JP2007298648A - Cellulose ester optical film, method for producing the same, and polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester optical film excellent in spectral absorption performance as an optical film, free of coloring, excellent in transparency, having satisfactory ultraviolet absorption capacity, capable of suppressing attachment of a foreign matter to a surface of a conveyance roll, faulty transfer to the film due to the attachment and depression by the foreign matter on the conveyance roll, and containing an ultraviolet absorber excellent in long-term weather resistance, and to provide a polarizing plate and a liquid crystal display device using the same and an ultraviolet absorbent for use in the same. <P>SOLUTION: The cellulose ester optical film consists primarily of cellulose acylate containing at least one selected from triazine derivatives or benzotriazole derivatives. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cellulose ester optical film used for optical applications, in particular, a protective film for a polarizing plate used for a liquid crystal display device, a retardation film, a viewing angle widening film, an antireflection film used for a plasma display, and the like. The present invention relates to an optical film that can be used for various functional films and various functional films used in organic EL displays and the like, and an ultraviolet absorber used therefor. More specifically, a cellulose ester optical film containing an ultraviolet absorber having a specific structure, having no unnecessary coloration, excellent in color reproducibility, causing no pressing failure, and excellent in durability and light resistance, and The present invention relates to the polarizing plate, the liquid crystal display device and the ultraviolet absorber used.

  An optical film used for optical applications has a problem that when it is exposed to light containing ultraviolet rays, the decomposition is accelerated and the strength is lowered, and at the same time, the transparency is lowered due to the color change. For this reason, in optical films that require high transparency, deterioration due to ultraviolet rays has been prevented by mixing in advance ultraviolet absorbers of benzotriazole compounds, benzophenone compounds, cyanoacrylate compounds, and salicylic acid compounds. However, since many of these conventional ultraviolet absorbers have low solubility, bleed-out is likely to occur, they are likely to be deposited on the film, haze is increased and transparency is lowered, and further, due to transpiration during heat processing. There were various problems such as a decrease in the amount of addition and a decrease in ultraviolet absorption ability and contamination of the production process.

  The introduction of a polymerizable group into an ultraviolet absorber, homopolymerization or copolymerization to obtain an ultraviolet absorbing polymer, and attempts to eliminate these disadvantages are described (for example, Patent Documents 1 to 4). See.) Moreover, the example which made the protective film for polarizing plates contain an ultraviolet absorptive polymer as an optical film is described (for example, refer patent document 5).

  The UV-absorbing polymers described in them were effective to some extent in bleeding out, precipitation prevention, transpiration prevention, etc., but the UV-absorbing ability is not sufficient, and a large amount is required to obtain the desired UV-absorbing performance. The amount of addition is necessary, and when these UV-absorbing polymers are added in a large amount, the compatibility with the resin is not sufficient and sufficient transparency cannot be obtained, or the film itself is colored yellow, or for a long time. When stored, it has problems such as a decrease in the ability to absorb ultraviolet rays, and it has been difficult to put it into practical use as an optical film.

  In addition, there is a description of a water-soluble ultraviolet absorber by introducing a water-soluble group into the benzophenone skeleton (see, for example, Patent Document 6). It is insufficient and the compatibility with the cellulose ester is not good.

On the other hand, in the production of a cellulose ester film as an optical film, the cellulose ester film is transported by a transport roll and dried through a drying device or a tenter to obtain a cellulose ester film. A solid / liquid substance consisting of a plasticizer or UV absorber bleed out on the surface of the film during conveyance by this conveyance roll is transferred to the surface of the conveyance roll, contaminating the film surface, or convex portions due to foreign matter There has been a problem that a pressing failure occurs in which the film is partially deformed by pressing.
JP 60-38411 A JP-A-62-181360 Japanese Patent Application Laid-Open No. 3-28185 JP-A-7-90184 JP-A-6-148430 JP-A-6-87879

  The present invention has been made in view of the above-mentioned problems, and its purpose is excellent in spectral absorption performance as an optical film application, excellent in transparency without coloration, having sufficient ultraviolet absorbing ability, and a transport roll surface. Cellulose ester optics containing UV absorbers with excellent long-term weather resistance, which can greatly reduce the occurrence of film transfer failure caused by this, film transfer failure due to this, and occurrence of pressing failure due to foreign matter on the transport roll The object is to provide a film, a polarizing plate using the film, a liquid crystal display device, and an ultraviolet absorber used therefor.

  As a result of intensive studies on a cellulose ester optical film containing an ultraviolet absorber capable of solving the above-mentioned problems, the present inventor has excellent spectral absorption performance and coloration by using an ultraviolet absorber having a specific structure and physical properties. It has been found that it has sufficient ultraviolet absorption ability, such as no transparency and excellent transparency, and does not cause a failure due to being pressed, and has excellent long-term weather resistance.

  The above object of the present invention can be achieved by the following configuration.

  1. A cellulose ester optical film comprising, as a main component, cellulose acylate containing at least one selected from compounds represented by the following general formulas (1) to (3).

[Wherein, R ₁₁ and R ₁₂ each independently represent a hydrogen atom, a hydroxyl group or an alkoxy group, R ₁₃ , R ₁₄ and R ₁₅ each independently represent a substituent, and R ₁₆ , R ₁₇ and R ₁₈ each represent Independently represents a group having a hydrogen atom or a sugar residue, and at least one of R ₁₆ , R ₁₇ and R ₁₈ represents a group having a sugar residue. l1, m1, and n1 each represents an integer of 0 to 3. ]

[Wherein, R ₂₁ and R ₂₂ each independently represents a hydrogen atom or a substituent, and at least one of R ₂₁ and R ₂₂ represents a group having a sugar residue. p2 represents an integer of 0 to 3, and q2 represents an integer of O to 4. ]

[Wherein, X represents a sugar residue or a divalent linking group containing at least one sugar residue, and A and B represent groups represented by the general formula (4) or (5). May be different. * Is a connection point with X. R ₃₁ and R ₃₂ represent a hydrogen atom or a substituent, and p3 and q3 each represents an integer of 0 to 4. ]
2. 2. The cellulose ester optical film as described in 1 above, wherein the total number of acyl groups in the cellulose acylate is 6.2 or more and 7.5 or less.
However, the acyl group total carbon number is the sum of products of the substitution degree of each acyl group in the cellulose acylate and the carbon number of the acyl group.

