JP2001290022A - Optical compensation sheet and stn (super twisted nematic) liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical compensation sheet suited for an STN liquid crystal display device. SOLUTION: The optical compensation sheet used by being laminated on a liquid crystal display panel using rod-shaped liquid crystalline molecules 13a-13e and an STN liquid crystal display device have an optically anisotropic layer formed of a transparent supporting body 23 and discotic liquid crystalline molecules 21a-21e. The discotic liquid crystalline molecules 21a-21e are aligned practically as a mono-domain with an average inclined angle in 50-90 deg. range.

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 an optically anisotropic layer formed of discotic liquid crystal molecules on a transparent support and an STN type liquid crystal display.

[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 crystal molecules are twist-aligned at 90 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 JP-A-7-104.
No. 284 and No. 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 to use an optical compensation sheet using discotic liquid crystal molecules 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. H10-157, it is difficult to uniformly align the discotic liquid crystalline molecules from the interface of the alignment film to the air interface. If the discotic liquid crystal molecules are not uniformly monodomain aligned (in other words, dual domain aligned), light scattering due to disclination occurs, and the contrast ratio of the displayed image decreases. Research on a technology for substantially vertically aligning (homeotropically aligning) rod-like liquid crystal molecules used in a liquid crystal cell has been advanced. 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.
t) In a liquid crystal cell in a liquid crystal mode, an alignment film for aligning rod-like liquid crystal molecules substantially vertically is required. Various alignment films have been proposed for rod-like liquid crystal molecules. However, it is difficult to uniformly align the discotic liquid crystal molecules in the monodomain from the alignment film interface to the air interface only by using the alignment film of rod-like liquid crystal molecules.

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 optical compensation sheet in which discotic liquid crystalline molecules are uniformly monodomain and substantially vertically (homogeneously) oriented.
Further, an object of the present invention is to eliminate coloring of a display image,
Another object of the present invention is to provide an STN-type liquid crystal display device capable of obtaining a clear image with high contrast.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical compensatory sheet of the following (1) to (3) and an S sheet of the following (4).
This was achieved by a TN type liquid crystal display device. (1) An optical compensatory sheet having an optically anisotropic layer formed from a transparent support and discotic liquid crystal molecules, wherein the discotic liquid crystal molecules have substantially an average tilt angle in the range of 50 to 90 degrees. An optical compensatory sheet characterized by having a monodomain orientation. (2) The optical compensatory sheet according to (1), wherein the discotic liquid crystal molecules are twist-oriented, and the twist angle is in a range of 90 to 360 degrees. (3) 0.005 to 0.5 g / m ^{2 of the} optically anisotropic layer
The optical compensatory sheet according to (1), which comprises a cellulose ester in an amount in the range of (1). (4) The optical compensation sheet according to (3), wherein the cellulose ester is a lower fatty acid ester of cellulose.

(5) The optical device according to (1), wherein the optically anisotropic layer contains a liquid crystal alignment accelerator represented by the following formula (I) in an amount ranging from 0.005 to 0.5 g / m ^2. Compensation sheet. (I) (Hb-) in _m L (-Bu) _n [Formula, Hb consists fluorine-substituted alkyl group, fluorine-substituted aryl group, the alkyl group and alkyl-substituted oligosiloxanoxy group having 6 or more carbon atoms A hydrophobic group selected from the group; Bu is a group having an excluded volume effect containing at least two cyclic structures; L is (m +
n) a valent linking group; and m and n are each independently an integer from 1 to 12]. (6) In the formula (I), m and n are each 1 and L is -alkylene group-, -O-, -CO-,-
NR -, - SO ₂ - and a divalent linking group selected from the group consisting of optical compensation sheet according to R is a hydrogen atom or an alkyl group (5). (7) The optical compensation sheet according to (5), wherein in the formula (I), the group having an excluded volume effect of Bu contains a tricyclic or tetracyclic fused ring. (8) The optical compensation sheet according to (5), wherein in the formula (I), the group having an excluded volume effect of Bu has a structure in which at least two rings are bonded by a single bond, a vinylene bond, or an ethynylene bond.

(9) 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 STN type liquid crystal display device comprising:
The optical compensation sheet has a transparent support and an optically anisotropic layer formed from discotic liquid crystal molecules in this order from the polarizing plate side, and the discotic liquid crystal molecules have an average tilt angle in the range of 50 to 90 degrees. Substantially monodomain orientation and further twist orientation, with a twist angle of 90 to 3
An STN liquid crystal display device having a range of 60 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). The state in which the discotic liquid crystal molecules are oriented at an average tilt angle in the range of 50 to 90 degrees is referred to as the discotic liquid crystal molecules being substantially vertically oriented. Whether or not the discotic liquid crystal molecules are monodomain aligned or not (dual domain alignment) can be easily confirmed by observation with a polarizing microscope.

[0010]

As a result of the research, the present inventor has succeeded in substantially vertically (homogeneously) and uniformly monodomain aligning the discotic liquid crystal molecules. Specifically, by using an appropriate amount of an additive (cellulose ester or liquid crystal alignment accelerator) and adjusting the alignment temperature, the discotic liquid crystal molecules can be substantially vertically and uniformly monodomain aligned. In other words, if the discotic liquid crystal molecules are substantially vertically aligned without using an appropriate amount of the additive and adjusting the alignment temperature, dual domain alignment will result. By obtaining a means for stably aligning discotic liquid crystal molecules in a substantially vertical and uniform direction in a monodomain, ST
It has become possible to manufacture an optical compensation sheet suitable for an N-type liquid crystal display device. By using an optical compensation sheet in which discotic liquid crystal molecules are substantially vertically monodomain aligned (preferably, further twisted),
Coloring of the display image of the STN liquid crystal display device is eliminated, and a clear image with high contrast can be obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of discotic liquid crystalline molecules oriented substantially vertically (dual domain or mono domain). (A) of FIG.
This is a state in which discotic liquid crystal molecules are dual-domain aligned at an average tilt angle of 90 degrees. Each discotic liquid crystal molecule is oriented with a tilt angle of 60 to 80 degrees, but two discotic liquid crystal molecules tilted in opposite directions form a pair (dual domain alignment). Therefore, the average inclination angle is 90 degrees as a whole. Generally, the discotic liquid crystalline molecules on the side closer to the alignment film (22) have a high tilt angle (8 in the figure).
Discotic liquid crystal molecules on the opposite side (air interface side) are oriented at a low tilt angle (60 degrees in the figure). In the prior art, it is considered that the discotic liquid crystalline molecules that were substantially vertically aligned were in such a dual domain alignment state. Discotic liquid crystal molecules in a dual domain alignment state cause light scattering due to disclination. FIG. 1B shows a state in which the discotic liquid crystalline molecules are monodomain aligned at an average tilt angle of 90 degrees. In FIG. 1B, each discotic liquid crystalline molecule is oriented with a tilt angle of 90 degrees. FIG. 1C shows a state where the discotic liquid crystal molecules are monodomain aligned at an average tilt angle of 70 degrees. In FIG. 1C, the individual discotic liquid crystalline molecules are oriented with a tilt angle of 60 to 80 degrees. Unlike FIG. 1A, the discotic liquid crystal molecules are all tilted in the same direction (monodomain alignment), so that the average tilt angle as a whole is 70 degrees. As shown in FIG. 1 (b) or (c), by aligning the discotic liquid crystal molecules in a monodomain,
Light scattering due to disclination can be prevented.

