JP4609031B2 - Method for producing optical film for display - Google Patents

Description

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

  Polyester such as PET, and general-purpose resin films such as polyethylene (PE) and polypropylene (PP) are formed by melt extrusion molding. However, it is used as a cellulose ester-based optical film (polarizing plate protective film) such as TAC (triacetyl cellulose). The melt extrusion method has not been used yet.

  Cellulose ester films are usually formed by the solution casting method, but due to the solubility of cellulose esters, a large amount of halogen-based solvent such as methylene chloride is used as a solvent, and there is a problem that the environmental load is large. It has become.

  On the other hand, since the melting method does not use a solvent, it is expected to be a technology that has a low environmental load, a wide width, and a high possibility that the film forming speed can be increased, thereby improving productivity.

  However, since triacetyl cellulose (TAC), which is a raw material for optical films, is a polymer having a melting start temperature higher than the decomposition starting temperature, it has not been achieved to obtain an optical film using the melt casting method.

  On the other hand, a technique for obtaining a cellulose ester film applicable to a photographic support by a melt casting method by substituting not only acetyl groups but also propionyl groups at a specific ratio has been disclosed (for example, patents). Reference 1).

  Patent Document 2 discloses that a polarizer protective film, a polarizer, and a liquid crystal display device having good dimensional stability can be obtained by using a fatty acid cellulose ester such as an acetyl group, a propionyl group, and a butyryl group by a melt casting method. Is disclosed.

  As a supply form of the cellulose ester-based raw material polymer, there are those supplied in powder or flake form. When this powder or flaky raw material polymer is directly melt-extruded, it is colored by drying immediately before melting, soars when supplied to the extruder, or deposited and deposited on the raw material supply part of the extruder. There was a problem that the handling was inferior due to contamination.

  In addition, when powder or flakes are directly melt-extruded, deterioration will increase when the set temperature of the extruder is increased. Therefore, it is necessary to extrude at the lowest possible temperature. There is a problem that an insufficient material becomes a bright spot foreign material, and it is difficult to set an appropriate temperature range.

On the other hand, some cellulose ester-based raw materials are supplied in the form of pellets of 2 to 3 mm. This is a solution-based cellulose ester prepared from pulp or cotton, then dried, heated and melted to form a pellet. Since it has already been heated once at the time of pellet formation, it is further manufactured by melt casting. When heated again in the membrane, the cellulose ester deteriorates by heat, and the molecular weight tends to decrease or yellow, which is not preferable.
Japanese National Patent Publication No. 6-501040 JP 2000-352620 A

  Accordingly, an object of the present invention is to provide an optical film for display having good optical properties by a melt casting method using a raw material polymer of cellulose ester. Another object of the present invention is to provide a production method for producing the above-described high performance optical film for display without using a halogen-based solvent having a high environmental load, and further a polarizing plate and a liquid crystal display using the same as a protective film To provide an apparatus.

  The above problem could be solved by the following configuration.

(Claim 1)
An optical film for display comprising a cellulose ester polymer,
The shape of the raw material polymer is a particle having a particle size of 1 to 10 mm and a bulk specific gravity of 0.1 to 1.0. A method for producing an optical film for a display, which is formed by granulation using a raw material polymer and melt-extruded to form a film using the raw material polymer.

(Claim 2)
In the melt extrusion film formation, the raw polymer is melted in a temperature range of Tg to Tg + 100 ° C. by using a single-screw or twin-screw extruder and extruded from a T die having a flat slit gap. The manufacturing method of the optical film for displays of Claim 1 characterized by the above-mentioned.

(Claim 3)
The method for producing an optical film for display according to claim 1 or 2, wherein the raw material polymer is at least one cellulose ester selected from cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate.

  When powders and flakes are directly fed to a melt extruder, air is often involved and bubbles are formed in the molded product. By using granulated products, stable extrusion can be achieved. .

  Additives such as antioxidants and heat stabilizers are often added to prevent deterioration, but a uniform mixture can be obtained by mixing the raw material polymer and additives during granulation. And was able to.

  By using a granulated product having a particle size in the range of the present invention, drying before casting was facilitated, melting became uniform, and deterioration and bright spot foreign matter were satisfied. There was no uplift due to the powder and the handleability was good.

  The present invention is described in detail below.

[Melt casting method]
The present invention is characterized by using a cellulose film formed by melt casting as an optical film. In the present invention, melting and casting is defined as melting and casting a film constituent material without using the solvent used for solution casting.

  More specifically, the heat 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, a stretch molding method, and the like. Among these, in order to obtain an optical film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent.

  The melt casting method of the present invention includes a method in which the film forming material is heated to exhibit its fluidity and then extruded and formed on a drum or an endless belt as a melt casting film forming method.

(Cellulose ester)
The cellulose resin according to the present invention is a single or mixed acid ester of cellulose which shows a structure of a cellulose ester and contains at least one of a fatty acyl group and a substituted or unsubstituted aromatic acyl group.

  The cellulose ester constituting the optical film of the present invention is at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. It is preferable that

  Among these, particularly preferable cellulose esters include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

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

Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Of these, cellulose acetate propionate is particularly preferably used. Among them, 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 are preferable. The portion not substituted with the acyl group is usually present as a hydroxyl group. These can be synthesized by known methods.

