JP2007326359A - Method for manufacturing cellulose acylate film, cellulose acylate film, polarizing plate, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose acylate film excellent in flatness and being inhibited in streaky irregularity by a melt film forming method being free from a halogen solvent which impose a big load on the environment, and further, an optical film excellent in evenness and a liquid crystal display excellent in image quality. <P>SOLUTION: The method for manufacturing the cellulose acylate film is characterized in that the cellulose acylate film contains at least one compound represented by general formula (1): A-(X-B)<SB>n</SB>, and that the cellulose acylate film extruded from a casting die at the time of melt casting film formation is pressed between a touch roll and a cooling roll. The cellulose acylate film, a polarizing plate and the liquid crystal display are also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a cellulose acylate film, a cellulose acylate film, a polarizing plate using the cellulose acylate film, and a liquid crystal display device.

  The cellulose acylate film protects a support for a photographic negative film and an optical film used for a liquid crystal display, for example, a polarizer because of its high transparency, low birefringence, and easy adhesion to a polarizer. It has been used for films, polarizing plates and the like.

  Due to the thinness and lightness of the liquid crystal display, the production volume has increased greatly in recent years, and the demand for liquid crystal displays has increased. In addition, TVs using liquid crystal displays are thin and light, and large-scale TVs that have not been achieved with TVs using Brown 菅 are now being produced. Demand for optical films is increasing.

  These cellulose acylate films have heretofore been produced exclusively by the solution casting method. The solution casting method is a film forming method in which a solution obtained by dissolving cellulose acylate in a solvent is cast to obtain a film shape, and then the solvent is evaporated and dried to obtain a film. Since a film formed by the solution casting method has high flatness, a high-quality liquid crystal display without unevenness can be obtained using this film.

  However, the solution casting method requires a large amount of an organic solvent and has a large environmental load. The cellulose acylate film is formed using a halogen-based solvent with a large environmental load because of its dissolution characteristics, and therefore, the reduction of the amount of solvent used is particularly required. The cellulose acylate film is formed by solution casting film formation. It has become difficult to increase production.

  In recent years, attempts have been made to melt-form cellulose acylate for silver salt photography (for example, see Patent Document 1) or polarizer protective film (for example, see Patent Document 2). The rate is a polymer that has a very high viscosity when melted, and has a high glass transition temperature. Therefore, the cellulose acylate can be melted and extruded from a die and leveled even when cast on a cooling drum or cooling belt. However, it was found that the obtained film had a problem that the flatness of the obtained film was lower than that of the solution cast film because it solidified in a short time after extrusion.

  It is known that the addition of a plasticizer is effective for reducing the melt viscosity and glass transition temperature of organic polymers such as cellulose acylate.

  In Patent Documents 1 and 2, phosphoric acid plasticizers such as triphenyl phosphate and phenylenebisdiphenyl phosphate are used. However, as a result of investigation by the inventors of the present invention, these phosphoric acid plasticizers decompose phosphoric acid ester by moisture absorption or heating, generate phosphoric acid, and the generated phosphoric acid degrades cellulose acylate. It has been found that the film has a problem of coloring the film.

  As plasticizers used for cellulose acylate other than phosphate esters, ethylene glycol plasticizers or polyhydric alcohol esters which are esters of trivalent or higher alcohols and carboxylic acids are used in solution casting. Are known. For example, glycerin-carboxylic acid ester (for example, refer to Patent Document 3), pentaerythritol or dipentaerythritol ester (for example, refer to Patent Document 4) is disclosed. A plasticizer comprising a polyhydric alcohol-carboxylic acid is preferable for film formation of cellulose acylate because it has high chemical stability and does not generate strong acid that causes degradation of cellulose acylate even when hydrolyzed. It is a plasticizer. However, these plasticizers are insufficient in viscosity reduction effect and moisture permeability reduction effect, or cellulose acylate films with excellent bleed-out issues such as precipitation and volatilization of the plasticizer outside the film, and durability and flatness. It has been found that there is a problem that cannot be obtained.

  Further, Patent Documents 1 to 4 do not describe a more advantageous production method for melt film formation, and are essentially different from the technique of the present invention aimed at melt film formation.

  A method for producing an optical film by using a melt casting method has been proposed (see, for example, Patent Documents 5 and 6). Patent Document 5 proposes a method of cooling a molten resin by sandwiching it on an arc with a cooling roll and an endless belt maintained at a uniform temperature in the width direction. Patent Document 6 proposes a method of cooling by sandwiching a molten resin between two cooling drums. However, since the melt obtained by heating and melting the cellulose resin has a high viscosity, the film produced by the melt casting film formation method is inferior to the film produced by the solution casting film formation method. In particular, there is a drawback that die line and thickness unevenness are likely to occur.

In addition, as the liquid crystal display device has a large screen, it is desired that the width of the original film is wide and the winding length is long. For this reason, the original film becomes wider and the load on the original film tends to increase. If these are stored for a long period of time, a failure called a horse back failure is likely to occur. The horse's back failure is a failure in which the original film is deformed into a U shape like the horse's back, and a belt-like convex part is formed at a pitch of about 2 to 3 cm near the center, and the film remains deformed. This is a problem because the surface becomes distorted when processed into a polarizing plate. Moreover, the cellulose acylate film installed on the outermost surface of the liquid crystal display is subjected to clear hard processing, anti-glare processing, and anti-reflection processing. When these processes are performed, if the surface of the cellulose acylate film is deformed, coating unevenness and vapor deposition unevenness are caused, which causes a significant deterioration in the product yield. Until now, horse back failure has been reduced by reducing the coefficient of dynamic friction between the bases and adjusting the height of the knurling (embossing) on both sides. It is also known that a horse's back failure occurs due to the deflection of the core due to the film load, and it is disclosed that the occurrence of a horse's back failure is reduced by adjusting the surface roughness of the core of the optical film substrate ( For example, see Patent Document 7). However, there is a demand for a wider cellulose acylate film corresponding to recent liquid crystal televisions, and these techniques alone are insufficient and further means have been demanded.
Japanese National Patent Publication No. 6-501040 JP 2000-352620 A Japanese Patent Laid-Open No. 11-246704 Japanese Patent Laid-Open No. 11-124445 Japanese Patent Laid-Open No. 10-10321 JP 2002-221312 A JP 2002-3083 A

  Accordingly, the object of the present invention is to achieve a flat surface by a manufacturing method using an additive and an elastic touch roll that has sufficient viscosity reducing effect and moisture permeability reducing effect and does not cause bleeding or volatilization out of the film. The present invention is to provide an optical film having high uniformity and suppressed streak-like unevenness, and to provide a liquid crystal display having high image quality using the optical film. Further, the present invention provides an optical film excellent in productivity that does not cause deformation failure of the original film of the film such as a horse back failure or a convex failure even if stored for a long period of time. The effect is exhibited in the optical film. Furthermore, it is to provide a cellulose acylate film by a melt film forming method that does not use a halogen-based solvent having a large environmental load.

  About the said subject, when the inventors of this invention earnestly examined, by containing the compound which has a specific aromatic group structure, and using together with the cooling method using the elastic touch roll, a viscosity reduction effect, and The effect of reducing moisture permeability is sufficient, and the additive bleed-out does not occur. Even in the manufacturing method using the melt casting method, high flatness and streak-like unevenness are suppressed. The present inventors have found that a cellulose acylate film can be obtained that does not cause deformation failure of the original film, such as a film failure and a convex failure.

  1. A method for producing a cellulose acylate film formed by a melt casting film forming method, wherein the cellulose acylate film contains at least one compound represented by the following general formula (1) and is melt cast A method for producing a cellulose acylate film, wherein the cellulose acylate film extruded from a casting die at the time of film formation is produced by sandwiching the cellulose acylate film with a touch roll whose surface is elastically deformable and a cooling roll.

General formula (1)
A- (X-B) _n
(In the formula, A represents an alkyl group, X represents a divalent linking group selected from the group consisting of —NHCO—, —NHSO ₂ —, —O—, or —SO ₂ —, and B represents an aromatic group. And n represents 3 or 4, and a plurality of X-Bs may be the same or different.)
2. 2. The cellulose reed according to 1 above, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2), general formula (3) or general formula (4): A method for producing a rate film.

(In the formula, X represents a divalent linking group selected from the group consisting of —NHCO—, —NHSO ₂ —, —O—, or —SO ₂ —, and R ^{1 to} R ²⁰ each independently represents a hydrogen atom. Represents a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group, which further has a substituent. R ²¹ represents an alkyl group.)
3. 3. The method for producing a cellulose acylate film as described in 1 or 2 above, wherein the cellulose acylate used in the method for producing a cellulose acylate film has an acyl group total carbon number of 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.

  4). A cellulose acylate film produced by the method for producing a cellulose acylate film according to any one of 1 to 3 above.

  5. 5. The cellulose acylate film as described in 4 above, wherein the cellulose acylate film contains at least one selected from a hindered phenol-based antioxidant, a phosphorus-based antioxidant, and a carbon radical scavenger.

  6). 6. A polarizing plate using the cellulose acylate film as described in 4 or 5 above as a protective film for a polarizing plate.

  7). 7. A liquid crystal display device using the polarizing plate described in 6 above.

  According to the present invention, the flatness is high by the manufacturing method using the additive and the elastic touch roll which has sufficient viscosity reducing effect and moisture permeability reducing effect and does not cause bleed out such as precipitation or volatilization outside the film. It was possible to provide a highly uniform optical film in which streak-like unevenness was suppressed and to provide a liquid crystal display with high image quality. In addition, we provide optical films with excellent productivity that do not cause deformation defects in the original film, such as horse back failure or convex failure, even after long-term storage. It could be provided by a melt film-forming method that does not use a solvent.

  The present invention will be described in more detail. The optical film targeted by the present invention is a functional film used in various displays such as liquid crystal displays, plasma displays and organic EL displays, particularly liquid crystal displays, and includes a polarizing plate protective film, a retardation film, an antireflection film, It includes an optical compensation film such as a brightness enhancement film and a viewing angle expansion.

  The present invention relates to a cellulose acylate film having sufficient planarity and excellent optical properties and dimensional stability even for a melt-formed cellulose resin, and a method for producing the same.

  By using the cellulose acylate film according to the present invention, it is possible to obtain a high-quality optical film such as a polarizing plate protective film, an antireflection film, a retardation film, and a liquid crystal display device having a high display quality. be able to.

  As a result of diligent research, the inventors of the present invention have excellent optical characteristics and dimensional stability, as well as flatness in a thermal melting method, that is, a method of forming a film by a melt casting method that does not use a halogen-based solvent with a large environmental load. In order to obtain a high cellulose acylate film, the planarity of the obtained cellulose acylate film is dramatically improved by selecting a specific compound as an additive contained in the cellulose ester during casting. I found out.

  That is, it has been found that in the melt casting method in which the melted cellulose ester is cast on a cooling drum or a cooling belt, the use of the additive according to the present invention makes it easy to level and obtain a film with high flatness.

  The cellulose acylate film of the present invention is a cellulose acylate film characterized by containing the compound represented by the general formula (1). As content, 1-25 mass% is preferable. When the content is less than 1% by mass, the effect of improving the flatness is not recognized, and when the content is more than 25% by mass, bleeding out easily occurs and the temporal stability of the film decreases, which is not preferable. More preferred is a cellulose acylate film containing 3 to 20% by mass, and further preferred is a cellulose acylate film containing 5 to 15% by mass.

