JP2006091151A - Manufacturing method of optical film and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of stably manufacturing an optical film which has superior compensation functions for a liquid crystal display of the OCB system. <P>SOLUTION: This manufacturing method consists of a step of coating a liquid containing a liquid crystal compound on a support, and a step of orientating the liquid crystal compound at a temperature of the liquid crystal transition or higher, when or after the drying the liquid crystal compound layer made of the liquid and then fixing the orientation to obtain an optically by anisotropic layer. The liquid crystal compound layer is made 1.8 μm in thickness or smaller and the front retardation of the liquid crystal compound layer 27 nm or larger, the film is manufactured, in a way such that the lapping axis θ and the retardation axis ϕ of the optically by anisotropic layer satisfy the inequality formula (I). The inequality (I): ¾θ-ϕ¾<5°, where ϕ represents the retardation axis of the optical anisotropic layer measured by using a product "KOBRA-21ADH". <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing an optical film and a liquid crystal display device having the optical film.

  An optical film having a layer in which a liquid crystal compound is highly oriented and fixed has been developed in various applications in recent years, such as an optical compensation film of a liquid crystal display device, a brightness enhancement film, and an optical film of a projection display device. However, the development of liquid crystal display devices as optical films is remarkable. Usually, the liquid crystal display device includes a polarizing plate and a liquid crystal cell. In the TN type TFT liquid crystal display device which is currently mainstream, an optical compensation film is inserted between the polarizing plate and the liquid crystal cell to realize a liquid crystal display device with high display quality. However, in this configuration, the thickness of the liquid crystal display device itself is increased, and it is not possible to sufficiently meet the demand for thickness reduction.

  In contrast, by using an elliptically polarizing plate having a retardation film on one side of the polarizing film and a protective film on the other side, an invention that can increase the front contrast without increasing the thickness of the liquid crystal display device has been proposed. (For example, refer to Patent Document 1). However, with the phase difference film (optical film) having the above-described configuration, a sufficient viewing angle improvement effect cannot be obtained, and the display quality of the liquid crystal display device may deteriorate. At present, the thickness of the liquid crystal display device is increased by using an optical film in which an optically anisotropic layer formed from a discotic compound is coated on a transparent support directly as a protective film for a polarizing plate. However, the problem regarding the viewing angle is solved (for example, see Patent Documents 2 and 3).

Conventionally, optical films for optical compensation of TN liquid crystal display devices, which are currently mainstream, have been developed. Recently, however, demand for liquid crystal televisions is increasing, and liquid crystal televisions cause tailing in moving images. It has been pointed out that there is a problem in response speed, and as a solution to this, an OCB type liquid crystal display device has been proposed, and an optical film for optical compensation of such a type of liquid crystal display device has been proposed. . For example, Patent Documents 4 and 5 describe that by applying an optical film having a layer made of a liquid crystal compound to an OCB type liquid crystal display device, it is possible to deal with moving images and solve problems such as viewing angle. Has been.
However, it is very difficult to manufacture an optical film having good performance by controlling the optical parameters of each layer continuously in a large quantity, and in a roll form advantageous for transportation and storage. there were.

JP-A-2-247602 Japanese Patent Laid-Open No. 7-191217 European Patent No. 0911656A2 JP-A-9-212444 JP 11-316378 A

The present invention provides a method capable of stably and continuously producing an optical film having an excellent optical compensation function for a liquid crystal display device, particularly an OCB type liquid crystal display device having a high response speed and suitable for moving images. It is an object of the present invention to provide an optical film having an excellent optical compensation function and to provide the optical film in a roll shape.
In addition, the present invention has a polarizing function and an excellent optical compensation function for a liquid crystal display device, in particular, an OCB type liquid crystal display device having a fast response speed and suitability for moving images, and the liquid crystal display device is thin. It is an object of the present invention to provide a polarizing plate that can contribute to the improvement of the manufacturing process.
Furthermore, an object of the present invention is to provide a liquid crystal display device capable of displaying an image with high display quality, particularly an OCB type liquid crystal display device having a high response speed and suitable for moving images.

The object of the present invention has been achieved by the following [1] to [5].
[1] The following steps:
(1) A step of rubbing the surface of the support or the surface of the alignment film formed on the support;
(2) The process of apply | coating the coating liquid containing a liquid crystal compound on the said rubbed support body or alignment film surface;
(3) The liquid crystal compound layer composed of the applied coating solution is dried at the same time or after being dried, and then the liquid crystal compound is hybrid-aligned at a temperature equal to or higher than the liquid crystal transition temperature, and the alignment is fixed to the optically anisotropic layer. Forming a step;
A method for producing an optical film having an optically anisotropic layer on a support, wherein the rubbing axis θ of the rubbing treatment in the step (2) and the retardation axis φ of the optically anisotropic layer are as follows: The retardation value seen from the normal direction of the optically anisotropic layer produced in the step (3) that satisfies the formula (I) is 27 nm or more, and the thickness of the optically anisotropic layer is 1.8 μm or less. Manufacturing method of optical film:
Formula (I) | θ−φ | <5 °
In the formula, φ represents the retardation axis of the optically anisotropic layer measured with “KOBRA-21ADH” manufactured by Oji Scientific Instruments.
[2] The method for producing an optical film of [1], wherein the liquid crystal compound is a discotic liquid crystal compound.
[3] An optical film produced by the production method of [1] or [2].
[4] A liquid crystal display device having an optical film manufactured by the manufacturing method according to [1] or [2].
[5] The liquid crystal display device according to [4], wherein the display method is an OCB method.

