction in a plane parallel to the alignment film becomes a small value, and the in-plane refraction in the direction perpendicular to that direction is reduced. Rate (2
1y) and the refractive index (21z) in the thickness direction of the optically anisotropic layer
Is a large value. Therefore, the refractive index ellipsoid (21)
Has an upright disk shape as shown in FIG. From the above relationship, the retardation generated in the liquid crystal cell (1) can be offset by the optical compensation sheet (2). That is, the refractive index (13x, 13
y, 13z), the refractive index of discotic liquid crystal molecules (21x, 21y, 21z), the thickness of a rod-shaped liquid crystal molecule layer having the same director direction (13t), and the thickness of the discotic liquid crystal molecule layer (21t) If the liquid crystal display device is designed so as to satisfy the following expression, the angle dependence of the liquid crystal cell can be eliminated. │ (13x-13y) × 13t│ = │ (21x-21
y) × 21t││ (13x-13z) × 13t│ = │ (21x-21
z) × 21t |

FIG. 3 is a schematic diagram showing a layer structure of an STN type liquid crystal display device. The liquid crystal display device shown in FIG. 3A includes a lower polarizing plate (3) in order from the backlight (BL) side.
a), a lower optical compensation sheet (2a), an STN type liquid crystal cell (1), and an upper polarizing plate (3b) in this order. The liquid crystal display device shown in FIG. 3B includes, in order from the backlight (BL) side, a lower polarizing plate (3a), a lower optical compensation sheet (2a), an upper optical compensation sheet (2b), and an STN-type liquid crystal cell ( 1) and an upper polarizing plate (3b). The liquid crystal display device shown in FIG. 3C includes, in order from the backlight (BL) side, a lower polarizing plate (3a), an STN-type liquid crystal cell (1), an upper optical compensation sheet (2b), and an upper polarizing plate ( 3b). The liquid crystal display device shown in FIG. 3D includes, in order from the backlight (BL) side, a lower polarizing plate (3a), an STN-type liquid crystal cell (1), a lower optical compensation sheet (2a), and an upper optical compensation sheet ( 2b), and an upper polarizing plate (3b). The liquid crystal display device shown in FIG. 3E includes, in order from the backlight (BL) side, a lower polarizing plate (3a) and a lower optical compensation sheet (2).
a), STN type liquid crystal cell (1), upper optical compensation sheet (2)
b) and the upper polarizing plate (3b).

FIG. 3 shows the lower polarizing plate (3a) as an arrow.
, The normal (director) direction (DDa) of the discotic liquid crystal molecules near the alignment film of the lower optical compensation sheet (2a) (DDa), and the vicinity of the liquid crystal cell of the lower optical compensation sheet (2a). Direction (DDb) of discotic liquid crystal molecules in the normal direction (director), rubbing direction (RDa) of lower alignment film of liquid crystal cell (1), rubbing direction (RDb) of upper alignment film of liquid crystal cell (1) , The normal (director) direction (D) of the disc surface of the discotic liquid crystalline molecules near the liquid crystal cell of the upper optical compensation sheet (2a).
Dc), the normal (director) direction (DDd) of the discotic liquid crystal molecules near the alignment film of the upper optical compensation sheet (2a) (DDd), and the transmission axis (TAb) of the upper polarizer (3b). . The exact angles are described in FIGS. 4 and 5.

FIG. 4 is a plan view showing preferable optical directions for each element of the STN type liquid crystal display device. FIG.
Is an arrangement that emphasizes front contrast. FIG. 4 (a) shows the lower polarizing plate and ST as shown in FIG. 3 (a).
This is a case where one optical compensation sheet is provided between the liquid crystal cell and the N-type liquid crystal cell. (B) of FIG. 4, as shown in (b) of FIG.
This is a case where two optical compensation sheets are provided between the lower polarizing plate and the STN type liquid crystal cell. FIG. 4 (c) is the same as FIG. 3 (c).
As shown in (1), there is a case where one optical compensation sheet is provided between the STN type liquid crystal cell and the upper polarizing plate. FIG. 4D
FIG. 3D shows a case where two optical compensation sheets are provided between the STN type liquid crystal cell and the upper polarizing plate as shown in FIG. FIG. 4E shows one optical compensation sheet between the lower polarizing plate and the STN liquid crystal cell and between the STN type liquid crystal cell and the upper polarizing plate as shown in FIG. This is a case where one optical compensation sheet is provided in total. X is the standard (0
゜), and the meaning of each arrow is shown in FIG.
As described in the above. The transmission axis of the lower polarizing plate (TA
The arrangement may be such that a) and the transmission axis (TAb) of the upper polarizing plate are interchanged.

FIG. 5 is a plan view showing another preferred optical direction for each element of the STN type liquid crystal display device.
FIG. 5 shows an arrangement in which color is emphasized. (A) of FIG.
As shown in FIG. 3A, this is a case where one optical compensation sheet is provided between the lower polarizing plate and the STN type liquid crystal cell. FIG. 5B shows a case where two optical compensation sheets are provided between the lower polarizing plate and the STN liquid crystal cell, as shown in FIG. 3B. FIG. 5C shows a case where one optical compensation sheet is provided between the STN type liquid crystal cell and the upper polarizing plate as shown in FIG. 3C. FIG. 5D shows a case where two optical compensation sheets are provided between the STN liquid crystal cell and the upper polarizing plate, as shown in FIG. 3D. FIG. 5 (e) shows the lower polarizing plate and ST as shown in FIG. 3 (e).
One optical compensation sheet and ST between the N-type liquid crystal cell
This is the case where two optical compensation sheets are provided between the N-type liquid crystal cell and the upper polarizing plate. X is a reference direction (0 °), and the meaning of each arrow is as described with reference to FIG. The transmission axis (TAa) of the lower polarizing plate and the transmission axis (TAb) of the upper polarizing plate may be interchanged.

[Transparent Support] As the transparent support of the optical compensation sheet, it is preferable to use a polymer film having a small optical anisotropy. Transparent support means that the light transmittance is 80% or more. The small optical anisotropy specifically means that the in-plane retardation (R
e) is preferably 20 nm or less, more preferably 10 nm or less, and most preferably 5 nm or less. Further, the retardation (Rth) in the thickness direction is preferably 100 nm or less, and is preferably 5 nm or less.
It is more preferably 0 nm or less, most preferably 30 nm or less. In-plane retardation (R
e) and the retardation (Rth) in the thickness direction are respectively defined by the following equations. Re = (nx−ny) × d Rth = [{(nx + ny) / 2} −nz] × d where nx and ny are in-plane refractive indices of the transparent support, and nz is the thickness of the transparent support. Is the refractive index in the direction, and d is the thickness of the transparent support.

Examples of polymers include cellulose esters,
Includes polycarbonate, polysulfone, polyethersulfone, polyacrylate and polymethacrylate. Cellulose esters are preferred, acetyl cellulose is more preferred, and triacetyl cellulose is most preferred. The polymer film is preferably formed by a solvent casting method. The thickness of the transparent support is
It is preferably 20 to 500 μm, and 50 to 2 μm.
More preferably, it is 00 μm. In order to improve the adhesion between the transparent support and the layer provided thereon (adhesive layer, vertical alignment film or optically anisotropic layer), the transparent support is subjected to a surface treatment (eg, glow discharge treatment, corona discharge treatment, Ultraviolet (UV) treatment, flame treatment) may be performed. An adhesive layer (undercoat layer) may be provided on the transparent support.