  3. 3. A method for producing a cellulose ester optical film, comprising producing the cellulose ester optical film according to 1 or 2 by melt casting.

  4). A polarizing plate using the cellulose ester optical film described in 1 or 2 above.

  5. 3. A liquid crystal display device using the cellulose ester optical film as described in 1 or 2 above.

  With the above-described configuration of the present invention, the ultraviolet absorption property, transparency, durability (bleed out failure), light resistance, and a polarizing plate that maintains high contrast using the cellulose ester optical film that does not cause pressing failure In addition, a liquid crystal display device can be provided.

  The present invention will be described in more detail.

  The cellulose ester optical film of the present invention is a cellulose ester optical film containing as a main component a cellulose acylate containing at least one compound represented by the general formulas (1) to (3), preferably the cellulose acylate. The total acyl group carbon number of the rate is 6.2 or more and 7.5 or less. However, the acyl group total carbon number is the sum of products of the substitution degree of each acyl group in the cellulose acylate and the carbon number of the acyl group.

Cellulose is a natural polymer in which a number of D-glucose molecules are linearized by glycosidic bonds. In D-glucose, hydroxyl groups are bonded to the 1st to 4th and 6th position carbons, respectively. The 6-carbon aldehyde hydroxyl group at the 6 carbons of D-glucose constituting cellulose is condensed with the 4-position alcoholic hydroxyl group to form a cellulose chain by an ether bond. The carbon at the 6th position is a methyl group branched from the carbon at the 5th position, and the hydroxyl group at the 6th position is the hydrogen of this methyl group replaced, and has a structure that protrudes outward from the hexagonal chain of cellulose molecules. . D-glucose cellulose acylate is a polymer obtained by esterifying a part or all of hydroxyl groups bonded to carbons at 2, 3, and 6 positions of glucose units with an acyl group. Here, the “degree of substitution of acyl group” is a scale showing how much acyl group is bonded among 3n hydroxyl groups (with n degree of polymerization), and the degree of substitution is 2 per glucose unit. Of the three hydroxyl groups at the 3rd, 6th and 6th positions, the number of hydroxyl groups is substituted with an acyl group. Therefore, when all the three hydroxyl groups are esterified with an acyl group, the maximum value is 3.0.

  Hereinafter, the present invention and its components will be described in detail.

In the general formula (1), R ₁₁ and R ₁₂ each independently represent a hydrogen atom, a hydroxyl group, or an alkoxy group (for example, a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, etc.), and R ₁₃ , R ₁₄ and R ₁₅ each independently represents a substituent, and examples of the substituent include a halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), alkyl group (for example, methyl group, ethyl group, isopropyl group, Hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl group, etc.), alkenyl group (eg, vinyl group, allyl group, 3-buten-1-yl group, etc.), aryl group (eg, phenyl group, Naphthyl group, p-tolyl group, p-chlorophenyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, isopropoxy group, n-butoxy group) Etc.), aryloxy group (eg phenoxy group etc.), acyloxy group (eg acetoxy group, pivaloyloxy group, benzoyloxy group etc.), acyl group (eg acetyl group, propanoyl group, butyroyl group etc.), alkoxycarbonyl group (Eg, methoxycarbonyl group, ethoxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenoxycarbonyl group, etc.), carbamoyl group (eg, methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group, etc.), alkylthio group (eg, Methylthio group, ethylthio group, n-butylthio group and the like), arylthio group (for example, phenylthio group and the like), and the like.

R ₁₆ , R ₁₇ and R ₁₈ each independently represent a hydrogen atom or a group having a sugar residue, and at least one of R ₁₆ , R ₁₇ and R ₁₈ represents a group having a sugar residue. As the sugar residue, monosaccharides or oligosaccharides having 1 to 10 sugar units, particularly 1 to 5 sugars are preferable. Disaccharides such as carbon sugar, maltose, lactose, trehatose, cellobiose, isomaltose, gentiobiose, melibiose, laminaribiose, chitobiose, xylobiose, mannobiose, sophorose, mantotriose, isomaltotriose, maltotetraose , Mannotriose, manninotriose, etc., and hydrolysates such as starch, cellulose, chitin, chitosan (eg, pharmacopec dextrin, acrodextrin, british gum, cellodextrin) Etc.), and the like.

