JP2000304932A - Optical compensation sheet, elliptical polarizing plate, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make effectively and optically compensable a liquid crystal cell by aligning rodlike liquid crystal molecules in a state having a specified average tilt angle of the major axial direction of the rodlike liquid crystal molecules and the face of a transparent supporting body. SOLUTION: A transmission type liquid crystal display device as an example consists of, in order from the back light BL side, a transparent protective film 1a, a polarizing film 2a, transparent supporting body 3a, an optical anisotropic layer 4a, the lower substrate 5a of a liquid crystal cell, rodlike liquid crystal molecules 6, the upper substrate 5b of the liquid crystal cell, an optical anisotropic layer 4b, a transparent supporting body 3b, a polarizing film 2b, and a transparent protective film 1b. The transparent supporting body and optical anisotropic layer (3a to 4a, 4b to 3b) form an optical compensation sheet, and the transparent protective film, polarizing film, transparent supporting body and optical anisotropic layer (1a to 4a, 4b to 1b) form an elliptical polarizing plate. In this case, the optical anisotropic layers 4a, 4b consist of rodlike liquid crystal molecules 6. The rodlike liquid crystal molecules 6 are aligned at <5 deg. average tilt angle between the major axial direction of the rodlike liquid crystal molecules 6 and the faces of the transparent supporting bodies 3a, 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical compensatory sheet having an optically anisotropic layer formed of liquid crystal molecules, and an elliptically polarizing plate and a liquid crystal display using the same.

[0002]

2. Description of the Related Art A liquid crystal display device comprises a liquid crystal cell, a polarizing element, and an optical compensation sheet (retardation plate). In a transmission type liquid crystal display device, two polarizing elements are attached to both sides of a liquid crystal cell, and one or two optical compensation sheets are arranged between the liquid crystal cell and the polarizing element. In a reflection type liquid crystal display device, a reflection plate, a liquid crystal cell, one optical compensation sheet, and one polarization element are arranged in this order. The liquid crystal cell includes rod-like liquid crystal molecules, two substrates for enclosing the same, and an electrode layer for applying a voltage to the rod-like liquid crystal molecules. In the liquid crystal cell, the alignment state of the rod-like liquid crystal molecules is different. For the transmission type, TN (Twisted Nematic) and IPS (In-Plane Sw) are used.
itching), FLC (Ferroelectric Liquid Crysta)
l), OCB (Optically Compensatory Bend), STN
(Supper Twisted Nematic), VA (Vertically Align)
ed), ECB (Electrically Controlled Birefringenc)
e), TN, HAN (Hybrid Align)
Various display modes such as ed Nematic) and GH (Guest-Host) have been proposed.

[0003] Optical compensatory sheets are used in various liquid crystal display devices in order to eliminate coloring of images and to increase the viewing angle. As the optical compensation sheet, a stretched birefringent polymer film has been conventionally used. It has been proposed to use an optical compensatory sheet having an optically anisotropic layer formed of liquid crystal molecules on a transparent support, instead of the optical compensatory sheet made of a stretched birefringent film. Since liquid crystal molecules have various alignment forms, it has become possible to realize optical properties that cannot be obtained by a conventional stretched birefringent polymer film by using liquid crystal molecules.

[0004] The optical properties of the optical compensatory sheet are determined according to the optical properties of the liquid crystal cell, specifically, the above-mentioned difference in display mode. When liquid crystal molecules are used, an optical compensatory sheet having various optical properties corresponding to various display modes of a liquid crystal cell can be manufactured. As an optical compensation sheet using liquid crystal molecules, ones corresponding to various display modes have already been proposed. For example, an optical compensation sheet for a TN mode liquid crystal cell is disclosed in JP-A-6-214116.
And U.S. Pat. Nos. 5,583,679 and 5,646,703.
And German Patent Publication No. 391620A1. Further, an optical compensation sheet for a liquid crystal cell of IPS mode or FLC mode is disclosed in Japanese Patent Application Laid-Open No. H10-54982.
There is a description in the publication. In addition, OCB mode or HA
An optical compensation sheet for an N-mode liquid crystal cell is disclosed in US Pat.
05253 and International Patent Application WO 96/37804
No. is described in each specification. Furthermore, an optical compensatory sheet for a liquid crystal cell of the STN mode is disclosed in JP-A-9-26572.
There is a description in the publication. An optical compensation sheet for a VA mode liquid crystal cell is described in Japanese Patent No. 2866372.

[0005]

By using liquid crystal molecules instead of the conventional stretched birefringent polymer film, it has become possible to optically compensate the liquid crystal cell more accurately than before. However, according to the study of the present inventor, a liquid crystal cell (V
A mode, OCB mode, and HAN mode), the conventional optical compensation sheet has not effectively optically compensated. An object of the present invention is to provide an optical compensatory sheet capable of effectively optically compensating a liquid crystal cell having a large number of rod-like liquid crystal molecules oriented substantially vertically.

