JP2007056093A - Optical cellulose ester film for display, method for manufacturing the same, polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a cellulose ester film, whereby bleed-out failure of the film can be suppressed, deterioration in film appearance can be greatly improved, staining of rolls used in steps for manufacturing the film can be prevented, bleed-out of the cellose ester film used as a protective film for a polarizing plate can be suppressed, deterioration in appearance of the polarizing plate can be prevented and visibility of a liquid crystal display can be improved, the cellulose ester film obtained through the method, and the liquid crystal device using the cellulose ester film. <P>SOLUTION: In the method for manufacturing the cellulose ester film for a display, a coating liquid containing a cellulose ester resin is applied and dried on either or both sides of the cellulose ester film obtained by molding a cellulose ester resin having an organic additive through T-die melt extrusion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an optical cellulose ester film for display (hereinafter also simply referred to as a cellulose ester film, film), an optical cellulose ester film for display, and a liquid crystal display (LCD) using the same. Method for producing optical cellulose ester film for display, which can improve bleed-out from optical cellulose ester film for use, can prevent roll contamination in the production process, and has high productivity, and display optics obtained from the production method The present invention relates to a cellulose ester film and a liquid crystal display (LCD).

  In recent years, as liquid crystal display devices (LCD) are used in various places, higher productivity (increased production) is also demanded for liquid crystal display elements used in LCDs, that is, polarizing plates.

  By the way, as a protective film for LCD polarizing plates, cellulose triacetate (TAC) films are mainly used. However, with the increase in productivity of polarizing plates, such a cellulose triacetate film for LCDs has been increasing. As productivity increases, the load on the quality of cellulose triacetate film increases, and in particular, bleed-out failure of the film, in-process roll contamination during film production, and appearance deterioration of the film occur. Sexification was not easy.

  Thus, conventionally, the production of the cellulose triacetate film was handled by setting production conditions, but there was a limit to this, and it was necessary to change the properties of the film itself.

By the way, as a technique for improving the bleed out of the cellulose ester film used in the conventional protective film for polarizing plate, the content of bleed out additives such as plasticizers and ultraviolet absorbers is not lowered, and high temperature heat treatment is performed. Even if it is not, a technique for preventing the precipitation (bleed out) of a plasticizer, an ultraviolet absorber or the like is disclosed, but it is not yet satisfactory. (For example, see Patent Document 1)
In addition, a technique is disclosed in which a cellulose ester film having a laminated structure of a skin layer / core layer / skin layer in which a plasticizer and an ultraviolet absorber are included only in a core layer during melt casting of the cellulose ester film is produced by coextrusion. (For example, see Patent Document 2), the purpose of preventing bleeding out is because the plasticizer and the ultraviolet absorber move between the layers in the stage of co-extrusion.
JP 2001-54936 A JP 2000-352620 A

  As described above, in the existing cellulose ester film, when the productivity of the protective film for polarizing plate is increased with the increase in productivity of the liquid crystal display element, that is, the polarizing plate, In-process roll contamination during production of the film, deterioration of the appearance of the film, and the like occurred, and there was a problem that high productivity was not easy.

  The inventor of the present invention has been made in view of the above-mentioned problems, and the object of the present invention is to solve the above-described problems of the prior art and to increase the productivity (increase in production volume) of liquid crystal display elements, that is, polarizing plates. Along with this, the cellulose ester film used as a protective film for polarizing plates can suppress the bleed-out failure of the film, greatly improves the appearance deterioration of the film, and prevents in-process roll contamination during film production. In addition, by suppressing the bleed-out of the cellulose ester film used as a protective film for a polarizing plate, it is possible to prevent the deterioration of the appearance of the polarizing plate and improve the visibility of the liquid crystal display. , A cellulose ester film production method, and a cellulose ester obtained from the production method To provide a liquid crystal device using the Irumu and the cellulose ester film.

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

  1. An optical cellulose ester for display, wherein a cellulose ester resin-containing coating solution is formed on one or both sides of a cellulose ester film formed by a T-die melt extrusion method and dried. A method for producing a film.

  2. 2. The method for producing an optical cellulose ester film for display according to 1 above, wherein a coating liquid containing a cellulose ester resin is coated on both sides of the cellulose ester film formed by the T-die melt extrusion method and dried.

  3. 3. The method for producing an optical cellulose ester film for display as described in 1 or 2 above, wherein the organic additive is a plasticizer.

  4). 4. The method for producing an optical cellulose ester film for display according to any one of 1 to 3, wherein the coating liquid contains inorganic fine particles.

  5. 5. The optical cellulose ester for display according to 4 above, wherein the number average particle diameter of the inorganic fine particles in the coating solution is 0.1 to 10.0 μm and the content is 0.1 to 2% by mass. A method for producing a film.

  6). 6. The method for producing an optical cellulose ester film for display according to any one of 1 to 5, wherein the cellulose ester resin is cellulose acetate propionate.

  7). 7. The method for producing an optical cellulose ester film for display as described in 6 above, wherein the cellulose acetate propionate has a propionyl substitution degree of 0.1 to 2.

  8). Any one of said 1-7 characterized by manufacturing by apply | coating the coating liquid containing a cellulose-ester resin on the cellulose-ester film shape | molded by the T-die melt extrusion method, after extending | stretching at least uniaxial direction. The manufacturing method of the optical cellulose-ester film for a display of description.

  9. 8. The cellulose ester film formed by a T-die melt extrusion method is stretched in a uniaxial direction, and then the coating solution is applied and dried on the cellulose ester film. A method for producing an optical cellulose ester film for display.

  10. 10. The method for producing an optical cellulose ester film for display according to any one of 1 to 9 above, wherein the temperature for molding by T-die melt extrusion is Tg + 50 ° C. to Tg + 150 ° C. of cellulose.

  11. The method for producing an optical cellulose ester film for display according to any one of claims 1 to 10, wherein the optical cellulose ester film for display has a thickness of 20 to 150 µm.

  12 An optical cellulose ester film for display, which is obtained by the method for producing an optical cellulose ester film for display according to any one of 1 to 11 above.

  13. 13. A polarizing plate using the optical cellulose ester film for display described in 12 above on at least one surface.

  14 13. A liquid crystal display device, wherein the optical cellulose ester film for display described in 12 or the polarizing plate described in 13 is disposed in a liquid crystal cell.

  That is, as a result of various studies by the present inventor, among organic additives, especially hydrophobic plasticizer is added in a large amount, and if the plasticizer bleedout is suppressed, the bleedout of other organic additives can also be prevented. Applying and drying a coating solution containing cellulose ester resin on one or both sides of an organic additive, in particular a cellulose ester film having a plasticizer, formed by T-die melt extrusion method. It has been found that a method for producing an optical cellulose ester film for display produced by the method and a cellulose ester film obtained by the production method can solve the object of the present invention.

  Moreover, in this invention, although the said coating liquid is effective also by single-sided application | coating on a cellulose-ester film, the direction where both surfaces apply | coated is preferable at the point which shows the effect of this invention more.