  In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at a wavelength λ, respectively. In the present invention, Re (λ) is a value measured using KOBRA 21ADH (manufactured by Oji Scientific Instruments) with light having a wavelength of λ nm incident in the normal direction of the film. Rth (λ) is light having a wavelength of λ nm from the direction inclined by + 40 ° with respect to the film normal direction with the Re (λ) and slow axis (determined by KOBRA 21ADH) as the tilt axis (rotation axis). And the retardation value measured by making light of wavelength λ nm incident from a direction inclined −40 ° with respect to the film normal direction with the slow axis as the tilt axis (rotation axis). A value calculated by KOBRA 21ADH based on retardation values measured in three directions in total. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of the main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness.

  According to the present invention, a method capable of stably and continuously manufacturing an optical film having an excellent optical compensation function for a liquid crystal display device, particularly an OCB type liquid crystal display device having a high response speed and suitable for moving images. Can be provided. The optical film produced by the production method of the present invention has a good optical compensation function. Moreover, according to the manufacturing method of this invention, the optical film which has a favorable optical function can be manufactured with a roll form.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
(Optical film manufacturing method)
The present invention relates to a method for producing an optical film having an optically anisotropic layer containing a liquid crystal compound fixed in an aligned state on a support.
The method for producing an optical film of the present invention includes the following steps:
(1) A step of rubbing the surface of the support or the surface of the alignment film formed on the support;
(2) The process of apply | coating the coating liquid containing a liquid crystal compound on the support body or alignment film surface, or the said rubbing-processed support body or alignment film surface;
(3) Simultaneously or after drying the liquid crystal compound layer comprising the applied coating solution, the liquid crystal compound is aligned at a temperature equal to or higher than the liquid crystal transition temperature, and the alignment is fixed to form an optically anisotropic layer. Forming step;
including. Moreover, the said process can be performed continuously.

In the production method of the present invention, the rubbing axis θ of the rubbing process in the step (2) and the retardation axis φ of the optically anisotropic layer satisfy the following formula (1), and are produced in the step (3). The retardation value seen from the normal direction of the optically anisotropic layer is 27 nm or more, and the thickness of the optically anisotropic layer is 1.8 μm or less.
Formula (1) | θ−φ | <5 °
In the formula, φ represents the retardation axis of the optically anisotropic layer measured with “KOBRA-21ADH” manufactured by Oji Scientific Instruments.

  According to the production method of the present invention, since the thickness and retardation of the optically anisotropic layer are controlled, the difference between the rubbing axis and the retardation axis is reduced without being affected by external forces such as wind. Therefore, it has an excellent optical compensation function and can be mass-produced stably.

The production method of the present invention is also suitable for producing a roll-shaped optical film. That is,
(1 ′) a step of rubbing the surface of the long support conveyed in the longitudinal direction or the surface of the alignment film formed on the support;
(2) The process of apply | coating the coating liquid containing a liquid crystal compound on the support body or alignment film surface, or the said rubbing-processed support body or alignment film surface;
(3) Simultaneously or after drying the liquid crystal compound layer comprising the applied coating solution, the liquid crystal compound is aligned at a temperature equal to or higher than the liquid crystal transition temperature, and the alignment is fixed to form an optically anisotropic layer. Forming step;
(4) A step of winding the long laminate on which the optically anisotropic layer is formed;
The roll-shaped optical film can be continuously and stably produced by continuously performing the above.

Moreover, the production method of the present invention comprises:
1) In the step (2), a polymerizable liquid crystal compound having a crosslinkable functional group is used as the liquid crystal compound. In the step (3), the coating layer is continuously irradiated with light to polymerize the polymerizable liquid crystal compound. May be cured by fixing the alignment state, and then the step (4) may be continuously performed; and / or 2) When the step (1) is performed, the support or the alignment film may be used. Rubbing with a rubbing roller while removing the surface of the substrate and / or before the step (2), a step of dusting the surface of the support or the alignment film subjected to the rubbing treatment may be performed; And / or 3) Before the step (4), an inspection step of inspecting the formed optically anisotropic layer by continuously measuring the optical properties may be included.
Details of each of these steps are described in JP-A-9-73081.

Hereinafter, each process will be described.
(Step (1))
In the step (1), a rubbing treatment is applied to the surface of the support or the surface of the alignment film formed on the support.

  The rubbing treatment is preferably performed with a rubbing roller. The diameter of the rubbing roller to be used is preferably 100 mm to 500 mm, more preferably 200 mm to 400 mm, from the viewpoints of handling suitability and fabric life. The width of the rubbing roller needs to be wider than the width of the support, and is preferably at least film width × √2. The number of rotations of the rubbing roller is preferably set low from the viewpoint of dust generation, and depending on the orientation of the liquid crystal compound, it is preferably 100 rpm to 1000 rpm, and more preferably 250 rpm to 850 rpm.

