JP2009114371A - Cellulose ester film, polarizing plate, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film causing no micro craze in a film drawing process and allowing stretching with no deterioration in contrast, a polarizing plate using the cellulose ester film, and an image display device. <P>SOLUTION: The cellulose ester film, to which drawing processing is applied, comprises elastic fine particles with an average particle diameter of 0.1-0.5 μm. The elastic fine particles are acrylic polymer fine particles of the core shell structure, wherein a shell part has a crosslinked structure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cellulose ester film, a polarizing plate and an image display device. More specifically, the invention relates to a cellulose ester film that contains elastic fine particles as a matting agent, does not generate microcrazes during film stretching, and does not cause a decrease in contrast. .

In recent years, televisions for home use have been made thinner and the spread of large-sized liquid crystal televisions has also been promoted. Contrast is attracting attention as the performance of large LCD TVs, and is a factor in differentiation. Therefore, various methods for increasing the contrast have been proposed (see, for example, Patent Documents 1 and 2). However, when the polarizing plate used for the liquid crystal television and the polarizing plate protective film used for the polarizing plate are enlarged, the contrast deteriorates, and the enlarged and wide film is difficult to wind, and the yield is poor. there were.
JP 2001-64409 A JP 2006-342227 A

  Accordingly, it is an object of the present invention to provide a cellulose ester film that does not generate microcraze during film stretching and can be widened without a decrease in contrast, a polarizing plate using the cellulose ester film, and an image display device.

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

  1. A cellulose ester film subjected to stretching treatment, comprising elastic fine particles having an average particle diameter of 0.1 to 0.5 μm.

  2. 2. The cellulose ester film as described in 1 above, wherein the cellulose ester film is a retardation film.

  3. 3. The cellulose ester film as described in 1 or 2 above, wherein the elastic fine particles are acrylic polymer fine particles having a core-shell structure.

  4). 4. The cellulose ester film as described in 3 above, wherein the shell part of the elastic fine particles is an acrylic polymer fine particle having a crosslinked structure.

  5). The polarizing plate characterized by using the cellulose ester film of any one of said 1-4 on at least one surface.

  6). 5. An image display device using the cellulose ester film according to any one of 1 to 4 or the polarizing plate according to 5.

  According to the present invention, it is possible to provide a cellulose ester film that does not generate microcraze during film stretching and can be widened without a decrease in contrast, a polarizing plate using the cellulose ester film, and an image display device.

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

  As a result of intensive studies in view of the above problems, the present inventors have found that in a cellulose ester film subjected to stretching treatment, the matting agent contained in the film is a cause of reducing the contrast. Usually, the matting agent contained in the film is used as a secondary agglomerate having a primary particle size of about 14 to 18 nm in which fine particles of silica are dispersed in a solvent and about 0.2 to 0.3 μm. The film to which the matting agent is added is stretched by about 30 to 50% at a temperature of about 130 to 180 ° C. in the stretching step. At this time, the matting agent of the secondary agglomerates is stretched to generate minute voids or minute cracks (hereinafter referred to as crazes) such as tears. In the case of monodispersed spherical fine particles, the same phenomenon occurs because craze is generated around the fine particles due to the difference in hardness between the fine particles and the film resin material. Since this minute craze scatters light, haze is generated in the stretched film and the contrast is lowered.

  If the matting agent is not added, the slipping property is extremely deteriorated, the film cannot be wound up neatly, and the film is deformed. As a countermeasure, there is a method of laminating a protective film at the time of winding, but the conveyance speed in the manufacturing process is lowered, which is not preferable because the productivity is deteriorated.

  As a result of the study, the present inventors have found that the use of elastic fine particles without using hard fine particles such as conventional inorganic fine particles and organic fine particles in the matting agent does not cause fine crazes during film stretching, and contrast. The present inventors have found that a cellulose ester film having no decrease in the thickness can be obtained, and have achieved the present invention.

