JP2003021718A - Optical compensation sheet, polarizing plate and twisted nematic liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical compensation sheet improving lowering of contrast and reversal of coloring and colors observed in viewing in an oblique direction from the above, below, left and right, a polarizing plate and a liquid crystal display device using them. SOLUTION: In the optical compensation sheet having a biaxial supporting body and an optically anisotropic layer with respective slow axes nearly perpendicularly intersecting with each other, the optical compensation sheet is provided with the biaxial supporting body with 20-65 nm RO (B), 60-200 nm Rt and 2.0-4.5 Rt/RO (B) and the optically anisotropic layer with 50-255 nm RO (LC) where the RO difference between the biaxial supporting body and the optically anisotropic layer [RO (LC)-RO (B)] is 35-70 nm and the RO ratio [RO(LC)/RO (B)] is 2.5-6.5 and the direction exhibiting the maximum RO (LC) value of the optically anisotropic layer is deviating from the sheet normal direction by 20-80 deg..

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical compensation sheet,
The present invention relates to a polarizing plate and a twisted nematic liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, the following optical compensatory sheets have been used for expanding the viewing angle of liquid crystal display devices.
Seed configurations have been attempted, each proposed as an effective method.

(1) A method of supporting a discotic liquid crystal compound, which is a compound having negative uniaxiality, on a support (2) A depth of a nematic polymer liquid crystal compound having positive optical anisotropy A method of supporting on a support a hybrid orientation in which the pretilt angle of liquid crystal molecules changes in the direction (3) A nematic liquid crystal compound having positive optical anisotropy is formed on the support in a two-layer structure. Method of giving pseudo negative uniaxially similar optical properties by making the orientation direction of each layer approximately 90 degrees Each of the above-mentioned configurations has the following problems.

In the method described in the above (1), when applied to a TN mode liquid crystal panel, a disadvantage peculiar to the discotic liquid crystal compound is that the screen is colored yellow when viewed from an oblique direction.

In the method described in (2) above, the liquid crystal development temperature is high, and the orientation of the liquid crystal cannot be fixed on an isotropic transparent support such as TAC (cellulose triacetate), so that it is necessary to carry out another support once. After fixing the orientation on the body, it is necessary to transfer to a support such as TAC, which complicates the process and significantly lowers the productivity.

As an example of the method described in the above (3), for example, in JP-A-8-15681, an optically anisotropic layer using a rod-shaped positive uniaxial low molecular weight liquid crystal compound is used as an alignment function. Forming a layer composed of a rod-shaped positive uniaxial low-molecular liquid crystal compound oriented through an orientation layer having, and immobilizing it, and further through an orientation layer having an orientation ability on this layer. There is disclosed an optically anisotropic layer having a four-layer structure in which a layer made of a rod-shaped positive uniaxial low molecular weight liquid crystal compound reoriented is formed and fixed. In this case, it is possible to give a pseudo disk-like characteristic by shifting the alignment directions projected in the planes of the two liquid crystal layers by 90 degrees, for example.

Therefore, the method described in the above (3) has no coloring problem unlike the case of the discotic liquid crystal compound, so that color reproducibility is important in the liquid crystal TV (TV).
It has extremely advantageous characteristics in applications such as.

On the other hand, the TN type liquid crystal panel has characteristics such as high-speed response and high aperture ratio as well as productivity, and has a potential to support moving image display including color reproducibility. However, the TN panel itself has major problems such as viewing angle and color reversal, and it is general that optical compensation is performed by a sheet or the like except for dividing cells.

Further, as a viewing angle compensation of a TFT-TN liquid crystal display, as disclosed in Japanese Patent Application Laid-Open No. 7-191217, a discotic liquid crystal film is arranged on the upper and lower surfaces of the liquid crystal cell, Attempts have been made to improve the viewing angle characteristics of the. A compensation film for a TN type liquid crystal display is disclosed, for example, in JP-A-3-87720.
Similar to the retardation compensating plate for a liquid crystal display described in Japanese Patent Laid-Open No. 4-333019, it is composed of an optically anisotropic layer in which a liquid crystal compound is oriented on an optically nearly isotropic resin film. ing.

There are also the types disclosed in US Pat. No. 5,619,352, WO 9,744,702 and the like, but this method has at least two layers having different properties on a support. It is necessary to dispose the optically anisotropic layer so that the in-plane slow axis is perpendicular to it, which causes a large problem in terms of productivity.

The above-mentioned optical compensation sheets have a wider viewing angle in the range of the contrast ratio than the uncompensated TN type panel in terms of performance, but a method of applying a voltage in the direction parallel to the display of liquid crystal molecules, So-called IPS
Compared with the method, the viewing angle is still narrow, and there are major problems in terms of performance such as inversion and color change,
There is a demand for the development of a new compensation method that solves the above problems.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a viewing angle characteristic of a TN type LCD such as a TN-TFT, that is, a screen when viewed from an oblique direction. (EN) An optical compensatory sheet and a polarizing plate which can easily improve the coloring and light / dark reversal phenomenon, and a liquid crystal display device which uses the same and has a significantly improved viewing angle with a simple structure.

