JP2012072223A - Optical film, and polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film that has high retardation development, less effect due to humidity variation, less bleed out even in hot and humid conditions, and superior attachability to a polarizer, and further to provide a polarizing plate and a liquid crystal display device having good durability using the optical film.SOLUTION: The optical film contains: polyester polyol (A) obtained by the reaction of a dibasic acid having alicyclic structure or an ester-forming derivative thereof with glycol; and a cellulose ester, and a hydroxyl group content of the polyester polyol (A) is more than 50%.

Description

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

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

  In recent years, development of thin and light notebook PCs and thin and large-screen TVs has progressed, and along with this, the demand for thinner, larger, and higher performance optical compensation films for liquid crystal display devices has become stronger. .

  However, since the cellulose ester film does not have sufficient birefringence essential for the optical compensation film, various additives have been studied for the purpose of imparting birefringence to the cellulose ester film.

  On the other hand, with the exception of birefringence, the humidity stability of optical performance has been demanded more severely due to the demand for larger size and higher functionality, and the conventional cellulose ester film has high hygroscopicity, so this humidity stability is It was a bad problem.

  As means for solving these problems, a method using a polyester having excellent light stability as an additive has been proposed.

  For example, in Patent Document 1, there is a method for improving humidity stability and developing retardation by adding two kinds of a diester compound whose end is an aromatic ester group and a polyester oligomer whose end is an aromatic ester group. Proposed. However, the optical compensation film prepared by this method has insufficient retardation, and has low compatibility between the polyester having a terminal aromatic ester and the cellulose ester, so that it tends to bleed out in a film state. There was a problem.

  Patent Document 2 discloses an aliphatic polyester polyol for the purpose of improving bleeding out. However, polyester polyols that do not have a cyclic structure are not intended to improve the retardation expression, so the bleeding out when added to the cellulose ester is improved, but the retardation expression is low. It had the problem that.

  On the other hand, Patent Document 3 and Patent Document 4 disclose a polyester resin having a decahydronaphthalene ring as a polyester having an alicyclic structure, but it is intended to obtain a film having a large retardation as in the present invention. It was n’t. Moreover, the adhesiveness with the polyvinyl alcohol which is a polarizer is inadequate, and there is no description in the specification about the optical film which consists of a cellulose ester and polyester.

  In patent document 5, the retardation film excellent in the optical characteristic is proposed by using the polyester which used the dicarboxylic acid with a high trans ratio as a raw material. However, the bonding property with polyvinyl alcohol as a polarizer is insufficient, and there is no description in the specification about the optical film composed of cellulose ester and polyester.

JP 2008-69225 A JP 2009-98674 A JP 2001-261803 A JP 2001-261799 A JP 2009-109996 A

  The present invention has been made in view of the above problems.Therefore, the object of the present invention has high retardation expression, is less affected by humidity fluctuations, has less bleed out even under high temperature and high humidity, It is providing the optical film excellent in the pasting property with a polarizer. 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. The polyester polyol (A) contains a polyester polyol (A) and a cellulose ester obtained by reacting a dibasic acid having an alicyclic structure or an ester-forming derivative thereof with glycol, and the polyester polyol (A) has a hydroxyl group content. An optical film characterized by being larger than 50%.

  2. 2. The optical film as described in 1 above, wherein the polyester polyol (A) has a number average molecular weight of 300 to 3,000.

  3. 3. The optical film as described in 1 or 2 above, wherein the dibasic acid having an alicyclic structure has 9 to 14 carbon atoms.

  4). 4. The optical film as described in any one of 1 to 3 above, wherein the polyester polyol (A) has a hydroxyl group content of 70% to 100%.

  5. 5. The optical film as described in any one of 1 to 4, wherein the polyester polyol (A) has a hydroxyl value of 35 mg / g to 220 mg / g.

  6). The retardation Ro represented by the following formula (I) is 20 to 100 nm, and the retardation Rth represented by the following formula (II) is 70 to 300 nm. The optical film as described.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x in which the refractive index is maximum in the in-plane direction of the optical film, and ny represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the optical film. , Nz represents the refractive index in the thickness direction z of the optical film, and d (nm) represents the thickness of the optical film.)
7). A polarizing plate comprising the optical film according to any one of 1 to 6 on at least one surface of a polarizer.

