JP2006251642A - Optical film, polarizing plate, and liquid crystal display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film that optically compensates a liquid crystal cell, in particular, induces no irregularity or less irregularity even when it is used for a large liquid crystal display apparatus, and that contributes to the display of an image of high display quality, and to provide a polarizing plate and a liquid crystal display apparatus equipped with the optical film excellent in the characteristics. <P>SOLUTION: The optical film has an optical anisotropic layer formed from a composition containing a liquid crystal compound on a support, and is characterized in that: the optical anisotropic layer contains at least one kind of fluoro-aliphatic group-containing polymer having one or more kinds of hydrophilic groups selected from a group consisting of a carboxyl group (-COOH), sulfo group (-SO<SB>3</SB>H), phosphono group [-PO(OH)<SB>2</SB>] and salts of these; and the fluoro-aliphatic group-containing polymer is a polymer obtained by polymerization using a chain transfer agent having one or more kinds of hydrophilic groups selected from a group consisting of a carboxyl group (-COOH), sulfo group (-SO<SB>3</SB>H), phosphono group [-PO(OH)<SB>2</SB>] and salts of these. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical film having an optically anisotropic layer in which a liquid crystal compound is aligned and fixed, a polarizing plate provided with the optical film, and a liquid crystal display device.

  Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. Conventionally, stretched birefringent films have been used as optical compensation sheets. In recent years, it has been proposed to use an optical compensation sheet having an optically anisotropic layer made of a discotic liquid crystalline compound on a transparent support instead of a stretched birefringent film. This optically anisotropic layer is usually formed by applying a discotic liquid crystal composition containing a discotic liquid crystal compound on an alignment film, and heating it at a temperature higher than the alignment temperature to align the discotic liquid crystal compound, It is formed by fixing its orientation state. In general, the discotic liquid crystalline compound has a large birefringence and various alignment forms. By using a discotic liquid crystalline compound, it has become possible to realize optical properties that cannot be obtained with conventional stretched birefringent films.

  On the other hand, since the discotic liquid crystalline compound has various alignment forms, it is necessary to control the alignment of the discotic liquid crystalline compound in the optically anisotropic layer in order to express desired optical characteristics. As a method for controlling the discotic liquid crystalline compound to a horizontal alignment state having an average tilt angle of less than 5 degrees, a cellulose lower fatty acid ester, a fluorine-containing surfactant or a 1,3,5-triazine ring is added to the discotic liquid crystalline compound. A method of adding a compound having the above has been proposed (see, for example, Patent Document 1). In addition, there is a method in which a compound having a fluorine-substituted alkyl group and a hydrophilic group (a sulfo group is bonded to a benzene ring through a linking group) is added to the optically anisotropic layer to control the tilt angle of the discotic liquid crystalline compound. It has been proposed (see, for example, Patent Document 2). Furthermore, a method for controlling the orientation of the liquid crystalline compound by using a hydrophobic excluded volume effect compound in combination with the optically anisotropic layer has been proposed (see, for example, Patent Document 3). However, no mention is made of the effect of the compound that effectively promotes the hybrid alignment of the liquid crystal compound and the method of using the compound.

  As another method for controlling the alignment of the liquid crystal compound, a method using an alignment film (interface treatment) is known. However, it is difficult to uniformly align the liquid crystalline compound from the alignment film interface to the air interface (monodomain alignment) only with the regulating force of the alignment film, and defects such as schlieren are likely to remain. In particular, when the aging time is shortened in order to improve productivity, the occurrence of schlieren defects becomes significant. When a schlieren defect occurs in the optically anisotropic layer, there is a problem that light scattering occurs and optical properties are impaired.

In the prior art, an optical compensation sheet has been developed mainly assuming a small or medium-sized liquid crystal display device of 15 inches or less. However, recently, it is also necessary to assume a liquid crystal display device having a large size of 17 inches or more and high brightness. When a conventional optical compensation sheet was attached as a protective film to a polarizing plate of a large liquid crystal display device, it was found that unevenness occurred on the panel. This defect is not so conspicuous in a small-sized or medium-sized liquid crystal display device, but it is necessary to further develop an optical film that copes with light leakage unevenness in response to an increase in size and brightness.
As a technique for improving unevenness, a method of incorporating a leveling agent into a polymerizable liquid crystal has been disclosed (for example, see Patent Document 4). However, it has been found that this method is effective only when the polymerizable liquid crystal is homogeneously aligned, and cannot be applied to complicated alignment such as hybrid alignment as in the present invention.

JP 11-352328 A (pages 9-21) JP 2001-330725 A (page 7-10) JP 2002-20363 A (page 3-21) JP-A-11-148080

An object of the present invention is to provide an optical film for optically compensating a liquid crystal cell. In particular, an object of the present invention is to provide an optical film that contributes to displaying an image with high display quality without causing unevenness or reducing unevenness even when applied to a large liquid crystal display device.
Another object of the present invention is to provide a polarizing plate and a liquid crystal display device provided with an optical film having excellent properties.

The object of the present invention is achieved by the following optical film, the following polarizing plate provided with the optical film, and a liquid crystal display device composed thereof.
[1] An optical film having an optically anisotropic layer formed from a composition containing a liquid crystal compound on a support, the optically anisotropic layer having a carboxyl group (—COOH), a sulfo group (— SO ₃ H), a phosphono group [—PO (OH) ₂ ] and a fluoroaliphatic group-containing polymer having at least one hydrophilic group selected from the group consisting of salts thereof, and the fluoroaliphatic group Chain transfer in which the polymer contains one or more hydrophilic groups selected from the group consisting of carboxyl group (—COOH), sulfo group (—SO ₃ H), phosphono group [—PO (OH) ₂ ] and salts thereof An optical film which is a polymer obtained by polymerization using an agent.
[2] The optical film of [1], wherein the fluoroaliphatic group-containing polymer includes a repeating unit derived from a fluoroaliphatic group-containing monomer represented by the following general formula [1]:

一般式［１］においてＲ¹は水素原子またはメチル基を表し、Ｘは酸素原子、イオウ原子または−Ｎ（Ｒ²）−を表し、Ｚは水素原子またはフッ素原子を表し、ｍは１以上６以下の整数、ｎは２〜４の整数を表し、Ｒ²は水素原子または炭素数１〜４のアルキル基を表す。

In the general formula [1], R ¹ represents a hydrogen atom or a methyl group, X represents an oxygen atom, a sulfur atom or —N (R ² ) —, Z represents a hydrogen atom or a fluorine atom, and m represents 1 or more and 6 The following integers, n represents an integer of 2 to 4, and R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[3] The optical film of [1] or [2], wherein the fluoroaliphatic group-containing polymer includes a repeating unit derived from a monomer represented by the following general formula [2]:

上記一般式［２］において、Ｒ⁶は水素原子またはメチル基を表し、Ｚは２価の連結基を表し、Ｒ⁷は置換基を有してもよいポリ（アルキレンオキシ）基または置換基を有してもよい炭素数１以上２０以下の直鎖、分岐鎖または環状のアルキル基を表す。

In the general formula [2], R ⁶ represents a hydrogen atom or a methyl group, Z represents a divalent linking group, and R ⁷ represents a poly (alkyleneoxy) group or a substituent which may have a substituent. A linear, branched or cyclic alkyl group having 1 to 20 carbon atoms which may be present.