FIG. 2 shows the alignment state of rod-like liquid crystal molecules in a liquid crystal cell and the alignment of discotic liquid crystal molecules in an optically anisotropic layer in a pixel portion of an STN type liquid crystal display device when no voltage is applied (off). It is sectional drawing which shows a state typically. As shown in FIG. 2, the liquid crystal cell includes rod-like liquid crystal molecules (13a) between an alignment film (12) below the upper substrate (11) and an alignment film (14) above the lower substrate (15). To e) are enclosed in a liquid crystal layer. Alignment film (12, 14)
The rod-like liquid crystalline molecules (13a to 13e) are twist-aligned as shown in FIG. 2 due to the function of the chiral agent added to the liquid crystal layer. Although omitted in FIG. 2, the upper substrate (11) and the lower substrate (15) of the liquid crystal cell each have an electrode layer. The electrode layer has a function of applying a voltage to the rod-like liquid crystal molecules (13a to 13e). When the applied voltage of the STN type liquid crystal cell is 0 (when no voltage is applied), as shown in FIG. 2, the rod-like liquid crystal molecules (13a to 13e) are aligned with the alignment films (12,
It is oriented substantially parallel (in the horizontal direction) to the plane of 14).
The rod-like liquid crystal molecules (13a to 13e) form a spiral in the horizontal plane while being twisted along the thickness direction (in FIG. 2, from 13a to 13e, approximately 240 ° counterclockwise).
It is oriented in such a direction. When a voltage is applied (on) to the STN-type liquid crystal cell, the rod-like liquid crystal molecules (13b to 13d) in the central portion of the liquid crystal cell are not applied with a voltage (of
f) Orientation is performed more vertically (rearranged in parallel to the direction of the electric field) than in the case of (f). 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. 2 has an alignment film (22) and an optically anisotropic layer in this order on a transparent support (23). 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.
e) The disk surface is oriented substantially perpendicular to the surface of the vertical alignment film (22). Then, as shown in FIG. 2, the discotic liquid crystal molecules (21a to 21e) spiral in a horizontal plane while being twisted along the thickness direction (in FIG. 2, approximately 240 ° clockwise from 21a to 21e). ). In FIG. 2, rod-like liquid crystal molecules and discotic liquid crystal molecules are represented by 13a
And 21e, 13b and 21d, 13c and 21c, 13d and 21b, and 13e and 21a, respectively. 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. 3 is a schematic diagram showing the refractive index ellipsoids of the rod-like liquid crystal molecules of the liquid crystal cell and the discotic liquid crystal molecules of the optical compensatory 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 crystal molecules of the optical compensatory sheet which has a relationship of optically compensating the rod-like liquid crystal 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. 4 is a schematic diagram showing a layer structure of an STN type liquid crystal display device. The liquid crystal display device shown in FIG. 4A 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. 4B 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. 4C 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. 4D 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. 4E includes a lower polarizing plate (3a) and a lower optical compensation sheet (2) in order from the backlight (BL) side.
a), STN type liquid crystal cell (1), upper optical compensation sheet (2)
b) and the upper polarizing plate (3b).
In FIG. 4, the transmission axis of the lower polarizing plate (3a) (T
Aa), the discotic liquid crystal molecules on the lower polarizing plate side of the lower optical compensatory sheet (2a) in the normal direction (director) direction (DDa) of the discotic liquid crystal molecules, and the lower optical compensating sheet (2a) discotic on the upper polarizing plate side Direction (DDb) in the direction of the normal (director) of the disk surface of the liquid crystal molecules, rubbing direction (RDa) of the lower alignment film of the liquid crystal cell (1), rubbing direction (RDb) of the upper alignment film of the liquid crystal cell (1), The direction (DDc) of the normal (director) of the discotic liquid crystal molecules on the lower polarizing plate side of the optical compensatory sheet (2b) to the discotic liquid crystal molecules on the upper polarizing plate side of the upper optical compensatory sheet (2b). Normal (Director) direction of the disk surface (DD
d) and the transmission axis (TAb) of the upper polarizing plate (3b). The exact angles are described in FIGS. 5 and 6.

FIG. 5 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. 5 (a) shows the lower polarizing plate and the ST as shown in FIG. 4 (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. 5, 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. (C) of FIG. 5 is (c) of FIG.
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. (D) of FIG.
FIG. 4D 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. 5 (e) shows one optical compensation sheet between the lower polarizing plate and the STN type liquid crystal cell and between the STN type liquid crystal cell and the upper polarizing plate as shown in FIG. 4 (e). This is a case in which 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. 6 is a plan view showing another preferred optical direction for each element of the STN type liquid crystal display device.
FIG. 6 shows an arrangement in which color is emphasized. FIG. 6A shows:
As shown in FIG. 4A, this is a case where one optical compensation sheet is provided between the lower polarizing plate and the STN type liquid crystal cell. FIG. 6B 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. 4B. FIG. 6C shows a case where one optical compensation sheet is provided between the STN liquid crystal cell and the upper polarizing plate as shown in FIG. 4C. FIG. 6D 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. 4D. FIG. 6 (e) shows the lower polarizer and ST as shown in FIG. 4 (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. To improve the adhesion between the transparent support and the layer provided thereon (adhesion 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] In order to align discotic liquid crystalline molecules substantially vertically (homogeneously),
It is important to lower the surface energy of the alignment film. 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 is effective. In order to make the hydrocarbon group exist on the surface of the alignment film, it is preferable to introduce the hydrocarbon group into a side chain rather than 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). As the cycloalkyl group or cycloalkenyl group, an aliphatic group having a steroid ring is preferable. As the aromatic group, a group having a tolan structure or a biphenyl structure is preferable. 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 1
It is preferably 0 to 100, more preferably 10 to 60, and most preferably 10 to 40. The main chain of the polymer preferably has a polyimide structure, a polyvinyl alcohol structure or a poly (meth) acrylic acid 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. The hydrocarbon group may be present in the repeating unit derived from a tetracarboxylic acid, may be present in the repeating unit derived from a diamine, or may be present in both repeating units. When a hydrocarbon group is introduced into a polyimide, it is particularly preferable to form a steroid structure in the main chain or side chain of the polyimide. The steroid structure present in the side chain corresponds to a hydrocarbon group having 10 or more carbon atoms, and has a function of aligning the discotic liquid crystal molecules substantially vertically (homogeneously). 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.

A modified polyvinyl alcohol having a hydrocarbon group having 10 or more carbon atoms can also align discotic liquid crystal molecules substantially vertically (homogeneously). 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 preferably 10 to 100, more preferably 10 to 60, and more preferably 10 to 60.
Most preferably, it is from 40 to 40. The modified polyvinyl alcohol having a hydrocarbon group contains 2 to 80 mol% of a repeating unit having a hydrocarbon group having 10 or more carbon atoms.
And more preferably 3 to 70 mol%.

A preferred modified polyvinyl alcohol having a hydrocarbon group having 10 or more carbon atoms is represented by the following formula (P
V). (PV)-(VAl) x- (HyC) y- (VAc) z- wherein VA1 is a vinyl alcohol repeating unit; HyC is a repeating unit having a hydrocarbon group having 10 or more carbon atoms. VAc is a vinyl acetate repeating unit; x is 20 to 95 mol% (preferably 2 to 95 mol%)
Y is from 2 to 80 mol%)
(Preferably 3 to 70 mol%); and z is 0 to 30 mol% (preferably 2 to 20 mol%). Preferred repeating units (HyC) having a hydrocarbon group having 10 or more carbon atoms are represented by the following formulas (HyC-I) and (HyC-II).

[0025]

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Wherein L ¹ is —O—, —CO—, —SO
₂ -, - NH-, an alkylene group, an arylene group and a divalent linking group selected from their combinations; L
² is a single bond or -O -, - CO -, - SO 2 -,
-NH-, a divalent linking group selected from an alkylene group, an arylene group and a combination thereof;
¹ and R ² are each a hydrocarbon group having 10 or more carbon atoms. Examples of the divalent linking group formed by the above combination are shown below.