[0006]

The object of the present invention is to provide the following optical compensation sheets (1) to (8), (9), (1)
This was achieved by the elliptically polarizing plate of 0) and the liquid crystal display device of the following (11). (1) An optical compensation sheet having an optically anisotropic layer formed from a transparent support and rod-like liquid crystal molecules, wherein the average tilt angle between the major axis direction of the rod-like liquid crystal molecules and the transparent support surface is 5 An optical compensatory sheet characterized in that rod-like liquid crystalline molecules are oriented in a state of less than ゜. (2) The optical compensation sheet according to (1), wherein the transparent support has optical uniaxiality or optical biaxiality. (3) The slow axis in the plane of the transparent support is substantially parallel or orthogonal to the average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface ( The optical compensation sheet according to 2).

(4) It further has a second optically anisotropic layer formed of rod-like liquid crystalline molecules, and the second optically anisotropic layer also has a relationship between the major axis direction of the rod-like liquid crystalline molecules and the surface of the transparent support. The optical compensatory sheet according to (1), wherein the rod-like liquid crystalline molecules are oriented in a state where the average tilt angle between them is less than 5 °. (5) The optical compensation sheet according to (4), wherein the optically anisotropic layer and the second optically anisotropic layer are provided on the same side of the transparent support. (6) The optical compensation sheet according to (4), wherein the second optically anisotropic layer, the transparent support, and the optically anisotropic layer are laminated in this order. (7) The average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystal molecules of the optically anisotropic layer onto the surface of the transparent support and the major axis direction of the rod-like liquid crystal molecules of the second optically anisotropic layer. The optical compensation sheet according to (4), wherein an average direction of a line obtained by projecting the light on the transparent support surface is substantially orthogonal. (8) The average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystal molecules of the optically anisotropic layer onto the transparent support surface and the major axis direction of the rod-like liquid crystal molecules of the second optically anisotropic layer (4) The optical compensatory sheet according to (4), wherein an average direction of a line obtained by projecting the transparent support surface intersects at an angle of 5 ° to 85 °.

(9) An elliptically polarizing plate having a transparent support, an optically anisotropic layer formed of rod-like liquid crystal molecules, a polarizing film and a transparent protective film, wherein the long axis direction of the rod-like liquid crystal molecules and the transparent support An elliptically polarizing plate, wherein rod-like liquid crystal molecules are oriented in a state where the average inclination angle with respect to the body surface is less than 5 °. (10) The in-plane transmission axis of the polarizing film and the average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules of the optically anisotropic layer onto the transparent support surface are substantially parallel or orthogonal. The elliptically polarizing plate according to (9). (11) A liquid crystal display device comprising a VA mode liquid crystal cell and two polarizing elements disposed on both sides of the VA mode, wherein at least one of the polarizing elements is formed of a transparent support and a rod-shaped liquid crystal molecule. An elliptically polarizing plate having an isotropic layer, a polarizing film and a transparent protective film, wherein the rod-like liquid crystal molecules are oriented in a state where the average tilt angle between the major axis direction of the rod-like liquid crystal molecules and the transparent support surface is less than 5 °. A liquid crystal display device comprising:

[0009]

As a result of the research, the present inventors have found that the optical liquid crystal molecules in which the rod-like liquid crystal molecules are oriented in a state where the average tilt angle between the major axis direction of the rod-like liquid crystal molecules and the transparent support surface is less than 5 °. By providing the isotropic layer on the optical compensation sheet, it was possible to effectively optically compensate a liquid crystal cell having a large number of rod-like liquid crystal molecules oriented substantially vertically. In the conventional technology, an optical compensation sheet in which discotic liquid crystal molecules or rod-like liquid crystal molecules are obliquely aligned is used to correspond to a liquid crystal cell having a large number of rod-like liquid crystal molecules that are substantially vertically aligned. Compensation). However, as a result of the study of the present inventor, rod-like liquid crystal molecules that are aligned with an average tilt angle of less than 5 ° are effective for rod-like liquid crystal molecules that are substantially vertically aligned. It has been found. As a result, by using the optical compensation sheet of the present invention, optical compensation can be effectively performed on a liquid crystal cell having a large number of rod-like liquid crystal molecules oriented substantially vertically, such as a VA mode.

[0010]

FIG. 1 is a schematic diagram showing the basic structure of a transmission type liquid crystal display device. In the transmission type liquid crystal display device shown in FIG. 1A, a transparent protective film (1a), a polarizing film (2a), a transparent support (3a), an optically anisotropic layer ( 4a), the lower substrate of the liquid crystal cell (5a), the rod-like liquid crystalline molecules (6), the upper substrate of the liquid crystal cell (5b), the optically anisotropic layer (4b), the transparent support (3
b), a polarizing film (2b), and a transparent protective film (1b). The transparent support and the optically anisotropic layers (3a to 4a and 4b to 3b) constitute an optical compensation sheet. And
The transparent protective film, the polarizing film, the transparent support and the optically anisotropic layers (1a to 4a and 4b to 1b) constitute an elliptically polarizing plate. The transmission type liquid crystal display device shown in FIG. 1B includes, in order from the backlight (BL) side, a transparent protective film (1a), a polarizing film (2a), a transparent support (3a), and an optically anisotropic layer ( 4
a), lower substrate of liquid crystal cell (5a), rod-like liquid crystal molecules (6), upper substrate of liquid crystal cell (5b), transparent protective film (1)
b), a polarizing film (2b), and a transparent protective film (1c). The transparent support and the optically anisotropic layer (3a to 4a) constitute an optical compensation sheet. The transparent protective film, the polarizing film, the transparent support, and the optically anisotropic layers (1a to 4a) constitute an elliptically polarizing plate.

