JP2007168419A - Cellulose ester film and its manufacturing process, polarizing plate, optical compensation film, anti-reflective film, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film and a manufacturing process thereof which can improve the image unevenness in a display screen and change of visibility with passage of time which are generated when it is incorporated in a liquid crystal display, a polarizing plate, an optical compensation film, an anti-reflective film, and a liquid crystal display. <P>SOLUTION: A mixture comprising 100 mass parts of cellulose ester having a specific degree of substitution, 0.02-3 mass parts of phenol-based stabilizer having a molecular weight of 500 or more and 0.02-3 mass% of phosphite-based stabilizer or thioether based stabilizer having a molecular weight of 500 or more is melted at 180-240°C, extruded from a die and the cellulose ester film of 20 μm to 300 μm of thickness is formed into a film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a cellulose ester film by melt film formation. The present invention also relates to a cellulose ester film excellent in optical properties. Furthermore, the present invention also relates to a polarizing plate, an optical compensation film, an antireflection film and a liquid crystal display device using the cellulose ester film.

  Conventionally, when manufacturing a cellulose ester film used in a liquid crystal display device, a cellulose ester is dissolved in a chlorinated organic solvent such as dichloromethane, and the solution is cast on a substrate and dried to form a film. The casting method is mainly implemented. Among chlorinated organic solvents, dichloromethane is preferably used because it is a good solvent for cellulose esters, has a low boiling point (about 40 ° C.), and can be easily dried in a film forming process or a drying process. On the other hand, in recent years, it has been strongly demanded to suppress discharge of organic solvents such as chlorinated organic solvents from the viewpoint of environmental conservation. For this reason, a more strict closed system is adopted to prevent the organic solvent from leaking from the manufacturing process, or even if the organic solvent leaks from the film forming process, the organic solvent is adsorbed through the gas absorption tower before it is released to the outside air. Measures are taken so that the organic solvent is hardly discharged by performing a process such as burning with thermal power or decomposing with an electron beam. However, even if these measures were taken, further non-emission was not achieved, so further improvement was required.

Therefore, as a film forming method that does not use an organic solvent, a method of melt-forming cellulose ester has been developed (see, for example, Patent Documents 1 and 2). In this method, the melting point is lowered to facilitate film formation by elongating the carbon chain of the ester group of the cellulose ester. Specifically, melt film formation is enabled by changing the cellulose acetate used conventionally to cellulose propionate, cellulose butyrate, or the like. The cellulose ester film thus obtained has an advantage that it can provide a retardation film and the like in which the visual field characteristics are not easily changed due to a change in humidity when used as a substrate. Furthermore, after melt | dissolving a cellulose ester using the screw of compression ratio 3-15 at the temperature of 180-250 degreeC as a manufacturing method of the cellulose-ester film including the process of melt | dissolving a cellulose ester, and the process of casting, T -A method for producing a cellulose ester film characterized by being extruded from a die onto a casting drum has also been developed (Patent Document 3). It is described that the cellulose ester film produced by this method can reduce visibility change due to display unevenness and humidity by being incorporated in a liquid crystal display device.
Japanese National Patent Publication No. 6-501040 JP 2000-352620 A JP 2005-178194 A

  However, when the cellulose ester film melt-formed by these methods is carried out according to the examples, it is difficult to suppress the coloring and surface state of the cellulose ester film, and further the coloring during handling to a satisfactory level. It turned out that. Specifically, the present inventors have revealed that coloring resistance and film strength in the pelletizing process or melt film forming process are insufficient. In particular, the film produced according to the example of Patent Document 2 is markedly deteriorated in coloration and surface condition at the time of melt film formation, accompanied by deterioration in weather resistance over time, and its improvement was urgent.

  In addition, when a polarizing plate is produced using a cellulose ester film produced according to the above-mentioned patent document and incorporated in a liquid crystal display device, problems such as poor surface condition, luminance reduction due to coloring or haze increase, and the like need to be improved. It became clear that it was the level. Such a failure is particularly significant when the polarizing plate is incorporated into a large-sized liquid crystal display panel of 15 inches or more, and has been a big problem. These problems are caused by a series of film forming processes in which a melt is extruded from a melt kneader (pelletizing) through a T-die (slit) onto a casting drum, cooled and solidified to form a film, and further processed. It has also been clarified that the coloration becomes stronger due to the high temperature during the pelletization step and / or melt film formation.

  In view of these problems of the prior art, the present invention provides a cellulose ester film capable of improving image unevenness on a display screen generated when incorporated in a liquid crystal display device and change in visibility over time, and production thereof. It aims to provide a method. Another object of the present invention is to provide a cellulose ester film by an environmentally friendly manufacturing method that does not use an organic solvent. In particular, an object of the present invention is to provide a cellulose ester having strong weather resistance that is useful as a protective film for a polarizing plate or a retardation film and that can prevent coloring and the like.

The above object has been achieved by the present invention having the following constitution.
(Aspect 1)
Cellulose ester satisfying the following formulas (S-1) to (S-3) and at least one phenol-based stabilizer having a molecular weight of 500 or more are 0.02 to 3% by mass with respect to the cellulose ester, and the molecular weight is Cellulose ester mixture containing at least one selected from the group consisting of phosphite ester stabilizers having a molecular weight of 500 or more and thioether stabilizers having a molecular weight of 500 or more with respect to the cellulose ester A method for producing a cellulose ester film, comprising a melt film-forming step in which a cellulose ester film having a film thickness of 20 μm to 300 μm is formed by melting at a temperature of 180 to 240 ° C. and extruding from a die.
Formula (S-1) 2.5 <= A + B <= 3.0
Formula (S-2) 0 ≦ A ≦ 2.2
Formula (S-3) 0.8 ≦ B ≦ 3.0
(In the formula, A represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and B represents the total degree of substitution of the acyl group having 3 to 22 carbon atoms with respect to the hydroxyl group of cellulose.)

(Aspect 2)
The method for producing a cellulose ester film according to aspect 1, wherein the pelletized cellulose ester mixture is melted at 180 to 240 ° C and extruded from a die.
(Aspect 3)
The method for producing a cellulose ester film according to aspect 2, wherein the pelletized cellulose ester mixture is prepared by melting the cellulose ester mixture at 180 to 240 ° C to form a pellet.
(Aspect 4)
The method for producing a cellulose ester film according to aspect 3, wherein the pelletization is performed at an oxygen concentration of 5% or less.

(Aspect 5)
A compound having a mass loss of 20% by mass or less when heated at 220 ° C. in nitrogen for 30 minutes is used as the phenol stabilizer, and the phosphite stabilizer or the thioether stabilizer The production of the cellulose ester film according to any one of embodiments 1 to 4, wherein a compound having a mass reduction amount of 20% by mass or less when heated at 220 ° C. for 30 minutes in nitrogen is used. Method.
(Aspect 6)
The molecular weight of the phenol-based stabilizer is 550 or more, and the molecular weight of the phosphite-based stabilizer or the thioether-based stabilizer is 550 or more. The manufacturing method of the cellulose-ester film of description.
(Aspect 7)
Any one of the aspects 1 to 6, wherein the acyl group of B substituted on the hydroxyl group of cellulose in the cellulose ester is one or more acyl groups selected from a propionyl group and a butyryl group. The manufacturing method of the cellulose-ester film of description.
(Aspect 8)
The method for producing a cellulose ester film according to any one of aspects 1 to 7, wherein the cellulose ester mixture contains fine particles having an average primary particle size of 20 nm to 2 µm.
(Aspect 9)
The cellulose ester film formed by the melt film-forming step further includes a stretching step of stretching 0.3 to 3 times in at least one direction, according to any one of aspects 1 to 8, A method for producing a cellulose ester film.
(Aspect 10)
The method for producing a cellulose ester film according to any one of aspects 1 to 9, wherein an oxygen concentration during pelletization and / or melt film formation is 5% by volume or less.

(Aspect 11)
In the melt film-forming step, the melt-extruded molten cellulose ester (melt) is solidified on a casting drum, the cellulose ester film formed on the casting drum is peeled off, and tension-cut with a nip roll and wound up. The manufacturing method of the cellulose-ester film as described in any one of aspect 1-10 made.
(Aspect 12)
The method for producing a cellulose ester film described in aspect 11, characterized by winding the cellulose ester film tension during the winding as ^{0.01kg / cm 2 ~10kg / cm 2} .

(Aspect 13)
When the molten mixture is solidified on a casting drum, cooling is performed at a temperature between (Tg + 30 ° C.) and Tg (where Tg indicates the glass transition temperature of the cellulose ester film). The method for producing a cellulose ester film according to the aspect 11 or 12, wherein the method is carried out at a speed of (solidification speed).

(Aspect 14)
The cellulose ester satisfying the formulas (S-1) to (S-3) and the phenolic stabilizer having a molecular weight of 500 or more are 0.02 to 3% by mass with respect to the cellulose ester, and the molecular weight is At least one selected from the group consisting of a phosphite stabilizer having a molecular weight of 500 or more and a thioether stabilizer having a molecular weight of 500 or more is used at 180 ° C. to 240 ° C. using a kneading screw having a compression ratio of 2-15. After melting, the cellulose ester film according to any one of aspects 1 to 13, further comprising a step of extruding into water at 20 to 95 ° C from a nozzle and cooling, further cutting and pelletizing. Production method.

(Aspect 15)
In the melt film forming step, the cellulose ester mixture is melted at 180 ° C. to 240 ° C. using a kneading screw having a compression ratio of 2 to 15, and then extruded from a die onto a casting drum. The manufacturing method of the cellulose-ester film as described in any one of these.
(Aspect 16)
A mode 15 in which the molten cellulose ester is extruded from a die and then cooled at a temperature between Tg and (Tg−20 ° C.) at a rate of 0.1 ° C./second to 20 ° C./second. Of manufacturing cellulose ester film.

(Aspect 17)
The cellulose-ester film manufactured by the manufacturing method as described in any one of aspect 1-16.
(Aspect 18)
Cellulose ester satisfying the following formulas (S-1) to (S-3) and at least one phenol-based stabilizer having a molecular weight of 500 or more are 0.02 to 3% by mass with respect to the cellulose ester, and the molecular weight is Containing at least one selected from the group consisting of a phosphite ester stabilizer having a molecular weight of 500 or more and a thioether stabilizer having a molecular weight of 500 or more with respect to the cellulose ester, and having a film thickness 20 μm to 300 μm, the residual solvent amount is 0.01% by mass or less, and both the front retardation (Re) unevenness and the thickness direction retardation (Rth) unevenness are less than 3.0 nm. Cellulose ester film.
Formula (S-1) 2.5 <= A + B <= 3.0
Formula (S-2) 0 ≦ A ≦ 2.2
Formula (S-3) 0.8 ≦ B ≦ 3.0
(In the formula, A represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and B represents the total degree of substitution of the acyl group having 3 to 22 carbon atoms with respect to the hydroxyl group of cellulose.)

(Aspect 19)
For the absorbance at 400 nm measured by preparing a 2% by mass methylene chloride solution of the cellulose ester film, the cellulose ester film was heated in air at 240 ° C. for 1 hour, and then a 2% by mass methylene chloride solution was prepared. The cellulose ester film according to the aspect 17 or 18, wherein an increase in absorbance at 400 nm measured by the method is 0.05 or less.
(Aspect 20)
The front retardation (Re) is 0 to 300 nm, and the absolute value of retardation (Rth) in the thickness direction is 0 to 700 nm. Cellulose ester film.
(Aspect 21)
The cellulose ester film according to any one of aspects 17 to 20, wherein the visible light transmittance is 90% or more and the haze is 0.01 to 1.2%.
(Aspect 22)
The cellulose ester film according to any one of aspects 17 to 21, wherein the following formulas (A-1) and (A-2) are satisfied.
Formula (A-1) 0 ≦ | Re (700) −Re (400) | ≦ 15 nm
Formula (A-2) 0 ≦ | Rth (700) −Rth (400) | ≦ 35 nm
(In the formula, Re (400) and Re (700) represent the front retardation (Re) at wavelengths of 400 nm and 700 nm of the cellulose ester film, and Rth (400) and Rth (700) represent the cellulose ester film. Represents retardation in the thickness direction (Rth) at wavelengths of 400 nm and 700 nm.)
(Aspect 23)
23. The cellulose ester film according to any one of aspects 17 to 22, wherein a contact angle of water on the film surface (25 ° C., relative humidity 60%) is 45 ° or less.
(Aspect 24)
The cellulose ester film according to any one of aspects 17 to 23, comprising fine particles having an average primary particle size of 20 nm to 2 μm.
(Aspect 25)
The cellulose ester film according to any one of embodiments 17 to 24, wherein a plasticizer having a molecular weight of 500 or more is contained in an amount of 1 to 20% by mass based on the cellulose ester.

(Aspect 26)
The cellulose ester film according to any one of aspects 17 to 25, wherein the thickness unevenness is 0 to 5 μm.

(Aspect 27)
The cellulose ester film according to any one of aspects 17 to 26, wherein the cellulose ester satisfies the following formulas (S-4) to (S-6).
Formula (S-4) 2.6 ≦ Aa + Bb ≦ 3.0
Formula (S-5) 0 ≦ Aa ≦ 2.2
Formula (S-6) 0.8 <= Bb <= 3.0
(In the formula, Aa represents the substitution degree of the acetyl group to the hydroxyl group of cellulose, and Bb represents the total substitution degree of the propionyl group or butyryl group to the hydroxyl group of cellulose.)

(Aspect 28)
A polarizing plate comprising at least one layer of the cellulose ester film according to any one of aspects 17 to 27 laminated on a polarizing film.
(Aspect 29)
29. The polarizing plate according to aspect 28, wherein the polarizing film is tenter-stretched in a direction substantially 45 ° with respect to the longitudinal direction.

(Aspect 30)
An optical compensation film, wherein the cellulose ester film according to any one of aspects 17 to 29 is used as a substrate.
(Aspect 31)
An antireflection film comprising the cellulose ester film according to any one of aspects 17 to 29 as a substrate.

(Aspect 32)
30. A liquid crystal display device comprising at least one of the polarizing plate according to aspect 28 or 29, the optical compensation film according to aspect 30, and the antireflection film according to aspect 31.

  According to the present invention, the handling property during the production of cellulose ester is improved, the surface shape is greatly improved, and the image unevenness on the display screen generated when incorporated in a liquid crystal display device and the visibility over time are improved. A cellulose ester film with improved changes can be provided. Moreover, the cellulose-ester film formed into a film by the environmentally friendly manufacturing method can be provided without using an organic solvent at the time of manufacture. With the cellulose ester film of the present invention, it is possible to provide a film for optical use having excellent weather resistance over time, particularly excellent durability under a high temperature environment. In the liquid crystal display device manufactured by incorporating the cellulose ester film of the present invention, display unevenness, changes in optical characteristics due to humidity or image color are suppressed.

  Hereinafter, the cellulose ester film of the present invention, the production method thereof, and the cellulose ester film and the use thereof will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

《Cellulose ester》
First, the cellulose ester used in the present invention will be described. The cellulose ester used in the present invention satisfies the following formulas (S-1) to (S-3).
Formula (S-1) 2.5 <= A + B <= 3.0
Formula (S-2) 0 ≦ A ≦ 2.2
Formula (S-3) 0.8 ≦ B ≦ 3.0

  In the formula, A represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and B represents the sum of the degree of substitution of the acyl group having 3 to 22 carbon atoms with respect to the hydroxyl group of cellulose. The “degree of substitution” in the present specification means the total of the ratio of substitution of hydrogen atoms of hydroxyl groups at the 2-position, 3-position and 6-position of cellulose. When the hydrogen atoms of all hydroxyl groups at the 2nd, 3rd and 6th positions are substituted with acyl groups, the degree of substitution is 3. The C3-C22 acyl group represented by the substituent B of the cellulose ester of the present invention may be either an aliphatic acyl group or an aromatic acyl group. When the acyl group of the cellulose ester of the present invention is an aliphatic acyl group, the number of carbon atoms is preferably 3-18, more preferably 3-12, and the number of carbons is 3-8. It is particularly preferred. Examples of these aliphatic acyl groups include an alkylcarbonyl group, an alkenylcarbonyl group, and an alkynylcarbonyl group. When the acyl group is an aromatic acyl group, the carbon number is preferably 6-22, more preferably 6-18, and particularly preferably 6-12. Each of these acyl groups may further have a substituent.

  Examples of preferred acyl groups include propionyl, butyryl, pentanoyl, hexanoyl, heptanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, Examples thereof include an isobutyryl group, a pivaloyl group, a cyclohexanecarbonyl group, an oleoyl group, a benzoyl group, a naphthalenecarbonyl group, a phthaloyl group, and a cinnamoyl group. Among these, more preferred are propionyl, butyryl, dodecanoyl, octadecanoyl, pivaloyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like.

  In particular, the acyl group represented by B is preferably an aliphatic acyl group having 3 to 6 carbon atoms, and is preferably an acyl group selected from the group consisting of a propionyl group, a butyryl group, a pentanoyl group and a hexanoyl group. More preferable B is an acyl group selected from the group consisting of a propionyl group and a butyryl group. The acyl group represented by B constituting the ester of the cellulose ester of the present invention may be a single species or a plurality of species. In the present invention, the substitution degree distribution of hydroxyl groups at the 2-position, 3-position and 6-position of cellulose is not particularly limited.

In the present invention, it is preferable to use a cellulose ester that satisfies the following formulas (S-4) to (S-6).
Formula (S-4) 2.6 ≦ Aa + Bb ≦ 3.0
Formula (S-5) 0 ≦ Aa ≦ 2.2
Formula (S-6) 0.8 <= Bb <= 3.0
In the present invention, it is particularly preferable to use a cellulose ester that satisfies the following formulas (S-7) to (S-9).
Formula (S-7) 2.65 ≦ Aa + Bb ≦ 2.97
Formula (S-8) 0.2 <= Aa <= 2.2
Formula (S-9) 0.8 ≦ Bb ≦ 3.0
(In the formula, Aa represents the substitution degree of the acetyl group to the hydroxyl group of cellulose, and Bb represents the total substitution degree of the propionyl group or butyryl group to the hydroxyl group of cellulose.)

(Method for producing cellulose ester)
Next, the manufacturing method of the cellulose ester used by this invention is demonstrated. As for the raw material cotton and the synthesis method of the cellulose ester of the present invention, the description on pages 7 to 12 of the Japan Society of Invention Public Technical Report (Public Technical Number 2001-1745, issued on March 15, 2001, Japan Society of Invention) can also be applied. In addition, the addition amount here is the mass% with respect to a cellulose ester.

  The cellulose raw material to be used is not particularly limited, but those derived from hardwood pulp, softwood pulp, and cotton linter are preferably used. The cellulose raw material is preferably subjected to a treatment (activation) for contacting with an activator prior to acylation. As the activator, acetic acid, propionic acid, or butyric acid is preferable, and acetic acid is particularly preferable. The addition amount of the activator is usually 5 to 10000% by mass, more preferably 10 to 2000% by mass, and further preferably 30 to 100% by mass with respect to the cellulose raw material. The addition method can be selected from methods such as spraying, dripping and dipping. The activation time is preferably 20 minutes to 72 hours, particularly preferably 20 minutes to 12 hours. The activation temperature is preferably 0 ° C to 90 ° C, particularly preferably 20 ° C to 60 ° C. Furthermore, 0.1 mass%-10 mass% of acylation catalysts, such as a sulfuric acid, can also be added to an activator.

  The acylation of cellulose is preferably carried out by reacting cellulose and a carboxylic acid anhydride using a Bronsted acid or a Lewis acid (see “Science and Chemistry Dictionary”, fifth edition (2000)) as a catalyst. As a method for obtaining a cellulose ester, a method of reacting two carboxylic acid anhydrides as an acylating agent by mixing or sequentially adding them, a mixed acid anhydride of two carboxylic acids (for example, acetic acid / propionic acid mixed acid anhydride) ), A mixed acid anhydride (for example, acetic acid / propionic acid mixed acid anhydride) in a reaction system using a carboxylic acid and an acid anhydride of another carboxylic acid (for example, acetic acid and propionic acid anhydride) as a raw material. A method of forming and reacting with cellulose, a method of once synthesizing a cellulose ester having a substitution degree of less than 3, and a method of further acylating the remaining hydroxyl group with an acid anhydride or acid halide can be used. The synthesis of a cellulose ester having a high degree of substitution with respect to the 6-position hydroxyl group is described in publications such as JP-A Nos. 11-5851, 2002-212338, and 2002-338601.