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

Even when the optical film to be manufactured is not in the form of a roll, it is preferable from the viewpoint of productivity to perform the rubbing treatment while conveying the support.
The conveyance speed of the support is preferably 10 m / min to 100 m / min, more preferably 15 m / min to 80 m / min, from the viewpoints of productivity and liquid crystal orientation. The conveyance can be performed using various apparatuses conventionally used for film conveyance, and the conveyance method is not particularly limited.

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

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

In order to produce a highly uniform optically anisotropic layer, the surface tension of the coating liquid for forming the optically anisotropic layer is preferably 25 mN / m or less, more preferably 22 mN / m or less. preferable.
In order to realize this low surface tension, a coating liquid for forming an optically anisotropic layer is used in a surfactant or a fluorine compound, particularly a repeating unit corresponding to the monomer (1) below and a monomer (2) below. It is preferable to contain a fluorine-based polymer such as a fluoroaliphatic group-containing copolymer containing a repeating unit corresponding to.
(1) Fluoroaliphatic group-containing monomer represented by the following general formula (3) (2) Poly (oxyalkylene) acrylate and / or poly (oxyalkylene) methacrylate

In the general formula (3), R ² represents a hydrogen atom or a methyl group, X represents an oxygen atom, a sulfur atom or —N (R ³ ) —, p is an integer of 1 to 6, q is 2 or 3 Represents an integer. R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

  The weight average molecular weight of the fluoropolymer added to the coating liquid for forming the optically anisotropic layer is preferably 3000 to 100,000, and more preferably 6,000 to 80,000. Furthermore, the addition amount of the fluorine-based polymer is preferably 0.005 to 8% by mass, and 0.01 to 1% by mass with respect to the coating liquid composition (coating component excluding the solvent) mainly comprising a liquid crystal compound. More preferably, 0.05-0.5 mass% is further more preferable. If the addition amount of the fluorine-based polymer is less than 0.005% by mass, the effect is insufficient, and if it exceeds 8% by mass, the coating film cannot be sufficiently dried, or the performance as an optical film (for example, letter The uniformity of the foundation, etc.).

  Application of the coating liquid for forming the optically anisotropic layer to the rubbing surface is performed by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method). Can be implemented. The coating amount can be appropriately determined based on the desired thickness of the optically anisotropic layer.

  In addition, the liquid crystal compound used for preparing the coating liquid and various materials used as desired will be described later.

(Step (3))
In the step (3), the optically anisotropic layer is formed by fixing the orientation of the liquid crystal compound from the liquid crystal compound layer comprising the applied coating solution. That is, simultaneously or after drying the applied coating solution, the liquid crystal compound of the coating solution is aligned at a temperature equal to or higher than the liquid crystal transition temperature, and the alignment is fixed to produce an optically anisotropic layer. . The liquid crystal compound has a desired orientation by heating during drying or by heating after drying. The drying temperature can be determined in consideration of the boiling point of the solvent used in the coating solution and the materials of the support and the alignment film. The alignment temperature of the liquid crystal compound can be determined according to the liquid crystal phase-solid phase transition temperature of the liquid crystal compound used. When a discotic liquid crystal compound is used as the liquid crystal compound, the alignment temperature is preferably 50 to 300 ° C, more preferably 50 to 170 ° C.

Further, when the liquid crystal compound is in a liquid crystal state, the viscosity of the liquid crystal compound layer is preferably 10 cp to 10000 cp, and more preferably 100 cp to 1000 cp. If the viscosity is too low, it is likely to be affected by the drying air during orientation, and the difference between the rubbing axis and the retardation axis may be large, and very accurate wind speed / direction control is required for continuous production. Become. On the other hand, if the viscosity is high, it is difficult to be affected by the wind, but the alignment of the liquid crystal becomes slow and the productivity is very deteriorated.
The viscosity of the liquid crystal compound layer can be appropriately controlled by the molecular structure of the liquid crystal compound. Moreover, the method of adjusting to a desired viscosity by using an appropriate amount of the above-mentioned additive (especially cellulosic polymer etc.), a gelatinizer, etc. is used preferably.

  Heating can be carried out by blowing hot air at a predetermined temperature or by conveying in a heating chamber maintained at a predetermined temperature.

  The alignment state of the aligned liquid crystal compound is maintained and fixed, and the liquid crystal compound can be fixed when forming the optically anisotropic layer by cooling to a solid phase transition temperature or by a polymerization reaction. .

  In the step (3), it is preferable to simultaneously fix the liquid crystal compound and align the liquid crystal compound. As a method for fixing the alignment of the liquid crystal compound, a photopolymerization initiator or a thermal polymerization initiator is added to a system comprising a monomer having an unsaturated bond and a low molecular liquid crystal, and light or heat is simultaneously generated with the alignment of the low molecular liquid crystal. A method of polymerizing monomers having unsaturated bonds to fix the orientation of low-molecular liquid crystals; fixing the orientation by reacting low-molecular liquid crystals having reactive substituents with a polymer matrix by heat, light or pH change And a method of fixing the alignment by cross-linking low-molecular liquid crystals having reactive substituents in individual liquid crystal domains. However, the method is not limited to these methods, and various known methods are available. Technology can be used.