The transmission type liquid crystal display device shown in FIG. 1C has a transparent protective film (1) in order from the backlight (BL) side.
a), polarizing film (2a), transparent protective film (1b), lower substrate of liquid crystal cell (5a), rod-like liquid crystal molecules (6), upper substrate of liquid crystal cell (5b), optically anisotropic layer (4b) , Transparent support (3b), polarizing film (2b), and transparent protective film (1c)
Consists of Transparent support and optically anisotropic layer (4b-3
b) constitutes the optical compensation sheet. Then, a transparent protective film, a polarizing film, a transparent support and an optically anisotropic layer (4b to 1b)
c) constitutes an elliptically polarizing plate. FIG. 2 is a schematic diagram showing a basic configuration of a reflection type liquid crystal display device. The reflection type liquid crystal display device shown in FIG. 2 includes, in order from the bottom, a lower substrate (5a) of a liquid crystal cell, a reflector (RP), rod-like liquid crystal molecules (6), an upper substrate (5b) of a liquid crystal cell, and an optically anisotropic liquid crystal cell. A transparent layer (4), a transparent support (3), a polarizing film (2), and a transparent protective film (1). The transparent support and the optically anisotropic layer (4 to 3) constitute an optical compensation sheet. The transparent protective film, the polarizing film, the transparent support, and the optically anisotropic layer (4-1) constitute an elliptically polarizing plate.

In FIGS. 1 and 2, the arrangement order of the optically anisotropic layer (4) and the transparent support (3) may be reversed. Further, a second optically anisotropic layer can be further added to the optical compensation sheet or the elliptically polarizing plate shown in FIGS. There is no particular limitation on the arrangement of the second optically anisotropic layer. Therefore, (polarizing film) shown in FIGS. 1 and 2 → A → transparent support → B → optically anisotropic layer → C →
The second optically anisotropic layer can be provided at any position of A, B and C in the (liquid crystal cell) stacking order.

[Optical Anisotropic Layer] The optically anisotropic layer is formed from rod-like liquid crystalline molecules. The rod-like liquid crystal molecules have an average inclination angle of 5 between the major axis direction of the rod-like liquid crystal molecules and the transparent support surface.
Orient in the state of less than ゜. It is preferable to adjust the retardation of the entire optical compensatory sheet according to the optical anisotropy of the optically anisotropic layer. The in-plane retardation (Re) of the entire optical compensation sheet is preferably from 20 to 200 nm, more preferably from 20 to 100 nm, and most preferably from 20 to 70 nm. The retardation (Rth) in the thickness direction of the entire optical compensation sheet is preferably from 70 to 500 nm, more preferably from 70 to 300 nm, and more preferably from 70 to 300 nm.
More preferably, it is from 200 to 200 nm. The in-plane retardation (Re) and the retardation in the thickness direction (Rth) of the optical compensation sheet are defined by the following equations, respectively. Re = (nx−ny) × d Rth = [{(nx + ny) / 2} −nz] × d where nx and ny are in-plane refractive indices of the optical compensation sheet, and nz is the thickness of the optical compensation sheet. And d is the thickness of the optical compensatory sheet.

By combining an optically anisotropic layer with a transparent support having optical uniaxiality or optical biaxiality,
The retardation of the entire optical compensation sheet can be adjusted. The transparent support having optical uniaxiality or optical biaxiality will be described later. Further, a second optically anisotropic layer may be provided. The combined use of the optically anisotropic layer and the second optically anisotropic layer is particularly effective for adjusting the in-plane retardation (Re). Further, a second optically anisotropic layer can be provided for the purpose of controlling the wavelength dispersion of the retardation.
The second optically anisotropic layer is also preferably formed from rod-like liquid crystalline molecules, like the optically anisotropic layer. The rod-like liquid crystalline molecules of the second optically anisotropic layer are also preferably oriented with the average tilt angle between the major axis direction of the rod-like liquid crystalline molecules and the transparent support surface being less than 5 °. The optically anisotropic layer and the second optically anisotropic layer can be provided on the same side of the transparent support. Also,
The optically anisotropic layer and the second optically anisotropic layer are provided on opposite sides of the transparent support, in other words, the second optically anisotropic layer, the transparent support and the optically anisotropic layer are laminated in this order. You can also. The average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules of the optically anisotropic layer onto the transparent support surface and the major axis direction of the rod-like liquid crystalline molecules of the second optically anisotropic layer are defined as the transparent support surface. It is preferable that the average direction of the line obtained by projecting the image is substantially orthogonal. The average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystal molecules of the optically anisotropic layer onto the transparent support surface and the major axis direction of the rod-like liquid crystal molecules of the second optically anisotropic layer are transparent. The average direction of the line obtained by projecting on the support surface is
Intersecting at an angle of 5 ° to 85 ° is also possible.