[0027] L1: -O-CO- L2: -O -CO- alkylene group -O- L3: -O-CO- alkylene group -CO-NH- L4: -O-CO- alkylene group -NH-SO ₂ -Arylene group -O-L5: -arylene group -NH-CO-L6: -arylene group -CO-O-L7: -arylene group -CO-NH-L8: -arylene group -O-L9: -O-CO -NH-arylene group -NH-CO-

Preferred modified poly (meth) acrylic acid having a hydrocarbon group having 10 or more carbon atoms is represented by the following formula (P
A). (PA)-(VAA) x- (HyC) y- wherein VAA is a (meth) acrylic acid repeating unit; HyC is a repeating unit having a hydrocarbon group having 10 or more carbon atoms; x is 20 to 98 mol%
(Preferably 30-97 mol%); and y
Is 2 to 80 mol% (preferably 3 to 70 mol%)
It is. The definition and examples of the repeating unit (HyC) having a hydrocarbon group having 10 or more carbon atoms are the same as those of the modified polyvinyl alcohol.

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. 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 (homogeneously) aligned using the alignment film, the discotic liquid crystal molecules are fixed in the aligned state to form an optically anisotropic layer. Only the anisotropic layer may be transferred onto a polymer film (or a transparent support). Discotic liquid crystalline molecules fixed in an aligned state can maintain the aligned state without an alignment film. Therefore, in the optical compensation sheet of the present invention, the alignment film is not an essential element (although it is essential in the production of the optical compensation sheet).

[Optically 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 crystalline molecules are described in various references (C. Destrade et al., Mol. Crysr. Liq. Cryst., V
ol. 71, page 111 (1981); edited by The Chemical Society of Japan, quarterly chemistry review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2
(1994); B. Kohne et al., Angew. Chem. Soc. Chem. C
omm., page 1794 (1985); J. Zhang et al., J. Am. Che
m. Soc., vol. 116, page 2655 (1994)). Regarding the polymerization of discotic liquid crystalline molecules,
It is described in JP-A-8-27284. In order to fix the discotic liquid crystal molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystal molecules. 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) 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).

[0033]

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[0034]

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[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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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 crystal molecule can be twisted 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 -

[0047] _{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 −

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.

[0050]

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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) (a molecule having a hydrogen atom instead of Q in the above formula) 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.

Instead of introducing an asymmetric carbon atom into the divalent linking group (L) of the discotic liquid crystal molecule, an optically active compound (chiral agent) containing the asymmetric carbon atom is replaced with an optically anisotropic layer. , The discotic liquid crystal 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.

[Cellulose Ester] The discotic liquid crystal molecules are substantially vertically (homogeneously) and uniformly monodomain aligned on the air interface side.
Cellulose esters can be added to the optically anisotropic layer. As the cellulose ester, it is preferable to use a lower fatty acid ester of cellulose. 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
It is preferably 2 to 5, and more preferably 2 to 4. Substituents (eg, hydroxy) for fatty acids
May be bonded. 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 the cellulose acetate butyrate is preferably 30% or more, and 30 to 80%.
% Is more preferable. The acetylation degree of cellulose acetate butyrate is preferably 30% or less, more preferably 1 to 30%.
Cellulose ester is 0.005 to 0.5 g / m ^2.
Use in amounts in the range. The amount used is 0.01 to 0.4
It is preferably in the range of 5 g / m ² , more preferably in the range of 0.02 to 0.4 / m ² , and more preferably in the range of 0.
Most preferably, it is in the range of 03 to 0.35 / m ² . It is also preferable to use 0.1 to 5% by weight of the discotic liquid crystal molecules.

[Liquid Crystal Alignment Accelerator] In order to cause the discotic liquid crystal molecules to be substantially vertically (homogeneously) and uniformly monodomain aligned even on the air interface side, the compound represented by the formula (I) is used to promote liquid crystal alignment. It can also be used as an agent. (I) (Hb-) _m L (-Bu) _{n In the} formula (I), Hb represents a fluorine-substituted alkyl group, a fluorine-substituted aryl group, an alkyl group having 6 or more carbon atoms, and an alkyl-substituted oligosiloxanoxy group. And a hydrophobic group selected from the group consisting of The fluorine-substituted alkyl group may have a cyclic structure or a branch. The fluorine-substituted alkyl group preferably has 1 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, and more preferably 3 to 30 carbon atoms.
More preferably from 20 to 20, still more preferably from 4 to 15, and most preferably from 6 to 12. The proportion of the fluorine atom replacing the hydrogen atom of the alkyl group is preferably 50 to 100%, more preferably 60 to 100%, and 7%.
It is more preferably 0 to 100%, further preferably 80 to 100%, and 85 to 1
Most preferably, it is 00%. The fluorine-substituted aryl group is preferably a fluorine-substituted phenyl. The proportion of the fluorine atom replacing the hydrogen atom of the aryl group is
It is preferably 50 to 100%, and 60 to 10%.
The content is more preferably 0%, further preferably 70 to 100%, still more preferably 80 to 100%, and most preferably 85 to 100%.

The alkyl group having 6 or more carbon atoms may have a cyclic structure or a branch. The number of carbon atoms of the alkyl group is preferably from 6 to 60, more preferably from 7 to 50, still more preferably from 8 to 40, still more preferably from 9 to 30, and further preferably from 10 to Most preferably, it is 20. The alkyl-substituted oligosiloxanoxy group is a group represented by the following formula. R ^1- (SiR ² ₂ -O) _q- wherein R ¹ is a hydrogen atom, a hydroxyl or an alkyl group; R ² is a hydrogen atom or an alkyl group and at least one of a plurality of R ² Is an alkyl group;
Then, q is an integer of 2 to 12. It is particularly preferred that R ¹ is hydroxyl. It is particularly preferred that each of the plurality of R ² is an alkyl group. q is 2
It is preferably an integer of from 8 to 8, more preferably 3, 4, 5 or 6. The alkyl group may have a cyclic structure or a branch. The number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 6, still more preferably 1 to 4, and 1 ( Most preferably, it is methyl) or 2 (ethyl). Below, the example of a hydrophobic group (Hb) is shown.

[0056] (Hb-1) n-C 8 F 17 - (Hb-2) H-C 8 F 16 - (Hb-3) tetrafluorophenyl - (Hb-4) H- C 6 F 12 - (Hb _{-5) H-C 4 F 8} - (Hb-6) HO- (Si (CH 3) 2 -O) 4 - (Hb-7) n-C 12 H 25 -

In the formula (I), Bu is a group having at least two cyclic structures and having an excluded volume effect. The cyclic structure includes an aliphatic ring, an aromatic ring, and a heterocyclic ring. The ring having a cyclic structure is preferably a 5-, 6-, or 7-membered ring, more preferably a 5- or 6-membered ring, and most preferably a 6-membered ring. The relationship between the two ring structures includes fused ring formation, spiro bond, single bond, and bond via a divalent linking group. Preference is given to condensed ring formation, a single bond and a bond via a divalent linking group. When at least two cyclic structures form a fused ring, it is preferably a tricyclic fused ring or a tetracyclic fused ring. When at least two ring structures are bonded via a divalent linking group, examples of the divalent linking group include -O-, -C
O-, -alkylene group-, vinylene bond (-CH = CH
-), Ethynylene bonds (-C≡C-) and combinations thereof. The divalent linking group is preferably a vinylene bond or an ethynylene bond, and more preferably an ethynylene bond. In the ring of the cyclic structure,
The substituent may be bonded. Examples of the substituent include a halogen atom, hydroxyl, cyano, nitro, an alkyl group (preferably an alkyl group having 1 to 5 carbon atoms),
Substituted alkyl groups (eg, carboxyalkyl groups, alkoxyalkyl groups), alkoxy groups, substituted alkoxy groups (eg, oligoalkoxy groups), alkenyloxy groups (eg, vinyloxy), acyl groups (eg, acryloyl,
Methacryloyl), acyloxy groups (eg, acryloyloxy, benzoyloxy) and epoxy groups (eg, epoxyethyl). Hereinafter, examples of the group (Bu) having an excluded volume effect will be described.