[0013]

The above objects of the present invention have been achieved by the following constitutions.

1. An optical compensatory sheet having an optically biaxial transparent support and at least one optically anisotropic layer, which satisfies any of the following conditions A to D.

A. The transparent support has a retardation value [R0 (B)] represented by the above formula (1) of 20 nm to 65 n.
m, the retardation value [Rt
(B)] is 60 nm to 200 nm, and the ratio [Rt (B) / R0 (B)] of Rt (B) and R0 (B) is 2.0.
To 4.5, and B.I. The optically anisotropic layer is a layer in which a liquid crystalline compound expressing a nematic phase is aligned and the alignment state is fixed in a monodomain or a domain of 0.1 μm or less, and C.I. The retardation value R0 (LC) of the optically anisotropic layer is 50 nm to 255 nm,
When the slow axis of the optically anisotropic layer and the in-plane slow axis of the transparent support are projected on the sheet surface, the angle between them is 80 ° to 100 °, and the retardation value of the optically anisotropic layer is R0
(LC) and retardation value R0 (B) of the transparent support
Difference [R0 (LC) -R0 (B)] of 35 nm to 17
0 nm and the ratio [R0 (LC) / R0 (B)] is 2.5 to 6.5, D. The direction showing the maximum value of the retardation value R0 (LC) of the optically anisotropic layer is 20 ° to 80 ° from the sheet normal direction.

2. 2. The optical compensation sheet as described in 1 above, wherein the biaxial transparent support contains a cellulose ester resin.

3. Where the degree of substitution of the acetyl group of the cellulose ester resin is A and the degree of substitution of the propionyl group is B, both conditions of the formula (3) and the formula (4) are satisfied, and the above-mentioned item 2 is satisfied. Optical compensation sheet.

4. The slow axis of the biaxial transparent support,
Any one of the above items 1 to 3, which is substantially orthogonal to the direction (MD direction) in which the transparent support is conveyed during film formation.
An optical compensation sheet according to item.

5. When the wavelength dispersion characteristics when viewed from the normal direction of the optical compensation sheet are such that the in-plane retardation value at a wavelength of 590 nm is R0 (590) and the in-plane retardation value at a wavelength of 480 nm is R0 (480), the ratio thereof [R0 (480) / R0 (590)] is 0.9 to 1.
4 the difference [R0 (480) -R0 (590)] is-
The optical compensation sheet according to any one of items 1 to 4, wherein the optical compensation sheet has a thickness of 5 to 45 nm.

6. The optically anisotropic layer in which the liquid crystal molecules of the optical compensation sheet of any one of the above items 1 to 5 are oriented and fixed are arranged on the polarizer or polarizing plate side, and the optically anisotropic layer is optically anisotropic from the biaxial support side. When the layers are viewed, the polarizing plate is arranged so that the angle formed by the optical axis of the liquid crystal molecules and the surface of the optical compensation sheet decreases continuously or stepwise in the thickness direction of the optical compensation sheet. .

7. 7. The polarizing plate as described in 6 above, wherein the liquid crystal compound exhibits a nematic liquid crystal phase and is optically positive uniaxial.

8. 7. The polarizing plate according to the item 6, wherein the liquid crystalline compound exhibits a nematic liquid crystal phase and is optically biaxial.

9. A twisted nematic liquid crystal display device having a driving liquid crystal cell consisting of a pair of transparent substrates having electrodes and a nematic liquid crystal, and an upper polarizer and a lower polarizer above and below the transparent substrate. Between the substrate and at least one of the upper polarizer and the lower polarizer, at least the optical compensation sheet according to any one of the above items 1 to 5 is provided so that the biaxial support is on the transparent substrate side. A twisted nematic type liquid crystal display device characterized in that one is arranged.

As a result of earnest studies on the above problems, the present inventors have found that the alignment layer and the alignment of the liquid crystal compound are fixed on the transparent support having specific optical characteristics and adjacent to the alignment layer. By using the optical compensatory sheet having the optically anisotropic layer, it is possible to provide a polarizing plate having a significantly improved viewing angle characteristic as compared with the prior art and a liquid crystal display device using them.

The details of the present invention will be described below. First, the optically biaxial transparent support according to the present invention will be described.

The biaxial transparent support according to the optical compensation sheet of the present invention has a characteristic that the transmittance in the visible region is 80% or more, and specifically, it is a cellulose ester derivative, polyethylene terephthalate, Polycarbonate,
Examples include polyarylate and polysulfone. Among the above descriptions, the cellulose ester derivative can be preferably used from the viewpoint of obtaining the desired optical characteristics and the productivity.

From the viewpoint of the productivity of the transparent support, a preferable method for producing the transparent support is to use a transparent support solution (for example, a support).
A belt or a drum is used) to form a film by casting,
It is a film-forming method in which the solvent is removed from the support (belt or drum) while the solvent remains, and then the film is stretched while being dried.