  8). 8. A liquid crystal display device comprising the polarizing plate according to 7 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 development property, little influence by humidity fluctuation, little bleed-out even under high temperature and high humidity, and excellent adhesion to a polarizer. It was. Furthermore, it was possible to provide a polarizing plate and a liquid crystal display device having good durability 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.

  In order to solve the above-mentioned problems, the present inventors diligently studied about an optical film containing polyester. As a result, the detailed reason has not been elucidated, but a dibasic acid having an alicyclic structure or an ester-forming derivative thereof. By containing polyester polyol (A) obtained by reacting glycol and cellulose ester, it has high retardation expression, is less affected by fluctuations in humidity, and is bonded to polyvinyl alcohol as a polarizer. It was found that an optical film excellent in the above can be obtained. Furthermore, the polyester polyester polyol (A) has a number average molecular weight of 300 to 3000 and a hydroxyl value of 35 mg / g to 220 mg / g, so that the bleed out from the film is greatly improved in addition to the above effects. I found out that I can. It was also found that a polarizing plate and a liquid crystal device having good durability can be obtained by using the obtained optical film.

  Hereinafter, the present invention will be described in detail.

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

[Polyester polyol (A)]
The polyester polyol (A) used in the present invention is a polymer obtained by a reaction between a dibasic acid or an ester-forming derivative thereof and glycol and having a terminal hydroxyl group. The ester-forming derivative referred to here is an esterified product of the dibasic acid, dibasic acid chloride, or dibasic acid anhydride.

  The polyester polyol (A) includes a dehydration condensation reaction between a dibasic acid having an alicyclic structure and a glycol, an addition of a glycol to an anhydrous dibasic acid having an alicyclic structure and a dehydration condensation reaction, or a divalent alicyclic structure. It can preferably be obtained by a condensation reaction by dealcoholization of a basic acid esterified product and glycol.

  Examples of the dibasic acid having an alicyclic structure or an ester-forming derivative thereof include, for example, a dicarboxylic acid having an alicyclic structure such as a cyclohexane ring structure, a norbornane ring structure, a decahydronaphthalene ring structure, a dicyclohexane ring structure, or the like. Ester-forming derivatives can be used. Specific examples include, for example, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 3,3′-dicyclohexanedicarboxylic acid, 3,4′-dicyclohexanedicarboxylic acid, 4,4′-dicyclohexanedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, 2,3-decahydronaphthalenedicarboxylic acid, 2,2-bis (3-carboxycyclohexyl) propane, 2,2-bis (4 -Carboxycyclohexyl) propane, bis (3-carboxycyclohexyl) ether, bis (4-carboxycyclohexyl) ether, bis (3-carboxycyclohexyl) sulfide, bis (4-carboxycyclohexyl) sulfide, bis (3-carboxycyclohexyl) Tan, bis (4-carboxycyclohexyl) methane, 2,5-norbornanedicarboxylic acid, 2,6-norbornanedicarboxylic acid, 1,4-norbornanedicarboxylic acid, 2,3-norbornanedicarboxylic acid, etc., and their esterified products, and Examples thereof include acid chlorides, 1,2-cyclohexanedicarboxylic acid, 2,3-decahydronaphthalenedicarboxylic acid, 2,3-norbornanedicarboxylic acid anhydride, and the like. These may have a substituent, and these may be used alone or in combination of two or more.

  In the present invention, the dibasic acid having an alicyclic structure preferably has 9 to 14 carbon atoms. If the carbon number of the dibasic acid is 9 or more, the retardation is excellent in expression, and if the carbon number is 14 or less, bleeding out from the film can be suppressed. Preferred dibasic acids include, for example, 3,3′-dicyclohexanedicarboxylic acid, 3,4′-dicyclohexanedicarboxylic acid, 4,4′-dicyclohexanedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, 2, 3-norbornanedicarboxylic acid and esterified products thereof can be mentioned, and more preferably 4,4′-dicyclohexanedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, 2,3-norbornanedicarboxylic acid and these Particularly preferred are 4,4′-dicyclohexanedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid and esterified products thereof.

  Examples of the glycol include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methyl 1,3-propanediol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,4-cyclohexanediol Can be used alone or in combination of two or more, among which ethylene glycol, diethylene glycol, 1,2-propylene glycol, 2-methyl 1,3-propanediol are preferred, more preferably ethylene glycol, diethylene glycol, 1,2- Russia is propylene glycol.