The average direction of a line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules of the optically anisotropic layer onto the surface of the transparent support has a transparent support (which has an optical uniaxial property or an optical biaxial property). It is preferable to arrange them so as to be substantially parallel or orthogonal to the in-plane slow axis. In this specification, substantially parallel or orthogonal means that a difference in angle from a strictly parallel or orthogonal state is less than 10 °. The angle difference is preferably less than 8 °, more preferably less than 6 °, even more preferably less than 4 °, even more preferably less than 2 °, and less than 1 °. Is most preferred. Hereinafter, the rod-shaped liquid crystalline molecules used for the optically anisotropic layer and the second optically anisotropic layer will be further described. The rod-like liquid crystal molecules are preferably fixed in an aligned state. Although the alignment state can be fixed using a polymer binder, it is preferable to fix the alignment state by a polymerization reaction.

Depending on the display mode of the liquid crystal cell, the rod-like liquid crystal molecules may be cholesterically aligned. When the rod-like liquid crystal molecules are cholesterically aligned, the selective reflection region is preferably outside the visible region. As the rod-like liquid crystal molecules, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoates,
Cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitrile are preferably used. The rod-like liquid crystal molecules also include metal complexes. Further, a liquid crystal polymer containing a rod-like liquid crystal molecule in a repeating unit can also be used as the rod-like liquid crystal molecule. In other words,
The rod-like liquid crystal molecules may be bonded to a (liquid crystal) polymer. Regarding rod-shaped liquid crystalline molecules, see Quarterly Chemistry Review No. 22
The description is given in Chapters 4, 7 and 11 of the Volume Chemistry of Liquid Crystals (1994) edited by the Chemical Society of Japan and in Chapter 3 of the 142nd Committee of the Japan Society for the Promotion of Liquid Crystals. The birefringence of the rod-like liquid crystal molecules is 0.001 to 0.5.
7 is preferred. The rod-like liquid crystal molecules preferably have a polymerizable group. Examples of the polymerizable group (Q) are shown below.

[0017]

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The polymerizable group (Q) is an unsaturated polymerizable group (Q1
To Q7), an epoxy group (Q8) or an aziridinyl group (Q9), more preferably an unsaturated polymerizable group, and more preferably an ethylenically unsaturated polymerizable group (Q
1 to Q6) are most preferred. The rod-like liquid crystal molecules preferably have a molecular structure that is substantially symmetric with respect to the minor axis direction. For that purpose, it is preferable to have a polymerizable group at both ends of the rod-shaped molecular structure. Hereinafter, examples of rod-like liquid crystal molecules will be described.

[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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The optically anisotropic layer is composed of rod-like liquid crystal molecules or the following polymerizable initiators and optional additives (eg, plasticizer, monomer, surfactant, cellulose ester, 1,3,5-
It is formed by applying a liquid crystal composition (coating solution) containing a triazine compound and a chiral agent on the alignment film. As the solvent used for preparing the liquid crystal composition, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N,
N-dimethylformamide), sulfoxide (eg, dimethylsulfoxide), heterocyclic compound (eg, pyridine), hydrocarbon (eg, benzene, hexane), alkyl halide (eg, chloroform, dichloromethane), ester (eg, methyl acetate, Butyl acetate), ketones (eg, acetone, methyl ethyl ketone), and ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The liquid crystal composition can be applied by a known method (eg, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method).

The polymerization reaction of the rod-like liquid crystal molecules includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Photopolymerization reactions are preferred. Examples of photopolymerization initiators include α-carbonyl compounds (U.S. Pat.
Nos. 661 and 2367670), acyloin ethers (described in US Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in US Pat. No. 2,722,512), and polynuclear quinone compounds (described in US Pat. Patents 3046127 and 2951758), triarylimidazole dimer and p
-Combination with aminophenyl ketone (US Patent 35
No. 49367), acridine and phenazine compounds (described in JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (described in U.S. Pat. No. 4,221,970). The amount of the photopolymerization initiator used is 0.1% of the solid content of the coating solution.
The content is preferably from 01 to 20% by weight, more preferably from 0.5 to 5% by weight. Light irradiation for the polymerization of the rod-like liquid crystalline molecules is preferably performed using ultraviolet light. The irradiation energy is 20 mJ / cm ^{2 to} 50 J /
cm ² , preferably 100 to 800 mJ /
cm ² is more preferable. Light irradiation may be performed under heating conditions to promote the photopolymerization reaction. The thickness of the optically anisotropic layer (independently when a plurality of optically anisotropic layers are provided) is preferably from 0.1 to 20 μm, more preferably from 0.5 to 15 μm, Most preferably, it is 1 to 10 μm.

[Transparent Support] As the transparent support of the optical compensation sheet, a glass plate or a polymer film, preferably a polymer film is used. Transparent support means that the light transmittance is 80% or more. Generally, an optically isotropic polymer film is used as a transparent support. Optical isotropic, specifically,
The in-plane retardation (Re) is preferably less than 10 nm, more preferably less than 5 nm. In the optically isotropic transparent support, the retardation (Rth) in the thickness direction is preferably less than 10 nm, more preferably less than 5 nm. The in-plane retardation (Re) and the thickness direction retardation (Rth) of the transparent support are defined by the following formulas. Re = (nx−ny) × d Rth = [{(nx + ny) / 2} −nz] × d where nx and ny are in-plane refractive indices of the transparent support, and nz is the thickness of the transparent support. Is the refractive index in the direction, and d is the thickness of the transparent support.