[4] The optical film according to any one of [1] to [3], wherein the liquid crystal compound is a discotic compound.
[5] An optical film having an optically anisotropic layer formed from a composition containing a liquid crystal compound on a support, the optically anisotropic layer comprising a carboxyl group (—COOH), a sulfo group ( -SO ₃ H), a phosphono group [—PO (OH) ₂ ], and one or more hydrophilic groups selected from the group consisting of salts thereof via a divalent group containing at least a thioether bond (—S—) An optical film containing at least one fluoroaliphatic group-containing polymer bonded to the end of the main chain.
[6] A polarizing plate having the optical film of any one of [1] to [5] and a polarizer.
[7] A liquid crystal display device having the polarizing plate according to [6].

In the present specification, the in-plane retardation Re and the thickness direction retardation Rth of various optical members such as an optically anisotropic layer and an optical film are values measured by the following methods.
Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) by making light of wavelength λ nm incident in the normal direction of the film. Rth was measured by making light having a wavelength λ nm incident from a direction inclined + 40 ° with respect to the normal direction of the film with the slow axis in the plane (determined by KOBRA 21ADH) as the tilt axis (rotation axis). A retardation value and a retardation value measured by making light having a wavelength λ nm incident from a direction inclined −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH is calculated based on the retardation value measured in the direction. 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 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.

  In the present invention, the liquid crystalline compound is oriented in the presence of a fluoroaliphatic group-containing polymer having a predetermined hydrophilic group, and fixed in that state to form an optically anisotropic layer, thereby providing an excellent optical compensation capability. The optical film which has this is provided. That is, according to the present invention, even when applied to an optical film for optically compensating a liquid crystal cell, particularly a large liquid crystal display device, it contributes to display an image with high display quality without causing unevenness. An optical film can be provided. In addition, according to the present invention, it is possible to provide a polarizing plate provided with an optical film excellent in the above characteristics and a liquid crystal display device capable of displaying an image with high display quality with little or no unevenness.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail. In addition, the numerical range represented using "to" in this specification means the range which includes the numerical value described before and behind "to" as a lower limit and an upper limit, or an upper limit and a lower limit.
[Optical film]
The optical film of the present invention comprises at least one liquid crystalline compound and a group consisting of a carboxyl group (—COOH), a sulfo group (—SO ₃ H), a phosphono group [—PO (OH) ₂ ], and salts thereof. It has an optically anisotropic layer formed from a composition containing at least one fluoroaliphatic group-containing polymer having at least one selected hydrophilic group at the main chain end. The fluoroaliphatic group-containing polymer contributes to improving the applicability of the composition, and can reduce repelling and unevenness when the composition is applied to a support. In addition, by aligning the molecules of the liquid crystal compound in the presence of the fluoroaliphatic group-containing polymer, the liquid crystal compound is stably in a desired alignment state, for example, in the case of a discotic liquid crystal compound, it is stably in the hybrid alignment state. To contribute. As a result, the liquid crystal display device to which the optical film of the present invention and the polarizing plate having the optical film are applied can display an image with high or high display quality even when the image is large, with little or no unevenness in the image. it can.

Hereinafter, the fluoroaliphatic group-containing polymer that may be used in the present invention (sometimes abbreviated as “fluorine polymer”) will be described in detail.
The fluoropolymer mainly contains at least one hydrophilic group selected from the group consisting of a carboxyl group (—COOH), a sulfo group (—SO ₃ H), a phosphono group [—PO (OH) ₂ ] and salts thereof. At the chain end. More preferably, the hydrophilic group interacts with the end of the main chain of the fluoropolymer and is linked by a covalent bond. Among them, it is preferable to use a fluorine-based polymer obtained by polymerization using a chain transfer agent having a hydrophilic group, and a fluorine-based polymer obtained by polymerization using a chain transfer agent having a carboxyl group (—COOH). Is more preferable.

  The polymerization method of the fluorine-based polymer is not particularly limited, and for example, a polymerization method using a vinyl group such as cationic polymerization, radical polymerization, or anionic polymerization can be employed. Polymerization is particularly preferred in that it can be used for general purposes. As the polymerization initiator for radical polymerization, known compounds such as radical thermal polymerization initiators and radical photopolymerization initiators can be used, and it is particularly preferable to use radical thermal polymerization initiators. Here, the radical thermal polymerization initiator is a compound that generates radicals by heating to a decomposition temperature or higher. Examples of such radical thermal polymerization initiators include diacyl peroxide (acetyl peroxide, benzoyl peroxide, etc.), ketone peroxide (methyl ethyl ketone peroxide, cyclohexanone peroxide, etc.), hydroperoxide (hydrogen peroxide, tert. -Butyl hydroxide, cumene hydroperoxide, etc.), dialkyl peroxides (di-tert-butyl peroxide, dicumyl peroxide, dilauroyl peroxide, etc.), peroxyesters (tert-butyl peroxyacetate, tert) -Butyl peroxypivalate, etc.), azo compounds (azobisisobutyronitrile, azobisisovaleronitrile, etc.), persulfates (ammonium persulfate, sodium persulfate) And potassium persulfate) and the like. Such radical thermal polymerization initiators can be used singly or in combination of two or more.

As described above, it is more preferable to use a chain transfer agent when producing the fluoropolymer. A chain transfer agent having at least one hydrophilic group selected from the group consisting of a carboxyl group (—COOH), a sulfo group (—SO ₃ H), a phosphono group [—PO (OH) ₂ ] and salts thereof is preferable. A chain transfer agent having a carboxyl group (—COOH) is most preferred. Examples of the chain transfer agent include mercaptans (for example, mercaptoacetic acid, octyl mercaptan, decyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, octadecyl mercaptan, thiophenol, p-nonylthiophenol, etc.), polyhalogenated alkyls (for example, Carbon tetrachloride, chloroform, 1,1,1-trichloroethane, 1,1,1-tribromooctane, etc.) and low-activity monomers (α-methylstyrene, α-methylstyrene dimer, etc.) can be used. However, mercaptans are preferred. These chain transfer agents may be present in the system simultaneously with the monomer, and the addition method is not particularly limited. It may be added after being dissolved in the monomer, or may be added separately from the monomer.

For example, when a mercaptan having a hydrophilic group is used as a chain transfer agent, the fluorine-based polymer is a divalent group containing a thioether group derived from a chain transfer agent * -S-R-** (where R is a substituted group). Or a polymer via an unsubstituted alkylene group (preferably a C _1-15 alkylene group), an arylene group or a heterocyclic group, bonded to the polymer backbone with * and bonded to a hydrophilic group with ** The main chain and the hydrophilic group are bonded.

Specific examples of the chain transfer agent having at least one selected from a carboxyl group (—COOH), a sulfo group (—SO ₃ H), a phosphono group [—PO (OH) ₂ ] and a salt thereof usable in the present invention. Although listed below, the present invention is not limited by the following specific examples.

  These compounds can be synthesized, for example, by the method described in US Pat. No. 2,504,030.

  The fluoropolymer preferably has a repeating unit derived from a fluoromonomer represented by the following general formula [1].