[Alignment Film] According to the study of the present inventors, in order for the discotic liquid crystal molecules to be substantially vertically aligned, the function of the side chain is more important than the main chain of the polymer contained in the alignment film. It is. Specifically, the surface energy of the alignment film is reduced by the functional groups of the polymer, and thereby the discotic liquid crystal molecules are in a standing state. As the functional group that lowers the surface energy of the alignment film, a hydrocarbon group having 10 or more carbon atoms or a fluorine atom is effective. In order to make the hydrocarbon group or the fluorine atom exist on the surface of the alignment film, the hydrocarbon group or the fluorine atom is introduced into the side chain instead of the main chain of the polymer. The hydrocarbon group is an aliphatic group, an aromatic group, or a combination thereof. The aliphatic group may be cyclic, branched, or linear.
The aliphatic group is preferably an alkyl group (may be a cycloalkyl group) or an alkenyl group (may be a cycloalkenyl group). The hydrocarbon group may have a substituent that does not show strong hydrophilicity, such as a halogen atom. The number of carbon atoms in the hydrocarbon group is 10 to 10
It is preferably 0, more preferably 10 to 60, and most preferably 10 to 40. The polymer having a hydrocarbon group having 10 or more carbon atoms preferably has a steroid structure in a main chain or a side chain. The steroid structure present in the side chain corresponds to a hydrocarbon group having 10 or more carbon atoms, and has a function of vertically aligning discotic liquid crystalline molecules. In the present specification, a steroid structure refers to a cyclopentanohydrophenanthrene ring structure or a ring structure in which a part of the bond of the ring is a double bond in the range of an aliphatic ring (range in which an aromatic ring is not formed). means.

The fluorine-containing polymer has a fluorine atom of 0.0
Preferably, it is contained in an amount of 5 to 80% by weight,
More preferably, it is contained in an amount of 0.1 to 70% by weight.
More preferably, it is contained in a proportion of 5 to 65% by weight,
Most preferably, it is contained in a proportion of 1 to 60% by weight. The main chain of the polymer preferably has a polyimide structure. Polyimide is generally synthesized by a condensation reaction between a tetracarboxylic acid and a diamine. A polyimide corresponding to a copolymer may be synthesized using two or more kinds of tetracarboxylic acids or two or more kinds of diamines. A hydrocarbon group having 10 or more carbon atoms or a fluorine atom may be present in a repeating unit derived from a tetracarboxylic acid, in a repeating unit derived from a diamine, or in both repeating units. Is also good.

A polymerizable group may be introduced into the polymer of the alignment film. When a polymer having a polymerizable group and a discotic liquid crystal molecule having a polymerizable group are used in combination, the polymer and the discotic liquid crystal molecule are chemically bonded to each other via the interface between the optically anisotropic layer and the alignment film. Can be combined. Thereby, the durability of the optical compensation sheet can be improved. When the main chain of the polymer has a polyimide structure, the polymerizable group may be present in a repeating unit derived from a tetracarboxylic acid, may be present in a repeating unit derived from a diamine, or may be present in both repeating units. You may. The type of the polymerizable group is determined according to the type of the polymerizable group (Q) of the discotic liquid crystal molecule described below. As described below, the polymerizable group (Q) of the liquid crystal molecule includes an unsaturated polymerizable group (Q1 to Q7 described below), an epoxy group (Q
8) or an aziridinyl group (Q9), more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group (Q1 to Q6). Similarly, the polymerizable group of the polymer of the alignment film is preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group. Is most preferred.

It is preferable that the main chain of the polymer and the polymerizable group are not directly linked but are linked via a linking group. Examples of the linking group include -O-, -O-CO-, -O-CO-NH-,
-O-CO-NH-alkylene group-, -O-CO-NH
-Alkylene group -O-, -O-CO-NH-alkylene group -CO-O-, -O-CO-NH-alkylene group -O
-CO-, -O-CO-NH-alkylene group -CO-N
H-, -O-CO-alkylene group -O-CO-, -O-
CO-arylene group-O-alkylene group-O-CO-,
-O-CO-arylene group-O-alkylene group-O-,
-O-CO-arylene group-O-alkylene group- and -O-alkylene group-O-CO- are included (the left side is bonded to the main chain, and the right side is bonded to the polymerizable group). The alkylene group may have a branched or cyclic structure. The number of carbon atoms of the alkylene group is preferably 1 to 30, more preferably 1 to 20, still more preferably 1 to 15, and most preferably 1 to 12. The arylene group is preferably phenylene or naphthylene, more preferably phenylene, and most preferably p-phenylene. The arylene group may have a substituent. The polymer may have two or more polymerizable groups.

Examples of the repeating unit derived from a tetracarboxylic acid (the nitrogen atom of the imide structure is derived from a diamine) are shown below.

[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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[0033]

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Examples of repeating units derived from diamine are shown below.

[0035]

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[0036]

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[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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A group different from the repeating unit may be bonded to the terminal of the polyimide. Examples of the terminal group are shown below.

[0047]

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[0048]

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Examples of the polyimide having a hydrocarbon group on the side chain which can be preferably used for the alignment film include a repeating unit (A) derived from tetracarboxylic acid, a repeating unit (B) derived from diamine, and a terminal group (E). The numbers are quoted and shown. The proportion of repeating units in the copolymer is mol%.

The PI1: -A1-B1- PI2 :-( A1 -B1) 80 - (A1-B2) 20 - PI3 :-( A2-B1) 50 - (A1-B1) 50 - PI4: -A2-B3 _{- PI5 :-( A2-B3) 90} - (A2-B2) 10 - PI6: -A3-B1- PI7 :-( A2-B1) 40 - (A2-B4) 60 - PI8: -A2-B5- PI9 _{:-( A2-B5) 85 - (} A2-B2) 15 - PI10: -A4-B6-

[0051] _{PI11 :-( A3-B7) 50 -} (A4-B7) 50 - PI12: -A2-B8- PI13 :-( A3-B9) 75 - (A4-B9) 25 - PI14: -A3-B10 _{- PI15 :-( A5-B11) 85} - (A5-B12) 15 - PI16 :-( A2-B13) 60 - (A5-B13) 40 - PI17: -A2-B14- PI18 :-( A2-B14) _30- (A3-B14) _30- (A
_{2-B12) 20 - (A3} -B12) 20 - PI19: E1- (A2-B15) -E2 PI20: E3- (A5-B5) -E4

[0052] _{PI21 :-( A2-B1) 65 -} (A2-B2) 35 - PI22: -A6-B16- PI23: -A4-B17- PI24 :-( A4-B18) 40 - (A3-B18) 60 -PI25: -A4-B19- PI26: -A4-B20- PI27: -A7-B21- PI28: -A4-B22-

Further, examples of the fluorine-containing polyimide which can be preferably used for the alignment film are cited with reference to the numbers of the repeating unit (A) derived from tetracarboxylic acid, the repeating unit (B) derived from diamine, and the terminal group (E). While showing.
The proportion of repeating units in the copolymer is mol%.