Depending on the type of liquid crystal display mode, an optically anisotropic polymer film may be used as the transparent support. That is, in some cases, the optical anisotropy of the optically anisotropic layer is added to the optical anisotropy of the transparent support to correspond to the optical anisotropy of the liquid crystal cell (optical compensation). In such a case, the transparent support preferably has optical uniaxiality or optical biaxiality. In the case of an optically uniaxial support, even if it is optically positive (the refractive index in the optical axis direction is larger than the refractive index in the direction perpendicular to the optical axis), it is negative (the refractive index in the optical axis direction is (Smaller than the refractive index in the vertical direction).
In the case of an optically biaxial support, the refractive indices nx, ny of the above formula
And nz all have different values (nx ≠ ny ≠ nz). In-plane retardation of optically anisotropic transparent support (R
e) is preferably from 10 to 1000 nm,
More preferably, the thickness is 15 to 300 nm,
Most preferably, it is from 200 to 200 nm. The retardation (Rth) in the thickness direction of the optically anisotropic transparent support is
It is preferably from 10 to 1000 nm, more preferably from 15 to 300 nm, and from 20 to 200 nm.
More preferably, it is nm.

The material for forming the transparent support is determined depending on whether it is an optically isotropic support or an optically anisotropic support. In the case of an optically isotropic support, glass or cellulose ester is generally used. In the case of an optically anisotropic support, a synthetic polymer (eg, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, norbornene resin) is generally used. However, due to the use of (1) the use of a retardation increasing agent, (2) the reduction of the acetylation degree of cellulose acetate, or (3) the production of a film by a cooling dissolution method described in European Patent No. 0911656 A2, an optical difference is caused. An isotropic (high retardation) cellulose ester film can also be produced. The transparent support made of a polymer film is preferably formed by a solvent casting method.

In order to obtain an optically anisotropic transparent support, it is preferable to carry out a stretching treatment on the polymer film.
In the case of producing an optically uniaxial support, ordinary uniaxial stretching or biaxial stretching may be performed. When producing an optically biaxial support, it is preferable to carry out an unbalanced biaxial stretching process. In unbalanced biaxial stretching, a polymer film is stretched in a certain direction at a certain magnification (for example, 3
To 100%, preferably 5 to 30%), and a higher magnification (eg, 6 to 200%) in the direction perpendicular thereto.
%, Preferably 10 to 90%). The bidirectional stretching may be performed simultaneously. It is preferable that the stretching direction (the direction in which the stretching ratio is high in unbalanced biaxial stretching) and the in-plane slow axis of the stretched film be substantially the same. The angle between the stretching direction and the slow axis is preferably less than 10 °, more preferably less than 5 °, and most preferably less than 3 °.

The thickness of the transparent support is 10 to 500 μm
Is more preferable, and more preferably 50 to 200 μm. To improve the adhesion between the transparent support and the layer provided thereon (adhesive layer, alignment film or optically anisotropic layer), the transparent support is subjected to a surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet light ( UV) treatment, flame treatment)
May be implemented. An ultraviolet absorber may be added to the transparent support. An adhesive layer (undercoat layer) may be provided on the transparent support. Regarding the adhesive layer, see JP-A-7-33343.
No. 3 discloses this. The thickness of the adhesive layer is 0.1 to 2
μm, more preferably 0.2 to 1 μm.

[Alignment Film] The alignment film is formed by rubbing an organic compound (preferably a polymer), obliquely depositing an inorganic compound, forming a layer having microgrooves, or by using a Langmuir-Blodgett method (LB film). (Eg, ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearylate). In addition, the application of an electric field,
There is also known an alignment film in which an alignment function is generated by applying a magnetic field or irradiating light. An alignment film formed by rubbing a polymer is particularly preferable. The rubbing treatment is performed by rubbing the surface of the polymer layer several times with paper or cloth in a certain direction. In the present invention, since the rod-like liquid crystalline molecules are aligned at an average inclination angle of less than 5 °, a polymer that does not lower the surface energy of the alignment film (a normal polymer for alignment film)
It is preferable to use The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm. The optically anisotropic layer may be transferred onto a transparent support after the rod-shaped liquid crystalline molecules of the optically anisotropic layer are aligned using an alignment film. The rod-like liquid crystal molecules fixed in the alignment state can maintain the alignment state without the alignment film. In the present invention, since the rod-like liquid crystal molecules are oriented in a state where the average tilt angle is less than 5 °,
No rubbing treatment is required, and in some cases, an alignment film is not required. However, for the purpose of improving the adhesion between the liquid crystal molecules and the transparent support, an alignment film that forms a chemical bond with the liquid crystal molecules at the interface (described in JP-A-9-152509)
May be used. When an alignment film is used for the purpose of improving adhesion, rubbing treatment may not be performed. When two types of optically anisotropic layers are provided on the same side of the transparent support, the optically anisotropic layer formed on the transparent support may function as an alignment film of the optically anisotropic layer provided thereon. It is possible.

[Polarizing Film] As the polarizing film, an iodine-based polarizing film,
There are a dye-based polarizing film using a dichroic dye and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. The in-plane transmission axis of the polarizing film is preferably arranged so as to be substantially parallel or orthogonal to the average direction of a line obtained by projecting the major axis direction of the rod-like liquid crystal molecules onto the transparent support surface.

