JP2003232923A - Optical compensation film, elliptically polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical compensation film having a large effect of improving the viewing angle of an ECB mode liquid crystal display. <P>SOLUTION: In the optical compensation film having an optically anisotropic transparent supporting body having a longitudinal direction and an optically anisotropic layer with fixed alignment of a discotic liquid crystal compound, the phase lagging axis of the optically anisotropic transparent supporting body is controlled to be neither parallel nor perpendicular to the longitudinal direction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical compensation film for improving a viewing angle of a liquid crystal display device. The present invention also relates to an elliptically polarizing plate in which an optical compensation film and a polarizing film are bonded together. Furthermore, the present invention also relates to a liquid crystal display device using a liquid crystal cell and an optical compensation film or an elliptically polarizing plate.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) is a CRT (cat
Compared to hode ray tube), it has excellent features such as thinness, light weight, and low power consumption, and it has come to be widely used in notebook computers, monitors, TVs, PDAs, mobile phones, car navigation systems, video cameras, etc. It was The TN (twisted nematic) alignment mode using twisted nematic liquid crystal is the most popular at present. In this method, in principle, the problem of the viewing angle characteristics that the display color and contrast change depending on the viewing direction, and the response speed There is a problem of ECB
VA with homeotropic alignment in mode, especially when no voltage is applied
New liquid crystal display devices such as N mode, OCB mode of bend alignment, HAN mode in which one substrate side is vertically aligned and the other is horizontally aligned, and homogeneous alignment mode have been developed.

US Pat. Nos. 4,583,825 and 54,104.
No. 22 discloses a liquid crystal display device using a bend alignment mode liquid crystal cell in which a rod-shaped liquid crystal is aligned in a substantially opposite direction (symmetrically) in an upper portion and a lower portion of the liquid crystal cell. . Since the rod-shaped liquid crystal molecules are symmetrically aligned in 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.
Also called y Compensatory Bend) mode.

In the bend alignment method, it is necessary to use an optical compensation film in order to cancel the retardation on the front side and further widen the viewing angle. As this optical compensation film, an optically anisotropic layer is formed on a transparent support. A film having a film is disclosed in JP-A-6-214116 and US Pat.
583679, 5646703, West German Patent Publication 3
91116A1. In order to further improve the viewing angle of a bend alignment mode liquid crystal display device, it has been studied to use an optical compensation film similar to that of the TN alignment mode.
No. 22, JP-A-9-197397 (US Pat. No. 5,805,253), WO96 / 37804 (European patent application 0783128A) and JP-A-11-316378 (US Pat. No. 60644).
No. 57) discloses an optical compensation film having an optically anisotropic layer formed of discotic liquid crystal, and a bend alignment mode liquid crystal display device using the same. An extremely wide viewing angle can be obtained by using an optical compensation film having an optically anisotropic layer formed of discotic liquid crystal in a bend alignment mode liquid crystal display device.

Furthermore, the 42nd Spring Applied Physics Society (29
a-SZC-20, 1995) applies this idea to a reflective LCD in a HAN mode (Hybrid-a).
liquid-nematic mode) A liquid crystal cell has been proposed. That is, the HAN mode liquid crystal cell utilizes the hybrid alignment on the upper side of the bend alignment cell, and a biaxially stretched film has been proposed as an optical compensation film. To further improve the viewing angle of the HAN mode utilizing the hybrid orientation, it is disclosed in Japanese Patent Laid-Open No. 9-2191
No. 4, Japanese Patent No. 3118197 and the like describe an optical compensation film having an optically anisotropic layer formed of discotic liquid crystal, and a HAN mode liquid crystal display device using the same. OCB mode, HAN mode, V
An ECB mode liquid crystal cell such as an AN mode and a homogeneous alignment mode has a conventional liquid crystal mode (TN mode, ST mode).
Compared with the N mode), the liquid crystal display device is characterized by a wide viewing angle and a high response speed, and is expected to be developed not only as a transmission type but also as a reflection type or semi-transmission type liquid crystal display device in the future.

However, OCB mode, HAN mode, VA
In the optical compensation film described in Japanese Patent No. 3118197 used in ECB mode liquid crystal cells such as N mode and homogeneous alignment mode, the direction of the slow axis of the support is parallel to the longitudinal direction of the roll-shaped polymer film, It was necessary to perform rubbing for orienting the discotic liquid crystal at an angle of 45 ° with respect to the transport direction. Therefore, there is a manufacturing problem that a long rubbing roll is required, rubbing does not work well, alignment of the discotic liquid crystal is insufficient, or conveyance of a long film is difficult.

[0007]

The object of the present invention is to provide an OC
Another object of the present invention is to provide an optical compensation film or an elliptically polarizing plate for improving the viewing angle of an ECB mode liquid crystal display device such as B, HAN, VAN mode and homogeneous alignment mode. An object of the present invention is to provide an optical compensation film or an elliptical deflection plate which can be manufactured in a large size, easily and efficiently.

[0008]

An object of the present invention is to provide an optical compensation film of the following (1) to (6), (7) to (12).
And the liquid crystal display device of (13) and (14).

(1) An optically-anisotropic transparent support having an optically anisotropic transparent support having a longitudinal direction and an optically anisotropic layer having a fixed orientation of a discotic liquid crystalline compound. The optical compensation film is characterized in that the slow axis of is present in a direction which is neither substantially parallel nor perpendicular to the longitudinal direction.

(2) The optical compensation film as described in (1), wherein the angle between the slow axis of the transparent support and the longitudinal direction of the optical compensation film is in the range of 10 ° to 80 °. (3) The optical compensation film according to (1) or (2), wherein the in-plane standard deviation of the angle formed by the slow axis of the transparent support and the longitudinal direction of the optical compensation film is within 3 °. (4) The optical compensation film according to any one of (1) to (3), wherein the transparent support is made of cellulose acetate.

(5) The values of Re and Rth showing the optical anisotropy of the transparent support of the optical compensation film are 10 to 70 n, respectively.
m, the optical compensation film according to any one of (1) to (4) in the range of 70 to 400 nm. Here, Re and Rth are values defined by the following formulas (I) and (II), respectively. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d [where nx is the refractive index in the slow axis direction in the plane of the transparent support; ny is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support; and d is the thickness of the transparent support].

(6) R showing the optical anisotropy of the optically anisotropic layer
The values of e (0 °), Re (40 °), and Re (-40 °) are 35 ± 25 nm, 105 ± 50 nm, and 35 ± 2, respectively.
The optical compensation film according to any one of (1) to (5), which is in a range of 5 nm. Here, Re (0 °), Re (4
0 °) and Re (−40 °) are the minimum values from the normal direction and the normal direction in the plane including the direction opposite to the direction in which the retardation of the optically anisotropic layer takes the minimum value and the normal line, respectively. It represents the retardation value of the optical compensation film measured with light having a wavelength of 633 nm from a direction inclined by 40 ° in the direction opposite to the direction in which it is taken, and a direction inclined by 40 ° in the direction taking the minimum value from the normal.

