JP5671832B2 - Optical film, polarizing plate using the same, and liquid crystal display device - Google Patents

Description

  The present invention relates to an optical film, a polarizing plate using the optical film, and a liquid crystal display device.

  In a liquid crystal display device, an optical film (hereinafter simply referred to as a retardation film) for compensating a retardation due to birefringence of a liquid crystal cell is widely used. Various retardation films have been proposed so far, and stretched films obtained by orienting transparent resins by stretching have been widely used. Examples of the stretched film include films made of cellulose resin, polycarbonate resin, cyclic olefin resin, and the like.

  Among them, a cellulose ester film having a cellulose ester (hereinafter also referred to as a cellulose ester film) is widely used because of its excellent bonding property to polyvinyl alcohol used for a polarizer.

  However, the cellulose ester film has a disadvantage that the photoelastic coefficient is large and optical unevenness (frame unevenness) tends to occur at the edge of the corner portion of the liquid crystal display device. Therefore, development of a retardation film having a small photoelastic coefficient and excellent adhesion to polyvinyl alcohol as a polarizer has been demanded.

  A cyclic olefin resin film is known as a retardation film having a small photoelastic coefficient, but its bonding property with polyvinyl alcohol as a polarizer is insufficient.

  As a retardation film having a small photoelastic coefficient using a resin having a maleimide ring, a copolymer of an N-substituted maleimide resin, methyl methacrylate, and an aromatic vinyl compound is disclosed (for example, Patent Document 1). The retardation was negative, and the bonding property with polyvinyl alcohol was insufficient.

  In addition, as a retardation film that uses a resin having a maleimide ring and the retardation is positively expressed, homopolymers of N-substituted maleimides and copolymers with maleic anhydride are disclosed (for example, patent documents). 2) There is no description about the photoelastic coefficient in the specification. Further, the maleimide resin disclosed in the patent has a problem that the bonding property with polyvinyl alcohol is insufficient.

  Although a technique for producing a polarizer protective film having a small photoelastic coefficient by mixing a resin having a glutarimide ring is disclosed (for example, Patent Document 3), the film described in the patent has sufficient retardation. However, it had the subject that the pasting property with polyvinyl alcohol was insufficient.

JP 2008-268720 A JP 2009-156908 A JP 2006-316153 A

  The present invention has been made in view of the above problems, and an object of the present invention is an optical that has a small photoelastic coefficient, excellent retardation, low bleed-out, and excellent adhesion to a polarizer. To provide a film. Another object of the present invention is to provide a polarizing plate having good light resistance using the optical film and a liquid crystal display device in which frame unevenness is suppressed.

  The above object of the present invention is achieved by the following configurations.

1. The polymer (A) having at least one repeating unit represented by the following general formula (1) and having at least one repeating unit composed of a monomer having a hydroxyl group or an amide bond, and the cellulose ester , The content of (A) is contained within the range of 5 to 70% by mass with respect to the cellulose ester , and in the environment of 23 ° C. and 55% RH, with respect to light having a wavelength of 590 nm, the following formula: Retardation Ro represented by (I) is 20-100 nm, Rth represented by following formula (II) is 70-300 nm, The optical film characterized by the above-mentioned.

(In the formula, R ₁ represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group, and R ₂ and R ₃ each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. N is 0 or 1 is represented.)
Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x in which the refractive index is maximum in the in-plane direction of the optical film, and ny represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the optical film. , Nz represents the refractive index in the thickness direction z of the optical film, and d (nm) represents the thickness of the optical film.)
2. 2. The optical film as described in 1 above, wherein in the general formula (1), R ₁ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

3. 3. The optical film as described in 1 or 2 above, wherein the cellulose ester is cellulose acetate propionate and simultaneously satisfies the acyl group substitution degrees of the following formulas (1) and (2).

Formula (1) 1.4 <= X + Y <= 2.4
Formula (2) 0.5 <= Y <= 2.0
(In the formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the propionyl group.)
4). The optical film according to any one of 1 to 3 has a photoelastic coefficient of −5 × 10 ⁻¹² Pa ⁻¹ or more and 10 for light having a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. * 10 < ^-12> Pa < ^{-1 >} or less, The optical film characterized by the above-mentioned.

5. 5. A polarizing plate comprising the optical film according to any one of 1 to 4 on at least one surface of a polarizer.

6 . 6. A liquid crystal display device comprising the polarizing plate according to 5 above on at least one surface of a liquid crystal cell.

  According to the present invention, it is possible to provide an optical film having a small photoelastic coefficient, excellent phase difference, little bleed-out, and excellent adhesion to a polarizer. In addition, it is possible to provide a polarizing plate using the optical film with good light resistance and a liquid crystal display device in which frame unevenness is suppressed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  As a result of intensive studies to solve the above-described problems, the present inventors have found that a conventionally known polymer having a repeating unit represented by the general formula (1) has a hydroxyl group or an amide bond. It was found that the compatibility with the cellulose ester was remarkably improved and the bleed out was improved by introducing the repeating unit as described above into the polymer (A). Furthermore, the optical film containing the polymer (A) and the cellulose ester has not only positive retardation, but also a conventional polarizer protective film disclosed in Patent Documents 1 to 3. It was found that it was excellent in pasting property with a polarizer, which was a problem. In addition, since the polymer (A) has a very small photoelastic coefficient, it has a sufficient phase difference by mixing with a cellulose ester, has excellent bonding properties with a polarizer, and has a photoelastic coefficient. Small film can be provided. Further, it is found that by using the optical film obtained by the above configuration, a polarizing plate having good light resistance and a liquid crystal display device in which frame unevenness is suppressed can be obtained, and as soon as the present invention has been achieved.

    Hereinafter, the present invention will be described in detail.

(Optical film)
In the present invention, the “optical film” is a functional film used for various display devices such as a liquid crystal display, a plasma display, and an organic EL display, and more specifically, a polarizing plate protective film for a liquid crystal display device, a retardation film. Films, antireflection films, brightness enhancement films, hard coat films, antiglare films, antistatic films, optical compensation films such as viewing angle expansion, and the like are included.

The optical film in the present invention includes a polymer (A) having at least one repeating unit represented by the general formula (1) and at least one repeating unit composed of a monomer having a hydroxyl group or an amide bond, and cellulose. The ester is characterized in that the content of the polymer (A) is contained within a range of 5 to 70% by mass with respect to the cellulose ester .