  Preferred as the carboxylic acid anhydride is a carboxylic acid having 2 to 7 carbon atoms. Particularly preferred are acetic anhydride, propionic anhydride, and butyric anhydride. The acid anhydride is preferably added in an amount of 1.1 to 50 equivalents, more preferably 1.2 to 30 equivalents, and particularly preferably 1.5 to 10 equivalents based on the hydroxyl group of cellulose. The acylation catalyst is preferably a Bronsted acid or a Lewis acid, more preferably sulfuric acid or perchloric acid, and a preferred addition amount is 0.1 to 30% by mass, more preferably 1 to 15% by mass. And particularly preferably 3 to 12% by mass.

  The acylating solvent is preferably a carboxylic acid, more preferably a carboxylic acid having 2 to 7 carbon atoms, and particularly preferably acetic acid, propionic acid, or butyric acid. These solvents may be used as a mixture. As the acylation conditions, it is preferable to cool the acylating agent in advance in order to control the temperature rise due to the heat of reaction of acylation. The acylation temperature is preferably -50 ° C to 50 ° C, more preferably -30 ° C to 40 ° C, particularly preferably -20 ° C to 35 ° C. The minimum reaction temperature is preferably −50 ° C. or higher, more preferably −30 ° C. or higher, and particularly preferably −20 ° C. or higher. The acylation time is preferably 0.5 hours to 24 hours, more preferably 1 hour to 12 hours, and particularly preferably 1.5 hours to 10 hours.

  It is preferable to add a reaction terminator after the acylation reaction. The reaction terminator is not particularly limited as long as it decomposes acid anhydrides, and examples thereof include water, alcohol (having 1 to 3 carbon atoms), and carboxylic acids (acetic acid, propionic acid, butyric acid, etc.). Among them, water and carboxylic acid ( A mixture with acetic acid) is preferred. The composition of water and carboxylic acid is preferably 5 to 80% by mass, more preferably 10 to 60% by mass, and particularly preferably 15 to 50% by mass of water. A neutralizing agent may be added after the acylation reaction is stopped. Preferred examples of the neutralizing agent include ammonium, organic quaternary ammonium, alkali metal, group 2 metal, group 3-12 metal, or group 13-15 element carbonate, bicarbonate, organic acid salt, water An oxide or an oxide can be given. Particularly preferred are sodium, potassium, magnesium or calcium carbonates, bicarbonates, acetates or hydroxides.

  The cellulose ester thus obtained has a total degree of substitution (total of the degree of substitution with respect to the hydroxyl groups at the 2nd, 3rd and 6th positions of the cellulose) close to 3, but the desired degree of substitution. For the purpose of obtaining an ester bond, the ester bond is partially hydrolyzed by keeping it at 20 to 90 ° C. for several minutes to several days in the presence of a small amount of catalyst (generally an acylation catalyst such as residual sulfuric acid) and water. The acyl substitution degree of the cellulose ester can be reduced to a desired level. Thereafter, partial hydrolysis of the remaining catalyst can be stopped using the neutralizing agent.

(Filtration)
Filtration may be performed in any step from completion of acylation to reprecipitation. It is also preferred to dilute with a suitable solvent prior to filtration. The cellulose ester solution is mixed with water or an aqueous solution of carboxylic acid (for example, acetic acid, propionic acid, etc.) and reprecipitated. Reprecipitation may be either continuous or batch. It is preferable to perform a washing treatment after reprecipitation. Washing uses water or warm water, and the completion of washing can be confirmed by pH, ion concentration, electrical conductivity, elemental analysis, and the like. The cellulose ester after washing is preferably added with a weak alkali (carbonates such as Na, K, Ca and Mg, bicarbonates, hydroxides and oxides) for stabilization.

(Dry)
In the present invention, in order to adjust the moisture content of the cellulose ester to a preferable amount, it is preferable to dry the cellulose ester. The drying method is not particularly limited as long as the desired moisture content can be obtained, but it is preferable to carry out it efficiently by using means such as heating, blowing, depressurization, stirring and the like alone or in combination. The drying temperature is preferably 0 to 200 ° C., more preferably 40 to 180 ° C., and particularly preferably 50 to 160 ° C. It is preferable to remove the moisture as dry air and blow. In addition, in order to fully dry, you may implement under a vacuum and the range of 1 Pa-0.05Mpa is preferable as a vacuum degree in that case. Under the present circumstances, it is preferable to dry at the temperature lower than the glass transition point (Tg) of a cellulose ester, and it is further more preferable to dry at the temperature below (Tg-10 degreeC). The cellulose ester obtained by drying preferably has a moisture content of 2% by mass or less, more preferably 0.7% by mass or less, more preferably 0.3% by mass or less, and It is particularly preferably 1% by mass or less.

  The shape of the cellulose ester is not particularly limited, but is preferably in the form of particles or powder. The cellulose ester after drying may be pulverized or sieved for uniform particle size and improved handling. When the cellulose ester is in the form of particles, 90% by mass or more of the particles used preferably have a particle size of 0.1 mm to 5 mm. Moreover, it is preferable that 50 mass% or more of the particle | grains to be used have a particle size of 0.2 mm-4 mm, and it is preferable that 50 mass% or more of the particle | grains to be used has a particle size of 0.2 mm-3 mm. The cellulose ester particles preferably have a shape as close to a sphere as possible.

(Degree of polymerization)
The average degree of polymerization of the cellulose ester preferably used in the present invention is 100 to 700, more preferably 120 to 500, still more preferably 120 to 350, and particularly preferably 130 to 300. The average degree of polymerization was determined by gel permeation chromatography (GPC) as described in Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). ) To measure the molecular weight distribution. Further details are described in JP-A-9-95538. These cellulose esters may use only 1 type and may mix 2 or more types. Such adjustment of the degree of polymerization can also be achieved by removing low molecular weight components. The removal of the low molecular component can be carried out by washing the cellulose ester with a suitable organic solvent. In addition, the cellulose ester in the present invention may be a mixture of polymer components other than cellulose ester as appropriate. 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.

  The cellulose ester used in the present invention preferably has a mass average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 1.5 to 5.0, and more preferably. The cellulose ester is preferably 1.5 to 4.5, more preferably 1.5 to 3.5. The obtained cellulose ester is preferably stored in a low-temperature dark place so that the storage is less affected by the environment. Furthermore, it is more preferable to store in a moisture-proof bag made of a prevention material such as aluminum, a SUS drum, or a container for storage.

  In addition, the synthesis of cellulose esters having a high degree of substitution with respect to the hydroxyl group at the 6-position is described in JP-A Nos. 11-5851, 2002-212338, 2002-338601, and the like. Other synthetic methods for cellulose esters include the presence of a base (sodium hydroxide, potassium hydroxide, barium hydroxide, sodium carbonate, pyridine, triethylamine, tert-butoxy potassium, sodium methoxide, sodium ethoxide, etc.) A method of reacting with carboxylic acid anhydride or carboxylic acid halide or a method using mixed acid anhydride (such as carboxylic acid / trifluoroacetic acid mixed anhydride, carboxylic acid / methanesulfonic acid mixed anhydride) as an acylating agent is also used. In particular, the latter method is effective when an acyl group having a large number of carbon atoms or an acyl group that is difficult to be subjected to liquid phase acylation using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst.

<Stabilizer>
(Phenolic stabilizer)
Next, the phenol stabilizer having a molecular weight of 500 or more added to the cellulose ester in the present invention will be described.
As the phenol stabilizer having a molecular weight of 500 or more, any known phenol stabilizer can be used. Preferable phenolic stabilizers include hindered phenolic stabilizers. In particular, it is preferable to have a substituent at a site adjacent to the hydroxyphenyl group. In this case, the substituent is preferably a substituted or unsubstituted alkyl group having 1 to 22 carbon atoms, such as a methyl group, an ethyl group, or a propionyl group. , Isopropionyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, tert-pentyl group, hexyl group, octyl group, isooctyl group, 2-ethylhexyl group, nonyl group, isononyl group, dodecyl Group, tert-dodecyl group, tridecyl group, tert-tridecyl group and the like. Among these, methyl group, ethyl group, propionyl group, isopropionyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, tert-pentyl group, hexyl group, octyl group, isooctyl group, 2- Ethylhexyl group is more preferred. More preferred are propionyl group, isopropionyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group and tert-pentyl group.
Specific examples of the phenol-based stabilizer include the following compounds, but the phenol-based stabilizer that can be used in the present invention is not limited to these specific examples.

(PH-1)
n-Octadecyl-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate (molecular weight 531)
(PH-2)
Tetrakis- [methylene-3- (3 ′, 5′-di-tert-butyl-4-hydroxyphenyl) propionate] methane (molecular weight 1178)
(PH-3)
Tris- (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate (molecular weight 784)
(PH-4)
Triethylene glycol-bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] (molecular weight 588)

(PH-5)
3,9-bis- {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxa Spiro [5.5] undecane (molecular weight 741)
(PH-6)
1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (molecular weight 775)
(PH-7)
1,1,3-tris (5-di-tert-butyl-4-hydroxy-2-methylphenyl) butane (molecular weight 545)

(PH-8)
1,6-hexanediol-bis {3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate} (molecular weight 639)
(PH-9)
2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine (molecular weight 589)
(PH-10)
1,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate] (molecular weight 643)

(PH-11)
N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide) (molecular weight 637)
(PH-12)
Bis (ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate) calcium (molecular weight 695)

  These materials are readily available as commercial products and are sold by the following manufacturers. From Ciba Specialty Chemicals, Irganox 1076, Irganox 1010, Irganox 3113, Irganox 245, Irganox 1135, Irganox 1330, Irganox 259, Irganx 565, Irganx 565, Irganx 565, Ir35x10 Moreover, it can obtain from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-20, ADK STAB AO-70, and ADK STAB AO-80. Furthermore, from Sumitomo Chemical Co., Ltd., it can obtain as Sumilizer BP-76, Sumilizer BP-101, Sumilizer GA-80. In addition, it is also possible to obtain as Sinox 326M and Sinox 336B from Sipro Kasei Co., Ltd.

(Phosphite stabilizer)
Next, a phosphite ester stabilizer having a molecular weight of 500 or more that can be added to the cellulose ester in the present invention will be described.
As a phosphite stabilizer having a molecular weight of 500 or more that can be used in the present invention, any conventionally known phosphite stabilizer can be used. Examples of the phosphite-based stabilizer that can be used in the present invention include compounds described in JP-A No. 2004-182979, [0023] to [0039]. Specific examples of the phosphite ester stabilizer include JP-A No. 51-70316, JP-A No. 10-306175, JP-A No. 57-78431, JP-A No. 54-157159, and JP-A No. 54-157159. The compounds described in JP-A-55-13765 can also be mentioned. Furthermore, as other stabilizers, the materials described in detail on pages 17 to 22 of the Japan Institute of Invention Information (Public Technical No. 2001-1745, issued on March 15, 2001, Japan Society of Inventions) may be mentioned. it can.

Since the phosphite ester stabilizer has a phenolic ester and can maintain stability at high temperatures, it is preferable that at least one substituent is an aromatic ester group. The phosphite ester stabilizer is preferably a triester, and is desirably free of impurities such as phosphoric acid, monoester and diester. When these impurities are present, the content is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly 2% by mass or less.
Preferred specific examples of the phosphite stabilizer include the following compounds, but the phosphite stabilizer that can be used in the present invention is not limited thereto.

(PF-1)
Trisnonyl phenyl phosphite (molecular weight 689)
(PF-2)
Tris (2,4-di-tert-butylphenyl) phosphite (molecular weight 647)
(PF-3)
Distearyl pentaerythritol diphosphite (molecular weight 733)
(PF-4)
Bis (2,4-di-tert-butylphenyl) pentaerythritol phosphite (molecular weight 605)

(PF-5)
Bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite (molecular weight 633)
(PF-6)
2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite (molecular weight 529)
(PF-7)
Tetrakis (2,4-di-tert-butylphenyl) -4,4-biphenylene-di-phosphite (molecular weight 517)

  These are commercially available from Asahi Denka Kogyo Co., Ltd. as Adeka Tab 1178, 2112, PEP-8, PEP-24G, PEP-36G, and HP-10, and Sandostab P-EPQ from Clariant. Is possible.

(Thioether stabilizer)
Next, a thioether stabilizer having a molecular weight of 500 or more that can be added to the cellulose ester in the present invention will be described.
Any known thioether stabilizer can be used as the thioether stabilizer.
Specific examples of the thioether-based stabilizer include the following compounds, but preferred examples that can be used in the present invention are not limited thereto.

(TE-1)
Dilauryl-3,3-thiodipropionate (molecular weight 515)
(TE-2)
Dimyristyl-3,3-thiodipropionate (molecular weight 571)
(TE-3)
Distearyl-3,3-thiodipropionate (molecular weight 683)
(TE-4)
Pentaerythritol tetrakis (3-laurylthiopropionate) (molecular weight 1162)

  These are commercially available from Sumitomo Chemical Co., Ltd. as Sumilizer TPL, TPM, TPS, TDP. Also available from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-412S.

(Other stabilizers)
In the present invention, in addition to a phenolic stabilizer having a molecular weight of 500 or more, a phosphite stabilizer having a molecular weight of 500 or more, and a stabilizer useful for melt film formation of a cellulose ester other than a thioether stabilizer having a molecular weight of 500 or more. It doesn't matter. As such a stabilizer, for example, a tin-based stabilizer can be mentioned, and any known tin-based stabilizer can be used. Specific examples of preferable tin-based stabilizers include octyl tin maleate polymer, monostearyl tin tris (isooctyl thioglycolate), and dibutyl tin dilaurate.

Moreover, the said amine stabilizer is also utilized, In that case, well-known arbitrary amine stabilizers can be used. Specific examples of preferred amine stabilizers include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-[(2H-benzotriazol-2-yl) phenol]]. , Tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate, phenyl-β-naphthylamine, N, N′-di-sec-butyl-p- Phenylenediamine, N, N′-diphenyl-p-phenylenediamine, N-phenyl-N′-cyclohexyl-p-phenylenediamine, N-isopropyl-N′-phenyl-p-phenylenediamine, 4-benzoyloxy-2, 2,6,6-tetramethylpiperazine, bis (2,2,6,6-tetramethyl-4-piperidine) sebacate, bis [(1,2,2,6,6-pen Tamethyl-4-piperidinyl) 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butyl malonate, tetrakis (2,2,6,6-tetramethyl-4-piperidinyl) 1 , 2,3,4-butane-tetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidinyl) 1,2,3,4-butane-tetracarboxylate and the like. These are commercially available from Asahi Denka as ADK STAB LA-57, LA-52, LA-67, LA-62, LA-77, and TINUVIN 765, 144 from Ciba Specialty Chemicals. .
The timing of adding these may be at any stage of the melt (melt) production process as described later, and the process of adding additives at the end of the melt production process (melt preparation process) is added. May be.

(Use of stabilizer)
In the present invention, at least one phenolic stabilizer having a molecular weight of 500 or more, and at least one selected from the group consisting of a phosphite stabilizer having a molecular weight of 500 or more and a thioether stabilizer having a molecular weight of 500 or more, cellulose One feature is that it is added to the ester. These stabilizers are required not to volatilize even at high temperatures, and have a molecular weight of 500 or more, preferably 500 to 3000, more preferably 530 to 3000, and particularly preferably 600 to 2000. In addition, since it is preferable that it does not easily volatilize at a high temperature, the amount of mass loss when heated in air at 220 ° C. for 30 minutes is preferably 20% by mass or less, more preferably 15% by mass or less, The content is more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

  The amount of these stabilizers used is 0.02 to 3% by mass of at least one phenol-based stabilizer having a molecular weight of 500 or more based on the cellulose ester, and a phosphite-based stabilizer having a molecular weight of 500 or more. At least one selected from the group consisting of an agent and a thioether-based stabilizer having a molecular weight of 500 or more is 0.02 to 3% by mass with respect to the cellulose ester. The preferred use amount of these stabilizers is 0.03 to 2.5% by mass, more preferably 0.04 to 1.0% by mass, and still more preferably 0.05 to 0.7% by mass. Especially preferably, it is 0.05-0.6 mass%. The ratio between the content of the phenol-based stabilizer and the content of the phosphite-based stabilizer or the thioether-based stabilizer is not particularly limited, but is preferably 1/10 to 10/1 (parts by mass), and more Preferably it is 1/5 to 5/1 (parts by mass), more preferably 1/3 to 3/1 (parts by mass), and particularly preferably 1/3 to 2/1 (parts by mass).

  In the present invention, the method of adding at least one phenol-based stabilizer and at least one selected from a phosphite-based stabilizer or a thioether-based stabilizer to the cellulose ester may be added at the time of melt film formation. If it does not specifically limit. For example, it may be added at the time of synthesis of the cellulose ester, may be mixed in the cellulose ester in advance before melting, or preferably formed into a film while being mixed with the cellulose ester at the time of melt film formation. When adding at the time of the synthesis | combination of a cellulose ester, you may add before and after the precipitation production | generation of a cellulose ester, or when a cellulose ester is disperse | distributed in a solution state. Thereby, a cellulose ester and an additive can be mixed uniformly.

  In addition, in this invention, you may produce the stabilizer containing master pellet which made the cellulose ester contain stabilizer higher than a desired quantity previously. In that case, it is necessary to prepare the cellulose ester master pellet (cellulose ester master pellet) which does not contain a stabilizer separately. In that case, the stabilizer concentration in the stabilizer-containing master pellet is not particularly defined, but preferably 2 to 50 times the final stabilizer concentration in the cellulose ester film, more preferably 2 to 30 times, still more preferably. Is 3 to 25 times, particularly preferably 4 to 20 times. The following methods can be used for mixing the cellulose ester master pellet and the stabilizer master pellet. It should be noted that additives other than the above stabilizer (plasticizer, fine particles, other additives, etc.) may be added together at the stage of preparing the stabilizer master pellet. The additive concentration is preferably 2 to 50 times the final concentration of additives other than the stabilizer in the cellulose ester film, more preferably 2 to 30 times, still more preferably 3 to 25 times, Especially preferably, it is 4 to 20 times.

  In addition, when the additive is mixed after the cellulose ester is prepared as a powder, it is important to mix uniformly because the powder is mixed with each other. That is, when the stabilizer is powder, it is effective to use a mixing device in order to uniformly mix the cellulose ester powder. These include, for example, a container rotating type, a container fixing type, or a composite type thereof. Specifically, a rotating horizontal type (horizontal cylinder, inclined cylinder, V type, twentieth pyramid, square body, S-shaped, continuous type) V type, etc.), rotation axis horizontal (eg, ribbon, screw, rod, pin, double axis paddle, etc.), rotation vertical (ribbon, screw, conical screw, high speed flow, rotating disk, muller, etc.), vibration type (Vibration mill, sieve, etc.), internal blade type (horizontal cylinder, V type, double cone, etc.) can be used as the rotary type. During mixing, it is desirable to control the humidity, temperature and oxygen concentration so that the additive and cellulose ester are stable. Preferably, the humidity is lower and the temperature is lower. That is, the preferred humidity is 70% or less relative humidity, more preferably 50% or less relative humidity, more preferably 350% or less relative humidity, and particularly preferably 20% or less relative humidity. The temperature is preferably −20 to 100 ° C., more preferably 0 to 80 ° C., still more preferably 5 to 60 ° C., and particularly preferably 10 to 50 ° C.

  The oxygen concentration is preferably low, the oxygen concentration in the gas is preferably 10% by volume or less, more preferably 5% by volume or less, and still more preferably 2% by volume or less, The oxygen concentration is particularly preferably 1% by volume or less. The method for reducing the oxygen concentration is not particularly limited, but it can be achieved by degassing with an inert gas (for example, nitrogen, argon, helium, etc.) or vacuum equipment. It is recommended that the additive-containing cellulose ester mixture thus mixed is melt-pelletized or film-formed while maintaining a low oxygen concentration. In addition, when it is made by melting in a low oxygen concentration atmosphere in the pelletizing step, it may not be necessary to control the oxygen concentration during melt film formation, and the load on the step is reduced.

"Additive"
In the present invention, various additives may be further added to the cellulose ester as necessary. The addition may be performed at any stage from before the preparation of the melt to after the preparation. In the present invention, as additives other than stabilizers, plasticizers, ultraviolet absorbers (UV agents), fine particles, optical adjusting agents, release agents, surfactants, thermal stabilizers, antistatic agents, flame retardants, lubricants, oil agents Etc. can be used.