(7) A polarizing film having a longitudinal direction and an optically anisotropic transparent support having a longitudinal direction are arranged so that their longitudinal directions are parallel to each other, and a discotic liquid crystalline compound An elliptically polarizing plate having an optically anisotropic layer with a fixed orientation, in which the transmission axis of the polarizing film exists in a direction that is neither substantially parallel to nor perpendicular to the longitudinal direction, and is an optically anisotropic transparent support. The slow axis of the body exists in a direction that is neither substantially parallel nor perpendicular to the longitudinal direction, and the transmission axis of the polarizing film and the slow axis of the optically anisotropic transparent support are substantially An elliptically polarizing plate characterized by being parallel.

(8) The elliptically polarizing plate according to (7), wherein the angle formed by the slow axis of the transparent support and the longitudinal direction of the optical compensation film is in the range of 10 ° to 80 °. (9) The elliptical polarizing plate according to (7) or (8), wherein the in-plane standard deviation of the angle formed by the slow axis of the transparent support and the longitudinal direction of the optical compensation film is within 3 °. (10) The elliptically polarizing plate according to any one of (7) to (9), wherein the transparent support is made of cellulose acetate.

(11) The values of Re and Rth showing the optical anisotropy of the transparent support of the optical compensation film are 10 to 70, respectively.
nm, 70-400 nm range, The elliptically polarizing plate as described in any one of (7)-(10) characterized by the above-mentioned. (I) Re = (nx-ny) * d (II) Rth = {(nx + ny) / 2-nz} * d Here, Re and Rth are the values defined by said (5). (12) Re (0) indicating the optical anisotropy of the compensation film.
°), Re (40 °), and Re (-40 °) values are 35 ± 25 nm, 105 ± 55 nm, and 85 ± 25 nm, respectively.
The elliptically polarizing plate according to any one of (7) to (11), which is in the range of. Where Re (0 °), Re (40 °), R
e (−40 °) is the value defined in (6) above.

(13) A liquid crystal display device having a liquid crystal cell, at least one polarizing plate, and an optical compensation film disposed between the liquid crystal cell and the polarizing plate, wherein the optical compensation film is (1) to A liquid crystal display device, which is obtained by cutting the long optical compensation film described in any one of (6). (14) A liquid crystal display device having a liquid crystal cell and an elliptically polarizing plate, which is obtained by cutting the long elliptically polarizing plate described in any one of (7) to (12). A liquid crystal display device characterized in that

In the present specification, "substantially parallel" or "substantially perpendicular" means within ± 5 ° with respect to a precise angle. Therefore, “not substantially parallel or perpendicular” means that the angle (the narrower angle) is more than 5 ° and less than 85 °. In the present invention, “long optical compensation film”, “long polarizing film” and “long elliptically polarizing plate” refer to those having a shape having a longitudinal direction in film production, and in a long roll shape. One is a typical example, and it is preferable that the longitudinal direction is at least 10 times or more the width.

[0018]

In the present invention, the slow axis of the transparent support is inclined at 45 ° with respect to the transport direction of the long film, and rubbing necessary for aligning the discotic liquid crystal is
This can be done by installing the rubbing roll at a right angle to the transport direction of the transparent support, and the equipment is also simpler than installing the rubbing roll diagonally as in the past, and it is possible to manufacture efficiently. became. As a result, it is used for a liquid crystal display device for ECB mode such as OCB mode, HAN mode, VAN mode and homogeneous alignment mode.
An optical compensation film that can be manufactured easily and efficiently is provided, and OCB mode, H that utilizes wide viewing angle and high-speed response
The ECB mode liquid crystal display device such as the AN mode, the VAN mode, and the homogeneous alignment mode can be put into practical use.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Optical Compensation Film The optical compensation film of the present invention has at least a transparent support having optical anisotropy and an optically anisotropic layer in which the orientation of discotic liquid crystal is fixed. Regarding the optical compensation film having the constitution of JP-A-9-197397 and JP-A-9-21144.
No. 4, No. 9-222600, No. 9-230333,
9-230334, 11-212078, 1
It is disclosed in the respective gazettes of 1-316378 and 11-352328.

[Transparent Support] The transparent support used in the present invention is preferably a polymer film having a light transmittance of 80% or more. The polymer film is preferably one that does not easily exhibit birefringence due to external force,
For example, cellulose-based polymer, norbornene-based polymer (eg, ARTON, manufactured by JSR Corporation); ZEONOR,
Made by Nippon Zeon Co., Ltd .; ZEONEX, Nippon Zeon Co., Ltd.
Manufactured) and polymethylmethacrylate.

Cellulosic polymers are preferred, cellulose esters are more preferred, and lower fatty acid esters of cellulose are even more preferred. The 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). The cellulose ester is preferably cellulose acetate, and examples thereof include diacetyl cellulose and triacetyl cellulose. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.

Generally, the second position and the third position of cellulose acetate
The hydroxyl groups at the 6- and 6-positions are not evenly distributed in 1/3 of the total substitution degree, and the substitution degree of the 6-position hydroxyl group tends to be small. In the present invention, cellulose acetate 6
It is preferable that the degree of substitution of the hydroxyl group at the position is higher than that at the positions of 2 and 3. The ratio of the substitution degree at the 6-position with respect to the total substitution degree at the 2-position, 3-position and 6-position is preferably 30% or more and 40% or less, and more preferably 31% or more.
Most preferably, it is 2% or more. The 6-position substitution degree of cellulose acetate is preferably 0.88 or more.

The 6-position hydroxyl group has 3 carbon atoms in addition to the acetyl group.
The above-mentioned acyl groups, propionyl group, butyroyl group,
It may be substituted with a valeroyl group, a benzoyl group, an acryloyl group or the like. The substitution degree at each position is measured by NMR.
You can ask for it. As the cellulose acetate of the present invention, paragraph number 0 of JP-A No. 11-5851 is used.
043 to 0044, Synthesis Example 1 described in paragraphs 0048 to 0049, and Synthesis Example 3 described in paragraphs 0051 to 0052.
Cellulose acetate obtained by the synthetic method of can be used.

In a liquid crystal display device using an optical compensation film, "frame-like display unevenness" may occur in the peripheral portion of the screen after a lapse of time after energization. This unevenness is due to an increase in the transmittance of the peripheral portion of the screen, and is particularly noticeable during black display. The cause is that a heat distribution from the backlight causes a temperature distribution within the liquid crystal cell surface, and this temperature distribution changes the optical characteristics (retardation value, slow axis angle) of the optical compensation film. The change in the optical characteristic of the optical compensation film is caused by the elastic deformation of the optical compensation film because the expansion or contraction of the optical compensation film due to the temperature rise is suppressed by the adhesion with the liquid crystal cell or the polarizing film.