[0054] PI31: -A8-B23- PI32: -A9 -B24- PI33: -A10-B25- PI34: -A11-B23- PI35: -A12-B23- PI36 :-( A13-B26) 90 - (A13 _{-B2) 10 - PI37 :-( A13-} B26) 80 - (A13-B2) 20 - PI38 :-( A13-B26) 65 - (A13-B2) 35 - PI39 :-( A11-B27) -E5 PI40 : -A8-B28- PI41 :-( A8- B29) 60 - (A8-B26) 40 - PI42 :-( A8-B29) 50 - (A8-B26) 50 - PI43 :-( A8-B29) 25 - (A8-B26) ₇₅ -

[0055] _{PI44 :-( A9-B30) 95 -} (A3-B30) 5 - PI45 :-( A9-B30) 64 - (A3-B30) 36 - PI46 :-( A9-B30) 45 - (A3- _{B30) 55 - PI47: -A9-} B31- PI48 :-( A14-B32) 70 - (A2-B32) 30 - PI49 :-( A14-B32) 55 - (A2-B32) 45 - pI50 :-( A14 _{-B32) 20 - (A2-B32} ) 80 - PI51 :-( A15-B33) 78 - (A15-B34) 22 - PI52 :-( A15-B33) 63 - (A15-B34) 37 - PI53 :-( _{A15-B33) 22 - (A15} -B34) 78 - PI54 :-( A16-B35) 67 - (A2-B36) 33 - PI55 :-( A16-B35) 50 - (A2-B36) 50 - PI56: - _{(A16-B35) 22 - (} A2-B36) 78 -

[0056] _{PI57 :-( A16-B37) 85 -} (A16-B2) 15 - PI58 :-( A16-B37) 98 - (A16-B2) 2 - PI59 :-( A16-B37) 64 - (A16- _{B2) 36 - PI60 :-( A16-} B38) 99 - (A4-B38) 1 - PI61 :-( A16-B38) 81 - (A4-B38) 19 - PI62 :-( A16-B38) 51 - (A4 _{-B38) 49 - PI63 :-( A9-} B39) 30 - (A2-B39) 70 - PI64 :-( A9-B39) 55 - (A2-B39) 45 - PI65 :-( A9-B39) 1 - ( A2-B39) ₉₉ -PI66:-(A16-B40) -E6 PI67: -A2-B41- PI68: -A3-B42- PI69: -A4-B42-

[0057] PI70: -A2-B44- PI71 :-( A2 -B45) 70 - (A2-B2) 30 - PI72 :-( A2-B45) 56 - (A2-B2) 44 - PI73 :-( A2- _{B45) 44 - (A2-B2} ) 56 - PI74 :-( A6-B46) 60 - (A17-B46) 40 - PI75 :-( A6-B46) 50 - (A17-B46) 50 - PI76 :-( A6 _{-B46) 40 - (A17-B46} ) 60 - PI77 :-( A4-B47) 90 - (A4-B22) 10 - PI78 :-( A4-B47) 99 - (A4-B22) 1 - PI79 :-( _{A4-B47) 75 - (A4} -B22) 25 - PI80 :-( A4-B48) -E7 PI81 :-( A8-B23) -E8

A polyamic acid containing a hydrocarbon group having 10 or more carbon atoms or a fluorine atom can also be used for the alignment film. The polyamic acid is synthesized by a partial condensation reaction between a tetracarboxylic acid and a diamine. That is, two out of the four carboxyls of the tetracarboxylic acid are reacted with the diamine to form an amide bond. The remaining two carboxyls of the tetracarboxylic acid remain in the polyamic acid. Even polyamic acid can function as an alignment film. Further, the polyamic acid can be heated to be dehydrated and ring-closed to form a polyimide, which can then be used as an alignment film. By heating the polyamic acid for a short time or at a low temperature to partially dehydrate and close the ring, the resulting copolymer of the polyamic acid and polyimide may be used as an alignment film.

The degree of polymerization of the polymer used for the alignment film is 20
0 to 5000, preferably 300 to 30
00 is preferred. The molecular weight of the polymer is 90
00 to 200,000, preferably 1300
More preferably, it is 0 to 130,000. Two or more polymers may be used in combination.

The polymer used for the alignment film may be crosslinked. The cross-linking reaction is preferably performed simultaneously with or after the application of the coating liquid for the alignment film. Crosslinking of the polymer can be formed using a crosslinking agent. Examples of the crosslinking agent include epoxy compounds (eg, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, polyethylene glycol diglycidyl ether), aldehydes (eg, formaldehyde, glyoxal, glutaraldehyde, malonaldehyde, phthalaldehyde, terephthalaldehyde, Succinaldehyde, isophthalaldehyde, dialdehyde starch), N-methylol compounds (eg,
Dimethylol urea, methylol dimethylhydantoin), dioxane (eg, 2,3-dihydroxydioxane), carbenium, 2-naphthalate sulfonate,
1,1-bispyrrolidino-1-chloropyridinium, 1
-Morpholinocarbonyl-3- (sulfonatoaminomethyl), an active vinyl compound (eg, 1,3,5-triacryloyl-hexahydro-s-triazine, bis (vinylsulfone) methane, N, N′-methylenebis- [β −
(Vinylisulfonyl) propionamide), an active halogen compound (eg, 2,4-dichloro-6-hydroxy-s-)
Triazines) and isoxazoles. When the polymer is polyimide or polyamic acid, it is preferable to use an epoxy compound as a crosslinking agent.

The thickness of the alignment film is preferably 0.1 to 10 μm. In forming the alignment film, a rubbing treatment is preferably performed. The rubbing treatment is performed by rubbing the surface of the film containing the polymer several times with paper or cloth in a certain direction. After the discotic liquid crystal molecules are substantially vertically aligned using an alignment film, the discotic liquid crystal molecules are fixed in the aligned state to form an optically anisotropic layer. Only the isotropic layer may be transferred onto the transparent support. Discotic liquid crystalline molecules with a fixed alignment state can maintain the alignment state without an alignment film.

[Optical Anisotropic Layer] The optically anisotropic layer contains discotic liquid crystal molecules. In the optically anisotropic layer,
Using the above-mentioned alignment film, the disc surface of the discotic liquid crystalline molecules is substantially perpendicular to the alignment film (50 to 9).
(An average inclination angle in a range of 0 degree). It is preferable that the discotic liquid crystal molecules are fixed in the optically anisotropic layer while maintaining a vertical (homogeneous) alignment state. More preferably, the discotic liquid crystalline molecules are fixed by a polymerization reaction. Discotic liquid crystal molecules are described in various literatures (C. Destrade et al., Mol. Crysr. Liq. Cry
st., vol. 71, page 111 (1981); edited by The Chemical Society of Japan, quarterly chemistry review, No. 22, Chemistry of Liquid Crystal, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. C
hem. Comm., page 1794 (1985); J. Zhang et al., J.
Am. Chem. Soc., Vol. 116, page 2655 (1994)). The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284. In order to fix discotic liquid crystalline molecules by polymerization,
It is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecule. However, when a polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain an oriented state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystalline molecule having a polymerizable group is preferably a compound represented by the following formula.