  Therefore, in the invention of claim 1, the cellulose ester film subjected to the stretching treatment contains elastic fine particles having an average particle diameter of 0.1 to 0.5 μm, so that no microcraze is generated at the time of film stretching, and the contrast is reduced. A cellulose ester film having no decrease can be obtained.

  The invention of claim 2 is characterized in that the cellulose ester film is a retardation film.

  The invention according to claim 3 is characterized in that the elastic fine particles are acrylic polymer fine particles having a core-shell structure.

  The invention of claim 4 is. The shell portion of the elastic fine particle is an acrylic polymer fine particle having a cross-linked structure.

  Invention of Claim 5 and Claim 6 is a polarizing plate and a display apparatus which do not have a contrast fall using the said cellulose-ester film.

  Hereinafter, the present invention will be described in detail.

(Elastic fine particles)
The elastic fine particles are polymer fine particles having a layered structure, and are fine particles having rubbery polymer fine particles (core portion) at a hard outer edge portion such as methyl methacrylate. Usually, a method of forming by seed emulsion polymerization is known. The manufacturing method proposed in JP-A-7-70255 can be used.

  The core of the elastic fine particle is a rubber-like fine polymer particle, preferably an alkyl acrylate rubber, and the alkyl acrylate monomer includes an alkyl acrylate having 2 to 8 carbon atoms in the alkyl group or the alkyl acrylate and a copolymer thereof. A polymerizable monomer is preferably used. In this case, it is desirable to use a crosslinkable monomer and / or a grafting monomer.

  Examples of the alkyl acrylate having 2 to 8 carbon atoms in the alkyl group include ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, and 2-ethylhexyl acrylate. Butyl acrylate is preferably used. Examples of the monomer copolymerizable with the alkyl acrylate include aromatic vinyl such as styrene, vinyl toluene and α-methyl styrene, vinyl cyanide such as aromatic vinylidene, acrylonitrile and methacrylonitrile, vinylidene cyanide, methyl methacrylate, Examples thereof include alkyl methacrylates such as butyl methacrylate. Examples of the crosslinkable monomer include aromatic divinyl monomers such as divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, hexanediol diacrylate, hexanediol dimethacrylate, oligoethylene glycol diacrylate, Examples include alkane polyol polyacrylates or alkane polyol polymethacrylates such as oligoethylene glycol dimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate. Butylene glycol diacrylate and hexanediol diacrylate are preferably used.

  Examples of the grafting monomer include unsaturated carboxylic acid allyl esters such as allyl acrylate, allyl methacrylate, diallyl maleate, diallyl fumarate, diallyl itaconate, and the like. Allyl methacrylate is preferably used. Such crosslinkable monomers and grafting monomers are used in an amount of about 0.05 to 2% by mass, preferably about 0.1 to 1% by mass, based on the total amount of monomers of the core latex. The obtained core polymer is a rubbery polymer having a glass transition temperature of preferably −30 ° C. or lower. When the glass transition temperature exceeds −30 ° C., the craze during stretching may not be improved. The mass ratio of the core latex is desirably in the range of 40 to 70 mass% with respect to the entire core-shell polymer. The higher the ratio of the core-shell part, the better the effect of improving the craze, and the lower the ratio of the core-shell, the better the slipperiness.

  Subsequently, the polymerization of the methyl methacrylate glassy shell portion is performed by emulsion polymerization of a methyl methacrylate monomer in the presence of the core latex. As the methyl methacrylate monomer, methyl methacrylate or the methyl methacrylate and a monomer copolymerizable therewith are preferably used.

