JP2006045500A - Manufacturing method of cellulose acylate, and optical film obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a cellulose acylate containing few minute foreign matters and suitable as a material for an optical film, and to provide a cellulose acylate film capable of forming a liquid crystal display device of high qualities by solution film-forming or melt film-forming the cellulose acylate. <P>SOLUTION: The manufacturing method of the cellulose acylate having substitution degrees A and B satisfying the formulae; 2.0≤A+B≤3, 0≤A≤2.5 and 0.3≤B≤3 (wherein A is a substitution degree of acetyl groups; and B is the total of the substitution degrees of 3-7C acyl groups) comprises (1) a step for adding to a cellulose at least one of water and a 2-7C carboxylic acid as an activating agent and (2) a step for maintaining the mixture at 40°C or a higher temperature for at least 1 hr. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing cellulose acylate suitable for an optical film having a small content of fine foreign matter, and relates to an efficient synthesis method for shortening the reaction time. Furthermore, this invention relates to the optical film which consists of a cellulose acylate with little content of a micro foreign material.

  Cellulose acetate has been used as a support for photographic light-sensitive materials because of its transparency, toughness, and optical isotropy, and in recent years, its use has been expanded as an optical film for liquid crystal display devices. As an optical film for a liquid crystal display device, a polarizing plate protective film, an in-plane retardation (Re) and a thickness direction retardation (Rth) are developed, and an STN (super twisted nematic) system is used. A method of using it as a retardation film of a liquid crystal display element has been implemented.

In recent years, VA (vertical alignment) type and OCB (optically compensated bend) type display elements that require higher Re and Rth phase differences than STN type have been developed, and optical films with excellent retardation development. Material is required. A solution casting film using a mixed ester of cellulose acetyl group and propionyl group (cellulose acetate propionate) has been disclosed as a novel optical film material for meeting such demands (Patent Document 1). ). In addition, since cellulose acetate butyrate and cellulose acetate propionate have a melting temperature lower than that of cellulose acetate, a method is disclosed in which these cellulose acylates are melted to form an optical film (Patent Document 2). ).
As a commercial product of cellulose acylate other than cellulose acetate, various cellulose acetate butyrate and cellulose acetate propionate are disclosed for molding or coating (Non-patent Document 1).

  However, cellulose acetate butyrate, cellulose acetate propionate, etc. described in these patents and literature have the disadvantage that they contain fine foreign substances more easily than cellulose acetate, and the acylation reactivity. The reaction time is longer than that of cellulose acetate due to its low viscosity, and when the reaction temperature is increased or the amount of the catalyst is increased in order to solve this problem, the degree of polymerization, which is undesirable for film applications, tends to decrease. have. Although the details of the actual state of the minute foreign matter are unknown, it is estimated that the cellulose is unreacted or has a low acylation degree. Therefore, when a polarizing plate is made using a film made from such a cellulose acylate and incorporated in a liquid crystal display device, the refractive index of the minute foreign matter that is an insoluble matter is different from that of the cellulose ester, so the polarization state is abnormal. This may cause a defect such as light leakage depending on the use situation, which may deteriorate the quality of the liquid crystal display device. Coupled with the recent increase in definition of liquid crystal display devices, a decrease in the content of minute foreign matter is recognized as one of the important characteristics required for optical film materials.

  As a means for reducing minute foreign matters contained in cellulose acetate butyrate or cellulose acetate propionate, a method of filtering a dissolved dope with a filter is disclosed (Patent Document 3). This method is effective in reducing fine foreign matter if the filtration conditions are properly selected, but if the amount of fine foreign matter contained is large, the filtration pressure increases or the productivity decreases due to consumption of the filter medium. Therefore, it is essential to fundamentally reduce the amount of fine foreign matter contained in the cellulose acylate itself.

  As a method for synthesizing cellulose acetate propionate, for example, a method in which carboxylic acid is added to cellulose and held at 54.4 ° C. for 30 minutes and then acylated using sulfuric acid as a catalyst is disclosed (Patent Document 4). In addition, a method for producing cellulose acylate using trifluoroacetic anhydride as a propellant for acylation is disclosed (Patent Document 5). These methods are useful for the purpose of obtaining a cellulose acylate for molding or paint grade, but the content of the fine foreign matters is often so large that it is not suitable for optical film applications. In addition, the latter method has a problem that the cost is high for industrial production.

  As a means for activating cellulose and improving its reactivity, for example, after making wood pulp into a slurry in a dilute acetic acid aqueous solution, after repeating filtration and acetic acid substitution, acetylation is performed to obtain acetylcellulose. Although the method to obtain is disclosed, it is necessary to collect | recover a lot of acetic acid, and it is lacking in industrial production aptitude (patent document 6). As another method, cellulase is allowed to act on cellulose (Patent Document 7). A method of adding cellulose in acetic acid and acetic anhydride to cellulose and then subjecting it to high pressure conditions to obtain cellulose diacetate (Patent Document) 8), etc. are disclosed. However, there is a problem that both are not suitable for industrial mass production. Furthermore, in any method, when applied to cellulose acetate butyrate, cellulose acetate propionate, etc., it is effective for improving the acylation reactivity, but the content of fine foreign matter is suitable for optical films. However, there is a problem that the effect is insufficient for the purpose of reducing the amount to a certain amount.

  Thus, an industrially useful production method for reducing the amount of fine foreign matter contained in cellulose acetate butyrate, cellulose acetate propionate, etc. to a level usable as an optical film has not been known to date. This was the actual situation, and its realization was strongly desired.

JP 2001-188128 A JP 2000-352620 A JP 2001-188128 A Japanese National Patent Publication No. 6-501040 JP-A-6-32801 US Pat. No. 3,767,642 German Patent No. 19,624,866 US Pat. No. 5,371,207 Eastman Chemical Company Catalog (1994)

  An object of the present invention is to provide a method for producing a cellulose acylate having a small amount of fine foreign matter, which is suitable as a material for an optical film, and further, by forming a solution film or a melt film from the cellulose acylate. An object of the present invention is to provide a cellulose acylate film capable of producing a simple liquid crystal display device.

The above object of the present invention has been achieved as a result of intensive studies.
(1) A method for producing cellulose acylate satisfying the substitution degree of the following formula,
1) a step of adding at least one of water or a carboxylic acid having 2 to 7 carbon atoms as an activator to cellulose;
2) A method for producing cellulose acylate, comprising a step of maintaining at 40 ° C. or more for 1 hour or more.
2.0 ≦ A + B ≦ 3
0 ≦ A ≦ 2.5
0.3 ≦ B ≦ 3
(A represents the substitution degree of the acetyl group, and B represents the total substitution degree of the acyl group having 3 to 7 carbon atoms.)
(2) A method for producing cellulose acylate satisfying the substitution degree of the following formula,
1) a step of adding at least one of water or a carboxylic acid having 2 to 7 carbon atoms as an activator to cellulose;
2) A process of maintaining at 40 ° C or higher for 1 hour or more
3) a step of cooling the cellulose to −30 ° C. or higher and lower than 30 ° C. before acylation;
4) A step of adding an acid anhydride of a carboxylic acid having 2 to 7 carbon atoms to the cellulose thus treated, and acylating the hydroxyl group of the cellulose in the presence of Bronsted acid;
A method for producing cellulose acylate, comprising:
2.0 ≦ A + B ≦ 3
0 ≦ A ≦ 2.5
0.3 ≦ B ≦ 3
(A represents the substitution degree of the acetyl group, and B represents the total substitution degree of the acyl group having 3 to 7 carbon atoms.)
(3) The method for producing cellulose acylate according to (1) or (2), wherein the activator added to cellulose is a carboxylic acid having 2 to 7 carbon atoms.
(4) The cellulose acylate according to any one of (1) to (3), wherein the activator added to cellulose is selected from acetic acid, propionic acid or butyric acid. Production method.
(5) The method for producing cellulose acylate according to any one of (1) to (4), wherein the activator added to cellulose is acetic acid.
(6) The cellulose acylate according to any one of (1) to (5), wherein the time for keeping the cellulose at 40 ° C. or more together with the activator is 1 hour or more and 100 hours or less. Production method.
(7) The method for producing a cellulose acylate according to any one of (1) to (6), wherein the cellulose is kept at 60 ° C. or higher and 90 ° C. or lower together with the activator.
(8) The method for producing a cellulose acylate according to any one of (2) to (7), wherein the Bronsted acid is sulfuric acid.
(9) The method for producing a cellulose acylate according to any one of (2) to (8), wherein the maximum temperature reached in the acylation step is 50 ° C. or lower.
(10) The method for producing cellulose acylate according to any one of (2) to (9), wherein a reaction terminator is added over 3 minutes to 3 hours after the acylating step.
(11) The method for producing a cellulose acylate according to (10), wherein the reaction terminator is acetic acid containing 5% by mass to 80% by mass of water.
(12) A cellulose acylate film produced by casting a cellulose acylate produced by the production method according to any one of (1) to (11) by solution casting.
(13) A cellulose acylate film produced by melt casting a cellulose acylate produced by the production method according to any one of (1) to (11).
(14) The cellulose acylate film according to (12) or (13), wherein the in-plane retardation (Re) and the thickness direction retardation (Rth) satisfy the following formula:
Rth ≧ Re
300 ≧ Re ≧ 0
500 ≧ Rth ≧ 0
(15) A polarizing plate having at least one of the cellulose acylate films according to any one of (12) to (14) as a protective film for the polarizing film.

According to the production method of the present invention, cellulose acylate suitable for an optical film having a small content of fine foreign matters can be produced in a short reaction time. Furthermore, according to the production method of the present invention, an excellent optical film with a small content of fine foreign matters can be obtained.
In addition, the cellulose acylate film of the present invention produced by solution casting or melt casting from the cellulose acylate enables the production of a high-quality liquid crystal display device.

The cellulose acylate of the present invention will be described in detail. The cellulose acylate of the present invention is characterized by satisfying the substitution degree of the following formula.
2.0 ≦ A + B ≦ 3
0 ≦ A ≦ 2.5
0.3 ≦ B ≦ 3
A represents the substitution degree of the acetyl group, and B represents the total substitution degree of the acyl group having 3 to 7 carbon atoms.

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

  Preferred acyl groups as B are propionyl, butyryl, 2-methylpropionyl, pentanoyl, 3-methylbutyryl, 2-methylbutyryl, 2,2-dimethylpropionyl (pivaloyl), hexanoyl, 2-methylpentanoyl, 3-methylpentanoyl, 4-methylpentanoyl, 2,2-dimethylbutyryl, 2,3-dimethylbutyryl, 3,3-dimethylbutyryl, cyclopentanecarbonyl, heptanoyl, cyclohexanecarbonyl, benzoyl and the like can be mentioned, but more preferred Is propionyl, butyryl, pentanoyl, hexanoyl or benzoyl, particularly preferably propionyl or butyryl.

In the present invention, A + B satisfies 2.0 or more and 3 or less. A + B is preferably 2.5 or more and 3 or less, more preferably 2.6 or more and 2.97 or less, and particularly preferably 2.7 or more and 2.95 or less.
In the present invention, A satisfies 0 or more and 2.5 or less. A is preferably 0.1 or more and 2.1 or less, more preferably 0.2 or more and 2.0 or less, and particularly preferably 0.25 or more and 1.8 or less.
Further, in the present invention, B satisfies 0.3 or more and 3 or less. B is preferably 0.7 or more and 2.9 or less, more preferably 0.85 or more and 2.85 or less, and particularly preferably 1.0 or more and 2.8 or less.