D (-LQ) _{n wherein} D is a discotic core; L is a divalent linking group; Q is a polymerizable group; and n is an integer from 4 to 12 is there. An example of the discotic core (D) of the above formula is shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).

[0064]

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[0065]

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[0066]

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[0067]

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[0068]

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[0069]

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[0070]

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In the above formula, the divalent linking group (L) is
Alkylene group, alkenylene group, arylene group, -CO
It is preferably a divalent linking group selected from the group consisting of-, -NH-, -O-, -S- and a combination thereof. The divalent linking group (L) is an alkylene group, an alkenylene group, an arylene group, -CO-, -NH-, -O-
And a group obtained by combining at least two divalent groups selected from the group consisting of and -S-.
The divalent linking group (L) is most preferably 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, -CO- and -O-. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The arylene group preferably has 6 to 10 carbon atoms. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group, a halogen atom, a cyano, an alkoxy group, an 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-CO-O-AL- L2: -AL-CO-O-AL-O- L3: -AL-CO-O-AL-O-AL- L4: -AL-CO-O -AL-O-CO-L5: -CO-AR-O-AL-L6: -CO-AR-O-AL-O-L7: -CO-AR-O-AL-O-CO-L8: -CO -NH-AL-L9: -NH-AL-O-L10: -NH-AL-O-CO-L11: -O-AL-L12: -O-AL-O-L13: -O-AL-O- CO-

L14: -O-AL-O-CO-NH-AL- L15: -O-AL-S-AL- L16: -O-CO-AL-AR-O-AL-O-CO-L17: -O-CO-AR-O-AL-CO-L18: -O-CO-AR-O-AL-O-CO-L19: -O-CO-AR-O-AL-O-AL-OC
O-L20: -O-CO-AR-O-AL-O-AL-OA
L-O-CO-L21: -S-AL-L22: -S-AL-O-L23: -S-AL-O-CO-L24: -S-AL-S-AL-L25: -S-AR -AL-

When an asymmetric carbon atom is introduced into AL (alkylene group or alkenylene group), the discotic liquid crystalline molecule can be twisted and aligned in a helical manner.
Examples of AL * containing an asymmetric carbon atom are given below. The left side is the disc-shaped core (D) side, and the right side is the polymerizable group (Q) side. The carbon atom (C) marked with * is an asymmetric carbon atom. The optical activity may be either S or R.

AL * 1: -CH ₂ CH ₂ -C * HCH _{3
-CH 2 CH 2 CH 2 - AL} * 2: -CH 2 CH 2 CH 2 -C * HCH 3 -CH
_{2 CH 2 - AL * 3:} -CH 2 -C * HCH 3 -CH 2 CH 2 CH
_{2 CH 2 - AL * 4:} -C * HCH 3 -CH 2 CH 2 CH 2 CH 2
_{CH 2 - AL * 5: -CH} 2 CH 2 CH 2 CH 2 -C * HCH 3
_{-CH 2 - AL * 6: -CH} 2 CH 2 CH 2 CH 2 CH 2 -C * H
_{CH 3 - AL * 7: -C} * HCH 3 -CH 2 CH 2 CH 2 CH 2
_{- AL * 8: -CH 2 -C} * HCH 3 -CH 2 CH 2 CH
_{2 - AL * 9: -CH 2} CH 2 -C * HCH 3 -CH 2 CH
_{2 - AL * 10: -CH 2} CH 2 CH 2 -C * HCH 3 -CH
_{2 - AL * 11: -CH 2} CH 2 CH 2 CH 2 -C * HCH 3
- AL * 12: -C * HCH 3 -CH 2 CH 2 CH 2 - AL * 13: -CH 2 -C * HCH 3 -CH 2 CH 2 - AL * 14: -CH 2 CH 2 -C * HCH 3 _{-CH 2 - AL * 15: -CH} 2 CH 2 CH 2 -C * HCH 3 -

[0076] _{AL * 16: -CH 2 -C *} HCH 3 - AL * 17: -C * HCH 3 -CH 2 - AL * 18: -C * HCH 3 -CH 2 CH 2 CH 2 CH 2
_{CH 2 CH 2 - AL * 19} : -CH 2 -C * HCH 3 -CH 2 CH 2 CH
_{2 CH 2 CH 2 - AL *} 20: -CH 2 CH 2 -C * HCH 3 -CH 2 CH
_{2 CH 2 CH 2 - AL *} 21: -CH 2 CH 2 CH 2 -C * HCH 3 -CH
_{2 CH 2 CH 2 - AL *} 22: -C * HCH 3 -CH 2 CH 2 CH 2 CH 2
_{CH 2 CH 2 CH 2 - AL} * 23: -CH 2 -C * HCH 3 -CH 2 CH 2 CH
₂ CH ₂ CH ₂ CH ₂ -AL * 24: -CH ₂ CH ₂ -C * HCH ₃ -CH ₂ CH
_{2 CH 2 CH 2 CH 2 -} AL * 25: -CH 2 CH 2 CH 2 -C * HCH 3 -CH
_{2 CH 2 CH 2 CH 2 -} AL * 26: -C * HCH 3 - (CH 2) 8 - AL * 27: -CH 2 -C * HCH 3 - (CH 2) 8 - AL * 28: -CH 2 _{-C * HCH 2 CH 3 - AL} * 29: -CH 2 -C * HCH 2 CH 3 -CH 2 - AL * 30: -CH 2 -C * HCH 2 CH 3 -CH 2 CH
₂ −

[0077] _{AL * 31: -CH 2 -C *} HCH 2 CH 3
_{-CH 2 CH 2 CH 2 CH 2} - AL * 32: -CH 2 -C * H (n-C 3 H 7) -CH 2
_{CH 2 - AL * 33: -CH} 2 -C * H (n-C 3 H 7) -CH 2
_{CH 2 CH 2 CH 2 - AL} * 34: -CH 2 -C * H (OCOCH 3) -CH 2
_{CH 2 - AL * 35: -CH} 2 -C * H (OCOCH 3) -CH 2
_{CH 2 CH 2 CH 2 - AL} * 36: -CH 2 -C * HF-CH 2 CH 2 - AL * 37: -CH 2 -C * HF-CH 2 CH 2 CH 2 C
_{H 2 - AL * 38: -CH} 2 -C * HCl-CH 2 CH 2 - AL * 39: -CH 2 -C * HCl-CH 2 CH 2 CH 2
_{CH 2 - AL * 40: -CH} 2 -C * HOCH 3 -CH 2 CH 2 - AL * 41: -CH 2 -C * HOCH 3 -CH 2 CH 2 C
_{H 2 CH 2 - AL * 42} : -CH 2 -C * HCN-CH 2 CH 2 - AL * 43: -CH 2 -C * HCN-CH 2 CH 2 CH 2
_{CH 2 - AL * 44: -CH} 2 -C * HCF 3 -CH 2 CH 2 - AL * 45: -CH 2 -C * HCF 3 -CH 2 CH 2 CH
₂ CH ₂ −

The polymerizable group (Q) in the above formula is determined according to the type of the polymerization reaction. Examples of the polymerizable group (Q) are shown below.