In the general formula (1), R ₁ represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a hexyl group, an octyl group, a dodecyl group, and a 2-ethylhexyl group. Examples of the cycloalkyl group include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, and the like. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a methylnaphthyl group, an anthryl group, a phenanthryl group, and a biphenyl group. Preferably, it is an alkyl group, More preferably, it is a C1-C20 alkyl group.

  These alkyl group, cycloalkyl group and aryl group may have a substituent. Examples of the substituent include a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, etc.), an aryl group (for example, , Phenyl group, naphthyl group etc.), heterocyclic group (eg pyridine group, furan group, thiophene group), alkoxy group (eg methoxy group, ethoxy group, propoxy group etc.), aryloxy group (eg phenoxy group) An alkylcarbonyloxy group (for example, acetyloxy group), an alkylthio group (for example, methylthio group, trifluoromethylthio group, etc.), a carboxyl group, an alkylcarbonylamino group (for example, acetylamino group), a ureido group (for example, Methylaminocarbonylamino group, etc.), alkylsulfonyl group (eg, methanes) Phenyl group, trifluoromethanesulfonyl group, etc.), carbamoyl group (for example, carbamoyl group, N, N-dimethylcarbamoyl group, N-morpholinocarbonyl group, etc.), sulfamoyl group (sulfamoyl group, N, N-dimethylsulfamoyl group, Morpholinosulfamoyl group, etc.), trifluoromethyl group, hydroxy group, nitro group, cyano group, alkylsulfonamide group (eg methanesulfonamide group, butanesulfonamide group etc.), alkylamino group (eg amino group, N , N-dimethylamino group, N, N-diethylamino group, etc.), sulfo group, phosphono group, sulfite group, sulfino group, alkylsulfonylaminocarbonyl group (for example, methanesulfonylaminocarbonyl group, ethanesulfonylaminocarbonyl group, etc.) A Killcarbonylaminosulfonyl group (for example, acetamidosulfonyl group, methoxyacetamidosulfonyl group, etc.), alkylaminocarbonyl group (for example, acetamidocarbonyl group, methoxyacetamidocarbonyl group, etc.), alkylsulfinylaminocarbonyl group (for example, methanesulfinylaminocarbonyl group) Ethanesulfinylaminocarbonyl group, etc.). Moreover, when there are two or more substituents, they may be the same or different.

  n represents 0 or 1.

R ₂ and R ₃ each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Preferably, they are a hydrogen atom, a methyl group, or an ethyl group, More preferably, they are a hydrogen atom or a methyl group.

  Examples of the monomer that forms the repeating unit of the general formula (1) include N-methylmaleimide, N-ethylmaleimide, N-chloroethylmaleimide, N-methoxyethylmaleimide, N-hydroxyethylmaleimide, Nn- Propylmaleimide, Nn-butylmaleimide, Nn-hexylmaleimide, Nn-octylmaleimide, Nn-laurylmaleimide, N-isopropylmaleimide, N-isobutylmaleimide, Ns-butylmaleimide, N- Examples thereof include t-butylmaleimide.

  The content of the repeating structure represented by the general formula (1) in the polymer (A) is preferably 3 to 90 mol%, more preferably 5 to 50 mol%, still more preferably 10 to 40 mol%. It is.

  The polymer (A) may have a repeating unit of a monomer having a hydroxyl group or an amide group in addition to the repeating unit represented by the general formula (1) in order to enhance the compatibility with the cellulose ester. preferable. As the monomer having a hydroxyl group or an amide group, N, N-dimethylacrylamide, N, N-diethylacrylamide, N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-4-methyl- 2-pyrrolidone, N-vinyl-5-methyl-2-pyrrolidone, N-vinylacetamide, acryloylmorpholine, 2-hydroxyethylacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, hydroxymethyl acrylate, 3-hydroxy Mention is made of propyl methacrylate, 3-hydroxypropyl acrylate, allyl alcohol, methallyl alcohol, 1-buten-3-ol, 2-propyn-1-ol, 2-hydroxymethyl-1-butene, α-hydroxymethylstyrene and the like. It can be. Particularly preferred are N, N-dimethylacrylamide, N, N-diethylacrylamide, N-vinyl-2-pyrrolidone, acryloylmorpholine, and 2-hydroxyethyl methacrylate.

  The content ratio of the polymer structure constructed by polymerizing the monomer having a hydroxyl group or an amide bond in the polymer (A) is preferably 3 to 90% by mass, more preferably 5 to 70% by mass. More preferably, it is 10-50 mass%.

  The polymer (A) may have a repeating unit other than the monomer. The monomer that forms a repeating unit other than the monomer is not particularly limited, but is a (meth) acrylic acid ester monomer, a vinyl ester monomer, or any other vinyl monomer. Can be mentioned.

  Specific examples of the (meth) acrylic acid ester monomer include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate. , Cycloalkyl acrylate, cycloalkyl methacrylate, benzyl acrylate, benzyl methacrylate and the like.

  Specific examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, isopropenyl acetate, 1-butenyl acetate and the like.

  Specific examples of other optional vinyl monomers include, for example, (meth) acrylic acid, acrylamide, styrene, α-methylstyrene, methyl vinyl ether, ethyl vinyl ether, cyclohexyl vinyl ether, fumaric acid, dimethyl fumarate, maleic anhydride Examples include acid, itaconic acid, itaconic anhydride, acrylonitrile and the like.

  When the weight average molecular weight of the polymer (A) is too high, the compatibility with the cellulose ester and the solubility in the solvent are deteriorated. On the other hand, when the weight average molecular weight is too low, the coating property is deteriorated. More preferably, it is 5000-500000, Most preferably, it is 10000-100,000. The weight average molecular weight was calculated by measurement using gel permeation chromatography (GPC) under the following measurement conditions.

Solvent: Tetrahydrofuran Column: TSKgel SuperHM-M (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Flow rate: 0.6ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000 to 500 samples are used. Thirteen samples are used at approximately equal intervals.

  The polymer (A) can be synthesized by any appropriate method.

