JP5569437B2 - 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.

  Resin films such as cellulose ester, polycarbonate, and polyolefin are mainly used for optical compensation films for liquid crystal display devices as optical films. Among them, an optical film (cellulose ester film) having a cellulose ester is used as a polarizer. It is widely used because of its excellent bonding properties to the polyvinyl alcohol used.

  Since the cellulose ester film as it is does not have sufficient birefringence necessary for the optical compensation film, various studies have been made to impart birefringence to the cellulose ester film.

  For example, Patent Document 1 proposes a method for obtaining an optical compensation film by adding a compound having a molecular structure that has at least two aromatic rings and does not sterically hinder the conformation of the two aromatic rings. Yes. However, when the compound described in Patent Document 1 is added, the expression of retardation is not sufficient, and the polarizing plate produced using this optical compensation film is inferior in durability such as light resistance and wet heat resistance. There was a problem.

  In addition, development of thin and light notebook PCs and thin and large-screen TVs has progressed, and accordingly, optical compensation films for liquid crystal display devices have been increasingly demanded for thinner, larger and higher performance. . The humidity durability of the cellulose ester film depends on the film thickness and can be improved by reducing the film thickness. On the other hand, if the film thickness is reduced, the retardation value decreases. There is a need for compounds with high expression.

  On the other hand, an optical film containing a quinazolone compound as an ultraviolet absorber has been proposed. Patent Documents 2 and 3 propose quinazolone compounds having a specific substituent, but it has been found that the quinazolone compounds described in the patents have poor bleedout resistance. Patent Documents 3 and 4 propose bisquinazolone compounds linked by an aromatic ring. A polarizing plate prepared using an optical compensation film containing the compound described in the patent and a liquid crystal using the polarizing plate It has been found that the display device is inferior in durability such as light resistance and wet heat resistance. In addition, there were problems of front contrast unevenness and viewing angle deterioration due to heat and humidity.

  As described above, conventionally known retardation developing agents are not only sufficiently exhibiting retardation, but also have various problems, and further improvements have been demanded.

JP 2006-188718A JP 2010-59123 A JP 2010-77064 A JP 2009-242641 A

  This invention is made | formed in view of the said subject, The objective is to provide the optical film which has high retardation expression and was excellent in bleed-out tolerance. 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 is achieved by the following configurations.

1. In the optical film containing a cellulose ester, the following general formula (1) :

(In the formula, R ₁ and R ₂ represent a hydrogen atom or a substituent. R ₃ and R ₄ represent a hydrogen atom or a substituent having a negative Hammett's σp value. L ₁ and L ₂ are divalent. A represents a linking group, A represents a 1-9 valent aromatic group or a 1-9 valent heteroaromatic group, m represents 0 or 1, n represents an integer of 0 to 8, r and s represent Represents an integer of 1 to 4)
Containing a compound represented by
Following formula:
Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x where the refractive index is maximum in the in-plane direction of the optical film, 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.)
Retardation Ro is 20-100 nm and Rth is 70-300 nm at a measurement wavelength of 590 nm.
2. 2. The optical film as described in 1 above, wherein n in the general formula (1) is 0.

  3. 3. The optical film as described in 1 or 2 above, wherein the optical film has a thickness of 15 to 60 μm.

4 . A polarizing plate having the optical film according to any one of 1 to 3 on at least one surface of a polarizer.

5 . 5. A liquid crystal display device comprising the polarizing plate according to 4 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 high retardation expression and excellent bleed-out resistance. Furthermore, a polarizing plate and a liquid crystal display device having good durability can be provided using the optical film.

