JP5233935B2 - Optical film, polarizing plate using the same, liquid crystal display device and retardation developer - Google Patents

Description

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

  Resin films such as cellulose ester, polycarbonate, and polyolefin are mainly used for optical compensation films for liquid crystal display devices for optical use. Among them, an optical film having cellulose ester is applied to polyvinyl alcohol used for a polarizer. Widely used because of its excellent compatibility.

  Further, in recent years, development of thin and light notebook personal computers and thin and large-screen TVs has progressed, and accordingly, there has been an increasing demand for thinner optical compensation films for liquid crystal display devices. However, since the cellulose ester film does not have sufficient birefringence necessary for the optical compensation film as it is, various studies have been made to impart birefringence to the cellulose ester film.

  On the other hand, the humidity durability of the cellulose ester film depends on the film thickness, and can be improved by reducing the film thickness. However, if the film pressure is reduced, the retardation value decreases. There is a need for a compound having a high retardation expression ability.

  For example, a method for obtaining an optical compensation film by adding a compound having a molecular structure having at least two aromatic rings and not sterically hindering the conformation of the two aromatic rings has been proposed (for example, Patent Document 1). See) However, when the compound described in the above-mentioned patent document is added, the expression of retardation is not sufficient, and the polarizing plate produced using this optical compensation film has a problem that the light resistance is inferior.

  In addition, a method for obtaining an optical compensation film using a rod-shaped compound (for example, see Patent Document 2) and a disk-shaped compound (for example, Patent Document 3) as a retardation developer has been proposed. However, when an optical compensation film is produced using these compounds, there is a problem that the retardation is not sufficiently developed and is easily affected by humidity fluctuations.

  As described above, the conventionally known compounds have not only insufficient retardation, but also have various problems, and further improvements have been demanded.

JP 2006-188718A Japanese Patent No. 3896404 Japanese Patent No. 4260332

  The present invention has been made in view of the above problems. Therefore, the object of the present invention is to provide an optical film having high retardation expression, good light resistance, and being less affected by fluctuations in humidity. It is in. Furthermore, it is providing the polarizing plate and liquid crystal display device with favorable durability using this optical film.

  The above object of the present invention can be achieved by the following configuration.

  1. An optical film comprising a compound represented by the following general formula (1).

(In the formula, R ₁ represents an aryl group, a heteroaryl group, or a substituent that forms an aromatic ring by combining with R _3. R ₂ and R ₇ represent a hydrogen atom or a substituent. R ₃ represents a hydrogen atom or an alkyl group. A group, a cycloalkyl group, an aryl group, a heteroaryl group or a substituent which is bonded to R ₁ to form an aromatic ring, wherein R ₄ , R ₅ and R ₆ are a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or Represents a heteroaryl group, R ₈ represents an aryl group or a heteroaryl group, n represents an integer of 0 to 4. When n is 2 or more, a plurality of R ₅ and R ₆ are the same or different. May be.)
2. 2. The optical film as described in 1 above, wherein the optical film as described in 1 has a cellulose ester.

3. 3. The optical film as described in 1 or 2 above, wherein R ₂ and R ₇ of the compound represented by the general formula (1) are hydrogen atoms.

  4). 4. The optical film as described in any one of 1 to 3, wherein the optical film has a thickness of 20 to 60 μm.

  5. Retardation Ro represented by a following formula is 20-100 nm, Rth is 70-300 nm, The optical film of any one of said 1-4 characterized by the above-mentioned.

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

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

  8). The retardation developer used for the optical film of any one of said 1-5 is a compound represented by following General formula (1).

(In the formula, R ₁ represents an aryl group, a heteroaryl group, or a substituent that forms an aromatic ring by combining with R _3. R ₂ and R ₇ represent a hydrogen atom or a substituent. R ₃ represents a hydrogen atom or an alkyl group. A group, a cycloalkyl group, an aryl group, a heteroaryl group or a substituent which is bonded to R ₁ to form an aromatic ring, wherein R ₄ , R ₅ and R ₆ are a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or Represents a heteroaryl group, R ₈ represents an aryl group or a heteroaryl group, n represents an integer of 0 to 4. When n is 2 or more, a plurality of R ₅ and R ₆ are the same or different. May be.)