  In the general formula (1), when n = 1, examples of the method for synthesizing the polymer (A) include Japanese Patent Laid-Open Nos. 2006-37493, 2007-9191, and 2008-255139. Gazette, JP-A-2008-255175, Korea Polymer Journal vol. 3, No. 2, pp 76-81 (1995) and the like.

  In the general formula (1), when n = 0, the polymer (A) can be synthesized by radical polymerization of N-substituted maleimide and the above-mentioned other monomers. .

  The form of the polymerization reaction for obtaining the polymer (A) is not particularly limited, and polymerization forms such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization can be used.

  The polymerization temperature and the polymerization time vary depending on the type of monomer used, the usage ratio, etc., but preferably the polymerization temperature is 0 to 150 ° C., the polymerization time is 0.5 to 30 hours, and more preferably the polymerization is performed. The temperature is 60 to 140 ° C., and the polymerization time is 1 to 24 hours.

  In the case of a polymerization form using a solvent, the polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone ketone; ethers such as tetrahydrofuran Etc., and only one of these may be used, or two or more may be used in combination.

  During the polymerization reaction, a polymerization initiator may be added as necessary. Although it does not specifically limit as a polymerization initiator, For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amyl Organic peroxides such as peroxy-2-ethylhexanoate; 2,2'-azobis (isobutyronitrile), 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2, Azo compounds such as 4-dimethylvaleronitrile), and the like. These may be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited as long as it is appropriately set according to the combination of the monomers used and the reaction conditions.

  The content of the polymer (A) with respect to the cellulose ester is preferably 5 to 70% by mass for obtaining the effect of the present invention, that is, the development of retardation and the improvement of the bonding property with a polarizer.

(Cellulose ester)
The optical film in the present invention is characterized by containing a cellulose ester in addition to the polymer (A).

  The cellulose ester used in the present invention is not particularly limited, but the ester group is preferably a linear or branched carboxylic acid ester having about 2 to 22 carbon atoms, and these carboxylic acids may form a ring. It may be an aromatic carboxylic acid ester. In addition, these carboxylic acids may have a substituent. The cellulose ester is particularly preferably a lower fatty acid ester having 6 or less carbon atoms.

  As a preferred cellulose ester, specifically, in addition to cellulose acetate, a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate. Mention may be made of mixed fatty acid esters of cellulose. Of these, cellulose acetate propionate is particularly preferred.

  It is preferable that the cellulose acetate propionate used in the present invention satisfies the substitution degrees of the following formulas (1) and (2) at the same time.

Formula (1) 1.4 <= X + Y <= 2.4
Formula (2) 0.5 <= Y <= 2.0
(In the formula, X represents the degree of substitution of the acetyl group. Y represents the degree of substitution of the propionyl group.)
The measuring method of the substitution degree of these acyl groups can be measured according to ASTM-D817-96.

  A smaller total acyl group substitution degree tends to increase the phase difference, but the dimensional change, haze, and water absorption tend to deteriorate. When the total acyl group substitution degree is too large, it becomes difficult to develop a phase difference.

  Further, in order to obtain optical characteristics that meet the purpose, resins having different degrees of substitution may be mixed and used. The mixing ratio is preferably 10:90 to 90:10 (mass ratio).

  The number average molecular weight of the cellulose ester used in the present invention is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

  The weight average molecular weight Mw and the number average molecular weight Mn of the cellulose ester can be measured using gel permeation chromatography (GPC).

  An example of measurement conditions is as follows, but is not limited to this, and an equivalent measurement method can be used.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples are used. Thirteen samples are used at approximately equal intervals.

  The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  Cellulose esters such as cellulose acetate and cellulose acetate propionate used in the present invention can be produced by known methods. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

  In addition to the polymer (A) and cellulose ester, the optical film of the present invention contains at least one of a sugar ester compound, a plasticizer, an ultraviolet absorber, an antioxidant, and fine particles, which will be described below. Also good.

(Sugar ester compound)
A sugar ester compound is mentioned as a polyester-type resin added to the said polymer (A) and a cellulose ester.

  Examples of the sugar ester compound include ester compounds in which at least one pyranose structure or furanose structure is 1 to 12 and all or part of the OH groups in the structure are esterified.

  The proportion of esterification is preferably 70% or more of the OH groups present in the pyranose structure or furanose structure.

  Examples of the sugar as a raw material for synthesizing the sugar ester compound include the following, but the present invention is not limited thereto.

  Glucose, galactose, mannose, fructose, xylose or arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose .

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable.

  Examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

  The monocarboxylic acid used for esterifying all or part of the OH groups in the pyranose structure or furanose structure is not particularly limited, and is a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic A group monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, jurylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid , Creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyroca Succinic acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratrumic acid, phthalonic acid, p- Although coumaric acid can be mentioned, benzoic acid is particularly preferable.

  An oligosaccharide ester compound can be used as a compound having 1 to 12 of at least one of pyranose structural units or furanose structural units.

  Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc., and examples of the oligosaccharides include maltooligosaccharide, isomaltooligosaccharide, fructooligosaccharide, galactooligosaccharide, and xylo-oligosaccharide. .

  Examples of sugar ester compounds are listed below, but the present invention is not limited thereto.

  Monopet SB: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Monopet SOA: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

  As addition amount of these sugar ester compounds, it is preferable to contain 0.5-30 mass% with respect to the total mass of the said polymer (A) and a cellulose ester, and it is contained especially 5-20 mass%. preferable.

(Plasticizer)
The optical film of the present invention can contain a plasticizer. The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester. It is selected from plasticizers, acrylic plasticizers and the like. Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

General formula (a) Ra- (OH) _n
(However, Ra represents an n-valent organic group, n represents a positive integer of 2 or more, and an OH group represents an alcoholic and / or phenolic hydroxyl group.)
Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as alkyl group, methoxy group or ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

Formula (b) Rb (COOH) _m (OH) _n
(Where Rb is an (m + n) -valent organic group, m is a positive integer of 2 or more and 6 or less, n is an integer of 0 or more and 4 or less, a COOH group is a carboxyl group, and an OH group is an alcoholic or phenolic hydroxyl group. Represents.)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these. Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the said polyhydric carboxylic acid ester compound, Well-known alcohol and phenols can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. And aromatic monocarboxylic acids possessed by them, or derivatives thereof.

