JP2012123292A - 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 which has high retardation developability and good brittleness and durability, to provide a polarizing plate which uses the film to have good light resistance and heat and humidity resistance and be excellent in front contrast unevenness and viewing angle deterioration, and to provide a liquid crystal display device.SOLUTION: There are provided an optical film comprising a cellulose ester and including a compound that is represented by general formula (1) and has a molecular weight within the range of 200 to 1,800, and a polarizing plate and a liquid crystal display device using the same.

Description

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

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

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

  For example, a method for obtaining an optical compensation film by adding a compound having a molecular structure having at least two aromatic rings and not sterically hindering the conformation of the two aromatic rings has been proposed (for example, Patent Document 1). See) However, it has been found that the imide compound described in this document does not exhibit a high retardation value. On the other hand, a method for obtaining an optical compensation film having an increased retardation value by adding a specific polyimide compound and further stretching it has been proposed (see, for example, Patent Document 2). However, it has been found that there are problems that the film is brittle and the bleedout resistance is poor.

  In addition, when forming an optical film, slitting of the film is performed for the purpose of removing the knurled portion to be applied to both ends, removing the pinched portion at the time of transverse stretching, or making the wide original fabric a specified width. However, if the film is brittle, the slitting surface becomes rough or breaks, causing a problem that productivity is lowered. In addition, there is a problem that extremely small film waste generated during slitting floats in the process and adheres to the film surface to cause a failure.

  On the other hand, the 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. . The humidity durability of the cellulose ester film depends on the film thickness, and can be improved by reducing the film thickness. On the other hand, if the film thickness is reduced, the retardation value decreases. A compound having high expression is required, and for example, a method of adding an 1,3,5-triazine compound and obtaining an optical compensation film has been proposed (for example, see Patent Document 3). However, even if this compound is used, the retardation is not sufficiently developed. Further, a polarizing plate produced using this optical compensation film and a liquid crystal display device using the polarizing plate have durability such as light resistance and heat and humidity resistance. Turned out to be inferior. Furthermore, there were also problems of front contrast unevenness and viewing angle deterioration due to heat and humidity.

  As described above, the conventionally known retardation developing agent has various problems, and further improvement is desired.

JP 2006-188718A JP 2008-138015 A JP 2006-96875 A

  The present invention has been made in view of the above problems. Accordingly, an object of the present invention is to provide an optical film having high retardation expression and good brittleness and durability. Furthermore, another object of the present invention is to provide a polarizing plate and a liquid crystal display device that have good light resistance and heat and humidity resistance and are excellent in front contrast unevenness and viewing angle deterioration using the optical film.

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

  1. An optical film comprising at least a cellulose ester and a compound represented by the following general formula (1) having a molecular weight in the range of 300 to 1800.

(Wherein L represents an alkylene group, a cycloalkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, —O—, —S—, —CO—, —SO ₂ —, —NR ₁ —, and A divalent linking group formed by combining two or more of these, or a simple bond, A ₁ and A ₂ have a structure represented by the general formula (2), and R ₁ is a hydrogen atom or a substituent R _{2 to} R ₄ represent a hydrogen atom, a bonding point with L, or a substituent, R ₃ and R ₄ may form a ring with each other, and a dotted line part is a single bond or a double bond L is bonded to any position of R _{2 to} R ₄ or a part of the ring formed by R ₃ and R _{4. When} the dotted line is a single bond, each represents a hydrogen atom and R ₃ And a hydrogen atom and R ₄ are bonded.)
2. 2. The optical film as described in 1 above, wherein the general formula (2) is the following general formula (3).

(In the formula, R _{5 to} R ₉ represent a hydrogen atom, a bonding point with L, or a substituent, and R ₆ and R ₇ , R ₇ and R ₈ , R ₈ and R ₉ each form a ring. A ₁ and A ₂ and L in the general formula (1) may be any position of R _{5 to} R ₉ , or R ₅ and R ₆ , R ₆ and R ₇ , R ₇ and R ₈ . Bound to part of the ring
3. 3. The optical film as described in 1 or 2 above, wherein the optical film has a thickness of 20 to 60 μm.

  4). 4. The optical film according to any one of 1 to 3, wherein the optical film has a retardation Ro of 20 to 100 nm and Rth of 70 to 300 nm represented by the following formula.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x 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.)
5. 5. A polarizing plate having the optical film according to any one of 1 to 4 on at least one surface of a polarizer.

