JP2005157330A - Optical compensation sheet and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems relating to the ability of displaying a moving image (in particular, response time) of a liquid crystal display under a low-temperature environment. <P>SOLUTION: In an optical compensatory sheet having a cellulose acylate film or an optically anisotropic layer formed from a liquid crystal compound, the in-plane retardation value measured at 20°C and 20% relative humidity is in the range of 97 to 103%, based on the in-plane retardation value measured at 10°C and 20% relative humidity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical compensation sheet having an optically anisotropic layer formed from a cellulose acylate film or a liquid crystal compound, and a liquid crystal display device using the same.

  In recent years, an optical film in which the orientation of a liquid crystal compound is fixed has been developed in various applications such as an optical compensation sheet for a liquid crystal display device, a brightness enhancement film, and an optical compensation sheet for a projection display device. The development of the liquid crystal display device as an optical compensation sheet is particularly remarkable.

  The liquid crystal display device includes a polarizing plate and a liquid crystal cell. In the current mainstream TN mode TFT liquid crystal display device, an optical compensation sheet is inserted between the polarizing plate and the liquid crystal cell to display a high-quality image. However, when the optical compensation sheet is inserted, the device becomes thick, and the advantages of the thin liquid crystal display device cannot be fully exhibited.

In general, a polarizing film has a polarizing film disposed between two protective films. It has been proposed to increase the front contrast without increasing the thickness of the liquid crystal display device by using a polarizing plate (elliptical polarizing plate) in which one protective film is replaced with an optical compensation sheet (for example, Patent Document 1). reference). However, with the optical compensation sheet incorporated in the elliptically polarizing plate, a sufficient viewing angle improvement effect cannot be obtained, and the display quality of the liquid crystal display device sometimes deteriorates.
When using a polarizing plate (elliptical polarizing plate) in which one protective film of the polarizing plate is replaced with an optical compensation sheet having an optically anisotropic layer and a transparent support formed from a liquid crystal compound (for example, a discotic liquid crystal compound), It has been reported that problems related to viewing angle can be solved without increasing the thickness of the display device (see, for example, Patent Documents 2 and 3).

Recently, the demand for TN mode liquid crystal display devices has been increasing. In television applications, the display of moving images is a particular problem. Problems relating to response speed, for example, a tailing phenomenon, have been pointed out for moving images displayed by a TN mode liquid crystal display device.
Instead of a TN mode liquid crystal display device, an OCB type liquid crystal display device is used, and an optical compensation sheet having an optically anisotropic layer formed from a liquid crystal compound and a transparent support is incorporated into the liquid crystal display device, thereby supporting moving images. It has been proposed to realize response speed and solve the problem of viewing angle (see, for example, Patent Documents 4 and 5). However, LCD TVs are often mounted in cars or used outdoors because of their portability, and they always maintain high display quality in harsh conditions such as high temperature, low temperature, high humidity, or low humidity. It is requested.

  In order to cope with changes in cell retardation at high temperatures, it has been proposed to achieve high display quality at high temperatures by following the retardation of an optically anisotropic film (optical compensation sheet) ( For example, see Patent Document 6). However, no improvement means has been proposed for the OCB type liquid crystal display device having a display quality at a low temperature and a high response speed even at a low temperature.

JP-A-01-68940 Japanese Patent Laid-Open No. 07-191217 European Patent Application No. 0911656 Japanese Unexamined Patent Publication No. 09-212444 JP 11-316378 A Japanese Patent Laid-Open No. 08-278406

An object of the present invention is to solve the problem relating to the suitability of moving images (particularly response speed) of a liquid crystal display device in a low temperature environment.
Another object of the present invention is to solve various problems when the liquid crystal display device is applied to a portable television without increasing the thickness of the liquid crystal display device.
Furthermore, an object of the present invention is to provide an optical compensation sheet that is suitable for an OCB type liquid crystal display device and can improve the quality of the displayed image.

The present invention provides the following optical compensation sheets (1) to (6) and the following liquid crystal display devices (7) to (10).
(1) It consists of a cellulose acylate film, and the in-plane retardation value measured at a temperature of 20 ° C. and a relative humidity of 20% is 97 to 103% of the in-plane retardation value measured at a temperature of 10 ° C. and a relative humidity of 20%. An optical compensation sheet characterized by being in the range.
(2) An in-plane retardation value measured at a temperature of 10 ° C. and a relative humidity of 20%, having an in-plane retardation value measured at a temperature of 20 ° C. and a relative humidity of 20%, comprising an optically anisotropic layer formed from a liquid crystal compound and a transparent support. An optical compensation sheet characterized by being in a range of 97 to 103% of a retardation value.
(3) The optical compensation sheet according to (2), wherein the transparent support is made of a cellulose acylate film.
(4) The in-plane retardation value measured at a temperature of 20 ° C. and a relative humidity of 20% of the cellulose acylate film is within the range of 97 to 103% of the in-plane retardation value measured at a temperature of 10 ° C. and a relative humidity of 20%. The optical compensation sheet according to (3).
(5) The cellulose acylate film contains 4 to 15% by mass of a hydrophobic compound having a molecular weight of 200 to 700 and an oxygen atom number of 2 or less, based on the cellulose acylate (1) or (4) Optical compensation sheet.
(6) The optical compensation sheet according to (5), wherein the hydrophobic compound has 1 or less oxygen atoms.

(7) A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, and any one of (1) to (6) between the liquid crystal cell and at least one polarizing plate. A liquid crystal display device comprising the optical compensation sheet according to claim 1.
(8) A liquid crystal display device comprising a reflector, a liquid crystal cell, and a polarizing plate, wherein the optical compensation sheet according to any one of (1) to (6) is provided between the liquid crystal cell and the reflector. A liquid crystal display device characterized by the above.
(9) The liquid crystal display device according to (7) or (8), wherein the response time is 300 ms or less.
(10) The liquid crystal display device according to (7), which is an OCB method.

The in-plane retardation value (Re) is a value defined by the following formula.
Re = (nx−ny) × d
In the formula, nx is the refractive index in the slow axis direction (direction in which the refractive index is maximum) in the plane, and ny is the refractive index in the fast axis direction (direction in which the refractive index is minimum) in the plane. , Nz is the refractive index in the thickness direction, and d is the thickness (nm).
Unless otherwise defined in this specification, the wavelength of light for measuring the in-plane retardation value is 590 nm.
The slow axis of the optically anisotropic layer usually coincides with or is orthogonal to the average direction of orthogonal projection of the molecular symmetry axis of the liquid crystal compound onto the support surface.
The response time of the liquid crystal display device is measured under conditions of a temperature of 20 ° C. and a relative humidity of 20%. Even when measurement is performed under conditions of a temperature of 10 ° C. and a relative humidity of 20%, it is more preferable that the response time is 300 ms or less.

  As a result of the study by the present inventor, it has been found that the retardation value of the liquid crystal cell is significantly less temperature dependent at low temperatures. Therefore, it is preferable that the retardation change of the optical compensation sheet is small at low temperatures. The optical compensation sheet is an optical element used for adjusting a display hue in a liquid crystal display device that performs color expression using a phase difference in addition to a sheet that cancels the phase difference of the liquid crystal cell (optically compensates the liquid crystal cell). Includes anisotropic sheets.

The optical compensation sheet of the present invention has an optically anisotropic layer formed from a cellulose acylate film or a liquid crystal compound. In both the cellulose acylate film and the optically anisotropic layer, the influence of water is large as a factor causing the temperature dependence of retardation at low temperatures. When moisture is present in the cellulose acylate film or the optically anisotropic layer, the retardation of the molecular structure derived from the cellulose acylate that constitutes the film or the liquid crystal compound that constitutes the optically anisotropic layer is disturbed. cause. In general, at low temperatures, the amount of water in the film or layer decreases and the retardation increases.
According to the present invention, by suppressing the retardation change of the optical compensation sheet, the suitability of moving images (particularly the response speed) of the liquid crystal display device in a low temperature environment can be improved.

[Basic configuration of liquid crystal display]
FIG. 1 is a schematic diagram of an OCB type liquid crystal display device.
The liquid crystal display device shown in FIG. 1 includes a backlight device (1), a backlight side polarizing plate (2), a bend alignment mode liquid crystal cell (3), and a viewing side polarizing plate (4).
The backlight device (1) includes a backlight light source (11) and a light guide plate (12). A diffusing plate or a brightness enhancement film may be disposed between the backlight device (1) and the backlight side polarizing plate (2).
The backlight side polarizing plate (2) is composed of a second transparent protective film (21), a polarizing film (22), a first transparent protective film (23) made of cellulose acylate film, an alignment film (24), and a liquid crystalline compound. The formed optically anisotropic layer (25) is provided in this order. The first transparent protective film (23) may have optical anisotropy. The arrow written in the alignment film (24) is the rubbing direction. In the optically anisotropic layer (25), the discotic liquid crystalline compound (251) is hybrid-aligned so that the tilt angle is small on the side close to the alignment film (24) and the tilt angle is large on the far side.