  Of these monocarboxylic acids, acetic acid, propionic acid, and benzoic acid are particularly preferable.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

  The alcohol used for the polyvalent carboxylic acid ester may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

(Acid value)
The acid value means the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxyl group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto. For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

  The polyester plasticizer is not particularly limited, and a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used. Although it does not specifically limit as a polyester plasticizer, For example, the aromatic terminal ester plasticizer represented by the following general formula (c) can be used.

Formula (c) B-COO-((G-O-) _m -CO-A-COO-) _n G-O-CO-B
(In the formula, B represents a benzene ring and may have another substituent. G represents an alkylene group having 2 to 12 carbon atoms, an arylene group having 6 to 12 carbon atoms, or an oxyalkylene having 4 to 12 carbon atoms. Group A represents an alkylene group having 2 to 10 carbon atoms or an arylene group having 4 to 10 carbon atoms, and m and n represent a repeating unit.)
The compound of the general formula (c) is a benzene monocarboxylic acid group represented by BCOOH, an alkylene glycol group, an oxyalkylene glycol group or an aryl glycol group represented by HO— (GO—) ₁ H, HOCO-A It is synthesized from an alkylenedicarboxylic acid group or aryldicarboxylic acid group represented by —COO—H, and can be obtained by the same reaction as a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the raw material of the polyester plasticizer include, for example, benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, normal propyl benzoic acid, There are aminobenzoic acid, acetoxybenzoic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

  Examples of the alkylene glycol component of the polyester plasticizer include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propane. Diol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl- 1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentane Diol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-he There are sun diol, 2-methyl 1,8-octane diol, 1,9-nonane diol, 1,10-decane diol, 1,12-octadecane diol, etc., and these glycols are one kind or a mixture of two or more kinds. Used as. In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms as the raw material for the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. One kind or a mixture of two or more kinds can be used.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms as the raw material for the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds, respectively. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and the like.

  The polyester plasticizer has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

(Acrylic polymer)
The optical film of the present invention can also contain a (meth) acrylic polymer as a plasticizer.

  The (meth) acrylic polymer is preferably a polymer Y having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring.

  As the (meth) acrylic polymer, at least an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydroxyl group are used. The polymer X having a weight average molecular weight of 3000 to 30000 obtained by polymerization and the polymer Y having a weight average molecular weight of 500 to 3000 obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring More preferably, it is a mixture.

  More preferably, the polymer X is represented by the following general formula (X), and the polymer Y is represented by the following general formula (Y).

Formula (X)
_{- [CH 2 -C (Rc)} (CO 2 Rd) -] m - [CH 2 -C (Re) (CO 2 Rf-OH) -] n - [Xc] p -
General formula (Y)
_{Ry- [CH 2 -C (Rg)} (CO 2 Rh-OH) -] k - [Yb] q -
(In the formula, Rc, Re and Rg represent H or CH _3. Rd represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. Rf and Rh represent —CH ₂ —, —C ₂ H ₄ —. Or -C ₃ H _6- , Ry represents OH, H or an alkyl group having 3 or less carbon atoms, Xc represents a monomer unit that can be polymerized to Xa and Xb, and Yb can be copolymerized to Ya Represents a monomer unit, m, n, k, p and q represent molar composition ratios, provided that m ≠ 0, n ≠ 0, and k ≠ 0.
As addition amount of these plasticizers, it is preferable to contain 0.5-30 mass% with respect to the total mass of the said polymer (A) and a cellulose ester, It is preferable to contain especially 5-20 mass%. .

(UV absorber)
The optical film of the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet rays of 400 nm or less, and in particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, and further Preferably it is 2% or less.

  The ultraviolet absorber is not particularly limited, and examples thereof include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders, and the like. It is done.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxyphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, There are tinuvins such as tinuvin 928, all of which are commercially available from Ciba Japan and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  In addition, a discotic compound such as a compound having a 1,3,5-triazine ring is also preferably used as the ultraviolet absorber.

  The optical film preferably contains two or more ultraviolet absorbers. As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the use conditions, etc., but when the dry film thickness of the optical film is 30 to 200 μm, it is 0.5 to 10% by mass with respect to the optical film. Is preferable, and 0.6-4 mass% is still more preferable.

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the optical film may be deteriorated.

  The antioxidant has a role of delaying or preventing the optical film from being decomposed by, for example, the residual solvent amount of halogen in the optical film or phosphoric acid of the phosphoric acid plasticizer, so that the optical film of the present invention is used. It is preferable to make it contain in.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The addition amount of these compounds is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the total mass of the polymer (A) and the cellulose ester.

(Fine particles)
The optical film of the present invention preferably contains fine particles.

  Examples of the fine particles include inorganic compounds such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, and aluminum silicate. Mention may be made of magnesium silicate and calcium phosphate. Further, fine particles of an organic compound can also be preferably used. Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, polycarbonate resin, benzoguanamine resin, melamine resin Also, pulverized and classified products of organic polymer compounds such as polyolefin-based powders, polyester-based resins, polyamide-based resins, polyimide-based resins, polyfluorinated ethylene-based resins, and starches. Alternatively, a polymer compound synthesized by a suspension polymerization method, a polymer compound made spherical by a spray dry method or a dispersion method, or an inorganic compound can be used.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm.

  These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

  The content of these fine particles in the optical film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of an optical film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.), and can be used.

  Examples of the polymer include silicone resin, fluororesin and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the optical film low. In the said optical film, it is preferable that the dynamic friction coefficient of at least one surface is 0.2-1.0.

  Various additives may be batch-added to a dope that is a resin-containing solution before film formation, or an additive solution may be separately prepared and added in-line. In particular, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.

  When the additive solution is added in-line, it is preferable to dissolve a small amount of resin in order to improve mixing with the dope. A preferable amount of the resin is 1 to 10 parts by mass, and more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

  In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering), SWJ (Toray static type in-tube mixer Hi-Mixer) or the like is preferably used.

(Production method)
Next, the manufacturing method of the optical film of this invention is demonstrated.

  The optical film can be preferably used regardless of whether it is a film produced by a solution casting method or a film produced by a melt casting method.