[0058]

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[0059]

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[0060]

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[0061]

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[0062]

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[0063]

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[0064]

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[0065]

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In the formula (I), L is a (m + n) -valent linking group. In the formula (I), m and n are each independently an integer of 1 to 12. m and n are
Each is preferably 1 to 8, more preferably 1 to 6, still more preferably 1 to 4, still more preferably 1 to 3,
Most preferably, it is 1. If in formula (I), m and n are each 1, L is - alkylene group -, - O -, - CO -, - NR -, - SO ₂ - and selected from the group consisting of The divalent linking group is preferably R is a hydrogen atom or an alkyl group. L preferably contains at least one polar group (group other than -alkylene group-). The alkylene group preferably has 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, and preferably 1 to 2 carbon atoms.
It is more preferably 0, still more preferably 1 to 15, and most preferably 1 to 12. The number of carbon atoms in the alkyl group is preferably 1 to 40, more preferably 1 to 30, still more preferably 1 to 20, still more preferably 1 to 15. Most preferably, it is from 12 to 12.

When m is 2 or more, a plurality of hydrophobic groups (H
b) may be different. When n is 2 or more, the groups (Bu) having a plurality of excluded volume effects may be different. When m or n is 2 or more, the linking group (L) can form a chain structure or a cyclic structure. When the linking group (L) has a chain structure, a plurality of hydrophobic groups (Hb) or a plurality of groups having a excluded volume effect (Bu) can be bonded to the main chain linking group (L) as a side chain. . When the linking group (L) has a cyclic structure, a plurality of hydrophobic groups (Hb) or a plurality of groups having a excluded volume effect (Bu) can be bonded to the linking group (L) of the cyclic structure as a substituent. Hereinafter, examples of the linking group (L) are shown. (L-1) which is a divalent linking group
In (L-11), the left side is bonded to a hydrophobic group (Hb),
The right side binds to a group (Bu) having an excluded volume effect. For the polyvalent linking groups (L-12) to (L-16), a hydrophobic group (Hb) and a group having an excluded volume effect (Bu) are indicated.

(L-1) -SO ₂ -N (n-C ₃ H ₇ )
_{-C 2 H 4 -O-CO-} O- (L-2) -SO 2 -N (n-C 3 H 7) -C 2 H 4 -
O-CO-NH- (L- 3) -SO 2 -N (n-C 3 H 7) -C 2 H 4 -
_{O-CO-O-CH 2} - (L-4) -SO 2 -NH-C 2 H 4 -O-CO-NH
_{- (L-5) -SO 2} -NH-C 2 H 4 -O-CO-O- (L-6) -CO-NH-C 2 H 4 -O-CO-O- (L-7) - CO-NH- (L-8) -NH-C 2 H 4 -O-CO-O- (L-9) -CO-NH-C 2 H 4 -O-CO-NH- (L-10) - _{SO 2 -N (n-C 3} H 7) -C 6 H 12 -
O-CO-NH- (L- 11) -C 2 H 4 -O-CO-O-

[0069]

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[0070]

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[0071]

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[0072]

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[0073]

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The liquid crystal alignment accelerator is a compound in which the above-described hydrophobic group (Hb), a group having an excluded volume effect (Bu), and a linking group (L) are combined. There is no particular limitation on these combinations. Hereinafter, specific examples of the liquid crystal alignment accelerator represented by the formula (I) are shown. The hydrophobic group (Hb), the group having an excluded volume effect (Bu), and the linking group (L) in each example are the numbers of the examples described above.

I-1: (Hb-1)-(L-1)-(Bu-1) I-2: (Hb-1)-(L-2)-(Bu-2) I-3: ( Hb-1)-(L-1)-(Bu-3) I-4: (Hb-1)-(L-1)-(Bu-4) I-5: (Hb-1)-(L- 3)-(Bu-5) I-6: (Hb-1)-(L-1)-(Bu-6) I-7: (Hb-1)-(L-1)-(Bu-7) I-8: (Hb-1)-(L-3)-(Bu-1) I-9: (Hb-1)-(L-4)-(Bu-2) I-10: (Hb-1) )-(L-5)-(Bu-8) I-11: (Hb-1)-(L-2)-(Bu-9) I-12: (Hb-1)-(L-5)- (Bu-10) I-13: (Hb-1)-(L-6)-(Bu-11)

I-14: (Hb-2)-(L-7)-(Bu-7) I-15: (Hb-3)-(L-8)-(Bu-1) I-16: ( Hb-4)-(L-9)-(Bu-2) I-17: (Hb-5)-(L-6)-(Bu-8) I-18: (Hb-1)-(L- 10)-(Bu-9) I-19: (Hb-1)-(L-5)-(Bu-12) I-20: (Hb-6)-(L-11)-(Bu-12) I-21: (Hb-7)-(L-7)-(Bu-7) I-22: (Hb-1) _3- (L-12)-(Bu-2) ₃ I-23: (Hb _{-1) 3 - (L-13} ) - (Bu-2) 3 I-24: (Hb-1) 3 - (L-14) - (Bu-1) 3 I-25: (Hb-1) 4 - (L-15) - ( Bu-1) 4 I-26: (Hb-1) 4 - (L-16) - (Bu-2) 4

Two or more liquid crystal alignment promoters may be used in combination. The liquid crystal alignment promoter is 0.005 to 0.5 g / m2.
Use in amounts in the range of ² . The amount used is from 0.01 to 0.1.
It is preferably in the range of 45 g / m ² , more preferably in the range of 0.02 to 0.4 g / m ² ,
Most preferably, it is in the range of 0.03 to 0.35 g / m ² . In addition, the liquid crystal alignment promoter is preferably used in an amount of 0.01 to 20% by weight, more preferably 0.1 to 5% by weight, based on the amount of the discotic liquid crystal molecules.

[Formation of Optically Anisotropic Layer] The optically anisotropic layer comprises a discotic liquid crystalline molecule, if necessary, a cellulose ester, a liquid crystal alignment promoter, a compound containing an asymmetric carbon atom, Alternatively, it is formed by applying a coating solution containing the following polymerizable initiator and other additives on the vertical alignment film. 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), and heterocyclic compounds (eg,
Pyridine), hydrocarbon (eg, benzene, hexane), alkyl halide (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 application of the coating solution is performed by a known method (eg, an extrusion coating method,
Direct gravure coating method, reverse gravure coating method, die coating method, bar coating method). The thickness of the optically anisotropic layer is
0.1 to 50 μm, preferably 1 to 30 μm.
μm, more preferably 5 to 20 μm. When two optical compensatory sheets are used in a liquid crystal display device, the thickness may be half the thickness of the optically anisotropic layer 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, the inclination angle may change continuously along the thickness direction of the optically anisotropic layer.

The twist angle of the discotic liquid crystal molecules (twist angle) 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 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.

By heating the formed optically anisotropic layer, the discotic liquid crystalline molecules are substantially monodomain aligned at an average tilt angle in the range of 50 to 90 degrees. The heating temperature is
It is preferable that the following formula (T1) is satisfied. (T1) T _NI −0.5 × (T _NI −T _CN ) ≦ T <T _{NI In the} formula, T is a heating temperature (° C.) of the optically anisotropic layer;
T _NI is the nematic of discotic liquid crystalline molecules-
Isotropic transition temperature (° C.); and T _CN
Is the crystal-nematic transition temperature (° C.) of the discotic liquid crystalline molecule. When a columnar phase appears, T _CN is the crystal-columnar phase transition temperature (° C.) of the discotic liquid crystalline molecule. The heating temperature (T)
More preferably, the following formula (T2) is satisfied, and most preferably, the following formula (T3) is satisfied. (T2) T _NI −0.3 × (T _NI −T _CN ) ≦ T <T _NI (T3) T _NI −0.2 × (T _NI −T _CN ) ≦ T <T _NI The nematic-isotropic transition temperature and the crystal-nematic transition temperature of discotic liquid crystalline molecules vary depending not only on the type of discotic liquid crystalline molecules but also on the composition of the optically anisotropic layer. Therefore, before forming the optically anisotropic layer, a preliminary experiment is performed on the optically anisotropic layer having the same composition to measure the transition temperature. The transition temperature can be easily measured by heating the optically anisotropic layer while observing with a polarizing microscope.