The polymerization reaction used for fixing the liquid crystal compound includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred. Examples of the thermal polymerization initiator include azo compounds, organic peroxides, inorganic peroxides, sulfinic acids and the like. Details thereof are described in pages 6 to 18 of “Addition Polymerization / Ring-Opening Polymerization” (1983, Kyoritsu Shuppan) edited by the Society of Polymer Sciences, Editorial Committee of Polymer Experiments. Examples of the photopolymerization initiator include benzophenones, acetophenones, benzoins, thioxanthones, and the like. Details of these are described in pages 63 to 147 of “UV curing system” (1989, General Technology Center). Examples of photopolymerization initiators include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US Pat. Description), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970) are included.
The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

It is preferable to use ultraviolet rays for light irradiation for proceeding and fixing the polymerization of the liquid crystal compound. The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, more preferably in the range of 100~1000mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The light irradiation can be carried out by passing the support on which the coating liquid for forming the optically anisotropic layer is applied through a conveyance path in which one or more light sources are arranged at either the top, bottom, or left and right positions. .

  In the case of producing a roll-shaped optical film, the step (4) is performed following the step (3). Before shifting to the step (4), a protective layer can be provided on the optically anisotropic layer produced in the step (3). For example, a protective layer film prepared in advance may be continuously laminated on the surface of a long optically anisotropic layer.

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

  The conditions and apparatuses described in JP-A-9-73081 can be applied to the details of the conditions of each step of the production method of the present invention and the usable apparatus.

The present invention also relates to an optical film produced by the production method.
The optical film produced by the production method of the present invention is an optical film having a support and an optically anisotropic layer formed from a liquid crystal compound on the support. In order to align the liquid crystal compound of the optically anisotropic layer, the support or the surface of the alignment film formed on the support is rubbed.
The optical film of the present invention is an optical film produced by the production method of the present invention. Therefore, the rubbing axis θ applied to the surface of the support or the alignment film and the retardation axis φ of the optically anisotropic layer satisfy the above formula (1), and the letter viewed from the normal direction of the optically anisotropic layer. The foundation value is 27 nm or more, and the thickness is 1.8 μm or less. In the optical film of the present invention, the difference between the rubbing axis θ and the retardation axis φ of the optically anisotropic layer is less than 5 °. Is reduced, and the optical compensation capability is good.

  The optical film of the present invention is preferably produced in a roll state, and may be incorporated into a liquid crystal display device as an optical film after being cut into a desired shape, or used as a protective film for a polarizing plate. It can also be incorporated into the liquid crystal display device after being integrated with other components. It is preferably used for a horizontal alignment mode (particularly a reflection type liquid crystal display device) or a bend alignment mode liquid crystal display device. When the optical film of the present invention is applied to the liquid crystal display device of these modes, the arrangement of the optically anisotropic layer composed of the liquid crystal compound, the support and the polarizing film is very important. Details of the case of using a compound are described in JP-A-11-316378 and can also be applied to embodiments of the present invention.

Hereinafter, each component of the optical film of the present invention will be described in detail.
(Support)
The support used in the present invention is preferably transparent, and specifically, the light transmittance is preferably 80% or more. A transparent polymer film is preferable in consideration of the necessity of being able to be wound into a cylindrical shape when producing a roll-shaped optical film. Examples of the polymer film that can be used as a support include polymer films made of cellulose ester (eg, cellulose acetate, cellulose diacetate), norbornene-based polymer, polymethyl methacrylate, and the like. Commercially available polymers (for norbornene polymers, ARTON (manufactured by Nippon Synthetic Rubber Co., Ltd.) and ZEONEX (manufactured by Nippon Zeon Co., Ltd.) (both are trade names)) may be used. Among these, a film made of a cellulose ester is preferable, and a film made of a lower fatty acid ester of cellulose is more preferable. Lower fatty acid means a fatty acid having 6 or less carbon atoms. Particularly, the number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). A film made of cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate can also be used.

  In addition, even a conventionally known polymer such as polycarbonate or polysulfone, which easily develops birefringence, can exhibit birefringence by modifying the molecule as described in International Publication WO00 / 26705. Can be used as a support in the present invention.

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

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

The Rth retardation value of the support used in the present invention is preferably 40 nm to 400 nm, and the Re retardation value is preferably 0 to 70 nm.
When two optical films of the present invention using a cellulose acetate film as a support are incorporated into a liquid crystal display device, the Rth retardation value of the cellulose acetate film is preferably 40 to 250 nm. On the other hand, when one optical film of the present invention using a cellulose acetate film as a support is incorporated into a liquid crystal display device, the Rth retardation value of the cellulose acetate film is preferably 150 to 400 nm.
In addition, it is preferable that the birefringence ((DELTA) n: nx-ny) of a cellulose acetate film is 0.00025-0.00088. The birefringence Rth in the thickness direction of the cellulose acetate film is preferably 0.00088 to 0.005.