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

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

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

[Raw polymer shape]
<Particle size / size distribution>
The shape of the raw material polymer has a particle size of 1 to 10 mm when the particle size distribution is measured, the average particle size is between 1 and 10 mm, and 90% by mass or more of the particles are in the range of 1 to 10 mm. Say. The particle size distribution can be measured, for example, using a particle size distribution measuring device such as Nikkiso Co., Ltd. particle size distribution measuring device Microtrac MT3000, Shimadzu Corporation SALD-2000A.

  Moreover, after dispersing a raw material polymer in water, it can be measured by taking a micrograph and analyzing the image.

<Bulk specific gravity>
The bulk specific gravity of the raw material polymer can be obtained by measuring the mass of the powder filled in a container having a known volume. For example, Tsutsui Rika Instruments Co., Ltd. B. By using a dedicated measuring instrument such as a D powder characteristic measuring instrument, the measurement can be performed easily and with high accuracy.

  In the present invention, the bulk specific gravity of 0.1 to 1.0 means that Tsutsui Rika Instruments Co., Ltd. B. It means that the loosely packed bulk specific gravity measured using the D powder characteristic measuring device takes a value between 0.1 and 1.0.

  If the bulk specific gravity is less than 0.1, it becomes fluffy, and handling such as transportation and weighing is extremely bad. When it is larger than 1.0, a problem occurs in that the storage silo is in a compacted state and cannot be discharged by bridging. Therefore, it is necessary to be within the scope of the present invention.

<Granulation>
The granulation as used in the present invention is a method of extruding and cutting from a screen having a desired shape by applying pressure as it is in a powder form, extruding from a screen having a desired shape by kneading with a biaxial rotor at a temperature below the melting point. Including a method, etc., a method of melting by applying a temperature equal to or higher than the melting point and extruding into a strand form from a die with a twin-screw or single-screw extruder and cutting it is not included.

  Since it deteriorates when melted, it is intended by the present invention to granulate without melting.

  The shape of the granulated body is not particularly limited, such as a cylindrical shape, a spherical shape, a rectangular parallelepiped shape, and an indefinite shape. Although it depends on the granulation mechanism of the granulator, when measuring the particle size of the granulated material, the total of those smaller than 1 mm and larger than 10 mm needs to be less than 10% by mass. The size is determined according to the screw diameter of the extruder.

  When granulating, it is granulated by applying a certain pressure. Furthermore, granulation may be performed by applying a temperature below the melting point of the polymer.

  When granulating, additives such as a plasticizer, an antioxidant, a heat stabilizer, a slipping agent and the like described later can be mixed and granulated. When an additive having a melting point lower than the granulation temperature is added, the powders are kneaded and hardened, and can be easily granulated without applying a large pressure.

  As the granulator, a commercially available one can be used. For example, Fuji Paudal Co., Ltd. disk pelleter F-5 to 440, Nippon Steel Works Co., Ltd. large granulator CMP, CIM series, etc., Examples include press pelleters FMP-180N to 800N manufactured by Chiyoda Giken Co., Ltd., and cylindrical granulators FG-250 to 600 manufactured by Fukae Powtex Co., Ltd.

[Removal of volatile components]
Film formation by the melt casting method is remarkably different from the solution casting method, and if the volatile component is present in the material to be cast, the flatness and transparency of the film for ensuring the function as a film or retardation film can be ensured. It is not preferable from the point. This is because transparency deteriorates when volatile components are mixed into the formed film, and when a film is formed by extrusion from a die-slit, the film surface becomes a factor that causes streaking and induces deterioration in flatness. There are things to do. Therefore, when a film constituent material is formed into a film, it is not preferable that a component that volatilizes exists in a region lower than the melting temperature for film formation from the viewpoint of avoiding generation of a volatile component during heating and melting.

  Examples of the volatile component include moisture absorbed by any of the film constituent materials, or a solvent mixed before the material is purchased or at the time of synthesis, and includes volatilization caused by evaporation, sublimation, or decomposition by heating. The solvent here is different from the solvent for preparing the resin as a solution as a solution casting, and is contained in a trace amount in the film constituting material. Therefore, selection of the film constituent material is important in avoiding the generation of volatile components.

  It is preferable that the film constituent material used for the melt casting of the present invention removes volatile components represented by the moisture and the solvent before film formation or during heating. As this removal method, a so-called known drying method can be applied, and it can be performed by a method such as a heating method, a decompression method, a heating decompression method, etc., or even in an atmosphere in which nitrogen is selected as the inert gas. Good. When these known drying methods are performed, it is preferable in terms of film quality to be performed in a temperature range where the film constituting material does not decompose.

  For example, the moisture or solvent remaining after the removal in the drying step is 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably based on the total mass of the film constituent materials. Is 1% by mass or less.

  The drying temperature at this time can reduce the generation of volatile components by drying before film formation, and the resin alone, or at least one mixture or compatible of the resin and the film constituting material other than the inner resin. The product can be divided and dried. The preferable drying temperature 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 higher and (Tg−5) ° C. or lower. 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 removal rate of volatile components may be low, or it may take too long to dry, and when Tg is present in the material to be dried, heating to a drying temperature higher than Tg will cause the material to It may be difficult to handle due to fusion.