  Here, the melting temperature of the film constituting material means a temperature at which the material is heated and fluidity is developed. In order to melt and flow the cellulose ester, it is necessary to heat at least a temperature higher than the glass transition temperature. Above the glass transition temperature, the elastic modulus or viscosity decreases due to heat absorption, and fluidity is exhibited. However, in cellulose esters, the molecular weight of the cellulose ester may decrease due to thermal decomposition at the same time as melting at high temperatures, which may adversely affect the mechanical properties of the resulting film. Therefore, it is necessary to melt the cellulose ester at the lowest possible temperature. is there. In order to lower the melting temperature of the film constituting material, it can be achieved by adding a compound having a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester. The compound represented by the general formula (1) used in the present invention lowers the melting temperature of the cellulose ester, has low volatility even after the melt film-forming process and production, and has good process suitability and is obtained. It is excellent in that the optical properties, dimensional stability, and flatness of the cellulose acylate film are good.

In General Formula (1), A represents an alkyl group, X represents a divalent linking group selected from the group consisting of —NHCO—, —NHSO ₂ —, —O—, or —SO ₂ —, and B represents Represents an aromatic group, n represents 3 or 4, and a plurality of X-Bs may be the same or different. And the compound represented by General formula (1) has a preferable compound represented by the said General formula (2), General formula (3), or General formula (4).

In General Formula (2), General Formula (3), or General Formula (4), X has the same meaning as X in General Formula (1), and is —NHCO—, —NHSO ₂ —, —O—, or — Represents a divalent linking group selected from the group consisting of SO ₂ —.

In General Formula (2), General Formula (3), or General Formula (4), R ^{1 to} R ²⁰ are each independently a hydrogen atom, a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, It represents an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group, and these may further have a substituent.

The cycloalkyl group represented by R ^{1 to} R ²⁰ is preferably a cycloalkyl group having 3 to 8 carbon atoms, specifically, a group such as cyclopropyl, cyclopentyl, cyclohexyl and the like. These groups may be substituted, and preferred substituents include halogen atoms such as chlorine atom, bromine atom, fluorine atom, hydroxyl group, alkyl group, alkoxy group, cycloalkoxy group, aralkyl group (this phenyl group). The group may be further substituted with an alkyl group or a halogen atom), an alkenyl group such as a vinyl group or an allyl group, or a phenyl group (this phenyl group may be further substituted with an alkyl group or a halogen atom). Phenoxy group (this phenyl group may be further substituted by an alkyl group or a halogen atom), an acyl group having 2 to 8 carbon atoms such as an acetyl group or a propionyl group, an acetyloxy group, or a propionyloxy group. And an unsubstituted carbonyloxy group having 2 to 8 carbon atoms such as a group.

The aralkyl group represented by R ^{1 to} R ²⁰ represents a group such as a benzyl group, a phenethyl group, and a γ-phenylpropyl group, and these groups may be substituted. Preferred substituents include The group which may be substituted with the said cycloalkyl group can be mentioned similarly.

Examples of the alkoxy group represented by R ^{1 to} R ²⁰ include an alkoxy group having 1 to 8 carbon atoms. Specifically, methoxy, ethoxy, n-propoxy, n-butoxy, n-octyloxy, isopropoxy , Alkoxy groups such as isobutoxy, 2-ethylhexyloxy, or t-butoxy. These groups may be substituted, and preferred substituents include halogen atoms such as chlorine atom, bromine atom, fluorine atom, hydroxyl group, alkoxy group, cycloalkoxy group, aralkyl group (this phenyl group). May be substituted with an alkyl group or a halogen atom), an alkenyl group, a phenyl group (this phenyl group may be further substituted with an alkyl group or a halogen atom), an aryloxy group (for example, phenoxy) An acyl group such as an acetyl group or a propionyl group, or an aryl group such as an acetyloxy group or a propionyloxy group (the phenyl group may be further substituted with an alkyl group or a halogen atom). Arylcarbonyl groups such as unsubstituted acyloxy groups and benzoyloxy groups Shi group.

Examples of the cycloalkoxy group represented by R ^{1 to} R ²⁰ include an unsubstituted cycloalkoxy group having 1 to 8 carbon atoms, specifically, cyclopropyloxy, cyclopentyloxy, cyclohexyl. And groups such as oxy. In addition, these groups may be substituted, and preferred substituents include the same groups that may be substituted with the cycloalkyl group.

Examples of the aryloxy group represented by R ^{1 to} R ²⁰ include a phenoxy group, and the phenyl group includes a substituent that is exemplified as a group that may be substituted with the cycloalkyl group such as an alkyl group or a halogen atom. May be substituted.

Examples of the aralkyloxy group represented by R ^{1 to} R ²⁰ include a benzyloxy group and a phenethyloxy group, and these substituents may be further substituted. Preferred substituents include the above cycloalkyl The group which may be substituted with a group can be mentioned similarly.

Examples of the acyl group represented by R ^{1 to} R ²⁰ include an unsubstituted acyl group having 2 to 8 carbon atoms such as an acetyl group and a propionyl group (the hydrocarbon group of the acyl group includes alkyl, alkenyl, alkynyl). These substituents may be further substituted, and preferable substituents include the same groups that may be substituted with the cycloalkyl group.

The carbonyloxy group represented by R ^{1 to} R ²⁰ is an unsubstituted acyloxy group having 2 to 8 carbon atoms such as acetyloxy group and propionyloxy group (the hydrocarbon group of the acyl group is alkyl, alkenyl, alkynyl). And arylcarbonyloxy groups such as a benzoyloxy group, and these groups may be further substituted with the same groups as those which may be substituted with the cycloalkyl group.

The oxycarbonyl group represented by R ^{1 to} R ²⁰ represents an alkoxycarbonyl group such as a methoxycarbonyl group, an ethoxycarbonyl group or a propyloxycarbonyl group, or an aryloxycarbonyl group such as a phenoxycarbonyl group. These substituents may be further substituted, and preferred examples of the substituent include the same groups that may be substituted with the cycloalkyl group.

As the oxycarbonyl group represented by R ¹ to R ^20, represents an alkoxycarbonyloxy group having 1-8 carbon atoms such as a methoxycarbonyloxy group, these substituents may be further substituted, Preferable substituents include the same groups that may be substituted on the cycloalkyl group. In addition, any one of R ^{1 to} R ²⁰ may be connected to each other to form a ring structure.

R ²¹ represents an alkyl group, preferably a linear alkyl group having 1 to 8 carbon atoms.

  The compound represented by general formula (2), general formula (3), or general formula (4) can be synthesized by a known method, and typical synthesis examples will be described later. Although there is no restriction | limiting in particular in the molecular weight of the compound represented by General formula (2), General formula (3), or General formula (4) obtained, It is preferable that it is 300-1500, and it is 400-1000. Further preferred. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  Below, the specific compound of the polyhydric alcohol ester concerning this invention is illustrated.

  The cellulose acylate film used in the present invention contains at least the compound represented by the general formula (1) according to the present invention, but may be used in combination with other additives.

  The compound represented by the general formula (1) according to the present invention is highly compatible with the cellulose ester and has a feature that it can be added at a high addition rate. Therefore, a plasticizer and other additives are used in combination. However, bleed-out does not occur, and a plasticizer and other additives can be easily used together if necessary.

  In addition, when using a plasticizer together, it is preferable that the compound of this invention contains at least 50 mass% or more of the whole additive. More preferably 70% or more, still more preferably 80% or more. If it uses in such a range, even if it uses together with a plasticizer, the fixed effect that the planarity of the cellulose ester film at the time of melt casting can be improved can be acquired.

  The plasticizer used in combination is an aliphatic carboxylic acid-polyhydric alcohol plasticizer, an unsubstituted aromatic carboxylic acid or cycloalkyl carboxylic acid as described in paragraphs 30 to 33 of JP-A-2003-12823. A polyhydric alcohol ester plasticizer or dioctyl adipate, dicyclohexyl adipate, diphenyl succinate, di2-naphthyl-1,4-cyclohexanedicarboxylate, tricyclohexyl tricarbarate, tetra 3-methylphenyltetrahydrofuran-2,3 , 4,5-tetracarboxylate, tetrabutyl-1,2,3,4-cyclopentanetetracarboxylate, triphenyl-1,3,5-cyclohexyltricarboxylate, triphenylbenzene-1,3,5-tetra Carboxy Phthalic acid plasticizers (eg diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate, methyl phthalyl methyl glycolate, ethyl phthalyl Polyvalent carboxylic acid esters such as ethyl glycolate, propylphthalylpropyl glycolate, butylphthalylbutyl glycolate, etc.) and citric acid plasticizers (acetyltrimethyl citrate, acetyltriethyl citrate, acetyltributyl citrate, etc.) Plasticizer, triphenyl phosphate, biphenyl diphenyl phosphate, butylene bis (diethyl phosphate), ethylene bis (diphenyl phosphate) ), Phenylene bis (dibutyl phosphate), phenylene bis (diphenyl phosphate) (Adeka Stub PFR manufactured by Asahi Denka), phenylene bis (dixylenyl phosphate) (Adeka Stab FP500 manufactured by Asahi Denka), bisphenol A diphenyl phosphate (Adeka Stub manufactured by Asahi Denka) FP600) and the like, and polyether plasticizers such as polymer polyesters described in paragraph Nos. 49 to 56 of JP-A No. 2002-22956.

  However, since phosphoric acid plasticizers are prone to coloration when used for melt film formation of cellulose esters, phthalic acid ester plasticizers, polycarboxylic acid ester plasticizers, citrate ester plasticizers, and polyester plasticizers. It is preferable to use an agent and a polyether plasticizer.

  In addition, since the cellulose acylate film of this invention will affect as an optical use when it colors, Preferably yellow degree (yellow index, YI) is 3.0 or less, More preferably, it is 1.0 or less. Yellowness can be measured based on JIS-K7103.

(Cellulose acylate)
The cellulose acylate used in the present invention will be described in detail. In the present invention, the cellulose acylate constituting the optical film is preferably a cellulose acylate having an aliphatic acyl group having 2 or more carbon atoms, more preferably, the total acyl substitution degree of the cellulose acylate is 2.95 or less, and This is a cellulose acylate having an acyl group total carbon number of 6.2 or more and 7.5 or less. The acyl group total carbon number of the cellulose acylate is preferably 6.5 or more and 7.2 or less, and more preferably 6.7 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, more preferably 2 or more and 4 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.

  Glucose units constituting cellulose with β-1,4-glycoside bonds have free hydroxyl groups at the 2nd, 3rd and 6th positions. The cellulose acylate in the present invention is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group. The degree of substitution represents the total ratio of cellulose esterified at the 2nd, 3rd and 6th positions of the repeating unit. Specifically, the degree of substitution is 1 when the hydroxyl groups at the 2-position, 3-position and 6-position of cellulose are each 100% esterified. Therefore, when all of the 2nd, 3rd and 6th positions of cellulose are 100% esterified, the degree of substitution is 3 at the maximum.

  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.

  The present inventors have found that the mechanical properties and saponification properties of cellulose acylate films and the melt film-forming properties of cellulose acylates are in a trade-off relationship with respect to the total carbon number of acyl groups of cellulose acylate. I figured it out. For example, in cellulose acetate propionate, if the total carbon number of the acyl group is increased, melt film-forming properties are improved, but mechanical properties are lowered, and it is difficult to achieve both. However, in the present invention, by making the total acyl substitution degree of cellulose acylate 2.9 or less and the acyl group total carbon number to be 6.5 or more and 7.2 or less, film mechanical properties, saponification properties, melting It has been found that film forming properties can be achieved. 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, when the total substitution degree of acyl groups is equal, longer chain acyl groups such as propionyl group and butyryl group become more hydrophobic than acetyl groups, thereby improving melt film-forming properties. Therefore, when achieving the same melt film-forming properties, long chain acyl groups such as propionyl group and butyryl group have lower substitution degree and lower total substitution degree than acetyl group, so mechanical properties, saponification It is presumed that the decrease in sex can be suppressed.

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

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

  The cellulose ester 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 an acetyl group, propionyl group and / or butyl group within the above range. . The method for synthesizing such a cellulose ester 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 ester is synthesized industrially 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 ester obtained. In order to affect the quality of the film, the residual sulfuric acid content in the cellulose ester 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 washing step of the cellulose resin becomes too large. 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 acid is preferably 1000 ppm or less.