In order to suppress the above-mentioned "frame-like display unevenness", it is preferable to use a polymer film having a high thermal conductivity for the transparent support of the optical compensation film, as a polymer film having a high thermal conductivity. Is, for example, cellulose acetate {0.22W / (m · ° C)}, low density polyethylene {0.34W / (m · ° C)}, ABS {0.3
6W / (m · ° C)}, polycarbonate {0.19W /
(M · ° C.)} is preferable. ZEONEX, which is a cyclic olefin polymer {0.20 W / (m · ° C.), manufactured by Nippon Zeon Co., Ltd.}, ZEONOR {0.20 W / (m ·
℃), manufactured by Nippon Zeon Co., Ltd.}, ARTON {0.20W
/ (M · ° C.), manufactured by JSR Corporation}.

Considering the above optical characteristics and thermal characteristics, the polymer film used for the transparent support of the present invention has a cellulose acetate having an acetylation degree of 59.0 to 61.5%. Film is preferred. Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The acetylation degree follows the measurement and calculation of the acetylation degree 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, more preferably 290 or more. The polymer film has Mw / Mn (Mw is a mass average molecular weight, Mn by gel permeation chromatography).
Preferably has a narrow molecular weight distribution (number average molecular weight).
The specific value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, and most preferably 1.4 to 1.6. preferable.

Materials of cellulose acetate film particularly preferable as the polymer film, various additives, characteristics,
Regarding the manufacturing method, etc.
1745, published on March 15, 2001, Institute of Invention).

[Anisotropy of Transparent Support] The transparent support of the present invention exhibits optical anisotropy, and Re retardation value and Rth retardation value showing the degree thereof are respectively
It is defined by the following formulas (I) and (II). (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d

In the formulas (I) and (II), nx is
Slow axis direction in the film plane (direction in which the refractive index is maximum)
Is the refractive index of. In formulas (I) and (II), ny
Is the refractive index in the fast axis direction (direction in which the refractive index is minimum) in the film plane. In the formula (II), nz is the refractive index in the thickness direction of the film. Formulas (I) and (II)
In, d is the thickness of the film in nm.

In the present invention, the Re retardation value of the transparent support is preferably 10 to 70 nm, and the Rth retardation value is preferably 70 to 400 nm. The birefringence (Δn: nx-ny) of the transparent support is
It is preferably 0.00025 to 0.00088. Further, the birefringence index {(nx +
ny) / 2-nz} is 0.00088 to 0.005
Is preferred.

[Slow axis angle of transparent support] The transparent support of the present invention has in-plane anisotropy, and the optical anisotropy thereof is a polymer film or a polymer to which a retardation increasing agent described later is added. The film can be developed by obliquely stretching the film, or by coating the polymer film with an alignment film and rubbing it obliquely to orient the rod-shaped liquid crystal obliquely.

In this case, the angle (slow axis angle) formed by the direction in which the refractive index is the largest in the plane (direction of the slow axis) and the longitudinal direction of the film in the form of a long roll (conveying direction) is an oblique stretching direction. It can be controlled by the angle or the angle of oblique rubbing, and is 10 ° to 80 °, more preferably 20 °.
To 70 °, more preferably 30 ° to 60 °, particularly preferably 40 ° to 50 °, about 45 °.
Is most preferred. The in-plane variation of the slow axis angle is preferably 3 ° or less, more preferably 2 ° or less, and more preferably 1 ° with respect to the average value of the slow axis angle.
Most preferably it is: Regarding the method of inclining the direction of the slow axis of the polymer film by stretching to a desired angle with respect to the method of conveying the film, see JP-A-60-15.
7831, JP-A-2-113920, and JP-A3-1.
24426, JP-A-3-182701, 4-JP
No. 164626, Japanese Patent Application Laid-Open No. 2000-9912, Japanese Patent Application No. 2001-247210, and the like.

For example, in Japanese Unexamined Patent Publication No. 3-182701, a plurality of pairs of left and right film holding points forming an angle of θ with the running direction are provided at both left and right ears of a continuous film.
It has been proposed to manufacture a film having a stretching axis of an arbitrary angle θ with respect to the running direction of the film by a mechanism in which each pair of points can be stretched in the direction of θ as the film runs. Further, in Japanese Patent Laid-Open No. 2-113920, both ends of the film are gripped between two rows of chucks traveling on a tenter rail arranged so that the traveling distances of the chucks in a predetermined traveling section are different. There has been proposed a manufacturing method in which the film is stretched in a direction oblique to the length direction of the film.

Further, in Japanese Unexamined Patent Publication No. 2000-9912, a plastic film is stretched uniaxially in a horizontal or vertical direction, and the left and right of the stretching direction are stretched at different speeds in a longitudinal or lateral direction different from the previous stretching direction. Then, it is proposed to tilt the orientation axis with respect to the uniaxial stretching direction. The draw ratio is preferably 3 to 100%. The thickness of the polymer film is preferably 40 to 140 μm, more preferably 70 to 120 μm.

[Retardation Raising Agent] In order to adjust the retardation of the transparent support of the present invention, a retardation raising agent can be added to the polymer film. Examples of the retardation increasing agent include aromatic compounds having at least two aromatic rings, such as triazines (triphenyl-1,3,5-triazine, tri-
m-tolyl-1,3,5-triazine etc.), tra
Diesters of ns-1,4-cyclohexanedicarboxylic acid (diesters of pn-hexylphenol, p-
Examples thereof include diesters of n-amylphenol. As another specific example, Japanese Patent Laid-Open No. 2000-11
1914, 2000-275434, P.
It is described in the specification of CT / JP00 / 02619 and the like.

Two or more kinds of aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. The molecular weight of the retardation increasing agent is preferably 300 to 800. When a cellulose acetate film is used as the polymer film, the aromatic compound is used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acetate. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, and more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of cellulose acetate.

[Surface Treatment of Polymer Film] When the optical compensation film of the present invention is used as a transparent protective film of a polarizing plate, it is preferable to surface-treat the polymer film. As the surface treatment, corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment or ultraviolet irradiation treatment is carried out. It is particularly preferable to carry out an acid treatment or an alkali treatment, that is, a saponification treatment for the polymer film.

[Alignment Film] The alignment film has a function of defining the alignment direction of the discotic liquid crystal in the optically anisotropic layer. The alignment film is formed by rubbing an organic compound (preferably a polymer), obliquely depositing an inorganic compound, forming a layer having microgrooves, or an organic compound (eg, ω-tricosanoic acid) by the Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride,
It can be provided by means such as accumulation of methyl stearate). Furthermore, an alignment film which has an alignment function by applying an electric field, a magnetic field, or light irradiation is also known.