  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 on an optical film containing a retardation developer that can solve the above-mentioned problems, the present inventors have a high retardation expression and a bleed-out resistance by using a specific quinazolone compound. It has been found that an excellent optical film can be obtained. Moreover, when the obtained optical film was used, it discovered that the polarizing plate and liquid crystal display device which were excellent in durability were obtained. Although the detailed reason has not been elucidated, quinazolone compounds having an aromatic group or a heteroaromatic group are excellent in retardation and have a hydrogen atom or electron donating property on the benzene ring of two rings of the quinazolone structure. By having a substituent, the affinity with the cellulose ester is increased, and the bleed-out resistance is considered to be improved. In addition, when two or more quinazolone structures are directly connected to a 5-membered or 6-membered aromatic group or heteroaromatic group, the absorption wavelength becomes longer, so that the light resistance and heat resistance are reduced. It is considered that the light resistance and the heat and humidity resistance are improved by passing through.

  When the quinazolone compound having an aromatic group or a heteroaromatic group and having a specific substituent is used as a retardation developer, the present inventors have found that the above problems can be solved and have reached the present invention.

[Compound represented by the general formula (1)]
First, the compound represented by the general formula (1) according to the present invention will be described.

In the general formula (1), R ₁ and R ₂ represent a hydrogen atom or a substituent. The substituent represented by R ₁ and R ₂ is not particularly limited, and examples thereof include alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, Octyl, dodecyl, trifluoromethyl, etc.), cycloalkyl (eg, cyclopropyl, cyclopentyl, cyclohexyl, adamantyl, etc.), aryl (eg, phenyl, naphthyl, etc.), acylamino ( For example, acetylamino group, benzoylamino group, etc.), alkylthio group (eg, methylthio group, ethylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkenyl group (eg, vinyl group, 2-propenyl group). 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, -Methyl-3-butenyl group, 4-hexenyl group, cyclohexenyl group, styryl group, etc.), halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkynyl group (for example, propargyl group, etc.) A heterocyclic group (for example, pyridyl group, thiazolyl group, oxazolyl group, pyrazolyl group, imidazolyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, etc.), arylsulfonyl group (for example, phenylsulfonyl group, Naphthylsulfonyl group etc.), alkylsulfinyl group (eg methylsulfinyl group etc.), arylsulfinyl group (eg phenylsulfinyl group etc.), phosphono group, acyl group (eg acetyl group, pivaloyl group, benzoyl group etc.), carbamoyl Groups (for example, aminocarboni 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, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group), sulfonamide Group (for example, methanesulfonamide group, benzenesulfonamide group, etc.), cyano group, alkoxy group (for example, methoxy group, ethoxy group, propoxy group) Etc.), aryloxy groups (eg phenoxy group, naphthyloxy group etc.), heterocyclic oxy groups, siloxy groups, acyloxy groups (eg acetyloxy group, benzoyloxy group etc.), sulfonic acid groups, sulfonic acid salts, Aminocarbonyloxy group, amino group (eg, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc.), anilino group (eg, phenylamino group, Chlorophenylamino group, toluidino group, anisidino group, naphthylamino group, 2-pyridylamino group, etc., imide group, ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecyl group) Ureido group, phenyl Raid group, naphthylureido group, 2-pyridylaminoureido group, etc.), alkoxycarbonylamino group (eg, methoxycarbonylamino group, phenoxycarbonylamino group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, phenoxycarbonyl) Etc.), aryloxycarbonyl groups (for example, phenoxycarbonyl groups, 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 and R ₂ are preferably a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, and more preferably a hydrogen atom or an alkyl group.

In the general formula (1), R ₃ and R ₄ represent a hydrogen atom or a substituent having a negative Hammett σp value. When R ₃ and R ₄ are a hydrogen atom or a substituent having a negative Hammett's σp value, an optical film having excellent bleed-out resistance can be obtained.

  Here, the σp value used in this specification will be described. Hammett's rule is a method described in 1935 in order to quantitatively discuss the effect of substituents on the reaction or equilibrium of benzene derivatives. P. A rule of thumb proposed by Hammett, which is widely accepted today. Substituent constants determined by Hammett's rule include a σp value and a σm value, and these values can be found in many general books. A. Dean, “Lange's Handbook of Chemistry”, 12th edition, 1979 (McGraw-Hill) and “Areas of Chemistry” special edition, 122, 96-103, 1979 (Nankodo). In the present invention, each substituent is limited or explained by Hammett's substituent constant σp value, but this is limited to only a substituent having a known value that can be found in the above-mentioned book. Needless to say, it also includes a substituent that would be included in the range when the value was unknown based on Hammett's law even if the value was unknown. In the present specification, the σp value represents such a meaning.