In the general formula (2), R ₂₁ and R ₂₂ each independently represent a hydrogen atom or a substituent, and the substituent includes a group having a sugar residue, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, Iodine atom, etc.), alkyl group (eg, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl group, etc.), alkenyl group (eg, vinyl group, allyl group, 3-buten-1-yl group), aryl group (for example, phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, isopropoxy group, n -Butoxy group), aryloxy group (for example, phenoxy group), acyloxy group (for example, acetoxy group, pivaloyloxy group, Benzoyloxy group etc.), acyl group (eg acetyl group, propanoyl group, butyroyl group etc.), alkoxycarbonyl group (eg methoxycarbonyl group, ethoxycarbonyl group etc.), aryloxycarbonyl group (eg phenoxycarbonyl group etc.) , Carbamoyl group (for example, methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group, etc.), amino group, alkylamino group (for example, methylamino group, ethylamino group, diethylamino group, etc.), anilino group (for example, anilino group, N-methylanilino group etc.), acylamino group (eg acetylamino group, propionylamino group etc.), hydroxyl group, sulfonamide group (eg methanesulfonamide group, benzenesulfonamide group etc.), sulfa Ylamino group (eg, dimethylsulfamoylamino group), sulfonyl group (eg, methanesulfonyl group, butanesulfonyl group, phenylsulfonyl group), sulfamoyl group (eg, ethylsulfamoyl group, dimethylsulfamoyl group, etc.) ), Sulfonylamino groups (eg, methanesulfonylamino group, benzenesulfonylamino group, etc.), ureido groups (eg, 3-methylureido group, 3,3-dimethylureido group, 1,3-dimethylureido group, etc.), imides Examples thereof include a group (for example, phthalimide group), an alkylthio group (for example, methylthio group, ethylthio group, n-butylthio group, etc.), an arylthio group (for example, phenylthio group, etc.), and the like. When there are a plurality of substituents, they may be the same or different. At least one of R21 and R22 represents a group having a sugar residue, and the sugar residue is preferably a monosaccharide or oligosaccharide having a saccharide unit of 1 to 10, particularly 1 to 5, such as glucose, mannose, galactose, or glucosamine. Hexoses such as mannosamine and galactosamine, pentoses such as arabinose, xylose and ribose, maltose, lactose, trehatose, cellobiose, isomaltose, gentiobiose, melibiose, laminaribiose, chitobiose, xylobiose, mannobiose Sugars, mantotriose, isomaltotriose, maltotetraose, maltopentaose, mannotriose, manninotriose, etc., and hydrolysates such as starch, cellulose, chitin, chitosan Down, Acro dextrin, Buritesshu gum, Cerro dextrin and the like), and the like.

In the general formula (3), A and B represent a group represented by the general formula (4) or (5). In the general formula (4) or (5), R ₃₁ and R ₃₂ are each independently Represents a hydrogen atom or a substituent, and examples of the substituent include a halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom), alkyl group (eg, methyl group, ethyl group, isopropyl group, hydroxyethyl group, Methoxymethyl group, trifluoromethyl group, t-butyl group, etc.), alkenyl group (for example, vinyl group, allyl group, 3-buten-1-yl group, etc.), aryl group (for example, phenyl group, naphthyl group, p -Tolyl group, p-chlorophenyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, isopropoxy group, n-butoxy group, etc.), aryloxy group (eg, phenoxy group) Nonoxy group, etc.), acyloxy group (eg, acetoxy group, pivaloyloxy group, benzoyloxy group, etc.), acyl group (eg, acetyl group, propanoyl group, butyroyl group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, etc.) Group), aryloxycarbonyl group (for example, phenoxycarbonyl group, etc.), carbamoyl group (for example, methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group, etc.), amino group, alkylamino group (for example, methylamino group, ethyl) Amino group, diethylamino group, etc.), anilino group (eg, anilino group, N-methylanilino group, etc.), acylamino group (eg, acetylamino group, propionylamino group, etc.), hydroxyl group, sulfonamide group For example, methanesulfonamide group, benzenesulfonamide group, etc.), sulfamoylamino group (eg, dimethylsulfamoylamino group, etc.), sulfonyl group (eg, methanesulfonyl group, butanesulfonyl group, phenylsulfonyl group, etc.), Sulfamoyl group (eg, ethylsulfamoyl group, dimethylsulfamoyl group, etc.), sulfonylamino group (eg, methanesulfonylamino group, benzenesulfonylamino group, etc.), ureido group (eg, 3-methylureido group, 3, 3-dimethylureido group, 1,3-dimethylureido group etc.), imide group (eg phthalimide group etc.), alkylthio group (eg methylthio group, ethylthio group, n-butylthio group etc.), arylthio group (eg phenylthio) Group) etc. It is.

  X represents a sugar residue or a divalent linking group containing at least one sugar residue, and the sugar residue is preferably a monosaccharide or oligosaccharide having 1 to 10, particularly 1 to 5 sugar units, such as glucose, Hexasaccharides such as mannose, galactose, glucosamine, mannosamine, galactosamine, pentoses such as arabinose, xylose, ribose, maltose, lactose, trehatose, cellobiose, isomaltose, gentiobiose, melibiose, laminaribiose, chitobiose, mannobiose, mannobiose Hydrolysates such as starch, cellulose, chitin, chitosan, etc. Pharmacopoeia String, Acro dextrin, Buritesshu gum, Cerro dextrin and the like), and the like. The phrase “having a sugar residue as a partial structure” means that the sugar residue is bonded directly or via a divalent or higher valent linking group. The divalent or higher valent linking group includes, for example, an alkylene group ( For example, methylene, 1,2-ethylene, 1,3-propylene, 1,4-butylene, cyclohexane-1,4-diyl, etc.), alkenylene groups (for example, ethene-1,2-diyl, butadiene-1,4) A linking group derived from a compound containing at least one aromatic group (for example, ethyne-1,2-diyl, butane-1,3-diyne-1,4-diyl). For example, substituted or unsubstituted benzene, condensed polycyclic hydrocarbons, aromatic heterocycles, aromatic hydrocarbon ring assemblies, aromatic heterocycle assemblies, etc., heteroatom linking groups (oxygen, sulfur, nitrogen, silicon, lithium, etc.) Atom etc.) and the like, preferably, an alkylene group and a group linking a heteroatom. These linking groups may be further combined to form a composite group.

  Hereinafter, although the compound represented by General formula (1)-(3) of this invention is illustrated, it is not limited to these.

  The compounds represented by the general formulas (1) to (3) of the present invention (hereinafter also referred to as ultraviolet absorbers according to the present invention) function as ultraviolet absorbers, but are necessary when mixed with other transparent polymers. Depending on the case, a low molecular compound, a high molecular compound, an inorganic compound or the like can be used together. For example, it is one of the preferable embodiments that additives such as an antioxidant, a plasticizer, and a flame retardant are mixed at the same time.

  The method for adding the ultraviolet absorbent according to the present invention to the optical film may be contained in the optical film or may be applied onto the optical film. When contained in an optical film, it may be added directly.