  By washing the synthesized cellulose ester more sufficiently than when used in the solution casting method, the residual sulfuric acid content can be within the above range, and when producing a film by the melt casting method. Further, 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.

  Moreover, it is preferable that the cellulose ester used by this invention is a thing with few bright spot foreign materials when it is made into a film. A bright spot foreign material is an arrangement in which two polarizing plates are arranged orthogonally (crossed Nicols), a cellulose ester film is arranged between them, light from the light source is applied from one side, and the cellulose ester film is applied from the other side. This is the point where the light from the light source appears to leak when observed. 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 ester, and use a cellulose ester with a little bright spot foreign matter (use a cellulose ester with a small dispersion of substitution degree). And filtering the melted cellulose ester, or removing the bright spot foreign matters through the filtration process in the same way once in the solution state in at least one of the process of synthesizing the cellulose ester and the process of obtaining the precipitate You can also. 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 ester content in the film decreases, the bright spot foreign matter tends to decrease. 0.01 mm or more is preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, further preferably 50 pieces / cm ² or less, and 30 pieces / cm ² or less. Preferably, it is preferably 10 pieces / 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, it is more effective to filter the composition mixed with a plasticizer, deterioration inhibitor, antioxidant, etc. than to filter the melted cellulose ester alone. This is preferable because of its high removal efficiency. Of course, the cellulose ester may be dissolved in a solvent during the synthesis 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 ester having a viscosity of 10,000 Pa · s or less, more preferably 5000 Pa · s or less, further preferably 1000 Pa · s or less, and more preferably 500 Pa · s or less. More preferably. 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 ester obtained by dissolving the raw material cellulose ester at least once in a solvent and then drying the solvent may be used. In that case, a cellulose ester 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 ester is used, each additive in a molten state can be easily made uniform, and optical characteristics can be made uniform.

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

(Other additives)
In the cellulose acylate film of the present invention, in addition to the cellulose ester and the plasticizer, a stabilizer, a slip agent, a matting agent, a filler, an inorganic polymer, an organic polymer, a dye, a pigment, a phosphor, an ultraviolet absorber, Infrared absorber, dichroic dye, refractive index adjuster, retardation control agent, gas permeation suppressor, antibacterial agent, conductivity imparting agent, biodegradability imparting agent, anti-gelling agent, viscosity modifier, etc. An additive having a function may be added as desired.

  Since the cellulose ester of the present invention is melted and formed at a high temperature of 200 to 250 ° C., the cellulose ester is a process in which decomposition and deterioration of the cellulose ester are likely to occur as compared with conventional solution casting film formation. Among the agents, a stabilizer is preferably added to the film forming material.

  Examples of stabilizers include, but are not limited to, antioxidants, acid scavengers, hindered amine light stabilizers, ultraviolet absorbers, peroxide decomposers, radical scavengers, metal deactivators, and the like. Not. These are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. It is preferable that at least one selected from these is included in the film-forming material.

  In addition, when the cellulose acylate film of the present invention is used as a polarizer protective film, a retardation film, etc., since the polarizer is weak against ultraviolet rays, at least the cellulose acylate film on the light incident side with respect to the polarizer is used. Preferably contains an ultraviolet absorber.

  Moreover, when using the cellulose acylate film of this invention as a retardation film, the additive for adjusting retardation can be contained. As the compound to be added for adjusting the retardation, a retardation controlling agent as described in EP 911,656 A2 can be used.

  In addition, an organic polymer or an inorganic polymer can be added to the cellulose acylate film in order to control the viscosity at the time of heat-melting and adjust the film physical properties after film processing.

  When these additives are added to the cellulose ester resin, the total amount including them is preferably 1 to 30% by mass with respect to the mass of the cellulose resin. If the amount is 1% by mass or less, the melt film-forming property is lowered, and if it is 30% by mass or more, the mechanical properties and storage stability of the obtained cellulose acylate film may not be ensured.

(Antioxidant)
Cellulose ester contains an antioxidant as a stabilizer in the cellulose acylate film of the present invention because decomposition is accelerated not only by heat but also by oxygen in a high temperature environment where melt film formation is performed. Is preferred.

  The antioxidant useful in the present invention can be used without limitation as long as it is a compound that suppresses the deterioration of the melt-molded material due to oxygen. Among them, useful antioxidants include hindered phenol-based antioxidants, Examples include hindered amine-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, heat-resistant processing stabilizers, oxygen scavengers, etc. Among these, hindered phenol-based antioxidants, hindered amine-based antioxidants, phosphorus-based compounds, among others. Antioxidants are preferred.

  By blending these antioxidants, it is possible to prevent coloring and strength reduction of the molded product due to heat during heat molding or deterioration due to thermal oxidation without lowering transparency, heat resistance and the like. These antioxidants can be used alone or in combination of two or more.

  Among the above antioxidants, hindered phenol antioxidants are preferable. 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. Among such compounds, preferred compounds include compounds represented by the following general formula (5).

In the formula, R ₂₁ , R ₂₂ and R ₂₃ represent an alkyl substituent which is further substituted or unsubstituted. Specific examples of hindered phenol compounds 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-tert-butyl-4-hydroxybenzoate, n-hexyl 3,5-di-tert-butyl-4-hydroxyphenylbenzoate, n-dodecyl 3, 5-di-t-butyl-4-hydroxyphenylbenzoate, neo-dodecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl β (3,5-di-t-butyl- 4-hydroxyphenyl) propionate, ethyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octade Sil 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 bis- (3,5-di-t-butyl-4) -Hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl 3- (3,5-di-t-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-t-butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl 3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl 7- (3-methyl-5-tert-butyl-4- Hydroxyphenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5-di-tert-butyl-4-hydroxyl Nyl) propionate], ethylene glycol bis- [3- (3,5-di-t-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-1-n-octadecanoate-2,3-bis- (3 5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol-tetrakis- [3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate], 1,1,1 -Trimethylolethane-tris- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], sorbite Ruhexa- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) propionate, 2- Stearoyloxyethyl 7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ', 5'-di-t-butyl-4-hydroxy Phenyl) propionate], pentaerythritol-tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate). Hindered phenol compounds of the type described above are commercially available, for example, from Ciba Specialty Chemicals under the trade names “Irganox 1076” and “Irganox 1010”.

  The phosphorus-based antioxidant is a known compound, for example, a compound represented by the general formula (1) in JP-A-2002-138188, a formula (2) in the formula (2), ( The compound represented by 3) and (4) and the compound represented by the general formula (4) in JP-A-2005-344044 are preferred. Specifically, compounds represented by the formulas (5) to (8) and (9) to (11) of the above-mentioned JP-A No. 2004-182979, or tetrakis (2,4-di-t-butyl) Phenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, tetrakis (2,6-di-t-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite Tetrakis (2,6-di-t-butylphenyl-4-methyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, bis (2.6-di-t-butyl-4- Methylphenyl) pentaerythritol diphosphite, bis (2-tert-butyl-4-cumylphenyl) pentaerythritol diphosphite, bis (4-tert-butyl-2-cumylphenyl) pentaerythritol diphosphite Bis (2.6-di-t-butyl-4-ethylphenyl) pentaerythritol diphosphite, bis (2.4-di-t-butyl-6-methylphenyl) pentaerythritol diphosphite Can do. In addition, compounds described in JP-A-10-306175, JP-A-1-254744, JP-A-2-270892, JP-A-5-202078, JP-A-5-178870 and JP-T-2004-504435 are used. Can be mentioned.

  Moreover, as a commercial item, Sumilizer GP (made by Sumitomo Chemical Co., Ltd.), PEP-36 (made by Asahi Denka Co., Ltd.), GSY-P101 (made by UPI Corporation), etc. are mentioned.

  The antioxidant is preferably added in an amount of 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and further preferably 0.5 to 2% by mass. Two or more of these may be used in combination.

(Acid scavenger)
Since cellulose ester is decomposed by an acid in a high temperature environment where melt film formation is performed, the cellulose acylate optical film of the present invention preferably contains an acid scavenger as a stabilizer. 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. A compound having an epoxy group is 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 Epoxidized vegetable oils and other unsaturated natural oils, which may be represented and exemplified by compositions of various epoxidized long chain fatty acid triglycerides and the like (eg, epoxidized soybean oil, epoxidized linseed oil, etc.) As epoxidized natural glycerides or unsaturated fatty acids, which generally contain from 12 to 22 carbon atoms). Further, as a commercially available epoxy group-containing epoxide resin compound, EPON 815C and other epoxidized ether oligomer condensation products represented by the following general formula (6) can also be preferably used.

  In formula, n is an integer of 0-12. Other acid scavengers that can be used include those described in paragraphs 87 to 105 of JP-A-5-194788.

  The acid scavenger is preferably added in an amount of 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and further preferably 0.5 to 2% by mass. Two or more of these may be used in combination.

  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.

(UV absorber)
The ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the polarizer and the display device with respect to ultraviolet rays, and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Those are preferred. Examples of the ultraviolet absorber used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. However, benzophenone compounds, less colored benzotriazole compounds, and triazine compounds are preferable. Further, ultraviolet absorbers described in JP-A Nos. 10-182621 and 8-337574, and polymer ultraviolet absorbers described in JP-A Nos. 6-148430 and 2003-113317 may be used.

  Specific examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzo Triazole, 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'-hydroxy- '-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (straight 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-5 A mixture of (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  As commercial products, TINUVIN 171, TINUVIN 234, TINUVIN 360, TINUVIN 928 (all manufactured by Ciba Specialty Chemicals), and LA31 (Asahi Denka) are listed. It is done.

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

  In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and further preferably 0.5 to 2% by mass. Two or more of these may be used in combination.

  These benzotriazole structures and benzophenone structures may be partly or regularly pendant to the polymer, and the molecular structure of other additives such as plasticizers, antioxidants, and acid scavengers. Some may be introduced.

(Hindered amine compounds)
In addition to the above antioxidants, acid scavengers, and UV absorbers, hindered amine compounds can be cited as additives that can suppress decomposition of cellulose esters by heat and light, and in cellulose acylate films as necessary. You may add to.

  Examples of the hindered amine compound (HALS) used in the present invention include, for example, columns 5 to 11 of U.S. Pat. No. 4,619,956 and columns 3 to 5 of U.S. Pat. No. 4,839,405. 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds. Such a compound includes a compound represented by the following general formula (7).

In the formula, R ₃₁ and R ₃₂ are a hydrogen atom or a substituent. Specific examples of hindered amine 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-stearoyloxy-2 , 2,6,6-tetramethylpiperidine, 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6,6-penta Methylpiperidine, 1,2,2,6,6-pentamethylpiperidin-4-yl-β (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, 1-ben L-2,2,6,6-tetramethyl-4-piperidinylmaleate, (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-piperidin-4-yl) Ester, dimethyl-bis- (2,2,6,6-tetramethylpiperidin-4-oxy) -silane, tris- (1-propyl-2,2,6,6-tetramethylpiperidin-4-yl) -Phosphite, tris- (1-propyl-2,2,6,6-tetramethylpiperidin-4-yl) -phosphate, N, N'-bis- (2,2,6,6-tetramethylpiperidine- 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 Tetramethylpiperidin-4-yl)]-amino-acrylic acid methyl ester, tetrakis (1,2,2,6,6-pentamethyl-6-piperidyl) -1,2,3,4-butanetetracarboxylate and the like. Can be mentioned. Examples of preferred hindered amine compounds include, but are not limited to, the following HALS-1 and HALS-2. As a commercial item, LA52 (made by Asahi Denka Co., Ltd.) can be mentioned.

  It is preferable to contain at least one of the above compounds, and the content is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass with respect to the mass of the cellulose ester resin. Preferably it is 0.2-2 mass%.