  The method for producing a cellulose ester film according to the present invention, the cellulose ester film obtained from the production method, and a liquid crystal device using the cellulose ester film can suppress the bleed-out failure of the film, and can improve the appearance deterioration of the film. In addition, it is possible to prevent in-process roll contamination during the production of the film, high productivity is possible, and by suppressing the bleed-out of the cellulose ester film used as a protective film for a polarizing plate, As a result, the appearance deterioration of the polarizing plate can be prevented, and the visibility of the liquid crystal display can be improved.

  Hereinafter, the present invention will be described in more detail.

  In the present invention, a cellulose ester resin-containing coating solution is applied on one or both sides of a cellulose ester film having an organic additive (particularly a plasticizer) formed by a T-die melt extrusion method. The method for producing an optical cellulose ester film for display characterized by the production and the cellulose ester film obtained by the production method can suppress the bleed-out failure of the film, which is the object of the present application, and deteriorate the appearance of the film. It is possible to prevent the in-process roll contamination during the production of the film, improve the productivity, and suppress the bleed-out of the cellulose ester film used as the protective film for the polarizing plate. , And in turn, prevent deterioration of the appearance of the polarizing plate Doo is than made, and, by using the cellulose ester film or a polarizing plate in a liquid crystal display device was improved visibility.

  A coating solution containing a cellulose ester resin on one or both sides of a cellulose ester film having at least one additive selected from a plasticizer or an ultraviolet absorber formed by molding a cellulose ester resin by a T-die melt extrusion method will be described.

  As the cellulose acetate resin used in the coating solution, a resin similar to the cellulose acetate resin formed by the T-die melt extrusion method described later is used.

  Examples of the solvent to be dissolved include, for example, chloroform and dichloromethane, carbon tetrachloride and dichloroethane, tetrachloroethane and trichloroethylene, halogenated hydrocarbons such as tetrachloroethylene, chlorobenzene, and orthodichlorobenzene, phenols such as phenol and parachlorophenol, and benzene. And toluene, xylene, methoxybenzene, aromatic hydrocarbons such as 1,2-dimethoxybenzene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, ketones such as N-methyl-2-pyrrolidone And esters such as ethyl acetate and butyl acetate.

  Further, alcohols such as t-butyl alcohol and glycerin, ethylene glycol and triethylene glycol, ethylene glycol monomethyl ether and diethylene glycol dimethyl ether, propylene glycol and dipropylene glycol and 2-methyl-2,4-pentanediol, dimethylformamide and dimethyl Examples of the solvent include amides such as acetamide, nitriles such as acetonitrile and butyronitrile, ethers such as diethyl ether, dibutyl ether and tetrahydrofuran, methylene chloride, carbon disulfide, ethyl cellosolve and butyl cellosolve.

  A solvent can be used individually or in mixture of 2 or more types in an appropriate combination. The solution is prepared by dissolving 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, particularly 0.5 to 5 parts by weight of the cellulose ester resin with respect to 100 parts by weight of the solvent in view of the viscosity of the coating solution. Are preferred.

  In order to apply the prepared coating liquid on one or both sides of a cellulose ester film having at least one additive selected from a plasticizer or an ultraviolet absorber formed by molding a cellulose ester resin by a T-die melt extrusion method, for example, Known coating methods such as a dip coating method, a reverse coating method, a gravure roll method, a wire bar method, an extrusion coating method, and a curtain coating method can be applied. Among them, the extrusion coating method can be preferably applied from the viewpoint of mass productivity of a film with little thickness unevenness and alignment strain unevenness.

  For example, single-sided coating is performed by releasing a cellulose ester film having at least one additive selected from a plasticizer or an ultraviolet absorber formed from a cellulose ester resin by a T-die melt extrusion method to room temperature (20 ° C. to 30 ° C.). It is cooled, coated on the cellulose ester film by an extrusion coating method, and dried. In this case, it may be performed in the same process, or the cellulose ester film may be wound up once and performed in a separate process.

  In double-sided coating, the cellulose ester film coated on one side is wound up, and in another step, the coating solution may be further coated on the back side coated on one side and dried. As shown in Fig. 1, a cellulose ester film having at least one additive selected from a plasticizer or an ultraviolet absorber that is continuously coated on the back surface and dried to coat the coating solution on both sides is obtained.

  The film thickness after coating and drying the coating solution is preferably 1 μm to 10 μm (one side, both sides). If it is less than 1 μm, the effect of the present invention cannot be obtained, and if it exceeds 10 μm, a large amount of solvent is used, which is not preferable from an environmental viewpoint.

  The cellulose film having the organic compound of the present invention is a cellulose ester film formed by a T-die melt extrusion method. The molding temperature is Tg + 50 ° C. or more and Tg + 150 ° C. or less of cellulose.

(Cellulose ester resin (hereinafter also referred to as cellulose ester))
The cellulose ester resin of the present invention is the cellulose single or mixed acid ester which shows a structure of a cellulose ester and contains at least one of a fatty acyl group and a substituted or unsubstituted aromatic acyl group. And it has at least 1 type of additive chosen from a plasticizer or a ultraviolet absorber.

  Hereinafter, cellulose esters useful for satisfying the object of the present invention will be exemplified, but the present invention is not limited thereto.

  In the cellulose ester of the present invention, when the hydrogen atom of the hydroxyl group of cellulose is a fatty acid ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, butyryl, Examples thereof include isobutyryl, valeryl, pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl and the like.

Moreover, when the esterified substituent of the cellulose ester is an aromatic ring, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, and particularly preferable. Is one or two. Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

  The cellulose ester has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group, which is used as the structure used in the cellulose ester of the present invention. These may be a single or mixed acid ester of cellulose, or a mixture of two or more cellulose esters.

  In the cellulose ester constituting the polarizing plate protective film of the present invention, at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate It is preferable that

  Among these, more preferred cellulose esters include cellulose propionate, cellulose butyrate, cellulose acetate propionate and cellulose acetate butyrate.

  As the substitution degree of the mixed fatty acid ester, more preferred cellulose acetate propionate and lower fatty acid ester of cellulose acetate butyrate have an acyl group having 2 to 4 carbon atoms as a substituent, and the substitution degree of the acetyl group is X, When the substitution degree of propionyl group or butyryl group is Y, it is a cellulose resin containing a cellulose ester that simultaneously satisfies the following formulas (I) and (II).

Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Of these, cellulose acetate propionate is particularly preferably used. Among them, 1.5 ≦ X ≦ 2.5, 0.1 ≦ Y ≦ 2.0 is preferable, and 0.3 ≦ Y ≦ 0. 9 is preferred. If Y is less than 0.1, the decomposition during melt film formation is severe, and if it exceeds 2.0, the elastic modulus of the film formed becomes low and it cannot be practically used. The part not substituted with the acyl group is usually present as a hydroxyl group. These can be synthesized by known methods.

  Furthermore, the cellulose ester used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, Preferably it is 2.5-5.0, More preferably, the cellulose ester of 3.0-5.0 is used preferably.