  The drying process may be separated in two or more stages. For example, the film may be formed through storage of the material in the preliminary drying process and a previous drying process performed immediately before film formation to one week before film formation.

(Additive)
An additive can be added before or during the heat melting of the raw material polymer of the cellulose ester of the present invention.

  Examples of additives include plasticizers, antioxidants, acid scavengers, light stabilizers, peroxide decomposers, radical scavengers, metal deactivators, ultraviolet absorbers, matting agents, dyes, and pigments. . Moreover, if it has the said function, the additive which is not classified into this is also used.

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

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

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

  Further, the presence of the above-mentioned additives is not preferable as an optical film such as transmittance and haze value generated by suppressing the generation of colored substances in the visible light region at the time of heating and melting, or by mixing volatile components into the film. It is excellent in that the performance can be suppressed or eliminated.

  In the present invention, the display image of the liquid crystal display device has an influence when the haze value exceeds 2% when the optical film of the present invention is used. Therefore, the haze value is preferably less than 1%, more preferably less than 0.5%. is there. As an index of colorability, yellowness (yellow index, YI) can be used, preferably 3.0 or less, more preferably 1.0 or less.

  The optical film for display of the present invention preferably has a transmittance of 85% or more.

  In the step of imparting retardation during film production, it is possible to suppress the deterioration of the strength of the film constituting material or to maintain the strength inherent to the material. If the film constituent material becomes brittle due to significant deterioration, breakage is likely to occur in the stretching step, and the retardation value may not be controlled.

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

  In addition, since the optical film of the present invention is used as a polarizing plate protective film, it is described above in the film constituting material from the viewpoint of improving the storage stability with time with respect to the polarizing plate of the present invention and the polarizer constituting the polarizing plate. The presence of additives plays an important role.

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

  Hereinafter, the additive will be described in more detail.

(Plasticizer)
It is preferable to add a compound known as a plasticizer to the optical film of the present invention 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 has a lower elastic modulus or viscosity due to the absorption of heat at a glass transition temperature or higher, and exhibits fluidity. In order to melt the film constituent material, the plasticizer to be added preferably has a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester in order to satisfy the above object.

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

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

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

  Phosphate ester plasticizers: Specifically, phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclobenthyl phosphate and cyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate And phosphoric acid aryl esters such as cresyl phenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted. 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 phosphate ester may be part of the polymer, or may be regularly pendant, and also introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be. Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

  Ethylene glycol ester plasticizer: Specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropyl carboxylate, ethylene glycol dicyclohexyl carboxylate and the like Examples include ethylene glycol cycloalkyl ester plasticizers and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di4-methylbenzoate. These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted. Further, 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 plasticizers: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, glycerol cycloalkyl esters such as glycerol tricyclopropyl carboxylate, glycerol tricyclohexyl carboxylate Glycerin aryl esters such as glycerin tribenzoate and glycerin 4-methylbenzoate, diglycerin tetraacetylate, diglycerin tetrapropionate, diglycerin acetate tricaprylate, diglycerin alkyl esters such as diglycerin tetralaurate, di Diglycerides such as glycerin tetracyclobutylcarboxylate and diglycerin tetracyclopentylcarboxylate Emissions cycloalkyl esters, diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like. These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a 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, and the partial structure of the glycerin ester and diglycerin ester may be part of the polymer or regularly pendant, and may be an antioxidant or an acid scavenger. Or may be introduced into a part of the molecular structure of an additive such as an ultraviolet absorber.

  Polyhydric alcohol ester plasticizer: Specific examples include polyhydric alcohol ester plasticizers described in paragraphs 30 to 33 of JP-A-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.

  Dicarboxylic acid ester plasticizers: Specifically, alkyldocarboxylic acid alkyl ester plasticizers such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), dicyclopentyl succinate, Alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclohexyl adipate, diphenyl succinate, alkyl dicarboxylic acid aryl ester plasticizers such as di4-methylphenyl glutarate, dihexyl-1,4-cyclohexanedicarboxylate, Cycloalkyldicarboxylic acid alkyl ester plasticizers such as didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutanedicarboxylate, dicyclopropyl-1,2 Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as cyclohexyl dicarboxylate, aryl cycloalkyldicarboxylates such as diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexanedicarboxylate Ester plasticizers, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate, and aryl dicarboxylic acid cycloalkyls such as dicyclopropyl phthalate and dicyclohexyl phthalate Examples include ester plasticizers and aryl dicarboxylic acid aryl ester plasticizers such as diphenyl phthalate and di4-methylphenyl phthalate. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. 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.