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

  According to the present invention, it is possible to provide an optical film having high retardation expression and good brittleness and durability. Furthermore, the optical film can be used to provide a polarizing plate and a liquid crystal display device that have good light resistance and heat and humidity resistance and are excellent in front contrast unevenness and viewing angle deterioration.

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

  As a result of intensive studies on an optical film containing a cellulose ester containing a retardation developer that can solve the above-mentioned problems, the present inventors have developed a high retardation expression by using a dimer of a specific imide compound. It has been found that an optical film having good brittleness and durability can be obtained. Moreover, when the obtained optical film was used, it discovered that the polarizing plate and liquid crystal display device which have favorable light resistance and heat-and-humidity resistance, and are excellent in front contrast nonuniformity and viewing angle deterioration are obtained. Although the detailed reason has not been elucidated, it is likely to increase the anisotropy in the long axis direction of the molecule by making it an imide compound dimer, to have high retardation, and to be in a specific molecular weight range Therefore, it is considered that the affinity with the cellulose ester is increased, and the bleed out and the heat resistance are improved.

  Specifically, it has been found that the above problem can be solved when a specific imide compound having two 5-membered imide rings via a linking group and having a molecular weight in the range of 300 to 1800 is used as a retardation developer. It is up to the present invention.

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

In the general formula (1), L represents an alkylene group, a cycloalkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, —O—, —S—, —CO—, —SO ₂ —, —NR. _1- and a divalent linking group formed by combining two or more of these, or a simple bond, R ₁ represents a hydrogen atom or a substituent, and L may have a substituent.

The substituent that can be substituted for R ₁ and L in the general formula (1) may have a substituent represented by R _{2 to} R ₄ in the general formula (2) described later.

  L is preferably a cycloalkylene group, an arylene group, —O—, —CO—, a group obtained by combining two or more of these four groups, or a simple bond.

A ₁ and A ₂ have a structure represented by the general formula (2).

R _{2 to} R _{4 in the} structure represented by the general formula (2) represent a hydrogen atom, a bonding point with L, or a substituent, and R ₃ and R ₄ may form a ring with each other, It is bonded to any position of R _{2 to} R ₄ or a part of the ring formed by R ₃ and R ₄ .

  The bonding point with L means a position where L is bonded to the general formula (2), and L and an atom adjacent to the bonding point form a bond.

In the general formula (2), R _{2 to} R ₄ represent a hydrogen atom or a substituent. The substituent represented by R _{2 to} R ₄ is not particularly limited, and examples thereof include alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group). Group, dodecyl group, trifluoromethyl group, etc.), cycloalkyl group (eg, cyclopropyl group, cyclopentyl group, cyclohexyl group, adamantyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), acylamino group (eg, , Acetylamino group, benzoylamino group, etc.), alkylthio group (eg, methylthio group, ethylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkenyl group (eg, vinyl group, 2-propenyl group, etc.) 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1- Til-3-butenyl group, 4-hexenyl group, cyclohexenyl group, styryl group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom etc.), alkynyl group (eg, propargyl group etc.), Heterocyclic group (for example, pyridyl group, thiazolyl group, oxazolyl group, pyrazolyl group, imidazolyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, etc.), arylsulfonyl group (for example, phenylsulfonyl group, naphthyl) Sulfonyl group etc.), alkylsulfinyl group (eg methylsulfinyl group etc.), arylsulfinyl group (eg phenylsulfinyl group etc.), phosphono group, acyl group (eg acetyl group, pivaloyl group, benzoyl group etc.), carbamoyl group (Eg aminocarbonyl , Methylaminocarbonyl group, dimethylaminocarbonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylamino) Sulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), sulfonamide group ( For example, methanesulfonamide group, benzenesulfonamide group, etc.), cyano group, alkoxy group (for example, methoxy group, ethoxy group, propoxy group, etc.) ), Aryloxy groups (eg, phenoxy group, naphthyloxy group, etc.), heterocyclic oxy groups, siloxy groups, acyloxy groups (eg, acetyloxy group, benzoyloxy group, etc.), sulfonic acid groups, sulfonic acid salts, amino acids Carbonyloxy group, amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc.), anilino group (for example, phenylamino group, chlorophenyl) Amino group, toluidino group, anisidino group, naphthylamino group, 2-pyridylamino group, etc., imide group, ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group) Group, phenyluree Group, naphthylureido group, 2-pyridylaminoureido group, etc.), alkoxycarbonylamino group (eg, methoxycarbonylamino group, phenoxycarbonylamino group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, phenoxycarbonyl) Etc.), aryloxycarbonyl groups (for example, phenoxycarbonyl groups, etc.), heterocyclic thio groups, thioureido groups, carboxyl groups, carboxylic acid salts, hydroxyl groups, mercapto groups, nitro groups and the like. These substituents may be further substituted with the same substituent.