  The cellulose ester raw material cellulose used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

  For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

The cellulose ester resin of the present invention contains 20 ml of pure water (electric conductivity 0.1 μS / c
m or less, pH 6.8) is charged at 1 g, and when stirred at 25 ° C. for 1 hr in a nitrogen atmosphere, the pH is preferably 6 to 7 and the electrical conductivity is preferably 1 to 100 μS / cm. If the pH is less than 6, the residual organic acid may accelerate cellulose degradation during heating and melting, and if the pH is higher than 7, hydrolysis may accelerate. In addition, when the electrical conductivity is 100 μS / cm or more, since a relatively large amount of residual ions are present, it is considered to be a factor for degrading cellulose during heating and melting.

  The volume specific resistance value of the cellulose ester resin is preferably 1011 to 1015 Ω · cm. Furthermore, 1013 to 1015 Ω · cm is more preferable. Since the cellulose ester resin has high hygroscopicity, it is preferable that the cellulose ester resin be sufficiently dried to remove moisture as much as possible. Further, it is preferable to remove residual organic acid as much as possible. When the volume resistivity is lower than 1011 Ω · cm, the cellulose ester resin may be deteriorated during heating and melting due to the influence of residual organic acid and moisture. Although a molded product of 1015 Ω · cm could not be obtained, it is considered that the higher the volume resistivity value, the more advantageous for deterioration.

  The cellulose ester film of the present invention contains an organic additive in order to add various purposes and functions.

(Organic additives)
The cellulose ester film of the present invention contains an organic additive.

  Organic additives include plasticizers, ultraviolet absorbers, antioxidants, acid scavengers, light stabilizers, retardation control agents, polymer materials, and the like.

  Hereinafter, the additive will be described in more detail.

(Plasticizer)
It is preferable to add a compound known as a plasticizer to the polarizing plate protective film of the present invention from the viewpoint of improving the film, such as improving mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. . Further, in the melt casting method carried out in the present invention, the purpose of lowering the melting temperature of the film constituting material by adding a plasticizer rather than the glass transition temperature of the cellulose ester used alone, or the plasticizer than the cellulose ester at the same heating temperature. The purpose of reducing the viscosity of the film-constituting material containing is included.

  Here, in the present invention, the melting temperature of the film constituent material means a temperature at which the material is heated in a state where the material is heated and fluidity is developed.

  If the cellulose ester alone is lower than the glass transition temperature, the fluidity for forming a film is not exhibited. However, the cellulose ester has a lower elastic modulus or viscosity due to the absorption of heat at a glass transition temperature or higher, and exhibits fluidity. In order to melt the film constituent material, the plasticizer to be added preferably has a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester in order to satisfy the above-mentioned purpose.

  As the plasticizer used in the present invention, for example, phosphate ester derivatives and carboxylic acid ester derivatives are preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 or more and 10,000 or less described in JP-A-2003-12859, a polyester polymer, a polyester polyol polymer, an acrylic polymer, an aromatic ring An acrylic polymer having a side chain or an acrylic polymer having a cyclohexyl group in the side chain is also preferably used.

  For example, as plasticizers, phosphate ester plasticizers, ethylene glycol ester plasticizers, glycerin ester plasticizers, diglycerin ester plasticizers (fatty acid esters), polyhydric alcohol ester plasticizers, dicarboxylic ester esters Examples include plasticizers, polycarboxylic acid ester plasticizers, and polymer plasticizers. Of these, polyhydric alcohol ester plasticizers, dicarboxylic acid ester plasticizers and polycarboxylic acid ester plasticizers are preferred. Further, the plasticizer may be a liquid or a solid, and is preferably colorless due to restrictions on the composition. Thermally, it is preferably stable at a higher temperature, and the decomposition start temperature is preferably 150 ° C. or higher, more preferably 200 ° C. or higher. The addition amount may be as long as the optical properties and mechanical properties are not adversely affected, and the blending amount is appropriately selected within the range not impairing the object of the present invention, and preferably 0.001 with respect to 100 parts by mass of the polymer according to the present invention. -50 mass parts, More preferably, it is 0.01-30 mass parts. 0.1-15 mass% is especially preferable.

  Hereinafter, the plasticizer used in the present invention will be further described. Specific examples are not limited to these examples.

  Phosphate ester plasticizers: specifically, phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclobenthyl phosphate and cyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate And phosphoric acid aryl esters such as cresyl phenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted. Further, it may be a mix of an alkyl group, a cycloalkyl group, and an aryl group, and the substituents may be covalently bonded.

  Also, alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl phosphate) ), Arylene bis (dialkyl phosphate) such as biphenylene bis (dioctyl phosphate), phosphate esters such as arylene bis (diaryl phosphate) such as phenylene bis (diphenyl phosphate) and naphthylene bis (ditoluyl phosphate). These substituents may be the same or different, and may be further substituted. Further, it may be a mix of an alkyl group, a cycloalkyl group, and an aryl group, and the substituents may be covalently bonded.

  Furthermore, the partial structure of the phosphate ester may be part of the polymer or may be regularly pendant, and is introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. May be. Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

  Ethylene glycol ester plasticizer: Specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropyl carboxylate, ethylene glycol dicyclohexyl carboxylate and the like Examples include ethylene glycol cycloalkyl ester plasticizers and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di4-methylbenzoate. These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted. Further, a mixture of alkylate group, cycloalkylate group and arylate group may be used, and these substituents may be covalently bonded. Further, the ethylene glycol part may be substituted, the ethylene glycol ester partial structure may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber, etc. May be introduced into a part of the molecular structure of the additive.

  Glycerin ester plasticizers: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, glycerol cycloalkyl esters such as glycerol tricyclopropyl carboxylate, glycerol tricyclohexyl carboxylate Glyceryl aryl esters such as glycerin tribenzoate and glycerin 4-methylbenzoate, diglycerin tetraacetylate, diglycerin tetrapropionate, diglycerin acetate tricaprylate, diglycerin alkyl esters such as diglycerin tetralaurate, di Diglycerides such as glycerin tetracyclobutylcarboxylate and diglycerin tetracyclopentylcarboxylate Emissions cycloalkyl esters, diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like. These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mix of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the glycerin or diglycerin part may be substituted, and the partial structure of the glycerin ester or diglycerin ester may be part of the polymer or regularly pendant, and may be an antioxidant or an acid scavenger. Or may be introduced into a part of the molecular structure of an additive such as an ultraviolet absorber.

  Polyhydric alcohol ester plasticizer: Specific examples include polyhydric alcohol ester plasticizers described in paragraphs 30 to 33 of JP-A No. 2003-12823.

  These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mix of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the polyhydric alcohol part may be substituted, and the partial structure of the polyhydric alcohol may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber. May be introduced into a part of the molecular structure of the additive.