  The optical compensation sheet according to the present invention is a first transparent protective film (23) made of a cellulose acylate film, or an optically anisotropic layer formed from a first transparent protective film (23), an alignment film (24), and a liquid crystalline compound. It can be used as a laminate of (25).

  The liquid crystal cell (3) in the bend alignment mode includes a lower glass substrate (31), a lower transparent conductive film (32), a lower alignment film (33), a liquid crystal layer (34), an upper alignment film (35), and an upper A transparent conductive film (36), a color filter (37), and an upper glass substrate (38) are provided in this order. The arrow written in the alignment films (33, 35) is the rubbing direction. In the liquid crystal layer (34), the rod-like liquid crystal molecules (341) are bend-oriented symmetrically between the upper part and the lower part. The color filter (37) includes a blue region (371), a green region (372), a red region (373), and a black matrix (374) for dividing them.

  The viewing-side polarizing plate (4) includes an optically anisotropic layer (41) formed from a liquid crystalline compound, an alignment film (42), a first transparent protective film (43) made of a cellulose acylate film, a polarizing film (44), It has a 2nd transparent protective film (45) and a light-diffusion layer (46) in this order. In the optically anisotropic layer (41), the discotic liquid crystalline compound (411) is hybrid-aligned so that the tilt angle is small on the side close to the alignment film (42) and the tilt angle is large on the far side. The arrow written on the alignment film (42) is the rubbing direction. The first transparent protective film (43) has optical anisotropy. The second transparent protective film (45) may be optically isotropic.

  The optical compensation sheet according to the present invention is a first transparent protective film (43) made of a cellulose acylate film, or an optical anisotropic layer formed from a first transparent protective film (43), an alignment film (42) and a liquid crystalline compound. It can be used as a laminate of (41).

  The light diffusion layer (46) contains the first light-transmitting fine particles (461) and the second light-transmitting fine particles (462) in the light-transmitting resin. The two types of translucent fine particles preferably have different refractive indexes and different particle sizes (having two particle size distribution peaks as a whole). However, they may be the same type (having the same refractive index) and only the particle size may be different. Two types of fine particles having almost the same particle size (the peak of particle size distribution is not separated) but having different refractive indexes may be used. One kind of translucent fine particles can also be used. A low refractive index layer may be provided on the light diffusion layer (46).

[Optical characteristics of optical compensation sheet]
In the optical compensation sheet of the present invention, the in-plane retardation value measured at a temperature of 20 ° C. and a relative humidity of 20% is 97 to 103% of the in-plane retardation value measured at a temperature of 10 ° C. and a relative humidity of 20% (preferably 98 to 102%). In other words, in the present invention, an in-plane retardation value (Re20) measured at a temperature of 20 ° C. and a relative humidity of 20% and an in-plane retardation value (Re10) measured at a temperature of 10 ° C. and a relative humidity of 20% are obtained. The following formula is satisfied.
0.97 × Re10 ≦ Re20 ≦ 1.03 × Re10

[Cellulose acylate film (transparent support)]
The optical compensation sheet according to the present invention has a cellulose acylate film or a transparent support.
Specifically, that the support is transparent means that the light transmittance is 80% or more. The transparent support is preferably made of a polymer film. Examples of the polymer include cellulose esters (eg, cellulose acetate, cellulose diacetate), norbornene-based polymers, and poly (meth) acrylic acid esters (eg, polymethyl methacrylate). Commercially available polymers (Arton and Zeonex for norbornene polymer products) may be used.
Use a polymer that easily exhibits birefringence, such as polycarbonate or polysulfone, as a transparent support having low birefringence by controlling the expression of birefringence by molecular modification (see, for example, International Publication No. 00/26705 pamphlet). You can also.

The polymer is preferably a cellulose ester, and more preferably cellulose acylate.
Therefore, the optical compensation sheet according to the present invention preferably has at least one cellulose acylate film as a component.
The cellulose acylate is preferably a lower fatty acid ester of cellulose. Lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate can also be used. Cellulose acetate is particularly preferred.

When the optical compensation sheet is used as a protective film or retardation film for a polarizing plate, the acetylation degree of cellulose acetate is preferably 55.0 to 62.5%, and 57.0 to 62.0%. More preferably. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is determined according to the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).
The viscosity average degree of polymerization (DP) of cellulose acetate is preferably 250 or more, and more preferably 290 or more. Cellulose acetate preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 4.0, more preferably 1.0 to 1.65, and most preferably 1.0 to 1.6. .

In cellulose acetate, the hydroxyl groups at the 2-position, 3-position and 6-position of cellulose are not evenly substituted but the degree of substitution at the 6-position tends to be small. In the polymer film used as the support, it is preferable that the degree of substitution at the 6-position of cellulose is the same or greater than that at the 2- and 3-positions. The ratio of the substitution degree at the 6-position to the total substitution degree at the 2-position, the 3-position and the 6-position is preferably 30 to 40%, more preferably 31 to 40%, and more preferably 32 to 40%. Most preferred. The substitution degree at the 6-position is preferably 0.88 or more. The degree of substitution at each position can be measured by NMR.
Cellulose acetate having a high degree of substitution at the 6-position is described in Synthesis Example 1 described in Paragraph Nos. 0043 to 0044, Synthesis Example 2 described in Paragraph Nos. 0048 to 0049, and Paragraph Nos. 0051 to 0052. It can be synthesized with reference to the method of Synthesis Example 3.

The in-plane retardation value of the transparent support is preferably 0 to 200 nm, more preferably 20 to 150 nm, and most preferably 30 to 100 nm. The retardation value in the thickness direction of the transparent support is preferably 40 to 400 nm. When two optical compensation sheets are incorporated into the liquid crystal display device, the retardation value in the thickness direction is more preferably 40 to 250 nm. When two optical compensation sheets are incorporated in the liquid crystal display device, the retardation value in the thickness direction is more preferably 150 to 400 nm.
The in-plane retardation value (Re) and the thickness direction retardation value (Rth) are values defined by the following formulae.
Re = (nx−ny) × d
Rth = {(nx + ny) / 2−nz} × d
In the formula, nx is the refractive index in the slow axis direction (direction in which the refractive index is maximum) in the plane, and ny is the refractive index in the fast axis direction (direction in which the refractive index is minimum) in the plane. , Nz is the refractive index in the thickness direction, and d is the thickness (nm).
In addition, cellulose acylate having an acyl group having 2 to 4 carbon atoms as a substituent is also preferably used. The cellulose acylate having an acyl group having 2 to 4 carbon atoms as a substituent is described in JP-A Nos. 2002-210766 and 2002-187958.

  The in-plane birefringence (Δn: nx−ny) of the transparent support is preferably 0.00025 to 0.00088. The birefringence {(nx + ny) / 2−nz} in the thickness direction of the transparent support is preferably 0.00088 to 0.005.

In order to suppress the fluctuation of the in-plane retardation value (Re) of the cellulose acylate film (specifically, the fluctuation caused by the change in water content at low temperature), the molecular weight of the cellulose acylate film is 200 to 700. It is preferable to add 4 to 15% by mass of the hydrophobic compound having 2 or less oxygen atoms with respect to the cellulose acylate. The number of oxygen atoms in the hydrophobic compound is more preferably 1 or less. The addition amount of the hydrophobic compound is preferably 4 to 10% by mass, and more preferably 4 to 7% by mass.
Among the additives of cellulose acylate film, a retardation increasing agent is known as a hydrophobic compound satisfying the above definition. The retardation increasing agent is a compound having a function of increasing the retardation value (Rth) in the thickness direction of the cellulose acylate film. Retardation raising agents (including hydrophilic compounds) are described in JP-A Nos. 2000-154261 and 2000-1111914.

  In the present invention, the above-described hydrophobic compound is used not for increasing the retardation value (Rth) in the thickness direction but for suppressing the fluctuation of the in-plane retardation value (Re). Because the purpose of use is different, the hydrophobic compound is used in a larger amount (4 to 15% by mass relative to the cellulose acylate) than the amount (1.5% by mass or 3% by mass) of the retardation increasing agent. There is a need to.

The hydrophobic compound preferably has a 1,3,5-triazine ring.
The hydrophobic compound having a 1,3,5-triazine ring is more preferably represented by the following formula (I). Since the hydrophobic compound represented by the following formula (I) is difficult to precipitate (bleed out) on the surface of the cellulose acylate film, it is added in a large amount in order to suppress fluctuations in the in-plane retardation value (Re). be able to.

In the formula (I), Ar ¹ , Ar ² and Ar ³ are each independently an aromatic hydrocarbon group or an aromatic heterocyclic group (eg, pyridyl). An aromatic hydrocarbon group is preferred to an aromatic heterocyclic group.
The aromatic hydrocarbon group means an aryl group or a substituted aryl group. A phenyl or substituted phenyl group is preferred. The position of the substituent of the substituted phenyl group is preferably the 3-position, 4-position or 5-position.
Examples of the substituent of the substituted aryl group include a halogen atom, cyano, nitro, alkyl group, alkenyl group, aryl group, alkoxy group, alkenyloxy group, aryloxy group, acyl group, alkyl-substituted carbamoyl group, alkenyl-substituted carbamoyl group, An aryl-substituted carbamoyl group, an alkyl-substituted sulfamoyl group, an alkenyl-substituted sulfamoyl group, an aryl-substituted sulfamoyl group, an amide group, an alkylthio group, an alkenylthio group and an arylthio group are included.