[Transparent Protective Film] As the transparent protective film, a transparent polymer film is used. That the protective film is transparent means that the light transmittance is 80% or more. As the transparent protective film, a cellulose ester film, preferably a triacetyl cellulose film, is generally used. The cellulose ester film is preferably formed by a solvent casting method. The thickness of the transparent protective film is preferably 20 to 500 μm,
More preferably, it is 0 to 200 μm.

[Liquid Crystal Display Device] The present invention can be applied to liquid crystal cells of various display modes. As described above, the optical compensation sheet using liquid crystal molecules is formed of a TN (Twisted Nemati).
c), IPS (In-Plane Switching), FLC (Ferroel
ectric Liquid Crystal), OCB (Optically Compensa)
tory Bend), STN (Supper Twisted Nematic), V
A (Vertically Aligned), ECB (Electrically Cont
rolled Birefringence) and HAN (Hybrid Aligne)
dNematic) mode liquid crystal cells have already been proposed. The present invention relates to a VA mode, an OCB mode, and an HA mode in which rod-like liquid crystal molecules substantially vertically aligned
It is effective in a liquid crystal display device using a liquid crystal cell such as an N mode, and is particularly effective in a VA mode liquid crystal display device in which most rod-like liquid crystal molecules are substantially vertically aligned. VA mode liquid crystal cells include (1) VA mode liquid crystal cells in a narrow sense in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied and substantially horizontally when voltage is applied (Japanese Patent Application Laid-Open No. 176625), and (2) a liquid crystal cell (in the MVA mode) in which the VA mode is multi-domain (in the MVA mode) in order to enlarge the viewing angle.
7. Digest of tech. Papers (Preliminary Collection) 28 (199
7) Description of 845), (3) a liquid crystal cell (n-ASM mode) in which rod-like liquid crystal molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is performed when a voltage is applied (preliminary papers of the Japanese Liquid Crystal Symposium). Vol. 58-59 (1998)
And (4) a SURVAIVEAL mode liquid crystal cell (presented at LCD International 98).

[0043]

EXAMPLES [Example 1] (Preparation of optically biaxial transparent support) Average acetylation degree 60.9
% Cellulose acetate, 2.35 parts by weight of the following retardation increasing agent, 2.75 parts by weight of triphenyl phosphate and 2.75 parts by weight of biphenyl diphenyl phosphate.
20 parts by weight of 232.75 parts by weight of methylene chloride, 42.57 parts by weight of methanol and 8.50 parts of n-butanol
It dissolved in parts by weight. The obtained solution was cast using a drum casting machine to prepare a cellulose acetate film having a thickness of 105 μm after drying.

[0044]

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The cellulose acetate film was stretched at a substantial stretching ratio of 20% to produce an optically biaxial transparent support. The retardation of the transparent support at a wavelength of 633 nm was measured with an ellipsometer (M150, manufactured by JASCO Corporation). As a result, the retardation (Rth) in the thickness direction was 85 nm, and the in-plane retardation (Re) was 40 nm.

(Preparation of Optical Compensation Sheet) One surface of the transparent support was subjected to corona discharge treatment. 2% by weight of modified polyimide (manufactured by Nissan Chemical Co., Ltd.) on the surface subjected to corona discharge treatment
The solution was applied and dried to form an alignment film having a thickness of 0.5 μm. The surface of the alignment film was rubbed. A coating liquid was prepared by dissolving 20 parts by weight of an acrylic thermotropic liquid crystal polymer in 80 parts by weight of etrachloroethane.
The coating solution was applied on the alignment film. The mixture was heated at 160 ° C. for 5 minutes and allowed to cool at room temperature to fix the alignment state of the liquid crystal molecules. The thickness of the formed optically anisotropic layer was 1.5 μm. The retardation of the entire optical compensation sheet at a wavelength of 633 nm was measured with an ellipsometer (M150, manufactured by JASCO Corporation). As a result, the in-plane retardation (Re) was 40 m, and the retardation (Rth) in the thickness direction was 240 nm.

(Preparation of Elliptically Polarizing Plate) On the transparent support side of the optical compensatory sheet, a polarizing film and a transparent protective film were laminated in this order to prepare an elliptically polarizing plate. The transparent support was arranged such that the slow axis of the transparent support was parallel to the polarization axis of the polarizing film.

(Preparation of Liquid Crystal Display Device) The polarizing plate was deleted from a commercially available MVA liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.), and an elliptically polarizing plate prepared instead was pasted. With respect to the manufactured MVA liquid crystal display device, the viewing angle at which a contrast ratio of 10: 1 was obtained without image inversion was measured. As a result, the vertical, horizontal, and vertical viewing angles were 80 ° (similar to a commercially available device), but the oblique vertical, left, and right viewing angles were 60 °, which is significantly higher than the viewing angle (45 °) of a commercially available device. Improved.

Example 2 (Preparation of Optically Biaxial Transparent Support) 30 parts by weight of a norbornene resin (ARTON, manufactured by JSR Corporation) was dissolved in 70 parts by weight of methylene chloride. The obtained solution was cast using a band casting machine to prepare a norbornene film having a thickness of 100 μm after drying. The norbornene film was stretched in the longitudinal direction at a substantial stretch ratio of 15%, and further stretched in the width direction at a substantial stretch ratio of 7% to produce an optically biaxial transparent support. The retardation of the transparent support at a wavelength of 633 nm was measured with an ellipsometer (M150, manufactured by JASCO Corporation). As a result, the retardation (Rth) in the thickness direction was 45 nm, and the in-plane retardation (Re) was 40 nm.