  The polyester polyol (A) of the present invention comprises the dibasic acid or an ester-forming derivative thereof and a glycol, if necessary, in the presence of an esterification catalyst, for example, within a temperature range of 180 to 250 ° C. It can be produced by an esterification reaction in a well-known and conventional manner for a time.

  In conducting the esterification reaction, a solvent such as toluene or xylene may be used, but a method using no solvent or glycol used as a raw material as a solvent is preferable.

  As the esterification catalyst, for example, tetraisopropyl titanate, tetrabutyl titanate, p-toluenesulfonic acid, dibutyltin oxide and the like can be used. The esterification catalyst is preferably used in an amount of 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the total amount of dibasic acids or their ester-forming derivatives.

  The molar ratio when the dibasic acid or their ester-forming derivative is reacted with the glycol must be a molar ratio in which the terminal group of the polyester becomes a hydroxyl group, and therefore, 1 mol of the dibasic acid or their ester-forming derivative. The glycol is preferably 1.1 to 10 moles. More preferably, the glycol is 1.5 to 7 moles with respect to 1 mole of the dibasic acid or their ester-forming derivative, and even more preferably with respect to 1 mole of the dibasic acid or their ester-forming derivative. , Glycol is 2-5 moles.

  On the other hand, since the carboxyl group terminal in the said polyester polyol (A) reduces humidity stability, the one where the content is low is preferable. Specifically, the acid value is preferably 5.0 mgKOH / g or less, more preferably 0 to 1.0 mgKOH / g, and particularly preferably 0 to 0.5 to 0 mgKOH / g.

  The acid value as used herein refers to the number of milligrams of potassium hydroxide necessary to neutralize the acid (carboxyl group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070.

  The polyester polyol (A) preferably has a hydroxyl value (OHV) in the range of 35 mg / g to 220 mg / g. The hydroxyl value as used herein refers to the number of milligrams of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when OH groups contained in 1 g of a sample are acetylated. Acetic anhydride is used to acetylate OH groups in the sample, and unused acetic acid is titrated with a potassium hydroxide solution, and obtained from the difference from the initial titration value of acetic anhydride.

  In the present invention, the polyester polyol (A) refers to a compound having a hydroxyl group content greater than 50%. The hydroxyl group content of the polyester polyol (A) is preferably 70% or more. When the hydroxyl group content is high, the compatibility between the polyester polyol (A) and the cellulose ester is increased. For this reason, the hydroxyl group content is preferably 70% or more, more preferably 90% or more, and most preferably 99% or more.

The hydroxyl group content can be determined by the following formula (A).
Formula (A)
X / Y × 100 = hydroxyl group content (%)
X: Hydroxyl value (OHV) of the polyester polyol (A)
Y: 1 / (number average molecular weight (Mn)) × 56 × 2 × 1000
The polyester polyol (A) preferably has a number average molecular weight within a range of 300 to 3000, and more preferably has a number average molecular weight of 350 to 2000.

  The hydroxyl group content of the polyester polyol (A) can be adjusted by changing the ratio of the dibasic acid or ester-forming derivative thereof to glycol and the like to cause an esterification reaction.

  Further, the degree of dispersion (Mw / Mn) of the molecular weight of the polyester polyol (A) of the present invention is preferably from 1.0 to 3.0, and more preferably from 1.0 to 2.0. When the dispersity (Mw / Mn) is within the above range, a polyester polyol (A) excellent in compatibility with the cellulose ester can be obtained.

  As a method for controlling the number average molecular weight, the degree of dispersion, and the component content within the above preferred range, 2 to 5 mol of glycol is used per 1 mol of dibasic acid or ester-forming derivative thereof, and unreacted glycol is used. A method of distilling off under reduced pressure is preferred. The temperature at which the solvent is distilled off under reduced pressure is preferably 100 to 200 ° C, more preferably 120 to 180 ° C, and particularly preferably 130 to 170 ° C. The degree of reduced pressure when the solvent is distilled off under reduced pressure is preferably 0.1 to 500 Torr, more preferably 0.5 to 200 Torr, and most preferably 1 to 100 Torr.