  When a cellulose acetate film is used for the support, it is preferable to contain a retardation increasing agent in the film. Regarding preferred compound examples and production methods thereof, JP-A Nos. 2000-154261 and 2000-1111914 are preferred. It is described in the gazette.

(Optically anisotropic layer)
The optical film of the present invention has at least one optically anisotropic layer formed from a liquid crystal compound. The optically anisotropic layer may be formed directly on the surface of the support, or may be formed on the alignment film by forming an alignment film on the support.
Examples of the liquid crystal compound used for forming the optically anisotropic layer include a rod-like liquid crystal compound and a discotic liquid crystal compound. The rod-like liquid crystal compound and the discotic liquid crystal compound may be a high-molecular liquid crystal or a low-molecular liquid crystal, and further include those in which the low-molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity.

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

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

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

The discotic liquid crystal compound includes a compound having liquid crystallinity in which a linear alkyl group, an alkoxy group, or a substituted benzoyloxy group is radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule Is also included. The molecule or the assembly of molecules is preferably a compound that has rotational symmetry and can give a certain orientation.
When an optically anisotropic layer is formed from a discotic liquid crystal compound, the compound finally contained in the optically anisotropic layer no longer needs to exhibit liquid crystallinity. For example, a low molecular discotic liquid crystal compound has a group that reacts with heat or light, and the group reacts with heat or light to polymerize or crosslink to increase the molecular weight. Is formed, the compound contained in the optically anisotropic layer may no longer have liquid crystallinity. Preferred examples of the discotic liquid crystal compound are described in JP-A-8-50206. The polymerization of discotic liquid crystal compounds is described in JP-A-8-27284.

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

  An example of the disk-shaped core (D) is shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).

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

Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (Q). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group).
L1: -AL-CO-O-AL-
L2: -AL-CO-O-AL-O-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L6: -CO-AR-O-AL-O-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-O-CO-

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

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

In the hybrid alignment, the angle between the molecular symmetry axis of the liquid crystal compound and the surface of the support increases or decreases in the depth direction of the optically anisotropic layer and with an increase in the distance from the surface of the support. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction.
Even if the angle includes a region where the angle does not change, the angle only needs to increase or decrease as a whole. Furthermore, it is preferable that the angle changes continuously.

  The average direction of the molecular symmetry axis of the liquid crystal compound can be generally adjusted by selecting a liquid crystal compound or an alignment film material or by selecting a rubbing treatment method. Further, the molecular symmetry axis direction of the liquid crystal compound on the surface side (air side) can be generally adjusted by selecting the liquid crystal compound or the type of additive used together with the liquid crystal compound. Examples of the additive used together with the liquid crystal compound include a plasticizer, a surfactant, a polymerizable monomer and a polymer. Similar to the above, the degree of change in the orientation direction of the molecular symmetry axis can be adjusted by selecting the liquid crystal compound and the additive.

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

When a discotic liquid crystal compound is used as the liquid crystal compound, it is preferable to use a polymer that has a certain degree of compatibility with the discotic liquid crystal compound and can change the tilt angle of the discotic liquid crystal compound.
A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose and cellulose acetate butyrate. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, and in the range of 0.1 to 8% by mass with respect to the discotic liquid crystal compound so as not to inhibit the orientation of the discotic liquid crystal compound. It is more preferable that it is in the range of 0.1 to 5% by mass.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystal compound is preferably 50 to 300 ° C, more preferably 50 to 170 ° C.

  The thickness of the optically anisotropic layer is preferably 0.1 to 1.8 μm, more preferably 0.1 to 1.5 μm, and most preferably 0.1 to 1.0 μm. preferable. When the thickness is greater than 1.8 μm, the deviation of the retardation axis due to disturbance increases when aligning the liquid crystal compound, so that the value of | θ−φ | increases and the performance as a liquid crystal display device deteriorates.

(Alignment film)
The optical film of the present invention may have an alignment film between the support and the optically anisotropic layer.
In this invention, when it has the said alignment film, it is preferable that it is a layer which consists of a bridge | crosslinked polymer. As the polymer used for the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. The alignment film is formed by reacting a polymer having a functional group or a polymer having a functional group introduced therein with light, heat, pH change, or the like, or a highly reactive compound. Can be formed by introducing a linking group derived from a cross-linking agent between polymers to cross-link between the polymers.

The alignment film composed of a crosslinked polymer can be usually formed by applying a coating liquid containing the polymer or a mixture of a polymer and a crosslinking agent on a support, followed by heating or the like.
In the rubbing step described above, it is preferable to increase the degree of crosslinking in order to suppress dust generation in the alignment film. A value (1- (Ma / Mb)) obtained by subtracting 1 from the ratio (Ma / Mb) of the amount (Ma) of the crosslinking agent remaining after crosslinking to the amount (Mb) of the crosslinking agent added to the coating solution. When Mb)) is defined as the degree of crosslinking, the degree of crosslinking is preferably 50% to 100%, more preferably 65% to 100%, and most preferably 75% to 100%.

