JP2007041280A - Retardation film, polarizing plate and liquid crystal display using them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin retardation film capable of decreasing harmful materials during production and excellent in productivity, and to provide an optically compensated thin polarizing plate usable even in a liquid crystal television. <P>SOLUTION: The retardation film comprises a cellulose ester having a total substitution degree of acyl groups of 2.50-2.65 and an ultraviolet absorbing copolymer synthesized from an ultraviolet absorbing monomer represented by formula (1), a hydrophilic ethylenically unsaturated monomer and an ethylenically unsaturated monomer, wherein n represents an integer of 0-3; R<SB>1</SB>-R<SB>5</SB>each represent H, halogen or a substituent; X represents -COO-, -CONR<SB>7</SB>-, -OCO- or -NR<SB>7</SB>CO-; and R<SB>6</SB>and R<SB>7</SB>each represent H, alkyl or aryl, provided that a group represented by R<SB>6</SB>has a polymerizable group as a partial structure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a retardation film using a cellulose ester that is excellent in productivity, a thin film polarizing plate using the retardation film, and a liquid crystal display device.

  In recent years, there has been a remarkable spread of liquid crystal display devices such as notebook computer and desktop computer liquid crystal monitors, and most personal computers in offices and homes have been converted into liquid crystals. Recently, household televisions are also becoming thinner and large LCD televisions are becoming more popular. For this reason, the production volume of liquid crystal display devices has also increased significantly and is expected to increase further in the future.

On the other hand, environmental concerns such as global warming are high, and the regulation of harmful substances has begun at the world level. A cellulose ester film that uses methylene chloride, which is a harmful substance, is used for polarizing plates used in liquid crystal display devices. From the viewpoint of environmental problems, manufacturing methods that do not use methylene chloride are also being studied, but there are many problems such as ensuring safety and costs with flammable organic solvents, and they have not been put into practical use. Therefore, efforts are being made to increase the recovery rate of methylene chloride in order to increase the production amount by reducing the amount of methylene chloride released below a certain amount. At present, the recovery rate is set to 99% or more, but it is difficult to increase the recovery rate. The cause is the amount of residual methylene chloride in the film. The extremely small amount of methylene chloride contained in the film is a non-negligible amount in the region where the recovery rate is 99% or more. In order to reduce the amount of residual methylene chloride, the drying temperature is increased and the drying zone is extended to the practical limit, but further reduction is difficult. An effective means for reducing the residual methylene chloride is thinning. The amount of residual methylene chloride can be reduced to 1/10 by setting the cellulose ester film having a normal film thickness of 80 μm to 40 μm. In addition, since the amount of methylene chloride used for producing 1 m ² can be halved, it is very favorable for the global environment.

  For this reason, we want to increase the thinning ratio of cellulose ester film. However, for liquid crystal televisions and liquid crystal monitors, which are currently being used in large quantities, retardation films are used to expand the viewing angle. It was difficult to reduce the film thickness. Since the retardation film made of cellulose ester also has a function of a protective film, it is used by being directly bonded to one surface of a polarizer. Therefore, the same film thickness film is also used for the cellulose ester protective film bonded to the opposite side from the viewpoint of curling prevention. This did not increase the thinning ratio of the cellulose ester protective film.

  Since the retardation required for the retardation film is proportional to the film thickness, the retardation decreases when the film thickness is reduced. In order to increase the retardation, a method of adding a retardation increasing agent has been proposed. (Patent Document 1) However, in this method, if an attempt is made to increase the retardation to a target value with a thin film, the amount of addition increases and a problem of bleed out occurs, which makes it difficult to put it to practical use. As another method, a method for reducing the total acyl group substitution degree has been proposed (Patent Document 2). In this case, the hygroscopicity is increased, and the ultraviolet absorber is eluted by alkali saponification treatment, or cellulose. The ester resin itself is dissolved to generate foreign matter. Moreover, since problems such as deterioration of the polarizer occur under high temperature and high humidity conditions, it has been difficult to put into practical use.

As a result of intensive studies, we have determined the practical range of the total acyl group substitution degree, and further using a polymer ultraviolet absorber with a specific structure, so that foreign substances are generated by alkali saponification and the polarizer deteriorates under high temperature and high humidity conditions. And the present invention has been found. This makes it possible to provide a thin film retardation film that is friendly to the global environment and excellent in productivity. By using this together with a thin film polarizing plate protective film, optical compensation that can also be used for liquid crystal televisions has been achieved. A thin film polarizing plate is provided.
JP 2000-1111914 A JP 2004-170760 A

  It is possible to reduce the harmful substances during production and to provide a thin film retardation film with excellent productivity. By using it together with a thin film polarizing plate protective film, it can be used for liquid crystal televisions. It is to provide a thin film polarizing plate.

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

  (1) From a cellulose ester having a total acyl group substitution degree of 2.50 to 2.65, an ultraviolet absorbing monomer represented by the following general formula (1), a hydrophilic ethylenically unsaturated monomer, and an ethylenically unsaturated monomer A retardation film comprising a synthesized UV-absorbing copolymer and having a thickness of 30 to 60 μm.

[Wherein n represents an integer of 0 to 3, R _{1 to} R ₅ represent a hydrogen atom, a halogen atom, or a substituent, and X represents —COO—, —CONR ₇ —, —OCO—, —NR ₇ Represents CO—, and R ₆ and R ₇ represent a hydrogen atom, an alkyl group, or an aryl group. However, the group represented by R ₆ has a polymerizable group as a partial structure. ]
(2) The retardation film according to (1), wherein the retardation value Ro defined by the following formula (I) or (II) is 30 to 100 nm, and Rt is 100 to 300 nm. .

Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
[In the formula, nx is the refractive index in the direction with the largest refractive index in the film plane, ny is the refractive index in the film plane in the direction perpendicular to nx, nz is the refractive index in the thickness direction of the film, and d is the refractive index of the film. Each thickness is expressed in nm. ]
(3) The retardation film as described in (1) or (2) above, which contains an ester plasticizer represented by the following general formula (2).

General formula (2)
B- (GA) _n -GB
[Wherein B represents a benzene monocarboxylic acid residue. G represents an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms and an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. n is an integer of 1-5. ]
(4) The retardation film as described in any one of (1) to (3) above, which contains a polyhydric alcohol ester.

  (5) A polarizing plate using the retardation film according to any one of (1) to (4).

  (6) The polarizing plate according to (5), wherein the polarizer used in the polarizing plate is a 10 to 20 μm-thick polarizer using a polyethylene-polyvinyl alcohol copolymer.

  (7) A liquid crystal display device using the retardation film according to any one of (1) to (4).

  According to the present invention, it is possible to provide a thin film retardation film that can reduce harmful substances during production and is excellent in productivity. This can provide an optically compensated thin film polarizing plate that can also be used in a liquid crystal television.

  The best mode for carrying out the present invention will be described below.

(Cellulose ester)
The cellulose ester used in the present invention is a cellulose ester having a total acyl group substitution degree of 2.50 to 2.65. When the total acyl group substitution degree exceeds 2.65, the retardation development required for the thin film retardation film cannot be obtained. On the other hand, if it is less than 2.50, the ultraviolet absorber is eluted by alkali saponification treatment, or the surface of the cellulose ester film is peeled off, and foreign matter is generated in the saponification solution. In addition, the polarizer deteriorates under high temperature and high humidity conditions. The cellulose ester is preferably a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose ester means a fatty acid having 6 or less carbon atoms, such as cellulose acetate, cellulose propionate, cellulose butyrate, etc., and JP-A Nos. 10-45804 and 8- As the mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in No. 231761, US Pat. No. 2,319,052, etc., lower fatty acid esters of cellulose can be used.

  As a measuring method of the acyl group substitution degree of a cellulose ester, it can implement according to ASTM-D-817-96.

  Among the above fatty acids, cellulose acetate propionate and cellulose acetate butyrate are more preferable.

The most preferred lower fatty acid ester of cellulose has an acyl group having 2 to 4 carbon atoms as a substituent, where X is the acetyl group substitution degree and Y is the propionyl group or butyryl group substitution degree. 2.40 ≦ X + Y ≦ 2. 60
Those in the range of 0.7 ≦ Y ≦ 1.1 are used.
The range of 0.8 ≦ Y ≦ 1.0 is more preferable. Increasing the degree of propionyl group or butyryl group substitution is preferable because it improves hygroscopicity and lowers the elastic modulus, but if it is too high, the heat resistance deteriorates, so the above range is preferable. In addition, a propionyl group is more preferable than a butyryl group because of excellent heat resistance.

  The cellulose ester preferably has a molecular weight distribution Mw / Mn obtained by dividing the weight average molecular weight Mw by the number average molecular weight Mn from 1.4 to 3.0. More preferably, it is 1.4-2.2. By making it in this range, the expression of phase difference when stretched, white turbidity and the like are improved.

  The molecular weight of cellulose acetate is 30000-200000 in terms of number average molecular weight (Mn). The thing of 35000-70000 is still more preferable. When the number average molecular weight (Mn) is less than 30000, wrinkles are likely to be formed during film formation, and when the number average molecular weight (Mn) exceeds 200000, the dope viscosity becomes very high, which is not preferable for production.

  The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight Mn and the weight average molecular weight Mw can be calculated, and the ratio (Mw / Mn) can be calculated.

  The measurement conditions are as follows.

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

  As the cellulose ester, a cellulose ester synthesized from cotton linter, a cellulose ester synthesized from wood pulp, and a cellulose ester synthesized from other raw materials can be used alone or in combination.

  Cellulose esters are also affected by trace metal components in cellulose esters. These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small. The iron (Fe) component is preferably 1 ppm or less. About calcium (Ca) component, it is contained in a lot of ground water and river water, etc., and it becomes hard water, and it is unsuitable as drinking water. Coordination compounds with ligands, that is, complexes are easily formed, and scum (insoluble starch, turbidity) derived from many insoluble calcium is formed.