The method for producing the cellulose acylate of the present invention comprises:
1) a step of adding at least one of water or a carboxylic acid having 2 to 7 carbon atoms as an activator to cellulose (hereinafter also referred to as “activation step”);
2) including a step of maintaining at 40 ° C. or more for 1 hour or more.
Preferably, furthermore,
3) a step of cooling the cellulose to −30 ° C. or higher and lower than 30 ° C. before acylation;
4) A step of acylating a hydroxyl group of cellulose in the presence of Bronsted acid with a carboxylic acid anhydride having 2 to 7 carbon atoms to the cellulose treated as described above,
It is characterized by including.

Below, the manufacturing method of the cellulose acylate of this invention is demonstrated in detail.
Inventors fully activated cellulose prior to acylation to enable the acylation to proceed rapidly and homogeneously, and the amount of fine foreign matter is greatly reduced. I found. Although the details of this mechanism are not yet clear, it is considered that the reaction activity of the hydroxyl group of cellulose is improved by breaking strong hydrogen bonds between or within the molecules of the cellulose polymer. As the cellulose raw material, it is preferable to use a high-purity one having an α-cellulose content of 92-99.9%.

  The activation step includes 1) a step of adding at least one of water or a carboxylic acid having 2 to 7 carbon atoms as an activator, and 2) a step of maintaining at 40 ° C. or more for 1 hour or more. . At this time, when the cellulose raw material is in the form of a sheet or a lump, it is preferably crushed in advance. It is also preferable to further loosen the cellulose fibers by crushing or stirring during the step 1) or 2) or in the step before and after. The activated cellulose is preferably crushed until it becomes fluffy. The activator may be added by adjusting to any temperature, and the addition method can be selected from spraying, dropping, dipping and the like.

As the activator, water or carboxylic acid can be used, but when water is used, after activation, “an excess of acid anhydride is added to perform dehydration”, “to replace water It is preferable to include a step of “washing with carboxylic acid” or “adjusting acylation conditions”.
Preferred activators are carboxylic acids having 2 to 7 carbon atoms (for example, acetic acid, propionic acid, butyric acid, 2-methylpropionic acid, valeric acid, 3-methylbutyric acid, 2-methylbutyric acid, 2, 2-dimethylpropionic acid (pivalic acid), hexanoic acid, 2-methylvaleric acid, 3-methylvaleric acid, 4-methylvaleric acid, 2,2-dimethylbutyric acid, 2,3-dimethylbutyric acid, 3,3-dimethyl Butyric acid, cyclopentanecarboxylic acid, heptanoic acid, cyclohexanecarboxylic acid, benzoic acid, etc.), more preferably acetic acid, propionic acid, or butyric acid, and particularly preferably acetic acid.
In the activation, a Bronsted acid such as sulfuric acid can be further added as necessary. However, when a strong acid such as sulfuric acid is added, depolymerization is promoted. Therefore, the addition amount is preferably limited to about 0.1% by mass to 10% by mass with respect to cellulose. Two or more kinds of activators may be used in combination, or an acid anhydride of a carboxylic acid having 2 to 7 carbon atoms may be added.

  The addition amount of the activator is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 30% by mass or more based on cellulose. If the amount of the activator is small, the degree of activation of the cellulose decreases. The upper limit of the addition amount of the activator is not particularly limited as long as productivity is not lowered, but it is preferably 100 times or less, more preferably 20 times or less, and 10 times or less by mass with respect to cellulose. It is particularly preferred that Activation may be carried out by adding a large excess of activator to cellulose, and then the amount of the activator may be reduced by performing operations such as filtration, air drying, heat drying, distillation under reduced pressure, and solvent substitution.

  The process of keeping cellulose at 40 ° C. or more for 1 hour or more together with the activator will be described. If the temperature for keeping the cellulose together with the activator is lower than 40 ° C., the activation effect is insufficient, and the generation of fine foreign substances cannot be sufficiently suppressed. On the other hand, if the temperature is higher than 100 ° C., cellulose may be deteriorated and a large amount of energy is required for heating, which is not preferable for industrial production. The temperature for keeping the cellulose together with the activator is preferably 40 ° C. or higher and 90 ° C. or lower, more preferably 50 ° C. or higher and 90 ° C. or lower, and particularly preferably 60 ° C. or higher and 90 ° C. or lower. The temperature at the time of activation may be constant or may be changed.

When the time for keeping the cellulose together with the activator is shorter than 1 hour, the activation effect is insufficient and the generation of fine foreign matters cannot be sufficiently suppressed. The upper limit is not particularly limited. However, when it is longer than 720 hours, it is not preferable from the viewpoint of industrial production. The time for keeping the cellulose together with the activator is preferably 1 hour or more and 100 hours or less, more preferably 2 hours or more and 72 hours or less, and particularly preferably 3 hours or more and 48 hours or less.
The step of activating cellulose can also be performed under pressure. Moreover, you may use electromagnetic waves, such as a microwave and infrared rays, as a heating means.

  The method for producing the cellulose acylate of the present invention preferably includes a step of cooling the cellulose to −30 ° C. or more and less than 30 ° C. before acylation. If the acylation proceeds while the cellulose is at a high temperature, it becomes difficult to control the temperature during the acylation, and if the acylation temperature is too high, depolymerization proceeds and the degree of polymerization of the cellulose acylate decreases. The cooling temperature is preferably −20 ° C. or higher and lower than 30 ° C., more preferably −10 ° C. or higher and lower than 25 ° C., and particularly preferably −5 ° C. or higher and lower than 25 ° C. The cooling method may be any method, but after adjusting the temperature of the reaction vessel, conducting the activation treatment, introducing it to another reaction vessel for acylation, or after carrying out the activation treatment Take it out and let it cool or cool to the set temperature, add a precooled solvent or acylating agent to the activated cellulose, or reduce the heat of vaporization of the activator, solvent, or acylating agent by reducing the pressure. You can take a method such as cooling using.

In the method for producing cellulose acylate of the present invention, an acid anhydride of carboxylic acid is added to cellulose, and the hydroxyl group of cellulose is acylated in the presence of Bronsted acid.
The acid anhydride of the carboxylic acid preferably has 2 to 7 carbon atoms. For example, acetic anhydride, propionic anhydride, butyric anhydride, 2-methylpropionic anhydride, valeric anhydride, 3-methylbutyric anhydride , 2-methylbutyric anhydride, 2,2-dimethylpropionic anhydride (pivalic anhydride), hexanoic anhydride, 2-methylvaleric anhydride, 3-methylvaleric anhydride, 4-methylyoshi Herbic anhydride, 2,2-dimethylbutyric anhydride, 2,3-dimethylbutyric anhydride, 3,3-dimethylbutyric anhydride, cyclopentanecarboxylic anhydride, heptanoic anhydride, cyclohexanecarboxylic anhydride, benzoic acid An acid anhydride etc. can be mentioned.
More preferred are acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, hexanoic anhydride, heptanoic anhydride and the like, and particularly preferred are acetic anhydride, propionic anhydride, butyric acid. Anhydrous.
For the purpose of preparing a mixed ester, it is preferable to use these acid anhydrides in combination. The acid anhydride is usually added in excess equivalent to the cellulose. It is preferable to add 1.2 to 50 equivalents relative to the hydroxyl group of cellulose, more preferably 1.5 to 30 equivalents, and particularly preferably 2 to 10 equivalents.

  A Bronsted acid is used as the acylation catalyst used in the method for producing the cellulose acylate of the present invention. The definition of Bronsted acid is described in, for example, “Physical and Chemical Dictionary”, 5th edition (2000). Examples of preferred Bronsted acids include sulfuric acid, perchloric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and the like. Sulfuric acid and perchloric acid are more preferred, and sulfuric acid is preferred. Particularly preferred. A preferable amount of the Bronsted acid catalyst added is 0.1 to 30% by mass, more preferably 1 to 15% by mass, and particularly preferably 3 to 12% by mass with respect to the cellulose.

  In carrying out acylation, a solvent may be added for the purpose of adjusting viscosity, reaction rate, stirring ability, acyl substitution ratio, and the like. As the solvent, dichloromethane, chloroform, carboxylic acid, acetone, ethyl methyl ketone, toluene, dimethyl sulfoxide, sulfolane, and the like can be used. Preferred are carboxylic acids, and more preferred are carboxylic acids having 2 to 7 carbon atoms. Acids (eg acetic acid, propionic acid, butyric acid, 2-methylpropionic acid, valeric acid, 3-methylbutyric acid, 2-methylbutyric acid, 2,2-dimethylpropionic acid (pivalic acid), hexanoic acid, 2-methylvaleric acid 3-methylvaleric acid, 4-methylvaleric acid, 2,2-dimethylbutyric acid, 2,3-dimethylbutyric acid, 3,3-dimethylbutyric acid, cyclopentanecarboxylic acid, and the like.

  When acylation is performed, an acid anhydride and a Bronsted acid, and if necessary, a solvent may be mixed and mixed with cellulose, or sequentially mixed with cellulose. It is preferable to prepare a mixture of an acid and a Bronsted acid or a mixture of an acid anhydride, a Bronsted acid and a solvent as an acylating agent and then react with cellulose. In order to suppress an increase in temperature in the reaction vessel due to heat of reaction during acylation, the acylating agent is preferably cooled in advance. The cooling temperature is preferably −50 ° C. to 20 ° C., more preferably −35 ° C. to 10 ° C., and particularly preferably −25 ° C. to 5 ° C. The acylating agent may be added in liquid form or may be frozen and added as a crystal, flake or block solid. The acylating agent may be added to the cellulose all at once or in divided portions. In addition, cellulose may be added to the acylating agent all at once or in divided portions.

Although acylation of cellulose is an exothermic reaction, the method for producing the cellulose acylate of the present invention is characterized in that the maximum temperature reached during acylation is 50 ° C. or lower. When the reaction temperature is higher than this, depolymerization proceeds and cellulose acylate having a high degree of polymerization cannot be obtained. The maximum temperature reached during acylation is preferably 45 ° C. or lower, more preferably 40 ° C. or lower, and particularly preferably 35 ° C. or lower. The reaction temperature may be controlled using a temperature adjusting device or may be controlled by the temperature of the acylating agent. Since the exotherm during the acylation is large in the initial stage of the reaction, it is possible to control such as cooling in the initial stage of the reaction and heating thereafter. The end point of acylation can be determined by measuring light transmittance, solution viscosity, temperature change of the reaction system, solubility of the reaction product in an organic solvent, and the like.
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 or more and 24 hours or less, more preferably 1 hour or more and 15 hours or less, and particularly preferably 1.5 hours or more and 12 hours or less. If it is 0.5 hours or less, the reaction does not proceed sufficiently under normal reaction conditions, and if it exceeds 24 hours, it is not preferred for industrial production.

  In the method for producing cellulose acylate of the present invention, it is preferable to add a reaction terminator after the acylation reaction. The reaction terminator may be added to the acylation reaction vessel or the reactant may be added to the reaction terminator vessel. The reaction terminator is preferably added over 3 minutes to 3 hours. The reaction terminator may be any as long as it decomposes the acid anhydride, and preferred examples include water, alcohol (eg, ethanol, methanol, propanol, isopropyl alcohol, etc.) or a composition containing these. be able to. When water or alcohol is added directly, a large heat generation exceeding the cooling capacity of the reaction vessel occurs, which causes the degree of polymerization of the cellulose acylate to decrease, or the cellulose acylate precipitates in an undesired form Therefore, a mixture of acetic acid and water is particularly preferably used in the method for producing the cellulose acylate of the present invention. The composition ratio of acetic acid and water can be used at an arbitrary ratio, but acetic acid containing 5% by mass to 80% by mass of water is preferable, and acetic acid containing 10% by mass to 60% by mass of water is more preferable. Acetic acid containing 20% to 50% by weight of water is particularly preferred.