  The number average molecular weight (Mn) and dispersity (Mw / Mn) of the polyester polyol (A) 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: Tetrahydrofuran (THF)
Column: TSKgel G2000HXL (Tosoh Co., Ltd. uses two connected)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Flow rate: 1.0ml / min
Calibration curve: A calibration curve by PStQuick F (manufactured by Tosoh Corporation) is used.

  In obtaining the effects of the present invention, the polyester polyol (A) is preferably contained in the film in an amount of 5 to 30% by mass. More preferably, it is 5-20 mass%.

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

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

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

  Preferable cellulose esters used in the present invention are those satisfying the following formulas (a) and (b) at the same time.

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

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

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

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

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

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

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

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

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

(acrylic resin)
An acrylic resin can be used in combination with the cellulose ester resin. The acrylic resin that can be used in combination is not particularly limited, but is preferably composed of 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like can be mentioned, and these can be used alone or in combination of two or more monomers.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  The acrylic resin used for the optical film has a weight average molecular weight (Mw) of 110,000 or more and 1000000 or less, particularly from the viewpoint of improving brittleness as an optical film and improving transparency when compatible with a cellulose ester resin. Is preferred.

  If the weight average molecular weight (Mw) of the acrylic resin is 110,000 or more, sufficient brittleness improvement is obtained, and compatibility with the cellulose ester resin is excellent.

  The weight average molecular weight (Mw) of the acrylic resin is more preferably in the range of 110000 to 600000, and particularly preferably in the range of 110000 to 400000.

  The weight average molecular weight of the acrylic resin can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
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 Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  There is no restriction | limiting in particular as a manufacturing method of the said acrylic resin, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used.

  Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  A commercially available thing can also be used as said acrylic resin. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Denki Kagaku Kogyo Co., Ltd.) and the like can be mentioned. . Two or more acrylic resins can be used in combination.

  When a cellulose ester resin and an acrylic resin are used in combination, the acrylic resin can be mixed within a range where there is no problem in brittleness and compatibility, but preferably 1 to 99% by mass, more preferably based on the cellulose ester resin. Is 10 to 90% by mass, most preferably 30 to 70% by mass.

  In addition to the polyester polyol (A), at least one of a sugar ester compound, a plasticizer, an ultraviolet absorber, an antioxidant, and fine particles described below may be added to the optical film.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Monopet SB: manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Monopet SOA: manufactured by Daiichi Kogyo Seiyaku Co., Ltd. The amount of these sugar ester compounds added is preferably 0.5 to 30% by mass based on the resin used. In particular, it is preferable to contain 5-20 mass%.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the 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 still more preferable.

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

  The antioxidant has a role of delaying or preventing the optical film from being decomposed by, for example, the residual solvent amount of halogen in the optical film or phosphoric acid of the phosphoric acid plasticizer. 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 to the resin used.

(Fine particles)
The optical film preferably contains fine particles.

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

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

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

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

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

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

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

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

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

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

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

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

(Production method)
Next, a method for producing the optical film will be described.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  Here, the dope casting will be described.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

(Optical compensation film)
Since liquid crystal displays use anisotropic liquid crystal materials and polarizing plates, there is a viewing angle problem that even if a good display is obtained when viewed from the front, the display performance is degraded when viewed from an oblique direction. In order to improve performance, a viewing angle compensator is necessary. The average refractive index distribution is larger in the cell thickness direction and smaller in the in-plane direction. Therefore, a compensation plate that can cancel 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 film can also be used as an optical compensation film having such a function.

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

  The optical film has a retardation Ro of 23 ° C. and 55% RH represented by the following formula, a wavelength of 590 nm and a wavelength of 20 to 100 nm, an Rth of 23 ° C. and 55% RH, and a wavelength of 590 nm. It is preferable that it is 70-300 nm.

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

  The refractive index nx of the optical film is the maximum refractive index in the plane of the film, also referred to as the refractive index in the slow axis direction, and ny is the refractive index in the direction perpendicular to the slow axis in the film plane. Also called refractive index. When the slow axis or the fast axis exists in the film plane and the angle formed by the fast axis and the film forming direction is θ1, θ1 is preferably −1 ° or more and + 1 ° or less, and −0.5 ° More preferably, it is + 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 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 preferably has a breaking elongation of 10 to 80%.