  Examples of the monomer copolymerizable with methyl methacrylate include alkyl acrylates such as ethyl acrylate and butyl acrylate, alkyl methacrylates such as ethyl methacrylate and butyl methacrylate, aromatic vinyl such as styrene and α-methyl styrene, aromatic vinylidene, Examples thereof include vinyl polymerizable monomers such as vinyl cyanide and vinylidene cyanide such as acrylonitrile and methacrylonitrile. Ethyl acrylate, styrene or acrylonitrile is preferably used. Also in the polymerization of the shell portion, if necessary, a small amount of a crosslinkable monomer may be used as a copolymerization monomer in addition to the above-mentioned monomer, and in this way, higher impact resistance can be imparted to the thermoplastic resin. In some cases, a core-shell polymer can be obtained. In this case, as the crosslinkable monomer, the same one used in the polymerization for forming the core can be used, and such a crosslinkable monomer is usually used for polymerization of the shell part. It is used in the range of 0.01 to 2% by mass, preferably 0.1 to 1% by mass of the monomer amount. The obtained shell polymer is a glassy polymer having a glass transition temperature of preferably 60 ° C. or higher. When the glass transition temperature is less than 60 ° C., the agglomeration of particles increases, and the dispersion may deteriorate. In addition, the shell part is a methacrylic ester crosslinking agent such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, etc. It is preferable to crosslink with the above because of excellent solvent resistance.

  A method for confirming that the fine particles have a core-shell structure can be confirmed by comparing the size of the core fine particles with the size of the fine particles after polymerization. Further, the fine particles having a crosslinked structure in the shell portion can be confirmed by comparing the solvent resistance of the core fine particles and the fine particles after polymerization and imparting the solvent resistance. It is also possible to embed microparticles with a resin, prepare a slice of a fault, and confirm it with an electron microscope or the like. In this case, the shell portion or the core portion may be colored for easy observation.

  The average particle size is in the range of 0.1 to 0.5 μm. When the average particle size is small, sufficient slipperiness cannot be exhibited, and when the average particle size is large, haze deteriorates due to scattering by the particles and the contrast is lowered. Is necessary.

  The average particle diameter is obtained from the particle diameter of 100 arbitrary particles by observing fine particles with an electron microscope, for example. Here, each particle size is expressed by a diameter assuming a circle equal to the projected area. Alternatively, it can be obtained by diluting fine particles in a solvent and measuring using a dynamic light scattering method particle size measuring apparatus Zeta Sizer 1000HS (manufactured by Malvern).

  The refractive index is preferably close to the film to be added with little increase in haze. Since the refractive index of the cellulose ester film is about 1.47 to 1.49, the refractive index of the elastic fine particles is preferably 1.46 to 1.50, more preferably 1.47 to 1.49.

The amount of the elastic fine particles added is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and still more preferably 0.08 to 0.16 g per 1 m ^{2 of} the cellulose ester film.

  The elasticity of the elastic fine particles cannot be measured by the generally known method because it is in the form of fine particles. However, as a simple method, a thermomechanical measuring device is used by the method shown below, and the compressive displacement of the fine particles with respect to the load of the dry filler It is possible to determine the elasticity and the elasticity of the fine particles. The elastic fine particles referred to in the present invention are 0.5 to 20%, more preferably 1 to 10%, and most preferably 1 to 2% in terms of compressive displacement.

(Compression displacement rate)
Using a thermomechanical measuring device (trade name TMA-10, manufactured by Seiko Denshi Kogyo Co., Ltd.), a cylindrical sample packed in an area of 24 mm ² and a height of 2 mm is subjected to a compression displacement of a height when a load of 30 g is applied. The amount (mm) was measured, and the compression displacement rate was determined by the following equation.

Compression displacement rate (%) = Compression displacement amount (mm) ÷ 2 (mm) × 100
A general disperser can be used to disperse the elastic fine particles. For example, a sand mill or a high pressure homogenizer is preferably used. In the sand mill, beads having a diameter of 0.3 to 3 mm and a mill base are placed, the disk is rotated at 300 to 3000 rpm, and the centrifugal force of the beads is used to cause collision and shearing for dispersion. Examples of the beads used include glass beads, zirconia beads, alumina beads, and steel beads. In the present invention, zirconia beads with less contamination and glass beads that do not cause a problem even when contaminated are particularly preferable. The sand mill includes various types of sand mills such as a vertical type, a horizontal type, and an annular type. In the present invention, a horizontal type or an annular type sand mill with a more uniform dispersion shear force is particularly preferable. In addition, sand mills often have contamination due to beads, shafts, and the inside of a dispersion container being shaved by beads. Therefore, it is preferable to minimize the contamination by applying a ceramic coating or a Teflon (registered trademark) coating to the inside of the disk, shaft, or dispersion container.