  Dicarboxylic acid ester plasticizers: Specifically, alkyldocarboxylic acid alkyl ester plasticizers such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), dicyclopentyl succinate, Alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, dihexyl-1,4-cyclohexanedicarboxylate, Cycloalkyldicarboxylic acid alkyl ester plasticizers such as didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutanedicarboxylate, dicyclopropyl-1,2 Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as cyclohexyl dicarboxylate, aryl cycloalkyldicarboxylates such as diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexanedicarboxylate Ester plasticizers, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate and di-2-ethylhexyl phthalate, and aryl dicarboxylic acid cycloalkyls such as dicyclopropyl phthalate and dicyclohexyl phthalate Examples include ester plasticizers and aryl dicarboxylic acid aryl ester plasticizers such as diphenyl phthalate and di4-methylphenyl phthalate. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Further, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

  Polycarboxylic acid ester plasticizers: Specifically, alkyl polycarboxylic acid alkyl ester plastics such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate Agents, alkyl polyvalent carboxylic acid cycloalkyl ester type plasticizers such as tricyclohexyl tricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy-1,2 Alkyl polycarboxylic acid aryl ester plasticizers such as 1,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2,3,4 -Cyclobutane tetracarboxylate, tetrabutyl-1,2, 1,4-cyclopentanetetracarboxylate and other cycloalkyl polycarboxylic acid alkyl ester plasticizers, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl-1,3,5-cyclohexyl Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2,3,4,5,6 -Cycloalkyl polycarboxylic acid aryl ester plasticizers such as cyclohexyl hexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4,5-tetracarboxylate, etc. Aryl polycarboxylic acid Lester ester plasticizer, aryl polyvalent carboxylic acid cycloalkyl ester plasticizer tri such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polycarboxylic acid aryl ester-based plasticizers such as phenylbenzene-1,3,5-tetracartoxylate and hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Can be mentioned. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Further, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

  Polymer plasticizer: Specifically, aliphatic hydrocarbon polymer, alicyclic hydrocarbon polymer, acrylic polymer such as polyethyl acrylate and polymethyl methacrylate, polyvinyl isobutyl ether, poly N-vinyl pyrrolidone, etc. Examples include vinyl polymers, styrene polymers such as polystyrene and poly 4-hydroxystyrene, polybutylene succinates, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes, and polyureas. It is done. The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5,000 to 200,000. If it is 1,000 or less, a problem arises in volatility, and if it exceeds 500,000, the plasticizing ability is lowered, which adversely affects the mechanical properties of the cellulose ester derivative composition. These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination, and other plasticizers, antioxidants, acid scavengers, ultraviolet absorbers, slip agents, matting agents, and the like may be included.

  The addition amount of these compounds is preferably used in the range of 0.5% by mass to less than 50% by mass, more preferably 1% by mass to 30% by mass with respect to the resin in which the plasticizer constitutes the film. %, More preferably in the range of 1% by mass to less than 11% by mass. The addition amount of these compounds can be adjusted from the viewpoint of the above purpose.

  Among the plasticizers, it is generally preferable that no volatile component is generated during heat melting. Specific examples include non-volatile phosphate esters described in JP-A-6-501040. For example, among arylene bis (diaryl phosphate) esters and the above exemplified compounds, trimethylolpropane tribenzoate is preferable. It is not limited. When the volatile component is due to thermal decomposition of the plasticizer, the thermal decomposition temperature Td (1.0) of the plasticizer is higher than the melting temperature of the film-forming material when defined as the temperature at which the mass decreases by 1.0% by mass. Is required. This is because, for the above purpose, the plasticizer is added to the cellulose ester in a larger amount than other film constituent materials, and the presence of the volatile component has a great influence on the quality of the obtained film. The thermal decomposition temperature Td (1.0) can be measured with a commercially available differential thermogravimetric analysis (TG-DTA) apparatus.

  In addition, this invention expands the selection range of the said plasticizer considered generally preferable. That is, when the film constituent material is an integral molded product, the resin and the additive are brought into close contact with each other, and the contact area with air (especially oxygen and water) is reduced. Therefore, it is expected that the melting point of the film forming material and the thermal decomposition temperature of the plasticizer are lower than that of the single material, and the melting point of the film forming material is lowered and the thermal decomposition temperature of the plasticizer is increased. Further, the best mode of film formation according to the present invention is characterized by extruding in a short time at the lowest possible temperature. For example, the thermal decomposition temperature Td (1.0) of the plasticizer is the melting temperature of the film forming material. Even if it is lower, if the value is close to Td (1.0) = melting temperature of the film-forming material to melting temperature of the film-forming material−about 30 ° C., it is inferior to the film quality such as mechanical strength. There is no.

(Antioxidant)
The antioxidant used in the present invention will be described.

  Antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, heat-resistant processing stabilizers, oxygen scavengers, etc. Among them, phenolic antioxidants, particularly alkyl-substituted phenolic compounds Antioxidants are preferred. By blending these antioxidants, it is possible to prevent coloration and strength reduction of the molded product due to heat during molding or oxidative degradation without lowering transparency, heat resistance and the like. These antioxidants can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention, but the polymer 100 according to the present invention. Preferably it is 0.001-5 mass parts with respect to a mass part, More preferably, it is 0.01-1 mass part.

  As antioxidants, hindered phenol antioxidant compounds are known compounds, such as those described in columns 12-14 of US Pat. No. 4,839,405, such as 2, 6-dialkylphenol derivative compounds are included.

  Hindered phenolic antioxidant compounds of the above type are commercially available, for example, from Ciba Specialty Chemicals under the trade names “Irganox 1076” and “Irganox 1010”.

  Specific examples of other antioxidants include phosphorus antioxidants such as trisnonylphenyl phosphite, triphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, and dilauryl-3. , 3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythrityltetrakis (3-laurylthiopropionate), etc. System antioxidant, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5- Di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate 3,4-dihydro-2H-1-benzopyran compound, 3,3′-spirodichroman compound, 1,1-spiroindane compound, morpholine, thiomorpholine, thiomorpholine oxide, described in JP-B-08-27508, Examples thereof include thiomorpholine dioxide, compounds having a piperazine skeleton in the partial structure, oxygen scavengers such as dialkoxybenzene compounds described in JP-A No. 03-174150, and the like. These antioxidant partial structures may be part of the polymer, or may be regularly pendant to the polymer, and introduced into part of the molecular structure of additives such as plasticizers, acid scavengers, and UV absorbers. May be.

(Acid scavenger)
The acid scavenger preferably comprises an epoxy compound as an acid scavenger described in US Pat. No. 4,137,201. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of various polyglycol diglycidyl ethers, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ether of glycerol, metal epoxy compounds (such as those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, diphenols of bisphenol A Glycidyl ether (i.e., 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 4 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (e.g. butyl Epoxy stearate) ), And various epoxidized long chain fatty acid triglycerides and the like (e.g., epoxidized vegetable oils and other unsaturated natural oils, which may be represented and exemplified by compositions such as epoxidized soybean oil, sometimes epoxidized natural) These are referred to as glycerides or unsaturated fatty acids, which generally contain 12 to 22 carbon atoms)). Particularly preferred are the commercially available epoxy group-containing epoxide resin compounds EPON 815c and other epoxidized ether oligomer condensation products.

(Light stabilizer)
Light stabilizers include hindered amine light stabilizer (HALS) compounds, which are known compounds, such as columns 5-11 of US Pat. No. 4,619,956 and US Pat. , 839,405, as described in columns 3 to 5, including 2,2,6,6-tetraalkylpiperidine compounds, or acid addition salts thereof or complexes of them with metal compounds It is.