  Polycarboxylic acid ester plasticizers: Specifically, alkyl polycarboxylic acid alkyl ester plastics such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate Agents, alkyl polyvalent carboxylic acid cycloalkyl ester type plasticizers such as tricyclohexyl tricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy-1,2 Alkyl polycarboxylic acid aryl ester plasticizers such as 1,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2,3,4 -Cyclobutane tetracarboxylate, tetrabutyl-1,2, 1,4-cyclopentanetetracarboxylate and other cycloalkyl polycarboxylic acid alkyl ester plasticizers, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl-1,3,5-cyclohexyl Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2,3,4,5,6 -Cycloalkyl polycarboxylic acid aryl ester plasticizers such as cyclohexyl hexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4,5-tetracarboxylate, etc. Aryl polycarboxylic acid Lester ester plasticizer, aryl polycarboxylic acid cycloalkylester plasticizer tri, such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polycarboxylic acid aryl ester-based plasticizers such as phenylbenzene-1,3,5-tetracartoxylate and hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Can be mentioned. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. 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.

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

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

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

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

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

  The hindered phenolic antioxidant compound is a known compound, and is described in, for example, columns 12 to 14 of U.S. Pat. No. 4,839,405, and includes a 2,6-dialkylphenol derivative compound. It is.

  Specific examples of the hindered phenol compound include n-octadecyl = 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl = 3- (3,5-di-t- Butyl-4-hydroxyphenyl) -acetate, n-octadecyl = 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl = 3,5-di-t-butyl-4-hydroxyphenylbenzoate, n -Dodecyl = 3,5-di-tert-butyl-4-hydroxyphenylbenzoate, neo-dodecyl = 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, dodecyl = β (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate, ethyl = α- (4-hydroxy-3,5-di-t-butylphenyl) isobuty Rate, octadecyl = α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl = α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (n-octylthio) ethyl = 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (n-octylthio) ethyl = 3,5-di-t-butyl-4-hydroxy-phenylacetate 2- (n-octadecylthio) ethyl = 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl = 3,5-di-t-butyl-4-hydroxy -Benzoate, 2- (2-hydroxyethylthio) ethyl = 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol = bi Su- (3,5-di-tert-butyl-4-hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl = 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate , Stearamide-N, N-bis- [ethylene = 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino-N, N-bis- [ethylene = 3- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl = 3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-stearoyl) Oxyethylthio) ethyl = 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,2-propylene glycol = bis- 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], ethylene glycol = bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], neopentyl Glycol = bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol = bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin -Ln-octadecanoate-2,3-bis- (3,5-di-t-butyl-4-hydroxyphenylacetate), pentaerythritol-tetrakis- [3- (3 ', 5'-di -T-butyl-4'-hydroxyphenyl) propionate], 1,1,1-trimethylolethane-tris- [3- (3,5-di-t-butyl) -4-hydroxyphenyl) propionate], sorbitol hexa- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl = 7- (3-methyl-5-t- Butyl-4-hydroxyphenyl) propionate, 2-stearoyloxyethyl = 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ′, 5'-di-tert-butyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis (3,5-di-tert-butyl-4-hydroxyhydrocinnamate). Hindered phenolic antioxidants of the above type are commercially available from Ciba Specialty Chemicals under the trade names “Irganox 1076” and “Irganox 1010”, for example.

  Specific examples of other antioxidants include phosphorus antioxidants such as trisnonylphenyl phosphite, triphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, and dilauryl-3. , 3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythrityltetrakis (3-laurylthiopropionate), etc. System antioxidant, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5- Di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate 3,4-dihydro-2H-1-benzopyran compound, 3,3′-spirodichroman compound, 1,1-spiroindane compound, morpholine, thiomorpholine, thiomorpholine oxide, described in JP-B-08-27508 Examples include thiomorpholine dioxide, compounds having a piperazine skeleton in the partial structure, oxygen scavengers such as dialkoxybenzene compounds described in JP-A-3-174150, and the like. These antioxidant partial structures may be part of the polymer or regularly pendant to the polymer.

(Acid scavenger)
Since cellulose ester is accelerated by acid at high temperatures, the optical film of the present invention preferably contains an acid scavenger.

  Any acid scavenger useful in the present invention can be used without limitation as long as it is a compound that reacts with an acid to inactivate the acid, and is described in U.S. Pat. No. 4,137,201. Compounds having an epoxy group are preferred. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of various polyglycol diglycidyl ethers, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ether of glycerol, metal epoxy compounds (such as those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, diphenols of bisphenol A Glycidyl ether (i.e., 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 4 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (e.g. butyl Epoxy stearate And epoxidized vegetable oils and other unsaturated natural oils (sometimes these are epoxidized natural glycerides, which can be represented and exemplified by compositions of various epoxidized long chain fatty acid triglycerides and the like (eg, epoxidized soybean oil and the like) Or unsaturated fatty acids, which generally contain 12 to 22 carbon atoms). Moreover, EPON 815C can also be preferably used as a commercially available epoxy group-containing epoxide resin compound.

  Furthermore, examples of acid scavengers that can be used other than the above include oxetane compounds, oxazoline compounds, organic earth salts of alkaline earth metals and acetylacetonate complexes, and paragraphs 68 to 105 of JP-A-5-194788. Is included.

  In addition, although an acid scavenger may be called an acid scavenger, an acid capture agent, an acid catcher, etc., in this invention, it can use without a difference by these names.