  If the addition time of the reaction terminator is shorter than 3 minutes, the exotherm is large, causing a decrease in the degree of polymerization, insufficient hydrolysis of the acid anhydride, or reducing the stability of cellulose acylate Is not preferable. When the addition time of the reaction terminator exceeds 3 hours, industrial productivity is lowered, which is not preferable. The addition time of the reaction terminator is preferably 4 minutes or longer and 2 hours or shorter, more preferably 5 minutes or longer and 1 hour or shorter, and particularly preferably 10 minutes or longer and 30 minutes or shorter. When adding the reaction terminator, the reaction vessel may or may not be cooled, but for the purpose of suppressing depolymerization, it is preferable to cool the reaction vessel to suppress the temperature rise. It is also preferable to cool the reaction terminator.

After completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess carboxylic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Carbonates, acetates, hydroxides or oxides) may be added.
The cellulose acylate thus obtained has a total degree of substitution of 3, but in order to obtain a desired degree of substitution, 20% in the presence of a small amount of catalyst (generally remaining sulfuric acid) and water. It is preferably carried out by maintaining the temperature at ˜90 ° C. for several minutes to several days to partially hydrolyze the ester bond and to change to cellulose acylate having a desired degree of acyl substitution.
When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above or in water or aqueous acetic acid without neutralization. The cellulose acylate solution is added (or water or an acetic acid aqueous solution is added into the cellulose acylate solution) to separate the cellulose acylate, and the desired cellulose acylate can be obtained by washing and stabilizing treatment.
By removing impurities (sulfuric acid, perchloric acid, trifluoroacetic acid, p-toluenesulfonic acid, methanesulfonic acid, etc.) or bound esters (sulfuric acid ester, etc.) in cellulose acylate by such treatment, cellulose acylate In addition to the effect of increasing the thermal stability of the rate, it is effective in reducing the thermal discoloration of cellulose acylate, particularly when performing melt film formation.

Next, the fine foreign matter in the cellulose acylate will be described in detail.
The minute foreign matter in cellulose acylate is difficult to recognize with the naked eye and is observed using a polarizing microscope. When a polarizing plate protective film is prepared from cellulose acylate containing minute foreign substances and incorporated in a liquid crystal display device, it becomes a cause of failure due to light leakage, particularly in the case of black display that blocks all light.
This fine foreign matter is less than 10μm in diameter is 1μm or more, is observed by a polarization microscope under crossed Nicols, acceptable amounts when used as an optical film is preferably 0 / mm ² or more to 10 / mm ² or less More preferably, it is 0 piece / mm ² or more and 8 pieces / mm ² or less, and particularly preferably 0 piece / mm ² or more and 5 pieces / mm ² or less.

The polymerization degree of the cellulose acylate produced in the present invention is 100 to 700, preferably 120 to 600, more preferably 130 to 450, as a viscosity average polymerization degree. The average degree of polymerization can be measured by the intrinsic viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. Further details are described in JP-A-9-95538. The degree of polymerization can be controlled by reaction conditions and aging conditions. The degree of polymerization can also be adjusted by removing low molecular weight components. When the low molecular component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of normal cellulose acylate, which is useful. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent.
The cellulose acylate obtained by the production method of the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 6, particularly preferably 2.0 to 5.0, more preferably. It is 2.3-5.0, More preferably, it is 2.4-4.0.

  Next, the preferable form of film formation using the cellulose acylate manufactured by the manufacturing method of this invention is demonstrated.

  The cellulose acylate produced by the production method of the present invention may be used alone or in combination of two or more. Moreover, polymeric components other than the cellulose ester manufactured by the manufacturing method of this invention can also be mixed suitably. 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 particularly preferably 92% or more.

<Plasticizer>
It is also preferable to lower the crystal melting temperature (Tm) of cellulose acylate by adding a plasticizer to the cellulose acylate of the present invention. The molecular weight of the plasticizer used in the present invention is not particularly limited, and may be a low molecular weight compound or a high molecular compound. Examples of the plasticizer include phosphate esters, alkylphthalyl alkyl glycolates, carboxylic acid esters, and fatty acid esters of polyhydric alcohols. The property of the plasticizer may be solid or liquid, that is, it is not particularly limited in its melting point or boiling point. When performing melt film formation, those having low volatility can be particularly preferably used.

  Specific examples of the phosphate ester include, for example, triphenyl phosphate, tributyl phosphate, tributoxyethyl phosphate, tricresyl phosphate, trioctyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate, cresyl phenyl phosphate, Examples include octyl diphenyl phosphate, biphenyl diphenyl phosphate, and 1,4-phenylene-tetraphenyl phosphate. Moreover, it is also preferable to use the phosphate ester type plasticizer described in claims 3 to 7 of JP-T-6-501040.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

Examples of carboxylic acid esters include phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate and diethyl hexyl phthalate, and citrate esters such as acetyl trimethyl citrate, acetyl triethyl citrate and acetyl tributyl citrate. , Adipates such as dimethyl adipate, dibutyl adipate, diisobutyl adipate, bis (2-ethylhexyl) adipate, diisodecyl adipate, bis (butyl diglycol adipate), aromatics such as tetraoctyl pyromellitate, trioctyl trimellitate Polycarboxylic acid esters, dibutyl adipate, dioctyl adipate, dibutyl sebacate, dioctyl sebacate, diethyl azelate Dibutyl azelate, aliphatic, such as dioctyl azelate polycarboxylic acid esters, glycerol triacetate, can be mentioned diglycerol tetraacetate, acetylated glyceride, monoglyceride, a polyhydric alcohol fatty acid esters such as diglyceride. In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin and the like are preferably used alone or in combination.
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. These plasticizers can be used alone or in combination with a low-part plasticizer.

Polyhydric alcohol plasticizers have good compatibility with cellulose fatty acid esters, and glycerin ester compounds such as glycerin esters and diglycerin esters that exhibit a significant thermoplastic effect, and polyalkylene glycols such as polyethylene glycol and polypropylene glycol. And compounds in which an acyl group is bonded to the hydroxyl group of polyalkylene glycol.
Specific glycerin esters include glycerin diacetate stearate, glycerin diacetate palmitate, glycerin diacetate myristate, glycerin diacetate laurate, glycerin diacetate caprate, glycerin diacetate nonanate, glycerin diacetate octanoate, Glycerin diacetate heptanoate, glycerol diacetate hexanoate, glycerol diacetate pentanoate, glycerol diacetate oleate, glycerol acetate dicaprate, glycerol acetate dinonanoate, glycerol acetate dioctanoate, glycerol acetate diheptanoate , Glycerol acetate dicaproate, glycerol acetate divalerate, glycerol acetate dibu Glycerol dipropionate caprate, glycerol dipropionate laurate, glycerol dipropionate myristate, glycerol dipropionate palmitate, glycerol dipropionate stearate, glycerol dipropionate oleate, glycerol tributyrate, glycerol tri Examples include but are not limited to pentanoate, glycerin monopalmitate, glycerin monostearate, glycerin distearate, glycerin propionate laurate, glycerin oleate propionate, and these are used alone or in combination. be able to.
Among these, glycerol diacetate caprylate, glycerol diacetate pelargonate, glycerol diacetate caprate, glycerol diacetate laurate, glycerol diacetate myristate, glycerol diacetate palmitate, glycerol diacetate stearate, glycerol diacetate oleate preferable.

Specific examples of diglycerin esters include diglycerin tetraacetate, diglycerin tetrapropionate, diglycerin tetrabutyrate, diglycerin tetravalerate, diglycerin tetrahexanoate, diglycerin tetraheptanoate, diglyceride. Glycerin tetracaprylate, diglycerin tetrapelargonate, diglycerin tetracaprate, diglycerin tetralaurate, diglycerin tetramyristate, diglycerin tetrapalmitate, diglycerin triacetate propionate, diglycerin triacetate butyrate, diglycerin Triacetate valerate, diglycerin triacetate hexanoate, diglycerin triacetate heptanoate, diglycerin triacetate caprylate, Glycerin triacetate pelargonate, diglycerol triacetate caprate, diglycerol triacetate laurate, diglycerol triacetate myristate, diglycerol triacetate palmitate, diglycerol triacetate stearate, diglycerol triacetate oleate, diglycerol diacetate dipropionate, diglycerol Diacetate dibutyrate, diglycerol diacetate divalerate, diglycerol diacetate dihexanoate, diglycerol diacetate diheptanoate, diglycerol diacetate dicaprylate, diglycerol diacetate dipelargonate, diglycerol di Acetate dicaprate, diglycerin diacetate dilaurate, diglycerin diacetate dimisti Diglycerin diacetate dipalmitate, diglycerin diacetate distearate, diglycerin diacetate dioleate, diglyceryl acetate tripropionate, diglyceryl acetate tributyrate, diglyceryl acetate trivalerate, diglyceryl acetate tri Hexanoate, diglycerol acetate triheptanoate, diglycerol acetate tricaprylate, diglycerol acetate tripelargonate, diglycerol acetate tricaprate, diglycerol acetate trilaurate, diglycerol acetate trimyristate, diglycerol acetate tri Palmitate, Diglycerol acetate tristearate, Diglycerol acetate trioleate, Diglycerol laurate, Jig Examples include, but are not limited to, mixed acid esters of diglycerin such as glycerin stearate, diglycerin caprylate, diglycerin myristate, and diglycerin oleate, and these can be used alone or in combination.
Among these, diglycerin tetraacetate, diglycerin tetrapropionate, diglycerin tetrabutyrate, diglycerin tetracaprylate, and diglycerin tetralaurate are preferable.

  Specific examples of the polyalkylene glycol include polyethylene glycol and polypropylene glycol having an average molecular weight of 200 to 1000, but are not limited thereto, and these can be used alone or in combination.

  Specific examples of the compound in which an acyl group is bonded to the hydroxyl group of polyalkylene glycol include polyoxyethylene acetate, polyoxyethylene propionate, polyoxyethylene butyrate, polyoxyethylene valerate, polyoxyethylene caproate, Polyoxyethylene heptanoate, polyoxyethylene octanoate, polyoxyethylene nonanate, polyoxyethylene caprate, polyoxyethylene laurate, polyoxyethylene myristate, polyoxyethylene palmitate, polyoxyethylene stearate , Polyoxyethylene oleate, polyoxyethylene linoleate, polyoxypropylene acetate, polyoxypropylene propionate, polyoxypropylene butyrate, polyoxypropylene Valerate, polyoxypropylene caproate, polyoxypropylene heptanoate, polyoxypropylene octanoate, polyoxypropylene nonanoate, polyoxypropylene caprate, polyoxypropylene laurate, polyoxypropylene myristate, polyoxy Although propylene palmitate, polyoxypropylene stearate, polyoxypropylene oleate, polyoxypropylene linoleate, etc. are mentioned, it is not limited to these, These can be used individually or in combination.

The addition amount of the plasticizer is preferably 0 to 20% by mass, more preferably 2 to 18% by mass, and most preferably 4 to 15% by mass.
When the content of the plasticizer is more than 20% by mass, the heat transferability of the cellulose acylate is improved, the plasticizer oozes out on the surface of the melt-formed film, and the glass transition temperature Tg is heat resistant. Decreases.