In the general formula (2), when R ₃ and R ₄ represent a substituent, the two substituents R ₃ and R ₄ may be bonded to form a ring. The formed ring may be substituted with a group similar to the substituent which can be substituted with R _{1 to} R ₄ in the general formula (2).

  The general formula (2) is preferably a structure represented by the general formula (3).

R _{5 to} R _{9 in the} structure represented by the general formula (3) represent a hydrogen atom, a bonding point with L, or a substituent, and R ₆ and R ₇ , R ₇ and R ₈ , R ₈ and R _{9. May} form a ring with each other, and L in the general formula (1) is any position of R _{5 to} R ₉ , or R ₅ and R ₆ , R ₆ and R ₇ , R ₇ and R _8. It is bonded to a part of the ring formed by

In Formula _(3), R 5 ~R ₉ represents a hydrogen atom or a substituent. Examples of the substituent represented by R _{5 to} R ₉ include the same groups as the substituents that can be substituted with R _{2 to} R ₄ in the general formula (2). These substituents may be further substituted with the same substituent.

  In the present invention, the compound represented by the general formula (1) is characterized by having a molecular weight in the range of 300 to 1800. By using the compound represented by the general formula (1) having a molecular weight in the range of 300 to 1800, an optical film having high retardation expression and excellent brittleness and durability can be obtained. In addition, as for the compound represented by the said General formula (1), it is more preferable that molecular weight exists in the range of 350-1200.

Preferred structures of the compound of the general formula (1) in the present invention include the following skeletons. Each of the following skeletons may have a substituent that can be substituted with L in the general formula (1), and a substituent represented by R _{2 to} R ₉ in the general formula (2) and the general formula (3). good.

  More preferable skeletons include S-01, S-02, S-03, S-06, and S-07, and S-01 is particularly preferable.

In the present invention, A ₁ and A _{2 in} the general formula (1) preferably have a structure represented by the general formula (3). By using the compound represented by the general formula (1) containing the structure of the general formula (3) having a molecular weight in the range of 300 to 1800, it has further high retardation expression, brittleness and durability. An excellent optical film can be obtained.

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

  These compounds can be produced by known methods.

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

Synthesis example 1
(Synthesis of Exemplary Compound A-011)

  At room temperature, 5.00 g of compound A, 3.80 g of compound B, and 20 ml of sulfolane were mixed and then heated to reflux at 170 ° C. for 5 hours. After completion of the reaction, the mixture was cooled to room temperature and stirred for 1 hour. The solid was filtered, washed with acetone, and dried to obtain 7.67 g of Compound C.

  At room temperature, 3.5 g of Compound C, 0.5 g of pyridine, and 30 ml of dimethylacetamide were added and stirred at 50 ° C. Compound D was added dropwise to the reaction solution little by little. After completion of dropping, the mixture was stirred for 7 hours at 50 ° C., 30 ml of methanol was added, and the mixture was stirred for 1 hour. After cooling to room temperature, the precipitated solid was filtered and washed with methanol to obtain 3.3 g of Exemplified Compound A-011.

As a result of analyzing the obtained crystal by ¹ H-NMR and MASS spectrum, it was confirmed to be Exemplified Compound A-011.