The amount of the ultraviolet absorber according to the present invention is not uniform depending on the type of compound, use conditions, etc., but in the case of an ultraviolet absorber, 0.2 to 8.0 g per 1 m ² of the optical film is preferable. 0.4 to 5.0 is more preferable, and 1.0 to 3.0 is particularly preferable. Furthermore, from the viewpoint of preventing liquid crystal deterioration, those having excellent ultraviolet absorption performance at a wavelength of 380 nm or less and low visible light absorption of 400 nm or more are preferable from the viewpoint of good liquid crystal display properties. In the present invention, the transmittance at a wavelength of 380 nm is particularly preferably 8% or less, more preferably 4% or less, and particularly preferably 1% or less.

  Moreover, in this invention, a conventionally well-known ultraviolet absorber can also be used together. Although it does not specifically limit as a conventionally well-known ultraviolet absorber, For example, a salicylic acid type ultraviolet absorber (phenyl salicylate, p-tert-butyl salicylate, etc.) or a benzophenone type ultraviolet absorber (2,4-dihydroxybenzophenone, 2, 2) '-Dihydroxy-4,4'-dimethoxybenzophenone, etc.), benzotriazole ultraviolet absorbers (2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 -(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-amyl-phenyl) benzo Triazole, etc.), cyanoacrylate UV absorber (2'-ethylhexyl-2- Ano-3,3-diphenyl acrylate, ethyl-2-cyano-3- (3 ', 4'-methylenedioxyphenyl) -acrylate, etc.), triazine ultraviolet absorbers, or JP-A-58-185777, the same Examples thereof include compounds described in 59-149350, nickel complex compounds, and inorganic powders.

  Conventionally known ultraviolet absorbers used together with the ultraviolet absorber according to the present invention include benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers that are highly transparent and excellent in preventing deterioration of polarizing plates and liquid crystal elements. Benzotriazole-based UV absorbers that are less preferred and less colored are particularly preferred.

(Method for producing cellulose ester film)
Subsequently, the manufacturing method of the cellulose-ester film which is a preferable aspect of this invention is demonstrated.

  As a film-forming process used for the production of the cellulose ester film according to the present invention, the melt-casting is performed by heating and melting the cellulose ester to a temperature showing fluidity without using a solvent, and then casting the fluid cellulose ester. is there. 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. Here, after the film constituent material is heated to develop its fluidity, it is extruded onto a drum or an endless belt.

(Cellulose ester; cellulose acylate)
As the cellulose ester used in the present invention, a lower fatty acid ester of cellulose is preferably used.

  The lower fatty acid in the lower fatty acid ester of cellulose ester means a fatty acid having 6 or less carbon atoms, such as cellulose acetate, cellulose propionate, cellulose butyrate, etc., and JP-A Nos. 10-45804 and 8- Examples of lower fatty acid esters of cellulose include mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in US Pat. No. 2,176,61 and US Pat. No. 2,319,052. Among the above fatty acids, cellulose acetate and cellulose acetate propionate are preferably used. In the case of the cellulose ester film according to the present invention, those having a polymerization degree of 250 to 400 are particularly preferably used from the viewpoint of film strength.

  In the present invention, the cellulose acylate constituting the optical film is a cellulose acylate having an aliphatic acyl group having 2 or more carbon atoms, and the cellulose acylate has a total acyl group carbon number of 6.2 or more and 7. It is a cellulose acylate which is 5 or less. The acyl group total carbon number of cellulose acylate is preferably 6.5 or more and 7.2 or less, and more preferably 6.6 or more and 7.1 or less. However, the acyl group total carbon number is the sum of products of the substitution degree of each acyl group in the cellulose acylate and the carbon number. Furthermore, the number of carbon atoms of the aliphatic acyl group is preferably 2 or more and 6 or less from the viewpoint of productivity and cost of cellulose synthesis. The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

  Examples of the acyl group include an acetyl group, a propionyl group, a butyryl group, a pentanate group, and a hexanate group. Examples of the cellulose acylate include cellulose propionate, cellulose butyrate, and cellulose pentanate. Further, mixed fatty acid esters such as cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate pentanate may be used as long as the above-mentioned side chain carbon number is satisfied. Among these, cellulose acetate propionate and cellulose acetate butyrate are particularly preferable. Note that triacetyl cellulose and diacetyl cellulose, which are cellulose acylates generally used in solution casting film formation, do not satisfy the condition of the number of side chain carbon atoms, and thus are not included in the present invention.

  In general, the mechanical properties and saponification properties of a cellulose acylate film and the melt film-forming property of cellulose acylate are in a trade-off relationship with respect to the total substitution degree of acyl groups of cellulose acylate. For example, in cellulose acetate propionate, when the total substitution degree of acyl groups is increased, mechanical properties are lowered and melt film-forming properties are improved. In the present invention, it was found that the film mechanical properties, saponification properties, and melt film-forming properties can be achieved by adjusting the total number of acyl groups of cellulose acylate to 6.5 or more and 7.2 or less. Although details of this mechanism are unknown, it is presumed that the influence on film mechanical properties, saponification properties, and melt film-forming properties varies depending on the number of carbon atoms of the acyl group. That is, in the case of the same substitution degree, a long-chain acyl group such as a propionyl group or a butyryl group becomes more hydrophobic than an acetyl group, thereby improving melt film-forming properties. Therefore, when achieving the same melt film-forming property, the substitution degree of propionyl group and butyryl group may be lower than that of acetyl group, so that it is presumed that the deterioration of mechanical properties and saponification properties can be suppressed.

  In addition, the substitution degree of the acyl group of cellulose acylate is described in Carbohydr. Res. 273 (1995) 83-91 (Tezuka et al.).

  The cellulose acylate used in the present invention has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.0 to 5.5, particularly preferably 1.4 to 5.0, and more preferably. 2.0-3.0. Mw is preferably 100,000 to 500,000, and more preferably 150,000 to 300,000.

