JP2007063310A - Cellulose ester film, its production method, optical film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film reduced in a production load and an equipment load involved in solvent drying and recovery and being excellent in optical properties, to provide its production method, to provide an optical film, to provide a polarizing plate using the optical film as an excellent polarizing plate protective film having a small dispersion of retardation especially in the width direction, and to provide a liquid crystal display device using the polarizing plate. <P>SOLUTION: The cellulose ester film is characterized by containing at least one compound having an e value in the range: e<-0.8 as determined by the Q-e method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cellulose ester film formed by melt casting, a production method thereof, an optical film, a polarizing plate using the optical film as a polarizing plate protective film, and a liquid crystal display device using the polarizing plate.

  Liquid crystal display devices (LCDs) can be directly connected to IC circuits with low voltage and low power consumption, and can be made particularly thin, so displays such as word processors, personal computers, televisions, monitors, and portable information terminals Widely adopted as a device. The basic configuration of this LCD is, for example, that polarizing plates are provided on both sides of a liquid crystal cell.

  By the way, the polarizing plate allows only light of a polarization plane in a certain direction to pass through. Accordingly, the LCD plays an important role in visualizing the change in the orientation of the liquid crystal due to the electric field. That is, the performance of the LCD is greatly influenced by the performance of the polarizing plate.

  The polarizer of the polarizing plate is obtained by adsorbing and stretching iodine or the like on a polymer film. That is, after a solution called H ink containing a dichroic substance (iodine) was wet-adsorbed on a polyvinyl alcohol film, the dichroic substance was oriented in one direction by stretching the film uniaxially. Is. As a protective film for the polarizing plate, a cellulose resin, particularly cellulose triacetate is used.

  Cellulose ester films are widely used because they are optically and physically useful as protective films for polarizing plates. However, since the film production method is a production method based on a casting film production method using a halogen-based solvent, the cost required for solvent recovery has been a very heavy burden. Therefore, a variety of solvents other than halogen-based solvents were tested, but there was no substitute that provided satisfactory solubility. In addition to seeking an alternative solvent, a new dissolution method such as a cooling method has also been tried (see, for example, Patent Document 1), but industrial realization is difficult and further studies are required.

  Further, a technique for improving spectral characteristics and mechanical characteristics by adding a hindered phenol antioxidant, a hindered amine light stabilizer, and an acid scavenger to the cellulose ester at a certain addition ratio is disclosed (for example, (See Patent Document 2). A technique using a polyhydric alcohol ester plasticizer as a plasticizer (for example, see Patent Document 3), and a technique for limiting the polyhydric alcohol ester plasticizer to a specific structure (for example, see Patent Document 4) are also disclosed. Has been. Further, as a technique for preventing the deterioration of organic materials, a stabilizer composition containing various stabilizers and phosphites is known (for example, see Patent Document 5).

  In any case, the optical cellulose ester film has a production load and equipment load associated with the use of a solvent in the production process, and the optical properties and mechanical properties are insufficient.

In recent years, attempts have been made to melt-form cellulose esters for silver salt photography (for example, see Patent Document 6) or deflector protective films (for example, see Patent Document 7). It is a polymer with a very high viscosity at the time of melting, and also has a high glass transition temperature, so that it is difficult to level even if the cellulose ester is melted and extruded from a die and cast on a cooling drum or cooling belt. Because it solidifies in a short time, the solution cast film has flatness and curl properties, which are the physical properties of the film obtained, and also dimensional stability, retardation uniformity which is an optical property, particularly retardation uniformity in the width direction of the film It became clear that it had the subject of being lower than.
Japanese Patent Laid-Open No. 10-95861 JP 2003-192920 A JP 2003-12823 A JP 2003-96236 A Japanese Patent Laid-Open No. 11-222493 Japanese National Patent Publication No. 6-501040 JP 2000-352620 A

  An object of the present invention is to reduce the production load and equipment load associated with drying and recovery of a solvent, and a cellulose ester film excellent in optical properties, a method for producing the same, an optical film, and dispersion of retardation in the width direction, in particular. It is providing the polarizing plate used as an excellent polarizing plate protective film with few, and a liquid crystal display device using the polarizing plate.

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

  (1) A cellulose ester film containing at least one compound having an e value of e <−0.8 according to the Qe method.

  (2) The cellulose ester film as described in (1) above, wherein the compound having an e value by Qe method of e <−0.8 has at least one aromatic ring.

  (3) In the cellulose ester film, at least one selected from a phenol-based stabilizer, a hindered amine-based stabilizer, a phosphorus-based stabilizer, and a sulfur-based stabilizer is 0.01 to 100 parts by mass with respect to 100 parts by mass of the cellulose ester. The cellulose ester film as described in (1) or (2) above, comprising 5 parts by mass.

  (4) The cellulose ester in the cellulose ester film is at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. The cellulose ester film according to any one of (1) to (3), wherein:

  (5) Containing at least one of an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monovalent alcohol. The cellulose ester film according to any one of the items (4) to (4).

  (6) The ester plasticizer comprising the polyhydric alcohol and the monovalent carboxylic acid, and the ester plasticizer comprising the polyhydric carboxylic acid and the monovalent alcohol are an alkyl polyhydric alcohol aryl ester and a dialkylcarboxylic acid alkyl ester, respectively. The cellulose ester film as described in (5) above, wherein

  (7) An optical film using the cellulose ester film described in any one of (1) to (6) above.

  (8) A polarizing plate using the optical film according to the item (7) on at least one surface.

  (9) A liquid crystal display device using at least one of the optical film described in the item (7) and the polarizing plate described in the item (8).

  (10) At least one of a cellulose ester, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, or an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol, and an e value according to the Qe method A mixture comprising at least one compound containing at least one compound of which e <−0.8 is heated and melted at a melting temperature (Tm) of 150 ° C. or higher and 300 ° C. or lower, and melt-cast A method for producing a cellulose ester film to be obtained, wherein the added amount of the plasticizer and a compound containing at least one compound having an e value of e <−0.8 according to the Qe method is respectively relative to the cellulose ester. The manufacturing method of the cellulose-ester film characterized by being 1-30 mass% and 0.01-10 mass%.

  According to the present invention, the production load and equipment load associated with the drying and recovery of the solvent are reduced, and the cellulose ester film excellent in optical properties and the production method thereof, the optical film, and the retardation of the optical film in particular in the width direction are small. A polarizing plate used as an excellent polarizing plate protective film and a liquid crystal display device using the polarizing plate could be provided.

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

  The cellulose ester film of the present invention (hereinafter sometimes referred to as an optical film) is characterized by containing at least one compound having an e value of e <−0.8 according to the Qe method.

  The solution casting method, which is one of the methods for producing a cellulose ester film, is to form a film by casting a solution in which a cellulose ester is dissolved in a solvent, evaporating and drying the solvent, and this method remains inside the film. Since the solvent to be removed must be removed, the capital investment and production costs for the production line such as the drying line, drying energy, and the recovery and recycling equipment for the evaporated solvent are enormous, and it is important to reduce them. It is a difficult issue.

  On the other hand, in the film formation by the melt casting method, the solvent for adjusting the cellulose ester solution is not used as the solution casting, so that the above-described drying load and equipment load do not occur.