In the formula (I), X ¹ , X ² and X ³ are each independently a single bond or —NR—. R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. -NR- is preferred to single bond, and -NH- is most preferred.
Examples of the hydrophobic compound represented by the formula (I) are shown below.

[Optically anisotropic layer]
The optically anisotropic layer is formed from a liquid crystal compound. The optically anisotropic layer can be directly formed on the surface of the transparent support. An alignment film may be formed on the transparent support, and an optical anisotropic layer may be formed on the alignment film. Moreover, an optical compensation sheet can also be produced by forming an optical anisotropic layer from a liquid crystal compound on another substrate and then transferring the optical anisotropic layer to a transparent support. An adhesive layer may be provided on the transparent support to which the optical anisotropic layer is transferred.
The liquid crystal compound is preferably a rod-like liquid crystal compound or a discotic liquid crystal compound. The rod-like liquid crystal compound and the disk-like liquid crystal compound may be a polymer liquid crystal. In the formation of the optically anisotropic layer, the liquid crystal compound may not exhibit liquid crystallinity due to polymerization or crosslinking.

The rod-shaped liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are included. Further, the rod-like liquid crystal compound includes a metal complex. A liquid crystal polymer containing a molecular structure corresponding to a rod-like liquid crystal compound in a repeating unit can also be used. In other words, the rod-like liquid crystal compound may be bonded to a polymer to form a liquid crystal polymer.
For rod-like liquid crystal compounds, see Chapter 4, Chapter 7 and Chapter 11 of the Chemistry of the Quarterly Chemical Review Vol. 22 Liquid Crystal Chemistry (1994) edited by the Chemical Society of Japan, and the 142th Committee of the Japan Society for the Promotion of Science. Described in Chapter 3.

The birefringence of the rod-like liquid crystal compound is preferably 0.001 to 0.7.
The rod-like liquid crystal compound preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group.

  Discotic liquid crystal compounds are C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), including azacrown and phenylacetylene macrocycles.

The discotic liquid crystal compound generally has a structure in which side chains (eg, linear alkyl group, alkoxy group, substituted benzoyloxy group) are substituted radially with respect to the mother nucleus at the center of the molecule. The discotic liquid crystal compound is preferably a compound in which a molecule or an assembly of molecules has rotational symmetry and can impart a certain orientation.
When an optical anisotropic layer is formed from a discotic liquid crystal compound, the compound finally contained in the optical anisotropic layer no longer needs to exhibit liquid crystallinity. For example, a low-molecular discotic liquid crystal compound has a group that reacts with heat or light, and an optically anisotropic layer can be formed by polymerizing or crosslinking with heat or light to increase the molecular weight. . When the discotic liquid crystal compound has a high molecular weight, the liquid crystallinity is usually lost. A preferred discotic liquid crystal compound is described in JP-A-8-50206. The polymerization of the discotic liquid crystal compound is described in JP-A-8-27284.

In order to fix the discotic liquid crystal compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystal compound. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Accordingly, the discotic liquid crystal compound having a polymerizable group is preferably a compound represented by the following formula.
D (-LQ) n
In the formula, D is a discotic core, L is a divalent linking group, Q is a polymerizable group, and n is an integer of 4 to 12.

  An example of the disk-shaped 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).

  In the above formula, the divalent linking group (L) is a divalent group selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. The linking group is preferably. The divalent linking group (L) is a divalent combination of at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO-, -NH-, -O-, and -S-. More preferably, it is a linking group. The divalent linking group (L) is most preferably a divalent linking group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO- and -O- are combined. . The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The arylene group preferably has 6 to 10 carbon atoms.

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. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group).
L1: -AL-CO-O-AL-
L2: -AL-CO-O-AL-O-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L6: -CO-AR-O-AL-O-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-O-CO-

L11: -O-AL-
L12: -O-AL-O-
L13: -O-AL-O-CO-
L14: -O-AL-O-CO-NH-AL-
L15: -O-AL-S-AL-
L16: -O-CO-AR-O-AL-CO-
L17: -O-CO-AR-O-AL-O-CO-
L18: -O-CO-AR-O-AL-O-AL-O-CO-
L19: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
L20: -S-AL-
L21: -S-AL-O-
L22: -S-AL-O-CO-
L23: -S-AL-S-AL-
L24: -S-AR-AL-

The polymerizable group (Q) of the above formula is determined according to the type of polymerization reaction. The polymerizable group (Q) is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group.
In the above formula, n is an integer of 4 to 12. A specific number is determined according to the type of the disk-shaped core (D). In addition, although the combination of several L and Q may differ, it is preferable that it is the same.

Regarding the orientation of the liquid crystal compound, the average direction of the molecular symmetry axis of the optically anisotropic layer is preferably 43 ° to 47 ° with respect to the longitudinal direction.
In the hybrid alignment, the angle between the molecular symmetry axis of the liquid crystal compound and the surface of the support increases or decreases in the depth direction of the optical anisotropic layer and with an increase in the distance from the surface of the support. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction.
If the angle increases or decreases as a whole, the angle may include a region where the angle does not change. The angle preferably varies continuously.

The average direction of the molecular symmetry axis of the liquid crystal compound can be generally adjusted by selecting a liquid crystal compound or an alignment film material or by selecting a rubbing treatment method. In the case of an optical compensation sheet in which the slow axis of the transparent support and the slow axis of the optically anisotropic layer are not orthogonal or parallel to each other, rubbing treatment is performed in a direction different from the slow axis of the transparent support, thereby optically anisotropic. The slow axis direction of the layer can be adjusted.
In general, the molecular symmetry axis direction of the liquid crystal compound on the surface side (air side) of the optically anisotropic layer can be adjusted by selecting the type of the liquid crystal compound or the additive used in combination with the liquid crystal compound. Examples of the additive used in combination with the liquid crystal compound include a plasticizer, a surfactant, a polymerizable monomer, and a polymer. Similarly, the degree of change in the orientation direction of the molecular symmetry axis can be adjusted by selecting the liquid crystal compound and the additive. Regarding the surfactant, it is desirable to adjust the relationship with the surface tension control function of the coating solution.

  The plasticizer, surfactant, and polymerizable monomer used together with the liquid crystal compound are preferably compatible with the discotic liquid crystal compound and can change the tilt angle of the liquid crystal compound or do not inhibit the alignment. A polymerizable monomer (eg, a compound having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) is preferred. The addition amount of the compound is preferably in the range of 1 to 50% by mass, more preferably in the range of 5 to 30% by mass with respect to the liquid crystal compound. In addition, when a monomer having 4 or more polymerizable functional groups is mixed and used, the adhesion between the alignment film and the optically anisotropic layer can be improved.

  In order to suppress the retardation change of the optical compensation sheet (specifically, the water content change at a low temperature), a liquid crystal compound or a compound having a large number of polymerizable functional groups is used as a polymerizable monomer. It is preferable to cross-link the three-dimensional layer.

When a discotic liquid crystal compound is used as the liquid crystal compound, it is preferable to add a polymer having a certain degree of compatibility with the discotic liquid crystal compound and capable of changing the tilt angle of the discotic liquid crystal compound to the optical anisotropic layer.
The polymer is preferably cellulose ester or cellulose ether, and more preferably cellulose ester. Examples of cellulose esters include cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Examples of cellulose ethers include hydroxypropyl cellulose. The addition amount of the polymer is adjusted so as not to disturb the alignment of the discotic liquid crystal compound. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, more preferably in the range of 0.1 to 8% by mass, and most preferably in the range of 0.1 to 5% by mass with respect to the discotic liquid crystal compound. .

The discotic nematic liquid crystal phase-solid phase transition temperature in the discotic liquid crystal compound is preferably 70 to 300 ° C, and more preferably 70 to 170 ° C.
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and still more preferably 1 to 10 μm.

[Alignment film]
It is preferable to provide an alignment film between the transparent support and the optically anisotropic layer.
The alignment film is preferably a layer made of a crosslinked polymer. Crosslinkable polymers can be used. For example, a polymer having a crosslinkable functional group can be crosslinked by reacting between the polymers by light, heat, or PH change. Moreover, you may bridge | crosslink a polymer using a crosslinking agent. By using a crosslinking agent that is a compound having high reaction activity, a bonding group derived from the crosslinking agent is introduced between the polymers to crosslink between the polymers.