In the general formula [1], R ¹ represents a hydrogen atom or a methyl group, X represents an oxygen atom, a sulfur atom or —N (R ² ) — (R ² is a hydrogen atom or an alkyl having 1 to 4 carbon atoms). Represents a group, preferably a hydrogen atom or a methyl group), Z represents a hydrogen atom or a fluorine atom, m represents an integer of 1 to 6, and n represents an integer of 2 to 4.

  X is preferably an oxygen atom, Z is preferably a hydrogen atom, m is preferably 1 or 2, n is preferably 3 or 4, and a mixture thereof may be used.

  Specific examples of monomers that can be used in the production of the fluoropolymer usable in the present invention are listed below, but the present invention is not limited by the following specific examples.

  The fluoropolymer may contain a repeating unit derived from a monomer represented by the following general formula [2].

In the general formula [2], R ⁶ represents a hydrogen atom or a methyl group, Z represents a divalent linking group, and R ⁷ represents a poly (alkyleneoxy) group or a substituent which may have a substituent. A linear, branched or cyclic alkyl group having 1 to 20 carbon atoms which may be present. The divalent linking group represented by Z is preferably an oxygen atom, a sulfur atom, or —N (R ⁵ ) —. Here, R ⁵ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, or butyl. R ⁵ is more preferably a hydrogen atom or methyl. Z is particularly preferably an oxygen atom, —NH—, or —N (CH ₃ ) —.

In the above general formula [2], the poly (alkyleneoxy) group can be represented by (RO) x, and R is an alkylene group having 2 to 4 carbon atoms, such as —CH ₂ CH ₂ —, —CH _2. It is preferably CH ₂ CH ₂ —, —CH (CH ₃ ) CH ₂ —, or —CH (CH ₃ ) CH (CH ₃ ) —.
The alkyleneoxy units in the poly (alkyleneoxy) group may be the same in all units such as poly (propyleneoxy), and two or more different alkyleneoxy units are randomly distributed. (For example, a linear propyleneoxy unit, a branched propyleneoxy unit and an ethyleneoxy unit are randomly distributed), or a combination of two or more different alkyleneoxy unit blocks ( For example, a linear or branched block of propyleneoxy units and a block of ethyleneoxy units may be combined).

  In this poly (alkyleneoxy) chain, a plurality of poly (alkyleneoxy) units are one or more linking groups (for example, -CONH-Ph-NHCO-, -S-, etc., where Ph represents a phenylene group) ) Can be included. When the linking group has a valence of 3 or more, a branched alkyleneoxy unit can be obtained thereby. When this copolymer is used in the present invention, the molecular weight of the poly (alkyleneoxy) group is suitably from 250 to 3,000.

Examples of the linear, branched or cyclic alkyl group having 1 to 20 carbon atoms represented by R ⁷ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, which may be linear or branched, Heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, octadecyl group, eicosanyl group, etc., and also monocyclic cycloalkyl groups such as cyclohexyl group, cycloheptyl group and the like A polycyclic cycloalkyl group such as a bicycloheptyl group, a bicyclodecyl group, a tricycloundecyl group, a tetracyclododecyl group, an adamantyl group, a norbornyl group, or a tetracyclodecyl group is preferably used.

Examples of the substituent of the poly (alkyleneoxy) group or alkyl group represented by R ⁷ include a hydroxyl group, an alkylcarbonyl group, an arylcarbonyl group, an alkylcarbonyloxy group, a carboxyl group, an alkyl ether group, an aryl ether group, a fluorine atom, Examples include, but are not limited to, halogen atoms such as chlorine atom and bromine atom, nitro group, cyano group and amino group.

  The monomer represented by the general formula [2] is particularly preferably alkyl (meth) acrylate or poly (alkyleneoxy) (meth) acrylate.

  Specific examples of the monomer represented by the general formula [2] are shown below, but the present invention is not limited to the following specific examples.

Poly (alkyleneoxy) acrylates and methacrylates are commercially available hydroxypoly (alkyleneoxy) materials such as “Pluronic” (Pluronic (Asahi Denka Kogyo Co., Ltd.)), “Adeka Polyether” (Asahi Denka Kogyo ( “Carbowax” [Carbowax (Glico Product)], “Triton” [Toriton (Rohm and Haas) and “PEG” (Daiichi Kogyo Seiyaku Co., Ltd.) Can be produced by reacting what is sold as)) with acrylic acid, methacrylic acid, acrylic chloride, methacrylic chloride or acrylic acid anhydride in a known manner.
Separately, poly (oxyalkylene) diacrylate produced by a known method can also be used.

  In the fluoropolymer, the amount of the fluoroaliphatic group-containing monomer is preferably 50% by mass or more, more preferably 70% by mass or more, and more preferably 80% by mass or more of the total amount of constituent monomers of the polymer. Is more preferable. In the fluoropolymer, the amount of the repeating unit represented by the general formula [1] is preferably 50% by mass or more, more preferably 70% by mass or more of the total amount of the constituent monomers of the fluoropolymer. 80% by mass or more is particularly preferable.

  The mass average molecular weight of the fluoropolymer used in the present invention is preferably 1000 or more and 1,000,000 or less, more preferably 1000 or more and 500,000 or less, and more preferably 1000 or more and 100,000 or less. Further preferred. The mass average molecular weight can be measured as a value in terms of polystyrene (PS) using gel permeation chromatography (GPC).

  The polymerization method of the fluorine-based polymer is not particularly limited, and for example, a polymerization method using a vinyl group such as cationic polymerization, radical polymerization, or anionic polymerization can be employed. Polymerization is particularly preferred in that it can be used for general purposes. The radical polymerization method is not particularly limited, and an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, a solution polymerization method, and the like can be adopted. The solution polymerization, which is a typical radical polymerization method, will be described more specifically. The outlines of other polymerization methods are the same, and details thereof are described, for example, in “Polymer Science Experimental Method” edited by Polymer Society (Tokyo Kagaku Dojin, 1981).

  An organic solvent is used for solution polymerization. These organic solvents can be arbitrarily selected as long as the objects and effects of the present invention are not impaired. These organic solvents are usually organic compounds having boiling points under atmospheric pressure in the range of 50 to 200 ° C., and organic compounds that uniformly dissolve each component are preferred. Examples of preferred organic solvents include alcohols such as isopropanol and butanol; ethers such as dibutyl ether, ethylene glycol dimethyl ether, tetrahydrofuran and dioxane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethyl acetate and acetic acid And esters such as butyl, amyl acetate, and γ-butyrolactone; and aromatic hydrocarbons such as benzene, toluene, and xylene. These organic solvents can be used alone or in combination of two or more. Furthermore, a water-mixed organic solvent in which water is used in combination with the above organic solvent is also applicable from the viewpoint of the solubility of the monomer and the polymer to be produced.

  Also, the solution polymerization conditions are not particularly limited, but for example, it is preferable to heat within a temperature range of 50 to 200 ° C. for 10 minutes to 30 hours. Furthermore, in order not to deactivate the generated radicals, it is preferable to perform an inert gas purge not only during solution polymerization but also before the start of solution polymerization. Usually, nitrogen gas is suitably used as the inert gas.