  The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter. Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After performing, it can obtain | require by performing an analysis using ICP-AES (inductively coupled plasma emission spectroscopy analyzer).

  Instead of cellulose ester, a recycled material of cellulose ester film may be used. Recycled material is a finely pulverized cellulose ester film, which is generated when the cellulose ester film is formed, and is obtained by cutting out both sides of the film, or by using a cellulose film raw material that has been speculated out of scratches. Is done.

  The use ratio of the recycled material is preferably 0 to 70% by mass, more preferably 10 to 50% by mass, and most preferably 20 to 40% by mass with respect to the solid content of the prescription value such as the main dope. It is preferable to set the amount within the above range because the greater the amount of recycled material used, the better the filterability, and the smaller the amount of recycled material used, the better the slipperiness.

  When the recycled material is used, the additives contained in the cellulose ester film such as plasticizers, ultraviolet absorbers, and fine particles are reduced according to the amount used, and the final cellulose ester film composition becomes the design value. Make adjustments as follows.

(UV absorber)
In the present invention, a UV-absorbing copolymer (polymer UV absorber) synthesized from the UV-absorbing monomer represented by the general formula (1) and an ethylenically unsaturated monomer is contained.

In the general formula (1), n represents an integer of 0 to 3, and when n is 2 or more, the plurality of R ₅ may be the same or different, and are connected to each other to form 5-7. A member ring may be formed.

R _{1 to} R ₅ each represents a hydrogen atom, a halogen atom or a substituent. As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom etc. are mentioned, for example, Preferably they are a fluorine atom and a chlorine atom. Examples of the substituent include an alkyl group (for example, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl group), alkenyl group (for example, vinyl group). , Allyl group, 3-buten-1-yl group, etc.), aryl group (eg, phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, etc.), heterocyclic group (eg, pyridyl group, benzimidazolyl group) , Benzthiazolyl group, benzoxazolyl group, etc.), alkoxy group (eg methoxy group, ethoxy group, isopropoxy group, n-butoxy group etc.), aryloxy group (eg phenoxy group etc.), heterocyclic oxy group (eg For example, 1-phenyltetrazol-5-oxy group, 2-tetrahydropyranyloxy group, etc.), Ruoxy group (for example, acetoxy group, pivaloyloxy group, benzoyloxy group, etc.), acyl group (for example, acetyl group, propanoyl group, butyroyl group, etc.), alkoxycarbonyl group (for example, methoxycarbonyl group, ethoxycarbonyl group, etc.), aryl Oxycarbonyl group (for example, phenoxycarbonyl group), carbamoyl group (for example, methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group, etc.), amino group, alkylamino group (for example, methylamino group, ethylamino group, diethylamino group) Anilino group (for example, anilino group, N-methylanilino group, etc.), acylamino group (for example, acetylamino group, propionylamino group, etc.), hydroxyl group, cyano group, nitro group, sulfonamide (Eg, methanesulfonamide group, benzenesulfonamide group, etc.), sulfamoylamino group (eg, dimethylsulfamoylamino group, etc.), sulfonyl group (eg, methanesulfonyl group, butanesulfonyl group, phenylsulfonyl group, etc.) , Sulfamoyl group (eg, ethylsulfamoyl group, dimethylsulfamoyl group, etc.), sulfonylamino group (eg, methanesulfonylamino group, benzenesulfonylamino group, etc.), ureido group (eg, 3-methylureido group, 3 , 3-dimethylureido group, 1,3-dimethylureido group etc.), imide group (eg phthalimide group etc.), silyl group (eg trimethylsilyl group, triethylsilyl group, t-butyldimethylsilyl group etc.), alkylthio group (Eg methylthio Group, ethylthio group, n-butylthio group and the like), arylthio group (for example, phenylthio group and the like), and the like, preferably an alkyl group and an aryl group.

In the general formula (1), when each group represented by R _{1 to} R ₅ is a further substitutable group, it may further have a substituent, and adjacent R _{1 to} R ₄ are They may be connected to each other to form a 5- to 7-membered ring.

R ₆ represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic ring. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, n- Examples thereof include a butyl group, an isobutyl group, a t-butyl group, an amyl group, an isoamyl group, and a hexyl group. The alkyl group may further have a halogen atom or a substituent, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the substituent include An aryl group (eg, phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, etc.), acyl group (eg, acetyl group, propanoyl group, butyroyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, Isopropoxy group, n-butoxy group, etc.), aryloxy group (eg, phenoxy group, etc.), amino group, alkylamino group (eg, methylamino group, ethylamino group, diethylamino group etc.), anilino group (eg, anilino group) Group, N-methylanilino group, etc.), acylamino group (for example, acetylamino group, propioni) Amino group, etc.), hydroxyl group, cyano group, carbamoyl group (eg, methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group, etc.), acyloxy group (eg, acetoxy group, pivaloyloxy group, benzoyloxy group, etc.), alkoxycarbonyl group (For example, a methoxycarbonyl group, an ethoxycarbonyl group, etc.) and an aryloxycarbonyl group (for example, a phenoxycarbonyl group, etc.) are mentioned.

  Examples of the cycloalkyl group include saturated cyclic hydrocarbons such as a cyclopentyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group, which may be unsubstituted or substituted.

  Examples of the alkenyl group include a vinyl group, an allyl group, a 1-methyl-2-propenyl group, a 3-butenyl group, a 2-butenyl group, a 3-methyl-2-butenyl group, and an oleyl group. Is a vinyl group, 1-methyl-2-propenyl group.

  Examples of the alkynyl group include ethynyl group, butadiyl group, phenylethynyl group, propargyl group, 1-methyl-2-propynyl group, 2-butynyl group, 1,1-dimethyl-2-propynyl group, Preferably, they are an ethynyl group and a propargyl group.

  Examples of the aryl group include a phenyl group, a naphthyl group, and an anthranyl group. The aryl group may further have a halogen atom or a substituent. Examples of the halogen atom include a fluorine atom and chlorine. Atoms, bromine atoms, iodine atoms and the like. Examples of the substituent include alkyl groups (for example, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl group). Etc.), acyl groups (eg acetyl group, propanoyl group, butyroyl group etc.), alkoxy groups (eg methoxy group, ethoxy group, isopropoxy group, n-butoxy group etc.), aryloxy groups (eg phenoxy group etc.) ), Amino group, alkylamino group (for example, methylamino group, ethylamino group, diethyl) Mino group etc.), anilino group (eg anilino group, N-methylanilino group etc.), acylamino group (eg acetylamino group, propionylamino group etc.), hydroxyl group, cyano group, carbamoyl group (eg methylcarbamoyl group, Ethylcarbamoyl group, dimethylcarbamoyl group, etc.), acyloxy group (eg, acetoxy group, pivaloyloxy group, benzoyloxy group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, etc.), aryloxycarbonyl group (eg, Phenoxycarbonyl group and the like).

Examples of the heterocyclic group include a pyridyl group, a benzimidazolyl group, a benzthiazolyl group, and a benzoxazolyl group. R ₆ is preferably an alkyl group.

In the general formula (1), X represents —COO—, —CONR ₇ —, —OCO—, or —NR ₇ CO—.

R ₇ represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, and examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, Examples thereof include a t-butyl group, an amyl group, an isoamyl group, and a hexyl group. Such an alkyl group may further have a halogen atom or a substituent. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the substituent include an aryl group. Group (for example, phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, etc.), acyl group (for example, acetyl group, propanoyl group, butyroyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, iso group) Propoxy group, n-butoxy group, etc.), aryloxy group (eg, phenoxy group, etc.), amino group, alkylamino group (eg, methylamino group, ethylamino group, diethylamino group, etc.), anilino group (eg, anilino group) N-methylanilino group), acylamino group (for example, acetylamino group, propionyl) Mino group, etc.), hydroxyl group, cyano group, carbamoyl group (eg, methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group, etc.), acyloxy group (eg, acetoxy group, pivaloyloxy group, benzoyloxy group, etc.), alkoxycarbonyl group (For example, a methoxycarbonyl group, an ethoxycarbonyl group, etc.) and an aryloxycarbonyl group (for example, a phenoxycarbonyl group, etc.) are mentioned.

  Examples of the cycloalkyl group include saturated cyclic hydrocarbons such as a cyclopentyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group, which may be unsubstituted or substituted.

  Examples of the aryl group include a phenyl group, a naphthyl group, and an anthranyl group. The aryl group may further have a halogen atom or a substituent, and the halogen atom includes a fluorine atom, a chlorine atom, Examples of the substituent include an alkyl group (for example, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl group). An acyl group (for example, acetyl group, propanoyl group, butyroyl group, etc.), an alkoxy group (for example, methoxy group, ethoxy group, isopropoxy group, n-butoxy group, etc.), an aryloxy group (for example, phenoxy group, etc.), Amino group, alkylamino group (for example, methylamino group, ethylamino group, diethylamino group) ), Anilino group (for example, anilino group, N-methylanilino group, etc.), acylamino group (for example, acetylamino group, propionylamino group, etc.), hydroxyl group, cyano group, carbamoyl group (for example, methylcarbamoyl group, ethylcarbamoyl group) Group, dimethylcarbamoyl group, etc.), acyloxy group (eg acetoxy group, pivaloyloxy group, benzoyloxy group etc.), alkoxycarbonyl group (eg methoxycarbonyl group, ethoxycarbonyl group etc.), aryloxycarbonyl group (eg phenoxycarbonyl) Group).

Examples of the heterocyclic group include a pyridyl group, a benzimidazolyl group, a benzthiazolyl group, and a benzoxazolyl group. R ₇ is preferably a hydrogen atom.