  The optical film has a visible light transmittance of preferably 90% or more, and more preferably 93% or more.

  The haze of the optical film 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, or by further stretching it.

〔Polarizer〕
The optical film can be used for a polarizing plate having a polarizing plate protective film and the liquid crystal display device using the polarizing plate. The optical film 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. Thinning the manufacturing process can be simplified.

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

  The polarizing plate can be produced by a general method. The side of the optical film to be bonded to the polarizer is subjected to alkali saponification treatment, and bonded to at least one surface of the polarizer (prepared by immersing and stretching in an iodine solution) using a completely saponified polyvinyl alcohol aqueous solution. Is preferred. Another polarizing plate protective film can be bonded to the other surface. When the optical film 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 optical film (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-X -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 a polarizing plate using the optical film for a liquid crystal display device, the liquid crystal display device having various visibility can be manufactured.

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

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

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

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

<Synthesis Example 1>
In a nitrogen atmosphere, 20.0 g of dimethyl 2,6-decahydronaphthalenedicarboxylate, 17.9 g of 1,2-propylene glycol, and 20 mg of tetraisopropyl titanate are mixed, and stirred at 165 ° C. for 1 hour while distilling off the produced methanol. Went. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 18 hours. Next, the temperature was lowered to 170 ° C., and unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain (PE-1) of polyester polyol (A).

Number average molecular weight: 700
Dispersity: 1.4
Hydroxyl value: 160
Hydroxyl content: 100%
<Synthesis Example 2>
Under a nitrogen atmosphere, 20.0 g of dimethyl 2,6-decahydronaphthalenedicarboxylate, 14.6 g of ethylene glycol, and 20 mg of tetraisopropyl titanate were mixed, and stirred at 165 ° C. for 1 hour while distilling off the produced methanol. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 18 hours. Next, the temperature was lowered to 170 ° C., and unreacted ethylene glycol was distilled off under reduced pressure to obtain (PE-2) of polyester polyol (A).

Number average molecular weight: 650
Dispersity: 1.3
Hydroxyl value: 172
Hydroxyl content: 100%
<Synthesis Example 3>
In a nitrogen atmosphere, 15.7 g of dimethyl 1,4-cyclohexanedicarboxylate, 17.9 g of 1,2-propylene glycol and 20 mg of tetraisopropyl titanate were mixed, and stirred at 165 ° C. for 1 hour while distilling off the produced methanol. It was. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 18 hours. Next, the temperature was lowered to 170 ° C., and unreacted propylene glycol was distilled off under reduced pressure to obtain (PE-3) of polyester polyol (A).

Number average molecular weight: 1200
Dispersity: 1.5
Hydroxyl value: 91
Hydroxyl content: 98%
<Synthesis Example 4>
In a nitrogen atmosphere, 15.7 g of dimethyl 1,4-cyclohexanedicarboxylate, 13.4 g of 1,2-propylene glycol, and 20 mg of tetraisopropyl titanate were mixed, and stirred at 165 ° C. for 1 hour while distilling off the generated methanol. It was. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 18 hours. Next, the temperature was lowered to 170 ° C., and unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain (PE-4) of polyester polyol (A).

Number average molecular weight: 3100
Dispersity: 1.6
Hydroxyl value: 35
Hydroxyl content: 100%
<Synthesis Example 5>
In a nitrogen atmosphere, 22.2 g of dimethyl 4,4′-dicyclohexanedicarboxylate, 17.9 g of 1,2-propylene glycol and 20 mg of tetraisopropyl titanate were mixed, and stirred at 165 ° C. for 1 hour while distilling off the produced methanol. Went. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 18 hours. Next, the temperature was lowered to 170 ° C. and 1,2-propylene glycol as an unreacted substance was distilled off under reduced pressure to obtain (PE-5) of polyester polyol (A).

Number average molecular weight: 800
Dispersity: 1.5
Hydroxyl value: 140
Hydroxyl content: 100%
<Synthesis Example 6>
In a nitrogen atmosphere, 16.7 g of dimethyl 2,3-norbornanedicarboxylate, 16.0 g of 1,2-propylene glycol and 20 mg of tetraisopropyl titanate were mixed, and the mixture was stirred at 165 ° C. for 1 hour while distilling off the produced methanol. It was. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 18 hours. Next, the temperature was lowered to 170 ° C., and unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain (PE-6) of polyester polyol (A).