<Stabilizer>
In the present invention, as long as it does not impair the required performance, as a stabilizer for preventing thermal deterioration and coloring, phosphite compounds, phosphite compounds, phosphates, thiophosphates, weak organic acids An epoxy compound or the like may be added alone or in admixture of two or more. As specific examples of the phosphite stabilizer, compounds described in paragraphs [0023] to [0039] of JP-A No. 2004-182979 can be preferably used. 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 be used.
The addition amount of the stabilizer in the present invention is preferably 0.005 to 0.5% by mass, more preferably 0.01 to 0.4% by mass or more, and particularly preferably 0.05 to cellulose acylate. It is -0.3 mass%. If the amount added is less than 0.005% by mass, the effect of preventing deterioration and suppressing coloration during melt film formation may be insufficient. On the other hand, the case of 0.5% by mass or more is not preferable because it may ooze out on the surface of the melt-formed cellulose acylate film.
It is also preferable to add a deterioration inhibitor and an antioxidant. By adding a phenol compound, a thioether compound, a phosphorus compound or the like as a deterioration inhibitor or an antioxidant, a synergistic effect appears in deterioration and oxidation prevention. Furthermore, as other stabilizers, the materials described in detail on pages 17 to 22 of the Japan Society for Invention and Technology (Public Technical Number 2001-1745, issued on March 15, 2001, Japan Society of Invention) are preferably used. Can do.

<Ultraviolet absorber>
You may make the cellulose acylate of this invention contain 1 type, or 2 or more types of ultraviolet absorbers. From the viewpoint of preventing deterioration of the liquid crystal, the ultraviolet absorber preferably has a large absorbance for light having a wavelength of 380 nm or less and a small absorbance for light having a wavelength of 400 nm or more from the viewpoint of image display properties. Preferable compounds include, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Further preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. A benzotriazole-based compound is particularly preferable because unnecessary coloring with respect to cellulose acylate is small.

  Preferred UV inhibitors include 2,6-di-tert-butyl-p-cresol, 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′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6 -Tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate and the like.

  Furthermore, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole, 2- (2′-hydroxy) -3′-tert-butyl-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2 ′ -Hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3- Tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenol) ) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-tert-butyl-4 -Hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole- As a mixture of 2-yl) phenyl] propionate, and a UV absorber, a polymer UV absorber, a polymer type UV absorber described in JP-A-6-148430, and the like are preferably used.

  In addition, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-tert A phosphorus processing stabilizer such as -butylphenyl) phosphite may be used in combination. The amount of these compounds added is preferably 1 ppm to 3.0%, more preferably 10 ppm to 2% in terms of mass ratio with respect to cellulose acylate.

  In addition to the above, various additives (for example, optical anisotropy control agent, fine particles, infrared absorber, surfactant, odor trapping agent (amine etc.), etc.) can be added. As the infrared absorbing dye, for example, those disclosed in JP-A No. 2001-194522 can be used, and as the ultraviolet absorber, for example, those described in JP-A No. 2001-151901 can be used, and 0.001 to 5% by mass with respect to cellulose acylate, respectively. It is preferable to contain. It is preferable to use fine particles having an average particle diameter of 5 to 3000 nm, and those composed of metal oxides or cross-linked polymers can be used, and 0.001 to 5% by mass is preferably contained with respect to cellulose acylate. . The deterioration inhibitor is preferably contained in an amount of 0.0001 to 2% by mass based on the cellulose acylate. As the optical anisotropy control agent, for example, those described in JP-A-2003-66230 and JP-A-2002-49128 can be used, and it is preferably contained in an amount of 0.1 to 15% by mass with respect to cellulose acylate.

  The cellulose acylate film of the present invention can be produced by solution casting (hereinafter sometimes referred to as “solution casting”) or melt casting, and is preferably produced by solution casting. Below, the concrete method of solution casting and melt casting is demonstrated.

(Solution casting)
[1] Solvent In the method for producing cellulose acylate of the present invention, any of the following halogen-based solvents and non-halogen-based solvents can be used as the solvent used for dissolving cellulose acylate.
B) Halogen-based solvent The halogen-based organic solvent is preferably dichloromethane or chloroform. Particularly preferred is dichloromethane. In addition, there is no particular problem in mixing an organic solvent other than the halogen-based solvent. In that case, it is necessary to use at least 50% by mass of dichloromethane.

  The non-halogen solvent used in combination with the halogen solvent used in the method for producing the cellulose acylate of the present invention is described below. That is, as a preferable non-halogen solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. Esters, ketones, ethers and alcohols may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a solvent. For example, other functional groups such as alcoholic hydroxyl groups can be used. You may have group simultaneously. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

  The alcohol used in combination with the halogen-based organic solvent may be linear, branched or cyclic, and among them, saturated aliphatic hydrocarbon is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butyl alcohol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.

  The non-halogen organic solvent used in combination with the halogen-based organic solvent is not particularly limited, but methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane, dioxane, ketones having 4 to 7 carbon atoms or It is selected from acetoacetic acid esters, alcohols having 1 to 10 carbon atoms or hydrocarbons. Preferred non-halogen organic solvents used in combination are methyl acetate, acetone, methyl formate, ethyl formate, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl acetoacetate, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol. , 2-butanol, and cyclohexanol, cyclohexane, and hexane.

  Examples of combinations of halogenated organic solvents that are preferred main solvents used in the method for producing cellulose acylate of the present invention include, but are not limited to, the following (numbers in parentheses below) Indicates parts by mass).

・ Dichloromethane / methanol / ethanol / butanol (80/10/5/5)
・ Dichloromethane / acetone / methanol / propanol (80/10/5/5)
・ Dichloromethane / methanol / butanol / cyclohexane (80/10/5/5)
・ Dichloromethane / methyl ethyl ketone / methanol / butanol (80/10/5/5)
・ Dichloromethane / acetone / methyl ethyl ketone / ethanol / isopropanol (75/10/5/5/5)
・ Dichloromethane / cyclopentanone / methanol / isopropanol (80/10/5/5)
・ Dichloromethane / methyl acetate / butanol (80/10/10)
・ Dichloromethane / cyclohexanone / methanol / hexane (70/20/5/5)
・ Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5)
・ Dichloromethane / 1,3-dioxolane / methanol / ethanol (70/20/5/5)
・ Dichloromethane / dioxane / acetone / methanol / ethanol (60/20/10/5/5)
・ Dichloromethane / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (65/10/10/5/5/5)
・ Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol (70/10/10/5/5)
・ Dichloromethane / acetone / ethyl acetate / ethanol / butanol / hexane (65/10/10/5/5/5)
・ Dichloromethane / methyl acetoacetate / methanol / ethanol (65/20/10/5)
・ Dichloromethane / cyclopentanone / ethanol / butanol (65/20/10/5)

B) Non-halogen solvent The preferred non-halogen solvent is preferably a solvent selected from esters, ketones and ethers having 3 to 12 carbon atoms. Esters, ketones and ethers may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO—, and —COO—) can also be used as a main solvent, such as an alcoholic hydroxyl group. It may have a functional group of In the case of the main solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

  Furthermore, a preferable solvent used in the method for producing the cellulose acylate of the present invention is a mixed solvent of three or more different types, and the first solvent is methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane. , At least one selected from dioxane or a mixture thereof, the second solvent is selected from ketones having 4 to 7 carbon atoms or acetoacetate, and the third solvent has 1 to 10 carbon atoms. It is selected from alcohols or hydrocarbons, and more preferably an alcohol having 1 to 8 carbon atoms. Note that when the first solvent is a mixed liquid of two or more kinds of solvents, the second solvent may be omitted. The first solvent is particularly preferably methyl acetate, acetone, methyl formate, ethyl formate, or a mixture thereof, and the second solvent is preferably methyl ethyl ketone, cyclopentanone, cyclohexanone, or methyl acetate. There may be.

  The alcohol as the third solvent may be linear, branched or cyclic, and is preferably a saturated aliphatic hydrocarbon. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butyl alcohol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used.

  Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene. These alcohols and hydrocarbons as the third solvent may be used alone or in combination of two or more, and are not particularly limited. As the third solvent, preferred specific compounds include alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and cyclohexanol, cyclohexane, hexane, Are methanol, ethanol, 1-propanol, 2-propanol, 1-butanol.

  The above three types of mixed solvents preferably contain a first solvent in a proportion of 20 to 95% by mass, a second solvent in a proportion of 2 to 60% by mass, and a third solvent in a proportion of 2 to 30% by mass, Furthermore, it is preferable that a 1st solvent is 30-90 mass%, a 2nd solvent is 3-50 mass%, and also 3-25 mass% of 3rd alcohol is contained. In particular, it is preferable that the first solvent is 30 to 90% by mass, the second solvent is 3 to 30% by mass, and the third solvent is alcohol and 3 to 15% by mass. In addition, when the first solvent is a mixed solution and the second solvent is not used, the first solvent is preferably contained in a ratio of 20 to 90% by mass and the third solvent in a ratio of 5 to 30% by mass, Furthermore, it is preferable that a 1st solvent is 30-86 mass%, and also a 3rd solvent is contained 7-25 mass%. The non-halogen organic solvent used in the present invention is described in more detail in pages 12 to 16 of the Japan Society for Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society for Invention). It is described in detail.

Preferred combinations of non-halogen organic solvents used in the method for producing the cellulose acylate of the present invention can be exemplified below, but are not limited thereto (the numbers in parentheses indicate parts by mass).
・ Methyl acetate / acetone / methanol / ethanol / butanol (75/10/5/5/5)
・ Methyl acetate / acetone / methanol / ethanol / propanol (75/10/5/5/5)
・ Methyl acetate / acetone / methanol / butanol / cyclohexane (75/10/5/5/5)
・ Methyl acetate / acetone / ethanol / butanol (81/8/7/4)
・ Methyl acetate / acetone / ethanol / butanol (82/10/4/4)
・ Methyl acetate / acetone / ethanol / butanol (80/10/4/6)
・ Methyl acetate / methyl ethyl ketone / methanol / butanol (80/10/5/5)
・ Methyl acetate / acetone / methyl ethyl ketone / ethanol / isopropanol (75/10/5/5/5)

・ Methyl acetate / cyclopentanone / methanol / isopropanol (80/10/5/5)
・ Methyl acetate / acetone / butanol (85/10/5)
・ Methyl acetate / cyclopentanone / acetone / methanol / butanol (60/15/15/5/5)
・ Methyl acetate / cyclohexanone / methanol / hexane (70/20/5/5)
・ Methyl acetate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5)
・ Methyl acetate / 1,3-dioxolane / methanol / ethanol (70/20/5/5)
・ Methyl acetate / dioxane / acetone / methanol / ethanol (60/20/10/5/5)
・ Methyl acetate / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (65/10/10/5/5/5)
・ Methyl formate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5)

Methyl formate / acetone / ethyl acetate / ethanol / butanol / hexane (65/10/10/5/5/5),
Acetone / methyl acetoacetate / methanol / ethanol (65/20/10/5)
Acetone / cyclopentanone / ethanol / butanol (65/20/10/5)
Acetone / 1,3-dioxolane / ethanol / butanol (65/20/10/5)
1,3-dioxolane / cyclohexanone / methyl ethyl ketone / methanol / butanol (60/20/10/5/5)

Further, as described below, it is also preferable to add a part of the solvent after dissolution and dissolve in multiple stages (the numbers in parentheses indicate parts by mass).
・ A cellulose acylate solution was prepared with methyl acetate / acetone / ethanol / butanol (81/8/7/4), filtered and concentrated, and 2 parts by weight of butanol was added after addition. ・ Methyl acetate / acetone / ethanol / butanol (84 / 10/4/2) to prepare a cellulose acylate solution, and after filtration / concentration, add 4 parts by weight of butanol additionally. Prepare a cellulose acylate solution with methyl acetate / acetone / ethanol (84/10/6) and filter / Add 5 parts by weight of butanol after concentration

[2] Dissolution In the present invention, in both cases of halogen-based and non-halogen-based solvents, it is preferable that 10 to 35% by mass of cellulose acylate is dissolved in the solvent, more preferably 13 to 33% by mass, In particular, it is 15 to 30% by mass.
Prior to dissolution, it is preferable to dry the cellulose acylate after film formation and after film formation so that the moisture content is 2% by mass or less, more preferably 1% by mass or less.