In the general formula (1), examples of the substituent having a negative Hammett's σp value represented by R ₃ and R ₄ include an alkoxy group (eg, methoxy group, ethoxy group, propoxy group, etc.), alkyl Examples include a group (for example, methyl group, ethyl group, propyl group, etc.), a hydroxyl group, an amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, etc.). The substituent represented by R ₃ and R ₄ is preferably an alkoxy group, an alkyl group or a hydroxyl group, and more preferably a methoxy group, a methyl group or a hydroxyl group.

In the general formula (1), L ₁ and L ₂ represent a divalent linking group. The divalent linking group represented by L ₁ and L ₂ is not particularly limited. For example, a divalent alkyl group (methylene group, 1,2-ethylene group, 1,2-propylene group, 1, 3-propylene group, 1,4-butylene group, etc.), divalent cycloalkyl group (1,2-cyclohexylene group, 1,4-cyclohexylene group, etc.), divalent aryl group (1,4-phenylene, etc.) Group, 1,3-phenylene group, 1,4-naphthylene group, 2,6-naphthylene group, 9,10-anthracenylene, etc.), divalent heterocyclic group (2,5-pyridylene group, 1,3-imidazolene) Group, 3,5-thienylene group, 2,5-thienylene, 2,5-furylene, etc.), —CH═CH—, —NR ₅ —, —O—, —S—, —C (═O) —, -S (= _{O) 2} - or a divalent connecting selected from combinations of these groups It can be given to the group. The divalent alkyl group, divalent cycloalkyl group, divalent aryl group, and divalent cycloaryl group represented by L ₁ and L ₂ may have a substituent, and the substituent is particularly limited. For example, the same group as the substituent represented by R ₁ in the general formula (1) can be exemplified. L ₁ and L ₂ represent a divalent alkyl group, —NR ₅ —, —O—, —S—, —C (═O) —, —S (═O) ₂ —, or a group of these ₂ to 3 It is preferable that they are a divalent linking group in combination, a methylene group, —NR ₅ —, —O—, —S—, —C (═O) —, —S (═O) ₂ — or a group thereof. More preferably, it is a divalent linking group in which two are combined.

In the general formula (1), R ₅ represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group. When R ₅ represents an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, these groups include, for example, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group represented by R ₁ in the general formula (1). Examples of the cyclic group include the same groups as those described above, and these groups may have a substituent. Examples of the substituent include R ₁ in the general formula (1). Examples thereof include the same groups as the substituents that the alkyl group, cycloalkyl group, aryl group or heterocyclic group represented by may have.

In the present invention, the compound represented by the general formula (1) is characterized by having a divalent linking group represented by L ₂ . When the linking group represented by L _{2 is included} , an optical film excellent in light resistance and wet heat resistance can be obtained.

  In the general formula (1), A represents a 1-9 valent aromatic ring or a 1-9 valent heteroaromatic ring. The aromatic group or heteroaromatic group represented by A may be a single ring or a condensed ring. When the aromatic ring or heteroaromatic ring represented by A is a single ring, it is preferably a 5- to 10-membered ring, more preferably a 5-membered ring or a 6-membered ring. When the aromatic ring or heteroaromatic ring represented by A is a condensed ring, a 2-10 cyclic aromatic ring condensed with a 5-10 membered ring is preferable, and a 5-6 membered ring condensed with 2 A 5-cyclic aromatic ring is more preferable, and a bicyclic aromatic ring condensed with a 5- to 6-membered ring is particularly preferable. Examples of the aromatic ring represented by A include a benzene ring and a naphthalene ring. Examples of the heteroaromatic ring represented by A include pyrrole ring, pyrazole ring, triazole ring, tetrazole ring, furan ring, thiophene ring, oxazole ring, thiazole ring, imidazole ring, pyridine ring, pyridazine ring, pyrazine ring, Examples thereof include a pyrimidine ring, a triazine ring, an indole ring, a benzofuran ring, a benzothiophene ring, a benzoxazole ring, a benzothiazole ring, and a benzimidazole ring. A is preferably a 5-membered or 6-membered ring, and more preferably a benzene ring.