Number average molecular weight: 720
Dispersity: 1.4
Hydroxyl value: 147
Hydroxyl content: 95%
<Synthesis Example 7>
In a nitrogen atmosphere, 15.7 g of dimethyl 1,4-cyclohexanedicarboxylate, 17.0 g of 1,4-cyclohexanedimethanol and 20 mg of tetraisopropyl titanate were mixed, and the mixture was stirred at 165 ° C. for 1 hour while distilling off the produced methanol. went. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 18 hours. Next, the temperature was lowered to 170 ° C., and the mixture was stirred for 3 hours under reduced pressure to obtain (PE-7) of polyester polyol (A).

Number average molecular weight: 770
Dispersity: 1.6
Hydroxyl value: 147
Hydroxyl content: 89%
<Synthesis Example 8>
In a nitrogen atmosphere, 15.7 g of dimethyl 1,4-cyclohexanedicarboxylate, 12.4 g of 1,2-propylene glycol, and 20 mg of tetraisopropyl titanate were mixed, and stirred at 165 ° C. for 1 hour while distilling off the produced methanol. It was. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 8 hours. Next, the temperature was lowered to 165 ° C., and 1,2-propylene glycol as an unreacted substance was distilled off under reduced pressure to obtain (PE-8) of polyester polyol (A).

Number average molecular weight: 800
Dispersity: 1.5
Hydroxyl value: 84
Hydroxyl content: 60%
<Comparative Synthesis Example 1>
In a nitrogen atmosphere, 4.85 g of dimethyl terephthalate, 4.4 g of 1,2-propylene glycol, 6.8 g of p-toluic acid, and 10 mg of tetraisopropyl titanate were mixed and stirred at 140 ° C. for 2 hours. Stirring was carried out at ° C for 16 hours. Next, the temperature was lowered to 170 ° C., and unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain a comparative polyester (A-1).

Number average molecular weight: 490
Dispersity: 1.4
Hydroxyl value: 0.1
Hydroxyl content: 0.04%
<Comparative Synthesis Example 2>
Under a nitrogen atmosphere, 12.0 g of dimethyl succinate, 17.9 g of 1,2-propylene glycol and 20 mg of tetraisopropyl titanate were mixed, and stirred at 165 ° C. for 1 hour while distilling off the produced methanol. The mixture was further stirred at 185 ° C. for 1 hour, then heated to 195 ° C. and stirred for 18 hours. Next, the temperature was lowered to 170 ° C., and unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain a comparative polyester polyol (A-2).

Number average molecular weight: 700
Dispersity: 1.4
Hydroxyl value: 160
Hydroxyl content: 100%
<Comparative Synthesis Example 3>
Under a nitrogen atmosphere, 20.0 g of dimethyl 2,6-decahydronaphthalenedicarboxylate, 6.0 g of 1,2-propylene glycol and 20 mg of tetraisopropyl titanate were mixed and stirred at 175 ° C. for 1 hour. After further stirring at 195 ° C. for 4 hours, the temperature was then lowered to 170 ° C., and unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain comparative polyester (A-3).

Number average molecular weight: 720
Dispersity: 1.4
Hydroxyl value: 70
Hydroxyl content: 45%
<Comparative Synthesis Example 4>
Under a nitrogen atmosphere, 28.0 g of the trans isomer of dimethyl 2,6-decahydronaphthalenedicarboxylate and 15.0 g of ethylene glycol were mixed, and 0.03 mol% of manganese acetate tetrahydrate, 0.03 mol of triethylamine were added to the acid component. 01 mol% was added and it stirred at 200 degreeC for 1 hour. The mixture was further heated to 220 ° C. and stirred for 1 hour while distilling off the methanol produced. After adding 0.05 mol% of germanium oxide and 0.01 mol% of triphenyl phosphite to the acid component, the temperature was raised to 280 ° C. and stirred for 5 hours while distilling off ethylene glycol under reduced pressure. (A-4) was obtained.