After mixing these cellulose acylate and solvent, it is preferable to swell the cellulose acylate at 0 to 50 ° C. for 0.1 to 100 hours.
Various additives may be added before the swelling step, during or after the swelling step, and further during or after cooling and dissolution. Examples of the additive include a plasticizer, an ultraviolet ray inhibitor, a deterioration inhibitor, an optical anisotropy control agent, fine particles, an infrared absorber, and a surfactant. In addition to the above-mentioned plasticizers, for example, those described in JP-A No. 2000-352620 can be used, and 0.1 to 25% by mass, more preferably 0.5 to 15% by mass, and more preferably based on cellulose acylate. It is preferable to contain 1-10 mass%. As the infrared absorbing dye, for example, those disclosed in JP-A No. 2001-194522 can be used, and as the ultraviolet absorber, for example, those described in JP-A No. 2001-151901 can be used, and 0.001 to 5% by mass with respect to cellulose acylate, respectively. It is preferable to contain. It is preferable to use fine particles having an average particle diameter of 5 to 3000 nm, and those composed of metal oxides or cross-linked polymers can be used, and 0.001 to 5% by mass is preferably contained with respect to cellulose acylate. . The deterioration inhibitor is preferably contained in an amount of 0.0001 to 2% by mass based on the cellulose acylate. As the optical anisotropy control agent, for example, those described in JP-A-2003-66230 and JP-A-2002-49128 can be used, and it is preferably contained in an amount of 0.1 to 15% by mass with respect to cellulose acylate.

In the present invention, the cellulose acylate may be dissolved at room temperature or may be dissolved by a cooling / heating method. As the cooling / heating method, methods described in JP-A Nos. 11-323017, 10-67860, 10-95854, 10-324774, and 11-302388 can be used. That is, a solvent and cellulose acylate mixed and swollen are dissolved using a screw-type kneader provided with a cooling jacket.
Further, the dope used in the method for producing the cellulose acylate of the present invention is preferably subjected to concentration and filtration, and these are disclosed in the Japan Institute of Technology (Technical Number 2001-1745, published on March 15, 2001, Those described in detail on page 25 of the "Invention Association" can be used.

[3] Film Formation A specific method for solution film formation will be described according to the procedure.
The cellulose acylate produced according to the above is dissolved according to the above-described method to prepare a dope (cellulose acylate high concentration solution). This is filtered and degassed, then kept at 35 ° C., sent to a pressure die through a constant flow pump (for example, a pressure metering gear pump that can deliver a metered liquid with high accuracy by the number of rotations), and a metal or the like from a base (slit) Cast evenly on a smooth support (drum, band, etc.). The casting may be a single layer casting, or two or more types of cellulose acylate solutions may be cast simultaneously and / or sequentially. When the casting process includes two or more layers, the types and concentrations of the cellulose acylate, the solvent, and the additive of the dope in each layer may be the same or different.

  After casting, after drying on a smooth support, it is peeled off and dried while transporting a raw dry dope film (also referred to as web), but peeled off in a raw dry state containing 20% by mass or more of residual solvent. After drying this by the above-described method, both ends are trimmed, embossed (knurling is applied), and then wound up. The residual solvent in the film thus dried is preferably from 0% to 5%, more preferably from 0% to 2%, particularly preferably from 0% to 1%. After drying, trim both ends and wind up. A preferable width is 0.5 m or more and 5 m or less, more preferably 0.7 m or more and 3 m or less, and particularly preferably 1 m or more and 2 m or less. The preferred winding length is 300 m or more and 3,0000 m or less, more preferably 500 m or more and 10,000 m or less, and particularly preferably 1000 m or more and 7000 m or less.

(Melting film formation)
When melt-forming the cellulose acylate of the present invention, the acyl substitution degree of the cellulose acylate preferably satisfies the following formulas (1) to (3). Here, A represents the total of the substitution degree of the acetyl group, and B represents the acyl group having 3 to 7 carbon atoms.
2.0 ≦ A + B ≦ 3.0 Formula (1)
0 ≦ A ≦ 2.0 Formula (2)
1.2 ≦ B ≦ 2.9 Formula (3)

  Among the acyl groups having 3 to 7 carbon atoms that are subject to substitution degree B, propionyl, butyryl, 2-methylpropionyl, pentanoyl, 3-methylbutyryl, 2-methylbutyryl, 2,2-dimethylpropionyl (pivaloyl) are preferred. , Hexanoyl, 2-methylpentanoyl, 3-methylpentanoyl, 4-methylpentanoyl, 2,2-dimethylbutyryl, 2,3-dimethylbutyryl, 3,3-dimethylbutyryl, cyclopentanecarbonyl, heptanoyl , Cyclohexanecarbonyl, benzoyl and the like, more preferably propionyl, butyryl, pentanoyl, hexanoyl and benzoyl, particularly preferably propionyl and butyryl, and most preferably propionyl.

When melt-forming the cellulose acylate of the present invention, A + B is preferably 2.0 to 3.0. More preferably, it is 2.4-3.0, Most preferably, it is 2.5-2.95. When A + B is smaller than 2.0, the hydrophilicity of the cellulose acylate is increased, and the moisture permeability of the film is increased.
A preferably satisfies 0 to 2.0. More preferably, it is 0.05-1.8, Most preferably, it is 0.1-1.6.
B preferably satisfies 1.2 to 2.9. More preferably, it is 1.3-2.9, Most preferably, it is 1.5-2.9.
Furthermore, the cellulose acylate of the present invention can improve the thermal stability by setting the residual sulfate radical amount to a range of preferably 0 to 300 ppm, more preferably 0 to 200 ppm, particularly preferably 0 to 100 ppm. it can. Cellulose acylate with good thermal stability is less colored in melt film formation, and a highly transparent cellulose acylate optical film can be obtained.

When melt-forming the cellulose acylate of the present invention, the preferable degree of polymerization is 100 to 700, more preferably 120 to 600, and particularly preferably 130 to 450. The average degree of polymerization is 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. Furthermore, the method for measuring the average degree of polymerization is described in detail in JP-A-9-95538.
When melt-forming the cellulose acylate of the present invention, the weight average degree of polymerization / number average degree of polymerization of cellulose acylate by GPC is preferably 2.0 to 6.0, and preferably 2.2 to 5. Is more preferable and 2.4 to 4.0 is particularly preferable.

[1] Drying As a raw material for forming the cellulose acylate film of the present invention, it is preferable to use a material obtained by pelletizing cellulose acylate. That is, prior to melt film formation, the moisture content in the pellets is set to 1% or less, more preferably 0.5% or less, and then charged into a hopper of a melt extruder. At this time, the hopper is preferably Tg-50 ° C. or higher and Tg + 30 ° C. or lower, more preferably Tg−40 ° C. or higher and Tg + 10 ° C. or lower, particularly preferably Tg−30 ° C. or higher and Tg or lower. Thereby, the re-adsorption of the water | moisture content in a hopper can be suppressed, and the said drying efficiency can be expressed more easily.

[2] Kneading and extruding Kneading and melting at 120 ° C. or higher and 250 ° C. or lower, more preferably 140 ° C. or higher and 220 ° C. or lower, more preferably 150 ° C. or higher and 200 ° C. or lower. At this time, the melting temperature may be a constant temperature, or may be divided into several parts and controlled. The kneading time is preferably 2 minutes or more and 60 minutes or less, more preferably 3 minutes or more and 40 minutes or less, and particularly preferably 4 minutes or more and 30 minutes or less. Furthermore, it is also preferable to carry out the inside of the melt extruder in an inert (nitrogen or the like) air stream or while evacuating using a vented extruder.

[3] Film formation The melted resin is passed through a gear pump, and after removing the pulsation of the extruder, it is filtered with a metal mesh filter or the like, and extruded from a T-shaped die attached behind it onto a cooling drum in the form of a sheet. Extrusion may be performed in a single layer, or multiple layers may be extruded using a multi-manifold die or a feed block die. At this time, the thickness unevenness in the width direction can be adjusted by adjusting the distance between the lips of the die.

Thereafter, it is extruded onto a casting drum. At this time, it is preferable to use a method such as an electrostatic application method, an air knife method, an air chamber method, a vacuum nozzle method, or a touch roll method to increase the adhesion between the casting drum and the melt-extruded sheet. Such an adhesion improving method may be performed on the entire surface of the melt-extruded sheet or a part thereof.
The casting drum is preferably 60 ° C. or higher and 160 ° C. or lower, more preferably 70 ° C. or higher and 150 ° C. or lower, and particularly preferably 80 ° C. or higher and 150 ° C. or lower. Then, it peels off from a casting drum, winds up after passing through a nip roll. The winding speed is preferably from 10 m / min to 100 m / min, more preferably from 15 m / min to 80 m / min, particularly preferably from 20 m / min to 70 m / min.

The film forming width is preferably 1 m or more and 5 m or less, more preferably 1.2 m or more and 4 m or less, and particularly preferably 1.3 m or more and 3 m or less. The thickness of the unstretched film thus obtained is preferably 30 μm or more and 400 μm or less, more preferably 40 μm or more and 300 μm or less, and particularly preferably 50 μm or more and 200 μm or less.
The sheet thus obtained is preferably trimmed at both ends and wound up. The trimmed part is recycled as a raw material for the same type of film or as a raw material for a film of a different type after being pulverized or after being subjected to a granulation process or a depolymerization / repolymerization process as necessary. May be used. Moreover, it is also preferable from a viewpoint of scratch prevention to attach a lami film to at least one surface before winding.

In the present invention, Re and Rth are represented by the following formulas.
Re (nm) = | nx−ny | × d
Rth (nm) = | {(nx + ny) / 2} −nz | × d
(In each case, nx, ny, and nz are the refractive indexes in the film forming direction, the width direction, and the thickness direction, respectively, and d is the thickness (nm)).

  The Re and Rth of the unstretched cellulose acylate film of the present invention preferably satisfy the following. Re is preferably 0 nm or more and 300 nm or less, more preferably 0 nm or more and 250 nm or less, and particularly preferably 10 nm or more and 200 nm or less. Rth is preferably from 0 nm to 500 nm, more preferably from 20 nm to 400 nm, and particularly preferably from 30 nm to 350 nm.

(Stretching)
Next, stretching of the cellulose acylate film of the present invention formed by solution film formation or melt film formation will be described.