(Preparation of Optical Compensation Sheet) One surface of the transparent support was subjected to corona discharge treatment. An aqueous solution of the following modified polyvinyl alcohol (2% by weight) and glutaraldehyde (0.1% by weight) was applied on the surface subjected to the corona discharge treatment, and dried to form an alignment film having a thickness of 0.5 μm.

[0051]

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30 parts by weight of the rod-like liquid crystalline molecule (N31) was
It was dissolved in 70 parts by weight of methylene chloride to prepare a coating solution. The coating solution was applied on the alignment film and dried. By heating at 130 ° C. for 1 minute, the rod-like liquid crystal molecules were aligned. Further, the rod-like liquid crystal molecules were polymerized by irradiating ultraviolet rays to fix the alignment state. The thickness of the formed optically anisotropic layer is 1.0
μm. The retardation of the entire optical compensation sheet at a wavelength of 633 nm was measured using an ellipsometer (M15
0, manufactured by JASCO Corporation. As a result, the in-plane retardation (Re) was 30 m, and the retardation (Rth) in the thickness direction was 120 nm.

(Preparation of Elliptically Polarizing Plate) On the transparent support side of the optical compensation sheet, a polarizing film and a transparent protective film were laminated in this order to prepare an elliptically polarizing plate. The transparent support was arranged such that the slow axis of the transparent support was parallel to the polarization axis of the polarizing film.

(Preparation of Liquid Crystal Display Device) The polarizing plate was deleted from a commercially available MVA liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.), and an elliptically polarizing plate prepared instead was pasted. With respect to the manufactured MVA liquid crystal display device, the viewing angle at which a contrast ratio of 10: 1 was obtained without image inversion was measured. As a result, the vertical, horizontal, and vertical viewing angles were 80 ° (similar to a commercially available device), but the oblique vertical, horizontal, and vertical viewing angles were 70 °, which was significantly higher than the viewing angle (45 °) of a commercially available device. Improved.

Example 3 (Preparation of a transparent support) 45 parts by weight of cellulose acetate having an average acetylation degree of 60.9%, and 2.75 of triphenyl phosphate
Parts by weight and 2.20 parts by weight of biphenyldiphenyl phosphate were added with 232.75 parts by weight of methylene chloride and 4 parts by weight of methanol.
Dissolved in 2.57 parts by weight and 8.50 parts by weight of n-butanol. The obtained solution was cast using a drum casting machine to prepare a transparent support (cellulose acetate film) having a thickness of 105 μm after drying. The retardation of the transparent support at a wavelength of 633 nm was measured with an ellipsometer (M150, manufactured by JASCO Corporation). As a result, the retardation (Rth) in the thickness direction is 45 n
m, the in-plane retardation (Re) was 3 nm.

(Preparation of Optical Compensation Sheet) A gelatin undercoat layer was provided on both sides of the transparent support. An aqueous solution of 2% by weight of the modified polyvinyl alcohol used in Example 2 and 0.1% by weight of glutaraldehyde was applied on the gelatin undercoat layers on both sides, and dried to form an alignment film having a thickness of 0.5 μm. One of the alignment films was rubbed. 30 parts by weight of rod-like liquid crystal molecules (N31) were dissolved in 70 parts by weight of methylene chloride to prepare a coating solution. The coating solution was applied on the rubbed alignment film and dried. By heating at 130 ° C. for 1 minute, the rod-like liquid crystal molecules were aligned. Further, the rod-like liquid crystal molecules were polymerized by irradiating ultraviolet rays to fix the alignment state. The thickness of the formed optically anisotropic layer was 1.2 μm.

Next, the other alignment film was rubbed.
The rubbing process was performed so that the rubbing direction was perpendicular to the rubbing direction in the rubbing process.
A coating liquid was prepared by dissolving 30 parts by weight of rod-like liquid crystal molecules (N40) in 70 parts by weight of methylene chloride. The coating solution was applied on the rubbed alignment film and dried. 130 ° C
For 1 minute to align the rod-like liquid crystalline molecules. Further, the rod-like liquid crystal molecules were polymerized by irradiating ultraviolet rays to fix the alignment state. The thickness of the formed second optically anisotropic layer is
It was 2.0 μm. The retardation of the entire optical compensation sheet at a wavelength of 633 nm was measured with an ellipsometer (M150, manufactured by JASCO Corporation). As a result, the in-plane retardation (Re) was 60 nm, and the retardation (Rth) in the thickness direction was 120 nm.

Example 4 (Preparation of Optical Compensation Sheet) A commercially available average acetylation degree was 60.9.
% Cellulose acetate film (Fuji Photo Film Co., Ltd.) was used as a transparent support. On one side of the transparent support, a gelatin subbing layer was provided. On the gelatin undercoat layer, an aqueous solution of 2% by weight of the modified polyvinyl alcohol and 0.1% by weight of glutaraldehyde used in Example 2 was applied and dried to form an alignment film having a thickness of 0.5 μm.
The alignment film was rubbed. Rod-like liquid crystalline molecules (N31)
30 parts by weight were dissolved in 70 parts by weight of methylene chloride to prepare a coating solution. The coating solution was applied on the rubbed alignment film and dried. By heating at 130 ° C. for 1 minute, the rod-like liquid crystal molecules were aligned. Further, the rod-like liquid crystal molecules were polymerized by irradiating ultraviolet rays to fix the alignment state. The thickness of the formed optically anisotropic layer was 1.2 μm.