  In the present invention, the polymer used for the alignment film may be either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent. Of course, a polymer having both functions can also be used. Examples of the polymer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol acrylamide), styrene / vinyl toluene copolymer. , Polymers such as chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene and polycarbonate, and A compound such as a silane coupling agent can be exemplified. Examples of preferred polymers are water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol and modified polyvinyl alcohol, with gelatin, polyvinyl alcohol and modified polyvinyl alcohol being preferred, especially polyvinyl alcohol and Mention may be made of modified polyvinyl alcohol.

Among the above polymers, polyvinyl alcohol or modified polyvinyl alcohol is preferable. The polyvinyl alcohol has, for example, a saponification degree of 70 to 100%, generally a saponification degree of 80 to 100%, and more preferably a saponification degree of 85 to 95%. As a polymerization degree, the range of 100-3000 is preferable. Examples of the modified polyvinyl alcohol include those modified by copolymerization (for example, COONa, Si (OX) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ COO, SO ₃ , Na, C ₁₂ H ₂₅ Etc.), modified by chain transfer (for example, COONa, SH, C ₁₂ H ₂₅ etc. are introduced as modifying groups), modified by block polymerization (modified groups, for example, COOH, CONH ₂ , COOR, C ₆ H _5, etc. are introduced). As a polymerization degree, the range of 100-3000 is preferable. Among these, unmodified or modified polyvinyl alcohol having a saponification degree of 80 to 100% is preferable, and unmodified or alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% is more preferable.

  The modified polyvinyl alcohol used for the alignment film is preferably a reaction product of a compound represented by the following general formula (1) and polyvinyl alcohol.

R ¹ represents an unsubstituted alkyl group, or an alkyl group substituted with an acrylolyl group, a methacryloyl group or an epoxy group, W represents a halogen atom, an alkyl group or an alkoxy group, X represents an active ester, an acid anhydride Or, it represents an atomic group necessary for forming an acid halide, l represents 0 or 1, and n represents an integer of 0 to 4.

  Moreover, as the modified polyvinyl alcohol used for the alignment film, a reaction product of a compound represented by the following general formula (2) and polyvinyl alcohol is also preferable.

X ¹ represents an atomic group necessary for forming an active ester, acid anhydride or acid halide, and m represents an integer of 2 to 24.

As the polyvinyl alcohol used for reacting with the compounds represented by the general formula (1) and the general formula (2), the unmodified polyvinyl alcohol and the copolymer-modified one, that is, modified by chain transfer. And modified products of polyvinyl alcohol such as those modified by block polymerization. Preferred examples of the specific modified polyvinyl alcohol are described in detail in JP-A-8-338913.
When using a hydrophilic polymer such as polyvinyl alcohol for the alignment film, it is preferable to control the moisture content from the viewpoint of the degree of hardening, preferably 0.4% to 2.5%, 0.6% More preferably, it is -1.6%. The water content can be measured with a commercially available Karl Fischer moisture content measuring device.
The alignment film preferably has a thickness of 10 μm or less.

(Liquid crystal display device)
The present invention also relates to a liquid crystal display device having an optical film manufactured by the manufacturing method of the present invention. The optical film is advantageously used in liquid crystal display devices, in particular, TN mode, OCB mode liquid crystal display devices, and ECB mode reflective liquid crystal display devices.
The transmissive liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates.
One optical film is disposed between the liquid crystal cell and one polarizing plate, or two optical films are disposed between the liquid crystal cell and both polarizing plates. When an optical film is used as a protective film for a polarizing plate, the polarizing plate also serves as an optical film, which is preferable in terms of thinning and weight reduction of the liquid crystal display device.

  In a liquid crystal cell of a TN liquid crystal display device, rod-like liquid crystalline molecules are substantially horizontally aligned when no voltage is applied, and twisted to 60 to 120 °. TN liquid crystal cells are most frequently used as black and white and color liquid crystal display devices, and are described in many documents.

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

  The liquid crystal display device of the ECB system is a liquid crystal having the longest known configuration using a horizontal alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned in substantially the same direction at the top and bottom of the liquid crystal cell. It is a display device.

  Hereinafter, the present invention will be described more specifically with reference to examples. The materials, reagents, ratios, operations and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

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

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

In another mixing tank, 16 parts by mass of the following retardation increasing agent, 80 parts by mass of methylene chloride and 20 parts by mass of methanol were added and stirred while heating to prepare a retardation increasing agent solution.
The dope was prepared by mixing 464 parts by mass of the cellulose acetate solution having the above composition with 36 parts by mass of the retardation increasing agent solution and 1.1 parts by mass of silica fine particles (R972, manufactured by Irosil). The addition amount of the retardation increasing agent was 5.0 parts by mass with respect to 100 parts by mass of cellulose acetate. Moreover, the addition amount of silica fine particles was 0.15 mass part with respect to 100 mass parts of cellulose acetate.