  The polymerizable group referred to in the present invention means an unsaturated ethylene-based polymerizable group or a bifunctional polycondensable group, and preferably an unsaturated ethylene-based polymerizable group. Specific examples of the unsaturated ethylene polymerizable group include vinyl group, allyl group, acryloyl group, methacryloyl group, styryl group, acrylamide group, methacrylamide group, vinyl cyanide group, 2-cyanoacryloxy group, 1,2 -An epoxy group, a vinylbenzyl group, a vinyl ether group and the like can be mentioned, and a vinyl group, an acryloyl group, a methacryloyl group, an acrylamide group, and a methacrylamide group are preferable. Moreover, having a polymerizable group as a partial structure means that the polymerizable group is bonded directly or by a divalent or higher valent linking group, and the divalent or higher valent linking group is, for example, an alkylene group. (Eg, methylene, 1,2-ethylene, 1,3-propylene, 1,4-butylene, cyclohexane-1,4-diyl, etc.), alkenylene groups (eg, ethene-1,2-diyl, butadiene-1, 4-diyl, etc.), alkynylene groups (eg, ethyne-1,2-diyl, butane-1,3-diyne-1,4-diyl, etc.), linking groups derived from compounds containing at least one aromatic group (Eg, substituted or unsubstituted benzene, condensed polycyclic hydrocarbons, aromatic heterocycles, aromatic hydrocarbon ring assemblies, aromatic heterocycle assemblies, etc.), heteroatom linking groups (oxygen, sulfur, nitrogen, silicon Although such phosphorus atoms) are exemplified, preferably an alkylene group and a group linking a heteroatom. These linking groups may be further combined to form a composite group. The polymer derived from the ultraviolet absorbing monomer preferably has a weight average molecular weight of 2,000 to 30,000, more preferably 5,000 to 20,000.

  The weight average molecular weight of the ultraviolet absorbing polymer used in the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like. The polymerization temperature is usually from room temperature to 130 ° C, preferably from 50 ° C to 100 ° C.

  The UV-absorbing polymer used in the present invention may be a homopolymer of only an UV-absorbing monomer or a copolymer with other polymerizable monomer, but other polymerizable properties capable of copolymerization are also available. Examples of the monomer include a styrene derivative (for example, styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylnaphthalene, etc.), an acrylate derivative (for example, methyl acrylate, acrylic Ethyl acrylate, propyl acrylate, butyl acrylate, i-butyl acrylate, t-butyl acrylate, octyl acrylate, cyclohexyl acrylate, benzyl acrylate, etc.), methacrylate derivatives (eg, methyl methacrylate, methacrylic acid) Ethyl, propyl methacrylate, butyl methacrylate, I-butyl crylate, t-butyl methacrylate, octyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, etc.), alkyl vinyl ethers (eg, methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, etc.), alkyl vinyl esters (eg, vinyl formate) , Vinyl acetate, vinyl butyrate, vinyl caproate, vinyl stearate, etc.), crotonic acid, maleic acid, fumaric acid, itaconic acid, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, acrylamide, methacrylamide, etc. Is mentioned. Preferred are methyl acrylate, methyl methacrylate, and vinyl acetate.

  It is also preferred that the copolymer component other than the ultraviolet absorbing monomer in the polymer derived from the ultraviolet absorbing monomer contains at least one hydrophilic ethylenically unsaturated monomer.

  The hydrophilic ethylenically unsaturated monomer is not particularly limited as long as it is hydrophilic and has an unsaturated double bond polymerizable in the molecule. For example, unsaturated carboxylic acid such as acrylic acid or methacrylic acid. Or acrylic acid or methacrylic acid ester having a hydroxyl group or an ether bond (for example, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl acrylate, Hydroxypropyl, 2,3-dihydroxy-2-methylpropyl methacrylate, tetrahydrofurfuryl acrylate, 2-ethoxyethyl acrylate, diethylene glycol ethoxylate acrylate, 3-methoxybutyl acrylate, etc.), acrylamide, N, - dimethyl (meth) acrylamide, (N- substituted) (meth) acrylamide, N- vinylpyrrolidone, N- vinyloxazolidone and the like.

  As the hydrophilic ethylenically unsaturated monomer, (meth) acrylate having a hydroxyl group or a carboxyl group in the molecule is preferable, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, acrylic acid 2-hydroxypropyl is particularly preferred.

  These polymerizable monomers can be used alone or in combination of two or more to be copolymerized with the ultraviolet absorbing monomer.

  Although the polymerization method of the ultraviolet-absorbing copolymer used in the present invention is not particularly limited, conventionally known methods can be widely employed, and examples thereof include radical polymerization, anionic polymerization, and cationic polymerization. Examples of radical polymerization initiators include azo compounds and peroxides, and examples include azobisisobutyronitrile (AIBN), azobisisobutyric acid diester derivatives, benzoyl peroxide, and hydrogen peroxide. . The polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene and chlorobenzene, halogenated hydrocarbon solvents such as dichloroethane and chloroform, ether solvents such as tetrahydrofuran and dioxane, and amide solvents such as dimethylformamide. And alcohol solvents such as methanol, ester solvents such as methyl acetate and ethyl acetate, ketone solvents such as acetone, cyclohexanone and methyl ethyl ketone, and water solvents. Depending on the selection of the solvent, solution polymerization for polymerization in a homogeneous system, precipitation polymerization for precipitation of the produced polymer, emulsion polymerization for polymerization in a micelle state, and suspension polymerization for polymerization in a suspension state can also be performed. However, the ultraviolet-absorbing latex obtained by emulsion polymerization is not suitable for optical film applications.

  The use ratio of the above-mentioned UV-absorbing monomer, polymerizable monomer copolymerizable therewith and hydrophilic ethylenically unsaturated monomer is the compatibility of the obtained UV-absorbing copolymer polymer with other transparent polymers, It is appropriately selected in consideration of the influence on transparency and mechanical strength.

  The content of the ultraviolet absorbing monomer in the polymer derived from the ultraviolet absorbing monomer is preferably 1 to 70% by mass, and more preferably 5 to 60% by mass. When the content of the ultraviolet monomer in the ultraviolet absorbing polymer is less than 1% by mass, a large amount of the ultraviolet absorbing polymer must be used when trying to satisfy the desired ultraviolet absorbing performance. As a result, the transparency is lowered and the film strength is lowered. On the other hand, when the content of the ultraviolet monomer in the ultraviolet absorbing polymer exceeds 70% by mass, the compatibility with other polymers is lowered, so that a transparent optical film cannot be obtained. Moreover, the solubility with respect to a solvent becomes low, and the workability | operativity and productivity at the time of film preparation are inferior.

  In the present invention, the ultraviolet absorber contains a hydrophilic ethylenically unsaturated monomer. It is preferable that 5-50 mass% of hydrophilic ethylenically unsaturated monomers are contained in the said ultraviolet absorptive copolymer. When the content is 5% by mass or more, the compatibility is improved, and when the content is 50% by mass or less, the solubility in a solvent such as methylene chloride is improved. A more preferable content of the hydrophilic ethylenically unsaturated monomer is 10 to 25% by mass.

  In order to satisfy the preferable contents of the UV-absorbing monomer and the hydrophilic monomer, it is preferable to copolymerize an ethylenically unsaturated monomer having no hydrophilic group in the molecule in addition to both.

  Two or more kinds of UV-absorbing monomers and (non) hydrophilic ethylenically unsaturated monomers may be mixed and copolymerized.

  Hereinafter, representative examples of the ultraviolet absorbing monomer preferably used in the present invention are exemplified, but the invention is not limited thereto.

  The ultraviolet absorbent, ultraviolet absorbent monomer and intermediate thereof used in the present invention can be synthesized with reference to known literature. For example, U.S. Pat. Nos. 3,072,585, 3,159,646, 3,399,173, 3,761,272, 4,028,331, 5,683,861 No., European Patent No. 86,300,416, JP-A Nos. 63-227575, 63-185969, Polymer Bulletin. V. 20 (2), 169-176, and Chemical Abstracts V.I. 109, no. 191389 and the like can be synthesized.

  The ultraviolet absorbing polymer used in the present invention can be used in combination with another ultraviolet absorbing polymer or a low molecular weight ultraviolet absorber as required. However, other ultraviolet absorbing polymers are preferably used in small amounts because sufficient ultraviolet absorbing performance cannot be obtained or compatibility is not sufficient. In addition, low molecular weight ultraviolet absorbers cause foreign matter in bleed out and alkali saponification treatment, and are therefore preferably used in small amounts and most preferably not used.

  Examples of the low molecular weight ultraviolet absorber according to the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, and the like. I can do it.

  The method of adding the ultraviolet absorber and the ultraviolet absorbing polymer used in the present invention to the optical film may be added directly, but in-line addition with excellent productivity is preferred. In-line addition is a method in which an in-line mixer or the like is added to the dope composition after dissolving in advance in an organic solvent (for example, methanol, ethanol, methylene chloride, etc.).

The amount of the UV-absorbing polymer used in the present invention is not uniform depending on the type of compound, the conditions of use, etc., but is preferably 0.6 to 9.0 g per 1 m ^{2 of} optical film, and 1.2 to 6.0. Is more preferable, and 2.0 to 4.0 is particularly preferable.

  Furthermore, from the viewpoint of preventing liquid crystal deterioration, those having excellent ultraviolet absorption performance at a wavelength of 380 nm or less and low visible light absorption of 400 nm or more are preferable from the viewpoint of good liquid crystal display properties. In the present invention, the transmittance at a wavelength of 380 nm is particularly preferably 8% or less, more preferably 4% or less, and particularly preferably 1% or less.

(Polyhydric alcohol ester)
The polyhydric alcohol ester is composed of an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used in the present invention is represented by the following general formula (2).