In the general formula (1), A may have a substituent, and the substituent that A may have is not particularly limited. For example, R _{1 in the} general formula (1) and It includes the same groups as the substituents represented by R _2.

  In the general formula (1), m represents 0 or 1.

  In the said General formula (1), n represents the integer of 0-8. n is preferably an integer of 0 to 2, more preferably 0 or 1, and particularly preferably 0. In this case, the compatibility with the cellulose ester is particularly excellent, and an optical film particularly excellent in light resistance and wet heat resistance is obtained, which is preferable.

  In the said General formula (1), r and s represent the integer of 1-4. r and s are preferably integers of 1 to 2. At this time, an optical film having particularly excellent bleed-out resistance is obtained, which is preferable.

  Specific examples of the compound represented by the general formula (1) are given below, but the present invention is not limited to the following specific examples.

  These compounds can be produced by known methods.

<Synthesis example>
Hereinafter, although the synthesis method of the compound based on this invention is demonstrated concretely, this invention is not limited to these.

  (Synthesis of Exemplary Compound A-6)

  At room temperature, 2.86 g of compound A, 4.12 g of compound B, 3.28 g of sodium hydrogen sulfate, and 30 ml of dimethylacetamide were mixed and refluxed at 150 ° C. for 6 hours while dehydrating. After completion of the reaction, the reaction mixture was cooled to room temperature and 30 ml of pure water was added. The solid precipitated by the reaction was filtered and washed pure. 50 ml of acetone was added to the obtained solid and stirred at room temperature for 30 minutes. The solid was filtered, washed with acetone, and dried to obtain 6.00 g of Exemplified Compound A-6.

As a result of analyzing the obtained solid by ¹ H-NMR and MASS spectrum, it was confirmed to be Exemplified Compound A-6.

  Other compounds can be synthesized in the same manner.

  Although the compound represented by General formula (1) which concerns on this invention can adjust and contain a quantity suitably in order to provide a desired retardation, as an additional amount, with respect to the cellulose ester to be used, It is preferable to contain 1-15 mass%, and it is especially preferable to contain 2-10 mass%. If it is in this range, sufficient retardation can be imparted to the optical film of the present invention.

<Optical film>
Next, the details of the optical film of the present invention will be described.

  In this invention, an optical film is a functional film used for various display apparatuses, such as a liquid crystal display, a plasma display, and an organic electroluminescent display. Specifically, it is a polarizing plate protective film for liquid crystal display apparatuses, retardation film, antireflection Films, brightness enhancement films, hard coat films, antiglare films, antistatic films, optical compensation films such as viewing angle expansion, etc.

  As the resin of the film serving as the base material of the optical film of the present invention, a cellulose ester resin (also simply referred to as a cellulose ester in the present invention) is used, but other resins that can be used in combination include polycarbonate resins, Polystyrene resin, polysulfone resin, polyester resin, polyarylate resin, acrylic resin, olefin resin (norbornene resin, cyclic olefin resin, cyclic conjugated diene resin, vinyl alicyclic hydrocarbon resin, etc.) Etc. Among these, you may use together with at least 1 resin of polycarbonate-type resin, acrylic resin, and cyclic olefin resin. When using resin other than cellulose ester, the content is preferably 5 to 70% by mass.

  The optical film of the present invention is preferably used for a polarizing plate protective film, a retardation film, and an optical compensation film. It is preferable that the retardation film also serves as a polarizing plate protective film.

[Cellulose ester]
Although it does not specifically limit regarding the kind of cellulose ester which concerns on this invention, It is preferable that it is a C2-C22 linear or branched carboxylic acid ester, These carboxylic acid may form a ring, and carbon It may be an ester of an aromatic carboxylic acid of formula 7-11. 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.