The alignment film made of a crosslinked polymer is usually subjected to a treatment such as light, heat or pH adjustment after a coating liquid containing a crosslinkable polymer or a mixture of a polymer and a crosslinking agent is applied on a transparent support. It can be formed by performing.
In the rubbing step, it is preferable to increase the degree of crosslinking in order to suppress dust generation in the alignment film. A value (1- (Ma / Mb) obtained by subtracting 1 from the ratio (Ma / Mb) of the amount (Ma) of the crosslinking agent remaining after crosslinking to the amount (Mb) of the crosslinking agent added to the coating solution. )) Is defined as the degree of crosslinking, the degree of crosslinking is preferably 50% to 100%, more preferably 65% to 100%, and most preferably 75% to 100%.

Examples of the polymer used for the alignment film are polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, polystyrene, polymaleimide, polyvinyl alcohol, modified polyvinyl alcohol, poly (N-methylolacrylamide), polyvinyltoluene, chlorosulfonated polyethylene. , Nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, polyvinyl acetate, polyethylene, carboxymethylcellulose, gelatin, polypropylene, polycarbonate and copolymers thereof (eg, acrylic acid / methacrylic acid copolymer, styrene / maleimide) Copolymer, styrene / vinyl toluene copolymer, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer). Silane coupling agents can also be used as the polymer. The polymer is preferably water soluble.
Poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred.

The saponification degree of polyvinyl alcohol and modified polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%, and still more preferably 85 to 95%. The polymerization degree of polyvinyl alcohol and modified polyvinyl alcohol is preferably 100 to 3000.
The introduction of the modifying group in the modified polyvinyl alcohol may be any of copolymerization modification, chain transfer modification, and block polymerization modification. Examples of the modifying group to be introduced in _{copolymerization, -COONa, -Si (OX) 3} (X is a hydrogen atom or an alkyl _{group), - N (CH 3)} 3 · Cl, -C 9 H 19, -COO, containing _{-SO 3 Na, -C 12 H 25} . Examples of the modifying group to be introduced in the chain transfer include -COONa, _-SH, a _-C 12 _{H 25.} Examples of the modifying group introduced in the block polymerization include —COOH, —CONH ₂ , —COOR (R is an alkyl group), and —C ₆ H ₅ . An alkylthio group is also a preferred modifying group.
The modified polyvinyl alcohol is described in JP-A-8-338913.

When a hydrophilic polymer such as polyvinyl alcohol is used for the alignment film, it is preferable to control the water content from the viewpoint of the degree of hardening. The moisture content is preferably 0.4 to 2.5%, more preferably 0.6 to 1.6%. The water content can be measured with a commercially available Karl Fischer moisture content measuring device.
The alignment film preferably has a thickness of 10 μm or less.

[Manufacture of optical compensation sheet]
The optical compensation sheet is generally manufactured in a roll shape. The roll-shaped optical compensation sheet is preferably produced by continuously performing the following steps (1) to (4).
(1) A step of rubbing a surface of a long transparent support conveyed in the longitudinal direction or a surface of an alignment film formed on the transparent support with a rubbing roller;
(2) The process of apply | coating the coating liquid containing a liquid crystal compound to the said rubbing process surface;
(3) a step of orienting the liquid crystal compound at a temperature equal to or higher than a liquid crystal transition temperature and fixing the orientation to form an optically anisotropic layer simultaneously with or after drying the applied coating solution; 4) A step of winding the long laminate on which the optically anisotropic layer is formed.

While aligning the liquid crystal compound at a temperature equal to or higher than the liquid crystal transition temperature in the step (3), it is preferable that the film surface wind speed on the surface of the liquid crystal compound blown in a direction other than the direction subjected to the rubbing treatment satisfies the following formula. Most preferably, V is 0 to 2.5 × 10 ⁻³ × η.
0 <V <5.0 × 10 ⁻³ × η
In the formula, V is the film surface wind speed (m / sec) on the surface of the liquid crystal compound, and η is the viscosity (cp) of the optically anisotropic layer at the alignment temperature of the liquid crystal compound.

According to the steps (1) to (4), the average direction of the orthogonal projection of the molecular symmetry axis of the liquid crystal compound onto the transparent support surface (the average direction of the molecular symmetry axis of the optically anisotropic layer) and the surface of the transparent support Unlike the inner slow axis (longitudinal direction of the transparent support), the angle between the average direction of the molecular symmetry axis and the rubbing direction is -2 ° to 2 °, preferably -1 ° to 1 °, substantially An optical compensation sheet at 0 ° can be produced continuously and stably. That is, the manufacturing method including the steps (1) to (4) is suitable for mass production.
When the optical compensation sheet is applied to the OCB mode liquid crystal display device, the angle between the average direction of the molecular symmetry axis and the in-plane slow axis of the transparent support (longitudinal direction of the transparent support) is substantially 45 °. It is preferable that

In the step (2), a polymerizable liquid crystal compound having a crosslinkable functional group is used as the liquid crystal compound. In the step (3), the coating layer is continuously irradiated with light to cure the polymerizable liquid crystal compound by polymerization. It can fix to an orientation state and can implement the process of (4) continuously after that.
In the step (1), rubbing can be performed with a rubbing roller while removing the surface of the transparent support or the alignment film.
Before the step (2), a step of removing dust from the surface of the rubbed transparent support or the alignment film may be performed.
Before the step (4), an inspection step for inspecting the optical anisotropic layer formed by continuously measuring the optical characteristics may be performed.
Each process of (1)-(4) is described in Unexamined-Japanese-Patent No. 9-73081.

  The diameter of the rubbing roller used in the step (1) is preferably from 100 mm to 500 mm, more preferably from 200 mm to 400 mm, from the viewpoints of handling suitability and fabric life. The width of the rubbing roller needs to be wider than the width of the film to be conveyed, and is preferably not less than film width × √2. The number of rotations of the rubbing roller is preferably set low from the viewpoint of dust generation, and is preferably 100 rpm to 1000 rpm, more preferably 250 rpm to 850 rpm, depending on the orientation of the liquid crystal compound.

  In order to maintain the orientation of the liquid crystal compound even when the number of rotations of the rubbing roll is lowered, it is preferable to heat the transparent support or the alignment film during rubbing. The heating temperature is the film surface temperature of the transparent support or the alignment film, and is preferably in the range of (glass transition temperature of the material −50 ° C.) to (glass transition temperature of the material + 50 ° C.). When an alignment film made of polyvinyl alcohol is used, it is preferable to control the environmental humidity of rubbing. The relative humidity at 25 ° C. is preferably 25 to 70%, more preferably 30 to 60%, and most preferably 35 to 55%.

  The conveyance speed of the transparent support is preferably 10 m / min to 100 m / min, more preferably 15 m / min to 80 m / min, from the viewpoint of productivity and the orientation of liquid crystal. Various apparatuses conventionally used for film conveyance can be used for conveyance. There are no particular restrictions on the transport method.

  The alignment film can be formed by applying a coating solution prepared by dissolving a material such as polyvinyl alcohol in water or an organic solvent to the surface of the transparent support and drying it. The alignment film can be manufactured before the above series of steps. An alignment film may be continuously formed on the surface of the long transparent support to be conveyed.

  In the step (2), a coating liquid containing a liquid crystal compound is applied to the rubbing surface. As a solvent for the coating solution, an organic solvent is preferable. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

In order to form a highly uniform optically anisotropic layer, the surface tension of the coating solution is preferably 25 mN / m or less, and more preferably 22 mN / m or less.
In order to achieve a low surface tension, it is preferable to add a surfactant to the coating solution for the optically anisotropic layer. The surfactant is preferably a fluorosurfactant, more preferably a surfactant made of a fluorine-containing polymer, and most preferably a surfactant made of a fluoroaliphatic group-containing polymer. The fluorine-containing polymer may be a copolymer of a repeating unit containing fluorine and another repeating unit (for example, a repeating unit derived from polyoxyalkylene (meth) acrylate).

  The mass average molecular weight of the fluorine-containing polymer is preferably 3000 to 100,000, more preferably 6000 to 80,000. The addition amount of the fluorine-containing polymer is preferably 0.005 to 8% by mass, more preferably 0.01 to 1% by mass, based on the coating composition (coating component excluding the solvent) mainly composed of the liquid crystal compound. 0.05 to 0.5% by mass is most preferable.

  Application | coating to the rubbing process surface of a coating liquid can be implemented by a well-known method (For example, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method). The coating amount can be appropriately determined based on the thickness of the optical anisotropic layer.

  In the step (3), the liquid crystal compound is aligned at a temperature equal to or higher than the liquid crystal transition temperature at the same time as or after drying the applied coating solution, and the alignment is fixed to form an optically anisotropic layer. . The liquid crystal compound has a desired orientation by heating during drying or by heating after drying. The drying temperature can be determined in consideration of the boiling point of the solvent used in the coating solution and the materials of the transparent support and the alignment film. The alignment temperature of the liquid crystal compound can be determined according to the liquid crystal phase-solid phase transition temperature of the liquid crystal compound used. When a discotic liquid crystal compound is used as the liquid crystal compound, the alignment temperature is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

The viscosity in the liquid crystal state is preferably 10 cp to 10000 cp, and more preferably 100 cp to 1000 cp. If the viscosity is too low, it is easily affected by wind during orientation, and very accurate wind speed / wind direction control is required for continuous production. On the other hand, if the viscosity is high, it is difficult to be affected by the wind, but the alignment of the liquid crystal becomes slow and the productivity is very deteriorated.
The viscosity of the liquid crystal layer can be controlled by the molecular structure of the liquid crystal compound. The viscosity can also be adjusted by using appropriate amounts of additives (particularly cellulosic polymers) and gelling agents for the optically anisotropic layer.
Heating can be carried out by blowing hot air at a predetermined temperature or by conveying in a heating chamber maintained at a predetermined temperature.