The optically anisotropic layer can be heated using various means. The heating time sets the time required for the discotic liquid crystalline molecules to be substantially monodomain aligned. Generally, the heating time is between 10 seconds and 60 minutes. An additive for adjusting the transition temperature of discotic liquid crystalline molecules may be used. Nematic-isotropic transition temperature (T
_{If NI} ) is set to a low value, the heating temperature can be set low. As the additive, it is preferable to use a compound that is compatible with the discotic liquid crystal molecules and does not inhibit the alignment. When a monomer having a polymerizable group (eg, vinyl, vinyloxy, acryloyl, methacryloyl) is added to a discotic liquid crystalline molecule, a nematic-
The isotropic transition temperature can be reduced.
The amount of the additive to be used is preferably 1 to 50% by weight, more preferably 5 to 30% by weight, based on the amount of the discotic liquid crystal molecules.

It is preferable that the discotic liquid crystal molecules that are substantially vertically (homogeneously) aligned are fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction of the polymerizable group (Q) introduced into the discotic liquid crystalline molecule. 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 (US Pat. No. 2,367,661).
No. 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α
-Hydrocarbon-substituted aromatic acyloin compounds (U.S. Pat.
No. 22512), polynuclear quinone compounds (described in U.S. Pat. Nos. 3,046,127 and 2,951,758), and a combination of triarylimidazole dimer and p-aminophenyl ketone (U.S. Pat.
No. 7), acridine and phenazine compounds (JP-A-60-105667, U.S. Pat.
850) and 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 800 mJ / cm ² . Light irradiation may be performed under heating conditions to promote the photopolymerization reaction.

[Liquid crystal display device] The optical compensation sheet produced according to the present invention is particularly effective in an STN type liquid crystal display device. The STN-type liquid crystal display device includes an STN-type liquid crystal cell, a pair of optical compensation sheets disposed on both sides of the liquid crystal cell, an optical compensation sheet disposed on one side of the liquid crystal cell, and a pair of polarizing plates disposed on both sides thereof. Become. 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) is oriented substantially in the same direction (less than ± 10 °) when viewed from the normal direction of the liquid crystal cell. It is preferable to arrange them such that 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.

[0085]

EXAMPLES Example 1 (Preparation of Optical Compensation Sheet A) A 100 μm thick triacetyl cellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) was used as a transparent support. A 4% by weight solution obtained by dissolving the following polyimide in a mixed solvent of N-methyl-2-pyrrolidone, butoxyethanol and methyl ethyl ketone was applied on a transparent support using a # 3 bar coater. The coating layer was dried at 140 ° C. for 2 minutes, and further heated at 62 ° C. for 5 minutes to form an alignment film. The thickness of the alignment film was 0.51 μm.

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A coating solution having the following composition was applied using a # 9 bar coater onto the rubbed alignment film.
By heating at 130 ° C. for 10 minutes, the discotic liquid crystalline compound was aligned. In addition, two types of cellulose acetate butyrate (CAB-551-0.2 and CAB-551
The total coating amount of -531-1) was 0.034 g / m ^2.

<< Coating Liquid for Optically Anisotropic Layer >>デ ィ ス The following discotic liquid crystalline molecules (1) 91 parts by weight The following chiral agent 1.6 parts by weight Cellulose acetate butyrate having a degree of acetylation of 2.0%, a degree of butyrylation of 52.0% and a number average molecular weight of 30,000 (CAB-551-0.2, manufactured by Eastman Chemical Company) 0.25% by weight Part: cellulose acetate butyrate having a degree of acetylation of 3.0%, a degree of butyrylation of 50.0%, and a number average molecular weight of 40,000 (CAB-531-1, manufactured by Eastman Chemical Company) 0.25 parts by weight ethylene oxide-modified trimethylolpropane Triacrylate (V # 360, 9 parts by weight Photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) 3 parts by weight Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1 part by weight Methyl ethyl ketone 120 parts by weight Department ────────────────────────────────────

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While the coating layer was heated to 130 ° C., ultraviolet rays of 500 mJ / cm ² were irradiated using a metal halide lamp to polymerize the terminal vinyl group of the discotic liquid crystal molecule (1) and fix the alignment state. . In this way, an optically anisotropic layer in which the discotic liquid crystalline compound was vertically (homogeneous) and twisted and oriented was formed, and an optical compensation sheet was produced. When Δnd of the obtained optical compensation sheet was measured at a wavelength of 550 nm,
It was 440 nm. Further, the twist angle of the discotic liquid crystal molecules was 120 °. Furthermore, when the alignment state of the discotic liquid crystalline molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).
Was.

Example 2 (Preparation of Optical Compensation Sheet B) Except that the amounts of the two kinds of cellulose acetate butyrate were changed to 1 part by weight (total coating amount: 0.136 g / m ² ), An optical compensatory sheet was produced in the same manner as in Example 1. When the Δnd of the obtained optical compensation sheet was measured, it was 440 nm. Further, the twist angle of the discotic liquid crystal molecules was 120 °. Furthermore, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).

Example 3 (Preparation of Optical Compensation Sheet C) As cellulose acetate butyrate, a degree of acetylation of 2.0% and a degree of butyrylation of 5 were used.
0.5% by weight of only 2.0% cellulose acetate butyrate having a number average molecular weight of 30,000 (CAB-551-0.2, manufactured by Eastman Chemical Company) (coating amount: 0.0
An optical compensatory sheet was produced in the same manner as in Example 1 except that 34 g / m ² ) was used. When the Δnd of the obtained optical compensation sheet was measured, it was 440 nm. Also,
The twist angle of the discotic liquid crystal molecules was 120 °. Furthermore, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).

Example 4 (Preparation of Optical Compensation Sheet D) As cellulose acetate butyrate, the degree of acetylation was 2.0% and the degree of butyrylation was 5
Using only 0.25 parts by weight of 2.0% cellulose acetate butyrate having a number average molecular weight of 30,000 (CAB-551-0.2, manufactured by Eastman Chemical Company), # 18
An optical compensatory sheet was prepared in the same manner as in Example 1, except that the coating liquid for the optically anisotropic layer was applied using the bar coater described in Example 1. Cellulose acetate butyrate (CAB-55
1-0.2) was 0.034 g / m ² . When the Δnd of the obtained optical compensation sheet was measured, it was 880 nm. The twist angle of the discotic liquid crystal molecules was 240 °. Furthermore, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).

Example 5 (Preparation of Optical Compensation Sheet E) The amount of each of the two kinds of cellulose acetate butyrate was changed to 0.125 parts by weight, and the optical anisotropy was measured using a # 18 bar coater. An optical compensatory sheet was prepared in the same manner as in Example 1, except that the coating liquid for the hydrophilic layer was applied. The total coating amount of the two cellulose acetate butyrate was 0.034 g / m ² . When the Δnd of the obtained optical compensation sheet was measured, it was 880 nm. The twist angle of the discotic liquid crystal molecules was 240 °. Furthermore, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).

Example 6 (Preparation of Optical Compensation Sheet F) As cellulose acetate butyrate, the degree of acetylation was 2.0% and the degree of butyrylation was 5
Only 2.5% by weight of 2.0% cellulose acetate butyrate having a number average molecular weight of 30,000 (CAB-551-0.2, manufactured by Eastman Chemical Co., Ltd.) was used, and the optical difference was measured using a # 18 bar coater. An optical compensatory sheet was produced in the same manner as in Example 1 except that the isotropic layer coating solution was applied. Cellulose acetate butyrate (CAB-551
-0.2) was 0.34 g / m ² . When Δnd of the obtained optical compensation sheet was measured, 88
It was 0 nm. The twist angle of the discotic liquid crystal molecules was 240 °. Furthermore, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).