Formula (2) R _1- (OH) _n
In the formula, R ₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the 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, pentaerythritol, dipentaerythritol and the like. Of these, trimethylolpropane and pentaerythritol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this invention, 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 preferable 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 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. The use of acetic acid is preferred because the compatibility with the cellulose ester is increased, and it is also preferred 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-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, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid. Examples of preferable alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and 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. Aromatic monocarboxylic acids possessed by them, or derivatives thereof. In particular, benzoic acid is preferred.

  The molecular weight of the polyhydric alcohol ester is preferably in the range of 300 to 1500, and more preferably in the range of 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 specific compound of a polyhydric alcohol ester is shown below.

  The content of the polyhydric alcohol ester according to the present invention is preferably 1 to 15% by mass, particularly preferably 3 to 10% by mass in the cellulose ester film.

(Ester plasticizer)
The ester plasticizer is not particularly limited, but an ester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. Although it does not specifically limit as a preferable ester plasticizer, For example, the aromatic terminal ester plasticizer represented by following General formula (3) is raised.

Formula (3) 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 (3), 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 ester 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 ester plasticizer of the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, and 1,3-butanediol. 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl -1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl , 3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Used as a mixture of the above. 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 of the present invention include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. One kind or a mixture of two or more kinds can be used.

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

  The ester plasticizer used in the present invention has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is preferably 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, the synthesis example of the aromatic terminal ester plasticizer which concerns on this invention is shown.

<Sample No. 1 (Aromatic terminal ester sample)>
A reaction vessel was charged with 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,2-propanediol, and 0.35 part of tetraisopropyl titanate as a catalyst, and a reflux condenser was attached while stirring in a nitrogen stream. Then, while refluxing excess monohydric alcohol, heating was continued at 130 to 250 ° C. until the acid value became 2 or less, and water produced was continuously removed. Subsequently, the distillate is removed under reduced pressure of 1.33 × 10 ⁴ Pa to finally 4.0 × 10 ² Pa or less at 200 to 230 ° C., and then filtered to obtain an aromatic terminal ester having the following properties: A plasticizer was obtained.

Acid value: 0.2
<Sample No. 2 (Aromatic terminal ester sample)>
Sample No. 4 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,3-propanediol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

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, 495 parts of 1,3-butanediol, and 0.40 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.

Acid value: 0.05
<Sample No. 4 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of terephthalic 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.

Acid value: 0.1
<Sample No. 5 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of terephthalic 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.

Acid value: 0.1
<Sample No. 6 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of terephthalic acid, 610 parts of benzoic acid, 495 parts of 1,3-butanediol, and 0.40 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.

Acid value: 0.05
<Sample No. 7 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of isophthalic acid, 610 parts of benzoic acid, 418 parts of 1,2-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.

Acid value: 0.1
<Sample No. 8 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of isophthalic 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.

Acid value: 0.1
<Sample No. 9 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of isophthalic acid, 610 parts of benzoic acid, 495 parts of 1,3-butanediol, and 0.40 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.

Acid value: 0.05
Specific examples of the aromatic terminal ester plasticizer are shown below, but the present invention is not limited thereto.

  The content of the aromatic terminal ester plasticizer according to the present invention is preferably 1 to 20% by mass, and particularly preferably 3 to 11% by mass in the cellulose ester film.

  The total content of the polyhydric alcohol ester and the aromatic terminal ester plasticizer according to the present invention is preferably 5 to 20% by mass, and particularly preferably 7 to 15% by mass in the cellulose ester film. .

  The present invention relates to a cellulose ester having a total acyl group substitution degree of 2.50 to 2.65, an ultraviolet absorbing monomer represented by the general formula (1), a hydrophilic ethylenically unsaturated monomer, and an ethylenically unsaturated group. A retardation film containing an ultraviolet-absorbing copolymer synthesized from a monomer and having a thickness of 30 to 60 μm.

  In order to obtain the retardation necessary for the retardation film even when the film is thinned, the hygroscopicity is increased, and further, the ultraviolet absorber is eluted by alkali saponification treatment, or the generation of foreign matter due to dissolution of the cellulose ester resin itself, In order to solve the deterioration of the polarizing plate using the retardation film under high temperature and high humidity conditions, in the present invention, the practical range of the total acyl group substitution degree is set as the above range, and the specific structure having a high degree of Use molecular UV absorbers. For this reason, the retardation film of the present invention preferably contains an ester plasticizer represented by the general formula (1), and further a polyhydric alcohol ester. These ester plasticizers have a large effect of improving hygroscopicity, and these ester plasticizers have little bleed out, so that retardation adjustment is easy.

  As described above, the present invention is a thin cellulose ester film of 30 to 60 μm. In addition to the above components, the cellulose ester film of the present invention may contain the following components, which will be described below. .

  The cellulose ester film according to the present invention may contain an antioxidant. For example, it may contain a peroxide decomposing agent, a radical chain inhibitor, a metal deactivator or an acid scavenger as described in JP-A-5-197073. The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose ester.

  In the present invention, the cellulose ester film preferably contains a fine particle matting agent. Examples of the fine particle matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, and baking. It is preferable to contain inorganic fine particles such as calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, and crosslinked polymer fine particles. Of these, silicon dioxide is preferable because it can reduce the haze of the film. The average particle size of the secondary particles of the fine particles is in the range of 0.01 to 1.0 μm, and the content is preferably 0.005 to 0.3% by mass with respect to the cellulose ester. In many cases, fine particles such as silicon dioxide are surface-treated with an organic material, but such a material is preferable because it can reduce the haze of the film. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes (particularly alkoxysilanes having a methyl group), silazane, siloxane and the like. The larger the average particle size of the fine particles, the greater the mat effect, and on the contrary, the smaller the average particle size, the better the transparency. Therefore, the average particle size of the preferred primary particles is 5 to 50 nm, more preferably 7 to 16 nm. It is. These fine particles are usually present as aggregates in the cellulose ester film, and it is preferable to form irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film. As the fine particles of silicon dioxide, AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600, etc. manufactured by Aerosil Co., Ltd. can be mentioned, preferably AEROSIL 200V, R972, R972V, R974, R202 and R812. Two or more of these matting agents may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, matting agents having different average particle sizes and materials, for example, AEROSIL 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9 to 0.1.

  Next, the manufacturing method of the cellulose-ester film of this invention is described.

  A method for preparing a cellulose ester dope in the present invention will be described. The dough is formed by dissolving the flaky cellulose ester in an organic solvent mainly containing a good solvent for the cellulose ester in a dissolving kettle while stirring. For dissolution, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, 9-95557 or 9-95538 There are various dissolution methods, such as a method performed by the cooling dissolution method as described in JP-A No. 11-21379, and a method performed at a high pressure as described in JP-A No. 11-21379. After dissolution, the dope is filtered with a filter medium, defoamed, and sent to the next process with a pump. The concentration of the cellulose ester in the dope is about 10 to 35% by mass. More preferably, it is 15-25 mass%. In order to contain the polymer useful in the present invention in the cellulose ester dope, the addition method such as addition after dissolving the polymer in an organic solvent in advance or direct addition to the cellulose ester dope can be carried out without limitation. In this case, the polymer is added so as not to become cloudy or phase-separated in the dope. The amount added is as described above.

  Examples of organic solvents as good solvents for cellulose esters include methyl acetate, ethyl acetate, amyl acetate, ethyl formate, acetone, cyclohexanone, methyl acetoacetate, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,4-dioxane, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3 , 3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, Nitroethane, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, methylene chloride, Etc. can be mentioned Romopuropan, methyl acetate, acetone, it is preferably used methylene chloride. However, non-chlorine organic solvents tend to be preferable due to recent environmental problems. In addition, it is preferable to use a lower alcohol such as methanol, ethanol or butanol in combination with these organic solvents because the solubility of the cellulose ester in the organic solvent can be improved and the dope viscosity can be reduced. In particular, ethanol having a low boiling point and low toxicity is preferred. The organic solvent used for the dope according to the present invention is preferably used by mixing a good solvent and a poor solvent of cellulose ester from the viewpoint of production efficiency, and the preferable range of the mixing ratio of the good solvent and the poor solvent is good. The solvent is 70 to 98% by mass, and the poor solvent is 2 to 30% by mass. With the good solvent and the poor solvent used in the present invention, those that dissolve the cellulose ester used alone are defined as good solvents, and those that do not dissolve alone are defined as poor solvents. Although it does not specifically limit as a poor solvent used for dope concerning this invention, For example, methanol, ethanol, n-butanol, cyclohexane, acetone, cyclohexanone etc. can be used preferably. For the ester plasticizer useful in the present invention, the organic solvent is preferably selected using a good solvent for cellulose ester. As described above, when using a low molecular plasticizer, it can be carried out by a normal addition method, either directly added into the dope, or dissolved in an organic solvent in advance and poured into the dope. Good.

  In the present invention, when various additives as described above are added to the cellulose ester dope, the cellulose ester dope and various additives can be added in-line to a solution in which a small amount of cellulose ester is dissolved and mixed. preferable. For example, it is preferable to use an in-line mixer such as a static mixer SWJ (Toray static type in-pipe mixer Hi-Mixer) (manufactured by Toray Engineering). When using an in-line mixer, it is preferable to apply it to a dope in which cellulose ester is concentrated and dissolved under high pressure. The type of the pressure vessel is not particularly limited and can withstand a predetermined pressure, and heated and stirred under pressure. If you can.