  Further, when an undried cellulose ester is formed into a film by the melt casting method, fine foaming occurs at the time of molding, so that optical properties such as haze, transmittance, and retardation are deteriorated. When melt casting is carried out using the cellulose ester preferred in the present invention, the water content is reduced, no haze is generated, the optical properties are improved, and an ester plastic comprising a polyhydric alcohol used as a plasticizer and a monovalent carboxylic acid. An ester plasticizer comprising an agent or a polyvalent carboxylic acid and a monohydric alcohol has a high affinity with a cellulose ester, and as a result, improves optical properties and mechanical properties as a cellulose ester film.

  In addition, when a cellulose ester film is produced by the melt casting method by containing at least one compound having an e value of e <−0.8 according to the Qe method according to the present invention, it is surprisingly wide. It was found that the retardation of was uniform. The combined use of primary antioxidants typified by hindered phenols and secondary antioxidants typified by sulfur compounds, phosphite compounds, and hindered amines is known as a means of suppressing heat and photodegradation of polymer compounds. However, when at least one compound having an e value of e <−0.8 according to the Qe method was used this time, surprisingly good haze was exhibited.

  Further, when the cellulose ester film is produced by the above-mentioned solution casting method, bright spot foreign matter is generated. On the other hand, when the cellulose ester film is produced by the melt casting method, the number of bright spot foreign matter is reduced. Is done.

  The melt casting in the present invention is defined as melt casting in which a cellulose ester is heated and melted to a temperature exhibiting fluidity without using a solvent, and then the fluid cellulose ester is cast. More specifically, the heating and melting molding method can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, and a stretch molding method. Among these, in order to obtain an optical film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent. Here, after the film constituent material is heated to express its fluidity, it is included in the method for producing a cellulose ester film of the present invention as a melt casting film forming method by extrusion film formation on a drum or an endless belt. It is.

  The concept of the Qe method referred to in the present invention represents the concept of calculating copolymerization from the degree of stabilization and polarity due to resonance of a vinyl monomer. This concept was developed by T. Alfred Jr. , C.I. C. Prince is J. Polymer. Sci. 2, 101 (1947). These values are empirical analysis methods and are not a clear theory of physical meaning, but can be expressed numerically by vinyl group electron density, substituent conjugation, non-conjugation, and size. .

That is, it is suggested that the reactivity of the monomer in the copolymerization is largely governed by the resonance stability of the monomer and radicals generated therefrom and the difference in polarity between the monomer and the generated radical. Alfredy and Prince have empirically proposed the Q and e schemes taking into account the resonance and polarity terms. That is, the reactivity of the monomer in copolymerization is expressed by the following formulas (1) and (2).
Formula _{(1) R 1 = k 11} / K 12 = (Q 1 / Q 2) exp [-e 1 (e 1 -e 2)]
Equation _{(2) R 2 = k 22} / K 21 = (Q 2 / Q 1) exp [-e 2 (e 2 -e 1)]
It was expressed. Here, the subscripts 1 and 2 relate to the monomers 1 and 2, Q is a term related to the monomer conjugation scale, and e is a polar term. Q and e are not absolute values but expressed as relative values based on styrene. In Alfredy and Prince, Q of styrene was 1 and e was -0.8. Q is large for conjugated monomers such as styrene and methyl methacrylate, and Q is small for conjugated monomers such as vinyl acetate and vinyl chloride. In addition, e of a monomer having an electron-withdrawing substituent such as acrylate ester or acrylonitrile is positive, and e of a monomer having an electron-donating substituent such as vinyl ether is negative. In the Q and e schemes, from (Formula 1) and (Formula 2),
Formula (3) In (r ₁ r ₂ ) = − e ₁ (e ₁ −e ₂ ) −e ₂ (e ₂ −e ₁ ) = − (e ₁ −e ₂ ) ₂
It becomes. That is, (Equation 3) indicates that alternating copolymerization tends to occur in the copolymerization of the combination of monomers 1 and 2 having a large difference in polarity, and the alternation of the produced copolymer increases. Q and e values of various monomers are obtained from experimental values of r1 and r2. For example, Polymer Handbook 3rd edition (II / 267) and L. J. et al. Yong, J. et al. Polym. Sci. , 54, 411 (1961) and J.A. Brandrup et al., “Polymer Handbook,” interscience (1974). The compound used in the present invention may be a compound in which the e value described in the above-mentioned document is e <−0.8, and the compound in which e <−0.8 has at least one aromatic ring. It is preferable to have. Specific examples include the following compounds, but the present invention is not limited thereto.

  The compound of the present invention may be pendant to a monomer, dimer, trimer, tetramer, oligomer or polymer, and there is no particular molecular weight limitation. The addition amount is 0.01 to 30 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the cellulose ester.

  Moreover, the vinyl-type monomer structure site | part should just exist in a cellulose ester, and you may make it couple | bond with the hydroxyl group which remains in a cellulose ester by a covalent bond through a spacer.

(Stabilizer)
In the cellulose ester film of the present invention, in addition to a compound having an e value by Qe method of e <−0.8, among phenol-based stabilizer, hindered amine-based stabilizer, phosphorus-based stabilizer, and sulfur-based stabilizer. At least one selected from the above, or two or more stabilizers may be additionally added. By appropriately selecting these stabilizers and adding them to the cellulose ester in combination with a compound having an e value of e <−0.8 according to the Qe method, a cellulose ester film excellent in optical properties, particularly in the width direction. An excellent polarizing plate protective film can be obtained with little variation in retardation.

  As a preferable phenol-based stabilizer, conventionally known ones can be used, for example, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2 , 4-di-t-amyl-6- (1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate and the like, and JP-A Nos. 63-179953 and 1-168643. Acrylate compounds described in Japanese Patent Publication No. 1; octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis (4-methyl-6-tert-butylphenol) ), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3 5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenylpropionate) methane), ie pentaerythrmethyl -Tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenylpropionate)), triethylene glycol-bis (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate ) And the like; 6- (4-hydroxy-3,5-di-t-butylanilino) -2,4-bisoctylthio-1,3,5-triazine, 4-bisoctylthio-1 , 3,5-triazine, 2-octylthio-4,6-bis- (3,5-di-t-butyl-4-oxyanilino) -1,3,5-triazi Triazine group-containing phenol compounds, such as and the like.

  Preferred hindered amine stabilizers include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) succinate, bis (1 , 2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (N-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-benzyloxy-2,2) , 6,6-tetramethyl-4-piperidyl) sebacate, bis (N-cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6- Pentamethyl-4-piperidyl) 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1-acryloyl-2,2,6, -Tetramethyl-4-piperidyl) 2,2-bis (3,5-di-t-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1,2,2,6,6-pentamethyl- 4-piperidyl) decandioate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -1 -[2- (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy) ethyl] -2,2,6,6-tetramethylpiperidine, 2-methyl-2- (2, 2,6,6-tetramethyl-4-piperidyl) amino-N- (2,2,6,6-tetramethyl-4-piperidyl) propionamide, tetrakis (2,2,6,6-tetramethyl-4 -Piperi Le) 1,2,3,4-butane tetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, and the like.

  The phosphorus stabilizer is not particularly limited as long as it is usually used in the general resin industry. For example, triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl). ) Phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9, Monophosphite compounds such as 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecylphos Phyto), 4,4'-isopropylidene-bis (phenyl-di-alkyl (C12-C15) phos Aito) and the like diphosphite compounds such as. Among these, monophosphite compounds are preferable, and tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite and the like are particularly preferable.