  Examples of sand mills include Dino Mill (WA Bachofen), NEW My Mill (Mitsui Mine Co., Ltd.), SC Mill (Mitsui Mine Co., Ltd.), Nano Glen Mill (Asada Iron Works Co., Ltd.), and the like.

  A high-pressure homogenizer is a medialess disperser that disperses by a shear force or impact force of a collision by causing a mill base to pass through a narrow tube or an orifice at high speed or causing the mill bases to collide with each other. The mill bases collide with each other at a high pressure of 10 to 300 MPa, or pass through a thin tube or an orifice of 50 to 2000 μm.

  Examples of high-pressure homogenizers include microfluidizers (Mizuho Kogyo Co., Ltd.), optimizers (Sugino Machine Co., Ltd.), nanomizers (Yoshida Kikai Kogyo Co., Ltd.), clear mix, clear mix W motion (M Technique Co., Ltd.) ))and so on.

  Dispersers such as ultrasonic dispersers, ball mills, high-speed dispersers, attritors, triple roll mills, Henschel mixers, and kneaders can also be used.

  As a method for adding the fine particles, a method in which the fine particle dispersion is directly added to the dope is preferable because the generation of foreign matters is small. Further, it can be added to a dope after being added in advance to a liquid containing a small amount of resin.

(Cellulose ester)
The cellulose ester used in the cellulose ester film of the present invention is preferably 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, it is difficult to obtain the retardation development required for the thin film retardation film. 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, and when the substitution degree of acetyl group is X and the substitution degree of propionyl group or butyryl group is Y, 2.50 ≦ X + Y ≦ 2. 65
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 most preferred cellulose ester is therefore cellulose acetate propionate.

  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.

(Plasticizer)
The cellulose ester film of the present invention can contain a plasticizer as necessary to obtain the effects of the present invention. The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester plasticizer. Agent, acrylic plasticizer and the like. Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer 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. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

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

Formula (a) R1- (OH) n
However, R1 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

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

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

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

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

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

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

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

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

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

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

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

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

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

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

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

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

Formula (b) R2 (COOH) m (OH) n
(Wherein R2 is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxyl group, and an OH group is an alcoholic or phenolic hydroxyl group)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these. Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

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

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

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

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

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

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. And aromatic monocarboxylic acids possessed by them, or derivatives thereof. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Viscosity (25 ° C., mPa · s); 37000
Acid value: 0.05
Although the specific compound of the aromatic terminal ester plasticizer which can be used for this invention below is shown, this invention is not limited to this.

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

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

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products manufactured by Ciba Specialty Chemicals and can be preferably used.

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

  For example, as the benzotriazole ultraviolet absorber, a compound represented by the following general formula (d) can be used.

In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R 5 may be the same or different, and are a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, an alkoxyl group, an acyloxy group. Represents an aryloxy group, an alkylthio group, an arylthio group, a mono- or dialkylamino group, an acylamino group, or a 5- to 6-membered heterocyclic group, and R ₄ and R ₅ are closed to form a 5- to 6-membered carbocyclic ring. May be.

  Moreover, these groups described above may have an arbitrary substituent.

  Although the specific example of the benzotriazole type ultraviolet absorber used for this invention below is given, this invention is not limited to these.

UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole UV-3 : 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-Chlorobenzotriazole UV-5: 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole UV-8: 2- (2H-benzotriazol-2-yl) -6 (Linear and side chain dodecyl) -4-methylphenol (TINUVIN171)
UV-9: Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- 4-Hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate mixture (TINUVIN 109)
Further, as the benzophenone ultraviolet absorber, a compound represented by the following general formula (e) is preferably used.