The alignment film is preferably formed by rubbing a polymer. Preferred polymers include polyvinyl alcohol. Among them, modified polyvinyl alcohol having a hydrophobic group bonded thereto is particularly preferable. Since the hydrophobic group has an affinity for the discotic liquid crystal of the optically anisotropic layer, the discotic liquid crystal can be uniformly aligned by introducing the hydrophobic group into polyvinyl alcohol. The hydrophobic group is attached to the main chain end or side chain of polyvinyl alcohol. The hydrophobic group is preferably an aliphatic group having 6 or more carbon atoms (preferably an alkyl group or an alkenyl group) or an aromatic group.

When a hydrophobic group is bonded to the end of the main chain of polyvinyl alcohol, it is preferable to introduce a linking group between the hydrophobic group and the end of the main chain. Examples of linking groups include -S
-, - C (CN) R 1 -, - NR 2 -, - CS- and a combination thereof. R ₁ and R above
₂ is a hydrogen atom or a carbon atom number of 1 to 6, respectively.
Is an alkyl group (preferably an alkyl group having 1 to 6 carbon atoms).

[0041] When introducing polyvinyl alcohol hydrophobic group in the side chain of a part of the polyvinyl alcohol acetyl group vinyl acetate unit (-CO-CH _3), carbon atoms of 7 or more acyl groups (- CO-R ₃₎ to may be replaced. R ₃ is an aliphatic group or aromatic group having 6 or more carbon atoms. A commercially available modified polyvinyl alcohol (eg, MP103, MP203, R1130, manufactured by Kuraray Co., Ltd.) may be used.

The saponification degree of the (modified) polyvinyl alcohol used for the alignment film is preferably 80% or more.
The degree of polymerization of the (modified) polyvinyl alcohol is preferably 200 or more. The rubbing treatment is performed by rubbing the surface of the alignment film with paper or cloth in a certain direction several times. It is preferable to use a cloth in which fibers having uniform length and thickness are uniformly flocked.

In the present invention, rubbing is carried out by arranging a roll having the above-mentioned cloth stuck thereto in a direction orthogonal to the conveying direction of the polymer film provided with the alignment film, and with the hair tips of the cloth being in contact with the alignment film. , Polymer film 1-100m
Roll at 100 to 10,000 while sending at a speed of
It is performed by rotating at a speed of 0 times / minute. In order to stabilize the transport of the film and maximize the effect of rubbing, the angle formed by the roll and the transport direction (longitudinal direction) of the film is preferably controlled to 90 ° ± 5 °.

The alignment state of the discotic liquid crystal can be maintained even after the alignment film is removed after aligning the discotic liquid crystal of the optically anisotropic layer on the alignment film. That is, the alignment film is indispensable for aligning the discotic liquid crystal, but is not necessarily indispensable as the manufactured optical compensation film. When the alignment film is provided between the transparent support and the optically anisotropic layer, it is preferable to further provide an undercoat layer (adhesive layer) between the transparent support and the alignment film.

[Optically Anisotropic Layer] The optically anisotropic layer is made of discotic liquid crystal. Discotic liquid crystal
Generally, it has an optically negative uniaxiality. In the optical compensation film of the present invention, the discotic liquid crystal preferably has an angle formed by the disc surface and the transparent support surface that changes in the depth direction of the optically anisotropic layer (hybrid alignment). In the optically anisotropic layer, there is no direction or optical axis where the retardation value becomes 0. The optically anisotropic layer is preferably formed by aligning the discotic liquid crystal with the alignment film and fixing the discotic liquid crystal in the aligned state. The discotic liquid crystal is preferably fixed by a polymerization reaction.
The thickness of the optically anisotropic layer is preferably 0.5 to 100 μm, more preferably 0.5 to 30 μm.

Regarding discotic liquid crystals, various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst.,
vol. 71, page 111 (1981); Chemical Society of Japan, Quarterly Chemistry Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. C.
hem. Comm., page 1794 (1985); J. Zhang et al., JA
m. Chem. Soc., vol. 116, page 2655 (1994)). For the polymerization of discotic liquid crystals,
It is described in JP-A-8-27284. In order to fix the discotic liquid crystal by polymerization, it is preferable to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystal, and after alignment, crosslink by thermal polymerization or photopolymerization to fix the discotic liquid crystal. However, when the polymerizable group is directly bonded to the discotic core, it becomes difficult to maintain the alignment state in the polymerization reaction. Therefore, it is preferable to introduce a linking group between the discotic core and the polymerizable group.

Examples of the photopolymerization initiator which causes a polymerization reaction for fixing the aligned discotic liquid crystal while maintaining the aligned state include α-carbonyl compounds (US Pat.
No. 67661, No. 2376670).
Acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2951758). , Triarylimidazole dimer and p-aminophenyl ketone combination (US Pat.
No. 5,493,67), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,212,970). The amount of the photopolymerization initiator used is preferably 0.01 to 20 mass% of the solid content of the coating liquid, and 0.5
It is more preferable that the amount is 5 to 5% by mass.

The light irradiation for polymerizing the discotic liquid crystal molecules preferably uses ultraviolet rays. The irradiation energy is preferably 20 to 5000 mJ / cm _2, and more preferably in the range of 100 to 800 mJ / cm _2. Further, in order to accelerate the photopolymerization reaction, light irradiation may be carried out under heating conditions. A protective layer may be provided on the optically anisotropic layer.

[Liquid Crystal Cell] The liquid crystal display device of the present invention comprises:
For example, liquid crystal cells of various modes such as TN mode, STN mode, ECB mode such as OCB mode, HAN mode, VAN mode, and homogeneous alignment mode are used. Among them, OCB mode, HAN mode, VAN mode, or homogeneous alignment mode are used. ECB mode liquid crystal cells are preferred. For the liquid crystal cell, see '99
Market of PDP / LCD constituent materials and chemicals "1999
July 30, 2012, CMC, "EL, PDP, LCD
Display Technology and Market Trends- "2001 March
Mon, Toray Research Center, etc.

A liquid crystal cell using a liquid crystal having bend alignment (bend alignment cell) is a symmetrical cell, and a liquid crystal display device having this liquid crystal cell has a wide viewing angle. Similarly H
A reflective liquid crystal display device using an AN-aligned liquid crystal also has a wide viewing angle. A liquid crystal cell is generally composed of a substrate having a transparent electrode having an alignment film formed on a pair of surfaces, and a nematic liquid crystal layer enclosed between the substrates. In the bend alignment cell, a nematic liquid crystal that can be bend aligned in a liquid crystal cell to which a voltage is applied is generally used. The liquid crystal used in the bend alignment liquid crystal cell generally has a positive dielectric anisotropy. The angle of the orientation vector of the nematic liquid crystal with respect to the substrate changes due to the change in the voltage applied to the liquid crystal cell. Generally, the angle of the orientation vector of the nematic liquid crystal with respect to the substrate increases with an increase in the voltage applied to the liquid crystal cell, and the birefringence decreases. An image is obtained by this change in birefringence.