  These hindered amine light resistance stabilizers can be used alone or in combination of two or more, and used together with these hindered amine light resistance stabilizers and additives such as plasticizers, acid scavengers, and UV absorbers. Alternatively, it may be introduced into a part of the molecular structure of the additive. The blending amount is appropriately selected within a range not impairing the object of the present invention, but is preferably 0.01 to 20 parts by mass, more preferably 0.02 to 15 parts with respect to 100 parts by mass of the polymer according to the present invention. Part by mass, particularly preferably 0.05 to 10 parts by mass.

(UV absorber)
As an ultraviolet absorber, from the viewpoint of preventing deterioration of a polarizer or a display device with respect to ultraviolet rays, the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, it absorbs visible light having a wavelength of 400 nm or more. Less is preferred. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, etc., but benzophenone compounds and less colored benzotriazole compounds preferable. Moreover, you may use the ultraviolet absorber of Unexamined-Japanese-Patent No. 10-182621, Unexamined-Japanese-Patent No. 8-337574, and the polymeric ultraviolet absorber of Unexamined-Japanese-Patent No. 6-148430.

  Specific examples of useful benzotriazole ultraviolet absorbers include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl). ) Benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis ( 4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydro Cis-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy Examples include, but are not limited to, a mixture of -5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate.

  As commercially available products, TINUVIN 109, TINUVIN 171 and TINUVIN 360 (all manufactured by Ciba Specialty Chemicals) can also be used.

  Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy- 5-benzoylphenylmethane) and the like, but are not limited thereto.

  In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and further preferably 1 to 5% by mass. Two or more of these may be used in combination.

(Retardation control agent)
In the cellulose film of the present invention, an alignment film is formed to provide a liquid crystal layer, and the polarizing film processing is performed to improve the liquid crystal display quality by combining the cellulose film and the retardation derived from the liquid crystal layer to provide optical compensation. You may go. As the compound to be added for adjusting the retardation, an aromatic compound having two or more aromatic rings as described in the specification of European Patent 911,656A2 may be used as a retardation control agent. I can do it. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. Particularly preferred is an aromatic heterocycle, and the aromatic heterocycle is generally an unsaturated heterocycle. Of these, a 1,3,5-triazine ring is particularly preferred.

(Polymer material)
In the polarizing plate protective film of the present invention, a polymer material other than cellulose ester or an oligomer may be appropriately selected and mixed. The above polymer materials and oligomers are preferably those having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is 80% or more, more preferably 90% or more, and further preferably 92% or more. The purpose of mixing at least one of polymer materials and oligomers other than cellulose ester includes meanings for controlling viscosity at the time of heating and melting and improving film physical properties after film processing. In this case, it can be included as the above-mentioned other additives.

(Matting agent)
In the cellulose film of the present invention, fine particles such as a matting agent can be added in order to impart slipperiness, and examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound. The matting agent is preferably as fine as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include inorganic fine particles such as magnesium silicate and calcium phosphate, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. In many cases, fine particles such as silicon dioxide are surface-treated with an organic substance, but such particles are preferred because they can reduce the haze of the film.

  Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazane, siloxane and the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average particle size of the secondary particles of the fine particles is in the range of 0.1 to μm. The average particle size of primary particles of preferable fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used in the cellulose ester film in order to produce irregularities of 0.1 to 10 μm on the surface of the cellulose ester film. The content of the fine particles in the cellulose ester is preferably 0.1 to 2.0% by mass with respect to the cellulose ester.

  Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably Aerosil 200V, R972. , R972V, R974, R202, R812. Two or more kinds of these fine particles may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, fine particles 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: 0.1.

  The presence of fine particles in the film used as the matting agent can be used for another purpose to improve the strength of the film. In addition, the presence of the fine particles in the film can improve the orientation of the cellulose ester itself constituting the polarizing plate protective film of the present invention.

(Molded product manufacturing method and size)
As a method for obtaining a pellet-shaped molded product, a rod-shaped strand is obtained by melt extrusion at a temperature of the glass transition temperature of the cellulose ester resin or higher and the melting point + 30 ° C. or lower with a twin-screw extruder, and then the desired size is obtained. The method of cutting is mentioned.

  Since the cellulose ester resin is a material that is significantly deteriorated by heat, a method of molding at a temperature that does not deteriorate is preferable.

In order to obtain the effects of the present invention, the size of the molded product obtained by mixing the cellulose ester resin and the organic additive is in the range of 1 mm × 1 mm × 1 mm to 20 mm × 20 mm × 20 mm cube. It is. In the melt extrusion method, if it is smaller than 1 mm × 1 mm × 1 mm, blocking will occur at the time of molding, and the supply will not be stable. If it is larger than 20 mm × 20 mm × 20 mm, the melting and pulverization properties of the molded product will be poor. There is a risk of clogging at the inlet, resulting in a significant decrease in productivity. On the other hand, if the size is smaller than 1 mm × 1 mm × 1 mm, the specific surface area of the molded product increases, so the contact area with air (especially oxygen and water) also increases, cellulose easily deteriorates, the molecular weight decreases, and the machine There is a risk that the mechanical strength will decrease. In the pressure heating and melting method, if it is larger than 20 mm × 20 mm × 20 mm, it becomes difficult to obtain a film having a small film thickness (100 μm or less). In addition, the film thickness is likely to be uneven. (Thickness accuracy is degraded.)
When formed into a molded product, the resin and the additive are in close contact with each other, so that the mixing / dispersibility is enhanced. Moreover, since the contact area with air (especially oxygen and water) becomes small, it is advantageous also for deterioration of a cellulose.

For example, the cellulose ester and additive mixture of the present invention is hot-air dried or vacuum dried, then melt extruded, extruded into a film form from a T-die, and brought into close contact with a cooling drum by an electrostatic application method, etc., and cooled and solidified. An unstretched film is obtained.
The cellulose ester and additive of the present invention are powders or pellets of about 0.1 to 20 mm. Some raw materials contain a large amount of water and need to be dried. Drying may be performed independently, or may be performed after mixing a plurality of raw materials. The cellulose ester may generate an acid by heating, and decomposition and degradation proceed with this acid. Therefore, it is preferable to dry at about 60 to 90 ° C. so as not to generate an acid. In order to increase the ultimate drying level, it is also preferable to use dry air having a low dew point or to reduce the pressure or vacuum. A preferable dew point is −20 ° C. or lower, more preferably −30 ° C. or lower. Some additives have a low melting point. When drying after mixing, it is necessary to dry below the melting point of the substance with the lowest melting point in the material used so that it does not stick and harden during drying. Of course, it is only necessary to dry the mixture after mixing, but it may absorb moisture during mixing, so it is preferable to dry after mixing.
The dried raw material is immediately sent to the extruder, or stored in a stock tank maintained at a high temperature, low dew point or reduced pressure to prevent moisture absorption, and then sent to the extruder.
As a raw material, it is possible to recover and reuse a loss film that has not been turned into a product after slitting or being wound up. The recovered film is usually pulverized and supplied, but it can be formed into pellets or granulated and supplied. The recovered film also needs to be dried, but may be dried alone, mixed with a virgin polymer raw material, or dried with an additive.

  As the melt extrusion, a single screw extruder, a twin screw extruder, and a tandem extrusion in which two extruders are connected in series can be applied. A die may be installed downstream of the extruder and directly formed by extrusion, or a strand die may be installed and pelletized once, and then the pellet may be extruded and formed.