  Specific examples of the fluoroaliphatic group-containing copolymer preferably used in the present invention as the fluorine-based polymer are shown below, but the present invention is not limited to these specific examples. The numerical value in a formula here is a mass percentage which shows the composition ratio of each monomer, respectively, and Mw is the mass mean molecular weight of PS conversion measured by GPC.

  The fluoropolymer used in the present invention can be produced by a publicly known and commonly used method. For example, it can be produced by adding a general-purpose radical polymerization initiator to an organic solvent containing the above-described monomer having a fluoroaliphatic group, a monomer having a hydrogen bonding group, and the like, and polymerizing the mixture. Further, in some cases, other addition-polymerizable unsaturated compounds can be further added and produced by the same method as described above. Depending on the polymerizability of each monomer, a dropping polymerization method in which a monomer and an initiator are added dropwise to a reaction vessel is also effective for obtaining a polymer having a uniform composition.

  The content of the fluoropolymer in the composition for forming an optically anisotropic layer is 0.005 to 8% by mass in the composition (a composition excluding the solvent in the case of a coating solution). Is preferably 0.01 to 5% by mass, and more preferably 0.05 to 2.5% by mass. 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 Adversely affects the uniformity of the foundation.

  The optical film of the present invention is obtained by applying a composition containing a liquid crystalline compound, the above-mentioned fluorine-based polymer, and other various compounds added as necessary on an alignment film, and orienting the molecules of the liquid crystalline compound. It can be produced by a method including a step of forming an optically anisotropic layer. The optically anisotropic layer exhibits optical anisotropy expressed by molecular orientation of the liquid crystalline compound. Below, materials other than the fluorine-type polymer demonstrated above are demonstrated in detail among the materials used for the optically anisotropic layer of the optical film of this invention.

[Liquid crystal compounds]
In the present invention, as the liquid crystalline compound, any of a rod-like liquid crystalline compound and a discotic liquid crystalline compound may be used, and either a high molecular liquid crystal or a low molecular liquid crystal may be used. Furthermore, after forming the optically anisotropic layer using the composition of the present invention, for example, the low molecular liquid crystal may be contained in a crosslinked state in the optically anisotropic layer, and may no longer exhibit liquid crystallinity. . As the liquid crystalline compound used in the present invention, a discotic liquid crystalline compound is preferable.

  Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. The rod-like liquid crystal compound includes a metal complex liquid crystal compound. Moreover, the liquid crystal polymer which contains a rod-shaped liquid crystalline compound in a repeating unit can also be used as a rod-shaped liquid crystalline compound. In other words, the rod-like liquid crystalline compound may be bonded to a (liquid crystal) polymer. For rod-like liquid crystalline 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 142nd Committee of the Japan Society for the Promotion of Science. Described in Chapter 3. The birefringence of the rod-like liquid crystalline compound is preferably in the range of 0.001 to 0.7. The rod-like liquid crystalline compound preferably has a polymerizable group in order to fix its alignment state. The rod-like liquid crystalline compound is described in WO01 / 88574A1, page 50, line 7 to page 57, last line.

  Examples of discotic liquid crystalline 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, page 2655 (1994), and azacrown-based and phenylacetylene-based macrocycles. Further, the discotic liquid crystal compounds generally have a structure in which these are used as a mother nucleus at the center of a molecule, and a linear alkyl group, an alkoxy group, a substituted benzoyloxy group, etc. are radially substituted as the linear chain. Is also included and exhibits liquid crystallinity. Preferred examples of the discotic liquid crystalline compound are described in JP-A-8-50206.

  As the liquid crystalline compound used in the present invention, triphenylene liquid crystal is particularly preferable. Examples of the triphenylene liquid crystal used in the present invention include the C.I. Destrade et al., Mol. Cryst. 71, 111 (1981); Mourey et al., Mol. Cryst. 84, 193 (1982), and the like. Particularly preferred triphenylene liquid crystals are triphenylene derivatives represented by general formulas (1) to (3) described in JP-A-7-306317, and general formula (I) described in JP-A-7-309813. And triphenylene derivatives represented by the general formula (I) described in JP-A-2001-100028.

  In addition, when the optically anisotropic layer is finally formed, the liquid crystal compound no longer needs to be a liquid crystal compound. For example, a low molecular weight discotic liquid crystalline compound has a group that reacts with heat, light, etc., and as a result, polymerizes or crosslinks by reaction with heat, light, etc. Also good. The polymerization of the discotic liquid crystalline compound is described in JP-A-8-27284, and can be applied to the present invention.

  As an example of a method for fixing a discotic liquid crystalline compound by polymerization, as a discotic liquid crystalline compound, a liquid crystalline compound having a polymerizable group bonded as a substituent to a discotic core is used for hybrid alignment, and then the liquid crystalline There is a method of polymerizing and fixing a compound. However, when a polymerizable group is directly connected to the discotic core, it tends to be difficult to maintain the alignment state in the polymerization reaction. Therefore, it is preferable to introduce a linking group between the discotic core and the polymerizable group. As a preferable discotic liquid crystalline compound having a polymerizable group, a compound represented by the following formula (2) may be mentioned.

General formula (2)
D (-LP) _n
In the formula, D represents a discotic core, L represents a divalent linking group, P represents a polymerizable group, and n represents an integer of 2 to 12. Specific examples of the discotic liquid crystalline compound are described in WO01 / 88574A1 on page 58, line 6 to page 65, line 8.

  As the most preferable liquid crystal compound used in the present invention, triphenylene derivatives represented by general formulas (1) to (3) described in JP-A-7-306317, and general formulas described in JP-A-7-309813. Among the triphenylene derivatives represented by (I) and the triphenylene derivatives represented by the general formula (I) described in JP-A-2001-100028, compounds having a linking group between the triphenylene core and the polymerizable group are used. Can be mentioned.

  In the present invention, two or more kinds of liquid crystal compounds may be used in combination. Further, for example, the polymerizable discotic liquid crystalline compound and the non-polymerizable discotic liquid crystalline compound can be used in combination. The non-polymerizable discotic liquid crystalline compound is preferably a compound in which the polymerizable group (P in the formula (2)) of the polymerizable discotic liquid crystalline compound described above is changed to a hydrogen atom or an alkyl group. That is, the non-polymerizable discotic liquid crystalline compound is preferably a compound represented by the following formula (3).

General formula (3)
D (-LR) _n
In the formula, D represents a discotic core, L represents a divalent linking group, R represents a hydrogen atom or an alkyl group, and n is an integer of 4 to 12.

[Additive for optically anisotropic layer]
In the composition for forming an optically anisotropic layer, an optional additive can be used in combination with the liquid crystalline compound and the fluorine-based polymer. Examples of additives include an anti-repellent agent, an additive for controlling the tilt angle of the alignment film (tilt angle of the liquid crystalline compound at the optically anisotropic layer / alignment film interface), a polymerization initiator, and an alignment temperature. Additives (plasticizers) to be reduced, polymerizable monomers, and the like. Hereinafter, for each additive,

[Anti-repellent agent]
As a material for use in combination with a liquid crystal compound, particularly a discotic liquid crystal compound, to prevent repelling at the time of coating, a polymer compound can generally be suitably used. The polymer to be used is not particularly limited as long as it is compatible with the liquid crystal compound and does not significantly inhibit the tilt angle change or orientation of the liquid crystal compound. Examples of polymers that can be used as repellency inhibitors are described in JP-A-8-95030, and particularly preferred specific polymer examples include cellulose esters. Examples of cellulose esters include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. In order not to inhibit the alignment of the liquid crystalline compound, the amount of the polymer used for the purpose of preventing repellency is generally preferably in the range of 0.1 to 10% by mass with respect to the liquid crystalline compound. More preferably, it is in the range of 8% by mass, and even more preferably in the range of 0.1-5% by mass.