[0079]

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The polymerizable group (Q) is an unsaturated polymerizable group (Q1
To Q7), an epoxy group (Q8) or an aziridinyl group (Q9), more preferably an unsaturated polymerizable group, and more preferably an ethylenically unsaturated polymerizable group (Q
1 to Q6) are most preferred. In the above formula, n is an integer of 4 to 12. Specific numbers are determined according to the type of discotic core (D).
The combination of a plurality of L and Q may be different, but is preferably the same. Two or more discotic liquid crystal molecules may be used in combination. For example, a molecule having an asymmetric carbon atom in the divalent linking group and a molecule having no asymmetric carbon atom can be used in combination. Further, a molecule having a polymerizable group (Q) and a molecule having no polymerizable group (Q) may be used in combination. It is particularly preferable to use a molecule having an asymmetric carbon atom and having no polymerizable group in combination with a molecule having a polymerizable group and having no asymmetric carbon atom. In this case, only molecules having a polymerizable group and having no asymmetric carbon atom function as discotic liquid crystal molecules, and molecules having an asymmetric carbon atom and having no polymerizable group are chiral agents. (Described later).

The non-polymerizable discotic liquid crystalline molecules are
It is preferable that the compound is obtained by changing the polymerizable group (Q) of the polymerizable discotic liquid crystal molecule to a hydrogen atom or an alkyl group. That is, the non-polymerizable discotic liquid crystal molecule is preferably a compound represented by the following formula. D (-LR) _{n wherein} 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 from 4 to 12 . The example of the discotic core (D) in the above formula is the same as the example of the polymerizable discotic liquid crystal molecules described above, except that LQ (or QL) is changed to LR (or RL). The example of the divalent linking group (L) is the same as the example of the polymerizable discotic liquid crystal molecule. The alkyl group for R preferably has 1 to 40 carbon atoms, and preferably has 1 to 40 carbon atoms.
More preferably, it is from 30 to 30. A chain alkyl group is more preferable than a cyclic alkyl group, and a straight-chain alkyl group is more preferable than a branched chain alkyl group.
R is particularly preferably a hydrogen atom or a linear alkyl group having 1 to 30 carbon atoms.

Instead of introducing an asymmetric carbon atom into the divalent linking group (L) of the discotic liquid crystal molecule, a compound having an asymmetric carbon atom and exhibiting optical activity (chiral agent) is used as an optically anisotropic layer. , The discotic liquid crystalline molecules can be helically twisted and aligned. As the compound containing an asymmetric carbon atom, various natural or synthetic compounds can be used. The same or similar polymerizable group as the discotic liquid crystalline molecule may be introduced into the compound containing an asymmetric carbon atom. When a polymerizable group is introduced, the discotic liquid crystal molecules are aligned substantially vertically (homogeneously) and then fixed, and at the same time, the compound containing an asymmetric carbon atom is also optically anisotropic by the same or similar polymerization reaction. Can be fixed in the functional layer.

A fluorine-containing surfactant or a cellulose ester can be added to the optically anisotropic layer in order to align the discotic liquid crystalline molecules substantially vertically (homogeneously) and uniformly on the air interface side. . The fluorinated surfactant is composed of a hydrophobic group containing a fluorine atom, a nonionic, anionic, cationic or amphoteric hydrophilic group and an optionally provided linking group. Fluorine-containing surfactant consisting of one hydrophobic group and one hydrophilic group,
It is represented by the following equation. Rf-L ⁵ -Hy In the formula, Rf is a monovalent hydrocarbon group substituted with a fluorine atom, L ⁵ is a single bond or a divalent linking group,
Hy is a hydrophilic group. The above Rf functions as a hydrophobic group. The hydrocarbon group is preferably an alkyl group or an aryl group. The alkyl group preferably has 3 to 30 carbon atoms, and the aryl group preferably has 6 to 30 carbon atoms. Some or all of the hydrogen atoms contained in the hydrocarbon group are substituted with fluorine atoms. It is preferable to replace 50% or more of the hydrogen atoms contained in the hydrocarbon group with a fluorine atom.
More preferably, 0% or more is substituted, more preferably 70% or more is substituted, and most preferably 80% or more is substituted. The remaining hydrogen atoms may be further substituted with another halogen atom (eg, chlorine atom, bromine atom). Examples of Rf are shown below.

[0084] _{Rf1: n-C 8 F 17} - Rf2: n-C 6 F 13 - Rf3: Cl- (CF 2 -CFCl) 3 -CF 2 - Rf4: H- (CF 2) 8 - Rf5: H- _{(CF 2) 10 - Rf6:} n-C 9 F 19 - Rf7: pentafluorophenyl _{Rf8: n-C 7 F 15} - Rf9: Cl- (CF 2 -CFCl) 2 -CF 2 - Rf10: H- (CF _{2) 4 - Rf11: H- (} CF 2) 6 - Rf12: Cl- (CF 2) 6 - Rf13: C 3 F 7 -

In the above formula, the divalent linking group is an alkylene group, an arylene group, a divalent heterocyclic residue, -CO
—, —NR— (R is an alkyl group having 1 to 5 carbon atoms or a hydrogen atom), —O—, —SO ₂ — and a divalent linking group selected from the combination thereof. preferable. Examples of L ⁵ in the formula shown below. The left side is bonded to a hydrophobic group (Rf), and the right side is a hydrophilic group (Hy).
To join. AL represents an alkylene group, AR represents an arylene group, and Hc represents a divalent heterocyclic residue. Incidentally, an alkylene group, an arylene group and a divalent heterocyclic residue are
It may have a substituent (eg, an alkyl group).

[0086] L0: single bond _{L51: -SO 2 -NR- L52: -AL} -O- L53: -CO-NR- L54: -AR-O- L55: -SO 2 -NR-AL-CO-O- L56: -CO-O- L57: -SO 2 -NR-AL-O- L58: -SO 2 -NR-AL- L59: -CO-NR-AL- L60: -AL-O-AL- L61: - _{hc-AL- L62: -SO 2 -NR} -AL-O-AL- L63: -AR- L64: -O-AR-SO 2 -NR-AL- L65: -O-AR-SO 2 -NR- L66 : -O-AR-O-

Hy in the above formula is any one of a nonionic hydrophilic group, an anionic hydrophilic group, a cationic hydrophilic group and an amphoteric hydrophilic group. Nonionic hydrophilic groups are particularly preferred. An example of Hy in the above formula is shown below.