In the present invention, the cellulose ester dope must be filtered to remove foreign matters, particularly foreign matters that can be recognized as images in a liquid crystal image display device. It can be said that the quality of the polarizing plate protective film is determined by this filtration. Filter media used for filtration preferably have a low absolute filtration accuracy, but if the absolute filtration accuracy is too small, the filter media is likely to be clogged, and the filter media must be frequently replaced, reducing productivity. There is a problem. For this reason, the cellulose ester-doped filter medium of the present invention preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and in the range of 0.003 to 0.006 mm. Further preferred. There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, filter fibers made of plastic fibers such as polypropylene and Teflon (registered trademark) and metal filter media such as stainless steel fibers can cause the fibers to fall off. Less preferred. Filtration of the cellulose ester dope of the present invention can be carried out by a usual method, but the method of filtration while heating under pressure at a temperature not lower than the boiling point of the solvent at a normal pressure and in a range where the solvent does not boil is used before and after the filtration. The increase in differential pressure (hereinafter sometimes referred to as filtration pressure) is small and preferable. A preferred temperature range 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 × 10 ⁶ Pa or less, more preferably 1.2 × 10 ⁶ Pa or less, and further preferably 1.0 × 10 ⁶ Pa or less. If the cellulose of the raw material contains an acyl group unsubstituted or low-substituted cellulose ester, a foreign matter failure (hereinafter sometimes referred to as a bright spot) may occur. When a cellulose ester film is placed between two polarizing plates in a crossed state (crossed nicols), light is irradiated from one side and observed with an optical microscope (50 times) from the opposite side, a normal cellulose ester film is obtained. If there is, the light is blocked and you can't see anything black, but if there is a foreign object, the light leaks out and appears to shine like a spot. The larger the diameter of the bright spot, the greater the actual harm in the case of a liquid crystal image display device, preferably 50 μm or less, more preferably 10 μm or less, and further preferably 8 μm or less. The diameter of the bright spot means a diameter measured by approximating the bright spot to a perfect circle. There are no practical problems as long as the bright spot has a diameter of 400 / cm ² or less, but 300 / cm ² or less is preferable, and 200 / cm ² or less is more preferable. In order to reduce the number and size of such bright spots, it is necessary to sufficiently filter fine foreign matters. In addition, as described in JP-A-2000-137115, a method of re-adding a pulverized product of a cellulose ester film once formed into a dope and using it as a raw material for cellulose ester and its additive is a bright spot. Since it can reduce, it can use preferably.

  Next, the process of casting the cellulose ester dope on the metal support, the drying process on the metal support, and the peeling process of peeling the web from the metal support will be described. The metal support is an endless metal belt or a rotating metal drum that moves indefinitely, and its surface is a mirror surface. The casting step is a step of feeding the dope as described above to a pressure die through a pressure type quantitative gear pump and casting the dope from the pressure die onto the metal support at the casting position. Other casting methods include a doctor blade method in which the film thickness of the cast dope film is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse-rotating roll, but the slit shape of the die part is adjusted. A pressure die that is easy to make uniform in film thickness is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. In order to adjust the film thickness, it is preferable to control the dope concentration, the pumped liquid amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the metal support, etc. so as to obtain a desired thickness.

  The drying process on the metal support is a process in which the web (the dope film after casting on the metal support is referred to as the web) is heated on the support to evaporate the solvent. In order to evaporate the solvent, there are a method in which heated air is blown from the web side and the back side of the support, a method in which heat is transferred from the back side of the support by a heated liquid, a method in which heat is transferred from the front and back by radiant heat, and the like. A method of combining them is also preferable. Moreover, if the film thickness of a web is thin, drying will be quick. The temperature of the metal support may be the same or different depending on the position.

  In the drying method on the metal support suitable for the present invention, for example, the metal support is preferably cast at a temperature of 0 to 40 ° C., preferably 5 to 30 ° C. The drying air applied to the web is preferably about 30 to 45 ° C, but is not limited thereto.

  The peeling step is a step of evaporating the organic solvent on the metal support and peeling the web before the metal support goes around, and then the web is sent to the drying step. The position at which the web is peeled from the metal support is called the peeling point, and the roll that helps the peeling is called the peeling roll. Although it depends on the thickness of the web, if the residual solvent amount of the web at the peeling point (the following formula) is too large, it will be difficult to peel, or conversely if it is peeled off after sufficiently drying on the support, May be peeled off. Usually, the web is peeled at a residual solvent amount of 20 to 150% by mass. In the present invention, the preferable amount of residual solvent for peeling is 20 to 40% by mass or 60 to 120% by mass, and particularly preferably 20 to 30% by mass or 70 to 115% by mass. As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the residual solvent amount is as large as possible), there is a gel casting method (gel casting) that can be peeled even when the residual solvent amount is large. As the method, there are a method of adding a poor solvent for the cellulose ester in the dope and casting the dope and then gelling, a method of reducing the temperature of the support and gelling. There is also a method of adding a metal salt in the dope. By gelling on the support and strengthening the film, it is possible to speed up the peeling and increase the film forming speed. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, or slippage and vertical stripes due to peeling tension will easily occur, and the amount of residual solvent is determined by the balance between economic speed and quality. It is done.

  The amount of residual solvent used in the present invention can be expressed by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web at any point, and N is the mass when M is dried at 110 ° C. for 3 hours.

  Moreover, in the drying process of the cellulose ester film, it is preferable to further dry the film peeled off from the support, and to make the residual solvent amount 2.0% by mass or less, more preferably 1.0% by mass, and still more preferably. , 0.5% by mass or less.

  In the web drying process, a roll drying apparatus in which rolls are arranged in a staggered manner, and a method of drying while conveying the web with a tenter drying apparatus that holds the width of the web with clips and holds the width or extends slightly in the width direction are adopted. In the present invention, it is particularly preferable because the humidity stability of the optical performance is improved by maintaining the width or stretching in an arbitrary process after peeling from the support of the tenter drying apparatus and in an arbitrary amount of residual solvent. The means for drying the web is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably increased stepwise in the range of 40 to 150 ° C, more preferably in the range of 50 to 140 ° C.

  The stretching operation may be performed in multiple stages, and it is preferable to perform biaxial stretching in the casting direction and the width direction. Also, when biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible.

  Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferred draw ratio of simultaneous biaxial stretching is x1.05 to x1.5 times in the width direction and x0.8 to x1.3 times in the longitudinal direction (casting direction), particularly x1 in the width direction. 0.1 to x1.5 times, and preferably x0.8 to x0.99 times in the longitudinal direction. Particularly preferably, it is x1.1 to x1.4 times in the width direction and x0.9 to x0.99 times in the longitudinal direction.

  The thinner the film thickness of the cellulose ester film is the solvent (dope production) used in the production, for example, the greater the effect as a weight reducing means such as residual methylene chloride.

  In addition, it is preferable that the cellulose ester film is thinner because the finished polarizing plate is thinner and the liquid crystal display can be easily thinned. However, if it is too thin, the moisture permeability, tear strength, and the like deteriorate. Moreover, since retardation as a retardation film is difficult to obtain, the film thickness of the cellulose ester film satisfying these is in the range of 30 to 60 μm.

  The width of the cellulose ester film is preferably 1.4 m or more, and preferably in the range of 1.4 m to 4 m for a large-sized liquid crystal display device from the viewpoint of productivity.

  The retardation film comprising the cellulose ester of the present invention is preferably used for a liquid crystal display member because of its high moisture permeability and dimensional stability. A liquid crystal display member is a member used in a liquid crystal display device. For example, a polarizing plate, a polarizing plate protective film, a retardation plate, a reflective plate, a viewing angle improving film, an antiglare film, an antireflective film, and an antistatic material. A film etc. are mentioned. Among the above description, it is preferable to use for the retardation film for polarizing plates.

In order to form a polarizing plate using the retardation film of the present invention, the retardation film of the present invention having a film thickness of 30 to 60 μm (also serving as a polarizing plate protective film) and another polarizing plate protective film A are used. It is preferable that the polarizer described later is sandwiched between these. In the production of the polarizing plate, the polarizing plate protective film A bonded to the opposite side of the retardation film of the present invention is also preferably 30 to 60 μm in thickness from the viewpoint of curling prevention. As the polarizing plate protective film A bonded to the opposite side, a cellulose ester film is preferable, and the total acyl group substitution degree is larger than the cellulose ester used in the retardation film according to the present invention, that is, 2.65. A cellulose ester film prepared using a cellulose ester having a high degree of total acyl group substitution exceeding is preferred.

  The cellulose ester film used as the polarizing plate protective film A is various plasticizers (phosphate ester type, ethylene glycol ester type plasticizer, as well as the cellulose ester film according to the present invention suitable as the retardation film. Glycerin ester plasticizers, etc.), UV absorbers, UV-absorbing copolymer polymers (polymer UV absorbers or polymer UV agents), antioxidants, etc. It is formed by casting and stretching in the same manner as the cellulose film.

(Polarizer)
The polarizing plate was formed by subjecting the cellulose ester film according to the present invention to a surface saponification treatment with a 2.5 mol / l sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, washing with water for 3 minutes and drying, separately, for example, A polarizing film prepared by immersing 120 parts by weight of polyvinyl alcohol having a thickness of 120 μm in 100 parts by weight of an aqueous solution containing 1 part by weight of iodine and 4 parts by weight of boric acid and stretching in a vertical direction at 50 ° C. is prepared as a polarizer. The polarizing plate may be prepared by laminating the cellulose ester film subjected to the surface saponification treatment with a 5% by mass aqueous solution of a completely saponified polyvinyl alcohol as an adhesive.

  The content of iodine in the polyvinyl alcohol film (stretched film) is usually adjusted to about 0.5 to 5% by mass, preferably 1 to 3% by mass so that the polarizer exhibits a good degree of polarization. It is preferable to do this. The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method can be adopted, but it is preferable to use a dry stretching method. Examples of the stretching means of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. Stretching can also be performed in multiple stages. In the stretching means, the unstretched film is usually heated. Usually, an unstretched film having a thickness of about 30 to 150 μm is used. The stretch ratio of the stretched film can be appropriately set according to the purpose, but the stretch ratio is desirably about 2 to 7 times, preferably 3 to 6.5 times, and more preferably 3.5 to 6 times. The thickness of the stretched film is preferably about 5 to 40 μm. The iodine dyeing treatment is generally performed by immersing a polyvinyl alcohol film in an iodine solution. In the case where an iodine aqueous solution is used as the iodine solution, an aqueous solution containing iodine ions with, for example, potassium iodide or the like is used as iodine and a dissolution aid. The iodine concentration is about 0.01 to 0.5% by mass, preferably 0.02 to 0.4% by mass, the potassium iodide concentration is about 0.01 to 10% by mass, and further 0.02 to 8% by mass. % Is preferably used.