  According to the present invention, it was possible to provide an optical film having high retardation expression, good light resistance, and being less affected by humidity fluctuations. Furthermore, it was possible to provide a polarizing plate and a liquid crystal display device having good durability using the optical film.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  In order to solve the above-mentioned problems, the present inventors diligently studied an optical film containing a retardation developer. As a result, the detailed reason has not been elucidated, but by using a specific cyclic ketone compound, high retardation is achieved. It has been found that an optical film having expression properties and good light resistance can be obtained. It was also found that a polarizing plate and a liquid crystal device having good durability can be obtained by using the obtained optical film.

  Specifically, the present inventors have found that the above problem can be solved when a cyclic ketone compound represented by the general formula (1) having at least two aromatic rings in which a carbonyl group and a conjugated system are connected is used, and the present invention has been achieved. It depends on you.

(Compound represented by the general formula (1))
In the general formula (1), R ₁ represents an aryl group, a heteroaryl group, or a substituent that forms an aromatic ring by bonding with R ₃ . Examples of the aryl group represented by R ₁ include a phenyl group and a naphthyl group. Examples of the heteroaryl group represented by R ₁ include a pyridyl group, a thiazolyl group, an oxazolyl group, a pyrazolyl group, an imidazolyl group, a furyl group, a thienyl group, and a pyrrolyl group. Examples of the substituent that forms an aromatic ring by combining with R ₃ represented by R ₁ include, for example, a benzene ring, a pyridine ring, a furan ring, a thiophene ring, a thiazole ring, an oxazole ring, and an imidazole ring. And the like. The aryl group represented by R ₁ , the heteroaryl group, or the substituent that forms an aromatic ring by combining with R ₃ may have a substituent, and the substituent is not particularly limited, but an alkyl group (for example, Methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.), cycloalkyl group (for example, cyclopropyl group, cyclopentyl group, cyclohexyl) Group, adamantyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), acylamino group (eg, acetylamino group, benzoylamino group, etc.), alkylthio group (eg, methylthio group, ethylthio group, etc.), arylthio group (For example, phenylthio group, naphthylthio group, etc.), alkenyl group (for example, vinyl group, 2-propyl group) Nyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group, 4-hexenyl group, cyclohexenyl group, etc.), halogen atom (for example, fluorine atom, Chlorine atom, bromine atom, iodine atom, etc.), alkynyl group (eg, propargyl group, etc.), heterocyclic group (eg, pyridyl group, thiazolyl group, oxazolyl group, pyrazolyl group, imidazolyl group, furyl group, thienyl group, pyrrolyl group) Etc.), alkylsulfonyl groups (eg, methylsulfonyl group, ethylsulfonyl group, etc.), arylsulfonyl groups (eg, phenylsulfonyl group, naphthylsulfonyl group, etc.), alkylsulfinyl groups (eg, methylsulfinyl group, etc.), arylsulfinyl groups (For example, phenylsulfinyl group), phosphono group, a Sil group (for example, acetyl group, pivaloyl group, benzoyl group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group) Group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), sulfonamide group (for example, methanesulfonamide group) Benzenesulfonamide group etc.), cyano group, alkoxy group (eg methoxy group, ethoxy group, propoxy group etc.), aryloxy group (eg phenoxy group, naphthyloxy group etc.), heterocyclic oxy group, siloxy group, acyloxy Group (for example, acetyloxy group, benzoyloxy group, etc.), sulfonic acid group, salt of sulfonic acid, aminocarbonyloxy group, amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino) Group, 2-ethylhexylamino group, dodecylamino group, etc.), anilino group (for example, phenylamino group, chlorophenylamino group, toluidino group, anisidino group, naphthylamino group, 2-pyridylamino group, etc.), imide group, ureido group ( For example, methylureido group, ethylurei group Group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), alkoxycarbonylamino group (for example, methoxycarbonylamino group, phenoxycarbonylamino group) Etc.), alkoxycarbonyl groups (eg methoxycarbonyl group, ethoxycarbonyl group, phenoxycarbonyl etc.), aryloxycarbonyl groups (eg phenoxycarbonyl group etc.), heterocyclic thio groups, thioureido groups, carboxyl groups, carboxylic acid salts , Hydroxyl groups, mercapto groups, nitro groups and the like. These substituents may be further substituted with the same substituent. R ₁ is preferably an aryl group or a heteroaryl group, and more preferably an aryl group.