(Light stabilizer)
In the present invention, as a stabilizer for external light exposed as a polarizer protective film after production or light from the backlight of a liquid crystal display, a hindered amine light stabilizer (HALS) compound can be mentioned, which is a known compound, For example, as described in US Pat. No. 4,619,956, columns 5-11 and US Pat. No. 4,839,405, columns 3-5, 2,2,6 , 6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds.

  Specific examples of hindered amine light stabilizer compounds include 4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-allyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-benzyl. -4-hydroxy-2,2,6,6-tetramethylpiperidine, 1- (4-t-butyl-2-butenyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-stearoyl Oxy-2,2,6,6-tetramethylpiperidine, 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6 6-pentamethylpiperidine, 1,2,2,6,6-pentamethylpiperidin-4-yl-β (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, -Benzyl-2,2,6,6-tetramethyl-4-piperidinyl maleate, (di-2,2,6,6-tetramethylpiperidin-4-yl) -adipate, (di- 2,2,6,6-tetramethylpiperidin-4-yl) -sebacate, (di-1,2,3,6-tetramethyl-2,6-diethyl-piperidin-4-yl) -sebacate, (di -1-allyl-2,2,6,6-tetramethyl-piperidin-4-yl) -phthalate, 1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl-acetate, trimellitic acid- Tri- (2,2,6,6-tetramethylpiperidin-4-yl) ester, 1-acryloyl-4-benzyloxy-2,2,6,6-tetramethylpiperidine, dibutyl-malonic acid-di -(1,2,2,6,6-pentamethyl-piperidin-4-yl) -ester, dibenzyl-malonic acid-di- (1,2,3,6-tetramethyl-2,6-diethyl-piperidine- 4-yl) -ester, dimethyl-bis- (2,2,6,6-tetramethylpiperidine-4-oxy) -silane, tris- (1-propyl-2,2,6,6-tetramethylpiperidine- 4-yl) -phosphite, tris- (1-propyl-2,2,6,6-tetramethylpiperidin-4-yl) -phosphate, N, N′-bis- (2,2,6,6- Tetramethylpiperidin-4-yl) -hexamethylene-1,6-diamine, N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -hexamethylene-1,6- Diacetamide, 1-acetyl -4- (N-cyclohexylacetamide) -2,2,6,6-tetramethyl-piperidine, 4-benzylamino-2,2,6,6-tetramethylpiperidine, N, N'-bis- (2, 2,6,6-tetramethylpiperidin-4-yl) -N, N'-dibutyl-adipamide, N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -N , N'-dicyclohexyl- (2-hydroxypropylene), N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -p-xylylene-diamine, 4- (bis-2 -Hydroxyethyl) -amino-1,2,2,6,6-pentamethylpiperidine, 4-methacrylamide-1,2,2,6,6-pentamethylpiperidine, α-cyano-β-methyl-β- [N- (2,2 6,6-tetramethyl-piperidin-4-yl)] - amino - and methyl acrylate and the like.

  At least one or more stabilizers in the film-forming material used in the present invention can be selected. The amount to be added is 0.001% by mass or more based on the mass of the cellulose ester. The content is preferably not more than mass%, more preferably not less than 0.005 mass% and not more than 3 mass%, and still more preferably not less than 0.01 mass% and not more than 0.8 mass%.

(UV absorber)
When the optical film of the present invention is used as a polarizer protective film used on the outer side with respect to the liquid crystal cell, it is preferable to further contain an ultraviolet absorber. The ultraviolet absorber is a material having an effect of preventing the material constituting the film from being decomposed by ultraviolet rays in an environment used after production. Cellulose ester itself is a material that is relatively resistant to ultraviolet rays, but other additives may be compounds that are weak against ultraviolet rays, and polarizers and liquid crystal cells are also vulnerable to ultraviolet rays. In addition, it is preferable that at least the polarizer protective film on the side exposed to external light and the polarizer protective film on the side on which the backlight of the liquid crystal display is incident contain an ultraviolet absorber.

  As such an ultraviolet absorber, from the viewpoint of preventing deterioration of a polarizer and a display device with respect to ultraviolet rays, the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less. Those that absorb less are preferred. Examples include oxybenzophenone compounds, benzotriazole compounds, triazine compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Triazole compounds are preferable, and benzotriazole compounds are particularly preferable. Moreover, you may use the ultraviolet absorber of Unexamined-Japanese-Patent No. 10-182621, Unexamined-Japanese-Patent No. 8-337574, and the polymeric ultraviolet absorber of Unexamined-Japanese-Patent No. 6-148430.

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

  As commercially available products, TINUVIN 109, TINUVIN 171, TINUVIN 234, and TINUVIN 360 (all manufactured by Ciba Specialty Chemicals) can also be used.

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

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

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

  Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazane, siloxane and the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average particle size of the secondary particles of the fine particles is in the range of 0.05 to 1.0 μm. The average particle size of secondary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used in the cellulose ester film in order to generate irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film. The content of the fine particles in the cellulose ester is preferably 0.005 to 0.3% by mass with respect to the cellulose ester.

  Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably Aerosil 200V, R972. , R972V, R974, R202, R812. Two or more kinds of these fine particles may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, fine particles having different average particle sizes and materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

  The presence of fine particles in the film used as the matting agent can be used for another purpose to improve the strength of the film. The presence of the fine particles in the film can also improve the orientation of the cellulose ester itself constituting the optical film of the present invention.

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

(Other additives)
Examples of other additives include fillers, inorganic compounds such as silica and silicate, dyes, pigments, phosphors, refractive index adjusters, gas permeation inhibitors, and the like. Moreover, the additive which is not classified into this can be used if it has the said function.

  Then, as a method of incorporating these additives into the cellulose ester, each material is mixed in a solid or liquid state, heated and melted and kneaded to form a uniform melt, and then cast to form an optical film. Even in this method, after dissolving all the materials in advance using a solvent or the like to obtain a uniform solution, the solvent is removed to form a mixture of the additive and the cellulose ester, and this is heated and melted. It may be cast to form an optical film.

(Film formation)
Examples of the optical film of the present invention include U.S. Pat. Nos. 2,492,978, 2,739,070, 2,739,069, 2,492,977, and 2,336. 310, No. 2,367,603, No. 2,607,704, British Patent Nos. 64,071, 735,892, No. 45-9074, No. 49-4554, The film can be formed by referring to the methods described in JP 49-5614, JP 60-27562, JP 61-39890, and 62-4208.

  For example, the cellulose ester and additive mixture of the present invention can be hot-air dried or vacuum dried, melt extruded, extruded into a film form from a T-die, and taken up by a roll adjusted to 50 to 150 ° C. . At this time, nipping with two rolls is preferable from the viewpoint of improving flatness.

  For melt extrusion, a single screw extruder, a twin screw extruder, or a single screw extruder may be connected downstream of the twin screw extruder, but a twin screw extruder is used from the viewpoint of uniformly dispersing the aforementioned additives. It is preferable. 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 during the melt extrusion of the present invention is preferably in the range of Tg or more and Tg + 100 ° C. or less. Furthermore, it is preferable that it is the range of Tg + 10 degreeC or more and Tg + 90 degreeC or less.

  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 from the cooling roll described above is brought into the glass transition temperature (Tg) -50 ° C. to Tg + 100 ° C. of the cellulose ester via a plurality of roll groups and / or a heating device such as an infrared heater. It is preferable to heat and stretch in one or more stages. Next, it is preferable that the cellulose ester film stretched in the longitudinal direction obtained as described above is transversely stretched within a temperature range of Tg-50 ° C to Tg + 100 ° C and then heat-set.

  In the case of transverse stretching, it is preferable to perform transverse stretching while sequentially raising the temperature difference in the range of 1 to 50 ° C. in a stretching region divided into two or more, because the distribution of physical properties in the width direction can be reduced. Further, after the transverse stretching, it is preferable that the film is kept at a temperature of Tg-40 ° C. or higher at a temperature equal to or lower than the final transverse stretching temperature for 0.01 to 5 minutes because the physical property distribution in the width direction can be further reduced.

  In the heat setting, heat setting is usually performed for 0.5 to 300 seconds at a temperature higher than the final transverse stretching temperature and within a temperature range of Tg-20 ° C or lower. At this time, it is preferable to heat-fix while sequentially raising the temperature difference in the range of 1 to 100 ° C. in the region divided into two or more.

  The heat-set film is usually cooled to Tg or less, and clip holding portions at both ends of the film are cut and wound. At this time, it is preferable to perform a relaxation treatment of 0.1 to 10% in the lateral direction and / or the longitudinal direction within a temperature range of not more than the final heat setting temperature and not less than Tg. In addition, it is preferable that the cooling is gradually performed from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to carry out these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film. The cooling rate is a value obtained by (T1−Tg) / t, where T1 is the final heat setting temperature and t is the time until the film reaches Tg from the final heat setting temperature.

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

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

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

  A cellulose ester film having a laminated structure can also be produced by co-extruding compositions containing cellulose resins having different additive concentrations such as the above-mentioned plasticizer, ultraviolet absorber and matting agent. For example, a cellulose ester film having a structure of skin layer / core layer / skin layer can be produced. For example, the matting agent can be contained in the skin layer in a large amount or only in the skin layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. In addition, the type of plasticizer and ultraviolet absorber can be changed between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. The Tg of the skin layer and the core layer may be different, and the Tg of the core layer is preferably lower than the Tg of the skin layer. Also, the viscosity of the melt containing the cellulose ester during 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 used.

  The optical film of the present invention can be used for a polarizing plate protective film. When using as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method. The obtained optical film is alkali-treated, and a polarizer protective film is bonded to both sides of the polarizer using a completely saponified polyvinyl alcohol aqueous solution on both sides of the polarizer prepared by immersing and stretching the polyvinyl alcohol film in an iodine solution. There is a method, and an optical film which is a polarizing plate protective film of the present invention is preferred at least on one side from the viewpoint that it can be directly bonded to a polarizer.

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

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

(Stretching operation, refractive index control)
The optical film of the present invention can be controlled in refractive index by a stretching operation. As the stretching operation, the refractive index is controlled within a preferable range by stretching 1.0 to 2.0 times in one direction of the cellulose ester and 1.01 to 2.5 times in the direction perpendicular to the film plane. Can do.