(Plasticizer)
First, the plasticizer will be described. If a plasticizer is added to the cellulose ester, the crystal melting temperature (Tm) of the cellulose ester can be lowered. The molecular weight of the plasticizer used in the present invention is not particularly limited, but is preferably a high molecular weight, for example, preferably a molecular weight of 500 or more, more preferably 550 or more, and further preferably 600 or more. Examples of the plasticizer include phosphate esters, alkylphthalylalkyl glycolates, carboxylic acid esters, and fatty acid esters of polyhydric alcohols. These plasticizers may be solid or oily. That is, the melting point and boiling point are not particularly limited. When performing melt film formation, those having non-volatility can be particularly preferably used.

  Specific examples of the phosphate ester include trixylyl phosphate, tris ortho-biphenyl phosphate, cresyl phenyl phosphate, biphenyl diphenyl phosphate, 1,4-phenylene tetraphenyl phosphate, and the like. Moreover, it is also preferable to use the phosphate ester type plasticizer described in Embodiments 3 to 7 of JP-T-6-501040. Examples of the alkyl phthalyl alkyl glycolates include butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalate Examples include ruoctyl glycolate, octyl phthalyl methyl glycolate, and octyl phthalyl ethyl glycolate.

  Examples of carboxylic acid esters include phthalates such as didodecyl phthalate, and citrates such as acetyl trioctyl citrate, bis (2-ethylhexyl) adipate, diisodecyl adipate, and bis (butyl diglycol adipate). Aromatic polycarboxylic acids such as adipic acid esters, tetraoctyl pyromellitate and trioctyl trimellitate, and aliphatic polycarboxylic acids such as dioctyl adipate, dibutyl sebacate, dioctyl sebacate and dioctyl azelate Examples thereof include fatty acid esters of polyhydric alcohols such as esters, diglycerin tetraacetate, and diglyceride.

  In addition, aliphatic polyesters composed of glycol and dibasic acid such as polyethylene adipate, polybutylene adipate, polyethylene succinate, polybutylene succinate, aliphatic polyesters composed of oxycarboxylic acid such as polylactic acid, polyglycolic acid, High molecular weight plasticizers such as aliphatic polyesters composed of lactones such as polycaprolactone, polypropiolactone and polyvalerolactone, and vinyl polymers such as polyvinylpyrrolidone are also included. These plasticizers can be used alone or in combination with a low-part plasticizer.

  The polyhydric alcohol plasticizer has good compatibility with cellulose fatty acid esters, and glycerin ester compounds such as glycerin esters and diglycerin esters that exhibit a remarkable thermoplastic effect, and polyalkylenes such as polyethylene glycol and polypropylene glycol. Preferred examples include compounds in which an acyl group is bonded to the hydroxyl group of glycol or polyalkylene glycol. Specific glycerin esters include glycerin acetate dinonanoate, glycerin acetate dioctanoate, glycerin dipropionate laurate, glycerin dipropionate myristate, glycerin dipropionate palmitate, glycerin dipropionate stearate, glycerin Examples thereof include, but are not limited to, dipropionate oleate and glycerol tripentanoate.

  Specific examples of the diglycerin ester include diglycerin tetrapropionate, diglycerin tetrabutyrate, diglycerin tetravalerate, diglycerin tetracaprylate, diglycerin tetrapelargonate, diglycerin tetracaprate, diglycerin. Glycerol tetralaurate, diglycerol triacetate valerate, diglycerol diacetate dilaurate, diglycerol diacetate distearate, diglycerol diacetate dioleate, diglycerol acetate trilaurate, diglycerol acetate trimyristate, diglycerol acetate tri Examples thereof include mixed acid esters of diglycerin such as palmitate, diglyceryl acetate tristearate and diglyceryl acetate trioleate.

  Specific examples of the polyalkylene glycol include, but are not limited to, polyethylene glycol and polypropylene glycol having an average molecular weight of 200 to 1000. Specific examples of the compound in which an acyl group is bonded to the hydroxyl group of polyalkylene glycol include polyoxyethylene acetate, polyoxyethylene butyrate, polyoxyethylene valerate, polyoxyethylene octanoate, polyoxyethylene laurate, polyoxyethylene laurate, Examples include oxyethylene myristate, polyoxyethylene stearate, polyoxyethylene oleate, polyoxypropylene propionate, polyoxypropylene octanoate, polyoxypropylene oleate, and polyoxypropylene linoleate. It is not limited.

These plasticizers may be used alone or in combination.
The addition amount of the plasticizer is preferably 1 to 20% by mass, more preferably 1 to 15% by mass, and most preferably 2 to 10% by mass with respect to the cellulose ester.

(UV absorber)
An ultraviolet inhibitor may be added to the cellulose ester. With respect to the ultraviolet ray inhibitor, JP-A-60-235852, JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, JP-A-6-118233. 6-148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173. . The addition amount is preferably 0.01 to 2% by mass, more preferably 0.01 to 1.5% by mass of the melt (melt) to be prepared.

  That is, in this invention, it is preferable to make a cellulose ester contain 1 type, or 2 or more types of ultraviolet absorbers. From the viewpoint of preventing the deterioration of the liquid crystal, the ultraviolet absorber is preferably excellent in the ability to absorb ultraviolet rays having a wavelength of 380 nm or less, and less visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, benzotriazole compounds are preferable because they are less colored with respect to cellulose esters.

  Preferred ultraviolet absorbers include pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5 -Methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n- Octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl -4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N'-hexame Tylene bis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) Examples include benzene and tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate.

  In particular, the ultraviolet absorbers include 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tri Most preferred is ethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate].

  The following commercially available products can also be used as these ultraviolet absorbers. As benzotriazoles, TINUBIN P (Ciba Specialty Chemicals), TINUBIN 234 (Ciba Specialty Chemicals), TINUBIN 320 (Ciba Specialty Chemicals), TINUBIN 326 (Ciba Specialty Chemicals) TINUBIN 327 (Ciba Specialty Chemicals), TINUBIN 328 (Ciba Specialty Chemicals), Sumisorb 340 (Sumitomo Chemical), Adekas Type LA-31 (Asahi Denka Kogyo Co., Ltd.), etc. . In addition, as benzophenone-based ultraviolet absorbers, Seasorb 100 (manufactured by Sipro Kasei Co., Ltd.), Seasorb 101 (manufactured by Sipro Kasei Co., Ltd.), Seasorb 101S (manufactured by Sipro Kasei Co., Ltd.), Seasorb 102 (manufactured by Sipro Kasei Co., Ltd.), Seasorb 103 (Sipro Kasei) Kasei Co., Ltd.), Adekas Type LA-51 (Asahi Denka Kogyo Co., Ltd.), Chemisorp 111 (Chemipro Kasei Co., Ltd.), UVINUL D-49 (BASF Corp.), and the like. Examples of oxalic acid anilide UV absorbers include TINUBIN 312 (manufactured by Ciba Specialty Chemicals) and TINUBIN 315 (manufactured by Ciba Specialty Chemicals). In addition, as a salicylic acid ultraviolet absorber, Seasorb 201 (manufactured by Sipro Kasei) and Seasorb 202 (manufactured by Sipro Kasei) are marketed, and as a cyanoacrylate ultraviolet absorber, Seasorb 501 (manufactured by Sipro Kasei), UVINUL N-539 (BASF) is available.

(Fine particles)
In the present invention, fine particles may be mixed in the cellulose ester. Examples of the fine particles include fine particles of inorganic compounds and fine particles of organic compounds, and any of them may be used. The average primary particle size of the fine particles contained in the cellulose ester in the present invention is preferably 5 nm to 3 μm, more preferably 5 nm to 2.5 μm, and more preferably 20 nm to 2.0 μm from the viewpoint of keeping haze low. More preferably it is. Here, the average primary particle size of the fine particles is determined by observing the cellulose ester film with a transmission electron microscope (magnification of 500,000 to 1,000,000 times) and determining the average value of the primary particle sizes of 100 particles. The addition amount of the fine particles is preferably 0.005 to 1.0% by mass, more preferably 0.01 to 0.8% by mass, and still more preferably 0.02 to 0.0. 4% by mass.

  The average secondary particle size of the fine particles in the cellulose ester film finally obtained by the production method of the present invention is preferably 0.01 to 5 μm, more preferably 0.02 to 3 μm. 0.02 to 1 μm is particularly preferable. Here, the average secondary particle size of the fine particles is determined by observing the cellulose ester film with a transmission electron microscope (magnification of 100,000 to 1,000,000 times) and determining the average value of the secondary particle sizes of 100 particles. To do.

Examples of the inorganic compound include SiO ₂ , ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , ZrO ₂ , In ₂ O ₃ , MgO, BaO, MoO ₂ , V ₂ O ₅ , talc, clay, calcined kaolin, and calcined. Examples include calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Preferably, it is at least one of SiO ₂ , ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , ZrO ₂ , In ₂ O ₃ , MgO, BaO, MoO ₂ and V ₂ O ₅ , more preferably SiO _2. , TiO ₂ , SnO ₂ , Al ₂ O ₃ and ZrO ₂ .

As the fine particles of SiO ₂ , for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.) can be used. . As the ZrO ₂ fine particles, for example, commercially available products such as Aerosil R976 and R811 (above, manufactured by Nippon Aerosil Co., Ltd.) can be used. Seahoster KE-E10, E30, E40, E50, E50, E70, E150, W10, W30, W50, P10, P30, P50, P100, P150, P250 ) Etc. can also be used. Furthermore, silica microbeads P-400 and 700 (catalyst chemical industry product) can also be used. Also, SO-G1, SO-G2, SO-G3, SO-G4, SO-G5, SO-G6, SO-E1, SO-E2, SO-E3, SO-E4, SO-E5, SO-E6, SO-C1, SO-C2, SO-C3, SO-C4, SO-C5, SO-C6 (manufactured by Admatechs Co., Ltd.) can also be used. Further, silica particles 8050, 8070, 8100, and 8150 (manufactured by Moritex Co., Ltd., powdered water dispersion) can also be used.

  Next, as the fine particles of the organic compound that can be used in the present invention, for example, polymers such as silicone resins, fluororesins, and acrylic resins are preferable, and silicone resins are particularly preferable. The silicone resin preferably has a three-dimensional network structure, such as Tospearl 103, 105, 108, 120, 145, 3120, and 240 (above, manufactured by Toshiba Silicone Co., Ltd.). Commercial products having a trade name can be used.

Further, it is preferable to use fine particles made of an inorganic compound that are surface-treated in order to stably exist in the cellulose ester film. As the surface treatment method, there are a chemical surface treatment method using a coupling agent and a physical surface treatment method such as plasma discharge treatment and corona discharge treatment. In the present invention, a coupling agent should be used. Is preferred. As the coupling agent, an organoalkoxy metal compound (for example, a silane coupling agent, a titanium coupling agent, etc.) is preferably used. When inorganic fine particles are used as the fine particles (especially when SiO ₂ is used), treatment with a silane coupling agent is particularly effective. As the silane coupling agent, an organosilane compound represented by the following general formula (11) can be used. Although the usage-amount of the said coupling agent is not specifically limited, It is recommended to use 0.005-5 mass% preferably with respect to an inorganic fine particle, Furthermore, it is preferable to use 0.01-3 mass%.

R _x Si (OR ′) _(4-x) (11)
(In the formula, R and R ′ each independently represent a hydrogen atom, an alkyl group, an aryl group, an allyl group, or a fluoroalkyl group. The alkyl group is an epoxy group, an amino group, an acrylic group as a substituent. And may have a group, an isocyanate group, and / or a mercapto group, x is an integer of 0 to 3, preferably an integer of 0 to 2.)

Specific examples of the organosilane represented by the general formula (11) include the following, but the organosilane that can be used in the present invention is not limited to these examples.
Examples of the compound where x in the general formula (11) is 0 include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetra-n-butoxysilane.
a compound of x is 1, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, _{phenyltriethoxysilane, CF 3 CH 2 CH 2 Si} ( OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₅ CH ₂ CH ₂ Si (OCH ₃ ) ₃ , γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane , Γ-trimethoxysilylpropyl isocyanate, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and the like.
Examples of compounds in which x is 2 include dimethyldimethoxysilane, dimethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-aminopropylmethyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and γ-methacryloxypropylmethyldimethoxy. Silane etc. are mentioned.
Further, two or more different organosilanes can be used in combination for the purpose of adjusting the hardness and brittleness of the cured film and introducing functional groups.

  The coupling agent is processed by a direct processing method for fine particles and an integral blend method. The direct method is roughly classified into a dry method, a slurry method, and a spray method. The use of an agitator such as a Henschel mixer, a super mixer, a ready mixer, a V-type blender or an open kneader is particularly preferred. It is preferable that fine particles and a small amount of water, or an organic solvent containing water and a coupling agent are mixed, stirred with an open kneader to remove water, and further finely dispersed. The addition of these fine particles to the cellulose ester can be carried out by a method such as kneading by a conventional method. Particularly preferably, the fine particles previously dispersed in a solvent and the cellulose ester are mixed and dispersed, and then the solvent is volatilized. It may be preferable to use a solid product in the process of producing a cellulose ester melt from the viewpoint of obtaining a uniform melt. In order to uniformly disperse the fine particles in the film, the method may include a step in which the fine particles are finely divided from the powder and finely dispersed by a share in a kneader or a die during film formation. preferable. In addition to the fine particles, other functional materials (for example, a plasticizer and / or an ultraviolet absorber) may be simultaneously dissolved and dispersed in a solvent and mixed for use as required.

In the present invention, fine particle-containing master pellets having a higher concentration of stabilizer than the desired amount in cellulose ester may be prepared in advance. This makes it possible to produce cellulose ester pellets with good dispersibility of fine particles, and it is possible to produce a cellulose ester film having excellent surface shape and surface slipperiness (prevention of creaking) with good handling properties.
At this time, it is necessary to prepare a cellulose ester master pellet (cellulose ester master pellet) that does not contain fine particles. In that case, it is preferable to contain the above-mentioned stabilizer in the fine particle-containing master pellet at the same time. The amount of fine particles added in the fine particle-containing master pellet is not particularly limited, but is preferably 2 to 50 times the fine particle final concentration in the cellulose ester film, more preferably 2 to 30 times, and still more preferably 3 -25 times, particularly preferably 4-20 times. The above-mentioned mixer can be used for mixing the cellulose ester master pellet and the fine particle-containing master pellet. It should be noted that additives other than fine particles (stabilizers, plasticizers, other additives, etc.) may be added together at the stage of preparing the fine particle-containing master pellet. The final concentration of the desired additive in the cellulose ester film is preferably 2 to 50 times, more preferably 2 to 30 times, still more preferably 3 to 25 times, and particularly preferably 4 to 20 times. .

(Optical adjusting agent)
In the present invention, an optical adjusting agent (a retardation control agent, particularly a retardation increasing agent) for controlling optical anisotropy may be added to the cellulose ester. In the present invention, an aromatic compound having at least one aromatic ring is preferably used as a retardation control agent in order to adjust the retardation of the cellulose ester film. An aromatic compound is normally used in 0.01-20 mass parts with respect to 100 mass parts of cellulose esters. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, and more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the cellulose ester. At this time, two or more kinds of aromatic compounds may be used in combination. The aromatic ring of the aromatic compound here includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As a hetero atom contained in the heterocycle, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.

(Release agent)
The cellulose ester in the present invention preferably contains a compound having a fluorine atom. The compound having a fluorine atom can exhibit an action as a release agent, and may be a low molecular weight compound or a polymer. Examples of the polymer include the polymers described in JP-A No. 2001-269564. A polymer having a fluorine atom is preferably a polymer obtained by polymerizing a monomer containing an ethylated unsaturated monomer containing a fluorinated alkyl group as an essential component. The fluorinated alkyl group-containing ethylenically unsaturated monomer related to the polymer is not particularly limited as long as it is a compound having an ethylenically unsaturated group and a fluorinated alkyl group in the molecule. A surfactant having a fluorine atom can also be used, and a nonionic surfactant is particularly preferable.

<< Method for producing cellulose ester film >>
Below, the manufacturing method of the cellulose-ester film containing a stabilizer is described in detail. In addition, the cellulose-ester film of this invention is not limited to what was manufactured by these methods.

(1) Pelletization In the present invention, it is preferable that the cellulose ester, the stabilizer and other additives are mixed and pelletized prior to melt film formation. It is preferable to dry the cellulose ester and additives in advance before pelletization. As the moisture content after drying in that case, the cellulose ester mixture is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and particularly preferably 0.2% by mass or less. .

This can be substituted by using a vent type extruder. Pelletization can be made by melting the above cellulose ester and additives at 180 ° C. to 240 ° C. using a biaxial or uniaxial kneading extruder and then solidifying and cutting in noodles. . Pelletization may be performed by an underwater cut method in which the material is cut while being extruded directly into water. Preferably, the pellet size is such cross-sectional area is 1 mm ² to 300 mm ^2, a length 1Mm～30mm, and more preferably the cross-sectional area of 2 mm ² 100 mm ^2, length 1.5Mm～10mm. The number of revolutions of the extruder is preferably 10 rpm to 1000 rpm, more preferably 30 rpm to 500 rpm. The extrusion residence time in pelletization is usually 10 seconds to 30 minutes, preferably 10 seconds to 3 minutes. In the pelletization, it is preferable to remove or reduce oxygen. In that case, a preferable oxygen concentration that can be achieved by maintaining an inert gas (for example, nitrogen, helium, argon, etc.) or a reduced pressure state. Is 10% by volume or less, more preferably 5% by volume or less, still more preferably 2% by volume or less, and particularly 0.5% by mass or less.
In addition, although it does not specifically limit about the addition method of the stabilizer of this invention as mentioned above, generally mixing at the time of pelletization is preferable and recommended. However, the pellets are melted and pelletized by adding a high concentration of stabilizers and other additives to cellulose ester master pellets that have been melted and pelletized only in advance, with the melting temperature during pelletization at a low temperature. It is also preferable that the stabilizer-added master pellets are put into a melt extruder so as to obtain a desired stabilizer addition amount during melt film formation.

(2) Melt film formation Next, melt film formation will be described.

(Dry)
Prior to melt film formation, the moisture content of the cellulose ester and stabilizers and other additives, as well as the moisture content in the master pellets prepared beforehand (cellulose ester master pellets, stabilizer master pellets, additive-containing master pellets) is dried. Is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less. The drying temperature for this is preferably 40 to 180 ° C, the drying temperature is preferably 60 to 150 ° C, and the particularly preferred drying temperature is 80 to 130 ° C. The drying air flow rate is preferably be 20 to 400 m ³ / hour, and particularly preferably 100 to 250 m ³ / hour. The dew point of the drying wind is preferably 0 to -60 ° C, more preferably -20 to -40 ° C. At this time, it is preferable that the drying air is one from which moisture has been removed. Such dry air can be prepared by passing through a moisture removing device or blowing nitrogen gas. Further, it is preferable to remove or reduce oxygen during drying. Specifically, oxygen can be removed or reduced by using an inert gas (for example, nitrogen, helium, argon, or the like) or in a reduced pressure state. A preferable oxygen concentration is 10% by volume or less, more preferably 5% by volume or less, still more preferably 2% by volume or less, and particularly preferably 0.5% by mass or less.

(Melt extrusion)
Cellulose ester is fed into the cylinder through the feed port of the extruder. FIG. 1 shows a schematic diagram of a typical extruder 22 that can be used in the present invention. The cylinder 32 was melt-kneaded and compressed in order from the supply port 40 side, a supply part (region A) for quantitatively transporting the cellulose ester supplied from the supply port, and a compression unit (region B) for melt-kneading and compressing the cellulose ester. It is comprised with the measurement part (area | region C) which measures a cellulose ester. The cellulose ester film is preferably dried in order to reduce the amount of water by the above-mentioned method. However, in order to prevent oxidation of the molten cellulose ester by residual oxygen, the inside of the extruder is in an inert (nitrogen or the like) air stream. Alternatively, it is more preferable to carry out evacuation using a vented extruder. The screw compression ratio of the extruder is preferably set to 2.5 to 4.5, and L / D is preferably set to 20 to 70. Here, the screw compression ratio is expressed by a volume ratio between the supply unit A and the measurement unit C, that is, (volume per unit length of the supply unit A) / (volume per unit length of the measurement unit C). It is calculated using the outer diameter d1 of the screw shaft of the part A, the outer diameter d2 of the screw shaft of the measuring part C, the groove part diameter a1 of the supplying part A, and the groove part diameter a2 of the measuring part C. L / D is the ratio of the cylinder length to the cylinder inner diameter. Moreover, it is preferable that extrusion temperature is set to 190-240 degreeC. When the temperature in the extruder exceeds 230 ° C., it is preferable to provide a cooler between the extruder and the die.