  Furthermore, it is preferable to replace or depressurize the raw material supply and melting processes such as the raw material tank, the raw material charging section, and the inside of the extruder with an inert gas such as nitrogen gas. In the present invention, in order to mix the cellulose ester and a plurality of additives, pelletization is performed using a twin screw extruder excellent in kneading performance, and then melt extrusion film formation is performed using a single screw extruder having good quantitativeness. Is preferred.

  In particular, a method of heating and melting without giving mechanical stress as much as possible is preferable to pay attention when producing a film. Examples of existing apparatuses include a single screw extruder and a hot press machine. In the case of a single screw extruder, it is desirable to extrude at a low temperature for a short time as long as it can be obtained at a temperature at which a transparent film can be obtained. In the path from the inlet to the die, it is desirable to set the glass transition temperature: Tg to the melting point: Tm + 50 ° C. of the cellulose ester resin, and it is preferable to raise the temperature stepwise as the die is approached. The temperature of the die is preferably set to Tm to Tm + 30 ° C.

  The residence time (extrusion time) is preferably as short as possible. It was preferably 20 to 360 seconds, more preferably 20 to 60 seconds. If the residence time is long, the deterioration may be remarkable, and if it is too short, the melting may be insufficient. The residence time is adjusted by the rotational speed of the shaft, the viscoelasticity of the molded product, the heating temperature, and the like.

  The temperature during the melt extrusion of the present invention is preferably in the range of Tg + 50 ° C. or more and Tg + 150 ° C. or less of cellulose.

A gear pump and a filter are preferably arranged downstream of the extruder. Since the gear pump can convey the molten resin quantitatively, it can be preferably applied to make the film thickness of the take-up film uniform. A filter for protecting the gear pump is preferably disposed immediately before the gear pump. The gear pump includes a 2-gear type and a 3-gear type, but a 3-gear type with better quantitativeness is preferable. A main filter is arranged downstream of the gear pump. The main filter reduces foreign matter in the product film and improves product quality.
The die is preferably a T die. A lip gap adjusting mechanism such as a push-pull bolt, lip heater, or heat bolt is provided to adjust the film thickness uniformly. In order to make the lip less likely to be damaged, it is also preferable to perform plating or ultrahard processing such as diamond-like carbon. The discharge direction may be horizontal or vertical. It is also possible to apply a discharge obliquely downward in accordance with the take-up roll.
For taking out the discharged molten film, a method in which it is brought into close contact with a cooling drum by an electrostatic application method or the like, or a method in which a molten film is sandwiched between two rolls is preferably applied. The temperature of the cooling drum is preferably maintained at Tg-100 to Tg of the cellulose ester. It is preferable to suck the atmosphere around the cooling drum and the take-up roll from the die outlet. This is to prevent additives such as polymer degradation products and plasticizers from evaporating from the melt-extruded film and adhering to the die lip or roll. The suction is preferably set immediately after the resin is discharged from the die lip. It is also preferable to surround the periphery in order to increase the effect of removing volatile gas. If the air is enclosed and sucked, the resin film discharged from the die lip may fluctuate due to air being sucked in from the surroundings through the gap, so the same amount of fresh air as the amount of suction air is supplied into the enclosure. It is also preferable. If the temperature of the supplied air fluctuates, the temperature of the resin film changes to cause film thickness unevenness. Therefore, the temperature is preferably controlled to be constant. Even if such measures are taken, it is not possible to completely eliminate roll contamination due to volatile gas from the molten film. Therefore, it is preferable to install a cleaning device on the take-up roll or the cooling drum. The cleaning device can be applied to either a type that functions continuously during film formation or a type that functions by interrupting film formation periodically.
The cellulose ester film for a polarizing plate protective film of the present invention is particularly preferably a film stretched in the width direction or the film forming direction.

  The unstretched film peeled off from the cooling drum described above is heated within a range of Tg + 100 ° C. from the glass transition temperature (Tg) of the cellulose ester via a heating device such as a plurality of roll groups and / or an infrared heater, It is preferable to perform single-stage or multistage longitudinal stretching. The draw ratio is selected in a range of 5 to 200% so as to satisfy the retardation required for the product.

  Next, the cellulose ester film stretched in the machine direction obtained as described above is stretched in the range of 5 to 200% within the temperature range of Tg−20 ° C. to Tg + 20 ° C., and then heat-set. It is preferable.

  In the case of transverse stretching, it is preferable to perform transverse stretching while sequentially raising the temperature difference in the range of 1 to 50 ° C. in a stretching region divided into two or more, because the distribution of physical properties in the width direction can be reduced. Further, after the transverse stretching, it is preferable that the film is kept at a temperature of Tg-40 ° C. or higher at a temperature equal to or lower than the final transverse stretching temperature for 0.01 to 5 minutes because the physical property distribution in the width direction can be further reduced. The order of stretching is not limited to the order of length and width, but may be the order of width and length.

  Simultaneous biaxial stretching can also be preferably applied. In sequential stretching, there is a tendency to break easily at the second stage stretching, but simultaneous biaxial stretching has a merit that the vertical and horizontal orientations can be made uniform without being easily broken.

  The heat setting is performed at a temperature higher than the final transverse stretching temperature and usually within 0.5 to 300 seconds within a temperature range of Tg + 50 ° C. or less. At this time, it is preferable to heat-fix while sequentially raising the temperature difference in the range of 1 to 100 ° C. in the region divided into two or more.

  The heat-set film is usually cooled to Tg or less, and clip holding portions at both ends of the film are cut and wound. Under the present circumstances, it is preferable to carry out a relaxation | loosening process 0.1 to 10% in a horizontal direction and / or a vertical direction within the temperature range below Tc-30 degreeC or less at the last heat setting temperature. Further, the cooling is preferably performed by gradually cooling from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to carry out these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film. The cooling rate is a value obtained by (T1−Tg) / t, where T1 is the final heat setting temperature and t is the time until the film reaches Tg from the final heat setting temperature.

  More optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the cellulose ester constituting the film, so the physical properties of the obtained biaxially stretched film should be measured and adjusted appropriately to have desirable characteristics. It may be determined by.

  In the film forming process, the clip gripping portions at both ends of the cut film are pulverized or granulated as necessary, and then used as a raw material for the same type of film or for different types of film. It may be reused as a raw material.

(Stretching operation, refractive index control)
When the polarizing plate protective film of the present invention is used as a retardation film, the refractive index can be controlled by a stretching operation. As the stretching operation, the refractive index is controlled within a preferable range by stretching 1.0 to 2.0 times in one direction of the cellulose ester and 1.01 to 2.5 times in the direction perpendicular to the film plane. I can do it.

  For example, the film can be stretched sequentially or simultaneously in the longitudinal direction of the film and the direction perpendicular to the longitudinal direction of the film, that is, the width direction. At this time, if the stretching ratio in at least one direction is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and breakage may occur.