[Alignment film tilt angle control agent]
As an additive for controlling the tilt angle of the alignment film, a compound having both a polar group and a nonpolar group in the molecule can be added. Examples of the compound having a polar group include R—OH, R—COOH, R—O—R, R—NH ₂ , R—NH—R, R—SH, R—S—R, R—CO—R, R -COO-R, R-CONH- R, R-CONHCO-R, R-SO 3 H, R-SO 3 -R, R-SO 2 NH-R, R-SO 2 NHSO 2 -R, R-C = N-R, HO-P (-OR) 2, (HO-) 2 P-OR, P (-OR) 3, HO-PO (-OR) 2, (HO-) 2 PO-OR, PO ( -OR) ₃ , R-NO ₂ , R-CN, and the like. Moreover, organic salts (for example, ammonium salt, pyridinium salt, carboxylate, sulfonate, phosphate) may be used. Among the compounds having the polar group, R—OH, R—COOH, R—O—R, R—NH ₂ , R—SO ₃ H, HO—PO (—OR) ₂ , (HO—) ₂ PO— OR, PO (—OR) ₃ or organic salts are preferred. Here, each R above represents a nonpolar group, for example, an alkyl group (preferably a linear, branched or cyclic substituted or unsubstituted alkyl group having 1 to 30 carbon atoms), an alkenyl group (preferably 1 carbon atom). -30 linear, branched, cyclic substituted or unsubstituted alkenyl group), alkynyl group (preferably a linear, branched, cyclic substituted or unsubstituted alkenyl group having 1 to 30 carbon atoms), aryl group (preferably Examples thereof include substituted or unsubstituted aryl groups having 6 to 30 carbon atoms, and silyl groups (preferably substituted or unsubstituted silyl groups having 3 to 30 carbon atoms). These nonpolar groups may further have a substituent. Examples of the substituent include a halogen atom, an alkyl group (including a cycloalkyl group and a bicycloalkyl group), an alkenyl group (a cycloalkenyl group and a bicycloalkenyl group). Alkynyl group, aryl group, heterocyclic group, cyano group, hydroxyl group, nitro group, carboxyl group, alkoxy group, aryloxy group, silyloxy group, heterocyclic oxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy Group, aryloxycarbonyloxy group, amino group (including anilino group), acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkylsulfonylamino group, arylsulfonyl Mino group, mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, sulfo group, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, acyl group, aryloxycarbonyl group, alkoxycarbonyl group And carbamoyl group, arylazo group, heterocyclic azo group, imide group, phosphino group, phosphinyl group, phosphinyloxy group, phosphinylamino group, silyl group and the like.

  By adding an alignment film tilt control agent to the composition and aligning the molecules of the liquid crystalline compound in the presence of the alignment film tilt control agent, the tilt angle of the liquid crystal molecules at the alignment film side interface can be adjusted. However, the amount of change at that time is related to the rubbing density. If an alignment film having a high rubbing density is compared with an alignment film having a low rubbing density, the tilt angle is more likely to change in the alignment film having a low rubbing density even if the amount of the alignment film tilt control agent added is the same. Therefore, the preferred range of the added amount of the alignment film tilt control agent varies depending on the rubbing density of the alignment film to be used, the desired tilt angle, and the like. The content is preferably 0001% by mass to 30% by mass, more preferably 0.001% by mass to 20% by mass, and still more preferably 0.005% by mass to 10% by mass. Specific examples of the alignment film tilt control agent that can be used in the present invention are shown below, but the present invention is not limited to the following specific examples.

[Polymerization initiator]
It is preferable to form an optically anisotropic layer by fixing the molecules of the liquid crystalline compound in an aligned state, and it is preferable to fix the molecules of the liquid crystalline compound by utilizing a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. In order to prevent deformation of the support and the like due to heat, the photopolymerization reaction is performed. preferable. Examples of the photopolymerization initiator, the amount of photopolymerization initiator used, and the value of the light irradiation energy for polymerization are described in paragraphs [0050] to [0051] of JP-A No. 2001-91741 in the present invention. Applicable.

[Polymerizable monomer]
A polymerizable monomer may be used together with the liquid crystal compound. The polymerizable monomer that can be used in the present invention is not particularly limited as long as it is compatible with the liquid crystal compound and does not cause a significant change in tilt angle or inhibition of alignment of the liquid crystal compound. Among these, compounds having a polymerization active ethylenically unsaturated group such as a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group are preferably used. The addition amount of the polymerizable monomer 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, it is particularly preferable to use a monomer having two or more reactive functional groups because an effect of improving the adhesion between the alignment film and the optically anisotropic layer can be expected.

[Coating solvent]
The composition may be prepared as a coating solution. As a solvent used for preparation of a coating liquid, an organic solvent is preferable. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), 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.

[Application method]
Application of the coating liquid to the alignment film surface can be performed by a known method (for example, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, or a die coating method). Moreover, 1-50 mass% is preferable, as for content of the liquid crystalline compound in a coating liquid, 10-50 mass% is more preferable, and 20-40 mass% is more preferable.

[Characteristics of optically anisotropic layer]
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm.

  When the composition is applied onto the alignment film, the liquid crystalline molecules are aligned at the tilt angle of the alignment film at the interface with the alignment film and at the tilt angle of the air interface at the interface with air. After applying the composition of the present invention to the surface of the alignment film, the liquid crystal compound is uniformly aligned (monodomain alignment). The tilt angle of the liquid crystalline compound (angle formed by the normal of the disc surface of the discotic liquid crystalline compound and the normal of the surface on which the alignment layer of the transparent support is provided) changes continuously in the depth direction of the anisotropic layer. Hybrid orientation can be realized. An optical film having an optically anisotropic layer formed by hybrid-aligning liquid crystal molecules and fixing the liquid crystal molecules in the alignment state contributes to the expansion of the viewing angle of the liquid crystal display device, and also lowers the contrast with respect to a change in viewing angle. This contributes to preventing gradation or black / white reversal and hue change.

  In the presence of the fluorinated polymer, the liquid crystal molecules can be aligned at a tilt angle of 50 ° or more at the air interface. In order to realize hybrid alignment in a state where preferable performance can be exhibited as an optical compensation sheet, the tilt angle of the liquid crystalline molecules on the alignment film side is preferably 3 ° to 30 °. The tilt angle of the liquid crystal molecules on the alignment film side can be controlled by the above-described methods (alignment film rubbing density, alignment film tilt angle control agent, etc.). On the other hand, the tilt angle of the liquid crystal molecules on the air interface side is formed by using the fluorine-based polymer and other compounds added as desired (for example, at least two kinds of compounds having the hydrogen bonding group). And a preferred hybrid alignment state can be realized according to the display mode of the liquid crystal display device to which the optical film of the present invention is applied.