The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., it was dried for 1 minute, peeled off, and then stretched 28% in the width direction using a tenter with a drying air of 140 ° C. Then, it dried for 20 minutes with 135 degreeC dry air, and manufactured the support body (PK-1) whose residual solvent amount is 0.3 mass%.
The obtained support (PK-1) had a width of 1340 mm and a thickness of 92 μm. The retardation value (Re) at a wavelength of 548 nm was measured and found to be 38 nm. Further, the retardation value (Rth) at a wavelength of 548 nm was measured and found to be 175 nm.
The obtained support (PK-1) had a width of 1340 mm and a thickness of 92 μm.
A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is formed on the band surface side of the produced support (PK-1). Was applied at 10 cc / m ² and kept at a temperature of about 40 ° C. for 30 seconds. The alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second. The contact angle of PK-1 with respect to pure water was found to be 42 °.

(Preparation of alignment film)
On this PK-1 (alkali-treated surface), an alignment film coating solution having the following composition was applied at 28 ml / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

(Orientation film coating solution composition)
Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight Citrate ester (AS3 manufactured by Sankyo Chemical) 0.35 parts by weight

(Rubbing process)
PK-1 is transported at a speed of 20 m / min, a rubbing roll (300 mm diameter) is set so as to be rubbed at 45 ° with respect to the longitudinal direction, and rotated at 500 rpm. The rubbing process was given to. The contact length between the rubbing roll and PK-1 was set to 18 mm.

(Formation of optically anisotropic layer)
On the alignment film, 41.01 kg of the following discotic liquid crystal compound, 4.06 kg of ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB531-1, yeast) Manchemical Co., Ltd.) 0.35 Kg, Photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 1.35 Kg, Sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 0.45 Kg, Citrate (Three Kyo Chemical's AS3) 0.15g of fluoroaliphatic group-containing copolymer (Megafac F780, Dainippon Ink Co., Ltd.) was added to the coating solution in which 0.45Kg was dissolved in 102Kg of methyl ethyl ketone to prepare the coating solution. did.

  A # 3.0 wire bar was rotated at 391 revolutions / minute in the same direction as the film conveyance direction, and continuously applied to the PK-1 alignment film surface conveyed at 20 m / minute.

  In the process of continuously heating from room temperature to 100 ° C., the solvent was dried, and then heated in a drying zone at 130 ° C. for about 90 seconds to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 50 ° C., and an ultraviolet ray irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) is used to emit ultraviolet rays having an illuminance of 800 mW while the film surface temperature is about 70 ° C. Irradiated for 2 seconds, the crosslinking reaction was advanced, and the discotic liquid crystal compound was fixed to the orientation. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical film (KH-1) was produced.

A part of the produced roll-shaped optical film (KH-1) was cut out and used as a sample to measure optical characteristics. The Re retardation value of the optically anisotropic layer measured at a wavelength of 548 nm was 33 nm. In addition, the angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface continuously changed in the depth direction of the layer, and was 29 ° on average. Further, only the optically anisotropic layer was peeled from the sample, and the direction of the retardation axis of the optically anisotropic layer was measured with “KOBRA-21ADH” manufactured by Oji Scientific Instruments Co., Ltd. ) Was 45 ° with respect to the longitudinal direction.
Furthermore, when the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical film was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.
Moreover, it was 1.39 micrometers when the thickness of the optically anisotropic layer was measured with the interference film thickness measuring apparatus (OMRON Co., Ltd. make, Z5FM-C200).

(Preparation of polarizing plate)
A PVA film (thickness: 80 μm, width: 2500 mm) having an average polymerization degree of 1700 and a saponification degree of 99.5 mol% was vertically uniaxially stretched 8 times in warm water at 40 ° C., and the iodine 0.2 g / l and potassium iodide 60 g / l as they were. was immersed in an aqueous solution of 1 at 30 ° C. for 5 minutes, and then immersed in an aqueous solution of boric acid 100 g / l and potassium iodide 30 g / l. At this time, the film width was 1300 mm and the thickness was 17 μm.
Further, this film was immersed in a water-washed layer at 20 ° C. for 10 seconds, and then immersed in an aqueous solution of iodine 0.1 g / l and potassium iodide 20 g / l at 30 ° C. for 15 seconds. It dried for a time and obtained the iodine type polarizing film (HF-1).

Using the polyvinyl alcohol-based adhesive, the support (PK-1) surface of the produced optical film (KH-1) was attached to one side of the polarizing film (HF-1). Moreover, the saponification process was performed to the 80-micrometer-thick triacetylcellulose film (TD-80U: Fuji Photo Film Co., Ltd. product), and it affixed on the other side of the polarizing film using the polyvinyl alcohol-type adhesive agent.
The longitudinal direction of the polarizing film, the longitudinal direction of the support (PK-1), and the longitudinal direction of the commercially available triacetyl cellulose film were all arranged in parallel. Thus, a polarizing plate (HB-1BR) having an optical film on one side and a commercially available triacetyl cellulose film on the other side was produced.