  If the screw compression ratio is too small, the melt will not be melted and kneaded sufficiently, and undissolved parts will occur, or the heat generated by shearing will be too small, resulting in insufficient melting of the crystals, and fine crystals will remain in the cellulose ester film after production. In addition, there is a tendency that bubbles are easily mixed. Thereby, when the strength of the cellulose ester film is reduced, or when the film is stretched, the remaining crystals may impair the stretchability and the orientation may not be sufficiently increased. On the other hand, if the screw compression ratio is too large, shear stress is excessively applied and the cellulose ester is likely to be deteriorated due to heat generation, so that the cellulose ester film after production tends to be yellowish. Moreover, when too much shear stress is applied, molecular cutting occurs, the molecular weight may decrease, and the mechanical strength of the film may decrease. The screw compression ratio is preferably in the range of 2.5 to 4.5, more preferably in the range of 2.8 to 4.5 in order to make the cellulose ester film after production hardly yellowish and the film strength is strong and the stretch breakage is difficult. 4.2, particularly preferred is the range of 3.0 to 4.0.

On the other hand, if L / D is too small, melting and kneading are insufficient, and fine crystals tend to remain in the cellulose ester film after production as in the case where the compression ratio is small. On the other hand, if L / D is too large, the residence time of the cellulose ester in the extruder becomes too long, and the cellulose ester tends to be deteriorated. In addition, when the residence time is long, the molecule may be cut, or the molecular weight may be reduced to lower the mechanical strength of the cellulose ester film. In order to make the cellulose ester film after production hardly yellowish and the film strength is strong and the film is not easily stretched and broken, L / D is preferably in the range of 20 to 70, more preferably in the range of 22 to 65, and particularly preferably. Is in the range of 24-50.
Further, if the extrusion temperature is too low, the crystals are not sufficiently melted, and fine crystals are liable to remain in the cellulose ester film after production, and the film strength is lowered or remains when the film is stretched. There is a tendency that the crystal hinders stretchability and the orientation cannot be sufficiently increased. On the other hand, when the extrusion temperature is too high, the cellulose ester is deteriorated and the degree of yellowness (YI value) tends to deteriorate. The extrusion temperature is preferably 180 ° C. to 230 ° C., more preferably 190 ° C. to 230 ° C., and further preferably, in order to make the cellulose ester film after production hardly yellowish and the film strength is high and it is difficult to stretch and break. Is in the range of 195 ° C to 230 ° C. The temperature at this time shows the temperature of the most downstream part of an extruder.

  In general, single-screw extruders with relatively low equipment costs are often used as the types of extruders, and there are screw types such as full flight, madok and dalmage, but cellulose esters with relatively poor thermal stability. The full flight type is preferable. In addition, although the equipment cost is expensive, it is possible to use a twin-screw extruder that can be extruded while removing a volatile component by providing a vent port in the middle by changing the screw segment. Biaxial extruders can be broadly classified into the same direction and different types, and both can be used. However, the type of co-rotation with high self-cleaning performance is preferred because a stagnant portion is hardly generated. Although the twin-screw extruder is expensive, it has high kneadability and high cellulose ester supply performance, so that it can be extruded at a low temperature and is suitable for forming a cellulose ester film. By appropriately arranging the vent opening, it is possible to use the cellulose acylate pellets and powder in an undried state as they are. Also, film smears produced during film formation can be reused as they are without drying.

  In addition, although the diameter of a screw changes with target extrusion rates per unit time, Preferably it is 10 mm-300 mm, More preferably, it is 20 mm-250 mm, More preferably, it is 30 mm-150 mm. Moreover, in order to improve the thickness accuracy, it is important to reduce the fluctuation of the discharge amount. A gear pump is provided between the extruder and the die to supply a certain amount of cellulose ester from the gear pump. effective. A gear pump is accommodated in a state where a pair of gears consisting of a drive gear and a driven gear are engaged with each other, and the drive gear is driven to engage and rotate the two gears so that a melted state is generated from the suction port formed in the housing. The cellulose ester is sucked into the cavity, and a certain amount of the cellulose ester is discharged from a discharge port formed in the housing. Even if there is a slight fluctuation in the pressure at the tip of the extruder, the fluctuation is absorbed by using the gear pump, the fluctuation in the pressure downstream of the film forming apparatus becomes very small, and the fluctuation in thickness is improved. By using a gear pump, it is possible to make the fluctuation range of the pressure of the die portion within ± 1%.

  In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used. In addition, a high-precision gear pump using three or more gears that eliminates gear fluctuations of the gear pump is also effective. Other advantages of using a gear pump are that the pressure at the tip of the screw can be lowered to form a film, reducing energy consumption, preventing temperature rise of the cellulose ester, improving transport efficiency, shortening the residence time in the extruder, and extruding. The L / D of the machine can be expected to be shortened. In addition, when using a filter for removing foreign matter, if there is no gear pump, the amount of cellulose ester supplied from the screw may fluctuate as the filtration pressure rises. Use a gear pump in combination. This can be solved. On the other hand, as a disadvantage of the gear pump, depending on the method of selecting the equipment, the length of the equipment becomes long, the residence time of the cellulose ester becomes long, and the shearing stress of the gear pump part may cause the molecular chain to be broken, Caution must be taken.

  The preferred residence time from when the cellulose ester enters the extruder through the feed port until it exits the die is 2 minutes to 60 minutes, more preferably 3 minutes to 40 minutes, and even more preferably 4 minutes to 30 minutes. . Since the flow of polymer for bearing circulation in the gear pump becomes poor, the polymer seal in the drive part and the bearing part becomes poor, causing problems such as large fluctuations in metering and pumping pressure. A gear pump design (especially clearance) that matches the viscosity is required. In some cases, the staying part of the gear pump causes deterioration of the cellulose ester, and therefore a structure with as little staying as possible is preferable. The polymer pipes and adapters that connect the extruder and gear pump or gear pump and die, etc. must also be designed with as little residence as possible, and in order to stabilize the extrusion pressure of cellulose ester, which has a high temperature dependence of melt viscosity, It is preferable to make the fluctuation of the smallest possible. Generally, a band heater having a low equipment cost is often used for heating the polymer tube, but it is more preferable to use an aluminum cast heater with less temperature fluctuation. Further, in order to give G ′, G ″, tan δ, and η maximum and minimum values in the extruder, it is preferable that the barrel of the extruder is heated and melted with a heater divided into 3 to 20.

  The cellulose ester is melted by the extruder configured as described above, and the molten cellulose ester is continuously fed from the discharge port to the die. As long as the die has a design in which the residence of molten cellulose ester in the die is small, any type of commonly used T die, fish tail die, and hanger coat die may be used. Also, there is no problem in placing a static mixer for improving temperature uniformity immediately before the die. The clearance at the die exit portion is generally 1.0 to 5.0 times the film thickness, preferably 1.2 to 3 times, more preferably 1.3 to 2 times. When the lip clearance is too smaller than the film thickness, it tends to be difficult to obtain a good sheet by film formation. Further, when the lip clearance is too larger than the film thickness, the sheet thickness accuracy tends to decrease.

  The die is a very important facility for determining the thickness accuracy of the film, and a die that can control the thickness adjustment severely is preferable. Normally, the thickness can be adjusted at intervals of 40 to 50 mm, but preferably a type capable of adjusting the film thickness at intervals of 35 mm or less, more preferably at intervals of 25 mm or less. In addition, since the cellulose ester is highly dependent on the temperature and shear rate of the melt viscosity, it is important to design the die as little as possible in the temperature unevenness of the die and the flow rate unevenness in the width direction. An automatic thickness adjustment die that measures the downstream film thickness, calculates the thickness deviation, and feeds back the result to the die thickness adjustment is also effective in reducing the thickness fluctuation in long-term continuous production. For production of a film, a single-layer film forming apparatus with a low equipment cost is generally used. However, in some cases, a film having two or more types of structures can also be manufactured using a multilayer film forming apparatus in order to provide a functional layer on an outer layer. Is possible. In general, the functional layer is preferably thinly laminated on the surface layer, but the layer ratio is not particularly limited.

In order to filter foreign matter in the cellulose ester and to avoid damage to the gear pump due to foreign matter, it is preferable to perform so-called breaker plate type filtration in which a filter medium is provided at the outlet of the extruder. In order to filter foreign matter with high accuracy, it is preferable to provide a filtration device incorporating a so-called leaf type disk filter after passing through the gear pump. In particular, it is preferable to perform filtration with a metal mesh filter or the like. The mesh size is preferably 2 to 30 μm, more preferably 2 to 20 μm, and still more preferably 2 to 10 μm. At this time, it is preferable to pressurize and shorten the time required for filtration as much as possible. The filtration pressure is preferably 0.5 MPa to 15 MPa, more preferably 2 Pa to 15 MPa, and most preferably 10 Pa to 15 MPa. A higher filtration pressure is preferable because the filtration time can be shortened, but it is preferable to use a high pressure within a range in which the filter is not damaged. The temperature during filtration is preferably from 180 ° C to 230 ° C, more preferably from 180 ° C to 220 ° C, and particularly preferably from 190 ° C to 220 ° C. If the temperature during filtration is less than or equal to the upper limit value, it is preferable because problems such as thermal degradation are unlikely to occur. If the temperature is greater than or equal to the lower limit value, it takes too much time for filtration to cause thermal degradation. Is preferable because it is difficult to cause. The time required for filtration should be as short as possible to prevent yellowing of the film. Filtration rate of the filter 1 cm ² per minute, preferably 0.05～100Cm ^3, more preferably 0.1~100cm ^3, 0.5~100cm ³ is most preferred.

(3) Stretching In the present invention, in order to control film properties, it is also preferable to stretch the film by performing a stretching process. For example, an unstretched film can be stretched to control Re and Rth. At this time, the stretching temperature is preferably Tg to (Tg + 50 ° C.), more preferably (Tg + 5 ° C.) to (Tg + 20 ° C.). A preferable draw ratio is 1% to 300%, more preferably 3% to 200%, at least one side. It is more preferable to stretch with one stretching ratio larger than the other, and the smaller stretching ratio is preferably 1% to 30%, more preferably 3% to 20%, and the larger stretching ratio is 30% to 30%. 300% is preferable, and more preferably 40% to 150%. These stretching operations may be performed in one stage or in multiple stages. The draw ratio here is determined using the following equation.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / (Length before stretching)
Such stretching is preferably performed using a nip roll, a tenter or the like. Moreover, you may use the simultaneous biaxial stretching method of Unexamined-Japanese-Patent No. 2000-37772, Unexamined-Japanese-Patent No. 2001-113591, and Unexamined-Japanese-Patent No. 2002-103445.

  In addition, the angle θ formed by the film forming direction (longitudinal direction) and the slow axis is preferably 0 ± 3 °, more preferably 0 ± 1 ° in the case of longitudinal stretching. In the case of transverse stretching, 90 ± 3 ° or −90 ± 3 ° is preferable, and 90 ± 1 ° or −90 ± 1 ° is more preferable. The thickness of the stretched cellulose ester film is preferably 20 μm to 200 μm, more preferably 30 μm to 140 μm. The thickness unevenness is preferably 0% to 3% in both the longitudinal direction and the width direction, and more preferably 0% to 1%.

<Characteristics of cellulose ester film>
(optical properties)
Next, preferable optical characteristics of the cellulose ester film of the present invention will be described.
In this specification, Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at a wavelength λ. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). A detailed measurement method will be described later.

  The front retardation (Re) of the cellulose ester film of the present invention is preferably 0 to 300 nm, and the absolute value of retardation (Rth) in the thickness direction is preferably 0 to 700 nm. Furthermore, it is more preferable that (Re) is 0 to 250 nm and the absolute value of (Rth) is 0 to 400 nm, in particular, (Re) is 0 to 200 nm and the absolute value of (Rth) is 0. It is preferably ˜350 nm. In particular, the cellulose ester film of the present invention is effective as a polarizing plate protective film. In this case, Re is 0 to 20 nm, Rth is preferably 0 to 80 nm, Re is 0 to 10 nm, Rth is more preferably 0 to 60 nm.

  The cellulose ester film of the present invention can improve the problem of optical property fluctuations accompanying humidity change, and the difference between the optical property of 10% relative humidity and the optical property of 80% at 25 ° C. is small. One feature. The optical characteristic variation due to the humidity change can be evaluated by the absolute value of the change amount due to the humidity change of Re and Rth. That is, the Re humidity change (nm) is the absolute value of the difference between Re (relative humidity 80%) and Re (relative humidity 10%), and the Rth humidity change (nm) is Rth (relative humidity 80%). ) And Rth (relative humidity 10%). In the cellulose ester film of the present invention, the change in Re humidity is preferably 10 nm or less, more preferably 5 nm or less, and further 1 nm or less. Also, the Rth humidity change is preferably 25 nm or less, more preferably 20 nm or less, and further 15 nm or less. Compared to a conventional cellulose triacetate film, the cellulose ester film of the present invention has a humidity change of 2/3 to 1/2.

The cellulose ester film of the present invention can also control the behavior of optical properties with respect to wavelength. That is, the absolute value of the difference between Re (400) and Re (700) at wavelengths of 400 nm and 700 nm is preferably 0 to 15 nm, and the absolute value of the difference between Rth (400) and Rth (700) is 0 to It is preferably 35 nm. When this is expressed by a formula, the cellulose ester film of the present invention preferably satisfies the following formulas (A-1) and (A-2).
Formula (A-1) 0 ≦ | Re (700) −Re (400) | ≦ 15 nm
Formula (A-2) 0 ≦ | Rth (700) −Rth (400) | ≦ 35 nm
(In the formula, Re (400) and Re (700) represent front retardation (Re) at wavelengths of 400 nm and 700 nm, and Rth (400) and Rth (700) represent letters in the thickness direction at wavelengths of 400 nm and 700 nm. Represents the foundation (Rth).)

  In the cellulose ester film of the present invention, Re unevenness and Rth unevenness are suppressed. The Re unevenness and Rth unevenness referred to here were sampled at 7 locations every 20 cm from the end in the width direction in each region of 10 m, 250 m, and 450 m in the length direction of the cellulose ester film to prepare a total of 21 samples. These samples were conditioned at 25 ° C. and 60% relative humidity for 3 hours, measured for Re and Rth in the same environment, and calculated by calculating the difference between the maximum and minimum values obtained. . In the cellulose ester film of the present invention, Re unevenness and Rth unevenness are each preferably less than 3.0 nm, more preferably less than 1.0 nm, more preferably 0.8 nm or less, and 0.6 nm. More preferably, it is as follows. If the above 21 samples cannot be collected, Re unevenness and Rth unevenness are calculated by a method according to this.

  In the cellulose ester film of the present invention, the intrinsic birefringence in the in-plane direction at a wavelength of 590 nm in an environment of 25 ° C. and 60% relative humidity is preferably 0 to 0.001, and the intrinsic birefringence in the thickness direction is The absolute value is preferably 0 to 0.003. More preferably, the intrinsic birefringence in the in-plane direction is 0 to 0.0008, and the absolute value of the intrinsic birefringence in the thickness direction is 0 to 0.0025. More preferably, the intrinsic birefringence in the in-plane direction is 0 to 0.0006, and the absolute value of the intrinsic birefringence in the thickness direction is 0 to 0.001.

(Axis misalignment)
In the cellulose ester film of the present invention, the optical slow axis is preferably parallel or perpendicular to the casting direction or the width direction. In particular, when a stretching process is performed, it is preferable that the stretching is closer to 0 ° when stretching in the casting direction. Specifically, 0 ± 3 ° is more preferable, 0 ± 1.5 ° is more preferable, and 0 ± 0.5 ° is particularly preferable. When stretched in the width direction, 90 ± 3 ° or −90 ± 3 ° is preferable, more preferably 90 ± 1.5 ° or −90 ± 1.5 °, and still more preferably 90 ± 0.5 ° or − 90 ± 0.5 °.

(Elastic modulus, breakage progress, thermal dimensional change, water permeability, equilibrium water content)
Elastic modulus of the cellulose ester film of the present invention is preferably from ^{1.5kN / mm 2 ~3.5kN / mm 2} , more preferably from ^{1.8kN / mm 2 ~2.6kN / mm 2} . The breaking elongation is preferably 3% to 300%. Tg is preferably 95 ° C to 145 ° C. The thermal dimensional change at 80 ° C. for 1 day is preferably 0% to ± 1% in both the vertical and horizontal directions, and more preferably 0% to ± 0.3%. The water permeability at 40 ° C. / RH 90% 300g / m ² · day to 1000 g / m ² · day is preferred, more preferably 500 g / m ² · day ~800g / m ² · day. The equilibrium moisture content at 25 ° C./80% relative humidity is preferably 1% by mass to 4% by mass, and more preferably 1.5% by mass to 2.5% by mass.

(Residual solvent amount)
The cellulose ester film of the present invention does not contain or contains very little residual solvent. The amount of residual solvent is preferably 0.01% by mass or less, and most preferably zero. In particular, in the production method of the present invention by melt film formation, a solvent is not used at the time of film formation.

(Thickness and unevenness)
The film thickness of the cellulose ester film of the present invention is 20 to 300 μm, more preferably 30 μm to 200 μm, still more preferably 30 μm to 150 μm, and particularly preferably 40 to 120 μm. Therefore, it is preferable that the film thickness of the unstretched film on the premise that the film is stretched is previously set to be a thick extrudate film thickness depending on the stretch ratio. The thickness unevenness of the cellulose ester film of the present invention is preferably 0 to 5 μm in both the thickness direction and the width direction, more preferably 0 to 3 μm, and still more preferably 0 to 2 μm. Further, the angle θ formed by the film forming direction (longitudinal direction) and the slow axis of Re of the film is preferably as close to 0 °, + 90 °, or −90 °.

(Kishimi value)
In the present invention, by adding fine particles or a slipping agent to the cellulose ester film, the kimimi value can be reduced and the transportability can be improved. In the present invention, the dynamic and static kimi values of the cellulose ester film are both preferably 0.2 to 1.5, more preferably 0.2 to 1.3, and still more preferably 0.256. -1.0. When the presence state of the fine particles is coarse, the kishimi value may be small or large, and not only the transportability is unfavorable but also not recommended with the occurrence of scratches. A method for measuring the kishimi value will be described later.

(Arithmetic mean roughness)
The cellulose ester film containing fine particles has a moderate surface roughness. The degree of the surface roughness is represented by a commonly used arithmetic average roughness (Ra). The arithmetic average roughness (Ra) of the cellulose ester film of the present invention is preferably 1 nm to 500 nm, more preferably 1 nm to 250 nm, and particularly preferably 1 nm to 200 nm. The arithmetic average roughness (Ra) can be measured by a generally used contact type or non-contact type surface roughness measuring machine.

(Transmittance)
The transmittance of the cellulose ester film of the present invention is preferably 90% or more, more preferably 91% or more, and particularly preferably 92% or more. The transmittance is obtained by cutting a film sample into 20 mm × 70 mm, and measuring the transmittance of visible light (615 nm) with a transparency measuring device (AKA photoelectric colorimeter, manufactured by KOTAKI Corporation) at 25 ° C. and 60% relative humidity. Is obtained.

(Haze)
The cellulose ester film of the present invention preferably has a haze in the range of 0 to 1.5%, more preferably 0 to 1.2%, still more preferably 0 to 0.8%, and particularly preferably. Is 0.01 to 0.5%. The haze is measured according to JIS K-6714 using a haze meter (HGM-2DP, Suga Test Instruments) at 25 ° C. and a relative humidity of 60% after cutting a film sample into 40 mm × 80 mm.

The main preferable characteristics of the stretched cellulose ester film described above are described below. The tensile modulus is preferably 1.5 kN / mm ² or more and less than 3.0 kN / mm ² , more preferably 1.8 kN / mm ^{2 to} 2.6 kN / mm ² . The breaking elongation is preferably 3% to 100%, more preferably 8% to 50%. Tg is preferably 95 ° C to 145 ° C, more preferably 100 ° C to 140 ° C, and particularly preferably 105 ° C to 135 ° C. The thermal dimensional change at 80 ° C. for 1 day is preferably 0% to ± 1% in both the vertical and horizontal directions, and more preferably 0% to ± 0.3%. The water permeability at 40 ° C. relative humidity of 90% 300g / m ² · day to 1000 g / m ² · day is preferred, more preferably 500 g / m ² · day ~800g / m ² · day. The equilibrium water content at 25 ° C. and a relative humidity of 80% is preferably 1% by mass to 4% by mass, and more preferably 1.5% by mass to 2.5% by mass. The haze is preferably 0% to 3%, more preferably 0% to 1% or less. The total light transmittance is preferably 90% to 100%.