In the present invention, the bend orientation of the liquid crystal means that the orientation vector (that is, the director or the optical axis) of the liquid crystal molecules of the liquid crystal layer is symmetric (line symmetric) with respect to the center line of the liquid crystal layer
It also means that at least the region near the substrate has a bend portion. The bend portion refers to a portion where a line formed by the director in a region near the substrate is bent. That is, the bend orientation of the liquid crystal means that when a voltage is applied to the liquid crystal cell, the director of the liquid crystal molecules in the cell is almost parallel to the lower substrate in the vicinity of the lower substrate and the distance from the substrate. The angle between the director and the surface of the substrate increases with increasing, and the director becomes perpendicular or nearly perpendicular to the surface of the substrate in the region (center line region) where the distance between the upper substrate and the lower substrate is equal, and then the director As the distance from the lower substrate increases, the angle between the director and the surface of the substrate further increases, and eventually the director means that the liquid crystal molecules are aligned so as to be substantially parallel to the upper substrate near the upper substrate. . Near the centerline, the director may have a twisted orientation. Further, the directors in the region close to the upper and lower substrates or in the contact region may be tilted from the substrate surface (that is, may have a tilt angle).

In the bend-aligned liquid crystal cell, the product (Δn × d) of the refractive index anisotropy Δn of the liquid crystal compound and the thickness d of the liquid crystal layer of the liquid crystal cell is set to 1 in order to satisfy both luminance and viewing angle.
It is preferably in the range of 00 to 2000 nm, and 1
The range of 50 to 1700 nm is more preferable, and the range of 500 to 1500 nm is the most preferable.

The HAN alignment mode is well known in the field of liquid crystal display devices, and the HAN alignment cell has a structure in which the lower substrate is arranged at the center line of the bend alignment cell.
The alignment film on the lower substrate is a layer capable of homeotropic alignment of nematic liquid crystals. Examples of such an alignment film include an inorganic vapor deposition film, a surfactant layer, and an organic silane layer. The nematic liquid crystal used in the HAN-aligned cell of the present invention is generally a liquid crystal capable of forming a hybrid alignment by applying a voltage. In the HAN alignment cell, it is preferable that the liquid crystal is aligned substantially vertically on one substrate and the pretilt angle on the other substrate is 0 to 45 °. The product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 100 nm to 1000 nm, more preferably 300 to 800 nm. The substrate on the side of vertically aligning the liquid crystal may be the substrate on the reflection plate side or the substrate on the transparent electrode side.

The liquid crystal display device having the bend alignment cell or the HAN alignment cell has the self-compensation director region, but when the display device is viewed from a large angle (especially in the vertical direction), the light transmittance of the black display portion is high. Is increased, resulting in a decrease in contrast. By applying the optical compensation sheet of the present invention or the elliptically polarizing plate to the above cell, the contrast when viewed from the tilt direction can be greatly improved without lowering the contrast when viewed from the front.

[Polarizing Film] The polarizing film is mainly composed of a stretched polyvinyl alcohol film (hereinafter PVA). This PVA film is stretched and then dyed with iodine or a dichroic dye, or is dyed and then stretched, and then crosslinked with a boron compound to form a polarizing film.
Moreover, what stretched polyene and dyed similarly can also be used. As the protective film for the polarizing film, the above-mentioned optical compensation film, a λ / 4 plate, or an optically transparent polymer film having a small birefringence (for example, cellulose triacetate film) used as a protective film for an ordinary polarizing plate is used. Can be used.

The angle between the slow axis of the protective film and the transmission axis of the polarizing film is preferably 3 ° or less, more preferably 2 ° or less, and more preferably 1 ° or less. Most preferably, they are arranged so that The polarizing film preferably has a visible light transmittance of 80% or more and a polarization degree of 99% or more. The angle formed by the transmission axis of the polarizing film of the present invention and the longitudinal direction (conveying direction) of the polarizing film in the form of a long roll should be controlled by the angle of oblique stretching, like the transparent support of the optical compensation film described above. Can be 1
0 ° to 80 °, more preferably 20 ° to 70 °, even more preferably 30 ° to 60 °, particularly preferably 40 ° to 50 °, most preferably about 45 °.
The method described in Japanese Patent Application No. 2001-247210 is particularly preferable.

[Elliptic Polarizing Plate] A protective film is usually attached to both sides of the polarizing film. When the above-mentioned optical compensation film is used as this protective film, the support side is saponified, then coated with a PVA-based adhesive, and then saponified Fujicat TD80U (manufactured by Fuji Photo Film Co., Ltd.) An elliptically polarizing plate can also be obtained by applying the same pressure-sensitive adhesive and sticking the polarizing film so that the polarizing film is sandwiched therebetween. In the elliptically polarizing plate of the present invention, it is preferable that the transmission axis of the polarizing film and the slow axis of the transparent support of the optical compensation film are parallel to each other, and the transmission axis and the slow axis have the same angle with respect to the longitudinal direction of the film. In this case, both films can be bonded by roll-to-roll, which is preferable. The transmission axis of the polarizing film is inclined 45 ° with respect to the longitudinal direction, and the slow axis of the optical compensation film is 45 ° with respect to the longitudinal direction.
Particularly preferred is the case of inclination.

[Liquid Crystal Display Device] The liquid crystal display device of the present invention provides a dark display when the applied voltage is low and a bright display when the applied voltage is high, even in the normally white mode, which is a bright display when the applied voltage is low and a dark display when the applied voltage is high. It can also be used in the normally black mode. Regarding the driving method of the transmissive, reflective and semi-transmissive liquid crystal display device of the present invention, the active matrix method is preferable to the simple matrix method, and a TFT (Thin Film Transistor) is preferable.
tor), TFD (Thin Film Diode) or MIM (Metal Insulator Met)
al) is more preferred. More preferably, low temperature polysilicon or continuous grain boundary silicon is used for the TFT.

For details, see “Liquid Crystal Device Handbook” edited by Japan Society for the Promotion of Science, 142nd Committee, Nikkan Kogyo Shimbun, “Liquid Crystal Application” by Koji Okano, Baifukan, “Color Liquid Crystal Display” by Shunsuke Kobayashi, industrial books, etc. "Next-generation liquid crystal display technology" Tatsuo Uchida, Industrial Research Committee, "Cutting-edge of liquid crystal display" edited by Young Researchers of Liquid Crystal, Sigma Publishing,
"Liquid crystal: LCD basics and new applications" Described in Liquid Crystal Young Research Group, Sigma Publishing, etc.

[0060]

EXAMPLES [Example 1] (Preparation of Cellulose Triacetate Solution) The following composition was charged in a mixing tank and stirred with heating,
Each component was dissolved to prepare a cellulose triacetate solution.