Separately, it was attached to one side of the polarizing film (HF-1) on the support (PK-1) surface of the produced optical film (KH-1) using a polyvinyl alcohol-based adhesive. Moreover, the saponification process was performed to the film (Fuji Film CV-UA, Fuji Photo Film Co., Ltd. product) with a commercially available antireflection function, and it affixed on the other side of the polarizing film using the polyvinyl alcohol-type adhesive agent.
The longitudinal direction of the polarizer, the longitudinal direction of the support (PK-1), and the longitudinal direction of the film with antireflection function were all arranged in parallel. In this manner, a polarizing plate (HB-1BF) having an optical film on one side and a commercially available film with an antireflection function on the other side was produced.

(Preparation of bend alignment liquid crystal cell)
A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and the alignment film was rubbed. The obtained two glass substrates were faced to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 4.5 μm. A liquid crystal compound having a Δn of 0.1396 (ZLI1132, manufactured by Merck & Co., Inc.) was injected into the cell gap to prepare a bend alignment liquid crystal cell. The size of the liquid crystal cell was 20 inches.
A polarizing plate (HB-1BF) having an optical film on one side and a commercially available anti-reflection film on the other side is placed on the viewing side, the optical film on one side, and the other side on the other side. Each of the polarizing plates (HB-1BR) having a triacetylcellulose film was attached to the backlight side. The liquid crystal compound layer of the polarizing plate faces the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the liquid crystal compound layer facing the liquid crystal cell are arranged to be antiparallel.

A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally white mode of 2V white display and 5V black display was set. Using the measurement ratio (EZ-Contrast 160D, manufactured by ELDIM) with the transmittance ratio (white display / black display) as the contrast ratio, the viewing angle can be adjusted in 8 steps from black display (L1) to white display (L8). It was measured. As a result, the range in which the contrast ratio was 10 or more and black gradation inversion (inversion between L1 and L2) was 80 ° or more in both the top and bottom and the left and right.
Further, when the front contrast (CR: luminance of white display / brightness of black display) was obtained, a high contrast with 460 was obtained.

[Example 2]
After applying the optically anisotropic layer, an optical film (KH-2) was produced in the same manner as in Example 1 except that, when heated at 130 ° C. for 90 seconds, a wind of 3 m / second was applied in parallel to the transport direction. The film thickness was 1.4 μm, and | θ−φ | was 4 °. Further, Table 1 shows the results of mounting and mounting on the bend alignment liquid crystal cell of Example 1.

[Comparative Example 1]
After applying the optically anisotropic layer, an optical film (KH-H1) was produced in the same manner as in Example 1 except that, when heated at 130 ° C. for 90 seconds, a wind of 5 m / second was applied in parallel to the transport direction. The film thickness was 1.4 μm, and | θ−φ | was 6 °. Further, Table 1 shows the results of mounting and mounting on the bend alignment liquid crystal cell of Example 1.

[Comparative Example 2]
After applying the optically anisotropic layer, an optical film (KH-H2) was produced in the same manner as in Example 1 except that, when heated at 130 ° C. for 90 seconds, a wind of 7 m / second was applied in parallel to the transport direction. The film thickness was 1.4 μm and | θ−φ | was 9 °. Further, Table 1 shows the results of mounting and mounting on the bend alignment liquid crystal cell of Example 1.

[Comparative Example 3]
Example 1 except that a # 4.0 wire bar was used when applying the optically anisotropic layer, and that a 3 m / second wind was applied in parallel to the conveying direction when heated at 130 ° C. for 90 seconds. When an optical film (KH-H3) was produced in the same manner as described above, the film thickness was 1.9 μm and | θ−φ | was 6 °. Further, Table 1 shows the results of mounting and mounting on the bend alignment liquid crystal cell of Example 1.

  Thus, when | θ−φ | <5 °, the viewing angle, contrast, and color change are all good. However, when | θ−φ |> 5 °, the viewing angle and contrast are lowered, and the color tone changes. It was confirmed that the change became large.

Claims (5)

The following steps:
(1) A step of rubbing the surface of the support or the surface of the alignment film formed on the support;
(2) The process of apply | coating the coating liquid containing a liquid crystal compound on the said rubbed support body or alignment film surface;
(3) The liquid crystal compound layer composed of the applied coating solution is dried at the same time or after being dried, and then the liquid crystal compound is hybrid-aligned at a temperature equal to or higher than the liquid crystal transition temperature, and the alignment is fixed to the optically anisotropic layer. Forming a step;
A method for producing an optical film having an optically anisotropic layer on a support containing, wherein the rubbing axis θ of the rubbing treatment in the step (2) and the retardation axis φ of the optically anisotropic layer are as follows: The retardation value seen from the normal direction of the optically anisotropic layer produced in the step (3) that satisfies the formula (I) is 27 nm or more, and the thickness of the optically anisotropic layer is 1.8 μm or less. Manufacturing method of optical film:
Formula (I) | θ−φ | <5 °
In the formula, φ represents the retardation axis of the optically anisotropic layer measured with “KOBRA-21ADH” manufactured by Oji Scientific Instruments. The method for producing an optical film according to claim 1, wherein the liquid crystal compound is a discotic liquid crystal compound. An optical film produced by the production method according to claim 1. The liquid crystal display device which has an optical film manufactured with the manufacturing method of Claim 1 or 2. The liquid crystal display device according to claim 4, wherein the display method is an OCB method.