In the invention according to claim 1, as the biaxial transparent support, the retardation value [R0 (B)] represented by the formula (1) is 20 nm to 65 nm, and the retardation value represented by the formula (2). Retardation value [Rt (B)] is 6
One of the characteristics is that the ratio [Rt (B) / R0 (B)] of Rt (B) to R0 (B) is 2.0 to 4.5 at 0 nm to 200 nm, and in-plane retardation [R0
(B)] is more preferably 30 nm to 50 nm, and the retardation [Rt (B)] in the thickness direction is 7
More preferably 5 nm to 140 nm, Rt
The value of (B) / R0 (B) is more preferably 2.5 to 3.5. Further, the in-plane retardation is preferably generated in the width direction, and therefore, the stretching direction during film formation is preferably substantially orthogonal to the transport direction. The substantially orthogonal direction is 90 ° ± 5 ° with respect to the transport direction,
90 ° is preferred.

In the present invention, the refractive index of the biaxial transparent support can be measured by using an ordinary refractometer, for example, an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments). At 23 ° C. and 55% RH, the wavelength is 590 nm or 480 nm,
It is possible to obtain the retardation values R0 and Rt by performing three-dimensional refractive index measurement, calculating the refractive indexes Nx, Ny and Nz, and measuring the film thickness.

The invention according to claim 2 is characterized in that the biaxial transparent support is made of a cellulose ester resin.

In the invention according to claim 3, the substituents of the acetyl group and the propionyl group of the cellulose ester resin used for producing the cellulose ester film which is an optically biaxial transparent support are represented by the above formula (3) and Formula (4)
It is characterized by satisfying any of the relations.

As the cellulose ester resin that can be used in the present invention, it is extremely effective to use a cellulose ester resin having an acetyl group and a propionyl group, and it is preferable to use cellulose acetate propionate.

As the cellulose ester used in the present invention, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination. It is preferable to use a large amount of cellulose ester synthesized from cotton linter, which has good peelability from a belt or a drum, because the production efficiency is high. The ratio of the cellulose ester synthesized from cotton linter is preferably 60% by mass or more, more preferably 85% by mass or more, and further preferably used alone, from the viewpoint that the effect of releasability becomes remarkable.

The thickness of the cellulose ester film support used for the optical compensatory sheet according to the present invention may be such that it has optical characteristics for improving the viewing angle characteristics of a liquid crystal display, and it depends on the stretching ratio and the thickness of the transparent support. It can be controlled, and is preferably 35 μm or more and 250 μm or less, more preferably 60 μm or more and 140 μm or less. If the cellulose ester film support is thinner than this range, it becomes difficult to obtain the desired optical characteristics. On the contrary, if it is thicker than the above range, the optical characteristics become unnecessarily large, and the viewing angle characteristics of the liquid crystal display are deteriorated, which is not preferable.

In the present invention, when the optical compensatory sheet is used as a protective film for a polarizing plate or when the optical compensatory sheet is attached to a polarizer having a protective film, the optical compensatory sheet is provided between the liquid crystal cell and the polarizer. It is preferable to install it.

A conventionally known polarizer can be used as the polarizer. The polarizing plate in the present invention refers to a polarizer sandwiched between protective films. For example, a polarizer can be produced by using polyvinyl alcohol-iodine, and a protective film of triacetyl cellulose can be adhered from both sides to produce a polarizing plate.

The alignment layer according to the present invention will be described. The alignment layer according to the present invention is disposed on the transparent support and is used to align the liquid crystal compound in the optical anisotropic layer adjacent to the optical anisotropic layer described later.

Here, the materials constituting the alignment layer will be described. Specific materials for forming the alignment layer include, but are not limited to, the following resins and substrates. For example, polyimide, polyamide imide, polyamide, polyether imide, polyether ether ketone, polyether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal. , Polycarbonate,
Examples thereof include polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, polyvinylpyrrolidone, cellulosic plastics, epoxy resin and phenol resin.

A known method can be used for the alignment treatment, but a widely used processing method can be used for the rubbing treatment as a liquid crystal alignment treatment step for LCD. It can also be used.

Next, the optically anisotropic layer according to the present invention will be described. The optical anisotropic layer according to the optical compensatory sheet of the present invention, in order to improve the viewing angle characteristics of the liquid crystal display, the thickness of the optical anisotropic layer, the birefringence of the liquid crystal compound constituting it, and the alignment of the liquid crystal compound. It depends on the condition,
Generally, the film thickness is 0.2 μm or more and 5 μm or less, preferably 0.4 μm or more and 3 μm or less.

The optically anisotropic layer according to the present invention can be provided in at least one layer with respect to the optically biaxial cellulose ester film support, but one optically biaxial transparent support can be provided. On the other hand, it is also possible to install a plurality of optically anisotropic layers, and when the liquid crystal compound contained in the optically anisotropic layer is oriented or the orientation of the liquid crystal compound is fixed, the orientation direction is appropriately displayed. It is possible to design optical characteristics suitable for.