[0061] ────────────────────────────────────   Cellulose triacetate solution composition ────────────────────────────────────   100 parts by mass of cellulose acetate having a degree of acetylation of 60.9%   Triphenyl phosphate (plasticizer) 8.1 parts by mass   Biphenyl diphenyl phosphate (plasticizer) 3.6 parts by mass   Methylene chloride (first solvent) 338 parts by mass   Methanol (second solvent) 27 parts by mass ────────────────────────────────────

(Preparation of Retardation Raising Agent Solution) Into another mixing tank, 16 parts by mass of the following retardation increasing agent, 80 parts by mass of methylene chloride and 19 parts by mass of methanol were added, and the mixture was stirred with heating to form a letter. A solution of a foundation enhancer was prepared.

[0063]

[Chemical 1]

(Preparation of Cellulose Triacetate Film) 477 parts by mass of the cellulose triacetate solution was mixed with 52 parts by mass of the retardation increasing agent solution and stirred to prepare a dope. The obtained dope was cast using a band casting machine. The film with the residual solvent amount of 51% by mass was peeled from the band, and stretched at a stretching ratio of 18% using a tenter at a temperature of 130 ° C., the tenter was bent at 45 ° with respect to the stretching direction, and then the width was kept constant. While keeping at 13
After holding at 0 ° C. for 40 seconds, the tenter was removed to produce a long cellulose triacetate film having a slow axis of 45 ° with respect to the film conveying direction (longitudinal direction).

(Measurement of Optical Properties) With respect to the produced cellulose triacetate film, an ellipsometer (M
-150, manufactured by JASCO Corporation, wavelength 550 nm
The Re retardation value and the Rth retardation value were measured. In addition, automatic birefringence meter (KOBRA
The axis deviation angle was measured with -21ADH, Oji Scientific Instruments. Each measurement is performed at 10 points at equal intervals in the width direction.
The average value was calculated. Furthermore, the standard deviation of the slow axis angle was obtained. The results are shown in Table 1 together with the results of Example 2.

(Saponification Treatment of Cellulose Triacetate Film) On the cellulose triacetate film,
1.0 normal potassium hydroxide solution (solvent: IPA / propylene glycol / water = 75/13/12 wt%) #
After coating with 3 bar and heating at 60 ° C for 10 seconds, water is coated with # 1.6 bar on the same surface, and then wash water at 40 ° C 5
00cc / m2 is sprayed from the nozzle, and immediately the cleaning water on the film is blown off with an air knife three times.
It was dried with warm air of 100 ° C. to prepare a cellulose triacetate film whose surface was saponified.

(Formation of Alignment Film) 2.0 g of the following modified polyvinyl alcohol (the number in parentheses is wt%) was dissolved in 36 g of water on one side of a saponified cellulose triacetate film, and 12 g of methanol and glutaraldehyde were dissolved. The coating solution obtained by adding 0.1 g of (crosslinking agent) was applied with a # 14 wire bar coater, dried with hot air of 60 ° C. for 60 seconds, and further with hot air of 90 ° C. for 160 seconds to obtain a roll form. An alignment film was formed on the cellulose triacetate film. Then, in the obtained alignment film, the roll-shaped cellulose triacetate film was conveyed in the longitudinal direction.
The rubbing treatment was performed in parallel with.

[0068]

[Chemical 2]

(Formation of Optically Anisotropic Layer) 38.4 g of the following discotic liquid crystal compound and ethylene oxide-modified trimethylolpropane triacrylate (V # 36) were rubbed on the alignment film parallel to the longitudinal direction.
0, Osaka Organic Chemical Co., Ltd. 4.1 g, Cellulose Acetate Butyrate (CAB551-0.2, Eastman Chemical Co., Ltd.) 0.7 g, Cellulose Acetate Butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.3 g, a photopolymerization initiator (Irgacure 907,
Ciba Geigy Co., Ltd. 1.5 g, sensitizer (Kayacure D)
A coating solution prepared by dissolving 0.5 g of ETX (manufactured by Nippon Kayaku Co., Ltd.) in 102 g of methyl ethyl ketone was applied using a # 3 wire bar. Paste this on a metal frame, 130 ℃
In the constant temperature bath for 2 minutes, the monodomain discotic nematic phase was taken. Then 1 at 130 ° C
The discotic liquid crystal was polymerized by UV irradiation for 1 minute with a 20 W / cm high-pressure mercury lamp, and then allowed to cool to room temperature. In this way, an optically anisotropic layer was formed, and a long optical compensation film was prepared.

[0070]

[Chemical 3]

40 ° C. from the normal line in the plane including the normal line direction, the rubbing direction and the normal line of the produced optical compensation film,
Alternatively, the retardation value in the direction tilted by −40 ° was measured with an ellipsometer. The results are shown in Table 2 together with the results of Example 2.

(Preparation of HAN-type liquid crystal cell) A glass film with an ITO electrode was provided with a polyimide film as an alignment film and subjected to rubbing treatment. Another glass substrate with an ITO electrode was prepared, and a SiO vapor deposition film was provided as an alignment film. The two glass substrates were arranged so that the alignment films face each other, bonded with a cell gap of 4.9 μm, and liquid crystal ZLI1132 (Δn = 0.1396) manufactured by Merck was injected, and HA was used.
An N-type liquid crystal cell was produced. The retardation of the liquid crystal layer of the obtained liquid crystal cell was 674 nm.

(Production of λ / 4 Plate) At room temperature, 120 parts by mass of cellulose triacetate having an average degree of acetylation of 59.5%, 9.4 parts by mass of triphenyl phosphate, 4.8 parts by mass of biphenyldiphenylphosphate, and increase in retardation. 4-n-heptylphenol diester of trans-1,4-cyclohexanedicarboxylic acid as an agent 1.
A solution (dope) was prepared by mixing and dissolving 00 parts by mass, 544 parts by mass of methylene chloride, 99 parts by mass of methanol and 20 parts by mass of n-butanol. The obtained dope is cast on a moving stainless steel band,
It was dried by passing it through the zone at 0 ° C for 1 minute and the zone at 45 ° C for 5 minutes. The residual amount of solvent after drying was 30% by mass. After that, the film was peeled from the band, the winding speed was made higher than the carrying speed of the band, and the film was stretched in the carrying direction at 130 ° C. The direction perpendicular to the stretching direction was allowed to shrink freely. After the drawing, the film was passed through a zone at 120 ° C. for 30 minutes to be dried, and the drawn film was wound up. The residual amount of solvent after stretching was 0.1% by mass.