《Functionalization of cellulose ester film》
Next, the preferable aspect in the case of providing a function further to the cellulose-ester film of this invention is described.

(surface treatment)
First, a surface treatment method for a cellulose ester film will be described. The cellulose ester film can achieve improved adhesion between the cellulose ester film and each functional layer (for example, the undercoat layer and the back layer) by performing a surface treatment. As the surface treatment, for example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment refers to so-called low temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr (about 0.13 to 2666 Pa), but may be a glow discharge treatment under atmospheric pressure.

  First, glow discharge treatment under low pressure is performed in US Pat. Nos. 3,462,335, 3,761,299, 4,072,769, and British Patent 891,469. It is described in the specification. In addition, a specific gas such as an inert gas, nitrogen oxides, or an organic compound gas is also introduced. When the surface of the polymer is subjected to glow discharge treatment, it may be carried out at atmospheric pressure or under reduced pressure. Further, it may be carried out while introducing various gases such as oxygen, nitrogen, helium or argon and water into the atmosphere of the glow discharge treatment.

  As the surface treatment of the cellulose ester film of the present invention, an ultraviolet irradiation method is also preferably used. The mercury lamp used in the ultraviolet irradiation method is a high-pressure mercury lamp made of a quartz tube, and preferably has an ultraviolet wavelength of 180 nm to 380 nm. As long as the surface temperature of the cellulose ester film rises to around 150 ° C. with respect to the support performance, there is no problem with the UV irradiation method, and a high-pressure mercury lamp with a dominant wavelength of 365 nm can be used as the light source. When low temperature treatment is required, a low pressure mercury lamp having a dominant wavelength of 254 nm is preferable. It is also possible to use an ozone-less high-pressure mercury lamp and a low-pressure mercury lamp. With regard to the amount of processed light, the greater the amount of processed light, the better the adhesive strength between the cellulose ester film and the adherend layer. However, there is a problem that the support is colored and the support becomes brittle as the amount of light increases. .

Further, corona discharge treatment is also preferable as the surface treatment of the cellulose ester film of the present invention. As the corona discharge treatment apparatus for performing the corona discharge treatment, a solid state corona treatment machine manufactured by Pillar, a LEPEL type surface treatment machine, a VETAPHON type treatment machine, or the like can be used. The corona discharge treatment can be performed in air at normal pressure. The discharge frequency during the treatment is usually 5 to 40 kHz, more preferably 10 to 30 kHz, and the waveform is preferably an alternating sine wave. The gap clearance between the electrode and the dielectric roll is preferably 0.1 mm to 10 mm, more preferably 1.0 mm to 2.0 mm. Discharge is processed above a dielectric support roller provided in the discharge zone, and the treatment amount is usually 0.3 to 0.4 KV · A · min / m ² , preferably 0.34 to 0.38 KV · A · min. / M ² .

Next, flame treatment which is a kind of the surface treatment will be described. The gas used for the flame treatment may be natural gas, liquefied propane gas, or city gas, but the mixing ratio with air is important. The mixing ratio of natural gas / air is usually 1/6 to 1/10, preferably 1/7 to 1/9 by volume. In the case of liquefied propane gas / air, it is usually 1/14 to 1/22, preferably 1/16 to 1/19, and in the case of city gas / air, it is usually 1/2 to 1/8, preferably 1/3. ~ 1/7. The flame treatment amount is usually 1 to 50 Kcal / m ² , preferably 3 to 20 Kcal / m ² .

  Next, the alkali saponification treatment preferably used as the surface treatment of the cellulose ester film of the present invention will be specifically described. It is preferable that the cellulose ester film surface is immersed in an alkaline solution, then neutralized with an acidic solution, washed with water and dried. Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution, and the concentration of hydroxide ions is preferably 0.1 mol / L to 4.0 mol / L, and 0.5 mol / L to 3. More preferably, it is 5 mol / L. The liquid temperature of the alkaline solution is preferably in the range of room temperature to 90 ° C, more preferably 40 ° C to 70 ° C. In the alkali saponification treatment, the cellulose ester film is obtained by immersing in an alkali solution, generally washed with water, and then passing an acidic aqueous solution, followed by washing with water and surface treatment.

  At this time, the acidic aqueous solution is preferably an aqueous solution of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, formic acid, chloroacetic acid, oxalic acid, etc., and its concentration is preferably 0.01 mol / L to 3.0 mol / L. More preferably, it is 05 mol / L to 2.0 mol / L. The alkali saponification time is preferably 20 to 600 seconds, more preferably 30 to 300 seconds, and particularly preferably 40 to 210 seconds. The neutralization with an acidic solution is preferably carried out in 20 to 600 seconds, more preferably 30 to 250 seconds, and particularly preferably 40 to 180 seconds. Further, the water washing after neutralization is preferably carried out in 20 to 400 seconds, more preferably 30 to 300 seconds, and particularly preferably 40 to 210 seconds.

  The surface energy of the solid obtained by these methods should be determined by the contact angle method, the wet heat method, and the adsorption method as described in “Basics and Applications of Wetting” (Realize, 1989.12.10). It is preferable to use the contact angle method. The water contact angle (25 ° C./relative humidity 60%) of the cellulose ester film surface of the present invention is preferably 45 ° or less, more preferably 10 to 45 °, and particularly preferably 10 to 40 °. 10 to 30 ° is most preferable.

(Adhesive layer)
As a method of adhering the functional layer to the cellulose ester film of the present invention, after surface activation treatment, a method of directly applying the functional layer on the cellulose ester film to obtain adhesive force, and after some surface treatment Alternatively, there is a method in which an undercoat layer (adhesive layer) is provided and a functional layer is applied thereon without surface treatment. Various contrivances have been made for the constitution of the undercoat layer, for example, a single layer method in which one undercoat layer is composed of one layer, or a layer that adheres well to a support (cellulose ester film) as a first layer. There is a so-called multi-layer method in which an undercoat first layer is provided and an undercoat second layer that adheres well to the functional layer as a second layer is applied thereon.

  In the single layer method, the cellulose ester film is often expanded and interfacial mixed with the undercoat layer material to achieve good adhesion. Examples of the primer polymer used in the primer layer include water-soluble polymers, cellulose esters, latex polymers, and water-soluble polyesters. Examples of the water-soluble polymer include gelatin, gelatin derivatives, casein, agar, sodium alginate, starch, polyvinyl alcohol, polyacrylic acid copolymer, maleic anhydride copolymer, and the like as carboxymethyl cellulose, Examples thereof include hydroxyethyl cellulose. Examples of the latex polymer include a vinyl chloride-containing copolymer, a vinylidene chloride-containing copolymer, an acrylate ester-containing copolymer, a vinyl acetate-containing copolymer, and a butadiene-containing copolymer.

  In the first undercoat layer in the multi-layer method, for example, a copolymer starting from a monomer selected from vinyl chloride, vinylidene chloride, butadiene, methacrylic acid, acrylic acid, itaconic acid, maleic anhydride, etc. In addition, oligomers or polymers such as polyethyleneimine, epoxy resin, grafted gelatin, and nitrocellulose can be used. In the second undercoat layer, for example, the aforementioned water-soluble polymer, cellulose ester, latex polymer, water-soluble polyester, and the like can be used.

  In particular, when adhering to a polarizer, the cellulose ester film of the present invention is preferably provided with a hydrophilic binder layer comprising a hydrophilic binder. Examples of the hydrophilic binder include a -COOM group-containing vinyl acetate-maleic acid copolymer compound, a hydrophilic cellulose derivative (such as methyl cellulose, carboxymethyl cellulose, and hydroxyalkyl cellulose), and a polyvinyl alcohol derivative (such as vinyl acetate-vinyl). Alcohol copolymer, polyvinyl acetal, polyvinyl formal, polyvinyl benzal, etc.), natural polymer compounds (eg, gelatin, casein gum arabic, etc.), and hydrophilic group-containing polyester derivatives (eg, sulfone group-containing polyester copolymers).

The undercoat layer optionally applied to the cellulose ester film of the present invention can contain inorganic or organic fine particles as a matting agent to such an extent that the transparency of the functional layer is not substantially impaired. Silica (SiO ₂ ), titanium dioxide (TiO ₂ ), calcium carbonate, magnesium carbonate and the like can be used as the inorganic fine particle matting agent. Examples of the organic fine-particle matting agent include polymethyl methacrylate, cellulose acetate propionate, polystyrene, a treatment solution-soluble one described in US Pat. No. 4,142,894, and US Pat. No. 4,396,706. The polymers described in the specification can be used. The average particle size of these fine particle matting agents is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm. Moreover, the content is preferably 0.5 to 600 mg / m ² , more preferably 1 to 400 mg / m ² . The undercoat liquid may be a well-known coating method such as dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, slide coating, or the United States. It can apply | coat by the extrusion coat method which uses the hopper as described in patent 2,681,294.

(Conductive layer)
When producing a protective film for a polarizing plate using the cellulose ester film of the present invention, an antistatic layer is provided on at least one layer of the film, or a hydrophilic binder layer for adhering to a polarizer is provided. Is preferred.
First, the conductive layer will be described below. The conductive material contained in the conductive layer is preferably a conductive metal oxide or a conductive polymer. A transparent conductive film by vapor deposition or sputtering may be used. Examples of the conductive metal oxide include ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₂ , V ₂ O ₅ , or a composite oxide thereof. Are preferable, and ZnO, SnO ₂ or V ₂ O ₅ is particularly preferable. As examples of the hetero atoms of the composite oxide, addition of Al, In, Ta, Sb, Nb, halogen, and Ag is effective, and the addition amount is preferably in the range of 0.01 mol% to 25 mol%.

The volume resistivity of these conductive metal oxide powders is preferably 10 ⁷ Ω · cm or less, and particularly preferably 10 ⁵ Ω · cm or less. The primary particle size of the metal oxide powder is preferably 100 to 0.2 μm, and the conductive layer has a specific structure in which the major axis of the higher-order structure of these aggregates is 300 to 6 μm. It is preferable to contain the powder which has 0.01%-20% by a volume fraction. The amount of the conductive fine particles (metal oxide powder) is preferably 0.01~5.0g / m ^2, in particular 0.005~1g / m ² is preferred.

  The binder for dispersing the conductive fine particles is not particularly limited as long as it has a film-forming ability. Examples thereof include proteins such as gelatin and casein; carboxymethylcellulose, hydroxyethylcellulose, acetylcellulose, diacetylcellulose, Cellulose compounds such as acetylcellulose; sugars such as dextran, agar, sodium alginate, starch derivatives, polyvinyl alcohol, polyvinyl acetate, polyacrylic acid ester, polymethacrylic acid ester, polystyrene, polyacrylamide, poly-N-vinylpyrrolidone, polyester And synthetic polymers such as polyvinyl chloride and polyacrylic acid. Furthermore, as the conductive material, an organic electron conductive material is also preferable, and examples thereof include a polyaniline derivative, a polythiophene derivative, a polypyrrole derivative, and a polyacetylene derivative.

(Surfactant)
A surfactant is preferably used for forming a functional layer in the cellulose ester film of the present invention. The surfactant used for forming the functional layer in the present invention is classified into a dispersant, a coating agent, a wetting agent, an antistatic agent, etc. depending on the purpose of use, and the surfactant described below should be used appropriately. And those goals can be achieved. As the surfactant used in the present invention, either nonionic or ionic (anion, cation, betaine) can be used. Further, a fluorine-based low molecular surfactant is also preferably used as a coating agent or an antistatic agent in an organic solvent. The layer used may be a film made of cellulose ester, or any other functional layer. When used in optical applications, examples of functional layers include an undercoat layer, an intermediate layer, an orientation control layer, a refractive index control layer, a protective layer, an antifouling layer, an adhesive layer, a back undercoat layer, and a back layer. . The amount used is not particularly limited as long as it is an amount necessary to achieve the object, but generally 0.0001 to 5% by mass is preferable with respect to the total mass of the layer to be added, and further 0.0005 to 2%. Mass% is preferred. In this case, the coating amount of the surfactant is preferably 0.02 to 1000 mg, more preferably 0.05 to 200 mg per 1 m ² .

(Sliding layer)
Further, in the cellulose ester film of the present invention, a slipping agent may be contained in any layer applied on the film, and it is particularly preferred to contain it in the outermost layer. Examples of the slip agent used include polyorganosiloxanes as disclosed in JP-B-53-292; higher fatty acid amides as disclosed in US Pat. No. 4,275,146; Higher fatty acid esters (fatty acids having 10 to 24 carbon atoms) such as those disclosed in JP-A-58-33541, British Patent No. 927,446 or JP-A-55-126238 and 58-90633. And esters of alcohols having 10 to 24 carbon atoms); higher fatty acid metal salts as disclosed in U.S. Pat. No. 3,933,516; as disclosed in JP-A-58-50534 Esters of linear higher fatty acids and linear higher alcohols; as disclosed in WO 90 / 108115.8 Higher fatty acids containing an alkyl group - can be exemplified higher alcohol ester.
The sliding performance preferably has a static friction coefficient of 0.25 or less. The static friction coefficient is a value measured using a 5 mmφ stainless steel ball with a HEIDON-10 static friction coefficient measuring machine after conditioning the sample for 2 hours at a temperature of 25 ° C. and a relative humidity of 60%. Sex is good.

(Matting agent for functional layer)
In the functional layer of the cellulose ester film of the present invention, it is preferable to use a matting agent in order to improve the slipperiness of the film and the adhesion resistance under high humidity. In that case, the average height of the protrusions on the surface is preferably 0.005 to 10 μm, more preferably 0.01 to 5 μm. Further, it is better that there are many protrusions on the surface, but if there are more protrusions than necessary, the haze may deteriorate. As long as a preferable protrusion is a range having an average height of the protrusion, for example, it may be either spherical or indeterminate. When the projection is formed with the matting agent, the content is preferably 0.5 to 600 mg / m ² , and more preferably 1 to 400 mg / m ² . In this case, the matting agent used is not particularly limited in its composition, and may be an inorganic material, an organic material, or a mixture of two or more types, and the fine particles described above can be used.

(Other functional layers)
The cellulose ester film of the present invention can be provided with a transparent hard coat layer. As the transparent hard coat layer, an actinic radiation curable resin layer or a thermosetting resin layer is preferably used. The actinic radiation curable resin layer refers to a layer mainly composed of a resin (active radiation curable resin) that is cured through a crosslinking reaction or the like by irradiation with actinic rays such as ultraviolet rays or electron beams. Typical examples of the actinic radiation curable resin include an ultraviolet curable resin and an electron beam curable resin, but a resin that is cured by irradiation with actinic rays other than ultraviolet rays and electron beams may be used. Examples of the ultraviolet curable resin include an ultraviolet curable acrylic urethane resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, and an ultraviolet curable epoxy resin. Can be mentioned. In JP-A-2003-039014, the coated film is rolled and gripped in the width direction and dried, and a coating solution containing an actinic radiation curable substance is cured to have a high flatness. A technique is described and this technique is also applicable to the present invention.

  The cellulose ester film of the present invention can be provided with an antireflection layer to form an antireflection film. Various configurations such as a single layer and a multilayer are known as the configuration of the antireflection layer, but a multilayer structure having a structure in which a high refractive index layer and a low refractive index layer are alternately laminated is generally used. Examples of the configuration include a layer composed of two layers of a high refractive index layer / a low refractive index layer from the transparent substrate side, or three layers having different refractive indexes, a medium refractive index layer (transparent substrate or hard Layers with higher refractive index than the coating layer and lower refractive index than the high refractive index layer) / high refractive index layer / low refractive index layer, etc. Something to do is also proposed. Among these, from the viewpoint of durability, optical characteristics, cost, productivity, and the like, it is preferable to apply a high refractive index layer / medium refractive index layer / low refractive index layer in this order on a substrate having a hard coat layer.

  The cellulose ester film of the present invention can be provided with an antiglare layer. The antiglare layer has a structure containing fine particles in the layer in order to cause the antiglare function by scattering light on the surface of the antiglare layer or inside the antiglare layer by giving the surface an uneven structure. Yes. Preferred configurations for these layers are the embodiments shown below. The antiglare layer is preferably a layer having a film thickness of 0.5 to 5.0 μm and containing one or more kinds of fine particles having an average particle size of 0.25 to 10 μm. Further, the antiglare layer comprises silicon dioxide particles having an average particle size of 1.1 to 2 times the film thickness and silicon dioxide fine particles having an average particle size of 0.005 μm to 0.1 μm, such as diacetyl cellulose. It is a layer contained in such a binder, and can thereby exhibit an antiglare function. Examples of the particles used for the antiglare layer include inorganic particles and organic particles.

  The cellulose ester film of the present invention can be subjected to anti-curl processing. The anti-curl processing is to impart a function of rounding with the surface to which the curl is applied. In order to prevent the surface of the cellulose ester film of the present invention from being curled with some surface treatment applied to a different degree and type on both surfaces, the surface is inward. Apply preventive processing. The anti-curl processing can be performed, for example, on the side opposite to the side having the anti-glare layer or the anti-reflection layer, or on the opposite side when an easy-adhesion layer is applied on one side.

<< Use of Cellulose Ester Film of the Present Invention >>
The cellulose ester film of the present invention is combined with a functional layer described in detail on pages 32 to 45 of the Japan Institute of Invention Disclosure Technical Report (public technical number 2001-1745, issued on March 15, 2001, Japan Society of Invention). It is preferable to form various optical films. Among these, application of a polarizing film (polarizing plate), application of an optical compensation layer (optical compensation sheet), and application of an antireflection layer (antireflection film) are preferable.

(1) Application of polarizing film (production of polarizing plate)
Currently, a commercially available polarizing film is generally produced by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing the iodine or dichroic dye to penetrate into the binder. It is. Iodine and dichroic dye in the polarizing film exhibit polarizing performance by being oriented in the binder. The dichroic dye preferably has a hydrophilic substituent (for example, sulfo, amino, hydroxyl). For example, the compounds described in page 58 of the Japan Society of Invention Disclosure Technique (Public Technical No. 2001-1745, published on March 15, 2001, Japan Society of Invention).

  As the binder for the polarizing film, either a polymer that can be crosslinked per se or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used. As the binder, for example, a water-soluble polymer described in paragraph No. [0022] of JP-A-8-338913 (for example, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) is preferable. Gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127. The binder thickness is preferably 1 μm to 50 μm, more preferably 2 μm to 50 μm, and still more preferably 5 μm to 30 μm. Further, the binder of the polarizing film may be crosslinked. Crosslinkable boron compounds (for example, boric acid and borax) can also be used as a crosslinking agent. The addition amount of the crosslinking agent in the binder is preferably 0.1 to 20% by mass with respect to the binder.

  The polarizing film is preferably dyed with iodine or a dichroic dye after the polarizing film is stretched (stretching method) or rubbed (rubbing method). In the case of the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, more preferably 3.0 to 10.0 times. For the stretching, a parallel stretching method or a stretching method using a tenter projecting in an oblique direction described in JP-A-2002-86554 can be used. The saponified cellulose ester film and a polarizing film prepared by stretching are bonded to produce a polarizing plate. The direction in which the polarizing films are laminated is preferably 45 ° between the casting axis direction of the cellulose ester film and the stretching axis direction of the polarizing plate. Although the adhesive used when bonding a polarizing film and a cellulose-ester film is not specifically limited, For example, PVA-type resin (Including modified PVA, such as an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group) Examples thereof include a boron compound aqueous solution, and among them, a PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 μm to 10 μm, particularly preferably 0.05 μm to 5 μm after drying.

(2) Application of optical compensation layer (production of optical compensation sheet)
The optically anisotropic layer is for compensating for the liquid crystal compound in the liquid crystal cell in the black display of the liquid crystal display device, forms an alignment film on the cellulose ester film, and further provides an optically anisotropic layer. Is formed. An alignment film is provided on the surface-treated cellulose ester film. This film has a function of defining the alignment direction of liquid crystalline molecules. However, if the alignment state is fixed after aligning the liquid crystalline compound, the alignment film plays the role, and thus is not necessarily an essential component of the present invention. That is, it is possible to produce the polarizing plate of the present invention by transferring only the optically anisotropic layer on the alignment film in which the alignment state is fixed onto the polarizer. The alignment film is an organic compound (for example, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodget method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.

  As a method for applying the alignment film, a spin coating method, a dip coating method, a curtain coating method, an extrusion coating method, a rod coating method or a roll coating method is preferable, and a rod coating method is particularly preferable. The film thickness after drying is preferably 0.1 μm to 10 μm. Heating and drying can be performed at 20 ° C to 110 ° C. In order to form sufficient cross-linking, 60 ° C to 100 ° C is preferable, and 80 ° C to 100 ° C is particularly preferable. The drying time can be 1 minute to 36 hours, preferably 1 minute to 30 minutes. The pH is also preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, pH 4.5 to 5.5 is preferable, and 5 is particularly preferable. The thickness of the alignment film thus obtained is preferably in the range of 0.1 to 10 μm.