In the general formula (1), when R ₁ is a substituent that forms an aromatic ring by bonding with R ₃ , the aromatic ring formed is preferably a benzene ring.

In the general formula (1), R ₂ and R ₇ represent a hydrogen atom or a substituent. The substituent represented by R ₂ and R ₇ is not particularly limited, and examples thereof include the same groups as the substituents described above for R ₁ in the general formula (1). R ₂ and R ₇ are preferably hydrogen atoms.

In the general formula (1), R ₃ represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or a substituent that forms an aromatic ring by combining with R ₁ . Examples of the alkyl group represented by R ₃ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a t-butyl group, a pentyl group, a hexyl group, an octyl group, a dodecyl group, and a trifluoromethyl group. Can do. Examples of the cycloalkyl group represented by R ₃ include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, an adamantyl group, and the like. Examples of the alkenyl group represented by R ₃ include vinyl group, 2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group, and 4-hexenyl. Group, cyclohexenyl group and the like. Examples of the aryl group represented by R ₃ include a phenyl group and a naphthyl group. Examples of the heteroaryl group represented by R ₃ include a pyridyl group, a thiazolyl group, an oxazolyl group, a pyrazolyl group, an imidazolyl group, a furyl group, a thienyl group, and a pyrrolyl group. Examples of the substituent that forms an aromatic ring by combining with R ₁ represented by R ₃ include, for example, a benzene ring, a pyridine ring, a furan ring, a thiophene ring, a thiazole ring, an oxazole ring, and an imidazole ring. And the like. The alkyl group, cycloalkyl group, aryl group, heteroaryl group represented by R ₃ or the substituent that forms an aromatic ring by combining with R ₁ may have a substituent, and the substituent is not particularly limited. but, for example, it includes the same groups as the substituent groups described above for R ₁ in the general formula (1). R ₃ is preferably a hydrogen atom, an alkyl group or a cycloalkyl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom.

In the general formula (1), when R ₃ is a substituent which is bonded to R ₁ to form an aromatic ring, the aromatic ring formed is preferably a benzene ring.

In the general formula (1), R ₄ , R ₅ and R ₆ represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heteroaryl group. When R ₄ , R _5, and R ₆ represent an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group, these groups include an alkyl group, a cycloalkyl group, represented by R _{3 in the} general formula (1), The group similar to the group demonstrated as an example of an aryl group or heteroaryl group can be mentioned. The alkyl group, cycloalkyl group, aryl group and heteroaryl group represented by R ₄ , R ₅ and R ₆ may have a substituent, and the substituent is not particularly limited. Examples thereof include the same groups as the substituents described above for R ₁ in (1). R ₄ , R ₅ and R ₆ are preferably a hydrogen atom, an alkyl group or a cycloalkyl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom.

In the general formula (1), R ₈ represents an aryl group or a heteroaryl group. When R ₈ represents an aryl group or a heteroaryl group, these groups include the same groups as those described as examples of the aryl group or heteroaryl group represented by R _{3 in the} general formula (1). it can. The aryl group or heteroaryl group represented by R ₈ may have a substituent, and the substituent is not particularly limited. For example, the same as the substituent described above for R ₁ in the general formula (1) Can be mentioned. R ₈ is preferably an aryl group, more preferably a phenyl group or a naphthyl group, and particularly preferably a phenyl group.

In the general formula (1), n represents an integer of 0 to 4. When n is 2 or more, the plurality of R ₅ and R ₆ may be the same or different. n is preferably an integer of 1 to 3, and more preferably 2.

  Specific examples of the compound represented by the general formula (1) are shown below, but the present invention is not limited thereto.

  These compounds can be produced by known methods.

  Hereinafter, although the synthesis method of the compound concerning this invention is demonstrated concretely, this invention is not limited by these.

  (Synthesis of Exemplified Compound 1)

  Benzaldehyde 5 g and sodium hydroxide 5 g were dissolved in 50 ml of ethanol and cooled to 5 ° C. 1-Tetralone 6.9g was dripped over 30 minutes, Then, it stirred at room temperature for 5 hours. The reaction solution was cooled to 5 ° C., filtered, and then washed with cooled methanol to obtain Exemplary Compound 1 (9.3 g).

  As a result of analyzing the obtained crystal by 1H-NMR and MASS spectrum, it was confirmed to be Exemplified Compound 1.