Hy1:-(CH ₂ CH ₂ O) _n -H (n
Is an integer of 5 to _{30) Hy2 :-( CH 2 CH 2} O) n -R 1 (n is 5 to 3
0 integer, R ¹ is an alkyl group having 1 to 6 carbon _{atoms) Hy3 :-( CH 2 CHOHCH 2)} n -H (n is 5 to 30 integer) Hy4: -COOM (M represents a hydrogen atom, an alkali metal atom or dissociated state) Hy5: -SO ₃ M (M is a hydrogen atom, an alkali metal atom or dissociated _{state) Hy6 :-( CH 2 CH 2 O} ) n -CH 2 CH 2 CH 2
-SO ₃ M (n is 5 to 30 integer, M is a hydrogen atom or an alkali metal _{atom) Hy7: -OPO (OH) 2} Hy8: -N + (CH 3) 3 · X - (X represents a halogen atom) Hy9 : -COONH ₄

Nonionic hydrophilic groups (Hy1, Hy2, H
y3) is preferable, and a hydrophilic group (Hy1) composed of polyethylene oxide is most preferable. A fluorine-containing surfactant having two or more hydrophobic or hydrophilic groups containing a fluorine atom may be used. Two or more fluorine-containing surfactants may be used in combination. For fluorinated surfactants, see various references (eg, Hiroshi Horiguchi, “New Surfactants”, Sankyo Publishing (197
5), MJ Schick, Nonionic Surfactants, Marcell Dek
ker Inc., New York, (1967), JP-A-7-13293). The amount of the fluorinated surfactant is preferably in the range of 0.01 to 30% by weight, more preferably 0.05 to 10% by weight, and more preferably 0.1 to 5% by weight of the amount of the discotic liquid crystal molecules. % Is more preferable.

As the cellulose ester, a lower fatty acid ester of cellulose is preferably used. The “lower fatty acid” in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 to 5, more preferably 2 to 4. A substituent (eg, hydroxy) may be bonded to the fatty acid. Two or more fatty acids may form an ester with cellulose. Examples of lower fatty acid esters of cellulose include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose hydroxypropionate, cellulose acetate propionate, and cellulose acetate butyrate. Cellulose acetate butyrate is particularly preferred. The butyrylation degree of cellulose acetate butyrate is preferably 30% or more, and preferably 3% or more.
More preferably, it is 0 to 80%. The acetylation degree of cellulose acetate butyrate is preferably 30% or less, more preferably 1 to 30%. Cellulose ester is used in an amount of 0.005 to 0.5.
Preferably, it is used in an amount in the range of 5 g / m ² ,
The range is more preferably from 0.01 to 0.45 g / m ² , still more preferably from 0.02 to 0.4 / m ² , and more preferably from 0.03 to 0.35 / m ^2. Is most preferred. It is also preferable to use 0.1 to 5% by weight of the discotic liquid crystal molecules.

The optically anisotropic layer is composed of discotic liquid crystal molecules, and further, if necessary, a compound containing an asymmetric carbon atom, a fluorine-containing surfactant, a cellulose ester, or the following polymerization initiators and other additives. Is formed by applying a coating solution containing As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of the organic solvent include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethylsulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, ,
Chloroform, dichloromethane), ester (eg, methyl acetate, butyl acetate), ketone (eg, acetone, methyl ethyl ketone), ether (eg, tetrahydrofuran,
1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

The coating solution can be applied by a known method (eg, extrusion coating, direct gravure coating, reverse gravure coating, die coating, bar coating). Discotic liquid crystalline molecules that are substantially vertically (homogeneously) aligned are fixed while maintaining the alignment state. Immobilization is
Polymerizable group (Q) introduced into discotic liquid crystal molecules
It is preferable to carry out the polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Photopolymerization reactions are preferred. Examples of photopolymerization initiators include α-carbonyl compounds (described in U.S. Pat. Nos. 2,367,661 and 2,367,670) and acyloin ethers (U.S. Pat.
No. 8), α-hydrocarbon substituted aromatic acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (US Pat. Nos. 3,046,127 and 2951).
No. 758), a combination of a triarylimidazole dimer and p-aminophenyl ketone (described in US Pat. No. 3,549,367), an acridine and phenazine compound (JP-A-60-105667, US Pat. No. 4,239,850). Oxadiazole compounds (described in US Pat. No. 4,221,970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by weight of the solid content of the coating solution.
More preferably, it is 5 to 5% by weight. Light irradiation for the polymerization of discotic liquid crystalline molecules preferably uses ultraviolet light. The irradiation energy is 20 mJ /
cm ^{2 to} 50 J / cm ² , preferably 10
More preferably, it is 0 to 2000 mJ / cm ² . Light irradiation may be performed under heating conditions to promote the photopolymerization reaction. The thickness of the optically anisotropic layer is preferably 0.1 to 50 μm, more preferably 1 to 30 μm, and most preferably 5 to 20 μm. When two optical compensatory sheets are used in the liquid crystal display device, the thickness may be half the thickness of the optically anisotropic layer (the above-mentioned preferred range) required when using one optical compensatory sheet. The average tilt angle of the discotic liquid crystalline molecules in the optically anisotropic layer is 50 to 90 degrees. The angle of inclination is preferably as uniform as possible. However, if the tilt angle changes continuously along the thickness direction of the optically anisotropic layer, there is no problem even if there is a slight change.

The twist angle (twist angle) of the discotic liquid crystal molecules is similar (as much as possible) depending on the twist angle of the STN type liquid crystal cell (generally 180 to 360 °, preferably more than 180 ° to 270 °). It is preferable to adjust the angle so as to be within ± 10 °. When one optical compensation sheet is used for a liquid crystal display device, the twist angle of the discotic liquid crystal molecules is 180 to 36.
It is preferable that the angle is in the range of 0 degrees. When two optical compensation sheets are used in a liquid crystal display device, the twist angle of the discotic liquid crystal molecules is preferably in the range of 90 to 180 degrees. When the optical compensation sheet is used in an STN-type liquid crystal display device, the wavelength dependence (Δn (λ)) of the birefringence of the optically anisotropic layer depends on the wavelength dependence of the birefringence of the liquid crystal of the STN-type liquid crystal cell. Preferably, the values are close.

[Liquid Crystal Display Device] As described above, the present invention is particularly effective in a liquid crystal display device using an STN type liquid crystal cell. The STN type liquid crystal display device includes an STN type liquid crystal cell, one or two optical compensatory sheets disposed on one or both sides of the liquid crystal cell, and a pair of polarizing plates disposed on both sides thereof. The relationship between the alignment direction of the rod-like liquid crystal molecules in the liquid crystal cell and the alignment direction of the discotic liquid crystal molecules is determined by the director of the liquid crystal cell closest to the optical compensation sheet (the long axis direction of the rod-like molecules) and the liquid crystal. The director of the discotic liquid crystalline molecules of the optical compensation sheet closest to the cell (the normal direction of the disk-shaped core plane)
Seen from the normal direction of the liquid crystal cell, substantially the same direction (± 1
(Less than 0 °). The transparent support of the optical compensation sheet can also function as a protective film on the liquid crystal cell side of the polarizing film. In such a case, the transparent support is arranged so that the slow axis (the direction in which the refractive index is maximized) and the transmission axis of the polarizing film are substantially perpendicular or substantially parallel (less than ± 10 °). Is preferred.

[0096]

[Example 1] Thickness 100 μm, size 270
A 100 mm × 100 mm triacetylcellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) was used as a transparent support. Polyimide (PI1) having a hydrocarbon group in a side chain was dissolved in a mixed solvent of methanol and acetone (volume ratio = 50/50) to prepare a 5% by weight solution. This solution was applied to a thickness of 1 μm on a transparent support using a bar coater. The coating layer was dried with warm air at 130 ° C. for 2 minutes, and its surface was rubbed to form an alignment film. On the alignment film, a coating solution having the following composition was applied by an extrusion method.