  Next, the liquid crystalline molecules of the optically anisotropic layer are aligned on the alignment film. Thereafter, as necessary, the alignment film polymer and the polyfunctional monomer contained in the optically anisotropic layer are reacted, or the alignment film polymer is crosslinked using a crosslinking agent. The liquid crystalline molecules used in the optically anisotropic layer include rod-like liquid crystalline molecules and discotic liquid crystalline molecules. The rod-like liquid crystal molecules and the disk-like liquid crystal molecules may be high-molecular liquid crystals or low-molecular liquid crystals, and further include those in which low-molecular liquid crystals are cross-linked and no longer exhibit liquid crystallinity.

(Rod-like liquid crystalline molecules)
The rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer. The rod-like liquid crystalline molecules are described in Chapters 4, 7, and 11 of the Chemical Chemistry of the Quarterly Chemical Review Vol. 22, Liquid Crystal Chemistry (1994), and the Liquid Crystal Device Handbook, 142th Committee of the Japan Society for the Promotion of Science. Is described in Chapter 3. The birefringence of the rod-like liquid crystalline molecule is preferably in the range of 0.001 to 0.7. The rod-like liquid crystalline molecules preferably have a polymerizable group in order to fix the alignment state. The polymerizable group is preferably a radical polymerizable unsaturated group or a cationic polymerizable group. Specifically, for example, the polymerizable group described in paragraphs [0064] to [0086] of JP-A-2002-62427, A polymerizable liquid crystal compound is mentioned.

(Discotic liquid crystalline molecules)
The discotic liquid crystalline molecule exhibits liquid crystallinity in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. Also included are compounds. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation. In the optically anisotropic layer formed from the discotic liquid crystalline molecules, the compound finally contained in the optically anisotropic layer does not need to be a discotic liquid crystalline molecule. Also included are compounds having a group that reacts with heat or light and, as a result, polymerized or cross-linked by reaction with heat or light, resulting in a high molecular weight and loss of liquid crystallinity.

  Preferred examples of the discotic liquid crystalline molecules are described in JP-A-8-50206. The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284. In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. A compound in which the discotic core and the polymerizable group are bonded via a linking group is preferable, whereby the orientation state can be maintained even in the polymerization reaction. Examples thereof include compounds described in paragraph numbers [0151] to [0168] of JP-A No. 2000-155216.

(Other composition of optically anisotropic layer)
The optically anisotropic layer uses a plasticizer, a surfactant, a polymerizable monomer, etc. in combination with the liquid crystalline molecules to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal molecules, etc. can do. It is preferable that the compound has compatibility with the liquid crystal molecules and can change the tilt angle of the liquid crystal molecules or does not inhibit the alignment.

(Formation of optically anisotropic layer)
The optically anisotropic layer can be formed by applying a coating liquid containing liquid crystalline molecules and, if necessary, a polymerization initiator described later and optional components on the alignment film. The thickness of the optically anisotropic layer is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, and most preferably 1 μm to 10 μm. The aligned liquid crystal molecules can be fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is preferred.

  It is also preferable to combine this optical compensation film and the above-mentioned polarizing film. Specifically, the optically anisotropic layer is formed by applying the coating liquid for the optically anisotropic layer as described above to the surface of the polarizing film. As a result, without using a polymer film between the polarizing film and the optically anisotropic layer, a thin polarizing plate having a small stress (strain × cross-sectional area × elastic modulus) associated with the dimensional change of the polarizing film is produced. . When the polarizing plate according to the present invention is attached to a large liquid crystal display device, an image with high display quality can be displayed without causing problems such as light leakage. The tilt angle of the polarizing film and the optical compensation layer may be stretched so as to match the angle formed by the transmission axis of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the LCD and the vertical or horizontal direction of the liquid crystal cell. preferable. A normal inclination angle is 45 °. Recently, however, devices that are not necessarily 45 ° have been developed for transmissive, reflective, and transflective LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted in accordance with the design of the LCD.

<Liquid crystal display device>
(General liquid crystal display device configuration)
The cellulose ester film of the present invention can be used in various applications. The cellulose ester film of the present invention is effective when used as an optical compensation sheet for liquid crystal display devices. When the film itself is used as an optical compensation sheet, the transmission axis of the polarizing element (described later) and the slow axis of the optical compensation sheet made of a cellulose ester film are arranged so as to be substantially parallel or perpendicular. Is preferred. Such an arrangement of the polarizing element and the optical compensation sheet is described in JP-A-10-48420. The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing element. An optical compensation sheet is arranged.

  The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 80 μm to 500 μm. The optical compensation sheet is a birefringent film for removing the coloration of the liquid crystal screen. The cellulose ester film itself of the present invention can be used as an optical compensation sheet. Further, the function may be imparted as an antireflection layer, an antiglare layer, a λ / 4 layer or a biaxially stretched cellulose ester film. In addition, in order to improve the viewing angle of the liquid crystal display device, the cellulose ester film of the present invention and a film exhibiting birefringence opposite to that (positive / negative relationship) may be used as an optical compensation sheet. The thickness range of the optical compensation sheet is the same as the preferable thickness of the cellulose ester film of the present invention described above.

  Examples of the polarizing film of the polarizing element include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. Any polarizing film is generally manufactured using a polyvinyl alcohol film. The protective film of the polarizing plate preferably has a thickness of 25 μm to 350 μm, and more preferably has a thickness of 40 μm to 200 μm. The liquid crystal display device may be provided with a surface treatment film. The functions of the surface treatment film include hard coat, anti-fogging treatment, anti-glare treatment and antireflection treatment. As described above, there has also been proposed an optical compensation sheet in which an optically anisotropic layer containing a liquid crystal (particularly a discotic liquid crystalline molecule) is provided on a support (Japanese Patent Application Laid-Open Nos. 3-9325 and 6-148429). Nos. 8-50206 and 9-26572). The cellulose ester film of the present invention can also be used as a support for such an optical compensation sheet.

(Optically anisotropic layer containing discotic liquid crystalline molecules)
The optically anisotropic layer is preferably a layer containing discotic liquid crystal molecules that are tilted and aligned. The angle formed by the disc surface of the discotic liquid crystal molecule and the support surface is preferably changed (hybrid orientation) in the depth direction of the optically anisotropic layer. The optical axis of the discotic liquid crystalline molecule exists in the normal direction of the disk surface. The discotic liquid crystalline molecule has birefringence in which the refractive index in the disc surface direction is larger than the refractive index in the normal direction of the disc surface. The discotic liquid crystalline molecules may be aligned substantially horizontally with respect to the support surface.

(VA type liquid crystal display device)
The cellulose ester film of the present invention is also effectively used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell. In the optical compensation sheet used for the VA liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the VA liquid crystal display device are determined by the optical properties of the optically anisotropic layer, the optical properties of the support, and the arrangement of the optically anisotropic layer and the support. . When two optical compensation sheets are used in the VA liquid crystal display device, the in-plane retardation of the optical compensation sheet is preferably in the range of −5 nm to 5 nm. Therefore, the in-plane retardation of the two optical compensation sheets is preferably 0 to 5 in absolute value.

  When one optical compensation sheet is used in the VA liquid crystal display device, it is preferable that the in-plane retardation of the optical compensation sheet be in the range of −10 nm to 10 nm. The cellulose ester film of the present invention may be imparted with optical characteristics corresponding to various VA cells so as to be in such an optical characteristic range. The range corresponds to the cell gap. In the single-sheet cellulose ester film, Re is usually 40 to 120 nm, preferably Re is 50 to 100 nm, and particularly 50 to 90 nm. Further, Rth is usually 160 to 300 nm, preferably Rth is 170 to 260 nm, particularly 180 to 240 nm. Further, when two optical compensation sheets are used in the VA liquid crystal display device, the cellulose ester film of the present invention may be provided with optical characteristics corresponding to various VA cells. The range corresponds to the cell gap, and in the double-type cellulose ester film, Re is usually 20 to 80 nm, preferably Re is 30 to 70 nm, and particularly 30 to 60 nm. Rth is usually 80 to 200 nm, preferably Rth is 90 to 180 nm, and particularly 95 to 165 nm.

(OCB type liquid crystal display device and HAN type liquid crystal display device)
The cellulose ester film of the present invention is also advantageously used as a support for an optical compensation sheet of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell. In the optical compensation sheet used for the OCB type liquid crystal display device or the HAN type liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the OCB type liquid crystal display device or the HAN type liquid crystal display device are also the optical properties of the optically anisotropic layer, the optical properties of the support, and the optically anisotropic layer and the support. Is determined by the arrangement of The cellulose ester film of the present invention may have optical properties corresponding to various OCB mode liquid crystal cells. In the range, Re is usually 20 nm to 100 nm, preferably Re is 30 nm to 80 nm, particularly 30 nm to 60 nm. Further, Rth is usually 150 nm to 300 nm, preferably Rth is 160 nm to 260 nm, particularly 170 nm to 250 nm.

(Other liquid crystal display devices)
The cellulose ester film of the present invention is also advantageously used as a support for an optical compensation sheet of an ASM type liquid crystal display device having an ASM (Axially Symmetric Alligned Microcell) mode liquid crystal cell. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a resin spacer whose position can be adjusted. Other properties are the same as those of the TN mode liquid crystal cell. The ASM mode liquid crystal cell and the ASM type liquid crystal display device are described in a paper by Kume et al. (Kume et al., SID 98 Digest 1089 (1998)). The cellulose ester film of the present invention may be used as a support for an optical compensation sheet of a TN type liquid crystal display device having a TN mode liquid crystal cell. TN mode liquid crystal cells and TN type liquid crystal display devices have been well known for a long time. The optical compensation sheet used for the TN liquid crystal display device is described in JP-A-3-9325, JP-A-6-148429, JP-A-8-50206, and JP-A-9-26572. For the optical compensation sheet for these various liquid crystal display devices, the cellulose ester of the present invention may have its optical characteristics within a desired range.

<< Measurement method and evaluation method >>
Below, it describes about the measuring method and evaluation method of a cellulose ester and a cellulose-ester film. The measurement values described in the present application are those measured by the method described below.

(Substitution degree of cellulose ester)
The substitution degree of the acyl group with respect to the hydroxyl group of cellulose was determined by ¹³ C-NMR by the method described in Carbohydr. Res. 273 (1995) 83-91 (Tezuka et al.).

(Degree of polymerization of cellulose ester)
About 0.2 g of cellulose ester that was completely dried and had a water content of 0.02% by mass or less was precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride: ethanol = 9: 1 (mass ratio). This was measured with an Ostwald viscometer for the number of seconds dropped at 25 ° C., and the degree of polymerization was determined by the following equation.
η _rel = T / T ₀
[Η] = ln (η _rel ) / C
DP = [η] / Km
[In the formula, T is the number of seconds that the sample is dropped, T ₀ is the number of seconds that the solvent is dropped, ln is the natural logarithm, C is the concentration (g / L), and Km is 6 × 10 ⁻⁴ . ]

(Residual sulfuric acid amount)
The sulfate group content of the cellulose ester was measured by ASTM D-817-96, oxidative decomposition / coulometric titration method, etc., and the amount was defined by the sulfur atom content.

(Residual metal amount)
The cellulose ester was incinerated and then quantified by ICP-MS analysis.

(Re and Rth)
After adjusting the cellulose ester film for 24 hours at 25 ° C. and 60% relative humidity, the film was measured at 25 ° C. and 60% relative humidity using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments). By measuring a retardation value at a wavelength of 590 nm from a direction inclined in increments of 10 ° from + 50 ° to −50 ° from the film surface normal with the vertical direction and slow axis as the rotational axis, the front retardation value is obtained. (Re) and the retardation value (Rth) in the film forming direction were calculated. Unless otherwise specified, Re and Rth refer to this value.

  At this time, it is necessary to input an assumed value of average refractive index and a film thickness. KOBRA 21ADH calculates nx, ny, and nz in addition to Rth (λ) (Nx means the refractive index in the direction where the value of the refractive index in the film surface is maximum, and Ny is perpendicular to the direction of Nx. Means the refractive index in the film plane in the direction of crossing. The average refractive index of 1.48 is used for cellulose acetate, but values of polymer films for typical optical applications other than cellulose acetate include cycloolefin polymer (1.52), polycarbonate (1.59), poly Values such as methyl methacrylate (1.49) and polystyrene (1.59) can be used. In addition, as an average refractive index value of an existing polymer material, a polymer handbook (John Wiley & Sons, Inc.) or a catalog value of a polymer film can be used. In addition, in the case of a material whose average refractive index is unknown, it can be measured using an Abbe refractometer. In this specification, λ is 590 ± 5 nm unless otherwise specified.

(Re and Rth fluctuations with humidity)
The cellulose ester film was measured at 25 ° C. and 10% relative humidity in the same manner as described above, and Re (relative humidity 10%) and Rth (relative humidity 10%) were determined. Further, these samples were similarly measured at 25 ° C. and a relative humidity of 80%, and Re (relative humidity 80%) and Rth (relative humidity 80%) were obtained. For each sample, humidity Re fluctuation and humidity Rth fluctuation were determined according to the following formula.
Humidity Re variation (% / relative humidity%) = [100 × {absolute value of difference between Re (relative humidity 80%) and Re (relative humidity 10%)} / Re (relative humidity 60%)] / 70
Humidity Rth fluctuation (% / relative humidity%) = [100 × {absolute value of difference between Rth (relative humidity 80%) and Rth (relative humidity 10%)} / Rth (relative humidity 60%)] / 70

(Re unevenness, Rth unevenness)
In each region of 10 m, 250 m, and 450 m in the length direction of the cellulose ester film, a total of 21 samples were prepared by sampling 7 locations every 20 cm from the end in the width direction. These samples were conditioned at 25 ° C. and 60% relative humidity for 3 hours, and Re and Rth were measured in the same environment. The difference between the maximum and minimum values obtained was defined as Re unevenness and Rth unevenness, respectively evaluated. The smaller the value, the smaller the optical characteristic variation and the better.

(Axis misalignment)
The cellulose ester film was cut out to 70 mm × 100 mm, and the axis deviation angle was measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments). 20 points were measured at equal intervals over the entire width in the width direction of the cellulose ester film, and the average value of absolute values was obtained. The range of the slow axis angle (axis deviation) is the measurement of 20 points at equal intervals over the entire width direction, and the difference between the average of the absolute value of the axis deviation and the average of the four points from the smaller absolute value. It is what took.

(Haze)
The cellulose ester film was cut into 40 mm × 80 mm, and measured according to JIS K-6714 using a haze meter (HGM-2DP, manufactured by Suga Test Instruments Co., Ltd.) at 25 ° C. and a relative humidity of 60%.

(Transmittance)
The cellulose ester film was cut into a size of 20 mm × 70 mm, and the transmittance of visible light (615 nm) was measured at 25 ° C. and a relative humidity of 60% using a transparency measuring device (AKA photoelectric tube colorimeter, KOTAKI Corporation).

(Daisy)
Evaluation of the die stripe generated in a streak shape in the casting direction (length direction) of the cellulose ester film was performed by visual observation under a reflected light source. The evaluation criteria were as follows.
A: Dice lines were not seen.
B: Dice lines were slightly seen.
C: Dice lines were clearly recognized.
D: Dice lines were remarkably generated on the entire surface.

(Scratched)
The cellulose ester film was visually observed, and scratches were evaluated according to the following evaluation criteria.
A: No damage was observed.
B: Slight damage was observed.
C: The damage was considerably recognized.
D: Significant damage was observed.

(Increased coloring)
The cellulose ester film was conditioned at 25 ° C. and a relative humidity of 60% for 4 hours. Then, it cut | judged to 5 cm in diameter, was quickly put into the aluminum tray of 5 cm in diameter, and heated at 240 degreeC in the air in the muffle furnace for 1 hour. After cooling, 0.2 g of the sample was dissolved in methylene chloride so that the total volume became 10 ml, to prepare a 2 mass% solution, and the absorbance at 400 nm was measured. Also for the sample before heating, a 2 mass% methylene chloride solution was prepared and the absorbance at 400 nm was measured, and the increase in absorbance before and after heating was evaluated as the increase in coloration. It shows that it is a film with favorable thermal stability, so that a numerical value is small.

(Alkaline hydrolyzable)
A cellulose ester film was cut into 100 mm × 100 mm, saponified with a 2 mol / L sodium hydroxide aqueous solution at 60 ° C. for 3 minutes with an automatic alkali saponification treatment apparatus (manufactured by Shinto Kagaku Co., Ltd.), and washed with water for 4 minutes. The solution was neutralized with 0.01 mol / L dilute nitric acid at 30 ° C. for 4 minutes and washed with water for 4 minutes. Thereafter, drying was performed at 100 ° C. for 3 minutes, followed by natural drying for 1 hour, and the alkali hydrolyzability was evaluated from the following visual standard and haze values before and after the saponification treatment (25 ° C., relative humidity 60%).
A: No whitening was observed.
B: Slight whitening was observed.
C: Fair whitening was observed.
D: Remarkable whitening was observed.

(Curl value)
A cellulose ester film was cut into a size of 35 mm × 3 mm and conditioned for 24 hours at a relative humidity of 25%, 55%, and 85% in a curled humidity tank (HEIDON (No. YG53-168), manufactured by Shinto Kagaku Co., Ltd.). The curvature radius was measured with a curl plate. In addition, curling with wet was measured after standing for 30 minutes in water at a water temperature of 25 ° C.

(Kishimi value)
Cellulose ester films were cut into 100 mm × 200 mm and 75 mm × 100 mm, conditioned for 2 hours under conditions of 25 ° C. and 60% relative humidity, and using a Tensilon tensile tester (RTA-100, manufactured by Orientec Co., Ltd.) A large film sample was fixed on a table, and a small film sample with a 200 g weight was placed thereon. Then, the weight was pulled in the horizontal direction, the force at the start of movement and the force at the time of movement were measured, and the static friction coefficient and the dynamic friction coefficient were calculated, respectively, to obtain the apparent and dynamic kimi values.
F = μ × W (F: Kishimi value, μ: friction coefficient, W: weight of weight (kgf))

(Moisture content)
The cellulose ester film was cut into a size of 7 mm × 35 mm, and measured by the Karl Fischer method using a moisture meter and a sample drying apparatus (CA-03, VA-05, both Mitsubishi Chemical Corporation). It was calculated by dividing the amount of water (g) by the sample mass (g).

(Residual solvent amount)
The cellulose ester film was cut out to 7 mm × 35 mm, and the amount of base residual solvent was measured using gas chromatography (GC-18A, manufactured by Shimadzu Corporation).

(Heat shrinkage)
A cellulose ester film is cut out to 30 mm × 120 mm and aged for 24 hours and 120 hours at 90 ° C. and 5% relative humidity. With an automatic pin gauge (manufactured by Shinto Kagaku Co., Ltd.), 6 mmφ holes at both ends are spaced at 100 mm intervals. Opened, the original size (L1) of the interval was measured to a minimum scale of 1/1000 mm. Further, heat treatment was performed at 90 ° C. and 5% relative humidity for 24 hours and 120 hours, and the dimension (L2) of the punch interval was measured. The thermal contraction rate was determined by {(L1-L2) / L1} × 100.

(Moisture permeability coefficient)
Cellulose ester film (70 mmφ) was conditioned at 25 ° C./90% relative humidity and 40 ° C./90% relative humidity for 24 hours, respectively. The amount of water per unit area (g / m ² ) was calculated according to Z-0208. And the water vapor transmission rate was calculated | required by the mass before humidity-mass before humidity control. Further, as a compulsory evaluation, the moisture permeability coefficient was measured after conditioning for 24 hours at 60 ° C. and 95% relative humidity.

(Foreign substance inspection)
Reflected light was applied to a range of the total width of the cellulose ester film × 1 m and foreign matter in the film was visually detected, and then the foreign matter (lint) was confirmed and evaluated with a polarizing microscope.

(Elastic modulus)
Using a universal tensile tester STM T50BP manufactured by Toyo Baldwin, the stress at 0.5% elongation was measured in an atmosphere of 23 ° C. and a relative humidity of 70% at a pulling rate of 10% / min to obtain an elastic modulus.