  The optical film is produced by dissolving a resin and additives in a solvent to prepare a dope, casting a dope onto an endless metal support that moves indefinitely, and drying the cast dope as a web. It is performed by a step, a step of peeling from a metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  The process for preparing the dope will be described. It is preferable that the concentration of the resin in the dope is higher because the drying load after casting on the metal support can be reduced. However, if the concentration of the resin is too high, the load during filtration increases and the filtration accuracy deteriorates. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope may be used alone or in combination of two or more. However, it is preferable to use a mixture of a good solvent and a poor solvent of the resin in terms of production efficiency, and there are many good solvents. Is preferable in terms of the solubility of the resin. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what melt | dissolves the resin to be used independently is defined as a good solvent, and a solvent that swells or does not dissolve alone is defined as a poor solvent. For example, when cellulose ester is used as the resin, the good solvent and the poor solvent vary depending on the average acetylation degree (acetyl group substitution degree). For example, when acetone is used as the solvent, cellulose acetate ester (acetyl group substitution degree 2 .4), cellulose acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  The good solvent is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the said poor solvent is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope. Moreover, the solvent used for melt | dissolution of resin collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again. The recovery solvent may contain a small amount of additives added to the resin, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they should be reused preferably Can be purified and reused if necessary.

  As a method for dissolving the resin when preparing the dope described above, a general method can be used. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos. Moreover, after mixing resin with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of developing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of the solvent is preferably higher from the viewpoint of the solubility of the resin, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used. For example, cellulose ester or the like can be dissolved in a solvent such as methyl acetate.

  Next, the solution in which the resin is dissolved is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material resin by filtration.

Bright spot foreign matter means that when two polarizing plates are placed in a crossed Nicol state, an optical film or the like is placed between them, light is applied from one polarizing plate side, and observation is performed from the other polarizing plate side. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The expression of the difference (referred to as differential pressure) is small and preferable. A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate. A preferable support body temperature is 0-40 degreeC, and 5-30 degreeC is still more preferable. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the optical film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Yes, particularly preferably 20 to 30% by mass or 70 to 120% by mass.

  In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Further, in the optical film drying step, the web is peeled off from the metal support and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, particularly Preferably it is 0-0.01 mass% or less.

  In the film drying step, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

  In order to produce the optical film, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are held with clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

  The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but is preferably performed with hot air from the viewpoint of simplicity.

  The drying temperature in the web drying step is preferably increased stepwise from 40 to 200 ° C.

  Although the film thickness of an optical film is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20-60 micrometers.

  An optical film having a width of 1 to 4 m is used. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

(Stretching operation, refractive index control)
In the step of producing the optical film of the present invention, it is preferable to perform refractive index control, that is, retardation control by a stretching operation.

  For example, biaxial stretching or uniaxial stretching can be performed sequentially or simultaneously with respect to the longitudinal direction (film forming direction) of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction. Simultaneous biaxial stretching includes stretching in one direction and contracting the other tension by relaxing.

  It is preferable that the draw ratios in the biaxial directions perpendicular to each other are finally in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction. It is preferable to carry out in the range of 0.9 to 1.0 times in the direction and 1.2 to 2.0 times in the width direction.

  The stretching temperature is preferably 120 ° C to 200 ° C, more preferably 140 ° C to 180 ° C.

  The residual solvent in the film at the time of stretching is preferably 20 to 0%, more preferably 15 to 0%.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  It is preferable to perform the width maintenance or the transverse stretching in the film forming process by a tenter, and it may be a pin tenter or a clip tenter. In addition, you may extend | stretch sequentially, even if a conveyance direction and the width direction are extended | stretched simultaneously.

(Optical compensation film)
Since liquid crystal displays use anisotropic liquid crystal materials and polarizing plates, there is a viewing angle problem that even if a good display is obtained when viewed from the front, the display performance is degraded when viewed from an oblique direction. In order to improve the performance, it is preferable to use an optical compensation film that compensates the viewing angle. The average refractive index distribution is larger in the cell thickness direction and smaller in the in-plane direction. Therefore, an optical compensation film that can cancel this anisotropy and that has a so-called negative uniaxial structure in which the refractive index in the film thickness direction is smaller than the in-plane direction is effective. The optical film of the invention can also be used as an optical compensation film having such a function.

  When the optical film is used in the VA mode (mode using a vertically aligned liquid crystal), a mode in which a total of two sheets are used on each side of the cell (two-sheet type) and one of the upper and lower sides of the cell It may be used for any of the forms (single-sheet type) used only in

The optical film has a retardation Ro of 23 ° C. and 55% RH represented by the following formula, a wavelength of 590 nm and a wavelength of 20 to 100 nm, an Rth of 23 ° C. and 55% RH, and a wavelength of 590 nm. 70~300nm der in Ru.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x in which the refractive index is maximum in the in-plane direction of the optical film, and ny represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the optical film. , Nz represents the refractive index in the thickness direction z of the optical film, and d (nm) represents the thickness of the optical film.)
These retardation values can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments).

  When the slow axis or the fast axis of the optical film is present in the film plane and the angle formed by the fast axis and the film forming direction is θ1, θ1 is preferably −1 ° or more and + 1 ° or less, − More preferably, it is 0.5 ° or more and + 0.5 ° or less. This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

(Photoelastic coefficient)
The photoelastic coefficient of the optical film of the present invention is −5 × 10 ⁻¹² Pa ⁻¹ or more and 10 × 10 ⁻¹² Pa ⁻¹ or less with respect to light having a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. Preferably, it is from −2 × 10 ⁻¹² Pa ^{−1 to} 8 × 10 ⁻¹² Pa ^{−1 and} more preferably from 0 to 5 × 10 ⁻¹² Pa ⁻¹ .

  The photoelastic coefficient can be measured using a retardation measuring device (for example, KOBURA31PR, manufactured by Oji Scientific Instruments).

  In the present invention, the photoelastic coefficient is adjusted within the above range by optimizing the mixing mass ratio of the polymer (A) and cellulose ester according to the present invention, and adjusting the type and amount of other additives. be able to.

(Physical properties)
The moisture permeability of the optical film of the present invention is preferably 10 to 1200 g / m ² · 24 h at 40 ° C. and 90% RH. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The optical film of the present invention preferably has a breaking elongation of 10 to 80%.