Number average molecular weight: 79,000
Dispersity: 2.5
Hydroxyl value: 1.3
Hydroxyl content: 87%
Example 1
<Preparation of optical film 101>
<Fine particle dispersion 1>
Aerosil R972V (silica fine particles; primary particle size 16 nm; manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

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

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

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester A (cellulose triacetate having an acetyl substitution degree of 2.90; described as TAC in Table 1) 100 parts by mass PE-1 (polyester) 5 parts by mass Monopet SB (sucrose benzoate; sugar Ester compound (Daiichi Kogyo Seiyaku Co., Ltd.)
5 parts by mass Particulate additive solution 1 1 part by mass The above was put into a closed container and dissolved while stirring to prepare a dope solution. Next, using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

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

  The peeled optical film was stretched 20% in the width direction using a tenter while applying heat at 140 ° C. The residual solvent at the start of stretching was 15%.

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

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

<Preparation of optical films 102-124>
In the production of the optical film 101, optical films 102 to 124 were produced in the same manner except that the type of cellulose ester or the polyester in place of PE-1 was changed as shown in Table 1. In addition, the addition amount of cellulose ester B, C, D, and E which replaces the used cellulose ester A (TAC) was the same mass part as cellulose ester A (TAC).

  The materials used 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 (described as CAP in Table 1)
Cellulose ester C: cellulose diacetate having an acetyl substitution degree of 2.40 (described as DAC in Table 1)
Cellulose ester D: 50 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 Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) as an acrylic resin ) 50 parts by weight (described as CAP2 in Table 1).

Cellulose ester E: 70 parts by mass of cellulose ester B, copolymer of methyl methacrylate (hereinafter referred to as MMA) and hydroxyethyl methacrylate (hereinafter referred to as HEMA) (copolymerization ratio of MMA and HEMA is 8 to 2, weight) Average molecular weight 5000) 30 parts by mass (described as CAP3 in Table 1)
<Evaluation of optical film>
Each optical film sample produced as described above was evaluated as described below.

(Retardation value)
The retardation value of the center part of the width direction of the obtained optical film sample was measured. For measurement, an automatic birefringence meter KOBURA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) was used to measure three-dimensional birefringence at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. Was substituted into the above-described formulas (I) and (II) to determine Ro and Rth, respectively.

(Retardation value fluctuation)
Retardation Rth values in the thickness direction of the produced optical films were respectively determined, and retardation value variation Rt (a) was determined from the values.

After adjusting the humidity at 23 ° C. and 20% RH for 5 hours, measure the Rth value measured in the same environment as Rt (b) and continue the same film at 23 ° C. and 80% RH for 5 hours. After that, the Rth value measured in the same environment was determined and this was set as Rt (c), and Rt (a) was determined from the following equation.
Rt (a) = | Rt (b) −Rt (c) |
Furthermore, the humidity-controlled sample was measured again in an environment of 23 ° C. and 55% RH, and it was confirmed that this change was a reversible change. A smaller value indicates better humidity fluctuation.

  Table 1 shows the retardation value Ro in the in-plane direction, the retardation value Rth in the thickness direction, and the retardation value fluctuation Rt (a) obtained as described above.

(Haze)
One optical film sample was measured according to ASTM-D1003-52 using T-2600DA manufactured by Tokyo Denshoku Industries Co., Ltd.

(Bleed out)
The produced optical film was allowed to stand in a high temperature and high humidity atmosphere of 80 ° C. and 90% RH for 100 hours, and then bleed out was evaluated.
The presence or absence of bleed out was evaluated by observing the surface of the film.
◎: No bleed-out on the film surface ○: Partial bleed-out on the film surface is faint △: Full bleed-out on the film surface is faint x: Clear bleed-out on the film surface is clear Understandable Table 1 shows the retardation value, retardation value fluctuation, haze and bleedout test results obtained as described above.

  As is clear from Table 1, the optical films 101 to 116 of the present invention are superior in retardation development, have no haze and bleed out, and have a retardation value with respect to humidity change, as compared with the comparative optical films 117 to 124. It turns out that it is an optical film excellent in practical use with little fluctuation.

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

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

  Subsequently, the front side of the polarizer and the optical films 101 to 124 are pasted according to the following steps 1 to 5, and Konica Minolta Tack KC4UY (Konica Minolta Opto Optical Film) is pasted as a polarizing plate protective film on the back side. In addition, a polarizing plate was produced.