[Tilt angle]
The tilt angle refers to an angle formed between the major axis direction of the molecule of the liquid crystal compound and the normal line of the interface (alignment film interface or air interface). In the present invention, the tilt angle of the alignment film is 3 ° to 30 °, air The tilt angle on the interface side is preferably 40 to 80 °. If the tilt angle of the alignment film is too small, the time required for monodomain alignment of a liquid crystal compound, particularly a discotic liquid crystal compound, is increased, but it is preferable that the tilt angle is too large. On the contrary, it is not preferable because preferable optical performance cannot be obtained. Therefore, from the viewpoint of shortening the monodomain formation time and preferable optical performance as an optical compensation sheet, the tilt angle of the preferred alignment film is preferably 5 ° to 30 °, more preferably 10 to 30 °, and particularly preferably 20 to. 30 °. Further, the tilt angle on the air interface side is preferably 40 to 80 °, more preferably 50 to 80 °, and particularly preferably 50 to 70 °. The tilt angle on the alignment film side can be controlled in the range of several degrees to several tens of degrees by changing the rubbing density of the alignment film or adding the alignment film tilt angle control agent. As described above, when the optically anisotropic layer is once formed and then disposed between two layers by transfer or the like, the interface of the optically anisotropic layer is not necessarily the alignment film interface and the air interface. In such an embodiment, the tilt angle of the liquid crystalline molecules on one interface side and the other interface side of the two interfaces of the optically anisotropic layer is such that the alignment film side tilt angle range and the air interface side The tilt angle is preferably in the range.

[Alignment film]
The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. As long as the desired orientation can be imparted to the liquid crystalline compound of the optically anisotropic layer provided on the alignment film, any layer may be used as the alignment film. In the present invention, the tilt angle of the alignment film is controlled. From the viewpoint of easiness, an alignment film formed by a rubbing treatment of a polymer is particularly preferable. The rubbing treatment can be generally carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. In particular, in the present invention, it is described in “Liquid Crystal Handbook” (Maruzen Co., Ltd.). It is preferable to carry out by a method. The thickness of the alignment film is preferably 0.01 to 10 μm, and more preferably 0.05 to 1 μm. The polymer used for the alignment film is described in many documents, and many commercially available products can be obtained. For the production of the alignment film for the optical film of the present invention, polyvinyl alcohol and its derivatives are preferably used. Particularly preferred is a modified polyvinyl alcohol having a hydrophobic group bonded thereto. Regarding the alignment film, reference can be made to the description of page 43, line 24 to page 49, line 8 of WO01 / 88574A1.

[Rubbing density of alignment film]
As a method for changing the rubbing density of the alignment film, a method described in “Liquid Crystal Handbook” (Maruzen Co., Ltd.) can be used. The rubbing density (L) is quantified by the formula (A).
Formula (A) L = Nl {1+ (2πrn / 60v)}
In the formula (A), N is the number of rubbing, l is the contact length of the rubbing roller, r is the radius of the roller, n is the number of rotations (rpm) of the roller, and v is the stage moving speed (second speed). In order to increase the rubbing density, the rubbing frequency should be increased, the contact length of the rubbing roller should be increased, the radius of the roller should be increased, the rotation speed of the roller should be increased, and the stage moving speed should be decreased, while the rubbing density should be decreased. To do this, you can reverse this. Between the rubbing density and the tilt angle of the alignment film, there is a relationship in which the tilt angle decreases as the rubbing density increases and the tilt angle increases as the rubbing density decreases.

  If the liquid crystal molecules are aligned and the state is fixed by polymerization or the like, the alignment state can be maintained without an alignment film. Therefore, after the optically anisotropic layer is formed on an alignment film (for example, an alignment film formed on a temporary support), only the optically anisotropic layer is transferred onto the transparent support. An optical film can also be produced. That is, the present invention includes an optical film that does not include an alignment film.

[Transparent support]
The support used in the present invention is preferably transparent, and the light transmittance is preferably 80% or more. It is preferable to use an optically isotropic polymer film. As the specific examples and preferred embodiments of the polymer, the description in paragraph [0013] of JP-A-2002-22294 can be applied. In addition, even a conventionally known polymer such as polycarbonate or polysulfone, which easily develops birefringence, should have a decreased expression by modifying the molecule described in WO00 / 26705. You can also.

  As the polymer film, it is preferable to use cellulose acetate having an acetylation degree of 55.0 to 62.5%. In particular, the acetylation degree is preferably 57.0 to 62.0%. The description of paragraph number [0021] of JP-A No. 2002-196146 can be applied to the degree of acetylation, the range thereof, and the chemical structure of cellulose acetate. About manufacturing a cellulose acylate film using a non-chlorinated solvent, it is described in detail in JIII Journal of Technical Disclosure No. 2001-1745, and the cellulose acylate film described therein is also preferably used in the present invention. it can.

  The description of paragraph numbers [0018] to [0019] of JP-A No. 2002-139621 can be applied to the retardation value in the thickness direction of the cellulose ester film used as the transparent support and the range of the birefringence.

  In order to adjust the retardation of a polymer film used as a transparent support, particularly a cellulose acylate film, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation increasing agent. The description of paragraph numbers [0021] to [0023] of JP-A No. 2002-139621 can be applied to the preferred range and usage amount of the aromatic compound. Such retardation increasing agents are described in WO01 / 88574A1, WO00 / 2619A1, JP-A Nos. 2000-1111914, 2000-275434, and Japanese Patent Application No. 2002-70009.

  The cellulose acylate film is preferably produced by a solvent cast method from the prepared cellulose acylate solution (dope). It is preferable to add the above-mentioned retardation increasing agent to the dope. Using the prepared cellulose acylate solution (dope), a film can be formed by casting two or more layers of the dope. The description of paragraph numbers [0038] to [0040] of JP-A No. 2002-139621 can be applied to the formation of the film.

  The retardation of the cellulose acylate film can be further adjusted by a stretching treatment. The draw ratio is preferably in the range of 3 to 100%. When stretching the cellulose acylate film, tenter stretching is preferably used, and in order to control the slow axis with high accuracy, it is preferable to make the difference between the left and right tenter clip speeds, the separation timing, etc. as small as possible. .

  A plasticizer can be added to the cellulose ester film in order to improve mechanical properties or increase the drying speed. As a plasticizer, the aspect of paragraph number [0043] of JP, 2002-139621, A and a desirable range are applicable to the present invention.

  Degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) and UV inhibitors may be added to the cellulose ester film. Regarding the deterioration preventing agent, the description in paragraph number [0044] of JP-A-2002-139621 can be applied. As a particularly preferred example of the deterioration preventing agent, butylated hydroxytoluene (BHT) can be mentioned. The ultraviolet ray preventing agent is described in JP-A-7-11056.

  Regarding the surface treatment of the cellulose acylate film and the surface energy of the solid, the description in paragraph numbers [0051] to [0052] of JP-A No. 2002-196146 can be applied.

  The thickness of the cellulose acylate film varies depending on the purpose of use, but is usually in the range of 5 to 500 μm, more preferably in the range of 20 to 250 μm, and most preferably in the range of 30 to 180 μm. In addition, as an optical use, the range of 30-110 micrometers is especially preferable.