The optically anisotropic layer was subjected to a corona discharge treatment. Modified polyimide (manufactured by Nissan Chemical Co., Ltd.) on the optically anisotropic layer
Was applied and dried to form an alignment film having a thickness of 0.5 μm. The surface of the alignment film was rubbed.
The rubbing process was performed so that the rubbing direction intersects the rubbing direction in the rubbing process at 45 °. 30 parts by weight of rod-like liquid crystal molecules (N34) were dissolved in 70 parts by weight of methylene chloride to prepare a coating solution. The coating solution was applied on the rubbed alignment film and dried. 14
By heating at 0 ° C. for 3 minutes, the rod-like liquid crystalline molecules were aligned.
Further irradiate with ultraviolet rays to polymerize the rod-like liquid crystalline molecules,
The orientation state was fixed. The thickness of the formed second optically anisotropic layer was 1.8 μm. The retardation of the entire optical compensation sheet at a wavelength of 633 nm was measured with an ellipsometer (M150, manufactured by JASCO Corporation). As a result, the in-plane retardation (Re) was 100 nm, and the retardation (Rth) in the thickness direction was 200 nm.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a transmission type liquid crystal display device.

FIG. 2 is a schematic diagram showing a basic configuration of a reflection type liquid crystal display device.

[Explanation of symbols]

 BR Backlight RP Reflector 1, 1a, 1b, 1c Transparent protective film 2, 2a, 2b Polarizing film 3, 3a, 3b Transparent support 4, 4a, 4b Optically anisotropic layer 5a Lower substrate of liquid crystal cell 5b Liquid crystal cell Upper substrate 6 Rod-like liquid crystalline molecules

Claims (11)

[Claims] 1. An optical compensation sheet having an optically anisotropic layer formed from a transparent support and rod-like liquid crystalline molecules, wherein the average tilt angle between the major axis direction of the rod-like liquid crystalline molecules and the transparent support surface. An optical compensatory sheet characterized in that the rod-like liquid crystalline molecules are oriented in a state of less than 5 °. 2. The optical compensation sheet according to claim 1, wherein the transparent support has optical uniaxiality or optical biaxiality. 3. An in-plane slow axis of the transparent support and an average direction of a line obtained by projecting a major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface are substantially parallel or orthogonal. The optical compensation sheet according to claim 2. 4. The method according to claim 1, further comprising a second optically anisotropic layer formed of rod-like liquid crystalline molecules,
The optical compensatory sheet according to claim 1, wherein the rod-like liquid crystal molecules are oriented in a state where the average tilt angle between the major axis direction of the rod-like liquid crystal molecules and the transparent support surface is less than 5 °. 5. The optical compensation sheet according to claim 4, wherein the optically anisotropic layer and the second optically anisotropic layer are provided on the same side of the transparent support. 6. The optical compensation sheet according to claim 4, wherein the second optically anisotropic layer, the transparent support, and the optically anisotropic layer are laminated in this order. 7. An average direction of a line obtained by projecting a major axis direction of rod-like liquid crystalline molecules of an optically anisotropic layer onto a surface of a transparent support;
The optical compensation sheet according to claim 4, wherein the average direction of a line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules of the second optically anisotropic layer onto the surface of the transparent support is substantially orthogonal. 8. The average direction of a line obtained by projecting the major axis direction of rod-like liquid crystalline molecules of the optically anisotropic layer onto the surface of the transparent support;
5. The method according to claim 4, wherein the major axis direction of the rod-like liquid crystalline molecules of the second optically anisotropic layer intersects at an angle of 5 ° to 85 ° with an average direction of a line obtained by projecting the direction on the transparent support surface. Optical compensation sheet. 9. An elliptically polarizing plate having a transparent support, an optically anisotropic layer formed from rod-like liquid crystal molecules, a polarizing film and a transparent protective film, wherein the major axis direction of the rod-like liquid crystal molecules and the transparent support surface Wherein the rod-shaped liquid crystalline molecules are oriented in a state where the average inclination angle between the liquid crystal molecules is less than 5 °. 10. The transmission axis in the plane of the polarizing film and the average direction of a line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules of the optically anisotropic layer onto the transparent support surface are substantially parallel. 10. The elliptically polarizing plate according to claim 9, wherein the elliptically polarizing plate is orthogonal. 11. A liquid crystal display comprising a VA mode liquid crystal cell and two polarizing elements disposed on both sides thereof, wherein at least one of the polarizing elements is formed of a transparent support and rod-like liquid crystal molecules. An elliptically polarizing plate having an optically anisotropic layer, a polarizing film and a transparent protective film, wherein the rod-like liquid crystal molecules have an average inclination angle of less than 5 ° between the major axis direction of the rod-like liquid crystal molecules and the transparent support surface. A liquid crystal display device characterized in that is oriented.