  More preferable cellulose ester types include, in addition to cellulose acetate, propionate groups or butyrate groups in addition to acetyl groups such as cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate. A mixed fatty acid ester of cellulose to which is bound.

  Regarding the substitution degree of the acyl group of the cellulose ester according to the present invention, those having a total substitution degree of the acyl group of the cellulose ester of 1.5 or more and 2.6 or less are preferable.

  As the cellulose ester according to the present invention, those satisfying the following formulas (a) and (b) are particularly preferable.

Formula (a) 1.5 ≦ X + Y ≦ 2.6
Formula (b) 0 <X ≦ 2.6
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 acetate propionate (Y; propionyl group, Y> 0) are most preferably used. As cellulose acetate, it is preferable that 2.0 ≦ X ≦ 2.6, and as cellulose acetate propionate, 0 <X ≦ 2.0, 0.5 ≦ Y ≦ 2.0, 1.5 ≦ It is preferable that X + Y ≦ 2.6. In addition, the measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96. In addition, the portion not substituted with an acyl group usually exists as a hydroxyl group.

  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 (Mn) of the cellulose ester according to the present invention is preferably in the range of 30,000 to 200,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 40,000-100,000 is used preferably.

  The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose ester according to the present invention 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.

  Although there is no limitation in particular as a cellulose of the raw material of the cellulose ester which concerns on this invention, Cotton linter, wood pulp, kenaf etc. can be mentioned. 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. It is preferable to add at least one.

[Sugar ester compound]
Examples of sugars that can be used in the optical film of the present invention as a raw material for synthesizing sugar ester compounds include, for example, at least one pyranose structure or at least 12 furanose structures, and an OH group having the structure. The ester compound which esterified all or one part of these is mentioned.

  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 according to 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 can also be mentioned.

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

  For example, sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose and the like are preferable, and sucrose is more preferable.

  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, 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.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 of at least one of the pyranose structural unit or the furanose structural unit 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 addition amount of these sugar ester compounds is preferably 0.5 to 30% by mass based on the cellulose ester resin used. 5 to 20% by mass is particularly 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, 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 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 or 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.

  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 the 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, 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 biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Aromatic monocarboxylic acids having a ring of Of these monocarboxylic acids, acetic acid, propionic acid, and benzoic acid are particularly preferable.

  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—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 or an arylene group having 6 to 12 carbon atoms, A represents an alkylene group having 2 to 10 carbon atoms or an arylene group having 6 to 12 carbon atoms, and m and n are repeating units. Represents.

The compound represented by the general formula (c) includes a benzene monocarboxylic acid represented by BCOOH and an alkylene glycol, oxyalkylene glycol or aryl glycol represented by HO— (GO) _m —H, HOCO-A-COOH. It is synthesized from an alkylene dicarboxylic acid or arylene dicarboxylic acid represented by the formula (1), and can be obtained by the same reaction as a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the aromatic terminal ester plasticizer used in the present invention include, for example, benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethyl There are benzoic acid, normal propyl benzoic acid, 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 having 2 to 12 carbon atoms as the raw material for the aromatic terminal ester 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 (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3 -Dimethylol heptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1 There are 3-pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. These glycols are used as one or a mixture of two or more. 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 plasticizer include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols can be used as one or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms as the raw material for the aromatic terminal ester plasticizer include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, etc. These are each used as one or a mixture of two or more. 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 aromatic terminal ester 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.

  Hereinafter, synthesis examples of aromatic terminal ester plasticizers that can be used in the present invention will be shown.

(Sample No. 1)
A reaction vessel is charged with 410 parts of phthalic acid, 610 parts of benzoic acid, 737 parts of dipropylene glycol, and 0.40 part of tetraisopropyl titanate as a catalyst, and a reflux condenser is attached while stirring in a nitrogen stream. While refluxing excess monohydric alcohol, heating was continued at 130 to 250 ° C. until the acid value became 2 or less, and water produced was continuously removed. Next, the distillate is removed under reduced pressure at 200 to 230 ° C. under a reduced pressure of 1.33 × 10 ⁴ Pa to 4 × 10 ² Pa or less, and then filtered to remove an aromatic terminal ester plastic having the following properties: An agent was obtained.