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

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

  Furthermore, the film thickness fluctuation | variation of the film obtained can be reduced by extending | stretching in the biaxial direction orthogonal to each other. If the 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). It is necessary.

  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.

  The display optical film of the present invention preferably has a surface roughness Ra of 1 μm or less. When Ra is larger than 1 μm, when the above-described various functional layers are provided, the surface may become uneven or remain as convex defects, and smoothness and gloss may be impaired. In order to reduce Ra to 1 μm or less, the surface of the take-up roll or drawing roll immediately after melt extrusion is made into a mirror surface, the mirror roll is nipped immediately after taking up with the roll, and the temperature and magnification of vertical and / or horizontal drawing This is achieved by appropriately selecting the stretching speed. It is also effective to reduce Ra by sharpening the lip edge of the melt-extrusion die or mirroring the surface in contact with the molten resin inside the die.

  When the optical film for display 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-mentioned region, it is not preferable because it becomes difficult to develop retardation, the moisture permeability of the film becomes high, and the ability to protect the polarizer from humidity decreases.

  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.

(Liquid crystal display device)
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the optical film of the present invention is applied can provide excellent display properties regardless of the location. . In particular, since a clear hard coat layer, an antiglare layer, an antireflection layer, and the like are provided on the polarizing plate protective film on the display side outermost surface of the liquid crystal display device, it is particularly preferable to use the polarizing plate protective film for this portion. 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.

(Bright spot foreign matter)
With the bright spot foreign material of the present invention, two polarizing plates are placed in an orthogonal state (crossed nicols), a cellulose ester film (for example, cellulose acetate propionate) is placed between them, and light is applied from one polarizer side, This is a point that appears white when observed with a microscope from the other side of the polarizer, and if this is present, it becomes a defect of the display, and a smaller number is suitable for a high-definition display. This is considered to be caused by light leaking because the refractive index is different in the foreign part of the cellulose ester, and one of the causes is cellulose left unacetylated during the acetylation process or sufficiently heated and melted It is presumed that the raw polymer particles that were not present are entangled.

  The polarizing plate used for measuring bright spot foreign matter is preferably made of glass. This is because, when a polarizing plate made of a cellulose ester film is used, the polarizing plate itself contains bright spot foreign matter, which makes it difficult to distinguish it from the bright spot foreign matter in the sample. In addition, a polarizing plate may be disposed at a distance from the sample. If the polarizing plate is arranged at a distance from the sample, the focused position is shifted by the microscope, so that the bright spot foreign matter in the sample can be specified.

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

  The following cellulose ester was used as a raw material polymer.

<Cellulose ester>
C-1: cellulose acetate propionate (acetyl substitution degree 1.9, propionyl group substitution degree 0.8, molecular weight Mn = 70000, molecular weight Mw = 220,000, Mw / Mn = 3)
C-2: Cellulose acetate propionate (CAP482-20 (manufactured by Eastman Chemical Co.))
C-3: Cellulose acetate butyrate (CAB171-15 (manufactured by Eastman Chemical Co.))
<Plasticizer>
P-1: Trimethylolpropane tribenzoate <Antioxidant>
A-1: IRGANOX-1010 (Ciba Specialty Chemicals)
Example 1
Film formation of the present invention-1 to 3 After the cellulose ester C-1 is pulverized by changing the screen mesh with a Horai pulverizer, it is passed through a classification sieve so that the average particle diameter is 0.2 mm. It was adjusted. Plasticizer P-1: 8% and antioxidant A-1: 0.5% were added to this, and it mixed for 30 minutes with the V-type mixer.

  The obtained mixture was granulated with Fuji Powder Co., Ltd. disk pelleter F-5. The obtained granulated body had an average particle diameter of 2.0 mm and a cylindrical shape with a particle size distribution of 6% by mass obtained by adding particles less than 1 mm and greater than 10 mm. The pellets were dried by a dehumidifying hot air dryer (Matsui Seisakusho DMZ2) at a hot air temperature of 130 ° C and a dew point of -36 ° C. Then, it supplied to the technobel Co., Ltd. twin-screw extruder, melt-extruded, and shape | molded into the film. In addition, the schematic diagram of a twin-screw extruder is shown in FIG.

  The set temperature of the extruder was 220, 230, 230 ° C. from the raw material hopper 1 toward the barrel tip, and the T die was 240 ° C. The T-die was a coat hanger type with a gap of 300 μm. The gap can be adjusted by push-pull bolts according to the thickness of the film formed.

  From an opening of the additive hopper 2 provided in the middle part of the extruder, silica particles (particle size: 2 μm) were added as a slip agent by a continuous feeder so as to be 0.05% of the extrusion amount. Similarly, a UV absorber (TINUVIN 360) was added so that the amount of extrusion was 0.5% from the opening. The melt-extruded film was dropped between two chrome-plated mirror rolls whose temperature was adjusted to 120 ° C., passed between the three rolls, slit the edge, and wound around a winder.

  The extrusion amount and the rotation speed of the take-up roll were adjusted so that the wound film had a thickness of 80 μm.