If the content of the compound is 0.01% by mass or more, thermal decomposition of the cellulose ester resin can be suppressed, and if it is 5% by mass or less, a polarizing plate protective film from the viewpoint of compatibility with the resin. Sufficient transparency can be obtained, and the film can be prevented from becoming too brittle, which is preferable.
(Carbon radical scavenger)
The cellulose acylate film of the present invention preferably contains a carbon radical scavenger as a heat-resistant processing stabilizer in a high temperature environment where melt film formation is performed.

  The “carbon radical scavenger” used in the present invention has a group (for example, an unsaturated group such as a double bond or triple bond) in which a carbon radical can quickly undergo an addition reaction, and is polymerized after the carbon radical is added. Means a compound that gives a stable product in which no subsequent reaction takes place. Examples of the carbon radical scavenger include compounds having a radical polymerization inhibitory ability such as a group (unsaturated group such as (meth) acryloyl group and aryl group) that reacts quickly with a carbon radical in the molecule, and a phenolic or lactone based compound. The compound represented by the following general formula (8) or the following general formula (9) is particularly preferable.

In the general formula (8), R ⁴¹ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, particularly preferably a hydrogen atom or a methyl group. . R ⁴² and R ⁴³ each independently represent an alkyl group having 1 to 8 carbon atoms, and may be linear or have a branched structure or a ring structure. R ⁴² and R ⁴³ are preferably a structure represented by “* —C (CH ₃ ) ₂ —R ′” containing a quaternary carbon (* represents a connecting site to an aromatic ring, and R ′ has 1 carbon atom) Represents an alkyl group of ˜5). R ⁴² is more preferably a tert-butyl group, a tert-amyl group or a tert-octyl group. R ⁴³ is more preferably a tert-butyl group or a tert-amyl group. As the compound represented by the general formula (8), commercially available products include “Sumilizer GM, Sumilizer GS” (both trade names, manufactured by Sumitomo Chemical Co., Ltd.) and the like. Specific examples (I-1 to I-18) of the compound represented by the general formula (8) are illustrated below, but the present invention is not limited thereto.

In the general formula (9), R ^{52 to} R ⁵⁵ each independently represent a hydrogen atom or a substituent, and the substituent represented by R ^{52 to} R ⁵⁵ is not particularly limited. For example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc., cycloalkyl group (for example, cyclopentyl group, cyclohexyl group, etc.) ), Aryl groups (eg, phenyl group, naphthyl group, etc.), acylamino groups (eg, acetylamino group, benzoylamino group, etc.), alkylthio groups (eg, methylthio group, ethylthio group, etc.), arylthio groups (eg, phenylthio group) , Naphthylthio group, etc.), alkenyl group (for example, vinyl group, 2-propenyl group, 3-butenyl group, 1 Methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group, 4-hexenyl group, cyclohexenyl group, etc.), halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.) , Alkynyl groups (eg, propargyl group), heterocyclic groups (eg, pyridyl group, thiazolyl group, oxazolyl group, imidazolyl group, etc.), alkylsulfonyl groups (eg, methylsulfonyl group, ethylsulfonyl group, etc.), arylsulfonyl groups (Eg, phenylsulfonyl group, naphthylsulfonyl group, etc.), alkylsulfinyl group (eg, methylsulfinyl group, etc.), arylsulfinyl group (eg, phenylsulfinyl group, etc.), phosphono group, acyl group (eg, acetyl group, pivaloyl group) , Benzoyl groups, etc.), carbamoyl groups (eg For example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylamino) Sulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group) , Sulfonamide groups (for example, methanesulfonamide group, benzenesulfonamide group, etc.), cyano groups, alkoxy groups (for example, methoxy group, Xy group, propoxy group etc.), aryloxy group (eg phenoxy group, naphthyloxy group etc.), heterocyclic oxy group, siloxy group, acyloxy group (eg acetyloxy group, benzoyloxy group etc.), sulfonic acid group, Salt of sulfonic acid, aminocarbonyloxy group, amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc.), anilino group (for example, , Phenylamino group, chlorophenylamino group, toluidino group, anisidino group, naphthylamino group, 2-pyridylamino group, etc.), imide group, ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, Octylureido group, dodecyl Raid group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), alkoxycarbonylamino group (eg, methoxycarbonylamino group, phenoxycarbonylamino group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl) Groups, phenoxycarbonyl, etc.), aryloxycarbonyl groups (eg, phenoxycarbonyl group, etc.), heterocyclic thio groups, thioureido groups, carboxyl groups, carboxylic acid salts, hydroxyl groups, mercapto groups, nitro groups, etc. It is done. These substituents may be further substituted with the same substituent.

In the general formula (9), R ⁵⁶ represents a hydrogen atom or a substituent, and examples of the substituent represented by R ⁵⁶ include the same groups as the substituents represented by R ^{52 to} R ^55. .

  In the general formula (9), n represents 1 or 2.

In the general formula (9), when n is 1, R ⁵¹ represents a substituent, and when n is 2, R ⁵¹ represents a divalent linking group. When R ⁵¹ represents a substituent, examples of the substituent include the same groups as the substituents represented by R ^{52 to} R ⁵⁵ .

When R ⁵¹ represents a divalent linking group, examples of the divalent linking group include an alkylene group that may have a substituent, an arylene group that may have a substituent, an oxygen atom, a nitrogen atom, and a sulfur atom. Or a combination of these linking groups.

  In the general formula (9), n is preferably 1.

  As the lactone compound represented by the general formula (9), compounds described in JP-A-7-233160 and JP-A-7-247278 are preferable. Moreover, HP-136 (made by Ciba Specialty Chemicals) can be mentioned as a commercial item.

  Next, although the specific example of a compound represented by the said General formula (9) in this invention is shown, this invention is not limited by the following specific examples.

  The above-mentioned carbon radical scavengers can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within the range not impairing the object of the present invention. Usually, it is 0.001-10.0 mass part, Preferably it is 0.01-5.0 mass part, More preferably, it is 0.1-1.0 mass part.

(Matting agent)
A matting agent can be added to the cellulose acylate film of the present invention in order to impart sliding properties, optical and mechanical functions. Examples of the matting agent include inorganic compound fine particles and organic compound fine particles.

  The shape of the matting agent is preferably a spherical shape, a rod shape, a needle shape, a layer shape, a flat shape or the like. Examples of the matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Examples thereof include inorganic fine particles such as oxides, phosphates, silicates, and carbonates, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. These fine particles are preferably surface-treated with an organic substance because the haze of the film can be reduced.

  The surface treatment is preferably performed with halosilanes, alkoxysilanes, silazane, siloxane, or 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 primary particle size of the fine particles is in the range of 0.01 to 1.0 μm. The average particle diameter of primary particles of preferable fine particles is preferably 5 to 50 nm, and more preferably 7 to 14 nm. These fine particles are preferably used for generating irregularities of 0.01 to 1.0 μm on the surface of the cellulose acylate film.

  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. 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.

  These matting agents are preferably added by kneading. Further, as another form, after mixing and dispersing a matting agent previously dispersed in a solvent and a cellulose ester and / or a plasticizer and / or an ultraviolet absorber, a solid material obtained by volatilizing or precipitating the solvent is obtained. It is preferable to use it in the production process of the ester melt from the viewpoint that the matting agent can be uniformly dispersed in the cellulose resin.

  The matting agent can also be added to improve the mechanical, electrical and optical properties of the film.

  As the fine particles are added, the slipping property of the resulting cellulose acylate film is improved. However, the haze increases as the fine particles are added, so the content is preferably 0.001 to 5% by mass, more preferably. It is 0.005-1 mass%, More preferably, it is 0.01-0.5 mass%.

  As the cellulose acylate film of the present invention, if the haze value exceeds 1.0%, the optical material is affected. Therefore, the haze value is preferably less than 1.0%, more preferably less than 0.5%. is there. The haze value can be measured based on JIS-K7136.

(Melt casting method)
The film constituent material is required to have little or no volatile component in the melting and film forming process. This is for foaming during heating and melting to reduce or avoid defects inside the film and flatness deterioration of the film surface.

  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, more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less. It is desirable that In the present invention, a heat loss from 30 ° C. to 250 ° C. is determined using a differential thermal mass measuring apparatus (TG / DTA200 manufactured by Seiko Electronics Industry Co., Ltd.), and the amount is defined as the content of volatile components.

  It is preferable that the film constituent material used removes volatile components typified by the moisture and the solvent before film formation or during heating. As the removal method, a so-called known drying method can be applied, which can be performed by a method such as a heating method, a reduced pressure method, a heated reduced pressure method, or the like, and may be performed in air or in an atmosphere where nitrogen is selected as an inert gas. . When performing these known drying methods, it is preferable in terms of film quality to be performed in a temperature range in which the film constituting material does not decompose.

  By drying prior to film formation, the generation of volatile components can be reduced, and the resin can be divided into a single resin, or at least one mixture or compatible material other than resin, and dried. You can also The drying temperature is preferably 100 ° C. or higher. When a material having a glass transition temperature is present in the material to be dried, heating to a drying temperature higher than the glass transition temperature may cause the material to melt and become difficult to handle. It is preferable that it is below the temperature. When a plurality of substances have a glass transition temperature, the glass transition temperature with the lower glass transition temperature is used as a reference. More preferably, it is 100 degreeC or more and (glass transition temperature-5) degreeC or less, More preferably, it is 110 degreeC or more and (glass transition temperature-20) degreeC or less. The drying time is preferably 0.5 to 24 hours, more preferably 1 to 18 hours, and further preferably 1.5 to 12 hours. If the drying temperature is too low, the removal rate of volatile components will be low, and it will take too much time to dry. Further, the drying process may be divided into two or more stages. For example, the drying process includes a preliminary drying process for storing the material and a drying process immediately before the film is formed immediately before to 1 week before film formation. Also good.

  Melt casting film forming methods are classified into molding methods that are heated and melted, and melt extrusion molding methods, press molding methods, inflation methods, injection molding methods, blow molding methods, stretch molding methods, and the like can be applied. Among these, in order to obtain an optical film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent. Hereinafter, the method for producing the film of the present invention will be described by taking the melt extrusion method as an example.

  FIG. 1 is a schematic flow sheet showing an overall configuration of an example of an apparatus for carrying out the method for producing a cellulose acylate optical film of the present invention, and FIG. 2 is an enlarged view of a cooling roll portion from a casting die.

  In FIG. 1 and FIG. 2, the method for producing an optical film according to the present invention mixes film materials such as cellulose resin, and then melts and extrudes from a casting die 4 onto a first cooling roll 5 using an extruder 1. While circumscribing the 1st cooling roll 5, it is further circumscribed by the total of 3 cooling rolls of the 2nd cooling roll 7 and the 3rd cooling roll 8 in order, and it cools and solidifies to make the film 10. Next, the film 10 peeled off by the peeling roll 9 is then stretched in the width direction by holding both ends of the film by the stretching device 12, and then wound by the winding device 16. In addition, a touch roll 6 is provided that clamps the molten film on the surface of the first cooling roll 5 in order to correct the flatness. The touch roll 6 has an elastic surface and forms a nip with the first cooling roll 5. Details of the touch roll 6 will be described later.

  In the method for producing an optical film according to the present invention, the conditions for melt extrusion can be carried out in the same manner as those used for other thermoplastic resins such as polyester. The material is preferably dried beforehand. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less, using a vacuum or reduced pressure dryer or a dehumidifying hot air dryer.

  For example, a cellulose ester resin dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C., more preferably 230 to 260 ° C. using an extruder 1, and a leaf disk type filter 2 or the like is used. Filter to remove foreign matter.

  When introducing into the extruder 1 from a supply hopper (not shown), it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

  When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer 3.

  In the present invention, it is preferable that the cellulose resin and other additives such as a stabilizer added as necessary are mixed before melting. More preferably, the cellulose resin and the stabilizer are mixed first. Mixing may be performed by a mixer or the like, or may be mixed in the cellulose resin preparation process as described above. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, a Henschel mixer, or a ribbon mixer can be used.