In order to express Re and Rth, it is preferable to stretch the cellulose acylate film. Stretching may be performed on-line during the film-forming process, or may be performed off-line after winding up once after film-forming is completed. That is, in the case of solution casting, stretching may be carried out in an undried state during casting (for example, after peeling from the support after casting and after completion of drying), and after the completion of drying. May be. In the case of melt film formation, stretching may be performed without cooling during film formation, or may be performed after completion of cooling.
The stretching is preferably performed at Tg or more and Tg + 50 ° C. or less, more preferably Tg + 1 ° C. or more and Tg + 30 ° C. or less, particularly preferably Tg + 2 ° C. or more and Tg + 20 ° C. or less. A preferable draw ratio is 10% or more and 300% or less, more preferably 20% or more and 250% or less, and particularly preferably 30% or more and 200% or less. 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 performed by longitudinal stretching, lateral stretching, and combinations thereof. Longitudinal stretching includes (1) roll stretching (stretching in the longitudinal direction using two or more pairs of nip rolls with increased peripheral speed on the outlet side), (2) fixed end stretching (holding both ends of the film, And the like can be used. Further, for the transverse stretching, tenter stretching (stretching by stretching both sides of the film with a chuck and stretching it in the transverse direction (perpendicular to the longitudinal direction)) can be used. These longitudinal stretching and lateral stretching may be performed alone (uniaxial stretching) or in combination (biaxial stretching). In the case of biaxial stretching, it may be carried out in the longitudinal and transverse sequential manners (sequential stretching) or simultaneously (simultaneous stretching).
The stretching speed of longitudinal stretching and lateral stretching is preferably 10% / min or more and 10,000% / min or less, more preferably 20% / min or more and 1000% / min or less, and particularly preferably 30% / min or more and 800% / min or less. is there. In the case of multistage stretching, the average value of the stretching speed of each stage is indicated.

  Following such stretching, it is also preferable to relax 0% to 10% in the longitudinal or lateral direction. Furthermore, it is also preferable to heat-set at 150 ° C. or higher and 250 ° C. or lower for 1 second to 3 minutes following stretching.

  Rth expressed by such stretching is preferably from 0 nm to 500 nm, more preferably from 40 nm to 400 nm, and particularly preferably from 60 nm to 350 nm. Further, Re is preferably 0 nm or more and 300 nm or less, more preferably 20 nm or more and 250 nm or less, and particularly preferably 40 nm or more and 200 nm or less.

Re and Rth are preferably Re ≦ Rth, more preferably Re × 1.5 ≦ Rth, and particularly preferably Re × 2 ≦ Rth. Such Re and Rth are achieved by fixed end uniaxial stretching, more preferably by longitudinal and lateral biaxial stretching. That is, by stretching in the vertical and horizontal directions, the difference in in-plane refractive index (n _md , n _td ) is reduced and Re is reduced, and further, by extending in the vertical and horizontal directions and the area magnification is increased, the thickness is reduced. This is because Rth can be increased by increasing the orientation in the thickness direction. By setting such Re and Rth, light leakage in black display can be further reduced.
The film thickness after stretching in this manner is preferably 10 to 300 μm, more preferably 20 μm to 200 μm, and particularly preferably 30 μm to 100 μm.

  The angle θ formed by the film forming direction (longitudinal direction) and the slow axis of Re of the film is preferably closer to 0 °, + 90 °, or −90 °. That is, in the case of longitudinal stretching, the closer to 0 °, the better, preferably 0 ± 3 °, more preferably 0 ± 2 °, and particularly preferably 0 ± 1 °. In the case of transverse stretching, 90 ± 3 ° or −90 ± 3 ° is preferable, 90 ± 2 ° or −90 ± 2 ° is more preferable, and 90 ± 1 ° or −90 ± 1 ° is particularly preferable.

  The above-mentioned unstretched and stretched cellulose acylate films may be used alone, or may be used in combination with a polarizing plate, a liquid crystal layer or a layer with a controlled refractive index (low reflection layer), A hard coat layer may be provided and used.

(Photoelastic coefficient)
The cellulose acylate film of the present invention is preferably used as a polarizing plate protective film or a retardation plate. When used as a polarizing plate protective film or a retardation plate, the birefringence (Re, Rth) may change due to the stress due to expansion and contraction due to moisture absorption. The change in birefringence due to such stress can be measured as a photoelastic coefficient, and the range is preferably 5 × 10 ⁻⁷ (cm ² / kgf) to 30 × 10 ⁻⁷ (cm ² / kgf), It is more preferably 6 × 10 ⁻⁷ (cm ² / kgf) or more and 25 × 10 ⁻⁷ (cm ² / kgf) or less, and 7 × 10 ⁻⁷ (cm ² / kgf) or more and 20 × 10 ⁻⁷ (cm ² / kgf). It is particularly preferred that

(surface treatment)
The cellulose acylate film after unstretched or stretched can achieve improved adhesion between the cellulose acylate film and each functional layer (for example, the undercoat layer and the back layer) by optionally performing a 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 here may be low-temperature plasma that occurs in a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail in pages 30 to 32 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Invention Association). Note that, in the plasma treatment at atmospheric pressure which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 Kgy is used under 10 to 1000 Kev, and more preferably irradiation energy of 20 to 300 Kgy is used under 30 to 500 Kev. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.

  The alkali saponification treatment may be immersed in a saponification solution or coated with a saponification solution. In the case of the dipping method, it can be achieved by passing an aqueous solution of pH 10 to 14 such as NaOH or KOH through a bath heated to 20 ° C. to 80 ° C. for 0.1 to 10 minutes, and then neutralizing, washing with water and drying. .

  In the case of the coating method, a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method can be used. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, more preferably 12 or more. The reaction conditions during the alkali saponification are preferably 1 second to 5 minutes at room temperature, more preferably 5 seconds to 5 minutes, and particularly preferably 20 seconds to 3 minutes. After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied with water or acid, and then with water. Further, the coating-type saponification treatment and the alignment film uncoating described later can be performed continuously, and the number of steps can be reduced. Specific examples of these saponification methods are described in JP 2002-82226 A and WO 02/46809.

It is also preferable to provide an undercoat layer for adhesion to the functional layer. This layer may be applied after the above surface treatment or may be applied without the surface treatment. Details of the undercoat layer are described on page 32 of the Japan Society for Invention and Innovation (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention).
These surface treatment and undercoating processes can be incorporated at the end of the film forming process, can be performed alone, or can be performed in the functional layer application process described later.

(Functional layer)
The functional layer described in detail on pages 32 to 45 of the cellulose acylate film of the present invention in the technical report of the Invention Association (Public Technical Number 2001-1745, issued March 15, 2001, Invention Association) Are preferably combined. 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 (preparation of polarizing plate)

[Material used]
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. The polarizing film is manufactured by Optiva Inc. A coating type polarizing film typified by can also be used. Iodine and dichroic dye in the polarizing film exhibit deflection performance by being oriented in the binder. As the dichroic dye, an azo dye, stilbene dye, pyrazolone dye, triphenylmethane dye, quinoline dye, oxazine dye, thiazine dye or anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl). For example, the compound as described in Invention Association public technique, public technical number 2001-1745, page 58 (issue date March 15, 2001) can be mentioned.

  As the binder of the polarizing film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used. Examples of the binder include methacrylate copolymer, styrene copolymer, polyolefin, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylolacrylamide) described in paragraph No. [0022] of JP-A-8-338913, Polyester, polyimide, vinyl acetate copolymer, carboxymethyl cellulose, polycarbonate and the like are included. Silane coupling agents can be used as the polymer.

Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are more preferred. . It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%.
It is preferable that the polymerization degree of polyvinyl alcohol is 100-5000.

The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.
The lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of light leakage of the liquid crystal display device. It is preferably not more than a commercially available polarizing plate (about 30 μm), more preferably 25 μm or less, and particularly preferably 20 μm or less.

  The binder of the polarizing film may be cross-linked. A polymer or monomer having a crosslinkable functional group may be mixed in the binder, or a crosslinkable functional group may be imparted to the binder polymer itself. Crosslinking can be performed by light, heat, or pH change, and a binder having a crosslinked structure can be formed. The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, 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 orientation of the polarizing element and the wet heat resistance of the polarizing film are improved.

  Even after the crosslinking reaction is completed, the unreacted crosslinking agent is preferably 1.0% by mass or less, more preferably 0.5% by mass or less. By doing in this way, a weather resistance improves.

[Stretching of polarizing film]
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, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. Stretching may be performed in parallel to the MD direction (parallel stretching) or may be performed in an oblique direction (oblique stretching). These stretching operations may be performed once or divided into several times. By dividing into several times, it is possible to stretch more uniformly even at high magnification.

More preferred is oblique stretching in which the film is stretched with an inclination of 10 to 80 degrees in the oblique direction.
(A) Parallel stretching method Prior to stretching, the PVA film is swollen. The degree of swelling is 1.2 to 2.0 times (mass ratio before swelling and after swelling). Thereafter, the film is stretched at a bath temperature of 15 to 50 ° C., especially 17 to 40 ° C. in an aqueous medium bath or a dye bath for dissolving a dichroic substance while being continuously conveyed through a guide roll or the like. Stretching can be achieved by gripping with two pairs of nip rolls and increasing the conveyance speed of the subsequent nip roll to be higher than that of the previous nip roll. The draw ratio is based on the length ratio after stretching / initial state (hereinafter the same), but the preferred draw ratio is 1.2 to 3.5 times, especially 1.5 to 3.0 times from the viewpoint of the above-mentioned effects. is there. Thereafter, the film is dried at 50 ° C. to 90 ° C. to obtain a polarizing film.

(B) Diagonal Stretching Method For this purpose, a method of stretching using a tenter that projects in an oblique direction in an oblique direction as described in JP-A-2002-86554 can be used. Since this stretching is performed in the air, it is necessary to make it easy to stretch by adding water in advance. The moisture content is preferably 5% or more and 100% or less, more preferably 10% or more and 100% or less.
The temperature during stretching is preferably 40 ° C. or higher and 90 ° C. or lower, and more preferably 50 ° C. or higher and 80 ° C. or lower. The humidity is preferably from 50% relative humidity to 100% relative humidity, more preferably from 70% rh to 100% rh, and particularly preferably from 80% relative humidity to 100% relative humidity. The traveling speed in the longitudinal direction is preferably 1 m / min or more, more preferably 3 m / min or more.

After the stretching is completed, the film is dried at 50 ° C. or higher and 100 ° C. or lower, more preferably 60 ° C. or higher and 90 ° C. or lower, and 0.5 minutes or longer and 10 minutes or shorter. More preferably, it is 1 minute or more and 5 minutes or less.
The absorption axis of the polarizing film thus obtained is preferably 10 to 80 degrees, more preferably 30 to 60 degrees, and particularly preferably substantially 45 degrees (40 to 50 degrees).

[Lamination]
The saponified cellulose acylate film and a polarizing film prepared by stretching are bonded to prepare a polarizing plate. The laminating direction is preferably such that the casting axis direction of the cellulose acylate film and the stretching axis direction of the polarizing plate are 45 degrees.
The bonding adhesive is not particularly limited, and examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. preferable. The thickness of the adhesive layer is preferably 0.01 to 10 μm after drying, and particularly preferably 0.05 to 5 μm.

  The polarizing plate thus obtained preferably has a higher light transmittance, and preferably has a higher degree of polarization. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and particularly preferably in the range of 40 to 50% with respect to light having a wavelength of 550 nm. . The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and particularly preferably in the range of 99 to 100% in light having a wavelength of 550 nm.

  Furthermore, the polarizing plate thus obtained can be laminated with a λ / 4 plate to produce circularly polarized light. In this case, lamination is performed so that the slow axis of λ / 4 and the absorption axis of the polarizing plate are 45 degrees. At this time, λ / 4 is not particularly limited, but more preferably has a wavelength dependency such that the lower the wavelength, the smaller the retardation. Furthermore, it is preferable to use a polarizing film having an absorption axis inclined by 20 ° to 70 ° with respect to the longitudinal direction and a λ / 4 plate made of an optically anisotropic layer made of a liquid crystalline compound.