1H-NMR (400 MHz, deuterated chloroform, δ (ppm), TMS standard): 8.13 to 8.11 (m, 1H), 7.86 (s, 1H), 7.50 to 7.23 ( m, 8H), 3.143.11 (m, 2H), 2.95 to 2.92 (m, 2H)
(Synthesis of Exemplified Compound 21)

  10 g of benzaldehyde and 10 g of sodium hydroxide were dissolved in 100 ml of ethanol and cooled to 5 ° C. After adding 4.6 g of cyclohexanone dropwise over 30 minutes, the mixture was stirred at room temperature for 5 hours. The reaction solution was cooled to 5 ° C., filtered, and then washed with cooled methanol to obtain Exemplary Compound 1 (10.3 g).

  As a result of analyzing the obtained crystal by 1H-NMR and MASS spectrum, it was confirmed to be Exemplified Compound 21.

1H-NMR (400 MHz, deuterated chloroform, δ (ppm), TMS standard): 7.82 (s, 2H), 7.50 to 7.33 (m, 10H), 2.97 to 2.93 ( m, 4H), 1.84 to 1.79 (m, 2H)
The retardation developing agent represented by the general formula (1) according to the present invention can be contained by appropriately adjusting the amount to give a desired retardation. It is preferable to contain 1-15 mass%, and it is preferable to contain 2-10 mass% especially. If it exists in this range, sufficient retardation can be provided to the cellulose ester of this invention, and it is preferable.

(Cellulose ester)
Although it does not specifically limit as a cellulose ester used for the cellulose-ester film which concerns on the optical film of this invention, It is preferable that it is a C2-C22 linear or branched carboxylic acid ester, and these carboxylic acids form a ring. It may be an ester of an aromatic carboxylic acid. 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.

  Preferred cellulose esters, specifically, cellulose esters include, in addition to cellulose acetate, propionate groups other than acetyl groups such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate, or Examples include mixed fatty acid esters of cellulose to which butyrate groups are bonded.

  As a preferable cellulose ester used for this invention, what satisfies the following formula (a) and (b) simultaneously is preferable.

Formula (a) 2.0 ≦ X + Y ≦ 3.0
Formula (b) 0 ≦ Y ≦ 1.5
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group, or a mixture thereof.

  Of these, cellulose acetate (Y = 0) and cellulose propionate (Y; propionyl group, Y> 0) are most preferably used. Cellulose acetate propionate satisfies 1.0 ≦ X ≦ 2.5, preferably 0.1 ≦ Y ≦ 1.5, and 2.0 ≦ X + Y ≦ 3.0. The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  In addition, 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 cellulose ester and the compound represented by the general formula (1), the optical film of the present invention includes a sugar ester compound, a plasticizer, an ultraviolet absorber, an antioxidant, and fine particles described below. At least one may be added.

(Sugar ester compound)
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 ester compound of the present invention 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 of the present invention is not particularly limited, and known aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, An aromatic 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, serotic 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, veratrumic 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.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 at least one of the pyranose structure or furanose structure according to the present invention.

  Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc. Examples of oligosaccharides that can be applied to the present invention include maltooligosaccharides, isomaltoligosaccharides, fructooligosaccharides, galactooligosaccharides, xylooligos. Sugar.

  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. The sugar ester compound is preferably added in an amount of 0.5 to 30% by mass with respect to the cellulose ester. 5 to 20% by mass is preferable.

(Plasticizer)
The cellulose ester 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).

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, 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.

  Although there is no restriction | limiting in particular in the molecular weight of a polyhydric alcohol ester, It is preferable that it is 300-1500, and it is more preferable that it is 350-750. 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
(However, Rb is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group represents a carboxyl group, and an OH group represents an alcoholic or phenolic hydroxyl group.)
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 polyhydric carboxylic acid ester compound which can be used for this invention, 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. The number of carbon atoms is more preferably 1 to 20, and particularly preferably 1 to 10 carbon atoms. 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. The number of carbon atoms is more preferably 1 to 20, and particularly preferably 1 to 10 carbon atoms.

  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 benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. And aromatic monocarboxylic acids possessed by them, or derivatives thereof. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  Although there is no restriction | limiting in particular in the molecular weight of a polyhydric carboxylic acid ester compound, It is preferable that it is the range of molecular weight 300-1000, and it is more preferable that it is the range of 350-750. 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 that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention 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.