The thickness of the obtained long roll film is
101 μm, using an ellipsometer (M-150, manufactured by JASCO Corporation), wavelength 450 nm, 550 n
Retardation value (R
e) was measured to be 119 nm and 137, respectively.
nm and 143 nm. The direction of the slow axis was parallel to the transport direction (same as the stretching direction: longitudinal direction).
Further, from the refractive index measurement by the Abbe refractometer and the angle dependence of the retardation, the refractive index nx in the in-plane slow axis direction at a wavelength of 550 nm and the refractive index in the direction perpendicular to the in-plane slow axis. It was 1.6 when the value of (nx-nz) / (nx-ny) was calculated by obtaining ny and the refractive index nz in the thickness direction.

(Production of Polarizing Film) A long PVA film was immersed in an aqueous solution containing 2.0 g / l of iodine and 4.0 g / l of potassium iodide at 25 ° C. for 240 seconds, and 10 g of boric acid was further added.
After dipping in an aqueous solution of 1 / l for 60 seconds at 25 ° C., it is introduced into a tenter stretching machine and stretched 5.3 times to bend the tenter in the stretching direction.
After being dried in an atmosphere of 0 ° C., it was taken out from the tenter and wound up. Water content of PVA film before stretching is 31%
The water content after drying was 1.5%. The difference in transport speed between the left and right tenter clips was less than 0.05%, and the angle between the center line of the film introduced and the center line of the film sent to the next step was 46 °. No wrinkles or film deformation was observed at the tenter exit. The transmission axis direction of the obtained polarizing film was inclined by 45 ° with respect to the transport direction (longitudinal direction) of the tenter.
The transmittance at m was 43.7% and the polarization degree was 99.97%.

(Preparation of Circular Polarizing Plate) On a cellulose triacetate film (Fujitac TD80U, manufactured by Fuji Photo Film Co., Ltd.), a heat-crosslinkable fluoropolymer (JN-
7228, solid content concentration 6%, manufactured by JSR Corporation, 210 g
Silica sol (MEK-ST, average particle size 10-20n
m, solid content concentration 30 wt%, manufactured by Nissan Chemical Co., Ltd.) 18
g, and 200 g of methyl ethyl ketone were added and stirred, and then the coating liquid for low refractive index layer filtered with a polypropylene filter having a pore size of 1 μm was applied with a bar coater, dried at 80 ° C. for 5 minutes, and then heated at 120 ° C. for 10 minutes. The polymer was cross-linked to form a low refractive index layer having a thickness of 0.1 μm to prepare an antireflection film. The antireflection film and the λ / 4 plate were dipped in a 1.5N NaOH aqueous solution at 55 ° C for 1 minute to saponify both surfaces, thoroughly washed with dilute sulfuric acid and water, and dried. It was applied to a thickness of about 30 μm, stuck on both sides of the polarizing film by roll-to-roll, and dried at 80 ° C. to prepare a long circular polarizing plate. The film thickness of this circularly polarizing plate was about 241 μm.

(Production of HAN Alignment Mode Reflective Liquid Crystal Display Device) The respective elements produced as described above were assembled to produce a HAN alignment mode reflective liquid crystal display device having the following constitution.

──────────────────────────────────── Circular polarizing plate 1. Anti-reflection film 2. Polarizing film (PVA / I ₂ ) 3. Retardation plate (λ / 4 plate) ──────────────────────────────────── Optical compensation film 4. Transparent support (cellulose triacetate film) 5. Optically anisotropic layer (discotic liquid crystal layer) ───────────────────────────────────── 6. HAN type liquid crystal cell ──────────────────────────────────── 7. Reflector ────────────────────────────────────

The produced HAN type liquid crystal cell (6) was attached to a reflector (7) used in a commercially available reflection type liquid crystal display device, and the produced long-shaped (optical anisotropy The optical compensation film (consisting of the layer (5) and the transparent support (4)) is cut so that the rubbing direction of the liquid crystal cell and the rubbing direction of the transparent support of the optical compensation film are antiparallel to each other, thereby performing the optical compensation. Acrylic pressure sensitive adhesive is attached to the cellulose triacetate side of the film and the films are bonded together, and further on top of that (the antireflection film (1), the polarizing film (2) and the λ
The same acrylic adhesive is attached to the λ / 4 plate side of the circularly polarizing plate (comprising the / 4 plate (3)) so that the slow axis of the λ / 4 plate of the circularly polarizing plate is parallel to the rubbing direction of the liquid crystal cell. The HAN alignment mode liquid crystal display device was produced by laminating the layers.

A white display voltage of 2 V and a black display voltage of 6 V were applied to the liquid crystal cell of this liquid crystal display device, and a measuring instrument (EZ-Contras
t 160D, manufactured by ELDIM) was used to measure the front contrast ratio. Furthermore, the viewing angle (angle range where the contrast ratio is 5 or more) in the left-right direction (direction orthogonal to the rubbing direction of the cell) was examined. The results are shown in Table 3 together with the results of Example 2.

Example 2 (Preparation of Cellulose Triacetate Film) Cellulose triacetate powder (average size: 2 mm) was gradually added to a solution prepared by preliminarily mixing the following solvents with good stirring.

[0082] ────────────────────────────────────   Cellulose acetate solution composition ────────────────────────────────────   100 parts by mass of cellulose triacetate having an acetylation degree of 60.5%   Triphenyl phosphate (plasticizer) 6.8 parts by mass   Biphenyl diphenyl phosphate (plasticizer) 4.9 parts by mass   Methyl acetate (first solvent) 240 parts by mass   Cyclohexanone (second solvent) 100 parts by mass   25 parts by mass of methanol (third solvent)   Ethanol (4th solvent) 25 parts by mass   Silica (particle size 20 nm) 0.5 parts by mass   Retardation increasing agent used in Example 1 6.7 parts by mass ────────────────────────────────────

After the addition, the mixture was left at room temperature (25 ° C.) for 3 hours. The obtained heterogeneous gel solution was cooled at -70 ° C for 6 hours, then heated to 50 ° C and stirred to obtain a dope.
Thereafter, in the same manner as in Example 1, a cellulose triacetate film in which the slow axis was inclined by 45 ° with respect to the conveying direction of the long film was prepared, and the optical characteristics were measured. The results are shown in Table 1.

[0084]

[Table 1]                                 Table 1 ────────────────────────────────────   Transparent support Re value Rth value Standard deviation of slow axis angle ────────────────────────────────────   Example 1 37 nm 218 nm 1.2 °   Example 2 39 nm 221 nm 1.8 ° ────────────────────────────────────

(Saponification Treatment of Cellulose Acetate Film) One side of the cellulose acetate film is set to 3.8.
It was laminated with a polyethylene terephthalate film having a thickness of μm. This was immersed in a 1.5 N aqueous sodium hydroxide solution at 55 ° C. for 2 minutes. It was washed in a water-washing bath at room temperature and neutralized at 30 ° C. with 0.1 N sulfuric acid. Wash again in a water bath at room temperature for another 10
It was dried with hot air at 0 ° C. In this way, one surface of the cellulose acetate film was saponified.