<< Coating Solution for Optically Anisotropic Layer >> ───────────────────────────────── The following discotic liquid crystalline compound (1) 80 parts by weight The following discotic Liquid crystal compound (2) 20 parts by weight The following fluorinated surfactant 0.1 part by weight Photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) 0.2 part by weight Methyl ethyl ketone 185 parts by weight ───────────────────────────────

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[0100]

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The coating layer was heated at 130 ° C. for 2 minutes to orient the discotic liquid crystal compound substantially vertically. At that temperature, ultraviolet rays were irradiated for 4 seconds to polymerize the discotic liquid crystalline compound and fix the alignment state. In this way, an optically anisotropic layer in which the discotic liquid crystalline compound was vertically and twisted was formed to form an optical compensation sheet. 4 with respect to the rubbing axis of the alignment film
At an angle of 5 °, polarized light is incident on the optical compensation sheet from the transparent support side, and the optical equipment (Multi Chanel Photo Analyzer,
Polarization analysis of the emitted light using Otsuka Electronics Co., Ltd.)
When the twist angle was determined, it was 230-250 °.

Separately, except that the discotic liquid crystal compound (2) was removed from the coating liquid for the optically anisotropic layer, the discotic liquid crystal compound was substantially vertically oriented, but twisted. No optical compensatory sheet made. For this sheet, using an ellipsometer,
The in-plane retardation (Re) was measured, and the average inclination angle was determined from the angle dependence to be 70 to 85 °. Separately, an anti-parallel cell was prepared using a horizontal alignment film, and the discotic liquid crystalline compounds (1) and (2) were sealed in the cell. The in-plane retardation (Re) of the obtained liquid crystal cell was measured using an ellipsometer, and the value was divided by the cell thickness to obtain Δn, which was 0.07.

Example 2 An optical compensatory sheet was prepared and evaluated in the same manner as in Example 1 except that the same amount of polyimide (PI2) was used instead of polyimide (PI1). The average tilt angle of the discotic liquid crystalline compound was 70 °.

Example 3 An optical compensatory sheet was prepared and evaluated in the same manner as in Example 1 except that the same amount of polyimide (PI3) was used instead of polyimide (PI1). The average tilt angle of the discotic liquid crystalline compound was 60 °.

Example 4 An optical compensatory sheet was prepared and evaluated in the same manner as in Example 1, except that the same amount of polyimide (PI4) was used instead of polyimide (PI1). The average tilt angle of the discotic liquid crystalline compound was 75 °.

[Comparative Example 1] Inorganic vertical alignment film forming material (E
XP-OA004 (manufactured by Nissan Chemical Industries, Ltd.) was diluted with methanol to a solid content of 2% by weight. This was applied on a glass plate with a bar coater so as to have a thickness of 0.4 μm.
After drying at 40 ° for 10 minutes, an alignment film was formed. After rubbing the alignment film, two antiparacels were formed. In one cell, a rod-like liquid crystal molecule (MBBA) was inserted. Into the other cell, a product obtained by evaporating methyl ethyl ketone from the coating liquid for the optically anisotropic layer used in Example 1 and solidifying it (a discotic liquid crystal molecule) was inserted. For each cell, the alignment state of liquid crystalline molecules was examined. In the cell into which the rod-like liquid crystal molecules were inserted, the rod-like liquid crystal molecules were nematically aligned in a direction perpendicular to the glass plate. On the other hand, in the cell in which the discotic liquid crystal molecules were inserted, the average tilt angle was 30 ° and the vertical alignment (50 to 90)
゜) did not become. The used material for forming an inorganic vertical alignment film is commercially available as a vertical alignment film for rod-like liquid crystalline molecules, and is most commonly used. Experimental results using other commercially available vertical alignment films for rod-like liquid crystal molecules show that the vertical alignment films for commercially available rod-like liquid crystal molecules have insufficient functions to vertically align discotic liquid crystal molecules. did.

Example 5 Using the optical compensation sheet prepared in Example 1, an STN type liquid crystal display device having a structure shown in FIG. On the surface where the liquid crystal cell and the optical compensation sheet were in contact, the alignment direction of the rod-like liquid crystal molecules of the liquid crystal cell was aligned with the alignment direction of the discotic liquid crystal molecules of the optical compensation sheet. The angle between the absorption axis of the exit-side polarizing plate and the orientation direction of the rod-like liquid crystal molecules on the exit side of the liquid crystal cell was adjusted to 45 °. The absorption axis of the incident side polarizing plate and the absorption axis of the emission side polarizing plate were arranged so as to be orthogonal to each other. When a voltage was applied to the obtained STN liquid crystal display device, a normally black mode was set. When the visual characteristics were measured, an angle range having a contrast ratio of 5 or more was obtained at 120 ° or more in the left and right directions and 150 ° or more in the vertical direction.

Example 6 An optical compensatory sheet was prepared and evaluated in the same manner as in Example 1, except that the coating liquid for the optically anisotropic layer having the following composition was used. The result was obtained.

<< Coating Liquid for Optically Anisotropic Layer >> ───────────────────────────────── 63 parts by weight of the following discotic liquid crystalline compound (3): 27 parts by weight of discotic liquid crystal compound used (2) 10 parts by weight of the following polymerizable plasticizer: 1 part by weight of photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) 185 parts by weight of methyl ethyl ketone ──────────────────────────────

[0110]

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[0111]

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Example 7 Thickness 100 μm, size 27
A 0 mm × 100 mm triacetyl cellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) was used as a transparent support. Mixed solvent of fluorinated polyimide (PI31) with methanol and acetone (volume ratio = 50/50)
To prepare a 5% by weight solution. This solution was applied to a thickness of 1 μm on a transparent support using a bar coater. The coating layer was dried with hot air at 120 ° C. for 2 minutes, and its surface was rubbed to form an alignment film. On the alignment film, an optically anisotropic layer was formed in the same manner as in Example 1,
An optical compensation sheet was prepared. Polarized light enters the optical compensatory sheet from the transparent support side at an angle of 45 ° with respect to the rubbing axis of the alignment film.
r, manufactured by Otsuka Electronics Co., Ltd.), the polarization of the emitted light was analyzed, and the twist angle was found to be 230 to 250 °.

Separately, except that the discotic liquid crystal compound (2) was removed from the coating liquid for the optically anisotropic layer, the discotic liquid crystal compound was substantially vertically oriented, but twisted. No optical compensatory sheet made. For this sheet, using an ellipsometer,
The in-plane retardation (Re) was measured, and the average inclination angle was determined from the angle dependence to be 70 to 85 °. Separately, an anti-parallel cell was prepared using a horizontal alignment film, and the discotic liquid crystalline compounds (1) and (2) were sealed in the cell. The in-plane retardation (Re) of the obtained liquid crystal cell was measured using an ellipsometer, and the value was divided by the cell thickness to obtain Δn, which was 0.07.

Example 8 An optical compensatory sheet was prepared and evaluated in the same manner as in Example 7, except that the same amount of polyimide (PI36) was used instead of polyimide (PI31). The average tilt angle of the discotic liquid crystalline compound was 70 °.

Example 9 An optical compensatory sheet was prepared and evaluated in the same manner as in Example 7, except that the same amount of polyimide (PI50) was used instead of polyimide (PI31). The average tilt angle of the discotic liquid crystalline compound was 80 °.