  After the film constituent materials are mixed as described above, the mixture may be melted directly using the extruder 1 to form a film. Once the film constituent materials are pelletized, the pellets are extruded. The film may be melted by the machine 1 to form a film. When the film constituent material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only the material having a low melting point is melted, and the semi-melt is supplied to the extruder 1. It is also possible to form a film by introducing it. If the film component contains a material that is easily pyrolyzed, in order to reduce the number of times of melting, a method of directly forming a film without producing pellets, or after making a paste-like semi-molten material as described above A method of forming a film is preferred.

  As the extruder 1, various extruders available on the market can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used. When forming a film directly without producing pellets from film constituent materials, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is required. However, even with a single-screw extruder, the screw shape is a Maddock type. By changing to a kneading type screw such as a unimelt type or a dull mage, moderate kneading can be obtained, so that it can be used. When a pellet or braided semi-melt is once used as a film constituent material, it can be used in either a single screw extruder or a twin screw extruder.

  In the cooling process in the extruder 1 and after extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or reducing the pressure.

  The melting temperature of the film constituent material in the extruder 1 varies depending on the viscosity and discharge amount of the film constituent material, the thickness of the sheet to be produced, etc., but generally, with respect to the glass transition temperature Tg of the film, Tg or more and Tg + 100 ° C. or less, preferably Tg + 10 ° C. or more and Tg + 90 ° C. or less. The melt viscosity at the time of extrusion is 1 to 10000 Pa · s, preferably 10 to 1000 Pa · s. Further, the residence time of the film constituting material in the extruder 1 is preferably short, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The residence time depends on the type of the extruder 1 and the extrusion conditions, but can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, etc. It is.

  The shape, rotation speed, and the like of the screw of the extruder 1 are appropriately selected depending on the viscosity, the discharge amount, and the like of the film constituent material. In the present invention, the shear rate in the extruder 1 is 1 / second to 10000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second.

  The extruder 1 that can be used in the present invention is generally available as a plastic molding machine.

  The film constituent material extruded from the extruder 1 is sent to the casting die 4 and extruded from the slit of the casting die 4 into a film shape. The casting die 4 is not particularly limited as long as it is used for producing a sheet or a film. The material of the casting die 4 is sprayed or plated with hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Processing includes buffing, lapping using a # 1000 or higher whetstone, flat cutting using a # 1000 or higher diamond whetstone (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, and electrolytic composite polishing. And so on. A preferred material for the lip portion of the casting die 4 is the same as that of the casting die 4. The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

  The slit of the casting die 4 is configured so that the gap can be adjusted. This is shown in FIG. Of the pair of lips forming the slit 32 of the casting die 4, one is a flexible lip 33 having low rigidity and easily deformed, and the other is a fixed lip 34. A large number of heat bolts 35 are arranged at a constant pitch in the width direction of the casting die 4, that is, in the length direction of the slits 32. Each heat bolt 5 is provided with a block 36 having an embedded electric heater 37 and a cooling medium passage, and each heat bolt 35 penetrates each block 36 vertically. The base of the heat bolt 35 is fixed to the die body 31, and the tip is in contact with the outer surface of the flexible lip 33. While constantly cooling the block 36, the input to the embedded electric heater 37 is increased or decreased to increase or decrease the temperature of the block 36, thereby causing the heat bolt 35 to thermally expand and contract, thereby displacing the flexible lip 33 and thereby increasing the film thickness. adjust. Thickness gauges are installed at the required locations in the wake of the die, and the web thickness information detected thereby is fed back to the control device. The thickness information is compared with the set thickness information by the control device, and correction control comes from the same device. It is also possible to control the power or the ON rate of the heat bolt heating element by the amount signal. The heat bolt preferably has a length of 20 to 40 cm and a diameter of 7 to 14 mm, and a plurality of, for example, several tens of heat bolts are preferably arranged at a pitch of 20 to 40 mm. Instead of the heat bolt, a gap adjusting member mainly composed of a bolt for adjusting the slit gap by manually moving back and forth in the axial direction may be provided. The slit gap adjusted by the gap adjusting member is usually 200 to 1000 μm, preferably 300 to 800 μm, more preferably 400 to 600 μm.

  The first to third cooling rolls are made of seamless steel pipe having a wall thickness of about 20 to 30 mm, and the surface is finished to a mirror surface. Inside, a pipe for flowing a coolant is arranged so that heat can be absorbed from the film on the roll by the coolant flowing through the pipe. Of the first to third cooling rolls, the first cooling roll 5 corresponds to the rotary support according to the present invention.

  On the other hand, the touch roll 6 in contact with the first cooling roll 5 has an elastic surface and is deformed along the surface of the first cooling roll 5 by the pressing force to the first cooling roll 5. A nip is formed between the two. That is, the touch roll 6 corresponds to the pinching rotary body of the present invention.

  In FIG. 4, the schematic cross section of one Embodiment (henceforth, touch roll A) of the touch roll 6 is shown. As shown in the drawing, the touch roll A has an elastic roller 42 disposed inside a flexible metal sleeve 41.

  The metal sleeve 41 is made of stainless steel having a thickness of 0.3 mm and has flexibility. If the metal sleeve 41 is too thin, the strength is insufficient, whereas if it is too thick, the elasticity is insufficient. For these reasons, the thickness of the metal sleeve 41 is preferably 0.1 mm or more and 1.5 mm or less. The elastic roller 42 is formed in a roll shape by providing a rubber 44 on the surface of a metal inner cylinder 43 that is rotatable via a bearing. When the touch roll A is pressed toward the first cooling roll 5, the elastic roller 42 presses the metal sleeve 41 against the first cooling roll 5, and the metal sleep 41 and the elastic roller 42 have the shape of the first cooling roll 5. It deforms corresponding to the familiar shape, and forms a nip with the first cooling roll. Cooling water 45 flows in a space formed between the metal sleeve 41 and the elastic roller 42.

  5 and 6 show a touch roll B which is another embodiment of the pinching rotator. The touch roll B includes a flexible, seamless stainless steel pipe (thickness 4 mm) outer cylinder 51, and a highly rigid metal inner cylinder 52 arranged on the same axis as the inner side of the outer cylinder 51. It is roughly composed. A coolant 54 flows in the space 53 between the outer cylinder 51 and the inner cylinder 52. Specifically, in the touch roll B, outer cylinder support flanges 56a and 56b are attached to the rotation shafts 55a and 55b at both ends, and a thin metal outer cylinder 51 is attached between the outer peripheral portions of the both outer cylinder support flanges 56a and 56b. Yes. A fluid supply pipe 59 is disposed in the same axial center in a fluid discharge hole 58 formed in the axial center portion of one rotary shaft 55a and forming a fluid return passage 57. The fluid supply pipe 59 is thin-walled. It is connected and fixed to a fluid shaft cylinder 60 arranged at the axial center in the metal outer cylinder 51. Inner cylinder support flanges 61a and 61b are attached to both ends of the fluid shaft cylinder 60, respectively, and a thickness of about 15 to 20 mm between the outer periphery of the inner cylinder support flanges 61a and 61b and the other end side outer cylinder support flange 56b. A metal inner cylinder 52 having a thickness is attached. A cooling liquid flow space 53 of, for example, about 10 mm is formed between the metal inner cylinder 52 and the thin metal outer cylinder 51, and the metal inner cylinder 52 has a flow space 53 and an inner space near both ends. An outflow port 52a and an inflow port 52b communicating with the intermediate passages 62a and 62b outside the tube support flanges 61a and 61b are formed.

  Further, the outer cylinder 51 is thinned within a range where the thin cylinder theory of elastic mechanics can be applied in order to have flexibility, flexibility, and resilience close to rubber elasticity. The flexibility evaluated by the thin-walled cylinder theory is expressed by the thickness t / roll radius r, and the flexibility increases as t / r decreases. In this touch roll B, the flexibility is the optimum condition when t / r ≦ 0.03. Usually, the touch roll generally used has a roll diameter R = 200 to 500 mm (roll radius r = R / 2), a roll effective width L = 500 to 1600 mm, and a horizontally long shape with r / L <1. is there. As shown in FIG. 6, for example, when the roll diameter R = 300 mm and the roll effective width L = 1200 mm, the appropriate range of the wall thickness t is 150 × 0.03 = 4.5 mm or less, but the molten sheet width is 1300 mm. On the other hand, when the average linear pressure is clamped at 100 N / cm, the equivalent spring constant is equal by setting the thickness of the outer cylinder 51 to 3 mm as compared with the rubber roll of the same shape. The nip width k in the roll rotation direction of the nip is also about 9 mm, which is almost the same as the nip width of this rubber roll of about 12 mm. The deflection amount at the nip width k is about 0.05 to 0.1 mm.

  Here, t / r ≦ 0.03. However, in the case of a general roll diameter R = 200 to 500 mm, flexibility is sufficiently obtained especially in the range of 2 mm ≦ t ≦ 5 mm. Thinning by processing can be easily performed, and it is an extremely practical range. If the wall thickness is 2 mm or less, high-precision processing cannot be performed due to elastic deformation during processing.

  The converted value of 2 mm ≦ t ≦ 5 mm is 0.008 ≦ t / r ≦ 0.05 with respect to a general roll diameter, but in practical use, the roll diameter under the condition of t / r≈0.03. The wall thickness should be increased in proportion to For example, when roll diameter: R = 200, t = 2 to 3 mm, and when roll diameter: R = 500, t = 4 to 5 mm.

The touch rolls A and B are urged toward the first cooling roll by urging means (not shown). The urging force of the urging means is F, and the value F / W (linear pressure) of the film in the nip excluding the width W in the direction along the rotation axis of the first cooling roll 5 is 10 N / cm or more and 150 N / cm. Set to According to the present embodiment, a nip is formed between the touch rolls A and B and the first cooling roll 5, and planarity may be corrected while the film passes through the nip. Therefore, since the film is sandwiched over a long time with a small linear pressure compared to the case where the touch roll is formed of a rigid body and no nip is formed between the first cooling roll and the flatness is more reliably corrected. Can do. That is, when the linear pressure is smaller than 10 N / cm, the die line cannot be sufficiently eliminated. On the other hand, if the linear pressure is greater than 150 N / cm, the film is difficult to pass through the nip, resulting in unevenness in place of the film thickness.
In addition, since the surfaces of the touch rolls A and B are made of metal, the surfaces of the touch rolls A and B can be made smoother than when the surface of the touch roll is rubber. Obtainable. In addition, as a material of the elastic body 44 of the elastic roller 42, ethylene propylene rubber, neoprene rubber, silicon rubber, or the like can be used.

  Now, in order to satisfactorily eliminate the die line by the touch roll 6, it is important that the viscosity of the film when the touch roll 6 clamps the film is in an appropriate range. Cellulose resins are known to have a relatively large change in viscosity with temperature. Therefore, in order to set the viscosity when the touch roll 6 clamps the cellulose film to an appropriate range, it is important to set the temperature of the film when the touch roll 6 presses the cellulose film to an appropriate range. Become. And this inventor can set temperature T of the film just before a film is pinched by the touch roll 6 so that Tg <T <Tg + 110 degreeC may be satisfied, when the glass transition temperature of an optical film is set to Tg. preferable. When the film temperature T is lower than Tg, the viscosity of the film is too high and the die line cannot be corrected. On the contrary, if the temperature T of the film is higher than Tg + 110 ° C., the film surface and the roll do not adhere uniformly, and the die line cannot be corrected. Preferably Tg + 10 ° C. <T 2 <Tg + 90 ° C., more preferably Tg + 20 ° C. <T 2 <Tg + 70 ° C. In order to set the temperature of the film when the touch roll 6 sandwiches the cellulose film to an appropriate range, the first cooling roll starts from the position P1 at which the melt extruded from the casting die 4 contacts the first cooling roll 5. What is necessary is just to adjust the length L along the rotation direction of the 1st cooling roll 5 of the nip of 5 and the touch roll 6. FIG.