Viscosity (25 ° C., mPa · s); 43400
Acid value: 0.2
(Sample No. 2)
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 341 parts of ethylene glycol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 31000
Acid value: 0.1
(Sample No. 3)
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,2-propanediol, and 0.35 part of tetraisopropyl titanate as the catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 38000
Acid value: 0.05
(Sample No. 4)
Sample No. 4 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,3-propanediol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 37000
Acid value: 0.05
[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 hydroxyl group in the molecule and an ethylenically unsaturated monomer Xb having no hydroxyl ring in the molecule and having a hydroxyl group are used. A mixture of a polymer X having a weight average molecular weight of 3000 to 30000 obtained by polymerization and a 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.

  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).

General formula (X)-[Xa] _m- [Xb] _n- [Xc] _p-
In the formula, Xa represents — [CH ₂ —C (Rc) (CO ₂ Rd)] —, and Xb represents — [CH ₂ —C (Re) (CO ₂ Rf—OH)] —.

Formula (Y) Ry- [Ya] _k- [Yb] _q-
In the formula, Ya represents — [CH ₂ —C (Rg) (CO ₂ Rh—OH)] —.

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. Yb represents a monomer unit copolymerizable with Ya. m, n, k, p, and q represent a molar composition ratio. However, 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 cellulose-ester resin to be used, and it is especially preferable to contain 5-20 mass%.

[Ultraviolet 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 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, and the like, and Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328 Tinuvins such as Tinuvin 928 and the like are all commercially available from BASF 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.

  The optical film of the present invention 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 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 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. It is preferable to contain.

  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 ester resin used.

[Fine particles]
The optical film of 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 drying 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.

  When the optical film of the present invention is used as a polarizing plate protective film, the content of these fine particles in the polarizing plate protective film is preferably 0.01 to 1% by mass, particularly 0.05 to 0.5% by mass. % Is preferred. 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.). Can do.

  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 (above, manufactured by Toshiba Silicone Co., Ltd.) It is commercially available under the trade 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 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.

<Method for producing optical film>
Next, the manufacturing method of the optical film of this invention is demonstrated.

  The optical film of 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 production of the optical film of the present invention comprises a step of dissolving a cellulose ester and an additive in a solvent to prepare a dope, a step of casting the dope onto an endless metal support that moves indefinitely, a web of the cast dope As a step of drying, 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. The concentration for achieving both of these is preferably 10 to 35 mass%, more preferably 15 to 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, the cellulose acetate ester (acetyl group substitution degree 2.2 to 2.4). ), Cellulose acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree: 2.7 to 2.9) 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 recovered 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 mamacos. Further, a method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  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 further 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 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 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 / cm < 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 even 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 drying step of the optical film, the web is peeled off from the metal support, and further dried, so that the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less. Preferably it is 0-0.01 mass% or less.

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

Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that 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.

  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 of the present invention, it is particularly preferable to stretch in the width direction (lateral direction) by a tenter method in which both ends of the web are gripped by 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 15-60 micrometers. If it is this range, since the improvement of the moisture permeability depending on the film thickness of a film and the expression of the retardation by the retardation developing agent concerning this invention can be compatible, it is preferable.

  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 process 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 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 to 200 ° C, more preferably 140 to 180 ° C.

  The residual solvent in the film during stretching is preferably 0 to 20% by mass, more preferably 0 to 15% by mass.

  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.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and 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 this anisotropy and 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 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 sheets type) and a mode in which only one of the upper and lower sides of the cell is used (one sheet) Type).

  The optical film of the present invention has a retardation Ro of 23 ° C. and 55% RH represented by the following formula, a wavelength of 20 to 100 nm at 590 nm, an Rth of 23 ° C. and 55% RH, and a wavelength. Is preferably 70 to 300 nm at 590 nm.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
In the formula, nx represents the refractive index in the direction x where 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).