  More preferred sulfur stabilizers include, for example, dilauryl 3,3-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3-thio Dipropionate, pentaerythritol-tetrakis (β-lauryl-thio-propionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane, etc. Can be mentioned.

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

IRGANOX 1010: TINUVIN 770 manufactured by Ciba Specialty Chemicals Inc. TINUVIN 144 manufactured by Ciba Specialty Chemicals Co., Ltd. ADK STABLA LA-52 manufactured by Ciba Specialty Chemicals Inc. Sumilezer GP manufactured by Asahi Denka Kogyo PEP 24G: manufactured by Asahi Denka Kogyo Co., Ltd. Sumilezer TP-D: manufactured by Sumitomo Chemical Co., Ltd. These stabilizers can be used singly or in combination of two or more, and the blending amount impairs the object of the present invention. The amount is appropriately selected within a range of 0.001 to 10.0 parts by mass, preferably 0.01 to 5.0 parts by mass, and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the cellulose ester. 0.0 part by mass.

(Cellulose ester)
The cellulose ester according to the present invention is the above-mentioned single or mixed acid ester of cellulose containing at least one structure among a fatty acyl group and a substituted or unsubstituted aromatic acyl group.

In the aromatic acyl group, when the aromatic ring is a benzene ring, examples of the substituent of the benzene ring include halogen atom, cyano, alkyl group, alkoxy group, aryl group, aryloxy group, acyl group, carbonamido group, sulfone. Amido group, ureido group, aralkyl group, nitro, alkoxycarbonyl group, aryloxycarbonyl group, aralkyloxycarbonyl group, carbamoyl group, sulfamoyl group, acyloxy group, alkenyl group, alkynyl group, alkylsulfonyl group, arylsulfonyl group, alkyloxy Sulfonyl group, aryloxysulfonyl group, alkylsulfonyloxy group and aryloxysulfonyl group, -S-R, -NH-CO-OR, -PH-R, -P (-R) ₂ , -PH-O-R, -P (-R) (-O-R), -P ( _{O-R) 2, -PH (} = O) -R-P (= O) (- R) 2, -PH (= O) -O-R, -P (= O) (- R) (- O -R), -P (= O) (-O-R) ₂ , -O-PH (= O) -R, -O-P (= O) (-R) _2- O-PH (= O) —O—R, —O—P (═O) (— R) (— O—R), —O—P (═O) (— O—R) ₂ , —NH—PH (═O) —R , —NH—P (═O) (— R) (— O—R), —NH—P (═O) (— O—R) ₂ , —SiH ₂ —R, —SiH (—R) ₂ , _{-Si (-R) 3, -O-} SiH 2 -R, include -O-SiH (-R) ₂ and -O-Si (-R) _3. R is an aliphatic group, an aromatic group or a heterocyclic group. The number of substituents is preferably from 1 to 5, more preferably from 1 to 4, further preferably from 1 to 3, and preferably 1 or 2. Most preferred. As the substituent, a halogen atom, cyano, alkyl group, alkoxy group, aryl group, aryloxy group, acyl group, carbonamido group, sulfonamido group and ureido group are preferable, halogen atom, cyano, alkyl group, alkoxy group, An aryloxy group, an acyl group and a carbonamido group are more preferred, a halogen atom, cyano, an alkyl group, an alkoxy group and an aryloxy group are still more preferred, and a halogen atom, an alkyl group and an alkoxy group are most preferred.

  The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. The alkyl group may have a cyclic structure or a branch. The number of carbon atoms in the alkyl group is preferably 1-20, more preferably 1-12, still more preferably 1-6, and most preferably 1-4. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, t-butyl, hexyl, cyclohexyl, octyl and 2-ethylhexyl. The alkoxy group may have a cyclic structure or a branch. The number of carbon atoms in the alkoxy group is preferably 1-20, more preferably 1-12, still more preferably 1-6, and most preferably 1-4. The alkoxy group may be further substituted with another alkoxy group. Examples of the alkoxy group include methoxy, ethoxy, 2-methoxyethoxy, 2-methoxy-2-ethoxyethoxy, butyloxy, hexyloxy and octyloxy.

  The number of carbon atoms in the aryl group is preferably 6-20, and more preferably 6-12. Examples of the aryl group include phenyl and naphthyl. The aryloxy group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. Examples of the aryloxy group include phenoxy and naphthoxy. The number of carbon atoms in the acyl group is preferably 1-20, and more preferably 1-12. Examples of the acyl group include formyl, acetyl and benzoyl. The carbonamide group has preferably 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of the carbonamido group include acetamide and benzamide. The number of carbon atoms in the sulfonamide group is preferably 1-20, and more preferably 1-12. Examples of the sulfonamide group include methanesulfonamide, benzenesulfonamide, and p-toluenesulfonamide. The ureido group has preferably 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of ureido groups include (unsubstituted) ureido.

  The number of carbon atoms in the aralkyl group is preferably 7-20, and more preferably 7-12. Examples of the aralkyl group include benzyl, phenethyl and naphthylmethyl. The number of carbon atoms of the alkoxycarbonyl group is preferably 1-20, and more preferably 2-12. Examples of the alkoxycarbonyl group include methoxycarbonyl. The aryloxycarbonyl group preferably has 7 to 20 carbon atoms, and more preferably 7 to 12 carbon atoms. Examples of the aryloxycarbonyl group include phenoxycarbonyl. The number of carbon atoms in the aralkyloxycarbonyl group is preferably 8-20, and more preferably 8-12. Examples of the aralkyloxycarbonyl group include benzyloxycarbonyl. The number of carbon atoms in the carbamoyl group is preferably 1-20, and more preferably 1-12. Examples of the carbamoyl group include (unsubstituted) carbamoyl and N-methylcarbamoyl. The number of carbon atoms in the sulfamoyl group is preferably 20 or less, and more preferably 12 or less. Examples of the sulfamoyl group include (unsubstituted) sulfamoyl and N-methylsulfamoyl. The number of carbon atoms of the acyloxy group is preferably 1-20, and more preferably 2-12. Examples of the acyloxy group include acetoxy and benzoyloxy.

  The number of carbon atoms of the alkenyl group is preferably 2-20, and more preferably 2-12. Examples of alkenyl groups include vinyl, allyl and isopropenyl. The alkynyl group preferably has 2 to 20 carbon atoms, and more preferably 2 to 12 carbon atoms. Examples of alkynyl groups include thienyl. The number of carbon atoms in the alkylsulfonyl group is preferably 1-20, and more preferably 1-12. The arylsulfonyl group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. The alkyloxysulfonyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. The number of carbon atoms of the aryloxysulfonyl group is preferably 6-20, and more preferably 6-12. The number of carbon atoms of the alkylsulfonyloxy group is preferably 1-20, and more preferably 1-12. The number of carbon atoms of the aryloxysulfonyl group is preferably 6-20, and more preferably 6-12.

  In the cellulose ester according to 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, Examples include butyryl, isobutyryl, valeryl, pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl and the like.

  In the present invention, the aliphatic acyl group is meant to include those further having a substituent, and the substituent is a substitution of a benzene ring when the aromatic ring is a benzene ring in the above-described aromatic acyl group. What was illustrated as a group is mentioned.

  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.).

  As the structure used in the cellulose ester according to the present invention, 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. These may be used alone or as a mixed acid ester of cellulose, or a mixture of two or more cellulose esters.

  The cellulose ester according to the present invention is preferably at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate.

  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, 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 are preferable. The portion 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.