The average molecular weight and molecular weight distribution of cellulose acylate can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight and the weight average molecular weight are calculated. The measurement conditions are as follows.
Solvent: Methylene chloride column: Shodex K806, K805, K803 (used by connecting 3 products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. It is preferable that the 13 samples are substantially equally spaced.

  The cellulose acylate 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. Cellulose acylates made from these can be used in appropriate mixture or singly.

  For example, the ratio of cellulose acylate derived from cotton linter: cellulose acylate derived from wood pulp (conifer): cellulose acylate 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 I can do it.

  Cellulose acylate can be obtained, for example, by substituting the hydroxyl group of the raw material cellulose with acetic anhydride, propionic anhydride and / or butyric anhydride in the usual manner using the acetyl group, propionyl group and / or butyl group within the above range. It is done. The method for synthesizing such cellulose acylate is not particularly limited, and for example, it can be synthesized with reference to the method described in JP-A-10-45804 or JP-A-6-501040.

  The degree of substitution of acyl groups such as acetyl, propionyl and butyl groups can be measured according to ASTM-D817-96.

  In addition, cellulose acylate is industrially synthesized using sulfuric acid as a catalyst, but this sulfuric acid is not completely removed, and the residual sulfuric acid causes various decomposition reactions during melt film formation, resulting in cellulose obtained. In order to affect the quality of the acylate film, the residual sulfuric acid content in the cellulose acylate used in the present invention is in the range of 0.1 to 40 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts. If the residual sulfuric acid content exceeds 40 ppm, the deposit on the die lip during heat melting increases, such being undesirable. Moreover, since it becomes easy to fracture | rupture at the time of slitting at the time of hot drawing or after hot drawing, it is not preferable. A smaller amount is preferable, but if it is less than 0.1, it is not preferable because the burden of the cellulose acylate washing step becomes too large, and it is not preferable because it may easily break. This is not well understood, although an increase in the number of washings may affect the resin. Furthermore, the range of 0.1-30 ppm is preferable. The residual sulfuric acid content can be similarly measured by ASTM-D817-96.

Further, the total residual acid amount including other (such as acetic acid) residual acids is preferably 1000 ppm or less, more preferably 500 ppm or less, and even more preferably 100 ppm or less.
By washing the synthesized cellulose acylate more thoroughly than when used in the solution casting method, the residual acid content can be within the above range, and a film is produced by the melt casting method. In this case, adhesion to the lip portion is reduced, and a film having excellent flatness can be obtained, and a film having good dimensional change, mechanical strength, transparency, moisture resistance, Rt value and Ro value described later can be obtained. it can. For washing cellulose acylate, in addition to water, a poor solvent such as methanol or ethanol, or, as a result, a mixed solvent of a poor solvent and a good solvent can be used if it is a poor solvent. , Low molecular organic impurities can be removed. Furthermore, the cellulose acylate is preferably washed in the presence of an antioxidant such as a hindered amine or a phosphite, which improves the heat resistance and film formation stability of the cellulose acylate.

  Also, in order to improve the heat resistance, mechanical properties, optical properties, etc. of cellulose acylate, dissolve it in a good solvent of cellulose acylate and re-precipitate it in a poor solvent to remove low molecular weight components and other impurities of cellulose acylate. I can do it. At this time, it is preferable to carry out in the presence of an antioxidant as in the case of washing cellulose acylate. Furthermore, another polymer or a low molecular weight compound may be added after the reprecipitation treatment of cellulose acylate.

The intrinsic viscosity of cellulose acylate is preferably 1.5 to 1.75 g / cm ³ , and more preferably 1.53 to 1.63.

  Moreover, it is preferable that the cellulose acylate used in the present invention has a small amount of bright spot foreign matter when formed into a film. A bright spot foreign material is an arrangement in which two polarizing plates are arranged orthogonally (crossed Nicols), a cellulose acylate film is placed between them, light from a light source is applied from one side, and cellulose acylate is applied from the other side. When the rate film is observed, the light from the light source appears to leak. At this time, the polarizing plate used for the evaluation is desirably composed of a protective film having no bright spot foreign matter, and a polarizing plate using a glass plate for protecting the polarizer is preferably used. The bright spot foreign matter is considered to be one of the causes due to the unacetylated or low acetylated cellulose contained in the cellulose acylate, and the cellulose acylate with a little bright spot foreign matter is used (the cellulose acylate having a small dispersion of substitution degree). And at least one of the process of late synthesis of cellulose acylate and the process of obtaining precipitates, once in the solution state, the bright spot via the filtration step in the same way Foreign matter can also be removed. Since the molten resin has a high viscosity, the latter method is more efficient.

As the film thickness decreases, the number of bright spot foreign matter per unit area decreases, and as the cellulose acylate content in the film decreases, the bright spot foreign matter tends to decrease. The diameter of 0.01 mm or more is preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, more preferably 50 pieces / cm ² or less, and 30 pieces / cm ² or less. Preferably, it is preferably 10 / cm ² or less, but most preferably none. Moreover, it is preferable that it is 200 pieces / cm < ² > or less also about a bright spot of 0.005-0.01 mm or less, Furthermore, it is preferable that it is 100 pieces / cm < ² > or less, and it is 50 pieces / cm < ² > or less. The number is preferably 30 pieces / cm ² or less, more preferably 10 pieces / cm ² or less, and most preferably none.