Example 10 An optical compensatory sheet was prepared and evaluated in the same manner as in Example 7, except that the same amount of polyimide (PI72) was used instead of polyimide (PI31). The average tilt angle of the discotic liquid crystalline compound was 75 °.

Example 11 Using the optical compensation sheet prepared in Example 7, an STN liquid crystal display having the structure shown in FIG. 3E was prepared. On the surface where the liquid crystal cell and the optical compensation sheet were in contact, the alignment direction of the rod-like liquid crystal molecules of the liquid crystal cell was aligned with the alignment direction of the discotic liquid crystal molecules of the optical compensation sheet. The angle between the absorption axis of the exit-side polarizing plate and the orientation direction of the rod-like liquid crystal molecules on the exit side of the liquid crystal cell was adjusted to 45 °. The absorption axis of the incident side polarizing plate and the absorption axis of the emission side polarizing plate were arranged so as to be orthogonal to each other. When a voltage was applied to the obtained STN liquid crystal display device, a normally black mode was set. When the visual characteristics were measured, an angle range having a contrast ratio of 5 or more was obtained at 120 ° or more in the left and right directions and 150 ° or more in the vertical direction.

Example 12 An optical compensatory sheet was prepared and evaluated in the same manner as in Example 7, except that the coating liquid for the optically anisotropic layer having the following composition was used. The result was obtained.

<< Coating Liquid for Optically Anisotropic Layer >>デ ィ ス 63 parts by weight of discotic liquid crystal compound (3) used in Example 6 27 parts by weight of the discotic liquid crystal compound (2) used in Example 1 10 parts by weight of the polymerizable plasticizer used in Example 6 1 part by weight of a photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) Cellulose acetate Butyrate (CAB551-0.2, manufactured by Eastman Chemical Company) 0.5 part by weight Methyl ethyl ketone 184.5 parts by weight ─────────────────────── ─────────────

[Brief description of the drawings]

FIG. 1 shows no voltage application (off) of an STN type liquid crystal display device.
FIG. 4 is a cross-sectional view schematically showing an alignment state of rod-like liquid crystal molecules in a liquid crystal cell and an alignment state of discotic liquid crystal molecules in an optically anisotropic layer in a pixel portion of FIG.

FIG. 2 is a schematic diagram showing respective refractive index ellipsoids of rod-like liquid crystal molecules of a liquid crystal cell and discotic liquid crystal molecules of an optical compensation sheet which has a relation of optically compensating the rod-like liquid crystal molecules.

FIG. 3 is a schematic view illustrating a layer configuration of an STN liquid crystal display device.

FIG. 4 is a plan view showing preferred optical directions for each element of the STN liquid crystal display device.

FIG. 5 is a plan view showing another preferred optical direction for each element of the STN type liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Liquid crystal cell 2, 2a, 2b Optical compensation sheet 3, 3a, 3b Polarizer 11 Upper substrate of a liquid crystal cell 12, 14 Alignment film of a liquid crystal cell 13 Refractive index ellipsoid of a rod-like liquid crystal molecule 13a-13e Rod-like liquid crystal molecule 13t Thickness of rod-like liquid crystalline molecule layer 13x, 13y Refractive index of rod-like liquid crystalline molecule in plane parallel to alignment film 13z Refractive index of rod-like liquid crystalline molecule in thickness direction 15 Lower substrate of liquid crystal cell 21 Refraction of discotic liquid crystalline molecule Index ellipsoids 21a to 21e Discotic liquid crystal molecules 21t Thickness of discotic liquid crystal molecule layer 21x, 21y Refractive index in a plane parallel to the alignment film of discotic liquid crystal molecules 21z Refraction in the thickness direction of discotic liquid crystal molecules Ratio 22 Alignment film 23 Transparent support BL Backlight DDa, DDb, DDc, DDd Discotic liquid crystal Normal direction RDa of the disc face of the child, the direction the rubbing direction TAa, the transmission axis X criteria TAb polarizing plate alignment film RDb liquid crystal cell

Claims (12)

[Claims] 1. An optical compensatory sheet comprising a transparent support and an alignment film and an optically anisotropic layer formed of discotic liquid crystalline molecules in this order, wherein the alignment film has carbon atoms in a side chain. An optical compensatory sheet comprising a polymer having 10 or more hydrocarbon groups, wherein the discotic liquid crystalline molecules are oriented at an average tilt angle in the range of 50 to 90 degrees. 2. The optical compensation sheet according to claim 1, wherein the main chain of the polymer has a polyimide structure. 3. The optical compensation sheet according to claim 1, wherein the polymer has a steroid structure in a main chain or a side chain. 4. The optical compensatory sheet according to claim 1, wherein the discotic liquid crystalline molecules are twisted and have a twist angle in a range of 90 to 360 degrees. 5. An STN liquid crystal cell, two polarizing plates disposed on both sides thereof, and one or two optical compensation sheets disposed between the STN liquid crystal cell and one or both polarizing plates. An optical compensation sheet comprising a transparent support, an alignment film, and an optically anisotropic layer formed from discotic liquid crystal molecules in this order from the polarizing plate side, wherein the alignment film is The chain includes a polymer having a hydrocarbon group having 10 or more carbon atoms in the chain, and the discotic liquid crystalline molecules are oriented at an average tilt angle in the range of 50 to 90 degrees, and further twisted, and the twist angle is 90 to 90. An STN liquid crystal display device having a range of 360 degrees. 6. An alignment film containing a polymer having a hydrocarbon group having 10 or more carbon atoms in a side chain, from 50 to 9
A method of aligning discotic liquid crystalline molecules at an average tilt angle in the range of 0 degrees. 7. An optical compensatory sheet comprising, in this order, an alignment film and an optically anisotropic layer formed of discotic liquid crystalline molecules on a transparent support, wherein the alignment film contains a fluoropolymer, and 50 tick liquid crystal molecules
An optical compensatory sheet, wherein the optical compensatory sheet is oriented at an average inclination angle in the range of 90 to 90 degrees. 8. The optical compensation sheet according to claim 7, wherein the main chain of the fluoropolymer has a polyimide structure. 9. The fluorine-containing polymer having a fluorine atom of 0.1.
The optical compensatory sheet according to claim 7, wherein the optical compensatory sheet is contained in a proportion of from 05 to 80% by weight. 10. The optical compensatory sheet according to claim 7, wherein the discotic liquid crystal molecules are twist-aligned, and the twist angle is in a range of 90 to 360 degrees. 11. An STN liquid crystal cell, two polarizing plates disposed on both sides thereof, and one or two optical compensation sheets disposed between the STN liquid crystal cell and one or both polarizing plates. An optical compensatory sheet comprising a transparent support, an alignment film and an optically anisotropic layer formed from discotic liquid crystal molecules in this order from the polarizing plate side. Including a fluoropolymer, the discotic liquid crystalline molecules are oriented at an average tilt angle in the range of 50 to 90 degrees, and further twisted,
An STN liquid crystal display device having a twist angle in the range of 90 to 360 degrees. 12. A method for aligning discotic liquid crystalline molecules at an average tilt angle in the range of 50 to 90 degrees using an alignment film containing a fluoropolymer.