  In addition, the cellulose ester used in the present invention preferably has a water content of 3% by mass or less.

  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.

(Additive inclusion)
The cellulose ester according to the present invention preferably contains one or more additives before being heated and melted.

  In the present invention, the inclusion of the additive includes not only the state in which the additive is encapsulated in the cellulose ester but also the presence in the interior and the surface.

  Examples of the method for encapsulating the additive include a method in which the cellulose ester is dissolved in a solvent, and then the additive is dissolved or finely dispersed therein to remove the solvent. As a method for removing the solvent, a known method can be applied, and examples thereof include a submerged drying method, an air drying method, a solvent coprecipitation method, a freeze drying method, a solution casting method, and the like. The mixture of additives can be prepared in the form of powder, granules, pellets, films and the like. The inclusion of the additive is performed by dissolving the cellulose ester solid as described above, but it may be performed simultaneously with precipitation solidification in the cellulose ester synthesis step.

  In the in-liquid drying method, for example, an aqueous solution of an activator such as sodium lauryl sulfate is added to a solution in which cellulose ester and additives are dissolved, and the mixture is emulsified and dispersed. Next, the solvent is removed by distillation under normal pressure or reduced pressure, and a dispersion of cellulose ester containing the additive can be obtained. Furthermore, it is preferable to perform centrifugation or decantation to remove the active agent. As an emulsification method, various methods can be used, and it is preferable to use an emulsification dispersion apparatus using ultrasonic waves, high-speed rotational shearing, and high pressure.

  In the emulsification dispersion using ultrasonic waves, so-called batch type and continuous type can be used. The batch method is suitable for producing a relatively small amount of sample, and the continuous method is suitable for producing a large amount of sample. In the continuous type, for example, an apparatus such as UH-600SR (manufactured by SMT Co., Ltd.) can be used. In the case of such a continuous system, the irradiation time of ultrasonic waves can be obtained by the dispersion chamber volume / flow velocity × circulation number. When there are a plurality of ultrasonic irradiation apparatuses, it is obtained as the total of the respective irradiation times. The irradiation time of ultrasonic waves is practically 10000 seconds or less. Further, if it is necessary for 10000 seconds or more, the load on the process is large, and in practice, it is necessary to shorten the emulsification dispersion time by reselecting the emulsifier. Therefore, more than 10,000 seconds are not necessary. More preferably, it is 10 seconds or more and 2000 seconds or less.

  Disperser mixers, homomixers, ultramixers, and the like can be used as the emulsifying and dispersing apparatus by high-speed rotational shearing, and these types can be selectively used depending on the liquid viscosity at the time of emulsifying dispersion.

LAB2000 (manufactured by SMT) can be used for emulsification and dispersion at high pressure, but the emulsification / dispersion ability depends on the pressure applied to the sample. The pressure is preferably in the range of 10 ^{4 to} 5 × 10 ⁵ kPa.

  As the activator, a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a polymer dispersant and the like can be used, and can be determined according to the particle size of the solvent or the target emulsion. .

  In the air drying method, for example, a solution in which a cellulose ester and an additive are dissolved is sprayed and dried using a spray dryer such as GS310 (manufactured by Yamato Kagaku Co., Ltd.).

  In the solvent coprecipitation method, a solution in which a cellulose ester and an additive are dissolved is added to a solution that is a poor solvent for the cellulose ester and the additive and is precipitated. The poor solvent can be arbitrarily mixed with the solvent for dissolving the cellulose ester. The poor solvent may be a mixed solvent. Moreover, you may add a poor solvent in the solution of a cellulose ester and an additive.

  The mixture of the precipitated cellulose ester and additive can be separated by filtration, drying and separation.

  In the mixture of cellulose ester and additive, the particle size of the additive in the mixture is 1 μm or less, preferably 500 nm or less, and more preferably 200 nm or less. The smaller the particle size of the additive, the more preferable is the uniform distribution of mechanical and optical properties of the melt-formed product.

  The mixture of the cellulose ester and the additive and the additive added at the time of heat melting are preferably dried before heat melting or at the time of heat melting. The term “drying” as used herein refers to the removal of either the water or solvent used in preparing the mixture of cellulose ester and additive, or the solvent mixed during synthesis of the additive in addition to the moisture absorbed by any of the molten materials. Sure.

  As this removal method, a known drying method can be applied, and it can be performed by a method such as a heating method, a reduced pressure method, a heated reduced pressure method, etc. When performing these known drying methods, it is preferable in terms of film quality to be performed in a temperature range where the material does not decompose.

  For example, the moisture or solvent remaining after removal in the drying step is 10% by mass or less, preferably 5% by mass or less, more preferably 1% by mass or less, and still more preferably, with respect to the total mass of the film constituting material. Is 0.1% by mass or less. The drying temperature at this time is preferably 100 ° C. or higher and Tg or lower of the material to be dried. Including the viewpoint of avoiding fusion between materials, the drying temperature is more preferably 100 ° C. or more (Tg-5) ° C. or less, and still more preferably 110 ° C. or more (Tg-20) ° C. or less. A preferable drying time is 0.5 to 24 hours, more preferably 1 to 18 hours, and still more preferably 1.5 to 12 hours. Below these ranges, the degree of drying may be low, or the drying time may be too long. When Tg is present in the material to be dried, heating to a drying temperature higher than Tg may cause the material to fuse and make handling difficult.

  The drying process may be separated into two or more stages. For example, the material may be melted and filmed through storage of the material by the preliminary drying process and immediately before the melt filming and immediately before drying for 1 week. .

(Additive)
The cellulose ester film of the present invention has at least one plasticizer as an additive, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monovalent alcohol. In addition to this, a peroxide decomposing agent, a radical scavenger, a metal deactivator, an ultraviolet absorber, a matting agent, a dye, a pigment, and a plasticizer other than the above may also be included. .

  It is represented by coloring and molecular weight reduction, including decomposition reactions that have not been elucidated, such as oxidation prevention of film constituent materials, capture of acid generated by decomposition, suppression or prohibition of decomposition reaction due to radical species due to light or heat, etc. Additives are used in order to suppress the generation of volatile components due to deterioration or material decomposition, and to impart functions such as moisture permeability and slipperiness.

  On the other hand, when the film constituent material is heated and melted, the decomposition reaction becomes remarkable, and this decomposition reaction may be accompanied by strength deterioration of the constituent material due to coloring or molecular weight reduction. Moreover, generation | occurrence | production of an unfavorable volatile component may occur by the decomposition reaction of a film constituent material.

  When the film constituent material is heated and melted, the presence of the above-mentioned additive is excellent in terms of suppressing the deterioration of the strength based on the deterioration and decomposition of the material, or maintaining the strength inherent to the material. It is preferable that the above-mentioned additives are present from the viewpoint that the optical film can be produced.

  In addition, the presence of the above-described additives suppresses the formation of colored substances in the visible light region at the time of heating and melting, or unfavorable performance as an optical film such as transmittance and haze value generated by mixing volatile components in the film. It is excellent in that it can suppress or eliminate.

  In the present invention, the display image of the liquid crystal display image is affected when the optical film is used in the configuration of the present invention exceeding 1%, and therefore the haze value is preferably less than 1%, more preferably less than 0.5%. .

  Due to the presence of the above-mentioned additives, it is possible to suppress deterioration of the strength of the film constituting material or to maintain the strength inherent to the material in the step of imparting retardation during film production. This is because if the film constituting material becomes brittle due to remarkable deterioration, breakage is likely to occur in the stretching step, and the retardation value may not be controlled.