(Measurement of bright spot foreign matter)
Two polarizing plates were arranged in an orthogonal state (crossed Nicols) to block transmitted light, and a cellulose ester film was placed between the two polarizing plates. The polarizing plate used was a glass protective plate. Light was irradiated from one side, and the number of bright spots corresponding to the diameter per cm ² was counted with an optical microscope (50 times) from the opposite side.

(Measurement of Tg)
20 mg of a sample was placed in a DSC measurement pan. This was heated to 30 ° C. to 250 ° C. at 10 ° C./min in a nitrogen stream, and then cooled to −30 ° C. at −10 ° C./min. Thereafter, the temperature was raised again to 30 ° C. to 250 ° C., and the temperature at which the baseline started to deviate from the low temperature side was defined as Tg.

(Tensile strength, elongation rate)
A sample of 15 mm × 250 mm was conditioned at 23 ° C. and relative humidity of 65% for 2 hours, and an initial sample length of 100 mm and a tensile speed of 200 according to ISO1184-1983 using a Tensilon tensile tester (RTA-100, Orientec Co., Ltd.). The elastic modulus was calculated from the stress and elongation at the initial stage of tension at ± 5 mm / min, and the tensile strength, stretching force, and elongation at break were evaluated.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

Synthesis Example 1 Synthesis of Cellulose Acetate Propionate 150 parts by mass of cellulose derived from hardwood pulp and 75 parts by mass of acetic acid were placed in a reaction vessel equipped with a cooling device and a reflux device and stirred for 4 hours while heating at 60 ° C. did. The reaction vessel was cooled to 2 ° C. Separately, a mixture of 1545 parts by weight of propionic acid anhydride and 10.5 parts by weight of sulfuric acid was prepared as an acylating agent, cooled to −20 ° C., and then put into a reaction vessel containing the above pretreated cellulose at once. added. After 30 minutes, the external temperature was gradually increased, and after 2 hours from the addition of the acylating agent, the internal temperature was adjusted to 25 ° C., and the internal temperature was kept at 25 ° C. and further stirred for 3 hours. The reaction vessel was cooled in an ice water bath at 5 ° C., and 120 g of 25% by mass hydrous acetic acid cooled to 5 ° C. was added over 1 hour. The internal temperature was raised to 40 ° C. and stirred for 2.5 hours. Next, a solution obtained by dissolving magnesium acetate tetrahydrate corresponding to twice the mole of sulfuric acid in 50% by mass of hydrous acetic acid was added to the reaction vessel, and the mixture was stirred for 30 minutes. 25% by mass hydrous acetic acid, 33% by mass hydrous acetic acid, 50% by mass hydrous acetic acid and water were added in this order to precipitate cellulose acetate propionate. The obtained cellulose acetate propionate precipitate was washed with warm water. After stirring in a 0.005 mass% calcium hydroxide aqueous solution at 20 ° C. for 0.5 hour, the solution was removed and vacuum dried at 70 ° C.
According to ¹ H-NMR and GPC measurement, the obtained cellulose acetate propionate had an acetyl substitution degree of 0.30, a propionyl substitution degree of 2.63, and a number average polymerization degree of 170.

[Synthesis Example 2] Synthesis of cellulose acetate butyrate 100 parts by weight of cellulose (hardwood pulp) and 135 parts by weight of acetic acid were placed in a reaction vessel equipped with a cooling device and a reflux device and stirred for 4 hours while heating at 60 ° C. . The reaction vessel was cooled to 2 ° C. Separately, a mixture of 1080 parts by weight of butyric anhydride and 10.0 parts by weight of sulfuric acid was prepared as an acylating agent, cooled to −20 ° C., and then added to the reaction vessel containing the pretreated cellulose at once. It was. After 30 minutes, the external temperature was raised to 20 ° C. and reacted for 5 hours. The reaction vessel was cooled in an ice water bath at 5 ° C., and 2400 g of 12.5% by mass aqueous acetic acid cooled to about 5 ° C. was added over 1 hour. The internal temperature was raised to 40 ° C. and stirred for 2 hours. Next, a solution obtained by dissolving magnesium acetate tetrahydrate corresponding to twice the mole of sulfuric acid in 50% by mass of hydrous acetic acid was added to the reaction vessel, and the mixture was stirred for 30 minutes. 25% by mass aqueous acetic acid, 33% by mass aqueous acetic acid, 50% by mass aqueous acetic acid and water were added in this order to precipitate cellulose acetate butyrate. The obtained cellulose acetate butyrate precipitate was washed with warm water. After washing, the mixture was stirred in a 0.005 mass% calcium hydroxide aqueous solution for 0.5 hour, and then drained and dried at 70 ° C. under reduced pressure. The obtained cellulose acetate butyrate had an acetyl substitution degree of 0.84, a butyryl substitution degree of 2.12, and a number average polymerization degree of 205.

[Synthesis Example 3] Synthesis of Other Cellulose Esters Other cellulose acetate propionate and cellulose acetate butyrate were prepared from the methods of Synthesis Examples 1 and 2 depending on the desired degree of substitution and degree of polymerization. The same synthesis was carried out by changing the reaction temperature and time of acylation and the temperature and time of partial hydrolysis.

Synthesis Example 4 Synthesis of Cellulose Mixed Ester Cellulose acylating agent (acetic acid, acetic anhydride, propionic acid, propionic acid anhydride, butyric acid, butyric anhydride, alone or in combination depending on the desired degree of acyl substitution Acylation was carried out while mixing the sulfuric acid as the catalyst and keeping the reaction temperature at 40 ° C. or lower. After the cellulose as a raw material disappeared and acylation was completed, heating was further continued at 40 ° C. or lower to adjust to a desired degree of polymerization. After adding an acetic acid aqueous solution to hydrolyze the remaining acid anhydride, partial hydrolysis was performed by heating at 60 ° C. or lower, and the desired total substitution degree was adjusted. The remaining sulfuric acid was neutralized with an excess amount of magnesium acetate. Reprecipitation was performed from an aqueous acetic acid solution, and further washing with water was repeated to prepare cellulose esters having different acyl groups and different degrees of substitution shown in Table 2.

[Example 1]
(1) Preparation of cellulose ester mixture pellets As cellulose ester, cellulose ester A (acetyl substitution degree 0.45, propionyl substitution degree 2.40, total substitution degree 2.85, viscosity average polymerization degree 170, water content 0.1 mass %, A powder having a viscosity of 140 mPa · s of 6% by mass in a dichloromethane solution, an average particle size of 1.2 mm, a standard deviation of 0.3 mm, a bulk specific gravity of 0.21, and a true specific gravity of 1.22. Cellulose ester A is synthesized from cellulose collected from cotton linter as a raw material. Furthermore, cellulose ester A has a residual acetic acid amount of 0.02% by mass, a residual propionic acid amount of 0.01% by mass, a Ca content of 51 ppm, a Mg content of 15 ppm, and a Fe content of 0.45 ppm. In addition, the amount of sulfur as a sulfate group was 0.16 ppm.

  The substitution degree of the acetyl group with respect to the hydroxyl group at the 6-position was 0.15, and the substitution degree of the propionyl group with respect to the hydroxyl group at the 6-position was 0.79, which was 33.3% of the total acetyl. The mass average molecular weight / number average molecular weight ratio was 2.8. Cellulose ester A was formed into a solution on a glass plate using methylene chloride / methanol = 90/10 (mass ratio) to obtain a film having a thickness of 80 μm, and its basic characteristics were examined. That is, the yellow index of a film composed only of cellulose ester A is 0.82, haze is 0.1, transmittance is 93.8%, and Tg (glass transition temperature; measured by DSC) is 137 ° C. It was.

  This cellulose ester A was dried at 105 ° C. for 5 hours to adjust the water content to 0.07% by mass. To the dried cellulose ester A, an ultraviolet absorber having the following structure was added in an amount of 1.0% by mass with respect to the cellulose ester A. Further, silica particles having an average primary particle size of 1.2 μm (the mass abundance ratio of particles of 0.9 to 1.5 μm is 95% or more, and the mass abundance ratio of particles of 1.5 μm or more is 1.0%. 0.05% by mass with respect to cellulose ester A was added. Further stabilizers were added according to Table 1.

(2) Filtration and pelletization The mixture to which these additives were added was stirred and mixed with a Henschel mixer (manufactured by Mitsui Miike Seisakusho Co., Ltd.) to obtain a uniform cellulose ester mixture. Using this cellulose ester mixture, pellets were prepared by the following extruder (all the steps were filled with a nitrogen stream). That is, the cellulose ester mixture was put into a hopper of a twin-screw kneading extruder, and further kneaded and melted at 180 to 220 ° C. with a screw rotation speed of 300 rpm and a residence time of 40 seconds. Filtration was performed by pressure filtration using a sintered metal filter with a diameter of 5 μm installed just before the die.

  Further, the filtered melt was extruded from a nozzle having a diameter of 2.5 mm at an extrusion portion, and extruded from a die at a rate of 200 kg / hour in a strand shape of a diameter of 3 mm in a warm water bath at 40 ° C. to 80 ° C. within 3 seconds. After soaking for 30 seconds (strand solidification), the temperature was lowered by passing water at 10 ° C. to 30 ° C. for 30 seconds, and the pellet was obtained by cutting to 3 mm in diameter and 2 to 6 mm in length (mostly 3 mm) . The obtained cellulose ester pellets were dried at 105 ° C. for 3 hours under a nitrogen atmosphere, and then packed in a moisture-proof bag made of a laminate film having aluminum under a nitrogen atmosphere. Oxygen was blocked and stored. The obtained pellets had a transparent and homogeneous composition.

(3) Melt film formation Next, the cellulose ester pellets produced above were put into a hopper adjusted to 107 ° C, an upstream melting temperature of 195 ° C, an intermediate melting temperature of 210 ° C, a downstream melting temperature of 225 ° C, Compression ratio 14, T-die temperature 225 ° C., distance between T-die and casting drum 8 cm, solidification rate 30 ° C./second, casting drum temperature as first roll (upstream) 100 ° C., second roll (upstream) 99 ° C. The third roll (upstream) was treated at 98 ° C. and a cooling rate of −15 ° C./second. The melt was melt extruded over 10 minutes. At this time, an electrostatic application method (a 10 kV wire was placed 10 cm from the point where the melt was attached to the casting drum) was used. The solidified melt was peeled off and wound with a winding tension of 6 kg / cm ² via a nip roll. In addition, after trimming both ends (each 3% of the total width) immediately before winding, and after applying thickness processing (knurling) of 10 mm width and 50 μm height to both ends, a film with a width of 1.5 m was 30 m / min. 500 m was wound up. The above melt film formation was performed under the condition of an oxygen concentration of 5% by volume or less. The film thickness of each film is as described in Table 1. The residual solvent amount was zero.

(4) Evaluation Table 1 summarizes the results of measurement and evaluation of Re, Rth, Re unevenness, Rth unevenness, die stripe, transmittance, and coloring increase of each cellulose ester film.
The control sample 1-1 that did not contain any of the phenol-based stabilizer, the phosphite-based stabilizer, and the thioether-based stabilizer had extremely poor Re unevenness, Rth unevenness, dice, and transmittance.
Further, Comparative Sample 1-2 containing only one of a phenol stabilizer having a molecular weight of 500 or more, or a stabilizer selected from the group consisting of a phosphite stabilizer and a thioether stabilizer having a molecular weight of 500 or more. -Sample 1-7 had insufficient Re unevenness, Rth unevenness, die streak and transmittance.

Furthermore, Comparative Samples 1-18 to 1-31 in which the molecular weight of any one of the stabilizers selected from the group consisting of phenol stabilizers, phosphite stabilizers and thioether stabilizers is less than 500 are: , Re unevenness, Rth unevenness, die streak and transmittance were slightly improved, but the improvement level was insufficient.
Furthermore, although it contains both a phenol-based stabilizer having a molecular weight of 500 or more and a stabilizer selected from the group consisting of a phosphite-based stabilizer and a thioether-based stabilizer having a molecular weight of 500 or more, melt film formation Comparative Samples 1-16 and 1-17 whose temperature was outside the range of the present invention were insufficient in Re unevenness, Rth unevenness, die streak and transmittance.

  On the other hand, Samples 1-8 to 1-15 of the present invention have satisfactory levels of Re unevenness, Rth unevenness, die stripes and transmittance, and an excellent cellulose ester film can be obtained according to the present invention. It was. Furthermore, Samples 1-8 to 1-15 of the present invention were all excellent in haze of 0.3% or less. Also, the humidity dependence of Re {the difference between Re (relative humidity 80%) and Re (relative humidity 10%) at 25 ° C.) is 5 nm or less, and the humidity dependence of Rth {Rth (relative humidity at 25 ° C.) 80%) and Rth (relative humidity 10%)} were all 20 nm or less, which was excellent. Further, the wavelength dispersion characteristics were | Re (700) −Re (400) | within 8 nm and | Rth (700) −Rth (400) | within 30 nm.

  In particular, Comparative Sample 1-17 melted and formed at 245 ° C., which is the melting temperature listed in the examples of Patent Document 2 (Japanese Patent Laid-Open No. 2000-352620), has Re and Rth at the melting temperature of the present invention. The film was significantly larger than the sample 1-8 of the present invention formed, the die streak was remarkably poor, and the film was not suitable for practical use with a significant deterioration in transmittance and an increase in coloring increase. The phenol stabilizer PH-2 and the phosphite stabilizer PF-5 used in the representative sample 1-8 of the present invention are masses when heated at 220 ° C. for 30 minutes in nitrogen. Both reductions were 20% by mass or less. In contrast, the phenol stabilizer (comparative AF-1) having a molecular weight of less than 500 and the phosphite stabilizer (comparative PA-1) used in Comparative Sample 1-30 were heated at 220 ° C. for 30 minutes in nitrogen. In this case, the mass was reduced to more than 20% by mass and 30% by mass or less.

  From the above, according to the present invention, at least one selected from the group consisting of at least one phenolic stabilizer having a molecular weight of 500 or more, a phosphite stabilizer having a molecular weight of 500 or more, and a thioether stabilizer having a molecular weight of 500 or more. It was confirmed that an excellent optical film can be produced by appropriately containing a stabilizer and performing melt film formation at an appropriate temperature. Samples 1-8 to 1-15 of the present invention have a residual acetic acid content of less than 0.01% by mass, a Ca content of less than 0.05% by mass, and a Mg content of less than 0.01% by mass. Met. Further, the film had a longitudinal and transverse average heat shrinkage (80 ° C./relative humidity 90% / 48 hours) of −0.06%, and was a film in which heat shrinkage hardly occurred. Furthermore, Sample 1-8 to Sample 1-15 of the present invention also have an increase in coloring of 0.02% or less, which is very superior to that of Control Sample 1-1, which is 0.15. confirmed.

Here, as a representative of the film sample of the present invention, Sample 1-8 has an inclination width of 19.4 nm, a critical wavelength of 389.2 nm, an absorption edge of 376.1 nm, and an absorption at 380 nm of 1.1%. (Molecular orientation axis) is 0.12 °, elastic modulus is 2.95 GPa in the longitudinal direction, 2.94 GPa in the width direction, tensile strength is 119 MPa in the longitudinal direction, 108 MPa in the width direction, elongation is 62% in the longitudinal direction, width The direction was 67%, the alkali hydrolyzability was A, and the curl value was -0.3 at a relative humidity of 25%, and 1.0 when wet. The moisture content was 1.7% by mass, and the thermal shrinkage was -0.05% in the longitudinal direction and -0.07% in the width direction. The foreign matter had a lint of less than 5 pieces / m. Further, the bright spot is less than 10/3 m for 0.02 mm or less, less than 4/3 m for 0.02-0.05 mm, not more than 0.05 mm, the kishimi value is 0.57, and the arithmetic average roughness The thickness was 150 nm, the scratch was A rank, and there was no problem in handling. Further, no adhesion was observed after application, and the moisture permeability coefficient (550 g / m ² · day) was also good. Other samples of the present invention also showed characteristic values almost equivalent to those of Sample 1-8.

[Example 2]
Cellulose ester A in sample 1-8 of the present invention of Example 1 was converted to cellulose ester B (acetyl substitution degree 0.8, propionyl substitution degree 1.95, total substitution degree 2.75, viscosity average polymerization degree 150, water content 0 .15% by weight, 6% by weight viscosity in dichloromethane solution 59 mPa · s, powder having an average particle size of 1.5 mm and a standard deviation of 0.5 mm) and completely the same as Sample 1-8 of Example 1 Similarly, Sample 2-1 of the present invention was produced. Further, cellulose ester A was converted to cellulose ester C (acetyl substitution degree 1.80, propionyl substitution degree 1.05, total substitution degree 2.85, viscosity average polymerization degree 180, water content 0.1 mass%, 6 mass in dichloromethane solution. Sample 2 of the present invention in exactly the same way as Sample 1-8 of Example 1 except that the powder was changed to a powder having a viscosity of 91 mPa · s and an average particle size of 1.2 mm and a standard deviation of 0.4 mm. -2 was produced.
Table 1 shows the results of the same evaluation as in Example 1 for these samples.

  Sample 2-1 of the present invention is a little smaller in degree of polymerization, but also has small Re and Rth, small Re unevenness and Rth unevenness, small dice, transmittance and increase in coloring, and is excellent in all. It was. Sample 2-2 of the present invention is a cellulose ester having a small number of propionyl groups, but also has good die lines and excellent optical properties (re unevenness, Rth unevenness), dice lines, transmittance, and increased coloring. It was a thing. From the above, in the present invention, it was confirmed that the degree of polymerization of the cellulose ester and the practical allowable range of the substituent are wide.

[Example 3]
Sample 1-8 of the present invention of Example 1 was alkali saponified under the following conditions. The film is immersed in a 3 mol / L NaOH aqueous solution heated to 65 ° C. for 2 minutes, washed with water at 25 ° C. for 30 seconds, and then treated with a 0.05 mol / L sulfuric acid aqueous solution (25 ° C.) for 1 minute. And washed again with water at 25 ° C. When the contact angle (relative to pure water) of the obtained alkali-saponified film was measured, it was 30 ° and the wettability was good. The contact angle before the alkali saponification treatment was 67 °, and it was found that the sample of the present invention has excellent surface treatment suitability for the alkali saponification treatment. A 10 ml / m ² aqueous solution of PVA / glutaraldehyde (5% by mass / 0.2% by mass) was applied onto these films, and a commercially available polarizing film (HLC2-5618, manufactured by Sanlitz) was applied to the film at 70 ° C. For 1 hour and left at 30 ° C. for 6 days.

  The resulting membrane with a cellulose ester film was imparted at right angles to the cellulose ester film side with a grid knife-like cut having a depth of 200 μm at a 45 ° angle with a cutter knife. Nichiban cello tape No. 405 (cello tape: registered trademark) and Nitto tape (PET tape) adhered firmly to the entire surface of the scar and left for 30 minutes, and the edges were peeled off at right angles. As a result, the unsaponified cellulose ester film was peeled off from all the grid-like cellulose ester films, but in the polarizing film provided with the saponified cellulose ester film, the cellulose ester film was peeled off from any tape. It was not seen at all. From the above, it can be seen that the cellulose ester film of the present invention has excellent polarizing film properties.

[Example 4]
Next, examples in which the cellulose ester film is applied to a polarizing plate and the like will be described.
(4-1) Preparation of Polarizing Plate (1) Saponification of Cellulose Ester Film N, N ′, N ″ -Tri-m-toluyl-1,3,5-triazine-2,4,6-triamine is converted to cellulose ester A 4% by mass to the solution is cast, and a cellulose triacetate film (Re is 60 nm, Rth is 200 nm, film thickness is 80 μm) is stretched 1.32 times in the width direction during drying in the presence of residual solvent. The cellulose triacetate film and the cellulose ester film sample 1-8 of Example 1 were saponified by the following method, that is, after dissolving KOH to 1.5 mol / L, 60 ° C. those whose temperature had been adjusted two was used as a saponifying solution. then, 10 g / m ² was coated on the 60 ° C. cellulose ester film was saponified for 1 minute. Thereafter, 50 ° C. By spraying the warm water, and washed sprayed 10 liters / m 1 minute ^2-minutes. Thereafter, sends 110 ° C. in dry air at wind speed 15 m / sec, and dried for 5 minutes. The saponification, a roll of film The saponified film of the obtained cellulose ester film of the present invention was designated as Sample 4-1, and the saponified film of the cellulose triacetate film was designated as Sample 4-2.

(2) Production of Polarizing Film According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, a polarizing film having a thickness of 20 μm was prepared by giving a peripheral speed difference between two pairs of nip rolls and stretching in the longitudinal direction.