¹ H-NMR (400 MHz, DMSO-d6, δ (ppm), TMS standard): 0.87-0.91 (m, 12H), 1.29-1.40 (m, 16H), 1.65 ( m, 2H), 4.16 (d, 4H), 7.41 (d, 4H), 7.55 (d, 4H), 8.10 (d, 2H), 8.30-8.43 (m , 4H)
Synthesis example 2
(Synthesis of Exemplified Compound A-045)

  At room temperature, 5.00 g of compound E, 3.91 g of compound F, and 25 ml of sulfolane were mixed and then heated to reflux at 170 ° C. for 5 hours. After completion of the reaction, the mixture was cooled to 80 ° C., 20 ml of ethyl acetate was slowly added while paying attention to bumping, and then 20 ml of methanol was added. After stirring at room temperature for 1 hour, the solid was filtered, washed with ethyl acetate and methanol, and then dried to obtain 7.00 g of exemplary compound A-045.

As a result of analyzing the obtained crystal by ¹ H-NMR and MASS spectrum, it was confirmed to be Exemplified Compound A-045.

¹ H-NMR (400 MHz, DMSO-d6, δ (ppm), TMS standard): 3.75 (s, 6H), 7.10 (t, 2H), 7.22 (d, 2H), 7.39 (D, 2H), 7.49 (t, 2H), 8.10-8.21 (m, 4H), 8.30 (d, 2H)
Synthesis example 3
(Synthesis of Exemplary Compound A-065)

  At room temperature, 10.0 g of compound G and 6.8 g of compound F were mixed, and then heated and heated at 140 ° C. for 30 minutes. Since the reaction solution was solidified, 20 ml of xylene was added and heated to reflux at 140 ° C. for 5 hours. Thereafter, the mixture was cooled to room temperature, and the solid was crushed and stirred for 1 hour. The solid was filtered and washed with toluene. The obtained solid was suspended and purified with 30 ml of methanol to obtain 13.92 g of Compound H.

  At room temperature, 5.00 g of compound H, 0.5 ml of dimethylformamide, 3.00 g of thionyl chloride and 20 ml of toluene were added and heated to 60 ° C. and stirred. After 2 hours, the mixture was cooled to room temperature, and the solvent and excess thionyl chloride were distilled off under reduced pressure to obtain Compound I.

  At room temperature, 1.02 g of methylhydroquinone, 2.0 g of pyridine, and 5 ml of dimethylacetamide were mixed and stirred at room temperature. Thereafter, Compound I dispersed in 10 ml of dimethylacetamide was added dropwise little by little. The reaction solution was heated to 100 ° C. and stirred for 3 hours. After completion of the reaction, the mixture was cooled to room temperature and the precipitated solid was filtered, washed with methanol, and dried to obtain 3.70 g of Exemplified Compound A-065.

As a result of analyzing the obtained crystal by ¹ H-NMR and MASS spectrum, it was confirmed to be Exemplified Compound 25.

¹ H-NMR (400 MHz, DMSO-d6, δ (ppm), TMS standard): 2.25 (s, 3H), 3.76 (s, 6H), 7.11 (t, 2H), 7.25 (D, 2H), 7.29-7.7.62 (m, 7H), 8.10-8.22 (m, 2H), 8.56 (d, 2H), 8.60-8.70 (M, 2H)
Other exemplified compounds can also be synthesized in the same manner as in Synthesis Examples 1 to 3.

  Although the compound represented by General formula (1) which concerns on this invention can adjust and contain a quantity suitably in order to provide desired retardation, as addition amount, it is 1 to The content is preferably 15% by mass, and particularly preferably 2 to 10% by mass. If it is in this range, sufficient retardation can be imparted to the cellulose ester of the present invention.

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

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

  As the resin of the film that becomes the base material of the optical film of the present invention, a cellulose ester resin (also referred to simply as a cellulose ester in the present invention) is used, but other resins that can be used in combination include polycarbonate resins and polystyrene. Resin, polysulfone resin, polyester resin, polyarylate resin, acrylic resin, olefin resin (norbornene resin, cyclic olefin resin, cyclic conjugated diene resin, vinyl alicyclic hydrocarbon resin, etc.), etc. Can be mentioned. Among these, a cellulose ester resin, a polycarbonate resin, an acrylic resin, and a cyclic olefin resin may be used in combination. When using resin other than cellulose ester, the content is preferably 5 to 70% by mass.

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

<Cellulose ester>
Although it does not specifically limit as a cellulose ester based on this invention, It is preferable that it is a C2-C22 linear or branched carboxylic acid ester, These carboxylic acid may form a ring and aromatic carboxylic acid. It may be an 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. The mixed fatty acid ester of cellulose is mentioned.

  Preferred cellulose esters according to the present invention preferably satisfy the following formulas (a) and (b).