[Use of optical film]
The optical film of the present invention is preferably used for a liquid crystal display device as an optical compensation sheet. Moreover, it can use for the use of an elliptically polarizing plate in combination with a polarizing film. Furthermore, by applying to a transmissive liquid crystal display device in combination with a polarizing film, it contributes to an increase in viewing angle. The elliptically polarizing plate and liquid crystal display device using the optical film of the present invention as an optical compensation sheet will be described below.

[Elliptically polarizing plate]
An elliptically polarizing plate can be produced by laminating the optical film of the present invention and a polarizing film. By using the optical film of the present invention, an elliptically polarizing plate capable of expanding the viewing angle of a liquid crystal display device can be provided. Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film.

  The polarizing film is laminated on the optically anisotropic layer side of the optical compensation sheet. It is preferable to form a transparent protective film on the surface opposite to the side on which the optical compensation sheet of the polarizing film is laminated. The transparent protective film preferably has a light transmittance of 80% or more. As the transparent protective film, generally a cellulose ester film, preferably a triacetyl cellulose film is used. The cellulose ester film is preferably formed by a solvent cast method. The thickness of the transparent protective film is preferably 20 to 500 μm, and more preferably 50 to 200 μm.

[Liquid Crystal Display]
By using the optical film of the present invention, a liquid crystal display device having an enlarged viewing angle can be provided. In addition, a liquid crystal display device that can display a high-quality image without display unevenness can be provided. Optical compensation sheets for TN mode liquid crystal cells are described in JP-A-6-214116, US Pat. No. 5,583,679, US Pat. No. 5,646,703, and German Patent Publication 3911620A1. Further, an optical compensation sheet for liquid crystal cells in IPS mode or FLC mode is described in JP-A-10-54982. Furthermore, OCB mode or HAN mode liquid crystal cell optical compensation sheets are described in US Pat. No. 5,805,253 and International Publication WO 96/37804. Furthermore, an optical compensation sheet for an STN mode liquid crystal cell is described in JP-A-9-26572. A VA mode liquid crystal cell optical compensation sheet is described in Japanese Patent No. 2866372.

  In the present invention, optical compensation sheets for liquid crystal cells of various modes can be produced with reference to the above publication. The optical film of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensated Bend), STN (Super Tint Vendor). It can be used as an optical compensation film in a liquid crystal display device having a liquid crystal cell driven in various modes such as a Hybrid Aligned Nematic) mode. The optical film of the present invention is particularly effective in a liquid crystal display device of TN (Twisted Nematic) mode or OCB (Optically Compensatory Bend) mode.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

In a reactor equipped with a stirrer and a reflux condenser, 39.2 g of 1H, 1H, 7H-dodecafluoroheptyl acrylate, 0.8 g of mercaptoacetic acid (manufactured by Sigma-Aldrich Co., Ltd.), dimethyl 2,2′-azobis (2 -Methyl propionate (V-601 manufactured by Wako Pure Chemical Industries, Ltd.) 1.1 g and 30 g of 2-butanone were added, and the reaction was completed by heating at 78 ° C. for 6 hours under a nitrogen atmosphere. It was 1.4 × 10 ⁴ .

Fluoropolymers (P-12) and (P-20) were synthesized by a method similar to the synthesis of the fluoroaliphatic group-containing polymer (P-1).
Further, the following polymer R-1 was used as a comparative polymer.

[Example 1]
(Production of polymer substrate)
The following composition was put into a mixing tank and stirred while heating to 30 ° C. to dissolve each component to prepare a cellulose acetate solution.
────────────────────────────────────
Cellulose acetate solution composition (parts by mass) Inner layer Outer layer ────────────────────────────────────
Cellulose acetate with an acetylation degree of 60.9% 100 100
Triphenyl phosphate (plasticizer) 7.8 7.8
Biphenyl diphenyl phosphate (plasticizer) 3.9 3.9
Methylene chloride (first solvent) 293 314
Methanol (second solvent) 71 76
1-butanol (third solvent) 1.5 1.6
Silica fine particles (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.)
0 0.8
The following retardation increasing agent 2.20
────────────────────────────────────

  The obtained inner layer dope and outer layer dope were cast on a drum cooled to 0 ° C. using a three-layer co-casting die. The film having a residual solvent amount of 70% by mass was peeled off from the drum, both ends were fixed with a pin tenter, and the film was dried at 80 ° C. while transporting at a draw ratio of 110% in the transport direction, resulting in a residual solvent amount of 10%. By the way, it was dried at 110 ° C. Thereafter, it was dried at 140 ° C. for 30 minutes to produce a cellulose acetate film (outer layer: 3 μm, inner layer: 74 μm, outer layer: 3 μm) having a residual solvent of 0.3 mass%. The optical properties of the produced cellulose acetate film (PK-1) were measured.

The obtained polymer substrate (PK-1) had a width of 1340 mm and a thickness of 80 μm. It was 6 nm when the retardation value (Re) in wavelength 546nm was measured by the said method. Moreover, it was 90 nm when the retardation value (Rth) in wavelength 500nm was measured.
The prepared polymer substrate (PK-1) was immersed in a 2.0 mol / L potassium hydroxide solution (25 ° C.) for 2 minutes, neutralized with 2.0 mol / L sulfuric acid, washed with pure water, and dried. did. The surface energy of this PK-1 was determined by the contact angle method and found to be 63 mN / m.

On this PK-1, an alignment film coating solution having the following composition was coated at a coating amount of 28 ml / m ² with a # 16 wire bar coater. A polyvinyl alcohol layer was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds.

(Orientation film coating solution composition)
The following modified polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight

  The surface of the formed polyvinyl alcohol layer was rubbed to form an alignment film. In the rubbing treatment, the alignment film was rubbed in a direction parallel to the slow axis (measured at a wavelength of 632.8 nm) of the polymer substrate (PK-1).

(Formation of optically anisotropic layer)
The following composition was dissolved in 102 parts by mass of methyl ethyl ketone to prepare a coating solution.
The following discotic liquid crystalline compound (1) 41.01 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 4.06 parts by mass Fluoro aliphatic group-containing polymer exemplified compound ( P-1) 0.02 parts by mass photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 1.35 parts by mass sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.45 parts by mass

  The prepared coating solution was applied to the surface of the alignment film with a # 3.4 wire bar at room temperature and further heated in a constant temperature zone of 120 ° C. for 2 minutes to hybrid-align the discotic liquid crystalline compound. Next, UV irradiation was performed for 1 minute using a 120 W / cm high-pressure mercury lamp in an atmosphere of 60 ° C., and the discotic liquid crystalline compound was polymerized to fix the alignment state. Then, it stood to cool to room temperature. Thus, an optically anisotropic layer was formed, and an optical compensation sheet (KH-1) was produced. The Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm was 50 nm.

(Surface evaluation of optical compensation sheet)
The polarizing plate was placed in a crossed Nicol arrangement, and the unevenness and repellency of the optical compensation sheet obtained from the front and the direction inclined from the normal to 60 degrees were observed. The results are shown in Table 1. In the same manner, Examples 2 and 3 shown below and Comparative Examples 1 and 2 were also evaluated for surface conditions.