  In the present invention, preferable materials for the first roll 5 and the second roll 6 include carbon steel, stainless steel, resin, and the like. The surface accuracy is preferably high, and the surface roughness is 0.3 S or less, more preferably 0.01 S or less.

  In the present invention, it was discovered that the die line correction effect is more greatly manifested by reducing the pressure from the opening (lip) of the casting die 4 to the first roll 5 to 70 kPa or less. The reduced pressure is preferably 50 kPa or more and 70 kPa or less. Although there is no restriction | limiting in particular as a method of keeping the pressure of the part from the opening part (lip | rip) of the casting die 4 to the 1st roll 5 below 70 kPa, Cover the roll periphery from the casting die 4 with a pressure | voltage resistant member, and reduce pressure. There are methods. At this time, the suction device is preferably subjected to a treatment such as heating with a heater so that the device itself does not become a place where the sublimate is attached. In the present invention, if the suction pressure is too small, the sublimate cannot be sucked effectively, so it is necessary to set the suction pressure to an appropriate value.

  In the present invention, a film-like cellulose ester resin in a molten state is transferred from the T die 4 to the first roll (first cooling roll) 5, the second cooling roll 7, and the third cooling roll 8 in order and conveyed. Cooling and solidification is performed while the unstretched cellulose ester resin film 10 is obtained.

  In the embodiment of the present invention shown in FIG. 1, the cooled and solidified unstretched film 10 peeled from the third cooling roll 8 by the peeling roll 9 is guided to a stretching machine 12 via a dancer roll (film tension adjusting roll) 11. Therefore, the film 10 is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented.

  As a method of stretching the film in the width direction, a known tenter or the like can be preferably used. In particular, it is preferable to set the stretching direction to the width direction because lamination with a polarizing film can be performed in a roll form. By stretching in the width direction, the slow axis of the optical film made of the cellulose ester resin film becomes the width direction.

  On the other hand, the transmission axis of the polarizing film is also usually in the width direction. By incorporating a polarizing plate in which the transmission axis of the polarizing film and the slow axis of the optical film are parallel to each other into the liquid crystal display device, the display contrast of the liquid crystal display device can be increased and a good viewing angle can be obtained. Is obtained.

  The glass transition temperature Tg of the film constituting material can be controlled by varying the material type constituting the film and the ratio of the constituting material. When a retardation film is produced as an optical film, Tg is preferably 120 ° C. or higher, preferably 135 ° C. or higher. In the liquid crystal display device, in the image display state, the temperature environment of the film changes due to the temperature rise of the device itself, for example, the temperature rise derived from the light source. At this time, if the Tg of the film is lower than the use environment temperature of the film, the retardation value derived from the orientation state of the molecules fixed inside the film by stretching and the dimensional shape as the film are greatly changed. If the Tg of the film is too high, the temperature is increased when the film constituent material is made into a film, so that the energy consumption for heating is increased, and the material itself may be decomposed when it is made into a film, resulting in coloring. Therefore, Tg is preferably 250 ° C. or lower.

  In the stretching step, known heat setting conditions, cooling, and relaxation treatment may be performed, and adjustment may be made as appropriate so as to have characteristics required for the target optical film.

  In order to provide the physical properties of the retardation film and the function of the retardation film for expanding the viewing angle of the liquid crystal display device, the stretching step and the heat setting treatment are appropriately selected and performed. When such a stretching step and heat setting treatment are included, the heating and pressing step of the present invention is performed before the stretching step and heat setting treatment.

  When a retardation film is produced as an optical film and the functions of a polarizing plate protective film are combined, it is necessary to control the refractive index. However, the refractive index can be controlled by a stretching operation. Is a preferred method. Hereinafter, the stretching method will be described.

  In the retardation film stretching process, the required retardation is obtained by stretching 1.0 to 2.0 times in one direction of the cellulose resin and 1.01 to 2.5 times in the direction perpendicular to the film plane. Ro and Rth can be controlled. Here, Ro indicates in-plane retardation, the difference between the refractive index in the longitudinal direction MD in the plane and the refractive index in the width direction TD is multiplied by the thickness, and Rth indicates the thickness direction retardation. The difference between the refractive index (average of the longitudinal direction MD and the width direction TD) and the refractive index in the thickness direction is multiplied by the thickness.

  Stretching can be performed sequentially or simultaneously, for example, in the longitudinal direction of the film and in the direction orthogonal to the longitudinal direction of the film, that is, in 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 film breakage may occur.

  Stretching in biaxial directions perpendicular to each other is an effective method for bringing the refractive indexes nx, ny, and nz of the film within a predetermined range. Here, nx is the refractive index in the longitudinal MD direction, ny is the refractive index in the width TD direction, and nz is the refractive index in the thickness direction.

  For example, when stretching in the melt casting direction, if the shrinkage in the width direction is too large, the value of nz becomes too large. In this case, it can be improved by suppressing the width shrinkage of the film or stretching in the width direction. When stretching in the width direction, the refractive index may be distributed in the width direction. This distribution may appear when the tenter method is used. By stretching the film in the width direction, a shrinkage force is generated at the center of the film, and the phenomenon is caused by the end being fixed. It is thought to be called the Boeing phenomenon. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed and the distribution of the phase difference in the width direction can be reduced.

  By stretching in the biaxial directions perpendicular to each other, the film thickness variation of the obtained film can be reduced. When the film thickness variation of the retardation film is too large, the retardation becomes uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

  The film thickness variation of the cellulose resin film 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, preferably 1.01 to 1.5 times in the casting direction and 1.05 to 2.0 times in the width direction. It is more preferable to obtain the required retardation value.

  When the absorption axis of the polarizer exists in the longitudinal direction, the transmission axis of the polarizer coincides with the width direction. In order to obtain a long polarizing plate, the retardation film is preferably stretched so as to obtain a slow axis in the width direction.

  When a cellulose resin that obtains positive birefringence with respect to stress is used, the slow axis of the retardation film can be imparted in the width direction by stretching in the width direction from the above-described configuration. In this case, in order to improve the display quality, it is preferable that the slow axis of the retardation film is in the width direction. In order to obtain the target retardation value, the formula: (stretch ratio in the width direction)> ( It is necessary to satisfy the condition of the draw ratio in the casting direction.

  After stretching, after slitting the edge of the film to a product width by the slitter 13, the film is subjected to knurling (embossing) on both ends of the film by a knurling device comprising an embossing ring 14 and a back roll 15. By winding with the winder 16, sticking in the optical film (original winding) F and generation of scratches are prevented. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

  When the retardation film is a polarizing plate protective film, the thickness of the protective film is preferably 10 to 500 μm. In particular, the lower limit is 20 μm or more, preferably 35 μm or more. The upper limit is 150 μm or less, preferably 120 μm or less. A particularly preferred range is 25 to 90 μm. When the retardation film is thick, the polarizing plate after polarizing plate processing becomes too thick, and 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 the retardation film is thin, it is difficult to express retardation as a retardation film, and the moisture permeability of the film is increased, and the ability to protect the polarizer from humidity is reduced, which is not preferable.

  When the slow axis or the fast axis of the retardation film exists in the film plane and the angle formed with the film forming direction is θ1, θ1 is −1 ° to + 1 °, preferably −0.5 ° to +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 (manufactured by Oji Scientific Instruments).

  When each θ1 satisfies the above relationship, it contributes to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to faithful color reproduction in a color liquid crystal display device.

  When the retardation film is used for the multi-domain VA mode, the retardation film is arranged in the above region with the fast axis of the retardation film being θ1, which contributes to the improvement of display image quality. When the plate and the liquid crystal display device are in the MVA mode, for example, the configuration shown in FIG. 7 can be adopted.

  In FIG. 7, 21a and 21b are protective films, 22a and 22b are retardation films, 25a and 25b are polarizers, 23a and 23b are slow axis directions of the film, 24a and 24b are transmission axis directions of the polarizer, 26a, Reference numeral 26b denotes a polarizing plate, 27 denotes a liquid crystal cell, and 29 denotes a liquid crystal display device.

  The retardation Ro distribution in the in-plane direction of the optical film is preferably adjusted to 5% or less, more preferably 2% or less, and particularly preferably 1.5% or less. The retardation Rt distribution in the thickness direction of the film is preferably adjusted to 10% or less, more preferably 2% or less, and particularly preferably 1.5% or less.

  In the retardation film, it is preferable that the retardation value distribution fluctuation is small. When a polarizing plate including a retardation film is used in a liquid crystal display device, the retardation distribution fluctuation is preferably small from the viewpoint of preventing color unevenness and the like.

  The retardation film is adjusted so as to have a retardation value suitable for improving the display quality of the liquid crystal cell of VA mode or TN mode, and is preferably used in the MVA mode by dividing the retardation film into the above multi-domain as the VA mode. For this purpose, it is required to adjust the in-plane retardation Ro to a value greater than 30 nm and 95 nm or less, and the thickness direction retardation Rt to a value greater than 70 nm and 400 nm or less.

  The in-plane retardation Ro is observed from the normal direction of the display surface when the two polarizing plates are arranged in crossed Nicols and the liquid crystal cell is arranged between the polarizing plates, for example, in the configuration shown in FIG. When in a crossed Nicol state with respect to time, when observed obliquely from the normal line of the display surface, the polarizing plate deviates from the crossed Nicol state, and light leakage caused by this is mainly compensated. The retardation in the thickness direction mainly compensates for the birefringence of the liquid crystal cell similarly observed when viewed from an oblique direction when the liquid crystal cell is in the black display state in the TN mode or VA mode, particularly in the MVA mode. Contribute to.

  As shown in FIG. 7, in the liquid crystal display device, when two polarizing plates are arranged above and below the liquid crystal cell, 22a and 22b in the figure can select the distribution of the thickness direction retardation Rt. The total value of both of the above-mentioned ranges and the thickness direction retardation Rt is preferably larger than 140 nm and 500 nm or less. In this case, in-plane retardation Ro and thickness direction retardation Rt of 22a and 22b are preferably the same for improving productivity of an industrial polarizing plate. Particularly preferably, the in-plane retardation Ro is larger than 35 nm and not larger than 65 nm, and the thickness direction retardation Rt is larger than 90 nm and not larger than 180 nm, and is applied to the MVA mode liquid crystal cell in the configuration of FIG.

  In the liquid crystal display device, a TAC film having an in-plane retardation Ro = 0 to 4 nm and a thickness direction retardation Rt = 20 to 50 nm and a thickness of 35 to 85 μm as, for example, a commercially available polarizing plate protective film on one polarizing plate, When used at the position 22b, the polarizing film disposed on the other polarizing plate, for example, the retardation film disposed on 22a in FIG. 7, has an in-plane retardation Ro of more than 30 nm and not more than 95 nm, and The thickness direction retardation Rt is larger than 140 nm and 400 nm or less. The display quality is improved, and this is preferable from the viewpoint of film production.

<Liquid crystal display device>
The polarizing plate comprising the cellulose acylate film of the present invention can express a higher display quality than a normal polarizing plate, and in particular, a multi-domain liquid crystal display device, more preferably a multi-domain type by a birefringence mode. Suitable for use in liquid crystal display devices.

  The polarizing plate of the present invention can be used for MVA (Multi-domain Vertical Alignment) mode, PVA (Patterned Vertical Alignment) mode, CPA (Continuous Pinweal Alignment) mode, OCB (Optical Compensated B mode, etc.). It is not limited to the mode and the arrangement of the polarizing plates.

  Liquid crystal display devices are being applied as devices for colorization and moving image display, and the display quality is improved by the present invention, and the improvement of contrast and the resistance of polarizing plates improve the display of moving images that are less fatigued and faithful. It becomes possible.