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 according to the present invention is preferably in the range of 60,000 to 300,000, since 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.

  Although there is no limitation in particular as a cellulose of the raw material of the cellulose ester which concerns on this invention, Cotton linter, wood pulp, kenaf etc. can be mentioned. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

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

  In addition to the cellulose ester and the compound represented by the general formula (1), the optical film of the present invention includes a sugar ester compound, a plasticizer, an ultraviolet absorber, an antioxidant, and fine particles described below. It is preferable to add at least one.

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

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

  Examples of the sugar ester compound used in the present invention include the following, but are 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 group in the pyranose structure or furanose structure is not particularly limited, and is a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic A 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 applied as a compound having 1 to 12 at least one of a pyranose structure or a furanose structure.

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

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

Monopet SB: manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Monopet SOA: manufactured by Daiichi Kogyo Seiyaku Co., Ltd. The sugar ester compound is preferably added in an amount of 0.5 to 30% by mass with respect to the cellulose ester. 5 to 20% by mass is preferable.

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

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

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

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

  There is no restriction | limiting in particular as alcohol used for a 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 benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. And aromatic monocarboxylic acids possessed by them, or derivatives thereof. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  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 that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Viscosity (25 ° C., mPa · s); 37000
Acid value: 0.05
<Acrylic polymer>
The optical film according to the present invention can also contain a (meth) acrylic polymer as a plasticizer.

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

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

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

Formula (X)
_{- [CH 2 -C (-Rc)} (- CO 2 Rd)] m- [CH 2 -C (-Re) (- CO 2 Rf-OH) -] n- [Xc] p-
General formula (Y)
_{Ry- [CH 2 -C (-Rg)} (- CO 2 Rh-OH) -] k- [Yb] q-
(.Rf wherein, Rc, Re, Rg is, .rd representing H or CH3 is represents an alkyl group, a cycloalkyl group having 1-12 carbon atoms, Rh is _{-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 represents a monomer that can be copolymerized to Ya. M, n, k, p and q represent molar composition ratios, where m ≠ 0, n ≠ 0, k ≠ 0, m + n + p = 100, and k + q = 100.
The amount of these plasticizers added is preferably 0.5 to 30% by mass, and particularly preferably 5 to 20% by mass with respect to the cellulose ester.

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

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

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, There are tinuvins such as tinuvin 928, and these are all commercially available products from BASF 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 according to the present invention preferably contains two or more ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

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

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

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but when the dry film thickness of the polarizing plate protective film is 30 to 200 μm, it is 0.5 with respect to the polarizing plate protective film. -10 mass% is preferable, and 0.6-4 mass% is 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.

  Antioxidants have the role of delaying or preventing the optical film from being decomposed by, for example, the residual solvent amount of halogen in the optical film or phosphoric acid of the phosphoric acid plasticizer, so it is contained in the optical film. It is preferable to do so.

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

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

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

<Fine particles>
The optical film according to the present invention preferably contains fine particles.

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

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

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

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

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

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

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

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

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

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

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

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

<Production method>
Next, the manufacturing method of the optical film which concerns on this invention is demonstrated.

  The optical film according to the present invention 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 production of the optical film according to the present invention comprises a step of dissolving a cellulose ester and an additive in a solvent to prepare a dope, a step of casting a dope on an endless metal support, and casting the dope. It is carried out by a step of drying as a web, a step of peeling from a metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

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

  The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent. Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, cellulose acetate (acetyl group substitution degree 2.4), cellulose acetate Propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

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

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

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

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

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and 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, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is 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 cellulose ester by filtration.

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

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The expression of the difference (referred to as differential pressure) is small and preferable. A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and 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 according to the present invention, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are gripped by clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

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

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

  Although the film thickness of an optical film is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20-60 micrometers. If it is this range, since the improvement of the moisture permeability depending on the film thickness of a film and the expression of the retardation by the retardation developing agent concerning this invention can be compatible, it is preferable.

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

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

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

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

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

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

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

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

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

  When the optical film according to the present invention is used in the VA mode, a mode in which a total of two sheets are used on each side of the cell (two-sheet type) and a mode in which only one of the upper and lower sides of the cell is used (1 It may be used for any of the sheet type).

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

  These retardation values can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments).