General formula (c) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (c), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the polyester plasticizer used in the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer that can be used in the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1, 3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neo Pentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3-dimethylolheptane) 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-penta Diol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. It is used as one kind or a mixture of two or more kinds. In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  In addition, examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. It can be used as a seed or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of 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. 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 used in the present invention 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 cellulose ester film according to 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. Polymer X having a weight average molecular weight of 3000 to 30000 obtained by polymerization, and 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.

  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) -] in k- [Yb] q- (wherein, Rc, Re, Rg is, .rd representing H or CH ₃ the number of carbon atoms 1 to 12 represents an alkyl group or a cycloalkyl group, Rf or Rh represents —CH ₂ —, —C ₂ H ₄ — or —C ₃ H ₆ —, Ry represents OH, H or an alkyl having 3 or less carbon atoms. Xc represents a monomer unit polymerizable to Xa and Xb, Yb represents a monomer unit copolymerizable to Ya, and m, n, k, p and q represent molar composition ratios. (However, m ≠ 0, n ≠ 0, k ≠ 0, m + n + p = 100, k + q = 100.)
The amount of these plasticizers added is preferably 0.5 to 30% by mass, and particularly preferably 5 to 20% by mass with respect to the cellulose ester.

(UV absorber)
The cellulose ester film according to the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less. Particularly, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, particularly Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -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 ultraviolet absorber preferably used in the present invention is a benzotriazole ultraviolet absorber, a benzophenone ultraviolet absorber, or a triazine ultraviolet absorber, and particularly preferably a benzotriazole ultraviolet absorber or a benzophenone ultraviolet absorber.

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

  It is preferable that the polarizing plate protective film concerning this invention contains 2 or more types of 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 operating conditions, etc., but when the dry film thickness of the polarizing plate protective film is 30 to 200 μm, it is 0.5 with respect to the polarizing plate protective film. 10 mass% is preferable, and 0.6-4 mass% is 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 cellulose ester film may be deteriorated.

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

  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 amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose derivative.

(Fine particles)
The cellulose ester film according to the present invention preferably contains fine particles.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, 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 size of the fine particles is preferably 5 to 400 nm, 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 polarizing plate protective film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective 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 polarizing plate protective film low. In the polarizing plate protective film used in the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

  Various additives may be batch-added to a dope that is a cellulose ester-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 cellulose ester in order to improve mixing with the dope. The amount of the cellulose ester is preferably 1 to 10 parts by mass, 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 cellulose-ester film which concerns on the optical film of this invention is demonstrated.

  The cellulose ester film according to the present invention can be preferably used whether it is a film produced by a solution casting method or a film produced by a melt casting method.

  The cellulose ester film according to the present invention is prepared by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support, and casting the dope. Is performed by a step of drying as a web, 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. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. 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, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester. 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 dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent. Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, cellulose acetate (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.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention 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 a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again. The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. 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 mamaco. Moreover, after mixing a cellulose ester 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 a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, 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 particularly preferably 70 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, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution 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 particularly 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 cellulose ester 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, Most 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 particularly 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 particularly 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 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 cellulose ester 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. Especially preferably, it is 20-30 mass% or 70-120 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 drying step of the cellulose ester film, the web is peeled 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, Especially 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 used in the present invention, 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 a cellulose-ester film is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is preferably 10 to 100 μm. More preferably, it is 20-60 micrometers.

  The cellulose ester film according to the present invention has a width of 1 to 4 m. 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 cellulose ester film according to 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 stretching the other while relaxing the tension.

  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 between the rolls. 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 performance, a viewing angle compensator is necessary. The average refractive index distribution is larger in the cell thickness direction and smaller in the in-plane direction. Therefore, a compensation plate that can cancel out this anisotropy and that has a so-called negative uniaxial structure in which the refractive index in the film thickness direction is smaller than that in the in-plane direction is effective. The optical film can also be used as an optical compensation film having such a function.

  When the optical film of the present invention is used in the VA mode, a mode in which a total of two sheets are used on each side of the cell (two-sheet type) and a mode in which only one of the upper and lower sides of the cell is used (one sheet) Type).