  As described above, the polarizer, which is a main component of the polarizing plate, is an element that allows only light having a plane of polarization in a certain direction to pass through. A typical currently known polarizer is a polyvinyl alcohol-based material as described above. This is a polarizing film, which includes a polyvinyl alcohol film dyed with iodine and a dichroic dye dyed.

  In this invention, it is preferable to use the polarizer which is the film thickness of 5-20 micrometers using the ethylene modified polyvinyl alcohol which has a thinner film thickness besides the said polyvinyl alcohol-type film.

  Ethylene-modified polyvinyl alcohol is formed from ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol%, and has a hot water cutting temperature of 66. It is preferable to be produced from an ethylene-modified polyvinyl alcohol film having a temperature of ˜73 ° C. The difference in hot water cutting temperature between two points 5 cm away in the TD direction of the film is more preferably 1 ° C. or less to reduce color spots, and two points 1 cm away in the TD direction of the film. In order to reduce color spots, it is more preferable that the difference in the hot water cutting temperature is 0.5 ° C. or less. Furthermore, it is especially preferable that the thickness of the film before stretching is 10 to 50 μm in order to reduce color spots.

  As the ethylene-modified polyvinyl alcohol (ethylene-modified PVA) used in the present invention, an ethylene-vinyl ester polymer obtained by copolymerizing ethylene and a vinyl ester monomer is saponified, and the vinyl ester unit is converted into a vinyl alcohol unit. Can be used. Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Of these, vinyl acetate is preferably used.

  The ethylene unit content (ethylene copolymerization amount) in the ethylene-modified PVA is 1 to 4 mol%, preferably 1.5 to 3 mol%, more preferably 2 to 3 mol%.

  Such vinyl ester monomers are copolymerized with other monomers such as propylene, 1-butene, isobutene, etc., and acrylic acid and its salts; methyl acrylate, ethyl acrylate, n-propyl acrylate, etc. Also good.

  The polymerization degree of the ethylene-modified PVA constituting the polarizer is 2000 to 4000, preferably 2200 to 3500, particularly preferably 2500 to 3000, from the viewpoint of polarization performance and durability. When the degree of polymerization of ethylene-modified PVA is less than 2000, the polarizing performance and durability performance of the polarizing film are lowered, which is not preferable. Moreover, when the polymerization degree is 4000 or less, it is preferable that the color spots of the polarizer hardly occur.

  The degree of polymerization of ethylene-modified PVA is the weight average degree of polymerization determined from GPC measurement. This weight average degree of polymerization is a value obtained by performing GPC measurement at 40 ° C. using hexafluoroisopropanol (HFIP) in which 20 mmol / liter sodium trifluoroacetate is added to the mobile phase using monodispersed PMMA as a standard. is there.

  The saponification degree of the ethylene-modified PVA constituting the polarizer is 99.0 to 99.99 mol% from the viewpoint of the polarization performance and durability of the polarizing film, more preferably 99.9 to 99.99 mol%, Particularly preferred is .95 to 99.99 mol%.

  As a method for producing an ethylene-modified PVA film, a film forming method by a melt extrusion method using water-containing ethylene-modified PVA and a casting film-forming method using an ethylene-modified PVA solution in which ethylene-modified PVA is dissolved in a solvent are preferable. . The obtained ethylene-modified PVA film is subjected to drying and heat treatment as necessary.

  Examples of the solvent for dissolving the ethylene-modified PVA used in producing the ethylene-modified PVA film include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, and triethylene. Glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, glycerin, water and the like can be mentioned, and one or more of these can be used. Among these, dimethyl sulfoxide, water, or a mixed solvent of glycerin and water is preferably used.

  The ratio of ethylene-modified PVA in ethylene-modified PVA containing ethylene-modified PVA solution or water varies depending on the degree of polymerization of ethylene-modified PVA, but is preferably 25 to 60% by mass and most preferably 35 to 50% by mass. . Further, this ethylene-modified PVA solution or ethylene-modified PVA containing water may contain a plasticizer, a surfactant, a dichroic dye, or the like as necessary.

  When producing an ethylene-modified PVA film, it is preferable to add a polyhydric alcohol such as 1 to 30 parts by mass, ethylene glycol, or glycerin as a plasticizer with respect to 100 parts by mass of the ethylene-modified PVA.

  The ethylene-modified PVA film used for the production of the polarizer preferably has a thickness of 10 to 50 μm, and more preferably 20 to 40 μm. If the thickness is less than 10 μm, the film strength is too low to perform uniform stretching, and color spots of the polarizing film are likely to occur. When the thickness exceeds 50 μm, when a polarizing film is produced by uniaxially stretching an ethylene-modified PVA film, a thickness change due to neck-in at the end tends to occur, and color spots on the polarizing film are easily emphasized.

  In order to produce a polarizing film from an ethylene-modified PVA film, for example, the ethylene-modified PVA film may be dyed, uniaxially stretched, fixed, and dried, and further subjected to heat treatment as necessary. There is no particular limitation on the order of operations of the fixed processing. Moreover, you may perform uniaxial stretching twice or more.

  Dyeing can be performed before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. As a dye used for dyeing, iodine-potassium iodide, a dichroic dye, or the like can be used. Usually, the dyeing is generally performed by immersing the film in a solution containing the dye.

  Uniaxial stretching can be performed by wet stretching or dry heat stretching using warm water such as boric acid aqueous solution (in a solution containing the dye or in a fixing treatment bath described later) or an ethylene-modified PVA film after water absorption. Can be done in air. The stretching temperature is not particularly limited, but is preferably 30 to 90 ° C. when the ethylene-modified PVA film is stretched (wet stretching) in warm water, and 50 to 180 ° C. is suitable for dry heat stretching. Further, the stretching ratio of uniaxial stretching (the total stretching ratio in the case of multi-stage uniaxial stretching) is preferably 4 times or more, and most preferably 5 times or more from the viewpoint of the polarizing performance of the polarizing film. The upper limit of the stretching ratio is not particularly limited, but it is preferably 8 times or less because uniform stretching is easily obtained. 2-20 micrometers is preferable, as for the thickness of the film after extending | stretching, 5-20 micrometers is more preferable, and 5-15 micrometers is especially preferable.

  Fixing treatment is often performed for the purpose of strengthening the adsorption of the dye to the ethylene-modified PVA film. Usually, boric acid and / or boron compounds are added to the treatment bath used for the fixing treatment. Moreover, you may add an iodine compound in a processing bath as needed.

  It is preferable to perform the drying process of the obtained polarizer at 30-150 degreeC, and it is more preferable to carry out at 50-150 degreeC.

  The polarizer obtained as described above is usually used as a polarizing plate by attaching a protective film optically transparent and having mechanical strength on both sides or one side. In addition, examples of the adhesive for bonding include a PVA-based adhesive and a urethane-based adhesive. Among them, a PVA-based adhesive is preferably used.

  The polarizing plate of the present invention comprises a polarizer sandwiched between the polarizing plate protective film A having a thickness of 30 to 60 μm and the retardation film of the present invention having a thickness of 30 to 60 μm (also serving as a polarizing plate protective film). It is preferable that it is a polarizing plate with a film thickness of 80-160 micrometers.

  In laminating the polarizer and the retardation film for polarizing plate of the present invention or the protective film for polarizing plate (both cellulose ester films), the surface of the cellulose ester film must be subjected to an alkali saponification treatment in order to ensure adhesion. However, the retardation film of the present invention does not generate foreign matter due to elution of components even in alkali saponification treatment.

  The retardation film (stretched cellulose ester film) of the present invention has a retardation value Ro defined by the following formula (I) of 30 to 100 nm and a retardation value Rt defined by the following formula (II) of 100 to 100. It is characterized by being in the range of 300 nm.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
In the formula, nx is the refractive index in the direction with the largest refractive index in the film plane, ny is the refractive index in the film plane in the direction perpendicular to nx, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film. (Nm) respectively.

  By setting the retardation value within the above range, the optical performance as a retardation film for a polarizing plate can be sufficiently satisfied.

  The retardation values Ro and Rt can be measured using an automatic birefringence meter. For example, the wavelength can be obtained at 590 nm in an environment of 23 ° C. and 55% RH using KOBRA-21ADH (Oji Scientific Instruments).

  The polarizing plate protective film of the present invention preferably has a light transmittance (of visible light) of 90% or more, more preferably 95% or more, and further preferably 94% or more even after saponification treatment. The haze is preferably less than 1%, more preferably less than 0.5%, and further preferably less than 0.1%. In particular, 0% is most preferable.

(Display device)
By incorporating the polarizing plate of the present invention into a display device, the display device of the present invention having various visibility can be manufactured. The cellulose stealth film of the present invention is a reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type, etc. Preferably used. In particular, it is suitable for a VA liquid crystal display device.

  In particular, the VA type liquid crystal display device with a large screen of 30 or more screens has the effect of improving the humidity stability of the optical performance, reducing color unevenness and wavy unevenness, and preventing eyestrain even during long-time viewing. .

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

(Synthesis example of polymer UV agent P-1) Comparative example 2 (2'-hydroxy-5'-t-butyl-phenyl) -5-carboxylic acid- (2-methacryloyloxy) ethyl ester-2H-benzotriazole (exemplified) Compound MUV-19) was synthesized according to the method described below.