(Evaluation of tilt angle of liquid crystal compounds)
The retardation of the liquid crystal compound in the optically anisotropic layer near the alignment film and the air interface near the air interface is changed by changing the observation angle using an ellipsometer (APE-100, manufactured by Shimadzu Corporation). Jpn. J. et al. Appl. Phys. Vol. 36 (1997) p. It calculated by the method described in 143-147. The measurement wavelength was 632.8 nm. The results are shown in Table 1. In the following Examples 2 and 3 and Comparative Examples 1 and 2 as well, the tilt angle was determined in the same manner.
(Preparation of polarizing plate)
Using a polyvinyl alcohol-based adhesive, KH-1 (optical compensation sheet) was attached to one surface of the polarizer (HF-1). Further, a saponification treatment was performed on a 80 μm-thick triacetyl cellulose film (TD-80U: manufactured by Fuji Photo Film Co., Ltd.), and the opposite surface of the polarizer (HF-1) using a polyvinyl alcohol adhesive. Pasted on.
The transmission axis of the polarizer (HF-1) and the slow axis of the polymer film (PK-1) which is a support for the optical compensation sheet were arranged in parallel. The transmission axis of the polarizer (HF-1) and the slow axis of the triacetyl cellulose film were arranged so as to be orthogonal to each other. In this way, a polarizing plate (HB-1) was produced.

(Evaluation with TN liquid crystal cell)
A pair of polarizing plates provided in a liquid crystal display device (AQUAS LC20C1S, manufactured by Sharp Corporation) using a TN type liquid crystal cell is peeled off, and the produced polarizing plate (HB-1) is replaced with an optical compensation sheet. A single sheet was affixed to the observer side and the backlight side via an adhesive so that (KH-1) was on the liquid crystal cell side. The transmission axis of the polarizing plate on the viewer side and the transmission axis of the polarizing plate on the backlight side were arranged to be in the O mode.
About the produced liquid crystal display device, the viewing angle was measured from black display (L1) to white display (L8) using a measuring machine (EZ-Contrast 160D, manufactured by ELDIM). A region having a contrast ratio (white transmittance / black transmittance) of 10 or more and no gradation inversion on the black side (inversion at L1 and L2) was obtained as a viewing angle in the vertical and horizontal directions. The measurement results are shown in Table 1. The viewing angles were similarly determined for Examples 2 and 3 shown below and Comparative Examples 1 and 2.

[Examples 1 to 3, Comparative Examples 1 and 2]
As shown in Table 1, an optical compensation sheet was prepared in the same manner as in Example 1 except that the type and addition amount of the fluoroaliphatic group-containing polymer were changed. Similarly, the surface shape, the inclination angle, and the viewing angle were evaluated. Went. The results are shown in Table 1.

  As can be seen from the results in Table 1 above, by using a small amount of the fluoroaliphatic group-containing polymer of the present invention, the discotic compound can be brought into a hybrid alignment state with a sufficient inclination angle on the air interface side. An optical compensation sheet having a desired optical compensation capability and a good surface shape was obtained. Furthermore, by using such an optical compensation sheet, a liquid crystal display device having a good viewing angle could be provided.

[Example 4]
Optical compensation was performed in the same manner as in Example 1 except that the polymer base material having Rth of 80, 85, 100, 110, and 120 nm was prepared by changing the addition amount of the retardation increasing agent used in Example 1. Sheets and further polarizing plates with optical compensation sheets were prepared. Even when the Rth of the polymer substrate was changed to 80, 85, 100, 110, and 120 nm, it was confirmed that the viewing angles of the upper, lower, left, and right sides were almost the same as the viewing angles obtained in Example 1.

[Example 5]
Example 1 except that the retardation increasing agent used in Example 1 was replaced with the following retardation increasing agent, and the addition amount of the inner layer was 1.2 parts by mass, and a polymer substrate having an Rth of 90 nm was prepared. In the same manner as described above, an optical compensation sheet and a polarizing plate with an optical compensation sheet were produced. It was confirmed that the vertical and horizontal viewing angles were almost the same as the viewing angles obtained in Example 1.

[Example 6]
Optical compensation was performed in the same manner as in Example 1 except that the polymer base material having Rth of 80, 85, 100, 110, and 120 nm was prepared by changing the addition amount of the retardation increasing agent used in Example 5. Sheets and further polarizing plates with optical compensation sheets were prepared. Even when the Rth of the polymer substrate was changed to 80, 85, 100, 110, and 120 nm, it was confirmed that the viewing angles of the upper, lower, left, and right sides were almost the same as the viewing angles obtained in Example 1.

The polarizing plate having the optical film of the present invention and the optical film of the present invention includes a carboxyl group (—COOH), a sulfo group (—SO ₃ H), a phosphono group [—PO (OH) _{2 in the} optically anisotropic layer. And a fluoroaliphatic group-containing polymer having at least one hydrophilic group selected from the group consisting of salts thereof at the main chain end, and thus has excellent optical compensation ability and good surface shape It is. Even if the liquid crystal display device to which the optical film or polarizing plate of the present invention is applied is large, the image has no or less unevenness and can display an image with high display quality.

Claims (7)

An optical film having an optically anisotropic layer formed from a composition containing a liquid crystal compound on a support, the optically anisotropic layer comprising a carboxyl group (—COOH), a sulfo group (—SO ₃ H ), At least one fluoroaliphatic group-containing polymer having one or more hydrophilic groups selected from the group consisting of phosphono groups [—PO (OH) ₂ ] and salts thereof, and the fluoroaliphatic A chain in which the group-containing polymer has at least one hydrophilic group selected from the group consisting of a carboxyl group (—COOH), a sulfo group (—SO ₃ H), a phosphono group [—PO (OH) ₂ ], and salts thereof. An optical film which is a polymer obtained by polymerization using a transfer agent. The optical film according to claim 1, wherein the fluoroaliphatic group-containing polymer includes a repeating unit derived from a fluoroaliphatic group-containing monomer represented by the following general formula [1]:

In the general formula [1], R ¹ represents a hydrogen atom or a methyl group, X represents an oxygen atom, a sulfur atom or —N (R ² ) —, Z represents a hydrogen atom or a fluorine atom, and m represents 1 or more and 6 The following integers, n represents an integer of 2 to 4, and R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The optical film according to claim 1 or 2, wherein the fluoroaliphatic group-containing polymer includes a repeating unit derived from a monomer represented by the following general formula [2]:

In the general formula [2], R ⁶ represents a hydrogen atom or a methyl group, Z represents a divalent linking group, and R ⁷ represents a poly (alkyleneoxy) group or a substituent which may have a substituent. A linear, branched or cyclic alkyl group having 1 to 20 carbon atoms which may be present. The optical film according to claim 1, wherein the liquid crystal compound is a discotic compound. An optical film having an optically anisotropic layer formed from a composition containing a liquid crystal compound on a support, the optically anisotropic layer comprising a carboxyl group (—COOH), a sulfo group (—SO ₃ H), one or more hydrophilic groups selected from the group consisting of phosphono groups [—PO (OH) ₂ ] and salts thereof via at least a divalent group containing a thioether bond (—S—) An optical film containing at least one kind of fluoroaliphatic group-containing polymer bonded to. A polarizing plate comprising the optical film according to claim 1 and a polarizer. A liquid crystal display device comprising the polarizing plate according to claim 6.