The aligned liquid crystal compound is fixed while maintaining the alignment state, and an optically anisotropic layer is formed. The liquid crystal compound can be fixed by cooling to a solid phase transition temperature or by a polymerization reaction. Fixing by a polymerization reaction is preferred. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (JP-A-60-105667 and US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970).
The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

It is preferable to use ultraviolet rays for light irradiation for proceeding and fixing the polymerization of the liquid crystal compound. The irradiation energy is ^preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, and most preferably a range of 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The light irradiation can be carried out by passing the coated transparent support coated with the coating liquid for the optically anisotropic layer through a conveyance path in which the light source is arranged at any one of the vertical and horizontal positions.

  Before shifting to the step (4), a protective layer can be provided on the optically anisotropic layer produced in the step (3). For example, a protective film prepared in advance may be continuously laminated on the surface of the optically anisotropic layer formed in a long shape.

In the step (4), the long laminate having the optically anisotropic layer is wound up. The winding may be performed, for example, by winding a support having an optically anisotropic layer that is continuously conveyed around a cylindrical core.
Since the optical compensation sheet obtained by the step (4) is in the form of a roll, it is easy to handle even when manufactured in large quantities. It can be stored and transported as it is.

[Polarizer]
A polarizing plate (elliptical polarizing plate) can be formed by laminating the optical compensation sheet and the polarizing film. The roll-shaped optical compensation sheet may be bonded to a polarizing film after being cut into a desired shape such as a rectangle. After the roll-shaped optical compensation sheet is bonded to the long polarizing film, it can be cut into a desired shape.
A polarizing plate in which an optical compensation sheet and a polarizing film are bonded has an optical compensation function in addition to a polarization function, and can be easily incorporated into a liquid crystal display device. If the optical compensation sheet is a protective film for the polarizing film, the liquid crystal display device can be made thin.

The polarizing film includes an alignment type polarizing film or a coating type polarizing film (manufactured by Optiva Inc.). The oriented polarizing film is composed of a binder and iodine or a dichroic dye. Iodine and dichroic dyes exhibit deflection performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal.
A commercially available oriented polarizing film is produced by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing the iodine or dichroic dye to penetrate into the binder. . In addition, commercially available polarizing films have iodine or dichroic dye distributed about 4 μm from the polymer surface (about 8 μm on both sides), and a thickness of at least 10 μm is necessary to obtain sufficient polarizing performance. is there. The penetrance can be controlled by the solution concentration of iodine or dichroic dye, the bath temperature and the immersion time.
The thickness of the polarizing film is preferably not more than a commercially available polarizing plate (about 30 μm), more preferably 25 μm or less, and most preferably 20 μm or less. When the thickness is 20 μm or less, the light leakage phenomenon is not observed in the 17-inch liquid crystal display device.

The binder of the polarizing film may be cross-linked. As the binder for the polarizing film, a polymer that can be crosslinked by itself may be used. Applying light, heat, or pH change to a polymer having a functional group, or a polymer obtained by introducing a functional group into the polymer, reacting the functional group to crosslink between the polymers to form a polarizing film it can. Moreover, you may introduce | transduce a crosslinked structure into a polymer with a crosslinking agent. It can be formed by cross-linking between binders by introducing a bonding group derived from the cross-linking agent between binders using a cross-linking agent which is a compound having high reaction activity.
In general, crosslinking can be performed by applying a coating solution containing a crosslinkable polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. Since it is only necessary to ensure durability at the stage of the final product, the cross-linking treatment may be performed at any stage until the final polarizing plate is obtained.

  As the binder of the polarizing film, a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Examples of polymers include polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, polystyrene, polyvinyl alcohol, modified polyvinyl alcohol, poly (N-methylol acrylamide), polyvinyl toluene, chlorosulfonated polyethylene, nitrocellulose, chlorinated polyolefin ( Eg, polyvinyl chloride), polyester, polyimide, polyvinyl acetate, polyethylene, carboxymethylcellulose, polypropylene, polycarbonate and copolymers thereof (eg, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, styrene / vinyl) Toluene copolymer, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer). A silane coupling agent may be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol and modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. .

The saponification degree of polyvinyl alcohol and modified polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%, and most preferably 95 to 100%. As for the polymerization degree of polyvinyl alcohol, 100-5000 are preferable.
Modified polyvinyl alcohol is obtained by introducing a modifying group into polyvinyl alcohol by copolymerization modification, chain transfer modification or block polymerization modification. Examples of the modifying group to be introduced in _{copolymerization, -COONa, -Si (OX) 3} (X is a hydrogen atom or an alkyl _{group), - N (CH 3)} 3 · Cl, -C 9 H 19, -COO, containing _{-SO 3 Na, -C 12 H 25} . Examples of the modifying group to be introduced in the chain transfer include -COONa, _-SH, a _-SC 12 _{H 25.} The degree of polymerization of the modified polyvinyl alcohol is preferably 100 to 3000. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127.
Unmodified polyvinyl alcohol and alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% are particularly preferable.
Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent.
When a large amount of the crosslinking agent for the binder is added, the heat and humidity resistance of the polarizing film can be improved. However, when 50 mass% or more of a crosslinking agent is added to the binder, the orientation of iodine or the dichroic dye is lowered. 0.1-20 mass% is preferable with respect to a binder, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. The binder contains some crosslinking agent that has not reacted even after the crosslinking reaction has been completed. However, the amount of the remaining crosslinking agent is preferably 1.0% by mass or less in the binder, and more preferably 0.5% by mass or less. When the crosslinking agent is contained in the binder in an amount exceeding 1.0% by mass, there may be a problem in durability. That is, when a polarizing film having a large amount of residual crosslinking agent is incorporated in a liquid crystal display device and used for a long time or left in a high-temperature and high-humidity atmosphere for a long time, the degree of polarization may decrease.

  The dichroic dye includes an azo dye, a stilbene dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, an oxazine dye, a thiazine dye, or an anthraquinone dye. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl). Examples of dichroic dyes include C.I. I. Direct Yellow 12, C.I. I. Direct Orange 39, C.I. I. Direct Orange 72, C.I. I. Direct Red 39, C.I. I. Direct Red 79, C.I. I. Direct Red 81, C.I. I. Direct Red 83, C.I. I. Direct Red 89, C.I. I. Direct Violet 48, C.I. I. Direct Blue 67, C.I. I. Direct Blue 90, C.I. I. Direct Green 59, C.I. I. Acid Red 37 is included. As for the dichroic dyes, those described in JP-A-1-161202, 1-172906, 1-172907, 1-183602, 1-248105, 1-265205, 7-261024 are used. There are descriptions in each publication.

  The dichroic dye is used as a free acid or salt (eg, alkali metal salt, ammonium salt or amine salt). By blending two or more kinds of dichroic dyes, polarizing films having various hues can be produced. A polarizing film using a compound (pigment) that exhibits a black color when the polarization axes are orthogonal to each other, or a polarizing film that is blended with various dichroic molecules to exhibit a black color, has excellent single-plate transmittance and polarization rate. .

[Production of polarizing plate]
The polarizing film extends the binder in the longitudinal direction (MD direction) of the polarizing film (stretching method). Or after rubbing, it dye | stains with an iodine and a dichroic dye (rubbing method).
In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. The stretching step may be performed in several steps. By dividing into several times, it is possible to stretch more uniformly even at high magnification. Before stretching, a slight stretching may be performed horizontally or vertically (a degree that prevents shrinkage in the width direction).

From the viewpoint of yield, it is preferable that the film is stretched with an inclination of 10 to 80 ° relative to the longitudinal direction. In that case, stretching can be carried out by performing tenter stretching in biaxial stretching in different steps. The biaxial stretching is the same as the stretching method performed in normal film formation. In biaxial stretching, stretching is performed at different speeds on the left and right, so that the thickness of the binder film before stretching needs to be different on the left and right. In casting film formation, the flow rate of the binder solution can be differentiated between the left and right sides by tapering the die.
The tilt angle is preferably stretched so as to match the angle formed between the transmission axis of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the liquid crystal display device and the vertical or horizontal direction of the liquid crystal cell. A normal inclination angle is 45 °. However, recently, transmissive, reflective, and transflective liquid crystal display devices have been developed that are not necessarily 45 °, and the stretching direction is preferably adjustable in accordance with the design of the liquid crystal display device.
As described above, a binder film that is obliquely stretched by 10 to 80 degrees with respect to the MD direction of the polarizing film is produced.