The thickness of the protective film of the polarizing film is preferably 25 to 350 μm, more preferably 30 to 200, and still more preferably 40 to 120 μm. When the cellulose acylate film of the present invention is used as a protective film for a polarizing film, either an unstretched film or a stretched film can be used. In addition, the stretched cellulose acylate film of the present invention can be used as a protective film function of a polarizing film and is also preferably used as a retardation compensation function.
The obtained polarizing plate preferably has the following configuration. In the following, examples of the unstretched cellulose triacetate film include Fujitac TD80, TD80U, TD80UF (all trade names) manufactured by Fuji Photo Film Co., Ltd.
Polarizing plate A: Unstretched cellulose acylate film / polarizing film / unstretched cellulose triacetate film Polarizing plate B: Unstretched cellulose acylate film / polarizing film / unstretched cellulose acylate film Polarizing plate C: Stretched cellulose acylate film / polarized light Film / Unstretched cellulose triacetate film Polarizing plate D: Stretched cellulose acylate film / polarizing film / Unstretched cellulose acylate film Polarizing plate E: Stretched cellulose acylate film / polarizing film / stretched cellulose acylate film

(2) Application of optical compensation layer (creation of optical compensation sheet)
The optically anisotropic layer is for compensating the liquid crystal compound in the liquid crystal cell in the black display of the liquid crystal display device, and forms an alignment film on the cellulose acylate film, and further provides an optically anisotropic layer. It is formed by doing.

[Alignment film]
An alignment film is provided on the surface-treated cellulose acylate film. This film has a function of defining the alignment direction of liquid crystalline molecules. However, if the alignment state is fixed after the alignment of the liquid crystalline compound, the alignment film plays the role and is not necessarily an essential component. That is, it is possible to produce a polarizing plate using the cellulose acylate film 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 (eg, ω-tricosanoic acid) by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett 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.

The alignment film is preferably formed by polymer rubbing treatment. In principle, the polymer used for the alignment film has a molecular structure having a function of aligning liquid crystal molecules.
In the present invention, in addition to the function of aligning liquid crystal molecules, the crosslinkability of binding side chains having a crosslinkable functional group (eg, double bond) to the main chain or aligning liquid crystal molecules. It is preferable to introduce a functional group into the side chain.

  As the polymer used in the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used. Examples of the polymer include methacrylate copolymers, styrene copolymers, polyolefins, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol) described in paragraph No. [0022] of JP-A-8-338913. Acrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethylcellulose, polycarbonate and the like. Silane coupling agents can be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol) are preferable, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol are more preferable, and polyvinyl alcohol and modified polyvinyl alcohol are particularly preferable. . It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%. It is preferable that the polymerization degree of polyvinyl alcohol is 100-5000.

  A side chain having a function of aligning liquid crystal molecules generally has a hydrophobic group as a functional group. The specific type of functional group is determined according to the type of liquid crystal molecule and the required alignment state.

  For example, the modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of modifying groups include hydrophilic groups (carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, amino groups, ammonium groups, amide groups, thiol groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, fluorine atoms Substituted hydrocarbon groups, thioether groups, polymerizable groups (unsaturated polymerizable groups, epoxy groups, azirinidyl groups, etc.), alkoxysilyl groups (trialkoxy, dialkoxy, monoalkoxy) and the like can be mentioned. As specific examples of these modified polyvinyl alcohol compounds, for example, paragraph numbers [0022] to [0145] in JP-A No. 2000-155216 and paragraph numbers [0018] to [0018] in JP-A No. 2002-62426 are described. [0022] and the like.

  When the side chain having a crosslinkable functional group is bonded to the main chain of the alignment film polymer or the crosslinkable functional group is introduced into the side chain having the function of aligning liquid crystal molecules, the alignment film polymer and optical anisotropy are obtained. The polyfunctional monomer contained in the layer can be copolymerized. As a result, not only between the polyfunctional monomer and the polyfunctional monomer, but also between the alignment film polymer and the alignment film polymer and between the polyfunctional monomer and the alignment film polymer is firmly bonded by a covalent bond. Therefore, the strength of the optical compensation sheet can be remarkably improved by introducing the crosslinkable functional group into the alignment film polymer.

  The crosslinkable functional group of the alignment film polymer preferably contains a polymerizable group in the same manner as the polyfunctional monomer. Specific examples include those described in paragraphs [0080] to [0100] in JP-A-2000-155216. Apart from the crosslinkable functional group, the alignment film polymer can also be crosslinked using a crosslinking agent.

  Examples of the crosslinking agent include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazole, and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraphs [0023] to [024] in JP-A-2002-62426. Aldehydes having high reaction activity, particularly glutaraldehyde are preferred.

  0.1-20 mass% is preferable with respect to a polymer, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. The amount of the unreacted crosslinking agent remaining in the alignment film is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. By adjusting in this way, even if the alignment film is used for a long time in a liquid crystal display device or left in a high temperature and high humidity atmosphere for a long time, sufficient durability without reticulation can be obtained. May occur.

  The alignment film can be basically formed by applying the polymer on the transparent support containing the alignment film forming material and the crosslinking agent, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be carried out at any time after coating on the transparent support. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating solution is preferably a mixed solvent of an organic solvent (eg, methanol) having a defoaming action and water. The ratio of water: methanol is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the layer surface of an orientation film and also an optically anisotropic layer reduces remarkably.

  The alignment film is preferably applied by spin coating, dip coating, curtain coating, extrusion coating, rod coating, or roll coating. A rod coating method is particularly preferable. The film thickness after drying is preferably 0.1 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 more preferable. The drying time can be 1 minute to 36 hours, preferably 1 minute to 30 minutes. The pH is preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, the pH is 4.5 to 5.5, and 5 is particularly preferable.

The alignment film is provided on the transparent support or the undercoat layer. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above.
For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, a method of obtaining alignment by rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber, or the like can be used. Generally, it is carried out by rubbing several times using a cloth or the like in which fibers having a uniform length and thickness are planted on average.

In industrial implementation, this is achieved by bringing the rotating rubbing roll into contact with the film with the polarizing film being transported. Is preferably 30 μm or less. The wrap angle of the film on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 ° or more. As for the conveyance speed of a film, 1-100 m / min is preferable. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °. When used in a liquid crystal display device, the angle is preferably 40 to 50 °. 45 ° is particularly preferred.
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, if necessary, the alignment film polymer is reacted with the polyfunctional monomer contained in the optically anisotropic layer, 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]
As rod-like liquid crystalline molecules, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.

The rod-like liquid crystalline molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline molecules, see Chapter 4, Chapter 7 and Chapter 11 of the Chemical Chemistry of the Quarterly Chemical Review Vol. 22, Liquid Crystal Chemistry (1994), and the 142nd Committee of the Japan Society for the Promotion of Science. Described in Chapter 3.
The birefringence of the rod-like liquid crystal molecule is preferably in the range of 0.001 to 0.7.

  The rod-like liquid crystalline molecule preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably a radically polymerizable unsaturated group or a cationically polymerizable group. Specifically, for example, the polymerizable groups described in paragraphs [0064] to [0086] of JP-A-2002-62427 are described. Group and a polymerizable liquid crystal compound.

[Disc liquid crystalline molecules]
For discotic liquid crystal molecules, C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

  As a discotic liquid crystalline molecule, a compound having liquid crystallinity having a structure 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 Is also included. 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 paragraphs [0151] to “0168” in JP-A No. 2000-155216.

  In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline molecule and the surface of the polarizing film increases or decreases in the depth direction of the optically anisotropic layer and with increasing distance from the surface of the polarizing film. is doing. The angle preferably decreases with increasing distance. Further, the change in angle can be continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, or intermittent change including increase and decrease. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the angle includes a region where the angle does not change, the angle only needs to increase or decrease as a whole. Furthermore, it is preferable that the angle changes continuously.

  The average direction of the major axis of the discotic liquid crystalline molecules on the polarizing film side can be generally adjusted by selecting the discotic liquid crystalline molecules or the material of the alignment film, or by selecting the rubbing treatment method. In addition, the major axis (disk surface) direction of the surface-side (air-side) discotic liquid crystalline molecules is generally adjusted by selecting the type of additive used together with the discotic liquid crystalline molecules or discotic liquid crystalline molecules. be able to. Examples of the additive used together with the discotic liquid crystalline molecule include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the orientation direction of the major axis can also be adjusted by selecting liquid crystalline molecules and additives as described above.

"Other composition of optically anisotropic layer"
Along with the above liquid crystal molecules, a plasticizer, a surfactant, a polymerizable monomer, etc. can be used in combination to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal molecules, and the like. It is preferable that the liquid crystal molecules have compatibility with the liquid crystal molecules and can change the tilt angle of the liquid crystal molecules or do not inhibit the alignment.
Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Preferably, it is a polyfunctional radically polymerizable monomer, and is preferably copolymerizable with the above-mentioned polymerizable group-containing liquid crystal compound. Examples thereof include those described in paragraph numbers [0018] to [0020] in JP-A-2002-296423. The amount of the compound added is generally in the range of 1% by mass to 50% by mass and preferably in the range of 5% by mass to 30% by mass with respect to the discotic liquid crystalline molecules.

Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specific examples include compounds described in paragraph numbers [0028] to [0056] in JP-A-2001-330725.
The polymer used together with the discotic liquid crystalline molecule is preferably capable of changing the tilt angle of the discotic liquid crystalline molecule.

A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include those described in paragraph [0178] of JP-A No. 2000-155216. The addition amount of the polymer is preferably in the range of 0.1% by mass to 10% by mass with respect to the liquid crystalline molecule so as not to inhibit the alignment of the liquid crystal molecules. More preferably, it is in the range.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline molecules is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

[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.
As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

The coating liquid can be applied by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and particularly preferably 1 to 10 μm.

[Fixing the alignment state of liquid crystalline molecules]
The aligned liquid crystalline 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. A photopolymerization reaction is preferred.

  Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.
It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.
The irradiation energy is preferably in the range of 20 mJ / cm ² to 50 J / cm ^2, more preferably in the range of 20 to 5000 mJ / cm ^2, and particularly preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.
A protective layer may be provided on the optically anisotropic layer.

  It is also preferable to combine this optical compensation film and a 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 a polarizing plate using the cellulose acylate film of 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"
Each liquid crystal mode in which such an optical compensation film is used will be described.
(TN mode liquid crystal display)
It is most frequently used as a color TFT liquid crystal display device and is described in many documents. The alignment state in the liquid crystal cell in the TN mode black display is an alignment state in which the rod-like liquid crystalline molecules rise at the center of the cell and the rod-like liquid crystalline molecules lie in the vicinity of the cell substrate.

(OCB mode liquid crystal display)
This is a bend alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned in a substantially opposite direction (symmetrically) between the upper and lower portions of the liquid crystal cell. Liquid crystal display devices using a bend alignment mode liquid crystal cell are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode.

  Similarly to the TN mode, the liquid crystal cell in the OCB mode is in a black display, and the alignment state in the liquid crystal cell is such that the rod-like liquid crystal molecules rise in the center of the cell and the rod-like liquid crystal molecules lie in the vicinity of the cell substrate. .

(VA mode liquid crystal display device)
The feature is that the rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied. In the VA mode liquid crystal cell, (1) the rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied. In addition to a narrowly defined VA mode liquid crystal cell (described in JP-A-2-176625) that is aligned substantially horizontally when a voltage is applied, (2) the VA mode is multi-domained to expand the viewing angle ( Liquid crystal cell (in MVA mode) (SID97, Digest of tech. Papers 28 (1997) 845), (3) rod-like liquid crystal molecules are substantially vertically aligned when no voltage is applied, and twisted A liquid crystal cell of domain alignment mode (n-ASM mode) (described in the proceedings 58-59 (1998) of the Japanese Liquid Crystal Society) and (4) a SURVAVAL mode liquid crystal cell (LCD interface) Presented at the National 98) are included.