  In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group may have a substituent. A represents a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group or a —CO (NH) n-1-D group, and D represents an alkyl group, an alkenyl group or a substituent. Represents a phenyl group which may have m and n represent 1 or 2.

  In the above, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, the alkoxyl group represents, for example, an alkoxyl group having up to 18 carbon atoms, and the alkenyl group has, for example, carbon number An alkenyl group up to 16 represents an allyl group, a 2-butenyl group, or the like. In addition, as substituents to alkyl groups, alkenyl groups, and phenyl groups, halogen atoms such as chlorine atoms, bromine atoms, fluorine atoms, etc., hydroxyl groups, phenyl groups (this phenyl group is substituted with alkyl groups or halogen atoms, etc.) May be used).

  Specific examples of the benzophenone-based ultraviolet absorber represented by the general formula (e) are shown below, but the present invention is not limited thereto.

UV-10: 2,4-dihydroxybenzophenone UV-11: 2,2'-dihydroxy-4-methoxybenzophenone UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-13: Bis (2-methoxy -4-hydroxy-5-benzoylphenylmethane)
In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  The cellulose ester film according to the present invention preferably contains two or more kinds of ultraviolet absorbers.

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

  The method for adding the UV absorber is to add the UV absorber to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane, or a mixed solvent thereof. Or you may add directly in dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

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

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film may be deteriorated. The antioxidant has a role of delaying or preventing the cellulose ester film from being decomposed by, for example, a residual solvent amount of halogen in the cellulose ester film or phosphoric acid of a phosphoric acid plasticizer. It is preferable to make it contain in a film.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

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

  Moreover, in this invention, the conventional fine particle mat agent can be contained in the cellulose ester film in the range which does not inhibit the effect of this invention. Examples of the fine particle matting agent include inorganic substances such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. It is preferable to contain fine particles 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 preferably in the range of 0.01 to 1.0 μm. 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 become secondary particles of a cellulose ester film of 0.01 to 1.0 μm. 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 can be easily made 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 tend to 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 preferable that the optical performance is improved by maintaining or stretching the width in an arbitrary process after peeling from the support with a 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.

  For example, the tenter-type stretching operation in which both ends of the web are gripped by clips or the like may be performed in multiple stages, and biaxial stretching is preferably performed 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 x2.0 times in the width direction and x0.8 to x1.5 times in the longitudinal direction (casting direction), particularly x1 in the width direction. 0.1 to x1.8 times and preferably in the longitudinal direction x0.9 to x1.3 times. Particularly preferably, it is x1.1 to x1.5 times in the width direction and x0.9 to x1.1 times in the longitudinal direction.

  The effect of the elastic fine particles is exerted by stretching. The difference is not seen at 1.0 times, but the effect is seen at 1.05 times or more, the remarkable difference is seen at 1.25 times or more, and the difference in haze becomes the largest at 1.4 times or more. This is effective for improving the contrast. If the resin is stretched to 2.0 times or more, the whitening phenomenon of the resin itself occurs, and therefore a stretch ratio of less than 2.0 times is desirable.

  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 preferably in the range of 30 to 80 μm.

  The width of the cellulose ester film is preferably 1.4 m or more, and preferably in the range of 1.5 m to 3 m for a large-sized liquid crystal display device from the viewpoint of productivity.

  The cellulose ester film of the present invention is preferably a retardation film that has been subjected to the stretching operation to control birefringence.

  The retardation film (stretched cellulose ester film) has a retardation value Ro defined by the following formula (I) of 20 to 100 nm and a retardation value Rt defined by the following formula (II) in the range of 70 to 400 nm. It is preferable that it exists in.

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.

  Particularly preferred ranges for the retardation value are Ro of 45 to 75 (nm), Rt of 70 to 200 (nm), and more preferably 100 to 150 (nm).

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

(Polarizer)
The polarizing plate of the present invention is characterized in that it is a polarizing plate bonded to at least one surface of a polarizer using the cellulose ester film of the present invention as a polarizing plate protective film.