  In the liquid crystal display device including at least the polarizing plate including the retardation film of the present invention, one polarizing plate including the retardation film of the present invention is disposed with respect to the liquid crystal cell, or two polarizing plates are provided on both sides of the liquid crystal cell. Place one. At this time, it can contribute to the improvement of display quality by using the retardation film side of the present invention contained in the polarizing plate so as to face the liquid crystal cell of the liquid crystal display device. In FIG. 7, the films 22a and 22b face the liquid crystal cell of the liquid crystal display device.

  In such a configuration, the retardation film of the present invention can optically compensate the liquid crystal cell. When the polarizing plate of the present invention is used in a liquid crystal display device, at least one polarizing plate in the liquid crystal display device may be the polarizing plate of the present invention. By using the polarizing plate of the present invention, a liquid crystal display device with improved display quality and excellent viewing angle characteristics can be provided.

  In the polarizing plate of the present invention, a polarizing plate protective film of a cellulose derivative is used on the surface opposite to the retardation film as viewed from the polarizer, and a general-purpose TAC film or the like can be used. The polarizing plate protective film located on the side far from the liquid crystal cell can be provided with another functional layer in order to improve the quality of the display device.

  For example, it may be affixed to a film containing a known functional layer as a constituent for display in order to prevent reflection, anti-glare, scratch resistance, dust adhesion prevention, brightness improvement, or the polarizing plate surface of the present invention. It is not limited to.

  In general, a retardation film is required to obtain stable optical characteristics that the fluctuation of Ro or Rth is small as the retardation value. In particular, in a liquid crystal display device in a birefringence mode, these fluctuations may cause image unevenness.

  Since the long retardation film produced by the melt casting film forming method according to the present invention is mainly composed of cellulose resin, the alkali treatment process can be utilized by utilizing saponification inherent to cellulose resin. . This can be bonded to the retardation film of the present invention using a completely saponified polyvinyl alcohol aqueous solution in the same manner as a conventional polarizing plate protective film when the resin constituting the polarizer is polyvinyl alcohol. For this reason, this invention is excellent in the point which can apply the conventional polarizing plate processing method, and is excellent especially in the point from which the roll polarizing plate which is elongate is obtained.

  The production effect obtained by the present invention becomes more remarkable particularly in a long roll of 100 m or more, and the longer the length is 1500 m, 2500 m, or 5000 m, the more the production effect of polarizing plate production is obtained.

  For example, in the retardation film production, the roll length is 10 m or more and 5000 m or less, preferably 50 m or more and 4500 m or less in consideration of productivity and transportability. The width of the film at this time is the width of the polarizer or the production. A width suitable for the line can be selected. A film is produced with a width of 0.5 m or more and 4.0 m or less, preferably 0.6 m or more and 3.0 m or less, wound into a roll, and may be used for polarizing plate processing. After a film is manufactured and wound on a roll, the film may be cut to obtain a roll having a desired width, and such a roll may be used for polarizing plate processing.

  When producing the retardation film of the present invention, functional layers such as an antistatic layer, a hard coat layer, a slippery layer, an adhesive layer, an antiglare layer, and a barrier layer may be applied before and / or after stretching. Good. 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 the same kind of film raw material or as a different kind of film raw material. It may be reused.

  An optical film having a laminated structure can be produced by co-extrusion of a composition containing a cellulose resin having different additive concentrations such as the plasticizer, the ultraviolet absorber, and the matting agent. For example, an optical 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 glass transition temperature of the skin layer and the core layer may be different, and the glass transition temperature of the core layer is preferably lower than the glass transition temperature of the skin layer. At this time, the glass transition temperatures of both the skin and the core can be measured, and the average value calculated from these volume fractions can be defined as the glass transition temperature Tg and handled in the same manner. 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 cellulose acylate optical film of the present invention has a dimension stability of ± 2.0 at 80 ° C. and 90% RH when the dimensional stability is based on the size of the film left at 23 ° C. and 55% RH for 24 hours. %, Preferably less than 1.0%, more preferably less than 0.5%.

  When the cellulose acylate optical film of the present invention is used as a protective film for a polarizing plate as a retardation film, if the retardation film itself has a variation beyond the above range, the retardation retardation value and the orientation angle are as follows. Since it deviates from the initial setting, it may cause a decrease in display quality improvement capability or a deterioration in display quality.

  The retardation 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 retardation film was treated with alkali, and a polyvinyl alcohol film was immersed and drawn in an iodine solution, and a polarizer protective film was attached to both sides of the polarizer using a completely saponified polyvinyl alcohol aqueous solution on both sides of the polarizer. There is a method of matching, and at least one surface of the retardation film as the polarizing plate protective film of the present invention is directly bonded to the polarizer.

  Instead of the alkali treatment, a polarizing plate may be processed by applying an easy adhesion process as described in JP-A-6-94915 and JP-A-6-118232.

  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.

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

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

  In Table 1, each symbol represents the following group.

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 The molecular weight was expressed, and the weight average molecular weight was measured by GPC HLC-8220 (manufactured by Tosoh Corporation).

<Synthesis Examples 9 to 41>
Similarly to Synthesis Example 1, cellulose acylates C-9 to C-41 listed in Table 2 were obtained using the corresponding fatty acids and anhydrous fatty acids.

  In Table 2, Ac, Pr, and Bu of the acyl group substitution degree represent the same group as in Table 1, and Pe represents an n-pentanyl group.

Synthesis Example 42 Compound of Comparative Example Synthesis of Trimethylolpropane Tribenzoate (TMPTB) While stirring a mixed solution of 54 parts by mass of trimethylolpropane, 111 parts by mass of pyridine, and 650 parts by mass of toluene maintained at 10 ° C. 170 parts by mass of benzoyl chloride was added dropwise over 30 minutes, then heated to 100 ° C. and stirred for 3 hours. After completion of the reaction, the mixture is cooled to room temperature, and the precipitate is removed by furnace. Then, 1 mol / L aqueous HCl solution is added for washing, and further, 1% Na ₂ CO ₃ aqueous solution is added for washing, and the organic phase is separated. Toluene was distilled off under reduced pressure, and purification was performed to obtain 160 parts by mass (yield 90%) of white crystals TMPTB.

(Synthesis Example 43) Synthesis of Compound Example 2-1 While stirring a mixed solution of 282 parts by mass of phenol, 168 parts by mass of potassium hydroxide, and 450 parts by mass of methanol, 323 parts by mass of 2,2-bis (bromomethyl) -1-bromobutane Was added dropwise to 400 parts by mass of acetone, and then heated to reflux temperature and stirred for 2 hours. After completion of the reaction, the reaction mixture was cooled to room temperature and washed with toluene and water. The organic phase was separated and the treene was distilled off under reduced pressure, followed by purification, and 181 parts by mass (yield 50%) of white crystals. An exemplary compound 2-1 was obtained.

(Synthesis Example 44) Synthesis of Compound Example 2-61 While stirring a mixed solution of 330 parts by mass of thiophenol, 120 parts by mass of sodium hydroxide, and 450 parts by mass of methanol, 323 parts by mass of 2,2-bis (bromomethyl) -1-bromobutane A solution in which 400 parts by mass of acetone was dissolved was added dropwise, and then heated to reflux temperature and stirred for 5 hours. After cooling to room temperature and adding a hydrogen peroxide solution for oxidation treatment, toluene and water were added for washing. The organic phase was separated and the treene was distilled off under reduced pressure, followed by purification to obtain 202 parts by mass (yield 40%) of Exemplified Compound 2-61 as white crystals.

Synthesis Example 45 Synthesis of Compound Example 2-31 430 parts by mass of a sodium salt of benzamide and 323 parts by mass of 2,2-bis (bromomethyl) -1-bromobutane were heated to 180 ° C. and stirred for 8 hours. After completion of the reaction, the reaction mixture was cooled to room temperature and washed with toluene and water. The organic phase was separated, and the treene was distilled off under reduced pressure, followed by purification, and 244 parts by mass (yield 55%) of white crystals. A certain exemplary compound 2-31 was obtained.

(Synthesis Example 46) Synthesis of Compound Example 2-91 538 parts by mass of a sodium salt of benzenesulfonamide and 323 parts by mass of 2,2-bis (bromomethyl) -1-bromobutane were heated to 180 ° C. and stirred for 8 hours. After completion of the reaction, the reaction mixture was cooled to room temperature and washed with toluene and water. The organic phase was separated, and the treene was distilled off under reduced pressure, followed by purification and purification with 248 parts by mass (yield 45%) of white crystals. A certain exemplified compound 2-91 was obtained.

Synthesis Example 47 Synthesis of Compound Example 3-1 While stirring a mixed solution of 282 parts by mass of phenol, 168 parts by mass of potassium hydroxide, and 450 parts by mass of methanol, 281 parts by mass of 1,2,3-tribromopropane was added to acetone 400. The solution dissolved in parts by mass was added dropwise, and then heated to reflux temperature and stirred for 2 hours. After completion of the reaction, the reaction mixture was cooled to room temperature, washed with toluene and water, and the organic phase was separated, and the treene was distilled off under reduced pressure, followed by purification, and 192 parts by mass (yield 60%) of white crystals. An exemplary compound 3-1 was obtained.

(Synthesis Example 48) Synthesis of Compound Example 4-1 1,3-Dibromo-2,2-bis (2-bromomethyl) while stirring a mixed solution of 282 parts by mass of phenol, 168 parts by mass of potassium hydroxide, and 450 parts by mass of methanol ) A solution prepared by dissolving 388 parts by mass of propane in 400 parts by mass of acetone was dropped, and then heated to reflux temperature and stirred for 2 hours. After completion of the reaction, the reaction mixture was cooled to room temperature and washed with toluene and water. The organic phase was separated and the treene was distilled off under reduced pressure, followed by purification, followed by purification with 176 parts by mass (yield 40%) of white crystals. An exemplary compound 4-1 was obtained.

(Production of film)
<Film F-5>
Cellulose acylate C-5 100 parts by mass, stabilizer A-1 0.5 part by mass, ultraviolet absorber TINUVIN 928 (manufactured by Ciba Specialty Chemicals) 1.0 part by mass, matting agent Aerosil R972V 0 .3 parts by mass was mixed, and then 15 parts by mass of the exemplified compound 2-1 was added and mixed as a plasticizer, followed by drying under reduced pressure at 60 ° C. for 5 hours. This cellulose acylate composition was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized. At this time, an all screw type screw was used instead of a kneading disk in order to suppress heat generation due to shear during kneading. In addition, evacuation was performed from the vent hole, and volatile components generated during kneading were removed by suction. The space between the feeder and hopper supplied to the extruder, the extruder die and the cooling tank was a dry nitrogen gas atmosphere to prevent moisture from being absorbed into the resin.

  Film formation was performed with the manufacturing apparatus shown in FIG.

  The first cooling roll and the second cooling roll were made of stainless steel having a diameter of 40 cm, and the surface was hard chrome plated. Further, oil for temperature adjustment was circulated inside to control the roll surface temperature. The elastic touch roll had a diameter of 20 cm, the inner cylinder and the outer cylinder were made of stainless steel, and the surface of the outer cylinder was hard chrome plated. The wall thickness of the outer cylinder was 2 mm, and the surface temperature of the elastic touch roll was controlled by circulating oil for temperature adjustment in the space between the inner cylinder and the outer cylinder.

  The obtained pellet (moisture content 50 ppm) was melt-extruded into a film at a film-forming temperature of 240 ° C. on a first cooling roll having a surface temperature of 130 ° C. from a T die using a single-screw extruder, and a draw ratio of 20 A cast film was obtained. At this time, a T die having a lip clearance of 1.5 mm and an average surface roughness Ra of 0.01 μm was used.