In the present invention, the optically biaxial transparent support has predetermined optical characteristics, so that the liquid crystal layer coated on the support is a single layer to reduce the cost and productivity. From the viewpoint of.

When the optical compensation sheet of the present invention is installed,
Usually, an upper polarizer and a lower polarizer are arranged above and below a pair of substrates located on both sides of the driving liquid crystal cell,
The liquid crystal display device according to claim 9 is characterized in that at least one optical compensation sheet of the present invention is installed between the substrate and at least one of the upper and lower polarizers, and in particular, from the viewpoint of cost reduction. Further, in order to exert the desired effects of the present invention, it is preferable to install one optical compensation sheet of the present invention between the substrate and each of the upper polarizer and the lower polarizer.

When the liquid crystal display device is a twisted nematic type (TN type) liquid crystal display device, an optically biaxial transparent support of the optical compensation sheet of the present invention is provided on the side of the substrate closest to the TN type liquid crystal cell. The optical compensatory sheet is attached so that the body surface side comes, and the maximum refractive index direction in the optically biaxial transparent support surface of the optical compensatory sheet is substantially the same as the alignment direction of the nematic liquid crystal of the substrate closest to the liquid crystal cell. By bonding in a direction orthogonal to each other, an excellent effect can be exhibited. Substantially orthogonal is 90 ° ± 5 °, but 90 ° is particularly preferable.

In the optically anisotropic layer formed by orienting and fixing the liquid crystal molecules according to the present invention, the average tilt angle of the liquid crystal molecules is, when observed from the cross sectional direction of the optically anisotropic layer,
It is preferably oblique, and the orientation angle may change with respect to the thickness direction. Further, the inclination angle is high on the side of the biaxial transparent support and decreases as it approaches the polarizer, and this change is preferably continuous. The average tilt angle is different depending on the design of the display in order to compensate the viewing angle of the display, but it is preferably 10 ° or more and 70 ° or less, and preferably 25 ° or more and 50 ° or less, particularly in the TN type liquid crystal display device. .

In the invention according to claim 1, the retardation value R0 (LC) of the optically anisotropic layer is 50 nm to 255 nm.
And the difference between the retardation value R0 (LC) of the optically anisotropic layer and the retardation value R0 (B) of the transparent support [R0
(LC) -R0 (B)] is 35 nm to 170 nm,
One of the characteristics is that the ratio [R0 (LC) / R0 (B)] is 2.5 to 6.5. The retardation value R0 (LC) of the optically anisotropic layer can also be obtained in the same manner as the above equation (1).

In the optically anisotropic layer according to the present invention, R0
(LC) is preferably 70 nm to 210 nm, and R0 (LC) -R0 (B) is preferably 60 to 125 nm. Also, R0 (LC) / R0 (B)
Is preferably 2.5 to 5, and 2.5 to 4.
It is more preferably 5.

Further, in the present invention, the direction (direction A) in which the maximum refractive index direction of the optically anisotropic layer is projected on the optically biaxial transparent support surface is the optically biaxial It is preferable that it is substantially equal to the Ny direction (direction B) of the transparent support.
Here, being substantially equal to the Ny direction means that the angle formed by the direction A and the direction B is within ± 2 °.

Next, the liquid crystal compound according to the present invention will be described. The liquid crystal compound according to the present invention is not particularly limited as long as the liquid crystal compound can be aligned, and as a result, the orientation imparts optical anisotropy without light scattering in the visible light region.

As the liquid crystal compound of the present invention other than the polymer liquid crystal, a rod-shaped liquid crystal compound is generally mentioned, and a liquid crystal compound showing optically positive birefringence is preferable, and unsaturated ethylene is more preferable. A positive birefringent liquid crystal compound having a functional group is preferable from the viewpoint of fixing alignment, and for example, JP-A-9-281480 and 9-281.
Examples thereof include compounds having the structure described in No. 481, but the compounds are not particularly limited thereto.

The structure of the liquid crystal compound according to the present invention is not particularly limited, but the optically anisotropic layer according to the present invention exhibits a desired optical anisotropy, so that the liquid crystal molecules are aligned in a chemical reaction or The orientation of the liquid crystal compound can be fixed by the treatment utilizing the temperature difference. In addition, when a solution containing a liquid crystal compound and an organic solvent is prepared, and the solution is applied and dried to form an optically anisotropic layer, alignment treatment of the liquid crystal compound is performed at a temperature not higher than the liquid crystal transition temperature without heating the liquid crystal transition temperature or higher. It is also possible to

When a solution containing a liquid crystal compound is applied, the solvent is dried and removed after application to obtain a liquid crystal layer having a uniform film thickness. The liquid crystal layer can fix the alignment of the liquid crystal by the action of heat or light energy or a chemical reaction by the combined use of heat and light energy.