  20.0 g 3-nitro-4-amino-benzoic acid was dissolved in 160 ml water and 43 ml concentrated hydrochloric acid was added. After adding 8.0 g of sodium nitrite dissolved in 20 ml of water at 0 ° C., the mixture was stirred at 0 ° C. for 2 hours. To this solution, 17.3 g of 4-t-butylphenol was added dropwise at 0 ° C. in a solution of 50 ml of water and 100 ml of ethanol while keeping the liquidity alkaline with potassium carbonate. The solution was stirred for 1 hour while maintaining at 0 ° C., and further for 1 hour at room temperature. The reaction solution was acidified with hydrochloric acid, and the resulting precipitate was filtered and washed thoroughly with water.

  The filtered precipitate was dissolved in 500 ml of 1 mol / L NaOH aqueous solution, 35 g of zinc powder was added, and 110 g of 40% NaOH aqueous solution was added dropwise. After dropping, the mixture was stirred for about 2 hours, filtered, washed with water, and the filtrate was neutralized with hydrochloric acid to neutral. The deposited precipitate is filtered, washed with water, dried and then recrystallized with a mixed solvent of ethyl acetate and acetone to give 2 (2'-hydroxy-5'-t-butyl-phenyl) -5-carboxylic acid-2H. -Benzotriazole was obtained.

  Then 10.0 g of 2 (2′-hydroxy-5′-t-butyl-phenyl) -5-carboxylic acid-2H-benzotriazole and 0.1 g of hydroquinone, 4.6 g of 2-hydroxyethyl methacrylate, 0 .5 g of p-toluenesulfonic acid is added to 100 ml of toluene, and heated and perfused for 10 hours in a reaction vessel equipped with an ester tube. The reaction solution is poured into water, and the precipitated crystals are filtered, washed with water, dried, and recrystallized with ethyl acetate to give 2 (2'-hydroxy-5'-t-butyl-phenyl) which is the exemplified compound MUV-19. ) -5-carboxylic acid- (2-methacryloyloxy) ethyl ester-2H-benzotriazole was obtained.

  Next, a copolymer of 2 (2'-hydroxy-5'-t-butyl-phenyl) -5-carboxylic acid- (2-methacryloyloxy) ethyl ester-2H-benzotriazole and methyl methacrylate (polymer UV Agent P-1) was synthesized according to the method described below.

  To 80 ml of tetrahydrofuran, 4.0 g of 2 (2′-hydroxy-5′-t-butyl-phenyl) -5-carboxylic acid- (2-methacryloyloxy) ethyl ester-2H-benzotriazole synthesized in Synthesis Example 3 above. And 6.0 g of methyl methacrylate were added followed by 1.14 g of azoisobutyronitrile. The mixture was heated to reflux for 9 hours under a nitrogen atmosphere. Tetrahydrofuran was distilled off under reduced pressure, then redissolved in 20 ml of tetrahydrofuran and added dropwise to a large excess of methanol. The deposited precipitate was collected by filtration and dried in vacuo at 40 ° C. to obtain 9.1 g of a polymer UV agent P-1 which was a gray white powdery polymer. This copolymer was confirmed to have a number average molecular weight of 4500 by GPC analysis based on standard polystyrene. Further, from the NMR spectrum and UV spectrum, the above copolymer was found to be 2 (2′-hydroxy-5′-t-butyl-phenyl) -5-carboxylic acid- (2-methacryloyloxy) ethyl ester-2H-benzotriazole. And a copolymer of methyl methacrylate. The composition of the polymer is approximately 2 (2′-hydroxy-5′-t-butyl-phenyl) -5-carboxylic acid- (2-methacryloyloxy) ethyl ester-2H-benzotriazole: methyl methacrylate = 40: 60.

(Synthesis example of polymer UV agent P-2) Examples In the above-described synthesis process of polymer UV agent P-1, instead of 6.0 g of methyl methacrylate, 5.3 g of methyl methacrylate and 0.7 g of methacrylic acid were used. Polymer UV agent P-2 was synthesized in the same manner except that hydroxyethyl acid was used. The number average molecular weight was 4500. Further, the composition of the polymer is substantially 2 (2′-hydroxy-5′-t-butyl-phenyl) -5-carboxylic acid- (2-methacryloyloxy) ethyl ester-2H-benzotriazole: methyl methacrylate: The hydroxyethyl methacrylate was 40: 53: 7.

(Synthesis Example of Polymer UV Agent P-3) Example Polymer UV Agent P- 2 except that methyl methacrylate 4.5 g and hydroxyethyl methacrylate 1.5 g of polymer UV agent P-2 were used. 3 was produced. The finished composition ratio was 40:45:15.

[Preparation of transparent support A]
A cellulose ester solution was prepared using the cellulose ester, additives, fine particles, and solvent described in Tables 1 and 2 so as to have a dope composition as shown in Table 3.

  That is, the solvent was put into an airtight container, the remaining materials were put in order while stirring, and completely dissolved and mixed while heating and stirring. The fine particles were added dispersed in a part of the solvent. The solution was lowered to the temperature at which the solution was cast, allowed to stand, and subjected to a defoaming operation. Filtration using 244 gave each cellulose ester solution.

  Next, the cellulose ester solution whose temperature was adjusted to 33 ° C. was fed to a die and uniformly cast from a die slit onto a stainless steel belt. The cast part of the stainless steel belt was heated from the back with hot water of 37 ° C. After casting, the dope film on the metal support (which will be referred to as the web after casting on the stainless steel belt) is dried by applying hot air of 44 ° C., and the residual solvent amount during peeling is 80% by mass. Then, it is stretched so as to have a longitudinal stretching ratio of 1.05 times by applying tension at the time of peeling, and then the web end is gripped by a tenter so that the stretching ratio is 1.30 times in the width direction. Stretched. After stretching, the width is maintained for several seconds, and after the tension in the width direction is relaxed, the width is released, and further conveyed for 20 minutes in the third drying zone set at 110 ° C., and dried. Then, cellulose ester film samples 1 to 28 having a film thickness of 40 μm having a width of 1.5 m and a knurling of 1.5 cm in width and 8 μm in height were produced.

  About each produced cellulose-ester film, it used to summarize in Table 3 about the used cellulose ester, an additive, microparticles | fine-particles, a solvent. In addition, Table 4 shows the results of measurement according to the following evaluation methods.

"Evaluation methods"
(Haze)
Three film samples were superposed and measured according to ASTM-D1003-52 using T-2600DA manufactured by Tokyo Denshoku Industries Co., Ltd.

(Bleed out)
Each film sample was allowed to stand for 1000 hours in a high-temperature and high-humidity atmosphere at 80 ° C. and 90% RH, and then bleed-out was evaluated.

  The presence or absence of bleed out was evaluated by observing the surface of the film.

◎ ・ ・ ・ No bleed-out on the film surface ○ ・ ・ ・ Partial bleed-out is faint on the film surface △ ・ ・ ・ Full bleed-out is faint on the film surface × ・ ・ ・ Film surface Clearly shows full bleed out (Rt, Ro measurement)
Rt (nm) and Ro (nm) of each sample conditioned for 12 hours or more in an environment of 23 ° C. and 55% RH were measured. For the measurement, an automatic birefringence meter, KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.) was used, and the measurement was performed in an environment of 23 ° C. and 55% RH and at a wavelength of 590 nm.

(Rt humidity change)
Measure the Rt of the sample conditioned for 12 hours or more in an environment of 23 ° C. and 20% RH, and then measure the Rt of the sample conditioned for 12 hours or more in an environment of 23 ° C. and 80% RH. Calculated (%).

(Dimensional stability)
A cross-shaped mark is attached to two locations (MD direction and long direction) on the surface of the cellulose ester film sample, heat treatment (conditions: 80 ° C., 90% RH, 200 hours) is performed, and the distance between the marks using a factory microscope Was measured. The dimensional change rate was calculated by the following formula, assuming that the distance before the heat treatment is a1 and the distance after the heat treatment is a2.
Dimensional change rate (%) = (a1-a2) / a1 × 100
(Residual amount of methylene chloride)
The amount of residual methylene chloride can be measured by gas chromatography connected with a headspace sampler. In the present invention, gas chromatography 5890 type SERISII manufactured by Hewlett-Packard Company and headspace sampler HP7694 type were used, and the measurement was performed under the following measurement conditions.

Headspace sampler heating conditions: 120 ° C, 20 minutes GC introduction temperature: 150 ° C
Temperature rise: 40 ° C., hold for 5 minutes, then up to 100 ° C. (8 ° C./min) Column: DB-WAX manufactured by J & W (inner diameter 0.32 mm, length 30 m)
In the present invention, the amount of residual methylene chloride is defined by the following formula.
Residual methylene chloride amount (%) = (mass methylene chloride content in film) / (film mass after heat treatment) × 100
The heat treatment for measuring the amount of residual methylene chloride means that the film after measurement by gas chromatography is further heat-treated at 115 ° C. for 1 hour.

  Moreover, the polarizing plate was produced according to the following method, and also the following items were evaluated.

<Production of polarizing plate>
(Preparation of polarizing plate protective film A)
<Fine particle dispersion>
Fine particles (Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.)) 11 parts by mass Ethanol 89 parts by mass or more was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
The following cellulose ester was added to a dissolution tank containing methylene chloride, and heated to completely dissolve, then, this was added to Azumi Filter Paper No. Filtered using 244. The fine particle dispersion was slowly added thereto while sufficiently stirring the filtered cellulose ester solution. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.
Methylene chloride 99 parts by mass cellulose ester (cellulose triacetate; acetyl group substitution degree 2.9)
4 mass parts fine particle dispersion 11 mass parts The dope liquid of the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. The cellulose ester was added to the pressure dissolution tank containing the solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. A dope solution was prepared by filtration using 244.