  The slow axis or the fast axis of the optical film of the present invention is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less, assuming that the angle formed with the film forming direction is θ1. More preferably, it is 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 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 this invention can be used for the polarizing plate of this invention, and the liquid crystal display device of this invention 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 prepare an optical film having a phase difference separately from the polarizing plate protective film. Therefore, the manufacturing process can be simplified.

  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 of the present invention can be produced by a general method. The optical film of the present invention is preferably bonded to at least one surface of a polarizer prepared by subjecting the polarizer side of the optical film 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 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]
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 in 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 the case of a large-screen liquid crystal display device having a screen size of 30 or more, it is possible to obtain a liquid crystal display device having excellent visibility such as front contrast by reducing coloring during black display due to light leakage.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<< Production of optical film >>
(Preparation of optical 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 Next, a main dope liquid 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. While this was heated and stirred, it was completely dissolved, and 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 having an acetyl substitution degree of 2.90; described as TAC in Table 1) 100 parts by mass Retardation developer: Exemplified compound A-1 3 parts by mass Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.) 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, an endless belt casting apparatus was used to uniformly cast the dope solution on a stainless steel belt support at a temperature of 35 ° 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 amount of residual solvent in the cast (cast) film was 75% by mass, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m.

  The peeled optical 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% by mass.

  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.

(Production of optical films 102 to 124)
Optical films 102 to 124 were prepared in the same manner as in the production of the optical film 101 except that the type of cellulose ester, the additive in place of the exemplary compound A-1 and the film thickness of the optical film were changed as shown in Table 1. The film thickness of the optical film was adjusted by changing the flow rate of the dope solution. In addition, the addition amount of the cellulose ester replaced with the used cellulose ester A was the same mass part as the cellulose ester A.

  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 CAP1 in Table 1)
Cellulose ester C: Cellulose diacetate having an acetyl substitution degree of 2.41 (described as DAC in Table 1)
Cellulose ester D: cellulose acetate propionate having an acetyl substitution degree of 0.12, a propionyl substitution degree of 1.53, and a total acyl group substitution degree of 1.65 (denoted as CAP2 in Table 1)
Cellulose ester E: 30 parts by mass of cellulose acetate propionate having an acetyl substitution degree of 0.2, a propionyl substitution degree of 2.55, and a total acyl group substitution degree of 2.75 and a dialnal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) 70 masses Resin (described as CAP3 in Table 1) The structure of the comparative compound is as follows.

<< Evaluation of optical film >>
About the produced optical film sample, evaluation described below was performed.

(Film thickness)
The thickness of the film was measured using a commercially available micrometer.

(Retardation value)
The average refractive index of the film constituting material was measured using an Abbe refractometer (4T).

  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.)
(Bleed-out resistance)
The optical film was allowed to stand for 1000 hours in a high-temperature and high-humidity atmosphere at 80 ° C. and 90% RH, and then the presence or absence of bleed-out (crystal precipitation) on the surface of the optical film was visually observed and evaluated according to the following criteria.

A: No bleed-out is observed on the surface B: Partial bleed-out is slightly observed on the surface C: Slight bleed-out is observed on the entire surface D: Clear on the entire surface Bleed-out is recognized Here, A and B are at a level where there is no practical problem.

  The evaluation results are shown in Table 1.

  As is clear from Table 1, the optical films 101 to 119 of the present invention are practically excellent optical films having excellent retardation and excellent bleed-out resistance as compared with the comparative optical films 120 to 123. I understand that. In addition, the optical film 124 which does not contain a retardation developer has a small retardation value and has no function as an optical compensation film.

Example 2
<Production of polarizing plate>
(Preparation of polarizing plate 101)
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 film 101 produced in Example 1 were bonded according to the following steps 1 to 5, and Konica Minolta Tack KC4UY (Konica Minolta Opto's cellulose ester film) was bonded to the back side. A polarizing plate was produced.