  In the above-described film constituent material storage or film forming process, deterioration reactions due to oxygen in the air may occur simultaneously. In this case, the effect of reducing the oxygen concentration in the air can be used together with the stabilizing action of the additive in realizing the present invention. This includes the use of nitrogen or argon as an inert gas as a known technique, degassing operation under reduced pressure to vacuum, and operation under a sealed environment, and at least one of these three methods includes the above additives. Can be used in combination with the method of By reducing the probability that the film constituent material comes into contact with oxygen in the air, deterioration of the material can be suppressed, which is preferable for the purpose of the present invention.

  Since the optical film of the present invention is used as a polarizing plate protective film, the above-mentioned additives are added to the film constituting material from the viewpoint of improving the storage stability over time with respect to the polarizing plate of the present invention and the polarizer constituting the polarizing plate. Is preferably present.

  In the liquid crystal display device using the polarizing plate of the present invention, since the above-mentioned additives are present in the optical film of the present invention, the storage stability of the optical film over time can be improved from the viewpoint of suppressing the above-mentioned deterioration and deterioration, and the liquid crystal Also in improving the display quality of the display device, the optical compensation design provided with the optical film is excellent in that the function can be expressed over a long period of time.

(Ester plasticizer consisting of polyhydric alcohol and monovalent carboxylic acid, ester plasticizer consisting of polyvalent carboxylic acid and monovalent alcohol)
In general, it is preferable to add a compound known as a plasticizer from the viewpoint of film modification such as improvement of 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. This includes the purpose of reducing the viscosity of the film constituting material. 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 exhibits a fluidity due to a decrease in elastic modulus or viscosity due to heat absorption above the glass transition temperature. 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. Furthermore, an ester plasticizer composed of a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer composed of a polyvalent carboxylic acid and a monovalent alcohol have a high affinity with the cellulose ester and are more preferred.

  In the present invention, an ester plasticizer composed of a polyhydric alcohol and a monovalent carboxylic acid and / or an ester plasticizer composed of a polyvalent carboxylic acid and a monovalent alcohol are used.

  An ethylene glycol ester plasticizer that is one of polyhydric alcohol esters: specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropylcarboxylate And ethylene glycol cycloalkyl ester plasticizers such as ethylene glycol dicyclohexylcarboxylate, 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, it may be a mix of alkylate group, cycloalkylate group and arylate group, and these substituents may be covalently bonded. Further, the ethylene glycol part may be substituted, and 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. It may be introduced into a part of the molecular structure of the additive.

  Glycerin ester plasticizer that is one of polyhydric alcohol esters: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, glycerol tricyclopropylcarboxylate, glycerol Glycerin cycloalkyl esters such as tricyclohexylcarboxylate, glycerol aryl esters such as glycerol tribenzoate and glycerol 4-methylbenzoate, diglycerol tetraacetylate, diglycerol tetrapropionate, diglycerol acetate tricaprylate, diglycerol tetralaur Diglycerin alkyl ester such as rate, diglycerin tetracyclobutylcarboxylate, diglycerin tetracyclo Diglycerol cycloalkyl esters such as emissions chill carboxylate, 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 mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and the antioxidant, acid scavenger, You may introduce | transduce into a part of molecular structure of additives, such as a ultraviolet absorber.

  Specific examples of other polyhydric alcohol ester plasticizers 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 mixture 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.

  Among the ester plasticizers composed of the polyhydric alcohol and the monovalent carboxylic acid, alkyl polyhydric alcohol aryl esters are preferable. Specifically, the above-mentioned ethylene glycol dibenzoate, glycerin tribenzoate, diglycerin tetrabenzoate, Exemplified compound 16 described in paragraph 32 of Kokai 2003-12823 can be mentioned.

  Dicarboxylic acid ester plasticizer that is one of polyvalent carboxylic acid esters: Specifically, alkyl dicarboxylic acid alkyl such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), etc. Ester plasticizers, alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclopentyl succinate and dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, Cycloalkyl dicarboxylic acid alkyl ester plasticizers such as dihexyl-1,4-cyclohexanedicarboxylate and didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutane Dicarbo Cycloalkyl dicarboxylic acid cycloalkyl ester plasticizers such as sylate and dicyclopropyl-1,2-cyclohexyl dicarboxylate, diphenyl-1,1-cyclopropyl dicarboxylate, di2-naphthyl-1,4-cyclohexane Cycloalkyldicarboxylic acid aryl ester plasticizers such as dicarboxylate, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclopropyl phthalate Aryl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclohexyl phthalate, and aryl dicarboxylic acid aryl esters such as diphenyl phthalate and di 4-methylphenyl phthalate. Ether-based plasticizers. 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. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and it may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

  The addition amount of the ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and the ester plasticizer comprising a polyhydric carboxylic acid and a monohydric alcohol is usually 0.1 to 100 parts by mass of the cellulose ester. 50 parts by mass, preferably 1-30 parts by mass, more preferably 3-15 parts by mass.

  Examples of other polycarboxylic acid ester plasticizers include alkyl polycarboxylic acid alkyl esters such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate. Plasticizers, alkylpolycarboxylic acid cycloalkyl ester plasticizers such as tricyclohexyltricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy- Alkyl polyvalent carboxylic acid aryl ester plasticizers such as 1,2,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2, 3,4-cyclobutanetetracarboxylate, tetrabu Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as ru-1,2,3,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl- Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as 1,3,5-cyclohexyl tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2, Cycloalkyl polycarboxylic acid aryl ester plasticizers such as 3,4,5,6-cyclohexylhexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4 , 5-tetracarboxylate and other aryl polyvalent Rubinoic acid alkyl ester plasticizers, tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate and other aryl polyvalent carboxylic acid cycloalkyl esters Plasticizers of aryl polyvalent carboxylic acid aryl esters such as plasticizers triphenylbenzene-1,3,5-tetracarboxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Agents. These alkoxy groups and cycloalkoxy groups may be the same or different, and 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. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant into the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  Among the ester plasticizers composed of the polyvalent carboxylic acid and the monohydric alcohol, alkyl dicarboxylic acid alkyl esters are preferable, and specific examples include the dioctyl adipate.

(Other plasticizers)
Examples of other plasticizers used in the present invention include phosphate ester plasticizers and polymer plasticizers.

  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, cresyl Examples thereof include phosphoric acid aryl esters such as 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. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  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. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Furthermore, the partial structure of the phosphate ester may be part of the polymer or may be regularly pendant, and may be introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It 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.

  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 occurs in volatility, and if it exceeds 500,000, the plasticizing ability is lowered, and the mechanical properties of the cellulose ester film are adversely affected. 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.

  Other plasticizer addition amount is 0.1-50 mass parts normally with respect to 100 mass parts of cellulose esters, Preferably it is 1-30 mass parts, More preferably, it is 3-15 mass parts.

(Acid scavenger)
The acid scavenger is an agent that plays a role of trapping an acid (protonic acid) remaining in the cellulose ester brought in from the production. Further, when the cellulose ester is melted, the hydrolysis of the side chain is accelerated by moisture and heat in the polymer, and acetic acid and propionic acid are generated in the case of CAP. A compound having an epoxy structure, a tertiary amine, an ether structure, or the like may be used as long as it can be chemically bonded to an acid, but is not limited thereto.