In the rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment process of the liquid crystal display device can be applied. That is, orientation is obtained by rubbing the surface of the film in a certain direction using paper, gauze, felt, rubber, nylon, or polyester fiber. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are planted on average. It is preferable to carry out using a rubbing roll in which the roundness, cylindricity, and deflection (eccentricity) of the roll itself are all 30 μm or less. The wrap angle of the film on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 ° or more.
When rubbing a long film, it is preferable to transport the film at a speed of 1 to 100 m / min with a constant tension by a transport device. The rubbing roll is preferably rotatable in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °. When used in a liquid crystal display device, the angle is preferably 40 to 50 °. 45 ° is particularly preferred.

A protective film is preferably disposed on both surfaces of the polarizing film, and a part of the roll-shaped optical compensation sheet is preferably used as the protective film on one surface. For example, a laminate in which a protective film / polarizing film / transparent support / optical anisotropic layer or a protective film / polarizing film / transparent support / alignment film / optical anisotropic layer is laminated in this order is preferable. The polarizing film and the surface side of the optical anisotropic layer may be bonded together. An adhesive can be used for bonding. Polyvinyl alcohol resins (including modified polyvinyl alcohols with acetoacetyl groups, sulfonic acid groups, carboxyl groups, and oxyalkylene groups) and boron compound aqueous solutions can be used as adhesives. A polyvinyl alcohol resin is preferred.
The thickness of the adhesive layer is preferably in the range of 0.01 to 10 μm after drying, and more preferably in the range of 0.05 to 5 μm.

  When using a polarizing plate for a liquid crystal display device, it is preferable to install an antireflection layer on the viewing side surface. The antireflection layer may also be used as a protective layer on the viewing side of the polarizing film. From the viewpoint of suppressing a change in tint depending on the viewing angle of the liquid crystal display device, the internal haze of the antireflection layer is preferably 50% or more. The antireflection layer is described in JP-A Nos. 2001-33783, 2001-343646, and 2002-328228.

  In order to increase the contrast ratio of the liquid crystal display device, the transmittance of the polarizing plate is preferably higher and the degree of polarization is preferably higher. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 50% in light having a wavelength of 550 nm. . The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% in light having a wavelength of 550 nm.

[Liquid Crystal Display]
An optical compensation sheet or a polarizing plate incorporating the optical compensation sheet is preferably used for a birefringence mode liquid crystal display device. The optical compensation sheet according to the present invention is advantageously used in a liquid crystal display device that has a fast response speed at low temperatures, particularly an OCB type liquid crystal display device.
The response time of the liquid crystal display device is preferably 10 msec or less at room temperature. At 0 ° C., 200 msec or less is preferable, and 100 msec or less is more preferable. At -20 ° C, 500 msec or less is preferable, and 300 msec or less is more preferable. The response time is the time required to shift to the next display such as black display to white display and halftone display to halftone display.

The transmissive liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates.
One optical compensation sheet is disposed between the liquid crystal cell and one polarizing plate, or two optical compensation sheets are disposed between the liquid crystal cell and both polarizing plates.

  The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell. OCB mode liquid crystal cells are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are aligned symmetrically between the upper part and the lower part of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. For this reason, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed.

[Example 1]
(Preparation of transparent support)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

────────────────────────────────────────
Cellulose acetate solution composition ────────────────────────────────────────
Cellulose acetate having an acetylation degree of 60.9% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (No. 1) 2 solvents) 45 parts by mass Dye (360FP, manufactured by Sumika Finechem Co., Ltd.) 0.0009 parts by mass -------------------- ────────────

In another mixing tank, 16 parts by mass of the hydrophobic compound (2), 80 parts by mass of methylene chloride and 20 parts by mass of methanol were added and stirred while heating to prepare a hydrophobic compound solution.
To 464 parts by mass of the cellulose acetate solution, 36 parts by mass of the hydrophobic compound solution and 1.1 parts by mass of silica fine particles (R972, manufactured by Irosil Co., Ltd.) were mixed, and stirred sufficiently to prepare a dope. The addition amount of the hydrophobic compound was 5.0 parts by mass with respect to 100 parts by mass of cellulose acetate. Moreover, the addition amount of silica fine particles was 0.15 mass part with respect to 100 mass parts of cellulose acetate.

  The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., it was dried for 1 minute, peeled off, and then stretched 28% in the width direction using a tenter with a drying air of 140 ° C. Then, it dried with 135 degreeC drying air for 20 minutes, and manufactured the transparent support body whose residual solvent amount is 0.3 mass%.

The width of the transparent support was 1340 mm and the thickness was 92 μm.
The transparent support was conditioned and conditioned for 2 hours under the conditions of a temperature of 20 ° C. and a relative humidity of 20%, and the retardation value at a wavelength of 590 nm was measured using an ellipsometer (M-150, manufactured by JASCO Corporation). When (Re) was measured, it was 38.0 nm. Moreover, it was 175.0 nm when the retardation value (Rth) in wavelength 590nm was measured.
Next, the transparent support was temperature-controlled and humidity-controlled for 2 hours under conditions of a temperature of 10 ° C. and a relative humidity of 20%. Similarly, the retardation value (Re) at a wavelength of 590 nm was measured. there were. Moreover, it was 175.2 nm when the retardation value (Rth) in wavelength 590nm was measured.
A 1.0 N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the transparent support at 10 cc / m ^2. Then, after maintaining at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were deleted with an air knife. Then, it dried at 100 degreeC for 15 second.
The contact angle of the alkali-treated surface with pure water was measured and found to be 42 °.

(Formation of alignment film)
On the alkali-treated surface of the transparent support, an alignment film coating solution having the following composition was applied at 28 ml / m ² with a # 16 wire bar coater. The alignment film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds.

────────────────────────────────────────
Alignment film coating solution composition ────────────────────────────────────────
Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight Citrate ester (AS3, Sankyo Chemical Co., Ltd.) 0.35 parts by weight ────────────────────────────────────

(Rubbing process)
The transparent support on which the alignment film is formed is transported at a speed of 20 m / min, a rubbing roll (300 mm diameter) is set so as to be rubbed at 45 ° with respect to the longitudinal direction, and rotated at 650 rpm. A rubbing treatment was performed on the alignment film installation surface. The contact length between the rubbing roll and the transparent support was set to 18 mm.

(Formation of optically anisotropic layer)
To 102 kg of methyl ethyl ketone, the following discotic liquid crystal compound 41.01 kg, ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 4.06 kg, cellulose acetate butyrate (CAB531-1, yeast) Mand Chemical Co., Ltd.) 0.45 Kg, Photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 1.35 Kg, Sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 0.45 Kg were dissolved and applied. A liquid was prepared. The coating solution was continuously applied to the alignment film surface of the transparent support transported at 20 m / min by rotating a # 3.0 wire bar at 391 rotations in the same direction as the film transport direction.

  The temperature is continuously heated from room temperature to 100 ° C., the solvent is dried, and then the film surface wind speed of the disc-like optical anisotropic layer is 2.5 m / sec in the drying zone at 130 ° C. for about 90 seconds. Heated to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 80 ° C., and an ultraviolet ray with an illuminance of 600 mW is applied by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) with the surface temperature of the film being about 100 ° C. Irradiation was performed for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound was fixed to the alignment. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation sheet was produced.

When the viscosity of the optically anisotropic layer was measured at a film surface temperature of 127 ° C., it was 695 cp. The viscosity is a result of measuring a liquid crystal layer (excluding the solvent) having the same composition as the optically anisotropic layer with a heating type E-type viscosity system.
A part of the produced roll-shaped optical compensation sheet was cut out and used as a sample to measure optical characteristics.
The optical compensation sheet is temperature-controlled and humidity-controlled for 2 hours under the conditions of a temperature of 20 ° C. and a relative humidity of 20%, and the retardation value at a wavelength of 590 nm is measured using an ellipsometer (M-150, manufactured by JASCO Corporation). When (Re) was measured, it was 30.0 nm. Further, the angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface continuously changed in the depth direction of the layer, and averaged 28 °. Furthermore, when only the optical anisotropic layer was peeled from the sample and the average direction of the molecular symmetry axis of the optical anisotropic layer was measured, it was 45 ° with respect to the longitudinal direction of the optical compensation sheet.
Next, the optical compensation sheet was temperature-controlled and humidity-controlled for 2 hours under the conditions of a temperature of 10 ° C. and a relative humidity of 20%. Similarly, the retardation value (Re) at a wavelength of 590 nm was measured. there were.
When the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

(Preparation of polarizing plate)
Using a polyvinyl alcohol-based adhesive, the optical compensation sheet was attached to one side of the polarizing film with the transparent support surface. Further, a commercially available triacetylcellulose film (TD-80U: manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. .
The longitudinal direction of the polarizing film, the longitudinal direction of the transparent support, and the longitudinal direction of the commercially available triacetyl cellulose film were all arranged in parallel. In this way, a polarizing plate having an optical compensation sheet (only) was produced.
Moreover, the optical compensation sheet | seat was affixed on the one side of the polarizing film on the transparent support surface using the polyvinyl alcohol-type adhesive agent. Further, the antireflection film (Fuji Film CV Clearview UA, manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol adhesive.
The longitudinal direction of the polarizing film, the longitudinal direction of the transparent support, and the longitudinal direction of the commercially available triacetyl cellulose film were all arranged in parallel. In this way, a polarizing plate having an optical compensation sheet and an antireflection film was produced.