  The polarizing plate of the present invention can be produced by a general method. The cellulose ester film of the present invention is preferably bonded to at least one surface of a polarizer produced by subjecting the polarizer side to alkali saponification treatment and immersion drawing in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Even if this cellulose-ester film is used for the other surface, another polarizing plate protective film can also be bonded. For example, a commercially available cellulose ester film (for example, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4UE, KC8UE, KC8UY-HA, KC8UY-HA, KC8UY-C8 -RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

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

  The cellulose ester film of the present invention is preferably a retardation film that has been subjected to the stretching operation to control birefringence, and is preferably a film having an optical compensation function. Therefore, in the case of a liquid crystal display device, it is preferably designed as a polarizing plate protective film bonded to the liquid crystal cell side.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol is also preferably used. Among them, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. 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 in order to reduce color spots, and two points separated 1 cm 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.

  A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has few color spots, and is particularly preferably used for a large-sized liquid crystal display device.

  The polarizer obtained as described above is usually used as a polarizing plate with a protective film bonded to both sides or one side thereof. Examples of the adhesive used for pasting include a PVA-based adhesive and a urethane-based adhesive, among which a PVA-based adhesive is preferably used.

(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 ester film and retardation film of the present invention are various types of driving such as reflective type, transmissive type, transflective type LCD, TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type, etc. It is preferably used in the LCD of the type. The cellulose ester film and retardation film of the present invention are excellent in flatness and are preferably used in various display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and electronic paper. In particular, in a large-screen display device having a screen of 30 or more types, particularly 30 to 54 types, there is no white spot at the periphery of the screen, and the effect is maintained for a long period of time. MVA liquid crystal display device, IPS liquid crystal display A noticeable effect is observed in the device. In particular, according to the present invention, there is little color unevenness, glare and wavy unevenness, and there is an effect that eyes are not tired even during long-time viewing.

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

Example 1
(Method for producing elastic fine particle A)
In a 10 liter polymerization vessel equipped with a reflux condenser, 1500 parts by mass of deionized water and 75 parts by mass of 10% aqueous solution of Emulgen 950 (manufactured by Kao Corporation) were charged, and the temperature was raised to 70 ° C. while stirring under a nitrogen stream. . After adding 75 parts by mass of ethyl acrylate and dispersing for 10 minutes, 6 parts by mass of 10% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.) Was added and stirred for 1 hour to prepare a seed latex.

  The seed latex was heated to 75 ° C., and 2.38 parts of 2,2′-azobis (2- (2-imidazolin-2-yl) propane) (VA-061 manufactured by Wako Pure Chemical Industries, Ltd.) was added. Furthermore, the following core-forming monomer emulsion was continuously fed over 200 minutes to perform seed polymerization.

(Core-forming monomer emulsion)
2-ethylhexyl acrylate 923 parts by weight Butyl acrylate 247 parts by weight Acrylic methacrylate 2.5 parts by weight 1,4-butylene glycol diacrylate 2.5 parts by weight 10% aqueous solution of Emulgen 950 (manufactured by Kao Corporation) 750 parts by weight Deionized 3750 parts by weight of water After feeding the monomer emulsion, the temperature was raised to 90 ° C. and aged for 1 hour to form a core. The mass average particle diameter of the core was 0.10 μm.

  This was cooled to 70 ° C., and 1.25 parts by mass of 2,2′-azobis (2- (2-imidazolin-2-yl) propane) (VA-061 manufactured by Wako Pure Chemical Industries, Ltd.) was added. The monomer emulsion was continuously fed over 40 minutes to perform seed polymerization for shell formation.

Methyl methacrylate 805 parts by weight Ethyl acrylate 95 parts by weight Styrene 48 parts by weight Methacrylamide 6.3 parts by weight Diethylene glycol dimethacrylate 476 parts by weight A 10% aqueous solution of Emulgen 985 (manufactured by Kao Corporation) 190 parts by weight Deionized water 381 parts by weight Monomer After feeding the emulsion, the temperature was raised to 75 ° C. and aged for 1 hour to form a shell.
This was cooled and filtered, frozen at −30 ° C., dehydrated and washed with a centrifuge, and blown and dried at 60 ° C. to obtain core-shell type elastic fine particles A.