(Formation of Alignment Film) On the saponified surface of the cellulose triacetate film, the same alignment film as in Example 1 was provided and the same rubbing treatment was performed.

(Formation of Optically Anisotropic Layer) On the rubbed alignment film, the discotic liquid crystal 4 used in Example 1 was formed.
1.0 g, ethylene oxide modified trimethylolpropane triacrylate (V # 360, Osaka Organic Chemical Co., Ltd.) 4.0 g, cellulose acetate butyrate (CAB551-0.2, Eastman Chemical Co., Ltd.)
0.9 g, cellulose acetate butyrate (CAB5
31-1, Eastman Chemical Co., Ltd.) 0.2 g, photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.)
A coating solution prepared by dissolving 1.5 g and 0.5 g of a sensitizer (Kayakyu DETX, manufactured by Nippon Kayaku Co., Ltd.) in 102 g of methyl ethyl ketone was applied with a # 3 wire bar. This was attached to a metal frame and heated in a constant temperature bath at 130 ° C. for 2 minutes to form a monodomain of a discotic nematic phase. Next, UV irradiation was performed at 130 ° C. for 1 minute using a 120 W / cm high pressure mercury lamp to polymerize the discotic liquid crystal. Then, it stood to cool to room temperature.

40 ° C. from the normal direction in the plane including the normal direction, the rubbing direction and the normal line of the produced optical compensation film.
Alternatively, the retardation value in the direction inclined by -40 ° was measured with an ellipsometer. The results are shown in Table 2.

[0089]

[Table 2]                                 Table 2 ────────────────────────────────────   Optical Compensation Sheet Re (0 °) Re (-40 °) Re (40 °) ────────────────────────────────────     Example 1 37 nm 42 nm 81 nm     Example 2 39 nm 44 nm 85 nm ────────────────────────────────────

(Preparation of elliptically polarizing plate) The antireflection film prepared in Example 1 and the above optical compensation film were prepared at 55 ° C.
After dipping in 1.5N NaOH aqueous solution for 1 minute to saponify both sides, thoroughly washing with dilute sulfuric acid and water, and drying, a polyvinyl alcohol adhesive is applied to each cellulose triacetate side to a thickness of about 30 μ. The polarizing film prepared in 1 was pasted on both sides by roll-to-roll and further dried at 80 ° C. to prepare a long elliptical polarizing plate. The film thickness of this circularly polarizing plate was about 241 μm.

(Production of Bend Alignment Liquid Crystal Cell) A polyimide film was provided as an alignment film on a glass substrate having an ITO electrode, and the alignment film was rubbed. A polyimide film was provided as an alignment film on the other glass substrate, and a rubbing treatment was performed. The two glass substrates thus obtained were opposed to each other in an arrangement such that the rubbing directions were parallel to each other, and the cell gap was set to 10 μm. A liquid crystal compound having 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 liquid crystal cell thus obtained had a retardation of 698 nm.

(Production of OCB Alignment Mode Transmission Type Liquid Crystal Display Device) The respective elements produced as described above were assembled to produce an OCB alignment mode transmission type liquid crystal display device having the following constitution.

──────────────────────────────────── Elliptical polarizing plate 11. Anti-reflection film 12. Polarizing film (PVA / I ₂ ) 13. Transparent support (cellulose triacetate film) 14. Optically anisotropic layer (discotic liquid crystal layer) ───────────────────────────────────── 15. Bend alignment liquid crystal cell (OCB mode) ──────────────────────────────────── Elliptical polarizing plate 14. Optically anisotropic layer (discotic liquid crystal layer) 13. Transparent support (cellulose triacetate film) 12. Polarizing film (PVA / I ₂ ) 11. Anti-reflection film ──────────────────────────────────── Backlight

On both sides of the bend-aligned liquid crystal cell (15), the rubbing direction of the liquid crystal cell and the rubbing direction of the transparent support of the optical compensation film (consisting of the transparent support (13) and the optically anisotropic layer (14)). So that they are antiparallel to each other (the antireflection film (11), the polarizing film (12), the transparent support (1
3), an elliptically polarizing plate (consisting of the optically anisotropic layer (14)) is cut, an acrylic pressure sensitive adhesive is attached to the optically anisotropic layer side and bonded, and a backlight unit is attached to one side of the liquid crystal cell. A transmissive liquid crystal cell was prepared. A white display voltage of 2 V and a black display voltage of 6 V were applied to the liquid crystal cell of the manufactured liquid crystal display device, and a measuring instrument (EZ-Contrast 160D, manufactured by ELDIM)
Was used to measure the front contrast ratio as a transmissive liquid crystal display device. Further, the viewing angle (angle range where the contrast ratio is 10 or more) in the left-right direction (direction orthogonal to the rubbing direction of the cell) was examined. The results are shown in Table 3.

[0095]

[Table 3]                                 Table 3 ────────────────────────────────────   Liquid crystal display device Front contrast ratio Viewing angle ────────────────────────────────────     Example 1 15 120 °     Example 2 12 160 ° ────────────────────────────────────

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H049 BA02 BA03 BA04 BA07 BA42                       BB03 BB43 BB49 BC04 BC22                 2H091 FA08X FA08Z FA11X FC16                       HA06 LA12                 4F100 AJ06A AJ06B AK21C AK25B                       AL05B AL06C AR00B AT00A                       BA02 BA10A BA10B BA22                       GB41 JA11B JN00A JN00B                       JN01A JN10

Claims (4)

[Claims] 1. An optical compensation film having an optically anisotropic transparent support having a longitudinal direction and an optically anisotropic layer in which the orientation of a discotic liquid crystalline compound is fixed,
An optical compensation film, wherein the slow axis of the optically anisotropic transparent support exists in a direction that is neither substantially parallel nor perpendicular to the longitudinal direction. 2. A polarizing film having a longitudinal direction and an optically anisotropic transparent support having a longitudinal direction are arranged so that their longitudinal directions are parallel to each other, and the discotic liquid crystal compound is aligned. An elliptically polarizing plate having an optically anisotropic layer in which is fixed, wherein the transmission axis of the polarizing film exists in a direction that is not substantially parallel or perpendicular to the longitudinal direction,
The slow axis of the optically anisotropic transparent support exists in a direction that is neither substantially parallel nor perpendicular to the longitudinal direction, and the transmission axis of the polarizing film and the slow phase of the optically anisotropic transparent support are present. An elliptically polarizing plate characterized in that its axis is substantially parallel. 3. A liquid crystal display device having a liquid crystal cell, at least one polarizing plate, and an optical compensation film arranged between the liquid crystal cell and the polarizing plate, wherein the optical compensation film is as set forth in claim 1. A liquid crystal display device, which is cut from an optical compensation film. 4. A liquid crystal display device having a liquid crystal cell and an elliptically polarizing plate, wherein the elliptically polarizing plate is cut from the elliptically polarizing plate according to claim 2.