(Preparation of bend alignment liquid crystal cell)
A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and the alignment film was rubbed. The obtained two glass substrates were faced to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 4.5 μm. A liquid crystal compound having a Δn of 0.1396 (ZLI1132, manufactured by Merck & Co., Inc.) was injected into the cell gap to prepare a bend alignment liquid crystal cell. The size of the liquid crystal cell was 20 inches.

(Production of liquid crystal display device)
A polarizing plate having an optical compensation sheet (only) and a polarizing plate having an optical compensation sheet and an antireflection film were attached so as to sandwich the produced bend alignment cell. A polarizing plate having an optical compensation sheet and an antireflection film is on the viewing side. The optical anisotropic layer of the polarizing plate faces the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the optical anisotropic layer facing the liquid crystal cell are arranged to be antiparallel.

(Evaluation of liquid crystal display devices)
A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally white mode of 2V white display and 5V black display was set. Using the measurement ratio (EZ-Contrast 160D, manufactured by ELDIM) with the transmittance ratio (white display / black display) as the contrast ratio, the viewing angle can be adjusted in 8 steps from black display (L1) to white display (L8). It was measured. Further, the front contrast (CR: white display brightness / black display brightness) was obtained.
The above measurement was performed twice under the conditions of a temperature of 20 ° C. and a relative humidity of 20% and a temperature of 10 ° C. and a relative humidity of 20%.
The results are shown in Table 1.
Further, the liquid crystal display device was adjusted to a halftone on the entire surface, and unevenness was evaluated. As a result, no unevenness was observed from any direction.

[Example 2]
(Preparation of transparent support)
The dope was prepared by mixing the cellulose acetate solution prepared in Example 1 and the retardation increasing agent solution and thoroughly stirring. The addition amount of the retardation increasing agent was 7.5 parts by mass with respect to 100 parts by mass of cellulose acetate.

The obtained dope was cast using a band casting machine in the same manner as in Example 1, and the residual solvent amount was 0.3% by mass in the same manner as in Example 1 except that the draw ratio was 20%. A transparent support was produced.
The width of the transparent support was 1500 mm and the thickness was 95 μm.
The transparent support was conditioned and conditioned for 2 hours under the conditions of a temperature of 20 ° C. and a relative humidity of 20%, and the retardation value at a wavelength of 590 nm was measured using an ellipsometer (M-150, manufactured by JASCO Corporation). When (Re) was measured, it was 35.0 nm. Moreover, it was 200.0 nm when the retardation value (Rth) in wavelength 590nm was measured.
Next, the transparent support was conditioned and conditioned for 2 hours under conditions of a temperature of 10 ° C. and a relative humidity of 20%. Similarly, the retardation value (Re) at a wavelength of 590 nm was measured. there were. Moreover, it was 200.2 nm when the retardation value (Rth) in wavelength 590nm was measured.
The transparent support was immersed in a 2.0N potassium hydroxide solution (25 ° C.) for 2 minutes, neutralized with sulfuric acid, washed with pure water and dried. The surface energy of the transparent support was determined by a contact angle method and found to be 63 mN / m.

(Formation of alignment film)
On a transparent support, a coating solution having the following composition was applied at 28 ml / m ² with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds, and further with warm air of 90 ° C. for 150 seconds.

────────────────────────────────────────
Alignment film coating solution composition ────────────────────────────────────────
Modified polyvinyl alcohol used in Example 1 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight Citrate ester (AS3, manufactured by Sankyo Chemical Co., Ltd.) 0.35 parts by weight ────────────────────────────────────────

(Rubbing process)
The transparent support was transported at a speed of 20 m / min, and a rubbing roll (300 mm diameter) set so that the rubbing direction was 45 ° with respect to the longitudinal direction was rotated at 450 rpm on the alignment film installation surface of the transparent support. A rubbing treatment was performed.

(Formation of optically anisotropic layer)
To 102 Kg of methyl ethyl ketone, 41.01 Kg of the discotic liquid crystal compound used in Example 1, 4.06 Kg of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB531) −1, manufactured by Eastman Chemical Co., Ltd.) 0.29 Kg, photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Co., Ltd.) 1.35 Kg, sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.45 Kg, Quen 0.45 kg of acid ester (AS3, Sankyo Chemical Co., Ltd.) was dissolved. To the solution, 0.1 kg of the following fluoroaliphatic group-containing copolymer was added to prepare a coating solution. The coating solution was continuously applied to the alignment film surface of the transparent support being transported at 20 m / min by rotating a # 2.7 wire bar at 391 rotations in the same direction as the film transport direction.

  In the process of continuously heating from room temperature to 100 ° C., the solvent is dried, and then heated for about 90 seconds in the drying zone at 135 ° C. so that the wind speed corresponding to the disc-like optical anisotropic layer is 1.5 m / sec. The discotic liquid crystal compound was aligned. Next, the film is transported to a drying zone at 80 ° C., and an ultraviolet ray with an illuminance of 600 mW is applied by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) with the surface temperature of the film being about 100 ° C. Irradiation was performed for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound was fixed to the alignment. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation sheet was produced.

When the viscosity of the optically anisotropic layer was measured at a film surface temperature of 131 ° C., it was 600 cp. The viscosity is a result of measuring a liquid crystal layer (excluding the solvent) having the same composition as the optically anisotropic layer with a heating type E-type viscosity system.
A part of the roll-shaped optical compensation sheet was cut out and used as a sample to measure optical characteristics.
The optical compensation sheet is temperature-controlled and humidity-controlled for 2 hours under the conditions of a temperature of 20 ° C. and a relative humidity of 20%, and the retardation value at a wavelength of 590 nm is measured using an ellipsometer (M-150, manufactured by JASCO Corporation). When (Re) was measured, it was 28.0 nm. Further, the angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface changed continuously in the depth direction of the layer, and averaged 33 °. Furthermore, when only the optical anisotropic layer was peeled from the sample and the average direction of the molecular symmetry axis of the optical anisotropic layer was measured, it was 45.5 ° with respect to the longitudinal direction of the optical compensation sheet.
Next, the optical compensation sheet was temperature-controlled and humidity-controlled for 2 hours under the conditions of a temperature of 10 ° C. and a relative humidity of 20%. Similarly, the retardation value (Re) at a wavelength of 590 nm was measured. there were.
When the polarizing plate was placed in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

(Preparation of polarizing plate)
Using a polyvinyl alcohol-based adhesive, the optical compensation sheet was attached to one side of the polarizing film on the transparent support surface. Further, a commercially available triacetylcellulose film (TD-80U, manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. .
The longitudinal direction of the polarizing film, the longitudinal direction of the transparent support, and the longitudinal direction of the commercially available triacetyl cellulose film were all arranged in parallel. In this way, a polarizing plate was produced.

(Preparation of bend alignment liquid crystal cell)
A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and the alignment film was rubbed. The obtained two glass substrates were faced to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 6 μm. A liquid crystal compound having a Δn of 0.1396 (ZLI1132, manufactured by Merck & Co., Inc.) was injected into the cell gap to prepare a bend alignment liquid crystal cell. The size of the liquid crystal cell was 20 inches.

(Production of liquid crystal display device)
Two polarizing plates were attached so as to sandwich the prepared bend alignment cell. The optical anisotropic layer of the polarizing plate faces the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the optical anisotropic layer facing the liquid crystal cell are arranged to be antiparallel.

(Evaluation of liquid crystal display devices)
A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally white mode with 2 V white display and 6 V black display was set. Using the measurement ratio (EZ-Contrast 160D, manufactured by ELDIM) with the transmittance ratio (white display / black display) as the contrast ratio, the viewing angle can be adjusted in 8 steps from black display (L1) to white display (L8). It was measured. Further, the front contrast (CR: white display brightness / black display brightness) was obtained.
The above measurement was performed twice under the conditions of a temperature of 20 ° C. and a relative humidity of 20% and a temperature of 10 ° C. and a relative humidity of 20%.
The results are shown in Table 1.
Further, the liquid crystal display device was adjusted to a halftone on the entire surface, and unevenness was evaluated. As a result, no unevenness was observed from any direction.

[Comparative Example 1]
(Preparation of transparent support)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

────────────────────────────────────────
Cellulose acetate solution composition ────────────────────────────────────────
Cellulose acetate having an acetylation degree of 60.9% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (No. 1) 2 Solvents) 45 parts by weight Dye (360FP, manufactured by Sumika Finechem Co., Ltd.) 0.0009 parts by weight ─────────────────────────── ─────────────

  To 499 parts by mass of the cellulose acetate solution, 1.1 parts by mass of silica fine particles (R972, manufactured by Irosil Co., Ltd.) were mixed and sufficiently stirred to prepare a dope. The amount of silica fine particles added was 0.15 parts by mass with respect to 100 parts by mass of cellulose acetate.