Comparative Example 1 (Preparation of Optical Compensation Sheet X) The amount of the two kinds of cellulose acetate butyrate was changed to 4 parts by weight, and # 18 was obtained.
An optical compensatory sheet was prepared in the same manner as in Example 1, except that the coating liquid for the optically anisotropic layer was applied using the bar coater described in Example 1. The total coating amount of the two cellulose acetate butyrate was 0.544 g / m ² . When the Δnd of the obtained optical compensation sheet was measured, it was 880 nm. The twist angle of the discotic liquid crystal molecules was 240 °. Further, when the alignment state of the discotic liquid crystalline molecules was confirmed with a polarizing microscope, a schlieren pattern was observed, and the molecules were not uniformly aligned (monodomain alignment).

[Comparative Example 2] (Preparation of optical compensation sheet Y) Example 1 was repeated except that cellulose acetate butyrate was not added, and an optically anisotropic layer coating solution was applied using a # 18 bar coater. An optical compensatory sheet was produced in the same manner as described above. When the Δnd of the obtained optical compensation sheet was measured, it was 880 nm. The twist angle of the discotic liquid crystal molecules is 240
Was ゜. Further, when the alignment state of the discotic liquid crystalline molecules was confirmed by a polarizing microscope, two types of alignment states (dual domain alignment) having different tilt directions were recognized, although the Δnd and the twist angle were equal.

Example 7 (Production of Liquid Crystal Display) Twist Angle: 240 °, Δnd
Are placed under the 880 nm STN liquid crystal cell, two optically compensatory sheets A prepared in Example 1 with the optically anisotropic layer facing each other. (The normal direction of the disc surface of the discotic liquid crystal molecules). On the surface where the optical compensation sheet and the liquid crystal cell are bonded,
The optical compensation sheet was attached to the liquid crystal cell such that the director of the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal molecules of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. The contrast ratio of the manufactured STN-type liquid crystal display device was measured using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 1.

Example 8 (Production of Liquid Crystal Display) Twist Angle: 240 °, Δnd
The discotic liquid crystal properties of the optically anisotropic layer were determined by setting one optical compensation sheet A prepared in Example 1 on both sides of an 880 nm STN liquid crystal cell and the optically anisotropic layer side to the liquid crystal cell side. The directors of the molecules were mounted to match. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. S made
For a TN type liquid crystal display device, a measuring device (EZ-Contrast
160D, manufactured by ELDIM). The results are shown in Table 1.

Example 9 (Production of Liquid Crystal Display) Twist Angle: 240 °, Δnd
Are placed under the 880 nm STN liquid crystal cell, two optically compensatory sheets B prepared in Example 2 with the optically anisotropic layer facing each other. (The normal direction of the disc surface of the discotic liquid crystal molecules). On the surface where the optical compensation sheet and the liquid crystal cell are bonded,
The optical compensation sheet was attached to the liquid crystal cell such that the director of the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal molecules of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. The contrast ratio of the manufactured STN-type liquid crystal display device was measured using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 1.

Example 10 (Production of liquid crystal display device) Twist angle was 240 °, Δnd
The two optically compensatory sheets C prepared in Example 3 were placed under the 880 nm STN liquid crystal cell, with the optically anisotropic layer side facing each other, and the director of the discotic liquid crystalline molecules of the optically anisotropic layer was used. (The normal direction of the disc surface of the discotic liquid crystal molecules) was bonded. On the surface where the optical compensation sheet and the liquid crystal cell are bonded,
The optical compensation sheet was attached to the liquid crystal cell such that the director of the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal molecules of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. The contrast ratio of the manufactured STN-type liquid crystal display device was measured using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 1.

[Example 11] (Production of liquid crystal display device) Twist angle was 240 °, Δnd
Below the 880 nm STN liquid crystal cell, one optical compensation sheet D prepared in Example 4, the optically anisotropic layer side on the liquid crystal cell side, and the surface where the optical compensation sheet and the liquid crystal cell are bonded to each other. The optical compensation sheet was attached to the liquid crystal cell so that the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal cell of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. The contrast ratio of the manufactured STN-type liquid crystal display device was measured using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 1.

Example 12 (Production of Liquid Crystal Display) Twist Angle: 240 °, Δnd
Below the 880 nm STN liquid crystal cell, one optical compensation sheet E prepared in Example 5, the optically anisotropic layer side on the liquid crystal cell side, and the surface where the optical compensation sheet and the liquid crystal cell are bonded to each other. The optical compensation sheet was attached to the liquid crystal cell so that the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal cell of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. The contrast ratio of the manufactured STN-type liquid crystal display device was measured using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 1.

Example 13 (Production of Liquid Crystal Display) Twist Angle: 240 °, Δnd
Below the 880 nm STN liquid crystal cell, one optical compensation sheet F prepared in Example 6, the optically anisotropic layer side on the liquid crystal cell side, and the surface where the optical compensation sheet and the liquid crystal cell are bonded to each other. The optical compensation sheet was attached to the liquid crystal cell so that the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal cell of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. The contrast ratio of the manufactured STN-type liquid crystal display device was measured using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 1.

Comparative Example 3 (Production of Liquid Crystal Display Device) Twist Angle: 240 °, Δnd
Below the 880 nm STN liquid crystal cell, one optical compensation sheet X prepared in Comparative Example 1, the optically anisotropic layer side is the liquid crystal cell side, and the surface where the optical compensation sheet and the liquid crystal cell are bonded is The optical compensation sheet was attached to the liquid crystal cell so that the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal cell of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. The contrast ratio of the manufactured STN-type liquid crystal display device was measured using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 1.

Comparative Example 4 (Production of Liquid Crystal Display Device) Twist Angle: 240 °, Δnd
Below the 880 nm STN liquid crystal cell, one optical compensatory sheet Y produced in Comparative Example 2, the optically anisotropic layer side is the liquid crystal cell side, and the optical compensatory sheet and the liquid crystal cell are bonded together. The optical compensation sheet was attached to the liquid crystal cell so that the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal cell of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. The contrast ratio of the manufactured STN-type liquid crystal display device was measured using a measuring device (EZ-Contrast 160D, manufactured by ELDIM). The results are shown in Table 1.

[0108]

[Table 1] Table 1 装置 Equipment Sheet Sheet arrangement Cellulose ester Addition amount Contrast ratio ──────────────────────────────────── Actual 7 A Lower 2 sheets 0.034 g / m ² 18 Actual 8 A Lower 1 + Upper 1 0.034 g / m ² 18 Actual 9 B Lower 2 0.136 g / m ² 19 Actual 10 C Lower 2 0.034 g / m ² 19 Actual 11 D Below 1 piece 0.034 g / m ² 20 real 12 E 1 piece below 0.034 g / m ² 21 real 13 F 1 piece below 0.34 g / m ² 19 ratio 3 X 1 piece below 0.544 g / m ² 3 ratio 4 Y Bottom 1 None 5 ────────────────────────────────────

Example 14 (Preparation of Optical Compensation Sheet A1) A 100 μm-thick triacetylcellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) was used as a transparent support. A 4 wt% solution obtained by dissolving the polyimide used in Example 1 in a mixed solvent of N-methyl-2-pyrrolidone, butoxyethanol and methyl ethyl ketone was applied to a transparent support using a # 3 bar coater. Was applied. Apply layer 14
Dry at 0 ° C. for 2 minutes, heat at 62 ° C. for 5 minutes,
An alignment film was formed. The thickness of the alignment film was 0.51 μm. A coating solution having the following composition was applied on the rubbed alignment film using a # 9 bar coater.