  In the cellulose ester film according to the present invention, the retardation Ro represented by the following formula is 23 ° C. and 55% RH, and the wavelength is 590 nm and 20 to 100 nm, Rth is 23 ° C. and 55% RH. The wavelength is preferably 70 to 300 nm at 590 nm.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(Where nx represents the refractive index in the direction x where the refractive index is maximum in the in-plane direction of the cellulose ester film, and ny is the refractive index in the direction y perpendicular to the direction x in the in-plane direction of the cellulose ester film. Nz represents the refractive index in the thickness direction z of the cellulose ester film, and d (nm) represents the thickness of the optical film.) These retardation values are automatic birefringence meters KOBRA-21ADH (Oji Scientific Instruments). Can be measured.

  When the slow axis or the fast axis of the cellulose ester film according to the present invention is present in the film plane and the angle formed with 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.

(Physical properties)
The moisture permeability of the optical film according to 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 according to the present invention preferably has a breaking elongation of 10 to 80%.

  The optical film according to the present invention preferably has a visible light transmittance of 90% or more, more preferably 93% or more.

  The haze of the optical film according to 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 according to the present invention, or by further stretching it.

(Polarizer)
The optical film which concerns on this invention can be used for the polarizing plate which used the polarizing plate protective film, and the liquid crystal display device of this invention using the same. The cellulose ester film according to the present invention is preferably a film that also functions as a polarizing plate protective film, and in that case, it is not necessary to separately prepare an optical film having a phase difference separately from the polarizing plate protective film. The manufacturing process can be simplified by reducing the thickness of the display device.

  In the liquid crystal display device of the present invention, the polarizing plate according to the present invention is preferably bonded to both surfaces of the liquid crystal cell via an adhesive layer.

  The polarizing plate according to the present invention can be produced by a general method. The cellulose ester film according to the present invention is preferably bonded to at least one surface of a polarizer produced by subjecting the polarizer side to alkali saponification treatment and immersion drawing in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. . Another polarizing plate protective film can be bonded to the other surface. When the cellulose ester film according to the present invention is a liquid crystal display device, it 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 the polarizing plate using the optical film of the present invention for a liquid crystal display device, various liquid crystal display devices of the present invention having excellent 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 described below with reference to examples, but the present invention is not limited thereto.

Example 1
<Production of Cellulose Ester Film 101>
<Fine particle dispersion 1>
Fine particles (Aerosil R972V 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>
The fine particle dispersion 1 was slowly added to the dissolution tank containing methylene chloride with sufficient 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 A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester A was added to a pressurized dissolution tank containing a solvent while stirring. This is 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 A: Cellulose triacetate with an acetylation degree of 60.9% (described as TAC in the table) 100 parts by mass Retardation developer: Exemplified compound 1 3 parts by mass Monopet SB (first Manufactured by Kogyo Seiyaku Co., Ltd., described as BzSc in the table) 5 parts by mass Particulate additive solution 1 1 part by mass The above was put into a sealed 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 was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m.

  The peeled cellulose ester film was stretched 20% 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, a cellulose ester film 101 having a dry film thickness of 40 μm was obtained.

<Production of cellulose ester films 102-122>
In producing the cellulose ester film 101, cellulose ester films 102 to 122 were produced in the same manner except that the type of cellulose ester or the additive in place of the exemplified compound 1 was changed as shown in Table 1. In addition, the addition amount of the cellulose ester replaced with the used cellulose ester (TAC) was the same mass part as the cellulose ester (TAC).

  Details of the materials used in Example 1 are shown below.

  Cellulose ester B: cellulose acetate propionate having an acetyl substitution degree of 1.56, a propionyl substitution degree of 0.9, and a total acyl group substitution degree of 2.46 (denoted as CAP in the table) Cellulose ester C: degree of acetylation 55.0 % Cellulose diacetate (described as DAC in the table) The structure of the comparative compound is as follows.

<< Evaluation of cellulose ester film >>
Each cellulose ester film sample produced as described above was evaluated as described below. The results are shown in Table 1.

(Retardation value)
The average refractive index of the film constituting material was measured using an Abbe refractometer (4T). Moreover, the thickness of the film was measured using a commercially available micrometer.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), film retardation measurement was performed at a wavelength of 590 nm in a film that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH. went. The above average refractive index and film thickness were input into the following formulas, and the values of in-plane retardation Ro and thickness direction retardation Rth were determined. The direction of the slow axis was also measured at the same time.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(Where nx is the maximum refractive index in the film plane, ny is the refractive index in the direction perpendicular to nx, nz is the refractive index in the film thickness direction, and d is the thickness (nm) of the film.)
(Retardation fluctuation rate against humidity change)
The retardation values of the produced cellulose ester films were respectively determined as described above, and the Rth (a) variation rate (%) was determined from the values. In addition, the one where a fluctuation rate is smaller is preferable.