  The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., it was dried for 1 minute, peeled off, and then stretched by 20% in the width direction using a tenter with a drying air of 140 ° C. Then, it dried with 135 degreeC drying air for 60 minutes, and manufactured the transparent support body whose residual solvent amount is 1.3 mass%.

The width of the transparent support was 1340 mm and the thickness was 280 μm.
The transparent support was conditioned and conditioned for 2 hours under the conditions of a temperature of 20 ° C. and a relative humidity of 20%, and the retardation value at a wavelength of 590 nm was measured using an ellipsometer (M-150, manufactured by JASCO Corporation). When (Re) was measured, it was 25.0 nm. The retardation value (Rth) at a wavelength of 590 nm was measured and found to be 155.0 nm.
Next, the transparent support was conditioned and conditioned for 2 hours under the conditions of a temperature of 10 ° C. and a relative humidity of 20%. Similarly, the retardation value (Re) at a wavelength of 590 nm was measured. there were. Moreover, it was 152.8 nm when the retardation value (Rth) in wavelength 590nm was measured.
A 1.0 N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the transparent support at 10 cc / m ^2. Then, after maintaining at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were deleted with an air knife. Then, it dried at 100 degreeC for 15 second.
The contact angle of the alkali-treated surface with pure water was measured and found to be 42 °.

(Formation of alignment film)
On a transparent support, a coating solution having the following composition was applied at 28 ml / m ² with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds, and further with warm air of 90 ° C. for 150 seconds.

────────────────────────────────────────
Alignment film coating solution composition ────────────────────────────────────────
Modified polyvinyl alcohol used in Example 1 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight ─────────────────── ─────────────────────

(Rubbing process)
The transparent support on which the alignment film is formed is transported at a speed of 20 m / min, a rubbing roll (300 mm diameter) is set so as to be rubbed at 45 ° with respect to the longitudinal direction, and rotated at 650 rpm. A rubbing treatment was performed on the alignment film installation surface. The contact length between the rubbing roll and the transparent support was set to 18 mm.

(Formation of optically anisotropic layer)
102 kg of methyl ethyl ketone, 41.01 kg of the discotic liquid crystal compound used in Example 1, 4.06 kg of ethylene oxide-modified diacrylate, 0.58 kg of cellulose acetate butyrate (CAB531-1, manufactured by Eastman Chemical Co., Ltd.), photopolymerization started A coating solution was prepared by dissolving 1.35 kg of an agent (Irgacure 907, manufactured by Ciba Geigy) and 0.45 kg of citrate ester (AS3, manufactured by Sankyo Chemical Co., Ltd.). The # 3.6 wire bar was rotated 391 times in the same direction as the film transport direction, and the coating solution was continuously applied to the alignment film surface of the transparent support transported at 20 m / min.

  In the process of continuously heating from room temperature to 100 ° C., the solvent is dried, and then heated in a drying zone at 135 ° C. for about 60 seconds so that the wind speed corresponding to the disc-like optical anisotropic layer becomes 1.5 m / sec. The discotic liquid crystal compound was aligned. Next, the film is transported to a drying zone at 20 ° C., and an ultraviolet ray irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) is irradiated with ultraviolet rays having an illuminance of 100 mW with the surface temperature of the film being about 100 ° C. Irradiation was performed for 1 second, the crosslinking reaction was advanced, and the discotic liquid crystal compound was fixed to the alignment. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation sheet was produced.

A part of the obtained roll-shaped optical compensation sheet was cut out and used as a sample to measure optical characteristics.
The optical compensation sheet is temperature-controlled and humidity-controlled for 2 hours under the conditions of a temperature of 20 ° C. and a relative humidity of 20%, and the retardation value at a wavelength of 590 nm is measured using an ellipsometer (M-150, manufactured by JASCO Corporation). When (Re) was measured, it was 40.0 nm. Further, the angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface changed continuously in the depth direction of the layer, and averaged 33 °. Furthermore, when only the optical anisotropic layer was peeled from the sample and the average direction of the molecular symmetry axis of the optical anisotropic layer was measured, it was 37.0 ° with respect to the longitudinal direction of the optical compensation sheet.
Next, the optical compensation sheet was temperature-controlled and humidity-controlled for 2 hours under conditions of a temperature of 10 ° C. and a relative humidity of 20%. Similarly, the retardation value (Re) at a wavelength of 590 nm was measured. there were.

(Preparation of polarizing plate)
A polarizing plate was produced in the same manner as in Example 2 except that the produced optical compensation sheet was used.

(Production and evaluation of liquid crystal display devices)
A liquid crystal display device was produced and evaluated in the same manner as in Example 2 except that the produced polarizing plate was used.
The results are shown in Table 1.
Further, the liquid crystal display device was adjusted to a halftone on the entire surface, and unevenness was evaluated. As a result, unevenness was detected in a lattice shape in an inversion region with an upper viewing angle of 55 ° or more and a lower viewing angle of 60 ° or more.

Table 1 ─────────────────────────────────────────
Measured at a temperature of 20 ° and a relative humidity of 20% at a measurement temperature of 10 ° and a relative humidity of 20% Optical compensation Front-con view angle Front-con view angle
Seat Trust Up / Down Left / Right Trust Up / Down Left / Right──────────────────────────────────── ─────
Example 1 480 80/80 80/80 485 80/80 80/80
Example 2 530 80/80 80/80 525 80/80 80/80
Comparative Example 1 400 60/60 70/65 300 45/45 60/50
────────────────────────────────────────
(註)
Viewing angle: Angle at which the contrast ratio> 10 (°)

It is a cross-sectional schematic diagram of the liquid crystal display device of OCB mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight apparatus 11 Backlight light source 12 Light-guide plate 2 Backlight side polarizing plate 21 2nd transparent protective film 22 Polarizing film 23 1st transparent protective film which consists of a cellulose acylate film 24 Alignment film 25 Optical difference formed from the liquid crystalline compound Directional layer 251 Discotic liquid crystal compound 3 Liquid crystal cell 31 Lower glass substrate 32 Lower transparent conductive film 33 Lower alignment film 34 Liquid crystal layer 341 Rod-like liquid crystalline molecule 35 Upper alignment film 36 Upper transparent conductive film 37 Color filter 371 Blue region 372 Green region 373 Red region 374 Black matrix 38 Upper glass substrate 4 Viewing side polarizing plate 41 Optical anisotropic layer formed from liquid crystal compound 411 Discotic liquid crystal compound 42 Alignment film 43 First transparent protective film made of cellulose acylate film 44 Polarizing film 45 Second transparent protective film 46 Light diffusion 461 first light-transmitting particulate 462 second light-transmitting particulate dotted arrow (alignment film) rubbing directions

Claims (10)

  The in-plane retardation value measured at a temperature of 20 ° C. and a relative humidity of 20% is in the range of 97 to 103% of the in-plane retardation value measured at a temperature of 10 ° C. and a relative humidity of 20%. An optical compensation sheet, characterized by being.   An in-plane retardation value measured at a temperature of 10 ° C. and a relative humidity of 20%, consisting of an optically anisotropic layer formed from a liquid crystal compound and a transparent support, and an in-plane retardation value measured at a temperature of 10 ° C. and a relative humidity of 20%. An optical compensation sheet characterized by being in the range of 97 to 103% of the above.   The optical compensation sheet according to claim 2, wherein the transparent support comprises a cellulose acylate film.   The in-plane retardation value measured at a temperature of 20 ° C. and a relative humidity of 20% of the cellulose acylate film is within the range of 97 to 103% of the in-plane retardation value measured at a temperature of 10 ° C. and a relative humidity of 20%. Item 4. The optical compensation sheet according to Item 3.   The optical compensation sheet according to claim 1 or 4, wherein the cellulose acylate film contains 4 to 15% by mass of a hydrophobic compound having a molecular weight of 200 to 700 and an oxygen atom number of 2 or less based on the cellulose acylate.   The optical compensation sheet according to claim 5, wherein the hydrophobic compound has 1 or less oxygen atoms.   A liquid crystal display device comprising a liquid crystal cell and two polarizing plates arranged on both sides thereof, wherein the optical device according to any one of claims 1 to 6 is provided between the liquid crystal cell and at least one polarizing plate. A liquid crystal display device comprising a compensation sheet.   It is a liquid crystal display device which consists of a reflecting plate, a liquid crystal cell, and a polarizing plate, Comprising: It has the optical compensation sheet as described in any one of Claims 1 thru | or 6 between a liquid crystal cell and a polarizing plate. Liquid crystal display device.   The liquid crystal display device according to claim 7 or 8, wherein the response time is 300 ms or less.   The liquid crystal display device according to claim 7, which is an OCB method.

Images