  Specifically, it is preferable to comprise 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 diglycidyl ethers of various polyglycols, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Metal glycol compounds such as polyglycols, diglycidyl ethers of glycerol (eg, those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, bisphenol A Diglycidyl ether (ie, 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of alkyl of about 2 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms such as butyl Epoxy stearate) ), And various epoxidized long chain fatty acid triglycerides, etc. (eg, epoxidized vegetable oils and other unsaturated natural oils, which are sometimes represented and exemplified by compositions such as epoxidized soybean oil) These are referred to as glycerides or unsaturated fatty acids, which generally contain 12 to 22 carbon atoms)). Particularly preferred are commercially available epoxy group-containing epoxide resin compounds EPON 815c and other epoxidized ether oligomer condensation products of general formula (1).

  In the above formula, n is equal to 0-12. Further, acid scavengers that can be used include those described in paragraphs 87 to 105 of JP-A No. 5-194788.

(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, absorption of visible light having a wavelength of 400 nm or more is absorbed. 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, 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.

(Matting agent)
Fine particles such as a matting agent can be added to the cellulose ester film of the present invention in order to impart slipperiness, and examples of the fine particles include inorganic compound fine particles and organic compound fine particles. 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 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, 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 0.05 to 1.0 μm. The average particle size of secondary particles of the 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 generate irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film. The content of the fine particles in the cellulose ester is preferably 0.005 to 0.3% 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. The presence of the fine particles in the film can also improve the orientation of the cellulose ester itself constituting the optical film of the present invention.

(Retardation control agent)
In the optical film of the present invention, an alignment film is formed to provide a liquid crystal layer, and the optical film and the retardation derived from the liquid crystal layer are combined to provide an optical compensation capability, so that such polarization is improved for improving the liquid crystal display quality. Plate processing may be performed. The compound added to adjust the retardation is an aromatic compound having two or more aromatic rings as described in EP 911,656A2, and used as a retardation control agent. You can also. 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. An aromatic heterocyclic ring is particularly preferred, and the aromatic heterocyclic ring is generally an unsaturated heterocyclic ring. Of these, a 1,3,5-triazine ring is particularly preferred.

(Dimensional stability)
The optical film of the present invention has a dimensional stability at 80 ° C. and 90% RH of less than ± 1.0% when the dimensional stability is based on the dimensions of the film left at 23 ° C. and 55% RH for 24 hours. More preferably, it is less than 0.5%, and particularly preferably less than 0.1%.

  Since the optical film of the present invention is used as a protective film for a polarizing plate, if the optical film itself has a fluctuation beyond the above range, the absolute value of the retardation as a polarizing plate and the orientation angle are shifted from the initial setting. In some cases, the display quality may be reduced or the display quality may be deteriorated. The orientation angle refers to the smaller one of the angles formed by the direction having the maximum in-plane refractive index and the film transport direction or the direction perpendicular to the film transport direction.

(Film constituent materials)
The presence of the additive in the film constituting material is at least one of the materials constituting the film, such as the cellulose ester, plasticizer, antioxidant, and other ultraviolet absorbers, matting agents, retardation control agents, and the like that are added as necessary. It is excellent in terms of suppressing or preventing the generation of volatile components due to alteration or decomposition over the seeds. Further, the additive itself is required not to generate a volatile component in the melting temperature region of the film constituting material.

  The content of the volatile component when the film constituent material is melted is 1% by mass or less, preferably 0.5% by mass or less, preferably 0.2% by mass or less, more preferably 0.1% by mass or less. It is desirable to be. In the present invention, using a differential thermal mass measuring apparatus (TG / DTA200 manufactured by Seiko Denshi Kogyo Co., Ltd.), the heating loss from 30 ° C. to 350 ° C. is determined, and the amount is defined as the content of volatile components.

(Stretching operation, refractive index control)
The optical film of the present invention can be controlled in refractive index 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. Can do.

  For example, the film can be stretched sequentially or simultaneously in the longitudinal direction of the film and the direction orthogonal 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 stretching in the direction of melting and casting, if the shrinkage 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 using the tenter method, but it is a phenomenon that occurs when the film is stretched in the width direction and contraction force is generated at the center of the film and the end is fixed. It is thought to be called. 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 improved.

  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 variation in the film thickness of the optical film is too large, the retardation will be 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 optical 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 optical film is preferably in the width direction, and satisfies (stretch ratio in the width direction)> (stretch ratio in the casting direction). is required.

  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.

  When the optical film of the present invention is a polarizing plate protective film, the thickness of the protective film is preferably 10 to 500 μm. In particular, it is preferably 20 μm or more, and more preferably 35 μm or more. Moreover, 150 micrometers or less, Furthermore 120 micrometers or less are preferable. Most preferably, it is 25 or more and 90 micrometers. If the optical film is thicker than the above region, the polarizing plate after polarizing plate processing becomes too thick, so that it is not suitable for the purpose of thin and light in liquid crystal displays used for notebook personal computers and mobile electronic devices. On the other hand, if it is thinner than the above region, it is not preferable because retardation is difficult to develop, and the film has high moisture permeability and the ability to protect the polarizer from humidity is reduced.

  The slow axis or the fast axis of the optical film of the present invention is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less, assuming that the angle formed with the film forming direction is θ1. More preferably, it is 5 ° or more and + 0.5 ° or less. This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments).

  Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

(Polymer material)
In the optical film of the present invention, polymer materials and oligomers other than cellulose ester 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 contain as an above-mentioned other additive.

(Film formation)
The mixture of cellulose ester and additive according to the present invention is dried with hot air or vacuum, then melt extruded, extruded into a film form from a T-die, brought into close contact with a cooling drum by an electrostatic application method, etc., cooled and solidified. A stretched film is obtained. The temperature of the cooling drum is preferably maintained at 90 to 150 ° C.

  Melt extrusion may be used by connecting a single screw extruder, a twin screw extruder, and a single screw extruder downstream of the twin screw extruder, but from the viewpoint of the mechanical properties and optical properties of the obtained film, a single screw extruder is used. It is preferable to use it. 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.

  The temperature at the time of melt extrusion according to the present invention is usually in the range of 150 to 300 ° C, preferably in the range of 180 to 270 ° C, more preferably in the range of 200 to 250 ° C.

  When a polarizing plate is produced using the optical film of the present invention as a polarizing plate protective film, the cellulose ester film 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 in 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. Next, the cellulose ester film stretched in the longitudinal direction obtained as described above is preferably stretched transversely within a temperature range of Tg to Tg-20 ° C. and then heat-set.

  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.

  In the heat setting, heat setting is usually performed for 0.5 to 300 seconds at a temperature higher than the final transverse stretching temperature and within a temperature range of Tg-20 ° C or lower. 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. At this time, it is preferable to perform a relaxation treatment of 0.1 to 10% in the lateral direction and / or the longitudinal direction within a temperature range of not more than the final heat setting temperature and not less than Tg. In addition, it is preferable that the cooling is gradually performed 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.

(Functional layer)
In the production of the optical film of the present invention, functions such as an antistatic layer, a hard coat layer, an antireflection layer, a slippery layer, an easy adhesion layer, an antiglare layer, a barrier layer, and an optical compensation layer before and / or after stretching. A sex layer may be applied. In particular, it is also 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.

  In the cellulose ester film of the present invention, the cellulose ester film or the additive may be co-extruded with different content layers to form a cellulose ester film having a laminated structure.