  The Rth (a) variation was as follows: Rth (b) was conditioned at 23 ° C. and 20% RH for 5 hours, and then the Rth value measured in the same environment was measured as Rth (b). After the same film was continuously conditioned at 23 ° C. and 80% RH for 5 hours, the Rth value measured in the same environment was determined and this was defined as Rth (c), and Rth (a) was determined from the following equation.

Rth (a) = | Rth (b) −Rth (c) | / Rth (b) × 100 (%)
Furthermore, the humidity-controlled sample was measured again in an environment of 23 ° C. and 55% RH, and it was confirmed that this change was a reversible change.

  As is apparent from Table 1, the cellulose ester films 101 to 118 of the present invention are superior in practicality to the retardation development and practically superior to the retardation fluctuations in comparison with the comparative cellulose ester films 119 to 121. It turns out that it is an optical film. In addition, the cellulose ester film 122 which does not contain a retardation developer has a small retardation value and has no function as an optical compensation film.

Example 2
Cellulose was obtained in the same manner as in Example 1 except that the dope liquid used in the production of the cellulose ester film 101 of Example 1 was used and the flow rate of the dope liquid at the time of casting was changed to a film thickness as shown in Table 2. Ester films 201-206 were produced and evaluated in the same manner as in Example 1.

  As is clear from Table 1, it can be seen that the cellulose ester films 201 to 206 of the present invention are excellent in retardation development, and the variation in retardation humidity is small. Further, it can be seen that the effect is particularly high in 202 to 205 having a film thickness of 20 to 60 μm.

Example 3
<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.

  Subsequently, a polarizer, the cellulose ester films 101 to 121 and 201 to 206, and Konica Minolta Tack KC4UY (Konica Minolta Opto Co., Ltd. cellulose ester film) are bonded to the back surface in accordance with the following steps 1 to 5. Was made.

  Step 1: Soaked in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain a saponified cellulose ester film on the side to be bonded to the polarizer.

  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 lightly wiped off, and this was placed on the cellulose ester film treated in Step 1.

Step 4: The cellulose ester films 101 to 121 and 201 to 206 laminated in Step 3 and the polarizer were bonded to the back side cellulose ester film at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Process 5: The sample which bonded the polarizer produced in the process 4, the cellulose-ester films 101-121, 201-206, and Konica Minoltack KC4UY in the dryer of 80 degreeC for 2 minutes is dried, and the polarizing plates 101-121. 201-206 were produced.

<< Evaluation of polarizing plate >>
Next, the durability of the polarizing plate was evaluated as follows. The results are shown in Table 3.

(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 that there was no UV cut filter, and again, parallel transmittance (H0 ′) and direct transmittance (H90 ′) after 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 degree of polarization 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.

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 practically acceptable level.

(Heat resistant)
Two 500 mm × 500 mm polarizing plate samples obtained as described above were heat-treated (conditions: left at 100 ° C. for 90 hours at 90 ° C.), and either the vertical or horizontal center line portion when placed in an orthogonal state. The length of the blank portion of the larger edge was measured, the ratio to the side length (500 mm) was calculated, and the determination was made as follows according to the ratio. Edge blanking can be determined visually by the fact that the edge portion of the polarizing plate that does not transmit light in an orthogonal state passes light. In the state of the polarizing plate, the display of the edge portion becomes invisible.

A: Edge whiteness is less than 5% (a level that is not a problem as a polarizing plate)
B: White outline of edge is 5% or more and less than 10% (a level at which there is no problem as a polarizing plate)
C: White edge of edge is 10% or more and less than 20% (a level that can be managed as a polarizing plate)
D: Edge blank is 20% or more (a problematic level as a polarizing plate)
Here, it was determined that A and B were at a level having no practical problem.

  As can be seen from Table 3, the polarizing plates 101 to 118 and 201 to 206 of the present invention are practically excellent polarizing plates having better durability than the comparative polarizing plates 119 to 121.