<< Coating Liquid for Optically Anisotropic Layer >>デ ィ ス 91 parts by weight of discotic liquid crystal molecules (1) used in Example 1 1.6 parts by weight of a chiral agent used in Example 1 A cellulose acetate butyrate having a degree of acetylation of 2.0%, a degree of butyrylation of 52.0%, and a number average molecular weight of 30,000 (CAB-551-0.2, Eastman Chemie) 0.25 parts by weight Cellulose acetate butyrate having a degree of acetylation of 3.0%, a degree of butyrylation of 50.0%, and a number average molecular weight of 40,000 (CAB-531-1, manufactured by Eastman Chemical Company) 0.25 Parts by weight ethylene oxide-modified trimethylolpropane triacryle (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 7 parts by weight Photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) 3 parts by weight Sensitizer (Kaya Cure DETX, Nippon Kayaku Co., Ltd.) 1 part by weight methyl ethyl ketone 120 parts by weight ────────────────────────────────────

When the formed optically anisotropic layer was observed with a polarizing microscope while heating, no columnar phase appeared.
The nematic-isotropic transition temperature (T _NI ) of the discotic liquid crystal molecules was 149 ° C., and the crystal-nematic transition temperature (T _CN ) of the discotic liquid crystal molecules was 105 ° C. Again, the formed optically anisotropic layer was heated at 140 ° C. for 10 minutes to align the discotic liquid crystalline compound. With the coating layer heated to 140 ° C., 500 mJ / cm ² using a metal halide lamp.
Irradiation of ultraviolet rays, discotic liquid crystal molecules (1)
Was polymerized to fix the orientation state. In this manner, an optically anisotropic layer in which the discotic liquid crystal molecules were vertically (homogeneous) and twisted and oriented was formed, and an optical compensation sheet was produced. The Δnd of the obtained optical compensation sheet measured at a wavelength of 550 nm was 440 nm. Further, the twist angle of the discotic liquid crystal molecules was 120 °. Furthermore, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).

Comparative Example 5 (Preparation of Optical Compensation Sheet A2) An optical compensation sheet A2 was prepared in the same manner as in Example 14 except that the heating temperature of the optically anisotropic layer was changed to 110 ° C. When the Δnd of the obtained optical compensation sheet was measured, it was 440 nm.
The twist angle of the discotic liquid crystal molecules is 12
It was 0 °. Further, when the alignment state of the discotic liquid crystalline molecules was confirmed by a polarizing microscope, two types of alignment states (dual domain alignment) having different tilt directions were recognized, although the Δnd and the twist angle were equal.

Comparative Example 6 (Preparation of Optical Compensation Sheet A3) An optical compensation sheet A3 was prepared in the same manner as in Example 14 except that the heating temperature of the optically anisotropic layer was changed to 155 ° C. When the obtained optical compensatory sheet was examined, the discotic liquid crystal molecules were not oriented (isotropic state).

Example 15 (Preparation of Optical Compensation Sheet B1) Ethylene oxide-modified trimethylolpropane triacrylate (V # 36)
0, manufactured by Osaka Organic Chemical Co., Ltd.) except that the used amount was changed to 9 parts by weight, and an optically anisotropic layer coating solution was prepared and applied on the alignment film in the same manner as in Example 14. When the formed optically anisotropic layer was observed with a polarizing microscope while heating, no columnar phase appeared and the nematic-isotropic transition temperature (T _NI ) of the discotic liquid crystalline molecules was 1
The crystal-nematic transition temperature (T _CN ) of the discotic liquid crystalline molecule was 100 ° C. at 36 ° C. Again, the formed optically anisotropic layer was heated at 130 ° C. for 10 minutes,
The discotic liquid crystalline compound was aligned. While the coating layer was heated to 130 ° C., it was irradiated with 500 mJ / cm ² ultraviolet rays using a metal halide lamp to polymerize the terminal vinyl group of the discotic liquid crystal molecule (1) and fix the alignment state. In this manner, an optically anisotropic layer in which the discotic liquid crystal molecules were vertically (homogeneous) and twisted and oriented was formed, and an optical compensation sheet was produced. Δnd of the obtained optical compensation sheet is set to a wavelength of 550 n.
m was 440 nm. The twist angle of the discotic liquid crystalline molecules is 120.
Was ゜. Furthermore, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).

Comparative Example 7 (Preparation of Optical Compensation Sheet B2) An optical compensation sheet B2 was prepared in the same manner as in Example 15 except that the heating temperature of the optically anisotropic layer was changed to 105 ° C. When the Δnd of the obtained optical compensation sheet was measured, it was 440 nm.
The twist angle of the discotic liquid crystal molecules is 12
It was 0 °. Further, when the alignment state of the discotic liquid crystalline molecules was confirmed by a polarizing microscope, two types of alignment states (dual domain alignment) having different tilt directions were recognized, although the Δnd and the twist angle were equal.

Comparative Example 8 (Preparation of Optical Compensation Sheet B3) An optical compensation sheet B3 was prepared in the same manner as in Example 15 except that the heating temperature of the optically anisotropic layer was changed to 145 ° C. When the obtained optical compensatory sheet was examined, the discotic liquid crystal molecules were not oriented (isotropic state).

Example 16 (Preparation of Optical Compensation Sheet C1) Ethylene oxide-modified trimethylolpropane triacrylate (V # 36)
0, manufactured by Osaka Organic Chemical Co., Ltd.) was changed to 11 parts by weight to prepare an optically anisotropic layer coating solution in the same manner as in Example 14, and applied on the alignment film. When observed with a polarizing microscope while heating the formed optically anisotropic layer,
No columnar phase appeared, and the nematic-isotropic transition temperature (T _NI ) of the discotic liquid crystalline molecules was 130 ° C. and the crystal-nematic transition temperature (T _CN ) of the discotic liquid crystalline molecules was 95 ° C. Again, the formed optically anisotropic layer was heated at 120 ° C. for 10 minutes,
The discotic liquid crystalline molecules were aligned. 1 coating layer
While being heated to 20 ° C., ultraviolet rays of 500 mJ / cm ² were irradiated using a metal halide lamp to polymerize the terminal vinyl group of the discotic liquid crystal molecule (1), thereby fixing the alignment state. In this manner, an optically anisotropic layer in which the discotic liquid crystal molecules were vertically (homogeneous) and twisted and oriented was formed, and an optical compensation sheet was produced. Δnd of the obtained optical compensation sheet is set to a wavelength of 550 nm.
Was 440 nm. Also,
The twist angle of the discotic liquid crystal molecules was 120 °. Furthermore, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment).

Comparative Example 9 (Preparation of Optical Compensation Sheet C2) An optical compensation sheet C2 was prepared in the same manner as in Example 16 except that the heating temperature of the optically anisotropic layer was changed to 100 ° C. When the Δnd of the obtained optical compensation sheet was measured, it was 440 nm.
The twist angle of the discotic liquid crystal molecules is 12
It was 0 °. Further, when the alignment state of the discotic liquid crystalline molecules was confirmed by a polarizing microscope, two types of alignment states (dual domain alignment) having different tilt directions were recognized, although the Δnd and the twist angle were equal.

Comparative Example 10 (Preparation of Optical Compensation Sheet C3) An optical compensation sheet C3 was prepared in the same manner as in Example 16 except that the heating temperature of the optically anisotropic layer was changed to 140 ° C. When the obtained optical compensatory sheet was examined, the discotic liquid crystal molecules were not oriented (isotropic state).

[Examples 17 to 19 and Comparative Examples 11 to 1]
3] (Production of liquid crystal display device) Twist angle is 240 °, Δnd
Below the 880 nm STN liquid crystal cell, Example 14,
15, 16 and two optical compensatory sheets prepared in Comparative Examples 5, 7 and 9 with the optically anisotropic layer side facing each other, the director of the discotic liquid crystalline molecules of the optically anisotropic layer (the discotic liquid crystal). Normal direction of the disk surface of the conductive molecule)
Were bonded so that they matched. The optical compensation sheet was attached to the liquid crystal cell such that the discotic liquid crystal molecules and the director of the rod-like liquid crystal molecules of the liquid crystal cell coincided on the surface where the optical compensation sheet and the liquid crystal cell were bonded. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. ST created
For an N-type liquid crystal display device, use a measuring device (EZ-Contrast1).
60D, manufactured by ELDIM). The results are shown in Table 2.