  For example, a cellulose ester film having a structure of skin layer / core layer / skin layer can be produced. For example, fine particles such as a matting agent can be contained in the skin layer in a large amount or only in the skin layer. In addition, a melt-extruded layer of diacetyl cellulose that can be easily saponified may be formed on the skin layer. Melt extrusion of diacetylcellulose can be achieved according to known methods. Further, a low-volatile plasticizer and / or an ultraviolet absorber can be contained in the skin layer, and a plasticizer having excellent plasticity or an ultraviolet absorber having excellent ultraviolet absorption can be added to the core layer. The glass transition temperature of the skin layer and the core layer may be different, and the glass transition temperature of the core layer may be lower than the glass transition temperature of the skin layer. Also, the viscosity of the melt containing the cellulose ester at the time of melt casting may be different between the skin layer and the core layer, and the viscosity of the skin layer> the viscosity of the core layer or the viscosity of the core layer ≧ the viscosity of the skin layer may be When the viscosity of the thinner layer (usually skin layer) is higher, a laminate having a uniform film thickness can be obtained.

(Polarizer)
When a polarizing plate is formed and used as a polarizing plate protective film for the liquid crystal display device, the polarizing plate of at least one surface is preferably the polarizing plate of the present invention, and both surfaces are polarizing plates of the present invention. It is more preferable that

  In addition, as a conventional polarizing plate protective film, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC8UCR-3, KC8UCR-4, KC12UR, KC8UXW-H, KC8UYW-HA, KC8UX-RHA Cellulose ester films such as those manufactured by KK) are used.

  The production method of the polarizing plate of the present invention is not particularly limited, and can be produced 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. Can be pasted together. This method is preferable in that the polarizing plate protective film of the present invention can be directly bonded to a polarizer on at least one side.

  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 when the polarizing plate is shipped or transported. 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 cell. The separate film is used for the purpose of covering the adhesive layer.

(Liquid crystal display device)
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the cellulose ester film of the present invention is applied has high dimensional stability, so it can be placed at any position. In addition, excellent display properties can be obtained. A polarizing plate protective film provided with a clear hard coat layer, an antiglare layer, an antireflection layer, or the like is preferably used for this portion of the polarizing plate protective film on the outermost display side of the liquid crystal display device. In the case of a polarizing plate protective film provided with an optical compensation layer, or a polarizing plate protective film provided with an appropriate optical compensation capability by stretching operation or the like, it is excellent in being disposed at a site in contact with the liquid crystal cell. Displayability is obtained. In particular, the use of the present invention for a multi-domain type liquid crystal display device, more preferably a multi-domain type liquid crystal display device with a birefringence mode, can further exhibit the effects of the present invention.

  Multi-domain is a method of dividing a liquid crystal cell that constitutes one pixel into a plurality of parts, and is suitable for improving the viewing angle dependency and the symmetry of image display. Various methods have been reported. “Okita, Yamauchi: Liquid Crystal, 6 (3), 303 (2002)”. The liquid crystal display cell is also shown in “Yamada, Yamabara: Liquid Crystal, 7 (2), 184 (2003)”, but is not limited thereto.

  The display quality of the display cell is preferably symmetrical with respect to human observation. Therefore, when the display cell is a liquid crystal display cell, the domains can be multiplied substantially giving priority to the symmetry on the observation side. A known method can be used to divide the domain, and can be determined by taking into account the properties of the known liquid crystal mode by a two-division method, more preferably a four-division method.

  The polarizing plate of the present invention includes an MVA (Multi-domain Vertical Alignment) mode represented by a vertical alignment mode, in particular, an MVA mode divided into four, a known PVA (Patterned Vertical Alignment) mode and an electrode multi-domained by an electrode arrangement. It can be effectively used in a CPA (Continuous Pinwheel Alignment) mode in which arrangement and chiral ability are fused. In addition, a proposal of an optically biaxial film is also disclosed in conformity to the OCB (Optical Compensated Bend) mode, and “T. Miyashita, T. Uchida: J. SID, 3 (1), 29 ( 1995) ", the polarizing plate of the present invention can also exhibit the effect of the present invention in display quality. If the effect of this invention can be expressed by using the polarizing plate of this invention, arrangement | positioning of a liquid crystal mode and a polarizing plate will not be limited.

  Since the liquid crystal display device has high performance as a device for colorization and moving image display, the display quality of the liquid crystal display device using the optical film of the present invention, particularly a large-sized liquid crystal display device, is faithful with less eye fatigue. A moving image can be displayed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. In addition, the following "part" represents a "mass part".

Example 1
[Production of cellulose ester film]
Cellulose ester C-1 (manufactured by Eastman Chemical Co., CAP-482-20) was dried in air at normal pressure at 130 ° C. for 2 hours and allowed to cool to room temperature. In this cellulose ester, the exemplified compound 8 shown below: Compound 16, an exemplified compound 8 of a compound having an e value of e <−0.8 according to the Qe method of the present invention (hereinafter referred to as the present compound) is compared with the cellulose ester. 1 part by mass was added, and the mixture was heated and melted to a melting temperature of 230 ° C., then melt-extruded from a T-die, and further stretched at 160 ° C. at a stretch ratio of 1.2 × 1.2. As a result, a cellulose ester film sample 1-1 having a film thickness of 80 μm was obtained.

  Moreover, this invention sample 1-2-8 and 1-10-13 are the same method except having changed cellulose ester seed | species, this invention compound seed | species and addition amount, organic base seed | species, and addition amount as shown in Table 1. The cellulose ester films of Comparative Samples 1-9 and 14 (all having a film thickness of 80 μm) were prepared.

C-1: Cellulose acetate propionate CAP482-20 (manufactured by Eastman Chemical Co.)
C-2: Cellulose acetate butyrate CAB171-15 (manufactured by Eastman Chemical Co.)
Comparative compound:

  The present invention samples 1-1 to 8, 1-10 to 13 and comparative samples 1-9 and 14 produced as described above were evaluated as described below. The results are shown in Table 2.

[Evaluation]
(Retardation coefficient of variation (CV))
The surface layer was peeled from the formed film, the retardation was measured at 1 cm intervals in the width direction of the obtained cellulose ester film sample, and expressed by the variation coefficient (CV) of the retardation obtained from the following formula It is. For measurement, an automatic birefringence meter KOBURA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) is used and is three-dimensionally spaced at 1 cm intervals in the width direction of the sample at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. The birefringence was measured and the measured value was substituted into the following equation.

In-plane retardation Ro = (nx−ny) × d
Thickness direction retardation Rt = ((nx + ny) / 2−nz) × d
Here, d is the thickness (nm) of the film, the refractive index nx (also referred to as the maximum refractive index in the plane of the film, the refractive index in the slow axis direction), ny (in the direction perpendicular to the slow axis in the film plane). ) (Refractive index of the film in the thickness direction). The standard deviation by the (n-1) method was calculated | required for the obtained in-plane and thickness direction retardation, respectively. For the retardation distribution, the coefficient of variation (CV) shown below was obtained and used as an index. In actual measurement, n was set to 130 to 140.

Coefficient of variation (CV) = standard deviation / retardation average value ◎: variation (CV) is less than 1.5% ○: variation (CV) is 1.5% or more and less than 5% Δ: variation (CV) is 5% Or more, less than 10% x: variation (CV) is 10% or more (haze)
From the result of measurement using a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.), it was converted into a haze value when the sample thickness was 80 μm and displayed. In the evaluation, a haze of less than 0.5% was evaluated as ◎, 0.5 to less than 1.0% as ◯, 1.0 to less than 1.5% as Δ, and 1.5% or more as x.