  The visible light transmittance of the optical film of the present invention is preferably 90% or more, and more preferably 93% or more.

  The haze of the optical film of the present invention is preferably less than 1%, particularly preferably 0 to 0.1%.

  Further, a retardation value over a wider range can be obtained by further applying a liquid crystal layer or a resin layer to the optical film of the present invention or by further stretching it.

(Polarizer)
The optical film of the present invention can be used for a polarizing plate as a polarizing plate protective film and for a liquid crystal display device using the same. The optical film of the present invention is preferably a film that also functions as a polarizing plate protective film. In this case, it is not necessary to separately prepare an optical film having retardation separately from the polarizing plate protective film, and thus a liquid crystal display device Therefore, the manufacturing process can be simplified.

  In the liquid crystal display device, it is preferable that the polarizing plate is bonded to both surfaces of the liquid crystal cell via an adhesive layer.

  The polarizing plate can be produced by a general method. The side of the optical film of the present invention to be bonded to the polarizer is subjected to alkali saponification treatment, and is bonded to at least one surface of the polarizer (prepared by immersing and stretching in an iodine solution) using a completely saponified polyvinyl alcohol aqueous solution. It is preferable to match. Another polarizing plate protective film can be bonded to the other surface. When the optical film of the present invention is a liquid crystal display device, the optical film is preferably provided on the liquid crystal cell side of the polarizer, and a conventional polarizing plate protective film can be used as the film outside the polarizer.

  For example, as a conventional polarizing plate protective film, a commercially available cellulose ester film (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8HY-X, KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta Opto Co., Ltd.) are preferably used.

  In addition to the antiglare layer or the clear hard coat layer, the polarizing plate protective film used on the surface side of the display device preferably has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

(Liquid crystal display device)
By using a polarizing plate using the optical film of the present invention for a liquid crystal display device, the liquid crystal display device having various visibility can be produced.

  The optical film and polarizing plate of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB.

  In particular, it is preferably used for a VA (MVA, PVA) type liquid crystal display device.

  In particular, even in a large-screen liquid crystal display device with a 30-inch screen or more, it is possible to obtain a liquid crystal display device with excellent visibility such as front contrast by reducing coloring during black display due to light leakage.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Production example of polymer (A))
Although the manufacture example of the said polymer (A) of this invention is shown below, this invention is not limited to these. The weight average molecular weight was calculated by measurement using gel permeation chromatography (GPC) under the following measurement conditions.

Solvent: Tetrahydrofuran Column: TSKgel SuperHM-M (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Flow rate: 0.6ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000 to 500 samples are used. Thirteen samples are used at approximately equal intervals.

(Production Example 1: Production of polymer (A-1))
71 ml of tetrahydrofuran (hereinafter referred to as “THF”) was added to 200 ml of four-headed Kolben equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas introduction pipe, and deaerated by heating under reflux for 1 hour under a nitrogen stream. After allowing the reaction solvent to cool to room temperature, 18.9 g of methyl methacrylate, 3.5 g of hydroxyethyl methacrylate, 6.0 g of N-methylmaleimide, and 0.44 g of 2,2′-azobisisobutyronitrile were added, The reaction solution was heated to 66 ° C. and stirred for 6 hours. After cooling to room temperature, the reaction solution was poured into 500 ml of ethanol and reprecipitated. The precipitated solid was collected by filtration, washed with ethanol, and then dried at 100 ° C. and 1 Torr (1 Torr is 133.322 Pa) for 5 hours to give a white solid copolymer (A-1) 24.4 g (Mw = 32,000).

(Production Example 2: Production of polymer (A-2))
60 ml of THF was added to a 4-head Kolben with a capacity of 200 ml equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, and deaerated by heating under reflux for 1 hour under a nitrogen stream. After allowing the reaction solvent to cool to room temperature, 14.0 g of methyl methacrylate, 3.4 g of N-vinylpyrrolidone, 3.3 g of N-methylmaleimide, and 0.26 g of 2,2′-azobisisobutyronitrile were added. The reaction solution was heated to 66 ° C. and stirred for 6 hours. After cooling to room temperature, the reaction solution was poured into 400 ml of methanol and reprecipitated. The precipitated solid was collected by filtration, washed with methanol, and then dried at 100 ° C. and 1 Torr (1 Torr is 133.322 Pa) for 5 hours to obtain 15.4 g (Mw) of a white solid copolymer (A-2). = 24,000).

(Production Example 3: Production of polymer (A-3))
40 ml of THF was added to a 4-head Kolben having a capacity of 200 ml equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas introduction pipe, and the mixture was deaerated by heating under reflux for 1 hour under a nitrogen stream. After allowing the reaction solvent to cool to room temperature, 6.7 g of methyl methacrylate, 1.8 g of hydroxyethyl methacrylate, 6.0 g of N-methylmaleimide, and 0.22 g of 2,2′-azobisisobutyronitrile were added, The reaction solution was heated to 66 ° C. and stirred for 6 hours. After cooling to room temperature, the reaction solution was poured into 400 ml of methanol and reprecipitated. The precipitated solid was collected by filtration, washed with methanol, and then dried at 100 ° C. and 1 Torr (1 Torr is 133.322 Pa) for 5 hours to give 12.1 g (Mw) of a white solid copolymer (A-3). = 15,000).

  The polymers (A-4) to (A-11) and (A-14) to (A-15) shown in Table 1 were synthesized in the same manner.

(Production Example 4: Production of polymer (A-12))
90 ml of toluene was added to 30.0 g of a copolymer (Mw = 20,000) of methyl methacrylate (70 mol%) and N-vinylpyrrolidone (30 mol%), and the mixture was stirred at 40 ° C. for 24 hours. After cooling to room temperature and adding 120 ml of a 40 mass% methylamine methanol solution, the mixture was stirred for 3 hours at an internal temperature of 220 ° C. and an internal pressure of 40.8 kgf / cm ² (4.0 MPa). After allowing to cool to room temperature, the reaction mixture was concentrated under reduced pressure, and the resulting residue was dissolved in dioxane, and then poured into hexane for reprecipitation. The precipitated solid was collected by filtration, washed with hexane, and then dried at 100 ° C. and Torr (1 Torr is 133.322 Pa) for 24 hours to obtain 25.4 g (Mw) of a white solid copolymer (A-11). = 20,000).