[0121]

[Table 2] Table 2 装置 Equipment sheet T _NI T _CN orientation Processing temperature (T) Contrast ratio ──────────────────────────────────── Actual 17 A1 149 ° C 105 ° C 140 ° C 20 Ratio 11 A2 149 ° C 105 ° C 110 ° C 4 Actual 18 B1 136 ° C 100 ° C 130 ° C 21 Ratio 12 B2 136 ° C 100 ° C 105 ° C 3 Actual 19 C1 130 ° C 95 ° C 120 ° C 19 Ratio 13 C2 130 ° C 95 ° C 100 ℃ 3────────────────────────────────────

Example 20 (Preparation of Optical Compensation Sheet) A 100 μm-thick triacetyl cellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) was used as a transparent support. A 4 wt% solution obtained by dissolving the polyimide used in Example 1 in a mixed solvent of N-methyl-2-pyrrolidone, butoxyethanol and methyl ethyl ketone was applied to a transparent support using a # 3 bar coater. Was applied. 140 ° C
For 2 minutes, and further heated at 62 ° C. for 5 minutes to form an alignment film. The thickness of the alignment film was 0.51 μm.

A coating solution having the following composition was applied to the rubbed alignment film using a # 11 bar coater, and heated to 130 ° C. to align discotic liquid crystal molecules.

<< Coating Liquid for Optically Anisotropic Layer >> ───────────────────────────────── 100 weight parts of the following discotic liquid crystalline molecules (2) Chiral agent used 1.8 parts by weight Liquid crystal alignment accelerator (I-1) 5.0 parts by weight Photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) 0.2 parts by weight 2-butanone 185 parts by weight ───────────────────────────────────

[0125]

Embedded image

[0126]

Embedded image

While the coating layer was heated to 130 ° C., it was irradiated with ultraviolet rays of 500 mJ / cm ² using a metal halide lamp to polymerize the terminal vinyl groups of the discotic liquid crystal molecules and fix the alignment state. Thus, an optical compensation sheet was produced. When the retardation and the film thickness of the optical compensation sheet were measured using an ellipsometer, the retardation per 6.2 μm thickness was 440.
nm. In addition, when the alignment state of the discotic liquid crystal molecules was checked with a polarizing microscope, all the molecules were uniformly aligned (monodomain alignment), and no alignment defect was observed. When the above experiment was further repeated twice, the retardation per 6.2 μm was slightly changed (the second time was 444 nm, and the third time was 436 nm).
m), but no alignment defect was observed in any of the alignment states of the discotic liquid crystal molecules.

Comparative Example 14 Liquid Crystal Alignment Accelerator (I-1)
An optical compensatory sheet was produced in the same manner as in Example 20, except that was not added. When the retardation and the film thickness of the optical compensation sheet were measured using an ellipsometer, the retardation per 6.2 μm thickness was 378 nm. In addition, when the alignment state of the discotic liquid crystal molecules was confirmed with a polarizing microscope, it was confirmed that countless fine alignment defects having a sea-island pattern existed. When the above experiment was repeated twice more, the retardation per 6.2 μm thickness varied (368 nm in the second time, 390 nm in the third time), and the alignment state of the discotic liquid crystal molecules was It was confirmed that countless fine orientation defects having a sea-island pattern existed.

[Example 21] (Production of liquid crystal display device) Twist angle was 240 °, Δnd
Below the 880 nm STN liquid crystal cell, two optically compensatory sheets prepared in Example 20 with the optically anisotropic layer side facing each other, and the director of discotic liquid crystalline molecules of the optically anisotropic layer ( The discotic liquid crystal molecules were bonded so that their discotic liquid crystal molecules had the same normal direction. On the surface where the optical compensation sheet and the liquid crystal cell are bonded,
The optical compensation sheet was attached to the liquid crystal cell such that the director of the discotic liquid crystal molecules and the director of the rod-shaped liquid crystal molecules of the liquid crystal cell matched. Further, a pair of polarizing plates were attached in a crossed Nicol arrangement to produce an STN liquid crystal display device. When the manufactured STN liquid crystal display device was compared with the STN liquid crystal display device without the optical compensation sheet, a remarkable effect of improving the viewing angle by the optical compensation sheet was recognized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of discotic liquid crystalline molecules oriented substantially vertically (dual domain or mono domain).

FIG. 2 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. 3 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 relationship of optically compensating the same.

FIG. 4 is a schematic diagram showing a layer configuration of an STN liquid crystal display device.

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

FIG. 6 is a plan view showing another preferred optical direction for each element of the STN 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

 ──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 2000-24450 (P2000-24450) (32) Priority date February 1, 2000 (2000.2.1) (33) Priority claim country Japan (JP) (72) Inventor Shigeki Yokoyama 210 Nakanakanuma, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Photo Film Co., Ltd. (72) Inventor Mitsuyoshi Ichihashi 200 Onakazato, Fujinomiya City, Shizuoka Prefecture Fuji Photo Film Co., Ltd. F-term (reference) 2H049 BA06 BA42 BB49 BC02 BC05 BC22 2H091 FA11X FA11Z FB02 FB12 FD06 GA06 HA10 LA19 LA20 4H027 BA08 BA11 BB04 BD07 CH02 CH03 DG02 DG03 DJ02

Claims (9)

[Claims] 1. An optical compensation sheet having a transparent support and an optically anisotropic layer formed from discotic liquid crystal molecules, wherein the discotic liquid crystal molecules have an average tilt angle in the range of 50 to 90 degrees. An optical compensation sheet characterized by being substantially monodomain oriented. 2. The optical compensatory sheet according to claim 1, wherein the discotic liquid crystal molecules are twist-aligned, and the twist angle is in a range of 90 to 360 degrees. 3. The optically anisotropic layer has a thickness of 0.005 to 0.5.
The optical compensation sheet according to claim 1 comprising a cellulose ester in an amount ranging from g / m ^2. 4. The optical compensation sheet according to claim 3, wherein the cellulose ester is a lower fatty acid ester of cellulose. 5. The optically anisotropic layer has a thickness of 0.005 to 0.5.
The optical compensation sheet of claim 1 comprising alignment promoter in an amount ranging from g / m ² is represented by the following formula (I). (I) (Hb-) in _m L (-Bu) _n [Formula, Hb consists fluorine-substituted alkyl group, fluorine-substituted aryl group, the alkyl group and alkyl-substituted oligosiloxanoxy group having 6 or more carbon atoms A hydrophobic group selected from the group; Bu is a group having an excluded volume effect containing at least two cyclic structures; L is (m +
n) a valent linking group; and m and n are each independently an integer from 1 to 12]. 6. In the formula (I), m and n are each 1 and L is an alkylene group —, —O—, —C
O -, - NR -, - SO 2 - and a divalent linking group selected from the group consisting of optical compensation sheet according to claim 5 R is a hydrogen atom or an alkyl group. 7. The optical compensation sheet according to claim 5, wherein in the formula (I), the group having an excluded volume effect of Bu contains a tricyclic or tetracyclic fused ring. 8. The optical compensation sheet according to claim 5, wherein in the formula (I), the group having an excluded volume effect of Bu has a structure in which at least two rings are bonded by a single bond, a vinylene bond or an ethynylene bond. . 9. 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. Wherein the optical compensation sheet has a transparent support and an optically anisotropic layer formed from discotic liquid crystal molecules in this order from the polarizing plate side, and the discotic liquid crystal molecules have a thickness of 50%. To 90
Substantially mono-domain oriented at an average tilt angle in the range of degrees,
Furthermore, it has a twisted orientation and a twist angle of 90 to 360.
An STN liquid crystal display device having a range of degrees.