Examples of the radical polymerization initiator for the above-mentioned ethylenically unsaturated group polymerization reaction include azobis compounds, peroxides, hydroperoxides and redox catalysts such as potassium persulfate, ammonium persulfate and tert-butyl. Peroctoate, benzoyl peroxide, isopropyl percarbonate,
2,4-dichlorobenzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, dicumyl peroxide, azobisisobutyronitrile, 2,2'-azobis (2-amidinopropane) hydrochloride or benzophenones, acetophenone And benzoins, thioxanthones and the like. For details of these, "Ultraviolet Curing System" General Technology Center, pp. 63-147, 1989.
It is listed in the year etc.

Further, when the curing reaction is carried out by using the radical reaction, it is possible to shorten the reaction time by irradiating the above-mentioned actinic rays under a nitrogen atmosphere in order to avoid the delay of the polymerization reaction due to the presence of oxygen in the air. It is preferable in that it can be cured with a small amount of light.

On the other hand, when the liquid crystal compound is a polymer liquid crystal, it is not necessary to carry out the curing reaction by the above chemical reaction to fix the alignment of the liquid crystal. For example, the orientation can be fixed by heat-treating the polymer liquid crystal at a glass transition temperature or higher and allowing it to cool to the glass transition temperature or lower.

When the glass transition temperature of the polymer liquid crystal is higher than the heat resistance temperature of the support, the alignment film is placed on the heat resistant support, the polymer liquid crystal is applied, and then the glass of the polymer liquid crystal is applied. It can be oriented by heating above the transition temperature. This can be allowed to cool to room temperature to fix the alignment of the polymer liquid crystal, and then transferred to the support of the present invention using an adhesive to prepare an optically anisotropic body.

In the present invention, an optically anisotropic layer may be formed on the polarizing plate protective film, and a biaxial support may be attached thereto to give the optical compensation film or polarizing plate of the present invention.

The wavelength dispersion characteristics of the optical compensation sheet of the present invention will be described. In the invention according to claim 5, the chromatic dispersion characteristics when viewed from the normal direction of the optical compensation sheet are
The in-plane retardation value at a wavelength of 590 nm is R0 (59
0), the in-plane retardation value at a wavelength of 480 nm is R0
When it is set to (480), the ratio [R0 (480) / R0
(590)] is 0.9 to 1.4, and the difference [R0 (4
80) -R0 (590)] is -5 to 45 nm.

The wavelength dispersion characteristic referred to in the present invention means a wavelength of 48
It refers to the in-plane retardation value [R0 (480)] of the optical compensation sheet at 0 nm and the in-plane retardation [R0 (590)] of the optical compensation sheet at a wavelength of 590 nm. The ratio [R0 (480) / R0 (5
90)] is 0.9 to 1.4, but 1.0 to 1.3 is more preferable. When it is difficult to directly measure at the above wavelength, it is also possible to use the value calculated by Cauchy's equation after measuring at several different wavelengths.

According to the present invention, the viewing angle is extremely wide, and it is possible to remarkably improve the deterioration of contrast, coloring and reversal of tint.

[0061]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

<< Preparation of Optically Biaxial Transparent Support >> By the production method described below, using Cellulose Ester Resin 1 shown below as a cellulose ester resin, a transparent support 1 to 1 which is a cellulose ester film is used. 3 was prepared, and the cellulose ester resin 2 was used to prepare a transparent support 4 which was a cellulose ester film.

(Preparation of transparent supports 1 to 3) Cellulose ester resin 1 (cellulose acetate propionate)
Acetyl group substitution degree 1.90 Propionyl group substitution degree 0.
75 number-average molecular weight 120,000) 100 parts by mass, ethylphthalylethyl glycolate 2 parts by mass, triphenyl phosphate 8.5 parts by mass, methylene chloride 290 parts by mass, and ethanol 60 parts by mass are put in a closed container, and the mixture is slowly added. While stirring, the temperature was gradually raised to 45 ° C. over 60 minutes and dissolved to prepare a dope. 121kP inside the container
It became a. This dope was used as Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. After filtering using 244, it was left to stand for 24 hours to remove bubbles in the dope. Also, apart from this,
5 parts by mass of the above cellulose ester resin 1 and TINUVIN 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.)
6 parts by mass, Tinuvin 109 (manufactured by Ciba Specialty Chemicals Co., Ltd.) 4 parts by mass, Tinuvin 171 (Ciba
Specialty Chemicals Co., Ltd.) 4 parts by mass and A
EROSIL R972V (manufactured by Nippon Aerosil Co., Ltd.)
To 1 part by mass of each of these, 94 parts by mass of methylene chloride and 8 parts by mass of ethanol were added, mixed, stirred and dissolved to prepare an ultraviolet absorbent solution 1. The UV absorber solution 1 was added at a ratio of 2 parts by mass to 100 parts by mass of the dope, thoroughly mixed by a static mixer, and then cast from a die onto a stainless belt at a dope temperature of 30 ° C.
After contacting hot water having a temperature of 25 ° C. from the back surface of the stainless belt and drying for 1 minute on the temperature-controlled stainless belt, after further contacting the back surface of the stainless belt with cold water at 15 ° C. and holding for 15 seconds, It was peeled off from the stainless belt. The amount of residual solvent in the web at the time of peeling was 100% by mass. Then, while the roll is conveyed in an oven at 120 ° C., both ends of the peeled web are gripped by clips with a tenter, and the clip interval in the width direction is changed, so that the web is stretched to about 10 to 50% in the width direction. It was Further, the stretched film is cooled to 60 ° C., and then 12
It was dried at 0 ° C. for 5 minutes to prepare a transparent support 1 having a film thickness of 85 μm.