  The average particle size of the fine particles was obtained by diluting the fine particles 50 times by mass with ethanol and measuring the fine particles using a dynamic light scattering method particle size measuring apparatus Zetasizer 1000HS (manufactured by Malvern).

(Method for producing elastic fine particle B)
Elastic fine particles B were obtained in the same manner except that the amount of the emulsion for seed polymerization for shell formation of the elastic fine particles A was 2/3 parts by mass and the continuous feed time was 27 minutes.

(Method for producing elastic fine particles C)
Elastic fine particles C were obtained in the same manner except that 923 parts by mass of 2-ethylhexyl acrylate of the monomer emulsion for core formation of elastic fine particles A was changed to 461 parts by mass and 247 parts by mass of butyl acrylate was changed to 709 parts by mass. It was.

(Method for producing elastic fine particle D)
Elastic fine particles D are obtained in the same manner except that 923 parts by mass of 2-ethylhexyl acrylate in the monomer emulsion for core formation of elastic fine particles A is changed to 247 parts by mass and 247 parts by mass of butyl acrylate is changed to 923 parts by mass. It was.

(Method for producing elastic fine particles E)
Elastic fine particles E were obtained in the same manner except that the amount of the emulsion for seed polymerization for forming the shell of elastic fine particles D was 2/3 parts by mass and the continuous feed time was 27 minutes.

(Method for producing elastic fine particle F)
Elastic fine particles F were obtained in the same manner except that the composition of the monomer emulsion for shell formation of the elastic fine particles C was changed to the following composition.

<Monomer emulsion for shell formation of elastic fine particle F>
Methyl methacrylate 1056 parts by weight Ethyl acrylate 125 parts by weight Styrene 63 parts by weight Methacrylamide 6.3 parts by weight 10% aqueous solution of Emulgen 985 (manufactured by Kao Corporation) 250 parts by weight Deionized water 500 parts by weight (Production method of fine particles G)
Fine particles G were obtained in the same manner except that the composition of the core emulsion monomer emulsion of the elastic fine particles A was changed to the following composition, the polymerization time was 240 minutes, and the shell formation seed polymerization was not performed.

<Monomer emulsion for core formation of fine particles G>
2-ethylhexyl acrylate 1100 parts by weight Butyl acrylate 300 parts by weight Diethylene glycol dimethacrylate 476 parts by weight Acrylic methacrylate 3.0 parts by weight 1,4-butylene glycol diacrylate 3.0 parts by weight 10% of Emulgen 950 (manufactured by Kao Corporation) Aqueous solution 900 parts by weight Deionized water 4500 parts by weight [Preparation of cellulose ester film sample]
A cellulose ester solution was prepared using the cellulose ester, additives, fine particles, and solvent described in Table 1 so as to have a dope composition as shown in Table 2.

  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, and then the solution was added to Azumi Filter Paper No. 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 (simply 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 100% 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 1.40 times in the width direction. The film was stretched in a hot air zone at 150 ° C. 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 a third drying zone set at 120 ° C. for drying. Then, cellulose ester film samples 1 to 20 having a film thickness of 40 μm having a width of 1.9 m and a knurling of 1.5 cm in width and 8 μm in height were produced.

<Evaluation>
(Haze)
<3 sheets value>
Three film samples were superposed and measured according to ASTM-D1003-52 using T-2600DA manufactured by Tokyo Denshoku Industries Co., Ltd.

(Dynamic friction coefficient)
The dynamic friction coefficient between the film surface and the back surface is cut out so that the front and back surfaces of the film are in contact with each other according to JIS-K-7125-ISO8295, a 200 g weight is placed, the sample moving speed is 100 mm / min, and the contact area is 80 mm × 200 mm. The weight was pulled horizontally under the conditions, the average load (F) while the weight was moving was measured, and the dynamic friction coefficient (μ) was determined from the following formula.