  For example, when the film is stretched in the direction of melting and casting, if the contraction in the width direction is too large, the refractive index in the thickness direction of the film becomes too large. In this case, the width shrinkage of the film can be suppressed or improved by stretching in the width direction. When stretching in the width direction, the refractive index may be distributed with a width. This is sometimes seen when the tenter method is used, but it is a phenomenon that occurs when the film is stretched in the width direction, causing contraction force at the center of the film and the ends being fixed. It is thought to be called a phenomenon. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed, and the distribution of the width retardation can be reduced.

  Furthermore, the film thickness fluctuation | variation of the film obtained can be reduced by extending | stretching in the biaxial direction orthogonal to each other. If the film thickness variation of the polarizing plate protective film is too large, the retardation will become uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

  The film thickness variation of the cellulose ester film support is preferably in the range of ± 3%, more preferably ± 1%. For the purposes as described above, the method of stretching in the biaxial directions perpendicular to each other is effective, and the stretching ratio in the biaxial directions perpendicular to each other is finally 1.0 to 2.0 times in the casting direction. The width direction is preferably 1.01 to 2.5 times, the casting direction is 1.01 to 1.5 times, and the width direction is 1.05 to 2.0 times. preferable.

  When cellulose ester that obtains positive birefringence with respect to stress is used, the slow axis of the polarizing plate protective film can be provided in the width direction by stretching in the width direction. In this case, in the present invention, in order to improve display quality, the slow axis of the polarizing plate protective film is preferably in the width direction, and (stretch ratio in the width direction)> (stretch ratio in the casting direction) It is necessary to satisfy.

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

  It is preferable to perform the width maintenance or the transverse stretching in the film forming process by a tenter, and it may be a pin tenter or a clip tenter.

  As for the thickness of the polarizing plate protective film of this invention, 10-500 micrometers is preferable. In particular, it is preferably 20 μm or more, and more preferably 35 μm or more. Further, it is preferably 150 μm or less, more preferably 120 μm or less. Most preferably, it is 25 or more and 90 micrometers. If the polarizing plate protective film is thicker than the above-mentioned region, the polarizing plate after polarizing plate processing becomes too thick, so that it is not suitable for a thin and lightweight purpose in a liquid crystal display used for a notebook computer or a mobile electronic device. On the other hand, if it is thinner than the above-mentioned region, it is not preferable because it becomes difficult to develop retardation, the moisture permeability of the film becomes high, and the ability to protect the polarizer from humidity decreases.

When the slow axis or the fast axis of the polarizing plate protective film of the present invention is present in the film plane and the angle formed with the film forming direction is θ1, θ1 is preferably −1 ° or more and + 1 ° or less, − More preferably, it is 0.5 ° 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.

(Functional layer)
In producing the polarizing plate protective film of the present invention, before and / or after stretching, an antistatic layer, a hard coat layer, an antireflection layer, a slippery layer, an easy adhesion layer, an antiglare layer, a barrier layer, an optical compensation layer, etc. The functional layer may be provided. In particular, it is preferable to provide at least one layer selected from an antistatic layer, a hard coat layer, an antireflection layer, an easy adhesion layer, an antiglare layer, and an optical compensation layer. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.

(Polarizer)
The manufacturing method of the polarizing plate which has a polarizing plate protective film of this invention is not specifically limited, It can manufacture by a general method. The obtained polarizing plate protective film was treated with an alkali, and a polyvinyl alcohol film was immersed and stretched in an iodine solution, using a completely saponified polyvinyl alcohol aqueous solution on both sides of the polarizer, and polarizing plate protective films on both sides of the polarizer. There is a method of bonding, and at least one side is preferable from the viewpoint that the polarizing plate protective film of the present invention can be directly bonded to the polarizer.

  Further, instead of the alkali treatment, easy-adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be applied to perform polarizing plate processing.

  The polarizing plate is composed of a polarizer and a protective film for protecting both surfaces of the polarizer, and can further be constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the adhesive layer bonded to a liquid crystal plate, and is used on the surface side which bonds a polarizing plate to a liquid crystal cell.

(Liquid crystal display device)
In a liquid crystal display device, a substrate containing a liquid crystal is usually disposed between two polarizing plates. However, excellent display properties can be obtained regardless of the location of the cellulose film of the present invention. In particular, since a clear hard coat layer, an antiglare layer, an antireflection layer, and the like are provided on the polarizing plate protective film on the display side outermost surface of the liquid crystal display device, the polarizing plate protective film is preferably used in this portion. The stretched polarizing plate protective film of the present invention is also preferably used as a retardation film for widening the viewing angle.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited to these.

Example 1
As cellulose, cellulose acetate propionate (A): 100 parts by mass with a total substitution degree of 2.6, an acetyl substitution degree of 1.9, a propionyl substitution degree of 0.7, and a weight average molecular weight of 190,000 was used.
As additives, trimethylolpropane tribenzoate (B): 10 parts by mass, polyester polyol (C) described in Synthesis Example 1 described later: 3 parts by mass, Irganox 1010 (D): 0.5 parts by mass, ADK STAB LA52 (E): 0.25 parts by mass were used.
(Synthesis Example 1)
A reactor equipped with a cooling condenser is charged with 648 parts by weight of ethylene glycol, 58 parts by weight of diethylene glycol, 1121 parts by weight of succinic acid, 83 parts by weight of terephthalic acid, 0.03 parts by weight of tetrabutyl titanate, A dehydration condensation reaction was carried out at 140 ° C. for 2 hours and at 220 ° C. for 2 hours, and the cooling condenser was removed and further at 220 ° C. for 20 hours to obtain a polyester polyol (C) having a number average molecular weight of 1500.

  (A) was dried under reduced pressure at 80 ° C. for 24 hours, kept at 80 ° C., and stored in a storage tank in which dehumidified air was circulated. (B), (C), (D), and (E) are pulverized and aligned through a 0.5 mm sieve, and then weighed each mass and mixed with a V-type blender. It was fed and dried at 60 ° C. for 24 hours under normal pressure. Let this mixed composition be (F).

  (A) was quantitatively supplied from a storage tank via a hopper to a twin screw extruder (screw diameter: 40 mm, L / D: 50, rotating in the same direction) with a screw feeder. At this time, the hopper and the screw feeder were kept at 80 ° C. and purged with dehumidified air so that the material did not absorb moisture. (F) was supplied to the same supply port that supplied (A) with a screw feeder so that it might be 13.75 mass parts of (F) with respect to 100 mass parts of (A). At this time, the hopper and the screw feeder were kept at 60 ° C. and purged with dehumidified air so that the material did not absorb moisture.

In the twin screw extruder, the raw material supply unit was water-cooled, and L / D: 10 zones were set to 240 ° C., 250 ° C., 250 ° C., 250 ° C., and 240 ° C. in order from the downstream.
The reusable raw material obtained by pulverizing the edge portion slit at the time of film formation was melt-side fed from another twin screw extruder at a position of L / D: 30 from the root of the twin screw extruder.

  After melt extrusion from the twin screw extruder, it is guided to the die through the prefilter, gear pump and main filter. The prefilter was a 200 mesh metal fiber filter, the gear pump was a 3 gear type, and the main filter was a 400 mesh metal fiber filter. The temperature settings were: prefilter: 250 ° C., gear pump: 250 ° C., main filter: 260 ° C. The die was a coat hanger type T die with a slit gap of 300 μm and a temperature setting of 250 ° C. A static mixer was placed between the main filter and the die.