  The slow axis or the fast axis of the optical film according to the present invention is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less, assuming that the angle formed with the film forming direction is θ1. More preferably, it is 5 ° or more and + 0.5 ° or less. This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

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

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

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

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

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

<Polarizing plate>
The optical film according to the present invention can be used in the polarizing plate of the present invention and the liquid crystal display device of the present invention using the polarizing plate. The optical film according to the present invention is preferably a film that also functions as a polarizing plate protective film. In that case, it is not necessary to prepare an optical film having a phase difference separately from the polarizing plate protective film. The manufacturing process can be simplified by reducing the thickness of the apparatus.

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

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

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

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

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

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

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

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

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

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

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

Example 1
<Preparation of optical film 101>
<Fine particle dispersion 1>
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

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

Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass 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 acetylation degree of 60.9% (described as TAC in the table) 100 parts by mass Retardation developer: Exemplified compound A-011 3 parts by mass Monopet SB ( (Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by mass Particulate additive solution 1 1 part by mass The above was put into a sealed container and dissolved while stirring to prepare a dope solution. Next, an endless belt casting apparatus was used to uniformly cast the dope solution on a stainless steel belt support at a temperature of 35 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

  On the stainless steel belt support, the solvent was evaporated until the 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 102-130>
Optical films 102 to 130 were prepared in the same manner as in the production of the optical film 101 except that the type of cellulose ester or the additive in place of the exemplary compound A-011 was changed as shown in Table 1. In addition, the addition amount of the cellulose ester replaced with the used cellulose ester A (TAC) was the same mass part as the cellulose ester A (TAC).

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

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

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

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

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

Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(Where nx is the maximum refractive index in the film plane, ny is the refractive index in the direction perpendicular to nx, nz is the refractive index in the film thickness direction, and d is the thickness (nm) of the film.)
(Slitting aptitude)
Brittleness was evaluated by the slitting suitability described below.

  After attaching the 60 ° worn upper blade and the 90 ° lower blade to the hydraulic table press machine at a distance of 30 μm, each optical film was placed between both blades, and the lowering speed of the upper blade was 6 m / In minutes, 100 samples having a width of 90 cm and a length of 100 cm were continuously cut out. The cut surfaces of the cut samples were observed at 50 times using an optical microscope, and the sharpness was compared. The number of films in which some defects such as burrs, cleavage, cutting, or chipping occurred was counted, the defect rate was calculated, and the cutting property was evaluated according to the following criteria.

A: Defect rate is less than 2% B: Defect rate is less than 2-5% C: Defect rate is less than 5-10% D: Defect rate is 10% or more did.

(Bleed-out resistance)
The durability was evaluated by the bleed-out resistance described below.

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

A: No bleed-out is observed on the surface B: Partial bleed-out is slightly observed on the surface C: Slight bleed-out is observed on the entire surface D: On the entire surface A clear bleed-out is recognized. A and B were judged to be practically satisfactory levels.

  As is clear from Table 1, the optical films 101 to 124 of the present invention are more excellent in retardation development than the comparative optical films 125 to 130, and are brittle (slitting suitability) and durability (bleed out resistance). ) Is a practically excellent optical film. Further, from the results of the optical films 125 and 127 using the comparative compounds 1 and 3, in order to achieve the object of the present invention, it is necessary to adjust the molecular weight of the retardation developer within the scope of the present invention. It can be said. In addition, the optical film 129 which does not contain a retardation developer has a small retardation value and does not have any function as an optical compensation film.

Example 2
The optical film was used in the same manner as in Example 1 except that the dope liquid used in the production of the optical film 101 of Example 1 was used and the flow rate of the dope liquid during casting was changed so that the film thickness was as shown in Table 2. 201-206 were produced and evaluated in the same manner as in Example 1.

  As is apparent from Table 2, it can be seen that the optical films 201 to 206 of the present invention are excellent in retardation development, and are excellent in brittleness (slitting suitability) and durability (bleedout resistance). Further, it can be seen that the effect is particularly high in 202 to 205 having a film thickness of 20 to 60 μm.

Example 3
<Preparation of polarizing plate>
A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times).

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

  Next, according to the following steps 1 to 5, a polarizer, the optical films 101 to 130 and 201 to 206, and Konica Minolta Tack KC4UY (cellulose ester film manufactured by Konica Minolta Opto Co., Ltd.) are bonded to the back side to form a polarizing plate. Produced.