Coefficient of dynamic friction (μ) = F (gf) / weight of weight (gf)
<Measurement of retardation Ro and Rt>
Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), film retardation measurement at a wavelength of 590 nm was performed under the same environment for 24 hours in an environment of 23 ° C. and 55% RH. went. The above-mentioned average refractive index and film thickness were input into the following formula, and values of in-plane retardation (Ro) and retardation in the thickness direction (Rt) were obtained.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the film thickness direction, d Is the film thickness (nm).)
(Preparation of polarizing plate)
<Production of polarizer>
A 120 μm polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to prepare a polarizer having a width of 1.4 m. The film thickness was 25 μm.

<Preparation of polarizing plate>
The produced cellulose ester film samples 1 to 20 and a commercially available polarizing plate protective film, Konica Minolta Tack KC8UX (manufactured by Konica Minolta Opto, Inc., film thickness: 80 μm) are subjected to saponification treatment under the alkali saponification treatment conditions shown below. It was.

  Next, using the prepared polarizer, a fully saponified polyvinyl alcohol 5% aqueous solution was used to laminate KC8UX, a polarizer, and the prepared cellulose ester film sample in this order. Polarizing plates 1 to 20 using film samples were produced.

<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.

(Degree of polarization)
The parallel transmittance and the direct transmittance were measured for the polarizing plate, and the degree of polarization was calculated according to the following formula.

Polarization degree P = ((H0−H90) / (H0 + H90)) 1/2 × 100
H0: Parallel transmittance H90: Direct transmittance (contrast of liquid crystal panel)
The polarizing plate of the present invention and the comparative example obtained above is peeled off the retardation film and the polarizing plate previously bonded to the 32-type liquid crystal television KDL-32V2000 made by SONY, and the polarizing plate of the present invention and the comparative example is absorbed. The axes were bonded so as to be in the same direction as the absorption axis of the polarizing plate that had been bonded in advance, a display device was produced, and the contrast was evaluated. For evaluation, ELZIM EZ-contrast was used to measure the amount of transmitted light during black display and white display. Contrast = (transmitted light amount during white display: cd / cm ² ) / (transmitted light amount during black display: cd / cm ² ) was calculated and evaluated.

  From the results in Table 3, the cellulose ester film samples 1 to 6, 9 to 11 and 13 to 18 of the present invention can obtain a desired retardation as a retardation film or a polarizing plate protective film, have a low haze, and are conventional. It turns out that it has a dynamic friction coefficient equivalent to the cellulose-ester film sample of the comparative example using microparticles | fine-particles.

  Moreover, it turns out that the polarizing plate of this invention and a liquid crystal display device using the same are excellent in a polarization degree and contrast.

Example 2
The haze when the stretching ratio in the film width direction of the cellulose ester film samples 3 and 8 of Example 1 was changed as shown in the following table was measured, and the results are shown in the following table.

  From the results of Table 4, when the draw ratio is 0%, the effect of the elastic fine particles is not seen, but the haze of the sample 8 of the comparative example increases as the draw ratio increases, It can be seen that the sample 3 to which the elastic fine particles were added was excellent because no increase in haze was observed even when the draw ratio increased.

Claims (6)

A cellulose ester film subjected to stretching treatment, comprising elastic fine particles having an average particle diameter of 0.1 to 0.5 μm. The cellulose ester film according to claim 1, wherein the cellulose ester film is a retardation film. The cellulose ester film according to claim 1 or 2, wherein the elastic fine particles are acrylic polymer fine particles having a core-shell structure. The cellulose ester film according to claim 3, wherein the shell part of the elastic fine particles is an acrylic polymer fine particle having a crosslinked structure. The polarizing plate characterized by using the cellulose-ester film of any one of Claims 1-4 for at least one surface. An image display device using the cellulose ester film according to claim 1 or the polarizing plate according to claim 5.