(3) Bonding After the obtained polarizing film was sandwiched between the saponified cellulose ester film sample 4-1 and the stretched and saponified cellulose triacetate film sample 4-2, PVA (manufactured by Kuraray Co., Ltd.) (PVA-117H) Using a 3% aqueous solution as an adhesive, a polarizing plate was prepared such that the polarizing axis and the longitudinal direction of the cellulose ester film samples 4-1 and 4-2 were 90 ° (polarizing plate sample 4- 3). Among them, the cellulose ester film sample 4-1 of the present invention and the stretched and saponified cellulose triacetate film sample 4-2 are formed as a 20-inch VA liquid crystal display device described in FIGS. 2 to 9 of JP-A-2000-154261. Then, after mounting at 25 ° C and 60% relative humidity, bring it into 25 ° C and 10% relative humidity, and visually evaluate the magnitude of the color change with a 10-level evaluation (the larger the value, the larger the change). The area where display unevenness occurred was visually evaluated, and the ratio (%) where display unevenness occurred was determined. As a result, the display unevenness of the cellulose ester film of the present invention was 5% or less, which was very excellent. Further, according to Example 1 of JP-A-2002-86554, the cellulose ester film of the present invention is similarly used for a polarizing plate stretched using a tenter so that the stretching axis is at an angle of 45 ° with respect to the absorption axis. Although it was fabricated, good results were obtained as described above.

(4-2) Preparation of optical compensation film Instead of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-11-316378, the saponified cellulose ester film sample 4-1 of the present invention was used. Then, after attaching this to the bend alignment liquid crystal cell described in Example 9 of JP-A-2002-62431 at 25 ° C. and 60% relative humidity, it is brought into 25 ° C. and 10% relative humidity, The change in contrast was visually evaluated, and the color change was evaluated on a 10-point scale (the larger the change, the greater the change). Good performance was obtained by carrying out the present invention.

(4-3) Production of Low Reflective Film The cellulose ester film of the present invention was prepared by applying the cellulose ester film of the present invention according to Example 47 of the Japan Institute of Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Invention Association). When a low reflection film was produced using the ester film sample 1-8, good optical performance was obtained.

[Example 5]
The cellulose ester film sample 1-11 of the present invention produced in Example 1 was used in place of the cellulose triacetate film sample 1301 in Example 13 described in JP-A-2002-265636. Then, an optically anisotropic layer and a polarizing plate sample were prepared in exactly the same manner as in Example 13 described in JP-A No. 2002-265636, thereby preparing a bend alignment liquid crystal cell. The obtained liquid crystal cell had excellent viewing angle characteristics.

[Example 6]
Instead of the cellulose triacetate film sample 1401 in Example 14 described in JP-A-2002-265636, the cellulose ester film sample 1-13 of the present invention produced in Example 1 was used. Then, an optically anisotropic layer and a polarizing plate sample were prepared in exactly the same manner as in Example 14 described in JP-A No. 2002-265636 to prepare a TN type liquid crystal cell. The obtained liquid crystal cell had excellent viewing angle characteristics.

[Example 7]
(1) Mounting on VA panel The polarizing plate produced in Example 4 of the present invention is a backlight side polarizing plate so that the viewing side polarizing plate is 26 "wide and the absorption axis of the polarizer is long. The polarizer was punched into a rectangle so that the absorption axis of the polarizer had a short side.The front and back polarizing plates and the phase difference plate of the VA mode liquid crystal TV (manufactured by Sony Corporation, KDL-L26RX2) were peeled off. A polarizing plate (polarizing plate sample 4-3) prepared by using the cellulose ester film of the present invention was attached to the back side and attached to prepare a liquid crystal display device.After attaching the polarizing plate, 50 ° C., 5 kg / cm. ^At this time, the absorption axis of the polarizing plate on the viewing side is in the horizontal direction of the panel, the absorption axis of the polarizing plate on the backlight side is in the vertical direction of the panel, and the adhesive material surface is on the liquid crystal cell side Protect fill Then, using a measuring instrument (EZ-Contrast 160D, manufactured by ELDIM), a viewing angle (contrast ratio of 10 or more) was calculated from the luminance measurement of black display and white display. Even when it was used, good viewing angle characteristics with polar angles of 80 ° or more were obtained in all directions, and it was confirmed that there was no problem by conducting a light leakage and polarizing plate peeling test by a durability test. Is as follows.

1) Hold in an environment of 60 ° C and 90% relative humidity for 200 hours, take out in an environment of 25 ° C and 60% relative humidity, and display the liquid crystal display device in black 24 hours later, light leakage strength and peeling of the polarizing plate from the liquid crystal panel The presence or absence of was evaluated.
2) Hold in an environment of 80 ° C. and relative humidity of 10% or less for 200 hours, take out into an environment of 25 ° C. and relative humidity of 60%, and display the liquid crystal display device black after 1 hour. The presence or absence of peeling was evaluated.

[Example 8]
The sample of the present invention was prepared on an optically anisotropic film exhibiting desired optical characteristics, and the following commercially available monitors of different liquid crystal modes or retardation films of televisions were peeled off to produce the sample of the present invention produced in (4-2) above. When an optical compensation film was attached and the viewing angle characteristics thereof were examined, an excellent wide viewing angle characteristic and color were obtained, and it was confirmed that the cellulose ester of the present invention was useful.

(TN mode)
Both the viewing-side polarizing plate and the backlight-side polarizing plate were punched into a rectangle so that the absorption axis was 45 ° long with respect to the long side of the punched polarizing plate having a size of 17 ″. TN mode liquid crystal The front and back polarizing plates and the retardation plate of the monitor (Samson, SyncMaster 172X) were peeled off, and the polarizing plates made of the cellulose ester of the present invention were attached to the front and back sides in combination to produce a liquid crystal display device. After pasting, the film was held for 20 minutes at 50 ° C. and 5 kg / cm ² , and the optically anisotropic layer of the polarizing plate faced the cell substrate, and the rubbing direction of the liquid crystal cell and the optical difference facing the liquid crystal cell. They were arranged so that the rubbing direction of the isotropic layer was antiparallel.

(IPS panel)
The polarizing plate of the present invention is such that the viewing side polarizing plate is 32 "wide and the absorption axis of the polarizer is long, and the backlight side polarizing plate is rectangular so that the absorption axis of the polarizer is short. The polarizing plate made of the cellulose ester of the present invention was peeled off from the front and back sides of the IPS mode liquid crystal TV (manufactured by Hitachi, Ltd., W32-L5000). A liquid crystal display device was prepared by bonding in combination, and after bonding the polarizing plate, it was held and bonded for 20 minutes at 50 ° C. and 5 kg / cm ^2, with the absorption axis of the polarizing plate on the viewing side being the horizontal direction of the panel In addition, the absorption axis of the polarizing plate on the backlight side was arranged in the panel vertical direction, and the adhesive layer surface was arranged on the liquid crystal cell side.

[Example 9]
In the preparation of the cellulose ester pellets in Example 1 of the cellulose ester film sample 1-8 of the present invention (1) without adding two kinds of stabilizers in advance, (3) two kinds of the present invention in the melt film forming step The stabilizer was added to the hopper together with the cellulose ester, and the cellulose ester film sample 9-1 of the present invention was produced in exactly the same manner as the cellulose ester film sample 1-8 of the present invention. The increase in coloring increased slightly (0.03), but all the characteristics were within the allowable range. Accordingly, in the present invention, at least one kind of stability selected from the group consisting of at least one phenolic stabilizer having a molecular weight of 500 or more, a phosphite stabilizer having a molecular weight of 500 or more, and a thioether stabilizer having a molecular weight of 500 or more. It was confirmed that it is preferable to add the agent in the pelletizing step.

[Example 10]
In preparation of cellulose ester pellets (1) in the cellulose ester film sample 1-8 of the present invention of Example 1, phosphorus produced from bisphenol A (1 mol), phenol (4 mol) and phosphorus oxychloride as a plasticizer A cellulose ester film sample 10-1 of the present invention was produced in the same manner as the cellulose ester film sample 1-8 except that 5% by mass of an acid ester (molecular weight of 500 or more) was added to the cellulose ester.
The resulting cellulose ester film did not show any smoke during film formation, and was excellent in all respects such as die lines, transmittance, increased coloring, and optical properties (Re unevenness, Rth unevenness). In particular, it was confirmed that the cellulose ester film sample 10-1 was excellent while the moisture content was 1.7% and the non-addition was 2.2%. Therefore, it was confirmed that the plasticizer is effective for improving the physical properties of the cellulose ester film.

[Example 11]
(11-1) Preparation of Cellulose Ester Film In the cellulose ester film sample 1-8 of Example 1, except that the cellulose ester A is changed to the cellulose ester described in Table 2, it is completely the same as the cellulose ester film sample 1-8. Similarly, cellulose ester film samples 11-1 to 11-12 of the present invention were produced. The obtained cellulose ester film samples 11-1 to 11-12 of the present invention were satisfactory in all of Re unevenness, Rth unevenness, die stripe, haze and transmittance.

(11-2) Preparation of Polarizing Plate (11-2-1) Saponification of Cellulose Ester Film Each obtained cellulose ester film was saponified by the following immersion saponification method. That is, 2.5 mol / L NaOH aqueous solution was used as the saponification solution. The temperature was adjusted to 60 ° C., and the cellulose ester film was immersed for 2 minutes. Then, it was immersed in 0.05 mol / L sulfuric acid aqueous solution for 30 seconds, and washed with water.
(11-2-2) Production of Polarizing Film According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, a circumferential speed difference was given between two pairs of nip rolls and stretched in the longitudinal direction to produce a polarizing film having a thickness of 20 μm. .

(11-3) Bonding The polarizing film thus obtained, the saponified cellulose ester film, and the saponified triacetate film (Fuji Photo Film Co., Ltd. Fujitac) were combined with PVA (Kuraray Co., Ltd. PVA). -117H) 3% aqueous solution was used as an adhesive, and bonded in the following combination in the stretching direction of the polarizing film and the film forming direction (longitudinal method) of the cellulose ester.
Polarizing plate A: cellulose ester film / polarizing film / Fujitack (Fujitac TD80UF)
Polarizing plate B: cellulose ester film / polarizing film / cellulose ester film

(11-4) Mounting evaluation (2) Of two pairs of polarizing plates installed with a liquid crystal layer sandwiched between 26-inch and 40-inch liquid crystal display devices (manufactured by Sharp Corporation) using VA liquid crystal cells The polarizing plate on one side on the observer side was peeled off, and the polarizing plate A or B was attached instead using an adhesive. A liquid crystal display device was prepared by arranging so that the transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were orthogonal to each other. The obtained liquid crystal display device was observed for light leakage and color unevenness generated in the black display state, and in-plane uniformity. The cellulose ester film of the present invention was very excellent with no color tone change.

(11-5) Preparation of Low Reflective Film Using the cellulose ester film of the present invention, the film is low in accordance with Example 47 of the Japan Institute of Invention and Technology (public technical number 2001-1745, published on March 15, 2001, Japan Institute of Invention). When a reflective film was prepared, it had good optical performance.

(11-6) Preparation of optical compensation film When the liquid crystal layer was applied to the cellulose ester film of the present invention according to Example 1 of JP-A-11-316378, a good optical compensation film was obtained.

[Example 12]
Sample 1-8 and Sample 1-12 of Example 1 except that cellulose ester A is changed to the following cellulose esters A121 and A122 in the production steps of Sample 1-8 and Sample 1-12 of Example 1, respectively. Samples 12-1 and 12-2 were prepared in the same manner as described above. The obtained cellulose ester film samples 12-1 and 12-2 of the present invention were satisfactory in all of Re unevenness, Rth unevenness, die stripe, haze, and transmittance.

(Synthesis of cellulose esters A121 and A122)
After spraying 0.1 part by mass of acetic acid and 2.7 parts by mass of propionic acid to 10 parts by mass of cellulose (hardwood pulp), it was stored at room temperature for 1 hour. Separately, a mixture of acetic anhydride 1.2 parts by mass, propionic anhydride 61 parts by mass and sulfuric acid 0.7 parts by mass was prepared, and after cooling to −10 ° C., the cellulose and the reaction vessel were subjected to the above pretreatment. Mixed. After 30 minutes, the external temperature was raised to 30 ° C. and reacted for 4 hours. 46 parts by mass of 25% aqueous acetic acid was added to the reaction vessel, the internal temperature was raised to 60 ° C., and the mixture was stirred for 2 hours. 6.2 parts by mass of a solution prepared by mixing equal parts of magnesium acetate tetrahydrate, acetic acid and water was added and stirred for 30 minutes. The reaction solution was subjected to pressure filtration with a metal sintered filter having a reserved particle diameter of 40 μm, 10 μm, and 5 μm in order to remove foreign matters. The reaction solution after filtration was mixed with 75% aqueous acetic acid to precipitate cellulose acetate propionate, and then washed with warm water at 70 ° C. until the pH of the washing solution reached 6-7. Furthermore, after performing the process stirred for 0.5 hour in 0.001% calcium hydroxide aqueous solution, it filtered. The obtained cellulose acetate propionate was dried at 70 ° C. to obtain cellulose ester A121.

^From the measurement of ¹ H-NMR, the obtained cellulose ester A121 has an acetyl substitution degree of 0.15, a propionyl substitution degree of 2.62, a total substitution degree of 2.77, and a number average molecular weight of 54500 (number average polymerization degree DPn = 173). , Mass average molecular weight 132000 (mass average polymerization degree DPw = 419), residual sulfuric acid content 45 ppm, magnesium content 8 ppm, calcium content 46 ppm, sodium content 1 ppm, potassium content 1 ppm, iron content 2 ppm. As a result of observing the film cast from the dichloromethane solution of this sample with a polarizing microscope, almost no foreign matter was observed when the polarizers were made orthogonal or parallel.

  Furthermore, by changing the charged amounts of acetic anhydride and propionic anhydride, cellulose having an acetyl substitution degree of 0.43, a propionyl substitution degree of 2.40, a total substitution degree of 2.83, a weight average molecular weight of 125,000, and a number average molecular weight of 48,000. Acetate propionate (cellulose ester A122) was obtained. The residual sulfuric acid content was 40 ppm, the magnesium content was 10 ppm, the calcium content was 50 ppm, the sodium content was 2 ppm, the potassium content was 1 ppm, and the iron content was 1 ppm. As a result of observing the film cast from the dichloromethane solution of this sample with a polarizing microscope, almost no foreign matter was observed when the polarizers were made orthogonal or parallel.

  According to the production method of the present invention, it is possible to provide a cellulose ester film in which Re unevenness, Rth unevenness, die line, haze, transmittance and colorability are greatly reduced. Furthermore, if the cellulose ester film of the present invention is incorporated in a liquid crystal display device, it is possible to greatly suppress changes in visibility due to display unevenness and humidity, which have been problematic in the past. The present invention also provides an environmentally friendly cellulose ester film by providing a production method that does not use an organic solvent in response to the increasing demand for cellulose triacetate as an optical application. From the above, the cellulose ester film of the present invention has very high industrial applicability.

It is sectional drawing which shows the structure of an extruder.

Explanation of symbols

22 Extruder 32 Cylinder 40 Supply port A Supply part B Compression part C Weighing part

Claims (21)

Cellulose ester satisfying the following formulas (S-1) to (S-3) and at least one phenol-based stabilizer having a molecular weight of 500 or more are 0.02 to 3% by mass with respect to the cellulose ester, and the molecular weight is Cellulose ester mixture containing at least one selected from the group consisting of phosphite ester stabilizers having a molecular weight of 500 or more and thioether stabilizers having a molecular weight of 500 or more with respect to the cellulose ester A method for producing a cellulose ester film, comprising a melt film-forming step in which a cellulose ester film having a film thickness of 20 μm to 300 μm is formed by melting at a temperature of 180 to 240 ° C. and extruding from a die.
Formula (S-1) 2.5 <= A + B <= 3.0
Formula (S-2) 0 ≦ A ≦ 2.2
Formula (S-3) 0.8 ≦ B ≦ 3.0
(In the formula, A represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and B represents the total degree of substitution of the acyl group having 3 to 22 carbon atoms with respect to the hydroxyl group of cellulose.)   The method for producing a cellulose ester film according to claim 1, wherein the cellulose ester mixture is melted at 180 to 240 ° C to produce pellets, and the pellets are melted at 180 to 240 ° C and extruded from a die.   A compound having a mass loss of 20% by mass or less when heated at 220 ° C. in nitrogen for 30 minutes is used as the phenol stabilizer, and the phosphite stabilizer or the thioether stabilizer The method for producing a cellulose ester film according to claim 1 or 2, wherein a compound having a mass loss of 20% by mass or less when heated at 220 ° C for 30 minutes in nitrogen is used.   The molecular weight of the phenol-based stabilizer is 550 or more, and the molecular weight of the phosphite-based stabilizer or the thioether-based stabilizer is 550 or more. The manufacturing method of the cellulose-ester film of description.   The acyl group of B substituted with respect to the hydroxyl group of the cellulose in the cellulose ester is one or more acyl groups selected from a propionyl group and a butyryl group. The manufacturing method of the cellulose-ester film of one term.   The method for producing a cellulose ester film according to claim 1, wherein the cellulose ester mixture contains fine particles having an average primary particle size of 20 nm to 2 μm.   The cellulose ester film formed by the melt film forming step further includes a stretching step of stretching 0.3 to 3 times in at least one direction. Of manufacturing cellulose ester film.   The method for producing a cellulose ester film according to any one of claims 1 to 7, wherein an oxygen concentration at the time of the pelletization and / or melt film formation is 5% by volume or less.   The cellulose-ester film manufactured by the manufacturing method as described in any one of Claims 1-8. Cellulose ester satisfying the following formulas (S-1) to (S-3) and at least one phenol-based stabilizer having a molecular weight of 500 or more are 0.02 to 3% by mass with respect to the cellulose ester, and the molecular weight is Containing at least one selected from the group consisting of a phosphite ester stabilizer having a molecular weight of 500 or more and a thioether stabilizer having a molecular weight of 500 or more with respect to the cellulose ester, and having a film thickness 20 μm to 300 μm, the residual solvent amount is 0.01% by mass or less, and both the front retardation (Re) unevenness and the thickness direction retardation (Rth) unevenness are less than 3.0 nm. Cellulose ester film.
Formula (S-1) 2.5 <= A + B <= 3.0
Formula (S-2) 0 ≦ A ≦ 2.2
Formula (S-3) 0.8 ≦ B ≦ 3.0
(In the formula, A represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and B represents the total degree of substitution of the acyl group having 3 to 22 carbon atoms with respect to the hydroxyl group of cellulose.)   For the absorbance at 400 nm measured by preparing a 2% by mass methylene chloride solution of the cellulose ester film, the cellulose ester film was heated in air at 240 ° C. for 1 hour, and then a 2% by mass methylene chloride solution was prepared. The cellulose ester film according to claim 10, wherein an increase in absorbance at 400 nm measured by the method is 0.05 or less.   The cellulose ester film according to claim 10 or 11, wherein the front retardation (Re) is 0 to 300 nm and the absolute value of retardation (Rth) in the thickness direction is 0 to 700 nm.   The cellulose ester film according to any one of claims 10 to 12, wherein the visible light transmittance is 90% or more and the haze is 0.01 to 1.2%. The cellulose ester film according to any one of claims 10 to 13, which satisfies the following formulas (A-1) and (A-2).
Formula (A-1) 0 ≦ | Re (700) −Re (400) | ≦ 15 nm
Formula (A-2) 0 ≦ | Rth (700) −Rth (400) | ≦ 35 nm
(In the formula, Re (400) and Re (700) represent the front retardation (Re) at wavelengths of 400 nm and 700 nm of the cellulose ester film, and Rth (400) and Rth (700) represent the cellulose ester film. Represents retardation in the thickness direction (Rth) at wavelengths of 400 nm and 700 nm.)   The cellulose ester film according to any one of claims 10 to 14, wherein a contact angle of water on the film surface (25 ° C, relative humidity 60%) is 45 ° or less.   The cellulose ester film according to claim 10, comprising fine particles having an average primary particle size of 20 nm to 2 μm.   The plasticizer having a molecular weight of 500 or more is contained in an amount of 1 to 20% by mass with respect to the cellulose ester, The cellulose ester film according to any one of claims 10 to 16.   A polarizing plate comprising at least one layer of the cellulose ester film according to any one of claims 10 to 17 laminated on a polarizing film.   An optical compensation film comprising the cellulose ester film according to claim 10 as a base material.   An antireflection film comprising the cellulose ester film according to any one of claims 10 to 17 as a substrate.   A liquid crystal display device using at least one of the polarizing plate according to claim 18, the optical compensation film according to claim 19, and the antireflection film according to claim 20.

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