  When removing bright spot foreign matter by melt filtration, filter the cellulose acylate composition to which a plasticizer, a deterioration inhibitor, an antioxidant, etc. are added and mixed rather than filtering the melted cellulose acylate alone. However, it is preferable because the removal efficiency of bright spot foreign matter is high. Of course, it may be dissolved in a solvent during the synthesis of cellulose acylate and reduced by filtration. It is possible to filter a mixture of UV absorbers and other additives as appropriate. Filtration is preferably performed with a melt containing cellulose acylate having a viscosity of 1000 Pa · s or less, more preferably 500 Pa · s or less, still more preferably 100 Pa · s or less, and 50 Pa · s or less. More preferably it is. As the filter medium, conventionally known materials such as glass fibers, cellulose fibers, filter paper, and fluorine resins such as tetrafluoroethylene resin are preferably used, and ceramics and metals are particularly preferably used. The absolute filtration accuracy is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 10 μm or less, and even more preferably 5 μm or less. These can be used in combination as appropriate. The filter medium can be either a surface type or a depth type, but the depth type is preferably used because it is relatively less clogged.

  In another embodiment, the cellulose acylate as a raw material may be dissolved in a solvent at least once and then dried. In that case, cellulose acylate which is dissolved in a solvent together with at least one of a plasticizer, an ultraviolet absorber, a deterioration inhibitor, an antioxidant and a matting agent and then dried is used. As the solvent, a good solvent used in a solution casting method such as methylene chloride, methyl acetate or dioxolane can be used, and a poor solvent such as methanol, ethanol or butanol may be used at the same time. In the process of dissolution, it may be cooled to -20 ° C or lower, or heated to 80 ° C or higher. When such a cellulose acylate is used, it is easy to make each additive uniform when melted, and the optical characteristics may be made uniform.

  The optical film of the present invention may be obtained by appropriately mixing polymer components other than cellulose acylate. The polymer component to be mixed is preferably one having excellent compatibility with cellulose acylate, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more.

(Plasticizer)
A plasticizer can be added to the optical film of the present invention. 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.

  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.

  In the optical film of the present invention, in addition to the plasticizer, an additive exhibiting the same action as the plasticizer can be contained. As these additives, for example, if it is a low molecular weight organic compound capable of plasticizing a cellulose ester film, the same effect as the plasticizer can be obtained. These components are not added for the purpose of directly plasticizing the film as compared with the plasticizer, but exhibit the same action as the plasticizer depending on the amount.

(dye)
In the present invention, for example, a blue dye may be used as an additive in order to adjust the color of the film. A preferred dye is an anthraquinone dye. The anthraquinone dye can have an arbitrary substituent at positions 1 to 8 of the anthraquinone. Preferable substituents include an anilino group, a hydroxyl group, an amino group, a nitro group, or a hydrogen atom that may be substituted. The addition amount of the films of these dyes, 0.1 to 1000 / m ² to maintain the transparency of the film is preferably 10-100 [mu] g / m ^2.

(Stabilizer)
In the cellulose ester film according to the present invention, at least one selected from a phenol-based stabilizer, a hindered amine-based stabilizer, a phosphorus-based stabilizer, and a sulfur-based stabilizer, or two or more additional stabilizers are added. May be.

  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-t-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. Is 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 STAB LA-52 manufactured by Ciba Specialty Chemicals Inc. Sumilezer GP manufactured by Asahi Denka Kogyo Co., Ltd. PEP- 24G: manufactured by Asahi Denka Kogyo Co., Ltd. Sumilezer TP-D: manufactured by Sumitomo Chemical Co., Ltd. These stabilizers can be used alone or in combination of two or more with respect to the phosphites. The amount is appropriately selected within a range not impairing the object of the present invention, but is usually 0.001 to 10.0 parts by mass, preferably 0.01 to 5.0 parts by mass, with respect to 100 parts by mass of the cellulose ester. More preferably, it is 0.1-3.0 mass parts.
The cellulose ester having a water content of 3.0% by mass or less 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. .

(Matting agent)
It is preferable to add fine particles as a matting agent to the optical film of the present invention. As fine particles used in the present invention, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, Mention may be made of aluminum silicate, magnesium silicate and calcium phosphate.

  As a primary particle average diameter of silicon dioxide fine particles, 5 to 16 nm is more preferable, and 5 to 12 nm is more preferable. A smaller primary particle average diameter is preferred because haze is low. The apparent specific gravity is preferably 90 to 200 g / liter, and more preferably 100 to 200 g / liter. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

The amount of the matting agent added is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and particularly preferably 0.10 to 0.18 g per 1 m ² .

  Examples of the silicon dioxide fine particles include AEROSIL R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 manufactured by Nippon Aerosil Co., Ltd. Among them, AEROSIL200V and R972V are primary average particles. Silicon dioxide fine particles having a diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more are particularly preferable because they have a large effect of reducing the friction coefficient while keeping the turbidity of the optical film low.

  The fine particles of zirconium oxide are commercially available under the trade names of Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used. Examples of the polymer include silicone resin, fluorine resin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  These fine particles usually preferably form secondary particles having an average particle diameter of 0.01 to 1.0 μm, more preferably 0.1 to 0.8 μm, and most preferably 0.2 to 0.5 μm. These fine particles exist as aggregates of primary particles in the film, and form irregularities of 0.01 to 1.0 μm on the film surface. The content of these fine particles is preferably 0.005 to 0.3% by mass, more preferably 0.05 to 0.2% by mass, and most preferably 0.1 to 0.2% by mass with respect to the optical film.

(Structure and characteristics as an optical film)
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 hetero 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.

  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 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.

  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.

  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.

  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.

  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 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.

(Polarizing plate and liquid crystal display)
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.

  In a liquid crystal display device, a substrate containing liquid crystal is usually arranged between two polarizing plates. However, a polarizer protective film to which the optical film of the present invention is applied has high dimensional stability, so it can be placed at any position. Excellent display properties can be obtained. A polarizer protective film provided with a clear hard coat layer, an antiglare layer, an antireflection layer and the like is preferably used for this part as the polarizer protective film on the outermost surface of the display side of the liquid crystal display device. In the case of a polarizer protective film provided with an optical compensation layer, or a polarizer protective film imparted with an appropriate optical compensation capability by stretching operation, etc. 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.

[Synthesis example of cellulose acylate]
Although the synthesis method of the cellulose ester of this invention is demonstrated concretely below, this invention is not limited by these.