Further, an elastic touch roll having a metal surface with a thickness of 2 mm was pressed on the first cooling roll at a linear pressure of 10 kg / cm. The film temperature on the touch roll side during pressing was 180 ° C. ± 1 ° C. (The film temperature on the touch roll side at the time of pressing here refers to the temperature of the film at the position where the touch roll on the first roll (cooling roll) is in contact with the non-contact thermometer by retreating the touch roll. (The average value of the film surface temperature measured 10 points in the width direction from a position 50 cm away without a roll.) The glass transition temperature Tg of this film was 136 ° C. (The glass transition temperature of the film extruded from the die was measured by DSC method (in nitrogen, temperature rising temperature 10 ° C./min) using DSC6200 manufactured by Seiko Co., Ltd.)
The surface temperature of the elastic touch roll was 130 ° C., and the surface temperature of the second cooling roll was 100 ° C. The surface temperature of each roll of the elastic touch roll, the first cooling roll, and the second cooling roll is determined by measuring the temperature of the roll surface at a position 90 ° before the rotation direction from the position where the film first contacts the roll. The average value obtained by measuring 10 points in the width direction using was used as the surface temperature of each roll.

  The obtained film was heated at 160 ° C. and stretched by 1.05 times in the longitudinal direction by roll stretching, followed by a preheating zone, a stretching zone, a holding zone, a cooling zone (between each zone, insulation between each zone was insulated). It also has a neutral zone to ensure) and is stretched 1.20 times at 160 ° C in the width direction, then cooled to 70 ° C while relaxing 2% in the width direction, and then released from the clip. Then, the clip holding part is cut off, the film is subjected to a knurling process with a width of 10 mm and a height of 5 μm at both ends of the film, and a film thickness of 80 μm slit to a width of 1430 mm, Ro is 4 nm, and Rt is 45 nm. Produced. At this time, the preheating temperature and the holding temperature were adjusted to prevent the bowing phenomenon due to stretching.

[Films F-1 to F-4, F-6 to F-41]
In the production of the film F-5, the type of cellulose acylate, the type of plasticizer, the type of stabilizer-1 to the type of stabilizer-3, and the film forming temperature were changed as shown in Table 3, and further an elastic touch roll Films F-1 to F-4 and F-6 to F-41 were produced in the same manner except that the presence or absence of was used as described in Table 3. In Table 3, the amount of stabilizer-1 added was 0.5 parts by mass, the amount of stabilizer-2 added was 0.25 parts by mass, and the amount of stabilizer-3 added was 0.25 parts by mass. Further, in the production of each film, the extrusion amount and the take-up speed were appropriately adjusted so that the film thickness was 80 μm.

(Plasticizer)
TPP: Triphenyl phosphate (Aldrich)
TMPTB: Trimethylolpropane tribenzoate PETB: Pentaerythritol tetrabenzoate (Aldrich)
(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)
A-5. PEP-36 (Asahi Denka)
A-6. HP-136 (Ciba Specialty Chemicals)
A-7. GSY-P101 (manufactured by API Corporation)
(Alkaline saponification treatment of sample)
As a saponification treatment of the produced film, saponification, water washing, neutralization, and water washing were sequentially performed under the following conditions, and after drying at 80 ° C., a saponified film was produced.
Saponification process 2 mol / L sodium hydroxide 50 ° C. 90 seconds water washing process Water 30 ° C. 45 seconds neutralization process 10% by mass hydrochloric acid 30 ° C. 45 seconds water washing process Water (Evaluation)
As film evaluation, film mechanical strength, saponification properties, and film melt film-forming properties were evaluated.

(Film mechanical strength)
Using a mechanical strength tester Tensilon, the elongation at break in the film forming direction of the film in an environment of 23 ° C. and 50% RH was measured. In the evaluation, the elongation at break was less than 10%, Δ was 10% or more and less than 20%, Δ was 20% or more and less than 30%, and ◎ was 30% or more.

(Saponification)
As a saponification property, the static contact angle with water on the film surface after saponification was measured. The static contact angle was measured by the θ / 2 method using an automatic surface tension meter (CA-V manufactured by Kyowa Interface Science Co., Ltd.), and the evaluation value was an average value measured five times in the width direction. In the evaluation, the static contact angle was evaluated as ◎ when less than 35 °, ◯ when 35 ° or more and less than 45 °, Δ when 45 ° or more and less than 50 °, and × when 50 ° or more.

(Film melt film forming)
The film length and width were measured at 10 points every 5 cm, and the standard deviation of the film thickness was calculated. In the evaluation, the standard deviation is less than 2 μm, ◎ is 2 μm or more and less than 5 μm, ◯ is 5 μm or more and less than 10 μm, and Δ is 10 μm or more.

(Moisture permeability measurement)
The moisture permeability was measured according to the method of JIS Z0208. The measurement condition is 40 ° C. and 90% RH.
500 g / m less than ^{2 / day ◎, 500g / m} 2 / day or more 600 g / m less than ^{2 / day ○, 600g / m} 2 / day or more 700 g / m less than ^{2 / day △, 700g / m} 2 / day The above was set as x.

(Bleed-out evaluation)
After adjusting the humidity at 23 ° C. and 55% RH, the film was subjected to a wiping test using a waste cloth and a smear test using oil-based ink. The film surface that can be wiped with a waste cloth was marked with x, the film was recorded with a suitable line with oil-based ink, and the film with blurring was marked with x. When weak wiping marks or blurs were observed in either evaluation, it was judged as Δ.

(YI measurement)
Using a spectrophotometer U-3310 manufactured by Hitachi High-Technologies Corporation, the absorption spectrum of the obtained cellulose ester film was measured, and tristimulus values X, Y, and Z were calculated. From these tristimulus values X, Y, and Z, yellowness YI was calculated based on JIS-K7103.
Less than 1.0 was evaluated as ◎, 1.0 or more and less than 2.0 as ◯, 2.0 or more and less than 4.0 as Δ, and 4.0 or more as x.

(Flatness evaluation)
A sample at the time when 1 hour has elapsed after the start of melt film formation was taken, and a sample having a length of 100 cm and a width of 40 cm was cut out.

Paste black paper on a flat desk, place the above sample film on it, project the three fluorescent lamps placed diagonally above onto the film, and evaluate the flatness by the degree of bending of the fluorescent lamp. Ranked by criteria.
◎: All three fluorescent lamps appear straight ○: Some fluorescent lamps appear to be bent slightly △: Fluorescent lamps appear bent X: A fluorescent lamp appears to swell greatly.

(Horseback failure)
The evaluation is made by winding the cellulose ester film 120 on the core body 110 and then wrapping the outer surface twice with a polyethylene sheet, and setting it on the support plate 117 on the pedestal 118 by the storage method as shown in FIG. And after storing in a box, it preserve | saved for 30 days on 25 degreeC and 50% of conditions. Then, take out the box, open the polyethylene sheet, reflect the reflected fluorescent lamp tube on the surface of the cellulose ester film 120, observe the distortion or fine disturbance, and make the horse's back failure resistance according to the following criteria evaluated.
◎: Fluorescent lamps appear straight ○: Fluorescent lamps appear to be slightly bent △: Fluorescent lamps appear to be partially bent ×: Fluorescent lamps appear to be reflected in mottle

(Preparation of polarizing plate)
Next, the produced cellulose acylate films F1 to F41 were subjected to the following alkali saponification treatment to produce polarizing plates 1 to 41, respectively.

(Alkaline saponification treatment)
Saponification process 2 mol / L NaOH 50 ° C. 90 seconds Water washing process Water 30 ° C. 45 seconds Neutralization process 10% HCl 30 ° C. 45 seconds Water washing process Water 30 ° C. 45 seconds After saponification treatment, water washing, neutralization and water washing are performed in this order. And then dried at 80 ° C.

(Production of polarizer)
A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 6 times at 50 ° C. to produce a polarizer.

  The above prepared cellulose acylate film is bonded to both sides of the polarizer from both sides with the alkali saponification treated surface as the polarizer side and a 5% by mass aqueous solution of completely saponified polyvinyl alcohol as an adhesive, and a protective film for polarizing plate is applied. Combined polarizing plates 1 to 41 were produced.

(Characteristic evaluation as a liquid crystal display device)
The polarizing plate of 32 type TFT type color liquid crystal display Vega (manufactured by Sony Corporation) was peeled off, and each polarizing plate produced above was cut according to the size of the liquid crystal cell. A liquid crystal cell is sandwiched, and the two polarizing plates thus prepared are pasted so as to be orthogonal to each other so that the polarizing axis of the polarizing plate does not change from the original, to produce a 32-type TFT color liquid crystal display, and a cellulose acylate film When the characteristics as a polarizing plate were evaluated, the polarizing plate produced from the cellulose acylate film 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 an image display device such as a liquid crystal display.

It is a general | schematic flow sheet which shows one Embodiment of the apparatus which enforces the manufacturing method of the optical film of this invention. It is a principal part expansion flow sheet of the manufacturing apparatus of FIG. 3A is an external view of the main part of the casting die, and FIG. 3B is a cross-sectional view of the main part of the casting die. It is sectional drawing of 1st Embodiment of a pinching rotary body. It is sectional drawing in the plane perpendicular | vertical to the rotating shaft of 2nd Embodiment of a pinching rotary body. It is sectional drawing in the plane containing the rotating shaft of 2nd Embodiment of a pinching rotary body. It is a disassembled perspective view which shows the outline of the block diagram of a liquid crystal display device. It is a figure which shows the state of the storage of a cellulose-ester film original fabric.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Cellulose acylate film 16 Winding device 21a, 21b Protective film 22a, 22b Phase difference film 23a, 23b Film slow axis direction 24a, 24b Polarizer transmission axis direction 25a , 25b Polarizers 26a, 26b Polarizing plate 27 Liquid crystal cell 29 Liquid crystal display device 31 Die body 32 Slit 41 Metal sleeve 42 Elastic roller 43 Metal inner cylinder 44 Rubber 45 Cooling water 51 Outer cylinder 52 Inner cylinder 53 Space 54 Coolant 55a , 55b Rotating shaft 56a, 56b Outer cylinder support flange 60 Fluid shaft cylinder 61a, 61b Inner cylinder support flange 62a, 62b Intermediate passage 110 Core body 117 Support plate 118 Base 120 Cellulose ester film original fabric

Claims (7)

A method for producing a cellulose acylate film formed by a melt casting method, wherein the cellulose acylate film contains at least one compound represented by the following general formula (1), and is melt cast A method for producing a cellulose acylate film, wherein the cellulose acylate film extruded from a casting die at the time of film formation is produced by pressing with a touch roll and a cooling roll whose surface can be elastically deformed.
General formula (1)
A- (X-B) _n
(In the formula, A represents an alkyl group, X represents a divalent linking group selected from the group consisting of —NHCO—, —NHSO ₂ —, —O—, or —SO ₂ —, and B represents an aromatic group. And n represents 3 or 4, and a plurality of X-Bs may be the same or different.) 2. The cellulose according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2), general formula (3), or general formula (4). A method for producing an acylate film.

(In the formula, X represents a divalent linking group selected from the group consisting of —NHCO—, —NHSO ₂ —, —O—, or —SO ₂ —, and R ^{1 to} R ²⁰ each independently represents a hydrogen atom. Represents a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group, which further has a substituent. R ²¹ represents an alkyl group.) The cellulose acylate used in the method for producing a cellulose acylate film has an acyl group total carbon number of 6.2 or more and 7.5 or less, and the cellulose acylate film according to claim 1 or 2, Production method.
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. A cellulose acylate film produced by the method for producing a cellulose acylate film according to claim 1. The cellulose acylate film according to claim 4, wherein the cellulose acylate film contains at least one selected from a hindered phenol-based antioxidant, a phosphorus-based antioxidant, and a carbon radical scavenger. A polarizing plate comprising the cellulose acylate film according to claim 4 as a protective film for a polarizing plate. A liquid crystal display device using the polarizing plate according to claim 6.

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