  The resin sheet extruded from the die was picked up by sandwiching it between super mirror chrome plating rolls adjusted to 80 ° C. A suction nozzle was installed in the space between the die and the roll, and the volatile gas generated from the resin sheet was removed by suction. The raw material supply amount to the extruder, the number of revolutions of the extruder, and the number of revolutions of the take-up roll were adjusted so that the thickness of the taken resin sheet was 133 μm.

Coating liquid Cellulose polymer (A): 1 part by mass and silica particles (Aerosil R972V): 1 part by mass were dissolved and dispersed in 100 parts by mass of methylene chloride to prepare a coating liquid.

  As shown in FIG. 1, on both sides of the taken sheet, first, it is coated on the upper surface with an extrusion coater, dried in a drying zone, reversed and coated with the coating liquid on the opposite surface with the same extrusion coater, and used as a tenter for stretching. After being guided and dried, it was continuously stretched. The coating liquid amount was adjusted so that the film thickness after drying and stretching was 1 μm on both sides. Stretching was carried out by holding both ends of the film with a clip type tenter, passing through a preheating zone after drying the coating liquid, raising the film temperature to 150 ° C., and stretching the film by 30% at the same time. The film temperature was measured on both sides with a non-contact infrared thermometer. The film is transported while being kept at 150 ° C. for 10 seconds after the end of stretching, and then gradually cooled. After the film surface temperature becomes 50 ° C. or less, the film is released, slit at the edge, and knurled at both ends. From winder. As described above, the slit edge portion was pulverized and supplied to the extruder again. The film thickness of the obtained film was 80 μm.

Example 2
The same raw material as in Example 1 was extruded in the same manner to prepare a raw sheet, and then stretched 30% in the vertical direction using the difference in peripheral speed of the roll, and then the same coating liquid and coating method as in Example 1 After coating on both sides, the film was stretched 30% in the horizontal direction with a tenter and wound up in the same manner as in Example 1.

Example 3
A raw material sheet similar to that of Example 1 was extruded in the same manner to prepare a raw sheet, which was then led to a tenter and stretched 30% at the same time in the vertical and horizontal directions to prepare a film. The number of revolutions of the extruder and the take-up speed were adjusted so that the thickness of the obtained film was 78 μm. The coating liquid used in Example 1 was applied to both sides of the produced film by extrusion coater on both sides so that the film thickness after drying was 1 μm.

Comparative Example 1
In the same manner as in Example 1, however, the film was wound up by being stretched to a film thickness of 80 μm without applying the coating solution after forming the extruded sheet.

  Next, for each of the cellulose films of Examples 1 to 3 and Comparative Example 1 according to the present invention, the bleed out from the film, the moisture permeability of the film, and the liquid crystal display visibility were evaluated, and the obtained results were as follows. Table 1 summarizes the results.

(Evaluation of film bleed-out)
For each of the cellulose films of Examples 1 to 3 and Comparative Example 1 according to the present invention, a bleed-out evaluation test was performed as follows.

Here, as a bleed-out evaluation method, bleed-out is performed by leaving a sheet-fed film obtained by cutting a wound film into a length of 1 m for 300 hours under an environmental condition of a temperature of 60 ° C. and a humidity of 90% RH, and then blacking out. Under the white light of a fluorescent lamp
It was observed visually. Depending on the frequency of occurrence, ◯, Δ, and × were graded.

(Evaluation of moisture permeability of film)
About each cellulose film of Examples 1-3 of this invention and Comparative Example 1, it is 24 in the untreated state (reference | standard state) after manufacture, and the environmental conditions of temperature 23 degreeC and humidity 80% RH based on a calcium chloride-cup method. The moisture permeability (g / m ² ) after time was measured.

(Evaluation of liquid crystal display visibility)
The polarization characteristics of the cellulose films of Examples 1 to 3 and Comparative Example 1 of the present invention were evaluated. Here, as a method for evaluating polarization characteristics, a film was used as a protective film for a polarizing plate, a polarizing plate was prepared from the film according to a conventional method, and further used for a liquid crystal display. The image obtained on the liquid crystal display is observed visually, and the visibility of the image
◎, ○, △, and × were graded. The results are shown below.

  It can be seen that the sample of the present invention is superior in all purification items as compared with the comparison.

It is the schematic which shows an example coated and dried with the coating liquid which has a cellulose-ester resin on the cellulose-ester film obtained by the melting method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,22 Dryer 2,23 Storage tank 3,4 Hopper 5,6 Screw feeder 7 Supply port 8,24 Twin screw extruder 9,25 Prefilter 10 Gear pump 11 Main filter 12 Die 13 Take-off roll 14,16 Coating device 15 Drying zone 17 Tenter 18 Winder 19 Grinding 20 Weighing 21 Mixing

Claims (14)

An optical cellulose ester for display, wherein a cellulose ester resin-containing coating solution is formed on one or both sides of a cellulose ester film formed by a T-die melt extrusion method and dried. A method for producing a film. 2. The method for producing an optical cellulose ester film for display according to claim 1, wherein a coating liquid containing a cellulose ester resin is coated on both sides of the cellulose ester film formed by the T-die melt extrusion method and dried. The method for producing an optical cellulose ester film for display according to claim 1 or 2, wherein the organic additive is a plasticizer. The method for producing an optical cellulose ester film for display according to any one of claims 1 to 3, wherein the coating liquid contains inorganic fine particles. 5. The optical cellulose for display according to claim 4, wherein the number average particle diameter of the inorganic fine particles in the coating solution is 0.1 to 10.0 μm, and the content is 0.1 to 2 mass%. A method for producing an ester film. The method for producing an optical cellulose ester film for display according to any one of claims 1 to 5, wherein the cellulose ester resin is cellulose acetate propionate. The method for producing an optical cellulose ester film for display according to claim 6, wherein the cellulose acetate propionate has a propionyl substitution degree of 0.1 to 2. The coating solution containing a cellulose ester resin is applied to a cellulose ester film formed by a T-die melt extrusion method, dried, and then stretched in at least a uniaxial direction to produce the coating solution. The manufacturing method of the optical cellulose-ester film for a display of claim | item. The cellulose ester film formed by a T-die melt extrusion method is stretched in a uniaxial direction, and then the coating solution is applied and dried on the cellulose ester film. Of producing an optical cellulose ester film for display. The method for producing an optical cellulose ester film for display according to any one of claims 1 to 9, wherein the temperature for molding by a T-die melt extrusion method is Tg + 50 ° C to Tg + 150 ° C of cellulose. The method for producing an optical cellulose ester film for display according to any one of claims 1 to 10, wherein the optical cellulose ester film for display has a thickness of 20 to 150 µm. It is obtained with the manufacturing method of the optical cellulose-ester film for a display of any one of Claims 1-11, The optical cellulose-ester film for a display characterized by the above-mentioned. A polarizing plate using the optical cellulose ester film for display according to claim 12 on at least one surface. A liquid crystal display device, wherein the optical cellulose ester film for display according to claim 12 or the polarizing plate according to claim 13 is disposed in a liquid crystal cell.

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