  Step 1: The optical film 101 was immersed 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 placed on the cellulose ester film treated in Step 1.

Step 4: The optical film 101 laminated in Step 3 and the polarizer-side surface of the polarizer were overlaid with the Konica Minoltack KC4UY and bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Step 5: A sample in which the polarizer prepared in Step 4 was bonded to the optical film 101 and Konica Minoltack KC4UY in a drier at 80 ° C. was dried for 2 minutes to prepare polarizing plates 101 to 123.

(Production of polarizing plates 102 to 123)
In the production of the polarizing plate 101, the polarizing plates 102 to 123 were produced in the same manner except that the optical film 101 was changed to the optical films 102 to 123.

<Production of polarizing plate>
About the produced polarizing plate, durability of the polarizing plate was evaluated as follows.

(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 Light resistance was evaluated based on the following criteria for the amount of change in polarization degree obtained as described above.

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 is at a level where there is no practical problem.

(Heat resistant)
Two of the 500 mm × 500 mm polarizing plate samples obtained above are heat-treated (conditions: left at 80 ° C. and 90% RH for 100 hours), and when placed in an orthogonal state, whichever is the larger of the vertical or horizontal center line portions The length of the white-out portion of the edge was measured, the ratio to the side length (500 mm) was calculated, and the following criteria were evaluated 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)
A and B are levels at which there is no practical problem.

  The evaluation results are shown in Table 2.

  As is clear from Table 2, it can be seen that the polarizing plates 101 to 119 of the present invention are practically excellent polarizing plates having good light resistance and heat and humidity resistance as compared with the comparative polarizing plates 120 to 123.

Example 3
<Production of liquid crystal display device>
(Production of liquid crystal display device 101)
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 by SONY were peeled off in advance, and the prepared polarizing plates 101 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 absorption axis of the polarizing plate bonded in advance and the absorption axis of the polarizing plate 101. The liquid crystal display device 101 was manufactured in such a manner that the absorption axis was directed in the same direction.

(Production of liquid crystal display devices 102 to 123)
In the production of the liquid crystal display device 101, the liquid crystal display devices 102 to 123 were produced in the same manner except that the polarizing plate 101 was changed to the polarizing plates 102 to 123.

<Evaluation of liquid crystal display device>
The manufactured liquid crystal display device was evaluated as follows.

(Front contrast unevenness)
Measurement was performed after the backlight of the 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 five points of the liquid crystal display device and evaluate according to the following criteria did.

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, Unevenness is large A and B are at a level where there is no practical problem.

(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 made 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 A and B are at a level that causes no problem in practice.

  Table 3 shows the evaluation results.

  As can be seen from Table 3, the liquid crystal display devices 101 to 119 of the present invention have no front contrast unevenness compared to the comparative liquid crystal display devices 120 to 123. It can be seen that the liquid crystal display device is stable and has excellent durability.

Claims (5)

In the optical film containing a cellulose ester, the following general formula (1) :
(In the formula, R ₁ and R ₂ represent a hydrogen atom or a substituent. R ₃ and R ₄ represent a hydrogen atom or a substituent having a negative Hammett's σp value. L ₁ and L ₂ are divalent. A represents a linking group, A represents a 1-9 valent aromatic group or a 1-9 valent heteroaromatic group, m represents 0 or 1, n represents an integer of 0 to 8, r and s represent Represents an integer of 1 to 4)
Containing a compound represented by
Following formula:
Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x where the refractive index is maximum in the in-plane direction of the optical film, 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.)
Retardation Ro is 20-100 nm and Rth is 70-300 nm at a measurement wavelength of 590 nm.   The optical film according to claim 1, wherein n in the general formula (1) is 0.   The optical film according to claim 1, wherein the optical film has a thickness of 15 to 60 μm. A polarizing plate comprising the optical film according to any one of claims 1 to 3 on at least one surface of a polarizer. A liquid crystal display device comprising the polarizing plate according to claim 4 on at least one surface of a liquid crystal cell.