<Synthesis Example 1>
540 g of acetic acid was added to 30 g of cellulose (dissolved pulp manufactured by Nippon Paper Industries Co., Ltd.) and stirred at 54 ° C. for 30 minutes. After the mixture was cooled, esterification was performed by adding 150 g of acetic anhydride and 1.2 g of sulfuric acid cooled in an ice bath. Stirring was performed for 150 minutes while adjusting the esterification so as not to exceed 40 ° C. After completion of the reaction, a mixture of 30 g of acetic acid and 10 g of water was added dropwise over 20 minutes to hydrolyze excess anhydride. While maintaining the temperature of the reaction solution at 40 ° C., 90 g of acetic acid and 30 g of water were added and stirred for 1 hour. The mixture was poured into an aqueous solution containing 2 g of magnesium acetate, stirred for a while and then filtered and dried to obtain cellulose acylate C-1. The degree of acetyl substitution was 2.80, and the weight average molecular weight was 220,000.

<Synthesis Examples 2-8>
Using acetic acid, acetic anhydride, propionic acid, propionic anhydride, butyric acid, butyric anhydride described in Table 1, the same operation as in Synthesis Example 1 was performed,
Cellulose acylates C-2 to C-8 were obtained.

Acyl group substitution degree Ac: acetyl group, Pr: propionyl group, Bu: butyryl group Fatty acid I: acetic acid II: propionic acid or butyric acid anhydrous fatty acid I: acetic anhydride II: propionic anhydride or n-butyric anhydride Mw: weight average molecular weight The weight average molecular weight was measured by GPC HLC-8220 (manufactured by Tosoh Corporation).

<Synthesis Examples 9 to 26>
Similarly to Synthesis Example 1, cellulose acylates C-9 to C-26 listed in Table 2 were obtained using the corresponding fatty acids and anhydrous fatty acids.

  Hereinafter, although the example of the present invention is concretely explained by an example, the present invention is not limited by these. In addition, “part” described below represents “part by mass”.

Example 1
[Production of cellulose ester film]
<Film F-1>
A schematic flow sheet showing one embodiment of an apparatus for carrying out the method for producing a cellulose acylate film of the present invention is shown in FIG. 1, and the production method will be described with reference to FIG.

  Cellulose acylate C-1 100 parts by mass, stabilizer A-1 1.0 part by mass, UV absorber comparative compound 1 2.0 parts by mass, matting agent Aerosil R972V 0.3 part by mass, 90 ° C. 5 hours It was dried under reduced pressure. Next, 15 parts by mass of a plasticizer TPP was added and mixed, and this cellulose acylate composition was melted at a temperature of 260 ° C. using a melt extruder and extruded from the casting die 4 onto the first cooling roll 5. A film was sandwiched between the first cooling roll 5 and the touch roll 6 to form. The heat bolt was adjusted so that the gap width of the casting die 4 was 0.5 mm within 30 mm from the end in the width direction of the film and 1 mm at other places. The touch roll 6 flowed 80 ° C. water as cooling water therein. From the position P1 at which the resin extruded from the casting die 4 contacts the first cooling roll 5 to the position P2 at the upstream end in the rotation direction of the first cooling roll 5 in the nip between the first cooling roll 5 and the touch roll 6. 1 The length L along the circumferential surface of the cooling roller 5 was set to 20 mm. However, it was difficult to melt and could not be stably formed into a film.

<Films F-2 to F-36>
Cellulose acylate listed in Table 3 100 parts by mass, plasticizer 15 parts by mass, stabilizer-1 1.0 part by mass, stabilizer-2 1.0 part by mass and UV absorber, matting agent Aerosil R972V 0.3 part by mass The film F-2 to F-36 were produced by performing the same operation as the film F-1 at the melting temperatures shown in Table 3. The extrusion amount and take-up speed were adjusted so that the film thickness was 80 μm. The materials used are as follows.

(Plasticizer)
TPP: Triphenyl phosphate TMP: Trimethylolpropane tribenzoate PETB: Pentaerythritol tetrabenzoate (stabilizer)
A-1. IRGANOX-1010 (Ciba Specialty Chemicals)
A-2. Tinuvin 144 (Ciba Specialty Chemicals)
A-3. Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.)
A-4. LA-52 (Asahi Denka Kogyo Co., Ltd.)

  The samples F-1 to F-36 produced as described above were evaluated as described below.

[Evaluation of UV absorption performance]
Using Spectrophotometer U-3200 (manufactured by Hitachi, Ltd.), the spectral absorption spectrum of each optical film was measured, the transmittances at 400 nm and 380 nm were determined, and the ranking was performed as follows. In each rank, the higher the transmittance at 400 nm, the better, and the lower the transmittance at 380 nm, the better.

(400 nm transmittance)
A: Transmittance 80% or more B: Transmittance 70% or more and less than 80% C: Transmittance 60% or more and less than 70% D: Transmittance less than 60% (380 nm transmittance)
A: Transmittance less than 5% B: Transmittance 5% or more and less than 8% C: Transmittance 8% or more and less than 10% D: Transmittance 10% or more [Durability: Evaluation of bleed out]
Each optical film was allowed to stand for 1000 hours in a high-temperature and high-humidity atmosphere at 80 ° C. and 90% RH, and then visually observed for the presence or absence of bleed-out (crystal precipitation) on the surface of the optical film. Evaluation was performed.
(Double-circle): Generation | occurrence | production of bleeding out is not recognized at all on the optical film surface.
○: Slight partial bleed out is observed on the optical film surface.
Δ: Slight bleed out is observed over the entire surface of the optical film.
X: A clear bleed-out is recognized over the entire surface of the optical film.