(Bright spot foreign matter)
Two polarizing plates are arranged in an orthogonal state (crossed Nicols) to block transmitted light, and each sample is placed between the two polarizing plates. The polarizing plate used was a glass protective plate. Light was irradiated from one side, and the number of bright spots having a diameter of 0.01 mm or more per 1 cm ² was counted with an optical microscope (50 times) from the opposite side. In the evaluation, 0 to 30 volatiles were evaluated as ◎, 31 to 60 as ◯, 61 to 90 as Δ, and 91 or more as ×.

  From the above table, the inventive samples 1-1 to 8 and 1-10 to 13 have better retardation fluctuations, haze, bright spot foreign matter and optically superior than the comparative samples 1-9 and 14. it is obvious.

Example 2
In the same manner as in Example 1, except that the cellulose ester species, the present compound species and addition amount, the antioxidant species (AO agent 1, AO agent 2) and the addition amount were changed as shown in Table 3, Cellulose ester films (both having a film thickness of 80 μm) Inventive samples 2-1 to 2-10, 2-12 to 2-15, and comparative samples 2-11 and 2-16 were prepared.

  Using the produced cellulose ester film sample, the same evaluation as in Example 1 was performed, and the results are shown in Table 4.

  From the above table, Samples 2-1 to 2-10 and 2-12 to 2-15 of the present invention are good in retardation fluctuation, haze, and bright spot foreign matter as compared with Comparative Samples 2-11 and 2-16, and optical. It is clear that this is superior.

Example 3
In the same manner as in Example 1, the cellulose ester species, the present compound species and addition amount, the antioxidant species (AO agent 1, AO agent 2) and addition amount, the plasticizer species (described in Chemical Formula 4) and the addition amount are determined. Cellulose ester films (both having a film thickness of 80 μm) are the same except that they are changed as shown in Table 5. Samples 3-1 to 3-10, 3-12 to 3-15, comparative samples 3-11 and 3- 16 was produced.

  Using the produced cellulose ester film sample, the same evaluation as in Example 1 was performed, and the results are shown in Table 6.

  From the above table, the inventive samples 3-1 to 3-10 and 3-12 to 3-15 have better retardation fluctuations, haze, and bright spot foreign matters than the comparative samples 3-11 and 3-16, and are optical. It is clear that this is superior.

Example 4
In the same manner as in Example 1, cellulose ester species (C-1 to C-4), present compound species and addition amount, antioxidant species (AO agent 1, AO agent 2) and addition amount, plasticizer species ( Samples 4-1 to 4-7 of the present invention were prepared in the same manner except that the addition amount was changed as shown in Table 7 and the cellulose ester film (both had a film thickness of 80 μm).

C-3: Cellulose acetate propionate (acetyl group substitution degree 1.9, propionyl group substitution degree 0.8, molecular weight Mn = 70,000, molecular weight Mw = 220,000, Mw / Mn = 3)
C-4: Cellulose triacetate Using the produced cellulose ester film sample, the same evaluation as in Example 1 was performed and the results are shown in Table 8.

  From the above table, it is clear that Samples 4-1 to 4-7 of the present invention are excellent in retardation fluctuation, haze, and bright spot foreign matter and optically excellent.

Example 5
[Preparation of polarizing plate]
A 120 μm thick polyvinyl alcohol film was immersed in an aqueous solution containing 1 part by mass of iodine, 2 parts by mass of potassium iodide, and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to produce a polarizer.

  The inventive samples 3-1 to 3-10, 3-12 to 3-15 and comparative samples 3-11 and 3-16 prepared in Example 3 were alkalinized with a 2.5 M sodium hydroxide aqueous solution at 40 ° C. for 60 seconds. Then, the surface was further washed with water and dried for alkali treatment.

  The alkali-treated surfaces of Samples 3-1 to 3-10, 3-12 to 3-15, and Comparative Samples 3-11 and 3-16 of the present invention were applied to both surfaces of the polarizer, and a 5% aqueous solution of completely saponified polyvinyl alcohol was added. The polarizing plates 3-1 to 3-10, 3-12 to 3-15, and the polarizing plates 3-11 and 3-16 of the present invention, in which the protective film was formed, were bonded from both sides as an adhesive. .

  The polarizing plates 3-1 to 3-10 and 3-12 to 3-15 of the present invention are optically and physically excellent compared with the comparative polarizing plates 3-11 and 3-16, and have a good degree of polarization. It was a polarizing plate.

[Evaluation as a liquid crystal display]
The polarizing plate of 15-type TFT color liquid crystal display LA-1529HM (manufactured by NEC) was peeled off, and each of the polarizing plates prepared above was cut according to the size of the liquid crystal cell. The two polarizing plates prepared as described above were bonded so as to be orthogonal to each other so that the polarization axis of the polarizing plate was not changed from the original so as to sandwich the liquid crystal cell, and a 15-inch TFT color liquid crystal display was prepared. When the characteristics as a polarizing plate were evaluated, the polarizing plates 3-1 to 3-10 and 3-12 to 3-15 of the present invention had contrast compared to the comparative polarizing plates 3-11 and 3-16. High and excellent display performance. Thereby, it was confirmed that it is excellent as a polarizing plate for an image display device such as a liquid crystal display.

Claims (10)

A cellulose ester film comprising at least one compound having an e value of e <−0.8 according to the Qe method. The cellulose ester film according to claim 1, wherein the compound having an e value of e <−0.8 according to the Qe method has at least one aromatic ring. 0.01-5 parts by mass of at least one selected from the group consisting of a phenolic stabilizer, a hindered amine stabilizer, a phosphorus stabilizer, and a sulfur stabilizer in the cellulose ester film with respect to 100 parts by mass of the cellulose ester. The cellulose ester film according to claim 1, wherein the cellulose ester film is contained. The cellulose ester in the cellulose ester film is at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate and cellulose phthalate. The cellulose ester film according to any one of claims 1 to 3. It contains at least one kind of an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyhydric carboxylic acid and a monohydric alcohol. 2. The cellulose ester film according to claim 1. The ester plasticizer comprising the polyhydric alcohol and the monovalent carboxylic acid, and the ester plasticizer comprising the polyhydric carboxylic acid and the monovalent alcohol are an alkyl polyhydric alcohol aryl ester and a dialkylcarboxylic acid alkyl ester, respectively. The cellulose ester film according to claim 5, wherein An optical film using the cellulose ester film according to claim 1. A polarizing plate using the optical film according to claim 7 on at least one surface. A liquid crystal display device using at least one of the optical film according to claim 7 and the polarizing plate according to claim 8. At least one of a cellulose ester, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid or an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol, and the e value by the Qe method is e < Cellulose obtained by melt-melting a mixture comprising at least one compound containing at least one compound of −0.8 at a melting temperature (Tm) of 150 ° C. or more and 300 ° C. or less, and obtained by a melt casting method It is a manufacturing method of an ester film, Comprising: The addition amount of the compound containing at least 1 sort (s) of this plasticizer and the e value by Qe method is e <-0.8 is 1-30 with respect to a cellulose ester, respectively. The manufacturing method of the cellulose-ester film characterized by being the mass% and 0.01-10 mass%.