<Dope composition>
Methylene chloride 440 parts by mass Ethanol 40 parts by mass Cellulose ester (cellulose triacetate; acetyl group substitution degree 2.9)
100 parts by mass plasticizer (aromatic terminal ester sample No. 1) 5.5 parts by mass plasticizer (trimethylolpropane tribenzoate) 5.5 parts by mass UV absorber (polymer UV agent P-1) 3 parts by mass Dope In addition to 100 parts by mass of the liquid and 2 parts by mass of the fine particle additive liquid, the mixture is sufficiently mixed with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then a belt casting apparatus is used to measure a width of 2 m. It was cast uniformly on a stainless steel band support. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. When peeling, the film is stretched so that the longitudinal (MD) stretch ratio is 1.1 times, and then both ends of the web are gripped by a tenter, and the stretch ratio in the width (TD) direction is 1.1. It extended | stretched so that it might become double. The residual solvent at the start of stretching was 30%. After stretching, hold for several seconds while maintaining its width, release the width holding after relaxing the tension in the width direction, further carry for 30 minutes in the third drying zone set at 125 ° C., and perform drying, A cellulose ester film A, which is a polarizing plate protective film A having a width of 1.5 m, a knurling having a width of 1 cm and a height of 8 μm at the end and a film thickness of 40 μm, was produced.

(Preparation of polarizing plate)
A 120 μm thick polyvinyl alcohol film was immersed in 100 kg of an aqueous solution containing 1 kg of iodine and 4 kg of boric acid and stretched 6 times at 50 ° C. to form a polarizing film. Using the polarizing film as a polarizer, the cellulose ester film samples 1 to 28 subjected to the following alkali saponification treatment on both sides are used as one polarizing plate protective film, and the cellulose ester is used as the other polarizing plate protective film. Using the film A, a polarizing plate was prepared by laminating the polarizer and the polarizer using a completely saponified polyvinyl alcohol 5% aqueous solution as an adhesive so as to sandwich the polarizer between the two.

<Alkali saponification treatment>
Saponification step 2N-NaOH 50 ° C. 90 seconds Water washing step Water 30 ° C. 45 seconds Neutralization step 10% HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 45 seconds Saponification, water washing, neutralization, water washing under the above conditions And then dried at 80 ° C.

  The following evaluation was performed about each produced polarizing plate.

(Polarizer degradation)
For the polarizing plate produced by the above method, first, the parallel transmittance and the direct transmittance were measured, and the degree of polarization was calculated according to the following formula. Thereafter, each polarizing plate was subjected to forced degradation for 1000 hours at 60 ° C. and 90%, and then the parallel transmittance and the direct transmittance were measured again, and the degree of polarization was calculated according to the following formula. The amount of change in polarization degree was determined by the following formula.

Polarization degree P = ((H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )) ^1/2 × 100
Polarization degree change = P ₀ −P ₁₀₀₀
H ₀ : Parallel transmittance H ₉₀ : Direct transmittance P ₀ : Polarization degree before forced deterioration P ₁₀₀₀ : Polarization degree after forced degradation 1000 hours ◎: Polarization degree change rate of less than 10% ○: Polarization degree change rate of 10% or more Less than 25% x: Polarization degree change rate of 25% or more.

(Saponification liquid contamination)
Saponification process 2N-NaOH 50 ° C. 90 seconds Water washing process Water 30 ° C. 45 seconds Neutralization process 10% HCl 30 ° C. 45 seconds Water washing process Water 30 ° C. 45 seconds Saponification of cellulose triacetate base under the above conditions -Performed in order of water washing. When a cellulose acetate base of 1 m ² per liter was treated, the treatment liquid of the saponification step was sampled in a glass container, and the degree of dirt was visually divided into the following ranks and evaluated. × Level is a level that requires liquid change because suspended matter adheres to the film and breaks down.

  A: Level at which almost no dirt is seen.

  ○: The liquid is cloudy, but the suspended matter is not visible.

  X: Level at which the liquid is extremely turbid and many floating substances are visible.

  From the results of Tables 3 and 4, the cellulose ester film according to the present invention has both saponification solution contamination (foreign matter generation) and less polarizer deterioration when used as a polarizing plate, and less haze, bleedout, etc. It can be seen that there is little change in humidity.

Example 2
<Production of polarizing plate>
First, a polarizer was produced as follows.

  A polarizer A using the following ethylene-modified PVA film was produced.

<Polarizer A: Ethylene-modified PVA film>
100 parts by mass of ethylene-modified PVA having an ethylene unit content of 2.1 mol%, a saponification degree of 99.92 mol% and a polymerization degree of 3000 is impregnated with 10 parts by mass of glycerin and 200 parts by mass of water. After foaming, it was melt-extruded from a T die to a metal roll to form a film. The ethylene-modified PVA film obtained after drying and heat treatment had a thickness of 40 μm, and the average hot water cutting temperature of the film was 70 ° C.

  The ethylene-modified PVA film thus obtained was successively treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to produce a polarizing film. That is, the ethylene-modified PVA film is pre-swelled by immersing it in water at 30 ° C. for 60 seconds. Soaked for 2 minutes. Subsequently, it was uniaxially stretched 6 times in an aqueous solution at 55 ° C. with a boric acid concentration of 4%, and in an aqueous solution at 30 ° C. with a potassium iodide concentration of 60 g / liter, a boric acid concentration of 40 g / liter, and a zinc chloride concentration of 10 g / liter. For 5 minutes, and fixed. Thereafter, the ethylene-modified PVA film was taken out, dried with hot air at 40 ° C. under a constant length, and further subjected to heat treatment at 100 ° C. for 5 minutes. The obtained polarizer had an average thickness of 13 μm, and the polarization performance was a transmittance of 43.0%, a polarization degree of 99.5%, and a dichroic ratio of 40.1.

<Preparation of polarizing plate>
Next, the polarizer A according to the following steps 1 to 5, the cellulose ester film samples 1 to 28 prepared in Example 1, and the cellulose ester film A on the back side, and the polarizer and the bonded polarized light according to the following steps. Plates 101-128 were produced.

  Step 1: Each cellulose ester film was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain a cellulose ester 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 lightly wiped off, and this was placed on the cellulose ester film treated in Step 1.

Step 4: Step 3 Cellulose ester film laminated with the polarizer and the pressure backside cellulose ester film 20-30 N / cm ^2, the conveyance speed was pasted at approximately 2m / min.

  Step 5: The polarizer prepared in Step 4 in the dryer at 80 ° C., the sample obtained by bonding the cellulose ester film samples 1 to 28 and the back side cellulose ester film A are dried for 2 minutes, and the polarizing plates 101 to 128 are obtained. Produced.

<Production of liquid crystal display device>
A liquid crystal panel was produced as follows using each produced polarizing plate, and the characteristics as a polarizing plate and a liquid crystal display device were evaluated.

  The polarizing plates on both sides of the SONY 20-type display KLV-20AP2 previously bonded were peeled off, and the prepared polarizing plates 101 to 128 were each bonded to the glass surface of the liquid crystal cell.

  At that time, the direction of bonding of the polarizing plate is such that the surfaces of the cellulose ester film samples 1 to 28 are on the liquid crystal cell side, and the absorption axis is in the same direction as the polarizing plate previously bonded. The liquid crystal display devices 101 to 128 were respectively manufactured. Moreover, the used polarizing plate used what was cut out from the edge part of the elongate cellulose ester film in which performance is easy to vary.

<Evaluation>
About each of the obtained polarizing plate, the nonuniformity (light leakage) was evaluated by the following method about the polarizing plate dimension stability similarly to the above, and about the liquid crystal display device which affixed the polarizing plate.

(Corner unevenness)
Each of the liquid crystal display devices 101 to 128 is treated at 60 ° C. for 300 hours and then returned to 23 ° C. and 55% RH. After that, the power is turned on and the backlight is turned on, and light leakage of black display is visually observed 2 hours later. And evaluated according to the following criteria.

A: No light leakage
○: There are 1 to 2 weak light leaks. Δ: There are 1 to 2 strong light leaks. X: There are 3 or more strong light leaks. Among the polarizing plates 101 to 128, the polarizing plate using the retardation film of the present invention. In contrast to the comparative example, the dimensional change is small (approximately 0.4% or less) even though the polarizer is thinned. All the devices using the polarizing plate after lighting were good because no light leakage in black display was observed visually.

Claims (7)

It is synthesized from cellulose ester having a total acyl group substitution degree of 2.50 to 2.65, an ultraviolet absorbing monomer represented by the following general formula (1), a hydrophilic ethylenically unsaturated monomer, and an ethylenically unsaturated monomer. A retardation film containing an ultraviolet-absorbing copolymer and having a thickness of 30 to 60 μm.

[Wherein n represents an integer of 0 to 3, R _{1 to} R ₅ represent a hydrogen atom, a halogen atom, or a substituent, and X represents —COO—, —CONR ₇ —, —OCO—, —NR ₇ Represents CO—, and R ₆ and R ₇ represent a hydrogen atom, an alkyl group, or an aryl group. However, the group represented by R ₆ has a polymerizable group as a partial structure. ] The retardation film according to claim 1, wherein the retardation value Ro defined by the following formula (I) or (II) is 30 to 100 nm and Rt is 100 to 300 nm.
Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
[In the formula, nx is the refractive index in the direction with the largest refractive index in the film plane, ny is the refractive index in the film plane in the direction perpendicular to nx, nz is the refractive index in the thickness direction of the film, and d is the refractive index of the film. Each thickness is expressed in nm. ] The retardation film according to claim 1 or 2, comprising an ester plasticizer represented by the following general formula (2).
General formula (2)
B- (GA) _n -GB
[Wherein B represents a benzene monocarboxylic acid residue. G represents an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms and an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. n is an integer of 1-5. ] The retardation film according to claim 1, comprising a polyhydric alcohol ester. A polarizing plate using the retardation film according to claim 1. 6. The polarizing plate according to claim 5, wherein the polarizer used in the polarizing plate is a polarizer having a thickness of 10 to 20 [mu] m using a polyethylene-polyvinyl alcohol copolymer. A liquid crystal display device using the retardation film according to claim 1.