  The film obtained as described above is referred to as the present invention-1, and the films formed with the average particle diameter of the granulated particles of the cellulosic material as shown in Table 1 as 5 mm and 8 mm, respectively as the present invention-2, It was set to 3.

(Example 2) Film formation of the present invention-4 A film was produced in the same manner as in Example 1 except that the cellulose ester C-1 was changed to C-2.

(Example 3) Film formation of the present invention-5 A film was produced in the same manner as in Example 1 except that the cellulose ester C-1 was changed to C-3.

Comparative Example 1 Film Formation of Comparative Examples 1 and 3 Film formation was performed in the same manner as in Example 1 except that the particle size and particle size distribution of the raw material cellulose ester were adjusted to the values shown in Table 1 when granulating. did.

(Comparative Example 2) Film formation of Comparative Example 2 A film was formed in the same manner as in Example 1 except that the polymer was C-2 and the particle size was adjusted to the values shown in Table 1 when granulating.

  The obtained film samples were evaluated according to the following criteria. The results are shown in Table 1.

[Evaluation]
Average particle size: Shimadzu Corporation The average particle size (μm) was measured using a particle size distribution analyzer SALD-2000A.

  Particle size distribution: The total ratio (%) of particles less than 1 mm and greater than 10 mm when the average particle size was measured was calculated.

  Bulk specific gravity: Tsutsui Rika Instruments Co., Ltd. B. The loose bulk density was measured using a D powder characteristic measuring instrument.

Bright spot foreign matter: Two polarizing plates are arranged in an orthogonal state (crossed Nicols) to block transmitted light, and a prepared film sample is placed between the two polarizing plates. The polarizing plate used was a glass protective plate. Light was irradiated from one side, and the number of bright spots having a diameter of 0.01 mm or more per 1 cm ² was counted with an optical microscope (50 times) from the opposite side.

A: Number of bright spots from 0 to 30 ○: 31 to 50 Δ: 51 to 80 ×: 81 to 100 ××: 101 or more Molecular weight retention: Weight of raw polymer before being supplied to melt extrusion The average molecular weight Mw0 and the weight average molecular weight Mw1 of the polymer after melt extrusion were measured by gel permeation chromatography (GPC), and Mw1 / Mw0 × 100 (%) was defined as the molecular weight retention rate.

  Transmittance: Using a spectrophotometer U-3400 (Hitachi, Ltd.), the average transmittance of each sample in the wavelength region of 380 to 700 nm was calculated.

  Haze: Measured according to ASTM-D1003-52 using T-2600DA manufactured by Tokyo Denshoku Industries Co., Ltd.

  Surface roughness: The surface roughness is a centerline average roughness (Ra) defined by JIS B061-1982, and was measured using Surfcoder SE-30H (manufactured by Kosaka Laboratory).

  Film thickness: Ten points were measured using a micro gauge, and the film thickness was determined from the average value.

  From the above results, the shape of the raw material polymer formed by granulating at a low temperature of Tg or less using a powdered cellulose ester, granulated particles having a particle size of 1 to 10 mm and a bulk specific gravity of 0.1 to 1.0. It can be seen that the optical film formed by the melt casting method has excellent characteristics.

Example 2
(Preparation of polarizing plate)
A 120 μm-thick polyvinyl alcohol film was immersed in an aqueous solution containing 1 part by mass of iodine, 2 parts by mass of potassium iodide, and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to produce a polarizer. The film of Example or Comparative Example was alkali-treated with a 2.5 M / L sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, and further washed with water and dried to alkali-treat the surface.

  The polarizing plate on which the protective film was formed was prepared by bonding the alkali-treated surface of the optical film of Example or Comparative Example to both surfaces of the polarizer from both surfaces using a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive.

(Characteristic evaluation as a liquid crystal display device)
The both-sided polarizing plates of the 15-inch display VL-150SD manufactured by Fujitsu were peeled off, and the prepared polarizing plates were cut according to the size of the liquid crystal cell and bonded to the glass surface.

  The two prepared polarizing plates were bonded so as to be orthogonal to each other so that the polarizing axes of the polarizing plates were not changed, and liquid crystal display devices were respectively prepared.

  The liquid crystal display device using the polarizing plate of the present invention had high contrast and showed excellent display properties. Thereby, it was confirmed that it is excellent as a polarizing plate for image display apparatuses, such as a liquid crystal display.

The schematic diagram of a twin-screw extruder is shown.

Explanation of symbols

1 Raw material hopper 2 Additive hopper

Claims (3)

An optical film for display comprising a cellulose ester polymer,
The shape of the raw material polymer is a particle having a particle size of 1 to 10 mm and a bulk specific gravity of 0.1 to 1.0. A method for producing an optical film for display, wherein the film is formed by granulation and melt-extrusion film formation using the raw material polymer. In the melt extrusion film formation, the raw material polymer is melted in a temperature range from Tg to Tg + 100 ° C. by using a single-screw or twin-screw extruder and extruded from a T die having a flat slit gap. The manufacturing method of the optical film for displays of Claim 1 characterized by the above-mentioned. The method for producing an optical film for display according to claim 1 or 2, wherein the raw material polymer is at least one cellulose ester selected from cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate.

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