[Retardation coefficient of variation (CV)]
The surface layer is peeled off from the molded film, the retardation is measured at intervals of 1 cm in the width direction of the obtained cellulose ester film, and expressed by the variation coefficient (CV) of the retardation obtained from the following formula. is there. 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
In the formula, d is the thickness (nm) of the film, the refractive index nx (the maximum refractive index in the plane of the film, also referred to as the refractive index in the slow axis direction), ny (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% ×: variation (CV) is 10% or more [Haze Evaluation]
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.

[Evaluation of light resistance]
Following the alkali saponification treatment of each optical film according to the method described below, a polarizing plate is prepared, and the parallel transmittance (H0) and the direct transmittance (H90) of the untreated sample are measured. The degree of polarization was calculated. After that, each polarizing plate was subjected to a forced deterioration treatment under the conditions of 500 hours without a sunshine weather meter and without a UV cut filter, and then again the parallel transmittance (H0 ′) and the direct transmittance (H90 ′) after the deterioration treatment. Was measured, polarization degrees P0 and P500 were calculated according to the following formula, and the degree of polarization degree change was determined by the following formula.

<Alkali saponification treatment>
Saponification step: 2 mol / L NaOH 50 ° C. 90 seconds water washing step: water 30 ° C. 45 seconds neutralization step: 10% by mass HCl 30 ° C. 45 seconds water washing step: water 30 ° C. 45 seconds Each sample was saponified under the above conditions. Washing with water, neutralization and washing with water were carried out in this order, followed by drying at 80 ° C.

<Preparation of polarizing plate>
A 120 μm-thick polyvinyl alcohol film was immersed in 100 kg of an aqueous solution containing 1 kg of iodine and 4 kg of boric acid, and stretched 6 times at 50 ° C. to form a polarizing film. Samples subjected to the above alkali saponification treatment were bonded to both surfaces of this polarizing film, respectively, using a completely saponified polyvinyl alcohol 5% aqueous solution as an adhesive to produce polarizing plates.

<Calculation of degree of polarization P0, P500>
Polarization degree P0 = [(H0−H90) / (H0 + H90)] ^1/2 × 100
Polarization degree P500 = [(H0′−H90 ′) / (H0 ′ + H90 ′)] ^1/2 × 100
Polarization degree change = P0−P500
P0: Polarization degree before forced deterioration P500: Polarization degree after 500 hours of forced deterioration treatment <Determination of light resistance>
The amount of change in the degree of polarization obtained as described above was determined according to the criteria described below, and light resistance was evaluated.
◎: Polarization degree change less than 10% ○: Polarization degree change more than 10% and less than 25% ×: Polarization degree change more than 25% [Evaluation of pressed failure]
The presence or absence of foreign matter precipitation was visually observed on the first roll, the second roll, and the third roll. In addition, the peeled film was visually observed for the presence or absence of a pattern (pressed failure) due to foreign matter transfer onto the film.
○: Pushed without precipitates and no failure Δ: Precipitates are seen a little, and pushed and failures are seen a little ×: Precipitates are present. Table 4 shows the results obtained as described above.

  As is apparent from Table 4, the cellulose ester film containing the ultraviolet absorbent according to the present invention is superior to the comparative example in any of UV absorption performance, haze characteristics, light resistance, retardation variation coefficient, and pushing failure. Furthermore, it can be seen that the optical film combined with cellulose according to the present invention is pressed and has excellent failure.

Example 2
Carefully peel off the polarizing plate of a commercially available portable device (Sharp personal mobile tool Zaurus model name: MI-L1) equipped with a reflective TFT color liquid crystal display device, and here each polarizing plate produced in Example 1 The polarization direction was matched and attached to the liquid crystal display panel. As a result of visually evaluating the contrast of each liquid crystal display panel, the liquid crystal display panel using the polarizing plate of the present invention has a high contrast over a long period of time with respect to the liquid crystal display panel using the polarizing plate of the comparative example. Was maintained, and there was no unnatural yellowing, and it was confirmed that the color reproducibility was excellent.

It is a general | schematic flow sheet which shows one embodiment of the apparatus which enforces the manufacturing method of the cellulose acylate film of this invention.

Explanation of symbols

4 Casting Die 5 First Roll 6 Touch Roll 7 Second Roll 8 Third Roll 9 Peeling Roll 10 Cellulose Acetate Film 11 Dancer Roll 12 Stretching Machine

Claims (5)

A cellulose ester optical film comprising, as a main component, cellulose acylate containing at least one selected from compounds represented by the following general formulas (1) to (3).

[Wherein, R ₁₁ and R ₁₂ each independently represent a hydrogen atom, a hydroxyl group or an alkoxy group, R ₁₃ , R ₁₄ and R ₁₅ each independently represent a substituent, and R ₁₆ , R ₁₇ and R ₁₈ each represent Independently represents a group having a hydrogen atom or a sugar residue, and at least one of R ₁₆ , R ₁₇ and R ₁₈ represents a group having a sugar residue. l1, m1, and n1 each represents an integer of 0 to 3. ]

[Wherein, R ₂₁ and R ₂₂ each independently represents a hydrogen atom or a substituent, and at least one of R ₂₁ and R ₂₂ represents a group having a sugar residue. p2 represents an integer of 0 to 3, and q2 represents an integer of O to 4. ]

[Wherein, X represents a sugar residue or a divalent linking group containing at least one sugar residue, and A and B represent groups represented by the general formula (4) or (5). May be different. * Is a connection point with X. R ₃₁ and R ₃₂ represent a hydrogen atom or a substituent, and p3 and q3 each represents an integer of 0 to 4. ] 2. The cellulose ester optical film according to claim 1, wherein the total number of acyl groups in the cellulose acylate is 6.2 or more and 7.5 or less.
However, the acyl group total carbon number is the sum of products of the substitution degree of each acyl group in the cellulose acylate and the carbon number of the acyl group. A method for producing a cellulose ester optical film, comprising producing the cellulose ester optical film according to claim 1 by melt casting. A polarizing plate using the cellulose ester optical film according to claim 1. A liquid crystal display device using the cellulose ester optical film according to claim 1.

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