Next, in the production of the transparent support 1, the stretching conditions are appropriately changed so that the film thicknesses are 88 μm and 80 μm.
m transparent supports 2 and 3 were produced.

Each of the transparent supports 1 to 3 has a glass fiber reinforced resin core having a core diameter of 200 mm and a width of 1 mm.
The film was wound into a film roll having a length of m and a length of 1000 m by the taper tension method. At this time, the temperature 2
An embossing ring of 70 ° C. was pressed against the substrate to perform a 10 μm thickening process to prevent the films from sticking to each other.

(Preparation of transparent support 4) Transparent support 3
In the production of, instead of the cellulose ester resin 1,
Acetyl group substitution degree 2.88, number average molecular weight 1400
A transparent support 4 having a film thickness of 80 μm was prepared in the same manner except that the cellulose ester resin 2 of No. 00 (cellulose triacetate) was used.

The optical properties of the above prepared transparent supports are shown below. In addition, the measurement is an automatic birefringence meter KOBRA-
21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) was used.

Transparent support 1: Rt = 105 nm, R0 = 35 nm Transparent support 2: Rt = 140 nm, R0 = 40 nm Transparent support 3: Rt = 75 nm, R0 = 30 nm Transparent support 4: Rt = 51 nm, R0 = 2 nm << Preparation of Optical Compensation Sheet >> (Preparation of Alignment Film Material) Compound 1 was water: methanol = 3:
A solution 1 was prepared by dissolving in a solvent of 2. In addition, compound 2
Was dissolved in a solvent of water: methanol = 3: 1 to prepare solution 2. Further, the compound 3 was dissolved in a solvent of water: methanol = 5: 1 to prepare a solution 3.

(Preparation of Liquid Crystal Material) Liquid crystal materials LC-1 to LC-3 were prepared according to the method described below.

[0070]   <Preparation of LC-1>   Compound 4 3 parts by mass   Compound 5 5 parts by mass   Compound 6 4 parts by mass   Compound 8 8 parts by mass   Irgacure 369 (manufactured by Ciba Specialty Chemicals Co., Ltd.)                                                             1 part by mass   2-butanone 80 parts by mass   Cyclohexanone 5 parts by mass   <Preparation of LC-2>   Compound 4 4 parts by mass   Compound 5 3 parts by mass   Compound 6 6 parts by mass   Compound 8 8 parts by mass   Irgacure 369 1 part by mass   2-butanone 84 parts by mass   <Preparation of LC-3>   Compound 4 3 parts by mass   Compound 6 6.5 parts by mass   Compound 7 3 parts by mass   Compound 8 1.5 parts by mass   Irgacure 369 1 part by mass   2-butanone 85 parts by mass

[0071]

[Chemical 1]

[0072]

[Chemical 2]

(Preparation of Optical Compensation Sheets 1 to 14) The transparent supports 1 to 4 were subjected to gelatin subbing with a film thickness of 0.1 μm and dried, and then the transparent supports 1 to 3 were listed in Table 1. The solution 1 and the solution 2 are applied in a combination as described above using a wire bar # 3 so as to have a dry film thickness of 0.2 μm, dried with hot air at 70 ° C., and then subjected to rubbing treatment to obtain the sheet 1 ~ 6 were produced. Next, the solution 3 was applied onto the transparent support 4 in the same manner, dried and rubbed to prepare a sheet 7.

Then, the sheets 1 to 7 prepared above were coated with the solutions LC-1 to 3 using the wire bar # 5 so that the combinations shown in Table 1 were obtained, and then 90 in a calm state.
After leaving still for 1 minute at ℃, and radiating heat, 500 mJ / cm ² of ultraviolet ray is irradiated in a state of oxygen concentration of 0.1% or less using nitrogen gas to fix the alignment of the liquid crystalline compound and to obtain an optical compensation sheet. 1-14 were produced. Structure of each optical compensation sheet obtained and R0, RO (LC) / RO (B) of the optically anisotropic layer
Table 1 shows RO (LC) -RO (B).

[0075]

[Table 1]

The optical compensatory sheet 13 is a laminated portion of the optically anisotropic layer and the transparent support 1 produced through the process of forming LC-3 on the transparent support 4 having no optically biaxiality. The value of RO (B) in Table 1 is shown by the RO (B) value of the transparent support 1.