  The polymer (A-13) shown in Table 1 was synthesized in the same manner.

  In addition, the symbol in Table 1 represents the following monomers.

MMI: N-methylmaleimide, HEMI: N-hydroxyethylmaleimide, BMI: N-butylmaleimide, CHMI: N-cyclohexylmaleimide, PHMI: N-phenylmaleimide, MGI: N-methylglutarimide, BGI: N-butylglutar Imide, MMA: methyl methacrylate, MA: methyl acrylate, HEMA: hydroxyethyl methacrylate, VP: N-vinylpyrrolidone, DMAA: N, N-dimethylacrylamide Example 1
<Preparation of optical film 101>
<Fine particle dispersion 1>
Aerosil R972V (silica fine particles; primary particle size 16 nm; manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle addition liquid 1>
With the following composition, the fine particle dispersion 1 was slowly added to a dissolution tank containing methylene chloride while sufficiently stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass (Preparation of main dope solution)
A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester 1, polymer (A-1), and fine particle additive solution 1 were charged into a pressure dissolution tank containing a solvent while stirring. This was completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester 1 (cellulose acetate propionate having an acetyl substitution degree of 1.1, a propionyl substitution degree of 1.1 and a total acyl group substitution degree of 2.2 (denoted as CAP1 in the table)
60 parts by mass Polymer (A-1) 40 parts by mass Particulate additive liquid 1 1 part by mass The above was put into a closed container and dissolved while stirring to prepare a dope solution. Next, using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

  On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast (cast) film became 75%, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m.

  The peeled optical film was stretched 30% in the width direction using a tenter while applying heat at 140 ° C. The residual solvent at the start of stretching was 15%.

  Next, drying was terminated while the drying zone was conveyed by a number of rolls. The drying temperature was 130 ° C. and the transport tension was 100 N / m.

  As described above, an optical film 101 having a dry film thickness of 40 μm was obtained.

<Preparation of optical films 102-126>
In the production of the optical film 101, optical films 102 to 126 were produced in the same manner except that the types and parts by mass of the cellulose ester (CAP1) and the polymer (A-1) were changed as shown in Table 2. The optical film 126 was produced in the same manner as in the production of the optical film 101 except that 100 parts by mass of the comparative resin 1 was used instead of the cellulose ester and the polymer (A).

  The materials used are shown below.

Cellulose ester 2: cellulose acetate propionate having an acetyl substitution degree of 0.1, a propionyl substitution degree of 1.5, and a total acyl group substitution degree of 1.6 (denoted as CAP2 in the table)
Cellulose ester 3: cellulose acetate propionate having an acetyl substitution degree of 1.6, a propionyl substitution degree of 0.9, and a total acyl group substitution degree of 2.5 (denoted as CAP3 in the table)
Cellulose ester 4: Cellulose diacetate having an acetyl substitution degree of 2.4 (denoted as DAC in the table)
Comparative resin 1 (example of cyclic olefin resin): ARTON-G7810 (manufactured by JSR)
<Evaluation of optical film>
Each optical film sample produced as described above was evaluated as described below.

(Measurement of retardation)
The retardation value of the center part of the width direction of the obtained optical film sample was measured. For measurement, an automatic birefringence meter KOBURA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) was used to measure three-dimensional birefringence at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. Was obtained by substituting into the following equation.

In-plane retardation Ro = (nx−ny) × d
Thickness direction retardation Rth = ((nx + ny) / 2−nz) × d
In the formula, d is the thickness (nm) of the film, the refractive index nx (the maximum refractive index in the plane of the film, also referred to as the refractive index in the slow axis direction), ny (the direction perpendicular to the slow axis in the film plane). ) (Refractive index of the film in the thickness direction).
(Bleed out)
The produced optical film was allowed to stand in a high temperature and high humidity atmosphere of 80 ° C. and 90% RH for 100 hours, and then bleed out was evaluated.

The presence or absence of bleed out was evaluated by observing the surface of the film.
◎: No bleed-out on the film surface ○: Partial bleed-out on the film surface is faint △: Full bleed-out on the film surface is faint x: Clear bleed-out on the film surface is clear Understandably, ◎ and ○ were judged to be practically acceptable levels.

(Measurement of photoelastic coefficient)
The both ends in the width direction of the obtained optical film sample are held, and the retardation (Ro) in the film surface is measured while applying a load, and this is divided by the thickness (d) of the film to obtain Δn (= Ro / d ) Δn was determined while changing the load, the load-Δn curve was measured, and the slope was taken as the photoelastic coefficient. The retardation (Ro) in the film plane was measured at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH using a retardation measuring device (KOBUURA 31PR, manufactured by Oji Scientific Instruments).

  Table 2 shows the in-plane retardation Ro, the thickness direction retardation Rth, and the photoelastic coefficient obtained as described above.

As is clear from Table 2, the optical films 101 to 110, 112 to 118 , 124, and 125 of the present invention have less bleed-out than the comparative optical films 111, 122, 123, and 126, and exhibit retardation. It can be seen that the optical film is excellent overall and has a small photoelastic coefficient.

Example 2
<Preparation of polarizing plate>
A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times).

  This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

  Then, the front side of the polarizer and the optical films 101 to 122, 124, and 125 are bonded according to the following steps 1 to 5, and Konica Minolta Tack KC4UY (Konica Minolta Opto's cellulose ester film) is bonded to the back side. In addition, a polarizing plate was produced.

  Step 1: The optical films 101-122, 124, 125 were immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to saponify the side to be bonded to the polarizer. An optical film was obtained.

  Process 2: The said polarizer was immersed in the polyvinyl alcohol adhesive tank of 2 mass% of solid content for 1-2 seconds.

  Step 3: Excess adhesive adhered to the polarizer in Step 2 was gently wiped off, and this was placed on the optical film treated in Step 1.

Process 4: The optical film 101-122, 124, 125 laminated | stacked at the process 3 and the said Konica Minolta Tack KC4UY cellulose-ester film are piled up on the surface of the polarizer side of a polarizer, a pressure of 20-30 N / cm < ² >, conveyance speed about 2 m Bonded at / min.