  Step 1: It was 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 129 and 201 to 206 laminated in Step 3 were bonded to the polarizer on the back side cellulose ester film at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Step 5: A sample prepared by bonding the polarizer prepared in Step 4 with the optical films 101 to 129 and 201 to 206 and Konica Minoltack KC4UY in a dryer at 80 ° C. for 2 minutes, and polarizing plates 101 to 129, 201-206 were produced.

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

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

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

A: Polarization degree change amount is less than 2% B: Polarization degree change amount is 2% or more and less than 10% C: Polarization degree change amount is 10% or more and less than 25% D: Polarization degree change amount is 25% or more , B was judged to be a practically acceptable level.

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

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

  As is clear from Table 3, the polarizing plates 101 to 124 and 201 to 206 of the present invention are practically excellent polarizing plates having good light resistance and heat and humidity resistance as compared with the comparative polarizing plates 125 to 130. I understand. Further, from the results of the polarizing plates 125 and 127 using the comparative compounds 1 and 3, in order to achieve the object of the present invention, it is necessary to adjust the molecular weight of the retardation developer within the range of the present invention. It can be said.

Example 4
<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The polarizing plates on both sides of the 40-inch display KLV-40J3000 made in advance were peeled off, and the produced polarizing plates 101 to 130 and 201 to 206 were bonded to both surfaces of the glass surface of the liquid crystal cell, respectively.

  At that time, the direction of bonding of the polarizing plate is such that the surface of the optical film of the present invention is on the liquid crystal cell side and the absorption axis is directed in the same direction as the polarizing plate previously bonded. Then, liquid crystal display devices 101 to 130 and 201 to 206 were produced.

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

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

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

A: Front contrast is 0 to less than 5% variation and unevenness is small B: Front contrast is less than 5 to 10% variation and slightly uneven C: Front contrast is 10% or more variation, 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.

  As is clear from Table 4, the liquid crystal display devices 101 to 124 and 201 to 206 using the polarizing plates 101 to 124 and 201 to 206 of the present invention are the liquid crystal display devices 125 to 125 using the comparative polarizing plates 125 to 130. It can be seen that the liquid crystal display device is extremely stable and excellent in durability, with no front contrast unevenness and no fluctuation in viewing angle even under conditions where the humidity varies. Further, from the results of the liquid crystal display devices 125 and 127 using the comparative compounds 1 and 3, in order to achieve the object of the present invention, it is necessary to adjust the molecular weight of the retardation developer within the scope of the present invention. It can be said that there is.

Claims (6)

An optical film comprising at least a cellulose ester and a compound represented by the following general formula (1) having a molecular weight in the range of 300 to 1800.

(Wherein L represents an alkylene group, a cycloalkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, —O—, —S—, —CO—, —SO ₂ —, —NR ₁ —, and A divalent linking group formed by combining two or more of these, or a simple bond, A ₁ and A ₂ have a structure represented by the general formula (2), and R ₁ is a hydrogen atom or a substituent R _{2 to} R ₄ represent a hydrogen atom, a bonding point with L, or a substituent, R ₃ and R ₄ may form a ring with each other, and a dotted line part is a single bond or a double bond L is bonded to any position of R _{2 to} R ₄ or a part of the ring formed by R ₃ and R _{4. When} the dotted line is a single bond, each represents a hydrogen atom and R ₃ And a hydrogen atom and R ₄ are bonded.) The optical film according to claim 1, wherein the general formula (2) is the following general formula (3).

(In the formula, R _{5 to} R ₉ represent a hydrogen atom, a bonding point with L, or a substituent, and R ₆ and R ₇ , R ₇ and R ₈ , R ₈ and R ₉ each form a ring. A ₁ and A ₂ and L in the general formula (1) may be any position of R _{5 to} R ₉ , or R ₅ and R ₆ , R ₆ and R ₇ , R ₇ and R ₈ . Bound to part of the ring   The optical film according to claim 1, wherein the optical film has a thickness of 20 to 60 μm. The optical film according to any one of claims 1 to 3, wherein the optical film has a retardation Ro of 20 to 100 nm and Rth of 70 to 300 nm represented by the following formula.
Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
(However, nx represents the refractive index in the direction x 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 5 on at least one surface of a liquid crystal cell.