  Step 1: The optical films 101 to 124 were immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain an optical film having a saponified side to be bonded to a 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 gently wiped off, and this was placed on the optical film treated in Step 1.

Step 4: The optical films 101 to 124 laminated in Step 3 and the Konica Minoltack KC4UY optical film are stacked on the polarizer side surface of the polarizer, and the pressure is 20 to 30 N / cm ² , and the conveyance speed is pasted at about 2 m / min. Combined.

  Step 5: A polarizing plate corresponding to the optical films 101 to 124 is dried for 2 minutes in a drier at 80 ° C., the sample obtained by bonding the polarizer prepared in the step 4, the optical films 101 to 124, and Konica Minoltack KC4UY. 101-124 were produced respectively.

The comparative polyester (A-4) was hot-pressed at 270 ° C. and 9.8 × 10 ⁵ Pa, and stretched by 20% at 145 ° C. to produce a 40 μm film. This polyester film had insufficient bonding properties and could not be bonded by the alkali treatment.

  Moreover, this invention sample had favorable pasting property.

(Heat resistant)
Two 500 mm × 500 mm polarizing plate samples obtained as described above were processed under high temperature and high humidity (conditions: left at 80 ° C. and 90% RH for 100 hours), and the center in the vertical or horizontal direction when orthogonalized. Measure the length of the blank part of the larger edge of the line part, calculate the ratio to the side length (500 mm), and determine according to the ratio divided into 4 ranks as follows The heat and humidity resistance was evaluated. Edge blanking can be determined visually by the fact that the edge portion of the polarizing plate that does not transmit light in an orthogonal state passes light. In the state of the polarizing plate, the display of the edge portion becomes invisible.

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

  As is clear from Table 2, it can be seen that the polarizing plates 101 to 116 of the present invention are practically excellent polarizing plates having good durability as compared with the comparative polarizing plates 117 to 124.

Example 3
<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The polarizing plates on both sides of the Sony 40-type display KLV-40J3000 that had been bonded in advance were peeled off, and the prepared polarizing plates 101 to 125 were bonded to both surfaces of the glass surface of the liquid crystal cell, respectively.

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

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

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

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

A: Front contrast is 0 to less than 5% variation and unevenness is small B: Front contrast is less than 5 to 10% variation and slightly uneven C: Front contrast is 10% or more variation, Unevenness is large Here, A and B were judged to be 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 performed after the liquid crystal display device was placed in the environment for 5 hours.

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

  The above results are shown in Table 3.

  As is apparent from Table 3, the liquid crystal display devices 101 to 116 using the polarizing plates 101 to 116 of the present invention have a viewing angle that is smaller than the liquid crystal display devices 117 to 124 using the comparative polarizing plates 117 to 124. It is excellent in that it satisfies both the small deterioration and the small front contrast unevenness, and it can be seen that it is an extremely stable and durable liquid crystal display device that does not vary in viewing angle even under conditions of changing humidity. .

Claims (8)

  The polyester polyol (A) contains a polyester polyol (A) and a cellulose ester obtained by reacting a dibasic acid having an alicyclic structure or an ester-forming derivative thereof with glycol, and the polyester polyol (A) has a hydroxyl group content. An optical film characterized by being larger than 50%.   The optical film according to claim 1, wherein the polyester polyol (A) has a number average molecular weight of 300 to 3,000.   The optical film according to claim 1 or 2, wherein the dibasic acid having an alicyclic structure has 9 to 14 carbon atoms.   The optical film according to any one of claims 1 to 3, wherein the polyester polyol (A) has a hydroxyl group content of 70% to 100%.   5. The optical film according to claim 1, wherein the polyester polyol (A) has a hydroxyl value of 35 mg / g to 220 mg / g. The retardation Ro represented by the following formula (I) is 20 to 100 nm, and the retardation Rth represented by the following formula (II) is 70 to 300 nm. The optical film described in 1.
Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x in which the refractive index is maximum in the in-plane direction of the optical film, and ny represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the optical film. , Nz represents the refractive index in the thickness direction z of the optical film, and d (nm) represents the thickness of the optical film.)   A polarizing plate comprising the optical film according to claim 1 on at least one surface of a polarizer.   A liquid crystal display device comprising the polarizing plate according to claim 7 on at least one surface of a liquid crystal cell.