(Wavelength Dispersion Characteristics of Optical Compensation Sheet) The retardation value RO (480) at 480 nm and the retardation value RO (590) at 590 nm of each of the optical compensation sheets prepared above were measured by an automatic birefringence meter KOBRA.
-21ADH (manufactured by Oji Scientific Instruments), P (ratio) and Q (difference) were measured by the following formulas, and the obtained results are shown in Table 2.

[0078] P = R0 (480) / R0 (590) Q = R0 (480) -R0 (590)

[0079]

[Table 2]

(Measurement of Tilt Angle) Next, the tilt angle of the alignment film interface and the tilt angle of the air interface and the average tilt angle of the combination of the alignment film material and the liquid crystal material were measured, and the obtained results are shown in Table 3.

The tilt angle is measured by the liquid crystal solutions LC-1 to L
After coating C-3 on the alignment layer, the solvent was dried and the alignment layers were aligned so as to be antiparallel. Furthermore, an orthoscopic image and a conoscopic image were observed in a liquid crystal temperature range using a hot stage, and an average tilt angle was measured when antiparallel processing was performed using the above automatic birefringence meter. Furthermore, the solutions LC-1 to LC are applied to the respective alignment layers.
-3 is applied, dried and heat-treated, an alignment layer is arranged on only one side of the liquid crystalline compound, and a sample is prepared so that the other side becomes an air interface. The crystal rotation method is used to prepare an alignment film and an air interface. The tilt angle was measured.

Although each solution was shown as the material of the alignment film, this solution was applied, dried and rubbed, and then evaluated using the solution of each liquid crystalline compound.

[0083]

[Table 3]

(Production of Comparative Optical Compensation Sheets 15 to 20) In the production of the above-mentioned optical compensation sheets 1 to 14, Table 4 shows each of the above-prepared sheets, each transparent support, each alignment film material and each liquid crystal compound. Comparative optical compensation sheets 15 to 20 having the retardation values of the optical anisotropic layers shown in Table 4 were prepared in the same manner except that the film thickness of the optical anisotropic layer was appropriately changed.

[0085]

[Table 4]

The optical compensatory sheet 20 is a laminated portion of the optically anisotropic layer and the transparent support 1 produced through a process of forming LC-2 on the transparent support 4 having no optically biaxiality. The value of RO (B) in Table 4 is shown by the RO (B) value of the transparent support 1.

<< Preparation of Polarizing Plate >> The above-prepared optical compensation sheets 1 to 14 of the present invention and the comparative optical compensation sheet 15 to
20 was laminated with a polarizing plate to prepare polarizing plates 1 to 20 with an optically anisotropic layer. Specifically, the optical compensation sheet 1
1 to 12 and 14 to 19 are coated with SK Dyne 2092 (manufactured by Soken Kagaku Co., Ltd.) on the optically anisotropic layer side and dried,
The lamination was carried out so that the rubbing axis of the optically anisotropic layer and the absorption axis of the polarizing plate as shown in (4) coincided with each other. Also, the optical compensation sheet 1
Regarding Nos. 3 and 20, first, the transparent support side was laminated so that the rubbing axis and the absorption axis of the polarizing plate were aligned, and then,
The transparent support 1 was attached to the optically anisotropic layer side so that the slow axis of the transparent support 1 was orthogonal to the slow axis of the optically anisotropic layer, and the polarizing plates 1 to 2 were thus formed.
0 was produced.

<< Evaluation of Polarizing Plate >> O. DAT
15 inch liquid crystal display LCD-A15H made by A company
The polarizing plates with optical anisotropic layers 1 to 20 prepared above were peeled off, and the optical anisotropic layer side was the liquid crystal cell side, and the absorption axis was first attached. It stuck on both sides so that it might correspond to an absorption axis, and evaluated.
The evaluation was performed using EZ-contrast manufactured by ELDIM, and the comparison was made with a polarizing plate in which three points of top, bottom, left and right, and the area were pasted in advance in a portion having a contrast ratio of 10: 1 for monochrome display. In addition, the inversion area and the change in tint are set to 70
Comparison was made by human sensory evaluation.

In each evaluation rank, + means I. O. The 15-inch liquid crystal display LCD manufactured by DATA Co., Ltd. indicates that the results are good as compared to the polarizing plate used for LCD-A15H, the-indicates that the results are poor, and the 0 indicates that they are equivalent. The numbers of + and-represent those degrees.

Table 5 shows the results obtained as described above.

[0091]

[Table 5]

As is clear from Table 5, the polarizing plate using the optical compensation sheet of the present invention is superior in vertical and horizontal viewing angle characteristics to the comparative product and can prevent coloration and color reversal. I understand.

[0093]

According to the present invention, there is provided an optical compensation sheet and a polarizing plate capable of improving viewing angle characteristics, that is, reduction in contrast when viewed from diagonally upward, downward, leftward and rightward directions, coloration and reversal of tint. A liquid crystal display device having a significantly improved viewing angle can be provided by using the liquid crystal display device.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a preferable layer structure of an optical compensation sheet used in a liquid crystal device of the present invention.