  Step 5: A sample obtained by bonding the polarizer prepared in Step 4 with the optical films 101 to 122, 124, and 125 and Konica Minoltack KC4UY in a dryer at 80 ° C. for 2 minutes, and the corresponding polarizing plate 101 ˜122, 124, 125 were prepared.

  Since the optical films 123 and 126 could not be bonded together by the alkali treatment, a polarizing plate could not be produced.

[Evaluation of polarizing plate]
Next, the adhesiveness between the optical film and the polarizer and the light resistance of the polarizing plate were evaluated as follows.

(Adhesiveness)
The polarizing plate obtained in the above manner was treated at 80 ° C. and 90% RH for 1200 hours, and the state of bonding between the optical film and the polarizer was observed and ranked according to the following criteria. The results are shown in Table 3.

A: No peeling B: Peeling is slightly observed C: Peeling is recognized D: Peeling is recognized in a very wide range Here, it was judged that A and B were practically satisfactory levels.

(Evaluation of light resistance)
The parallel transmittance (H0) and the direct transmittance (H90) of the undegraded sample were measured, and the degree of polarization was calculated according to the following equation. After that, each polarizing plate was subjected to forced deterioration treatment for 500 hours under the condition of no sunshine weather meter and no UV cut filter, and then again the parallel transmittance (H0 ′) and direct transmittance (H90 ′) after the forced deterioration treatment. Was measured, polarization degrees P0 and P500 were calculated according to the following formula, and the degree of polarization degree change was determined by the following formula.

(Calculation of polarization degree P0, P500)
Polarization degree P0 = [(H0−H90) / (H0 + H90)] ^1/2 × 100
Polarization degree P500 = [(H0′−H90 ′) / (H0 ′ + H90 ′)] ^1/2 × 100
Polarization degree change = P0−P500
P0: Polarization degree before forced deterioration treatment P500: Polarization degree after 500 hours of forced deterioration treatment The degree of polarization change obtained as described above was determined according to the following criteria, and light resistance was evaluated. The results are shown in Table 3.

A: Polarization degree change amount is less than 2% B: Polarization degree change amount is 2% or more and less than 10% C: Polarization degree change amount is 10% or more and less than 25% D: Polarization degree change amount is 25% or more , B was judged to be a level with no practical problems.

<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The polarizing plates on both sides of the 40-inch display KLV-40J3000 made in advance were peeled off, and the prepared polarizing plates 101 to 122, 124, and 125 were bonded to both surfaces of the glass surface of the liquid crystal cell, respectively.

  At that time, the direction of bonding of the polarizing plate is such that the surface of the optical film of the present invention is on the liquid crystal cell side, and the polarizing axis of the polarizing plate and the polarizing plates 101 to 122 previously bonded, The liquid crystal display devices 101 to 122, 124, and 125 were respectively manufactured so that the absorption axes of 124 and 125 were oriented in the same direction.

(Characteristic evaluation as a liquid crystal display device)
The liquid crystal display device produced as described above was evaluated as described below.

(Frame unevenness)
Each liquid crystal display device obtained above was stored for 24 hours in an environment of temperature 45 ± 2 ° C. and humidity 95 ± 3% RH. Immediately after that, it is moved to a room with a temperature of 23 ° C. and a humidity of 55% RH, and the panel backlight is turned on. 24 hours after lighting, the front luminance at the four corners in the state of black display is measured, and the average value is calculated. Note that the “four corners” here are on the diagonal line of the effective display screen and the distance from the corner is 50 mm.

  About each liquid crystal display device, generation | occurrence | production of frame unevenness was evaluated in the following four steps by ratio of the average value of the front luminance of the said four corners, and the front luminance of the screen center part. The evaluation rank is as follows. The front luminance at the center of the screen of the liquid crystal display device was set to 1. The results are shown in Table 3.

Evaluation rank A: No occurrence of frame unevenness. (Four-corner front luminance average: 1.00 to 1.05)
B: The frame unevenness cannot be recognized with the naked eye. (Four-corner front luminance average: 1.06-1.10)
C: Although it appears as a frame unevenness, there is no hindrance in use. (Four-corner front luminance average: 1.11 to 1.20)
D: There is a problem in display quality. (Four corner front luminance average: 1.21 or more)

As is clear from Table 3, polarizing plates and liquid crystal display devices using the optical films 101 to 110, 112 to 118 , 124 and 125 of the present invention are polarizing plates and liquid crystal display devices using the comparative optical films 111 and 122, respectively. Compared with the above, it can be seen that the liquid crystal display device is excellent in adhesiveness with a polarizer, has good light resistance, and is excellent in overall quality with little frame unevenness.

Claims (6)

The polymer (A) having at least one repeating unit represented by the following general formula (1) and having at least one repeating unit composed of a monomer having a hydroxyl group or an amide bond, and the cellulose ester , The content of (A) is contained within the range of 5 to 70% by mass with respect to the cellulose ester , and in the environment of 23 ° C. and 55% RH, with respect to light having a wavelength of 590 nm, the following formula: Retardation Ro represented by (I) is 20-100 nm, Rth represented by following formula (II) is 70-300 nm, The optical film characterized by the above-mentioned.

(In the formula, R ₁ represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group, and R ₂ and R ₃ each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. N is 0 or 1 is represented.)
Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x in which the refractive index is maximum in the in-plane direction of the optical film, and ny represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the optical film. , Nz represents the refractive index in the thickness direction z of the optical film, and d (nm) represents the thickness of the optical film.) In the general formula (1), optical film according to claim 1, wherein R ₁ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. The optical film according to claim 1 or 2, wherein the cellulose ester is cellulose acetate propionate and simultaneously satisfies the acyl group substitution degrees of the following formulas (1) and (2) .
Formula (1) 1.4 <= X + Y <= 2.4
Formula (2) 0.5 <= Y <= 2.0
(In the formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the propionyl group.) The optical film of any one of claims 1 to 3 has a photoelastic coefficient of −5 × 10 ⁻¹² Pa ⁻¹ or more with respect to light having a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. An optical film characterized by being 10 × 10 ⁻¹² Pa ⁻¹ or less . A polarizing plate comprising the optical film according to claim 1 on at least one surface of a polarizer. A liquid crystal display device comprising the polarizing plate according to claim 5 on at least one surface of a liquid crystal cell.