Example 4
<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 121 and 201 to 206 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 cellulose ester film of the present invention is on the liquid crystal cell side, and the absorption axis is in the same direction as the polarizing plate previously bonded. Thus, liquid crystal display devices 101 to 121 and 201 to 206 were produced.

《Characteristic evaluation as a liquid crystal display device》
The liquid crystal display device produced as described above was evaluated as described below. The results are shown in Table 4.

(Front contrast unevenness)
The measurement was performed after the backlight of each liquid crystal display device was lit continuously for one week in an environment of 23 ° C. and 55% RH. For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure the luminance from the normal direction of the display screen of white display and black display with a liquid crystal display device, and the ratio was defined as the front contrast.

Front contrast = Brightness of white display measured from the normal direction of the display device / Brightness of black display measured from the normal direction of the display device Measure the front contrast of any 5 points on the liquid crystal display device, and use the following criteria evaluated.

A: Front contrast is 0 to less than 5% variation and unevenness is small B: Front contrast is less than 5 to 10% variation and slightly uneven C: Front contrast is 10% or more variation, Here, A and B were judged to be practically satisfactory levels.

(Viewing angle degradation)
The viewing angle of the liquid crystal display device was measured using EZ-Contrast 160D manufactured by ELDIM in an environment of 23 ° C. and 55% RH. Subsequently, the viewing angle of the produced liquid crystal display device was measured in an environment of 23 ° C., 20% RH, and further 23 ° C., 80% RH, and evaluated according to the following criteria. Finally, viewing angle measurement was performed again in an environment of 23 ° C. and 55% RH, and it was confirmed that the change during the measurement was a reversible fluctuation. These measurements were performed after the liquid crystal display device was placed in the environment for 5 hours.

A: No viewing angle variation is observed B: Viewing angle variation is slightly recognized C: Viewing angle variation is observed Here, A and B were determined to be at a level that is not problematic in practice.

  As is clear from Table 4, the liquid crystal display devices 101 to 118 and 201 to 206 using the polarizing plates 101 to 118 and 201 to 206 of the present invention are the liquid crystal display devices 119 to 119 using the comparative polarizing plates 119 to 121. Compared to 121, it can be seen that the liquid crystal display device is extremely stable and excellent in durability with no front contrast unevenness and no change in viewing angle even under conditions of changing humidity.

Claims (8)

An optical film comprising a compound represented by the following general formula (1).

(In the formula, R ₁ represents an aryl group, a heteroaryl group, or a substituent that forms an aromatic ring by combining with R _3. R ₂ and R ₇ represent a hydrogen atom or a substituent. R ₃ represents a hydrogen atom or an alkyl group. A group, a cycloalkyl group, an aryl group, a heteroaryl group or a substituent which is bonded to R ₁ to form an aromatic ring, wherein R ₄ , R ₅ and R ₆ are a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or Represents a heteroaryl group, R ₈ represents an aryl group or a heteroaryl group, n represents an integer of 0 to 4. When n is 2 or more, a plurality of R ₅ and R ₆ are the same or different. May be.)   The optical film according to claim 1, comprising a cellulose ester. The optical film according to claim 1, wherein R ₂ and R ₇ of the compound represented by the general formula (1) are hydrogen atoms.   The film thickness of the said optical film is 20-60 micrometers, The optical film of any one of Claims 1-3 characterized by the above-mentioned. Retardation Ro represented by a following formula is 20-100 nm, Rth is 70-300 nm, The optical film of any one of Claims 1-4 characterized by the above-mentioned.
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.)   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 6 on at least one surface of a liquid crystal cell. The retardation developer used for the optical film of any one of Claims 1-5 is a compound represented by following General formula (1).

(In the formula, R ₁ represents an aryl group, a heteroaryl group, or a substituent that forms an aromatic ring by combining with R _3. R ₂ and R ₇ represent a hydrogen atom or a substituent. R ₃ represents a hydrogen atom or an alkyl group. A group, a cycloalkyl group, an aryl group, a heteroaryl group or a substituent which is bonded to R ₁ to form an aromatic ring, wherein R ₄ , R ₅ and R ₆ are a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or Represents a heteroaryl group, R ₈ represents an aryl group or a heteroaryl group, n represents an integer of 0 to 4. When n is 2 or more, a plurality of R ₅ and R ₆ are the same or different. May be.)