[Explanation of symbols]

1,8 Polarizer 2.7 Optically anisotropic layer 3,6 Biaxial support 4, 5 substrates 9, 11 Optically anisotropic compound 10 liquid crystal 12 Liquid crystal cell 13, 20 Polarizer transmission axis 14, 19 Rubbing direction 15, 18 Biaxial support stretching direction 16, 17 Substrate rubbing axis

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Noriyasu Kuzuhara             Konica Stock Market, 1 Sakura-cho, Hino City, Tokyo             In-house F term (reference) 2H049 BA02 BA06 BA42 BB03 BB49                       BC04 BC05 BC09 BC22                 2H091 FA08X FA08Z FA11X FA11Z                       FB02 HA07 LA17 LA19

Claims (9)

[Claims] 1. An optical compensatory sheet having an optically biaxial transparent support and at least one optically anisotropic layer, which satisfies any of the following conditions A to D. A. The transparent support has a retardation value [R0 (B)] represented by the following formula (1) of 20 nm to 65 nm and a retardation value [Rt (B)] represented by the following formula (2) is 6:
0 nm to 200 nm, the ratio [Rt (B) / R0 (B)] of Rt (B) and R0 (B) is 2.0 to 4.5, and the formula (1) R0 (B) = (Nx -Ny) * d (In the formula, Nx represents the maximum in-plane refractive index, Ny represents the in-plane refractive index in the direction orthogonal to Nx, and d represents the film thickness (nm). Formula (2) Rt (B) = ((Nx + Ny) / 2-Nz) * d [In formula, Nz represents the refractive index of a thickness direction, Nx, Ny,
d has the same meaning as in formula (1). ] B. The optically anisotropic layer aligns a liquid crystal compound exhibiting a nematic phase, and the alignment state is a monodomain or 0.
A layer in which the orientation is fixed in a domain of 1 μm or less, and C.I. The retardation value R0 (LC) of the optically anisotropic layer is 5
0 nm to 255 nm, and the angle between the slow axis of the optically anisotropic layer and the in-plane slow axis of the transparent support when projected onto the sheet surface is 80 ° to 100 °. The difference between the retardation value R0 (LC) of the anisotropic layer and the retardation value R0 (B) of the transparent support [R0 (LC) -R
0 (B)] is 35 nm to 170 nm, and the ratio [R0 (LC) / R0 (B)] is 2.5 to 6.5, and D. The direction in which the maximum value of the retardation value R0 (LC) of the optically anisotropic layer is 20 ° to 80 ° from the sheet normal direction.
°. 2. The optical compensation sheet according to claim 1, wherein the biaxial transparent support contains a cellulose ester resin. 3. When the degree of substitution of the acetyl group of the cellulose ester resin is A and the degree of substitution of the propionyl group is B, both conditions of the following formulas (3) and (4) are satisfied. The optical compensation sheet according to claim 2. Formula (3) 2.0 ≦ (A + B) ≦ 2.8 Formula (4) 0 ≦ B ≦ 1.0 4. The slow axis of the biaxial transparent support is substantially orthogonal to the transport direction (MD direction) during film formation of the transparent support. The optical compensation sheet according to any one of items. 5. The wavelength dispersion characteristics of the optical compensation sheet when viewed from the normal direction are such that the in-plane retardation value at a wavelength of 590 nm is R0 (590) and the in-plane retardation value at a wavelength of 480 nm is R0 (480). The ratio [R
0 (480) / R0 (590)] is 0.9 to 1.4.
And the difference [R0 (480) -R0 (590)] is -5.
To 45 nm, The optical compensation sheet according to claim 1, wherein 6. An optically anisotropic layer in which the liquid crystal molecules of the optical compensation sheet according to claim 1 are aligned and fixed, and the optically anisotropic layer is arranged on the side of a polarizer or a polarizing plate to provide biaxial support. When observing the optically anisotropic layer from the body side, it is arranged so that the angle formed by the optical axis of the liquid crystal molecules and the surface of the optical compensation sheet decreases continuously or stepwise in the thickness direction of the optical compensation sheet. Characteristic polarizing plate. 7. The polarizing plate according to claim 6, wherein the liquid crystalline compound exhibits a nematic liquid crystal phase and is optically positive uniaxial. 8. The polarizing plate according to claim 6, wherein the liquid crystal compound exhibits a nematic liquid crystal phase and is optically biaxial. 9. A twisted nematic liquid crystal display device having a driving liquid crystal cell including a pair of transparent substrates having electrodes and a nematic liquid crystal, and an upper polarizer and a lower polarizer above and below the transparent substrates. The optical compensatory sheet according to any one of claims 1 to 5 is provided between the transparent substrate and at least one of the upper polarizer and the lower polarizer, and the biaxial support is provided on the transparent substrate side. A twisted nematic liquid crystal display device, characterized in that at least one is arranged so that