(IPS mode liquid crystal display)
The feature is that the rod-like liquid crystalline molecules are aligned substantially horizontally in the plane when no voltage is applied, and this is characterized by switching by changing the orientation direction of the liquid crystal with or without voltage application. Specifically, those described in JP-A Nos. 2004-365941, 2004-12731, 2004-215620, 2002-221726, 2002-55341, and 2003-195333 can be used.

(Other liquid crystal display devices)
The ECB mode and the STN mode can be optically compensated based on the same concept as described above.

(3) Application of antireflection layer (antireflection film)
The antireflection film generally comprises a low refractive index layer which is also an antifouling layer, and at least one layer having a higher refractive index than that of the low refractive index layer (that is, a high refractive index layer and a medium refractive index layer). It is provided above.
Colloidal metal by multilayer deposition of transparent thin films of inorganic compounds (metal oxides, etc.) with different refractive indexes by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, sol-gel method of metal compounds such as metal alkoxides Examples include a method of forming a thin film by post-processing (ultraviolet irradiation: JP-A-9-157855, plasma processing: JP-A-2002-327310) after forming an oxide particle film.

On the other hand, various antireflection films formed by laminating and applying a thin film in which inorganic particles are dispersed in a matrix have been proposed as an antireflection film having high productivity.
The antireflection film which consists of the antireflection layer which provided the anti-glare property which the antireflection film by application | coating as mentioned above provided the surface of the uppermost layer with the shape of a fine unevenness | corrugation is also mentioned.

  The cellulose acylate film of the present invention can be applied to any of the above methods, but a coating method (coating type) is particularly preferable.

[Layer structure of coating type antireflection film]
An antireflection film having a layer structure of at least a medium refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) on the substrate is designed to have a refractive index satisfying the following relationship.
The refractive index of the high refractive index layer> The refractive index of the medium refractive index layer> The refractive index of the transparent support> The refractive index of the low refractive index layer Further, a hard coat layer is provided between the transparent support and the medium refractive index layer. Also good. Further, it may comprise a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer.
Examples thereof include JP-A Nos. 8-122504, 8-110401, 10-300902, JP-A 2002-243906, JP-A 2000-11706, and the like.

Other functions may be imparted to each layer, for example, an antifouling low refractive index layer or an antistatic high refractive index layer (eg, JP-A-10-206603, JP-A-2002). -243906 publication etc.) etc. are mentioned.
The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. The strength of the film is preferably H or more, more preferably 2H or more, and particularly preferably 3H or more in a pencil hardness test according to JIS K5400.

[High refractive index layer and medium refractive index layer]
The layer having a high refractive index of the antireflection film is composed of a curable film containing at least an inorganic compound ultrafine particle having a high refractive index having an average particle diameter of 100 nm or less and a matrix binder.
Examples of the high refractive index inorganic compound fine particles include inorganic compounds having a refractive index of 1.65 or more, preferably those having a refractive index of 1.9 or more. Examples thereof include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.

In order to obtain such ultrafine particles, the surface of the particles is treated with a surface treatment agent (for example, silane coupling agents, etc .: JP-A-11-295503, JP-A-11-153703, JP-A-2000-9908). , Anionic compounds or organometallic coupling agents: Japanese Patent Laid-Open No. 2001-310432, etc., a core-shell structure with high refractive index particles as a core (: Japanese Patent Laid-Open No. 2001-166104, etc.), specific dispersant combined use (E.g., Japanese Patent Laid-Open No. 11-153703, Japanese Patent No. US6110858B1, Japanese Patent Laid-Open No. 2002-27776069, etc.).
Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.

  Further, it is selected from a polyfunctional compound-containing composition containing at least two radically polymerizable and / or cationically polymerizable groups, an organometallic compound containing a hydrolyzable group, and a partial condensate composition thereof. At least one composition is preferred. Examples thereof include compounds described in JP-A Nos. 2000-47004, 2001-315242, 2001-31871, and 2001-296401.

Also preferred are colloidal metal oxides obtained from hydrolyzed condensates of metal alkoxides and curable films obtained from metal alkoxide compositions. For example, it describes in Unexamined-Japanese-Patent No. 2001-293818.
The refractive index of the high refractive index layer is generally 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

[Low refractive index layer]
The low refractive index layer is formed by sequentially laminating on the high refractive index layer. The refractive index of the low refractive index layer is 1.20 to 1.55. Preferably it is 1.30-1.50.
It is preferable to construct as the outermost layer having scratch resistance and antifouling property. As means for greatly improving the scratch resistance, it is effective to impart slipperiness to the surface, and conventionally known thin film layer means such as introduction of silicone or introduction of fluorine can be applied.

  The refractive index of the fluorine-containing compound is preferably 1.35 to 1.50. More preferably, it is 1.36-1.47. The fluorine-containing compound is preferably a compound containing a crosslinkable or polymerizable functional group containing fluorine atoms in the range of 35 to 80% by mass.

For example, paragraph numbers [0018] to [0026] of Japanese Patent Application Laid-Open No. 9-222503, paragraph numbers [0019] to [0030] of Japanese Patent Application Laid-Open No. 11-38202, and paragraph numbers of Japanese Patent Application Laid-Open No. 2001-40284. [0027] to [0028], Japanese Patent Application Laid-Open Nos. 2000-284102 and 2003-26732, paragraph numbers [0012] to [0077], and Japanese Patent Application Laid-Open No. 2004-45462, paragraph numbers [0030] to [0047]. ] Etc. are mentioned.
The silicone compound is a compound having a polysiloxane structure, and preferably contains a curable functional group or a polymerizable functional group in the polymer chain and has a crosslinked structure in the film. For example, reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane (Japanese Patent Laid-Open No. 11-258403, etc.) and the like can be mentioned.

The crosslinking or polymerization reaction of the fluorine-containing and / or siloxane polymer having a crosslinking or polymerizable group is performed simultaneously with or after the application of the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer and the like. It is preferable to carry out by light irradiation or heating.
Also preferred is a sol-gel cured film in which an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent are cured by a condensation reaction in the presence of a catalyst.

  For example, a polyfluoroalkyl group-containing silane compound or a partially hydrolyzed condensate thereof (Japanese Patent Laid-Open Nos. 58-142958, 58-147483, 58-147484, Japanese Patent Laid-Open Nos. 9-157582, 11) -106704), silyl compounds containing a poly "perfluoroalkyl ether" group which is a fluorine-containing long chain group (Japanese Patent Application Laid-Open Nos. 2000-117902, 2001-48590, 2002) 53804), and the like.

The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as a filler (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as an additive other than the above. A low refractive index inorganic compound, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820), silane coupling agents, slip agents, surfactants, and the like.
When the low refractive index layer is located below the outermost layer, the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.). The coating method is preferable because it can be manufactured at a low cost.
The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and particularly preferably 60 to 120 nm.

[Hard coat layer]
The hard coat layer is provided on the surface of the transparent support in order to impart physical strength to the antireflection film. In particular, it is preferably provided between the transparent support and the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound.
The curable functional group is preferably a photopolymerizable functional group, and the hydrous functional group-containing organometallic compound is preferably an organic alkoxysilyl compound.
Specific examples of these compounds are the same as those exemplified for the high refractive index layer.

Specific examples of the constituent composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and WO0 / 46617.
The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described for the high refractive index layer.
A hard-coat layer can also serve as the glare-proof layer (after-mentioned) which contained the particle | grains with an average particle diameter of 0.2-10 micrometers and provided the glare-proof function (anti-glare function).
The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and particularly preferably 3H or higher, in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

[Forward scattering layer]
The forward scattering layer is provided in order to give a viewing angle improvement effect when the viewing angle is inclined in the vertical and horizontal directions when applied to a liquid crystal display device. By dispersing fine particles having different refractive indexes in the hard coat layer, it can also serve as a hard coat function.

  For example, Japanese Patent Application Laid-Open No. 11-38208 specifying a forward scattering coefficient, Japanese Patent Application Laid-Open No. 2000-199809 having a relative refractive index of a transparent resin and fine particles in a specific range, and Japanese Patent Application Laid-Open No. 2002 specifying a haze value of 40% or more. -107512 gazette etc. are mentioned.

[Other layers]
In addition to the above layers, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

[Coating method]
Each layer of the antireflection film is formed by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating, a micro gravure method or an extrusion coating method (US Pat. No. 2,681,294). It can be formed by coating.

[Anti-glare function]
The antireflection film may have an antiglare function that scatters external light. The antiglare function is obtained by forming irregularities on the surface of the antireflection film. When the antireflection film has an antiglare function, the haze of the antireflection film is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.

  As a method for forming irregularities on the surface of the antireflection film, any method can be applied as long as these surface shapes can be sufficiently maintained. For example, a method of forming irregularities on the film surface using fine particles in the low refractive index layer (for example, JP 2000-271878 A), a lower layer of the low refractive index layer (high refractive index layer, medium refractive index layer) Alternatively, a relatively large particle (particle size 0.05 to 2 μm) is added to a hard coat layer in a small amount (0.1 to 50% by mass) to form a surface uneven film, and these shapes are maintained on it. A method of providing a low refractive index layer (for example, JP 2000-281410 A, JP 2000-95893 A, JP 2001-100004 A, 2001-281407, etc.), an uppermost layer (antifouling layer) A method of physically transferring an uneven shape onto the surface after coating (for example, as an embossing method, described in JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401, etc.) And the like.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

Example 1
(Synthesis of cellulose acylate)
Synthesis example 1
(Synthesis of cellulose acetate propionate P-10)
10 g of cellulose (hardwood pulp), 2.2 g of water, and 11 g of acetic acid are placed in a 500 ml separable flask equipped with a reflux apparatus and stirred vigorously for 4 hours while heating in an oil bath adjusted to 80 ° C. 16 g of acetic acid was added and stirred for 2 hours. The cellulose subjected to such pretreatment was swollen and crushed to form a fluff shape. The reaction vessel was placed in an ice water bath at 5 ° C. for 1 hour to sufficiently cool the cellulose. Separately, a mixture of 2 g of acetic anhydride, 62 g of propionic anhydride, and 1.2 g of sulfuric acid was prepared, cooled to −20 ° C., and then added to the pretreated cellulose at once. 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 120 g of 25% aqueous acetic acid was added over 30 minutes. The internal temperature was raised to 30 ° C. and stirred for 2 hours. 5 g of a 50% aqueous solution of magnesium acetate tetrahydrate was added and stirred for 30 minutes. 75 g of 25% aqueous acetic acid and 250 g of water were gradually added to precipitate cellulose acetate propionate. After washing with hot water at 70 ° C. until the pH of the cleaning solution becomes 6-7, stirring is performed in a 0.005% calcium hydroxide aqueous solution at 20 ° C. for 0.5 hour, and the pH of the cleaning solution becomes 7. Washed with water until. The obtained cellulose acetate propionate was dried at 70 ° C. According to ¹ H-NMR and GPC measurement, the obtained cellulose acetate propionate had an acetylation degree of 1.45, a propionylation degree of 1.47 and a polymerization degree of 301.

Synthesis example 2
(Synthesis of cellulose acetate propionate P-4)
10 g of cellulose (hardwood pulp) and 5 g of acetic acid were placed in a 500 ml separable flask equipped with a reflux apparatus and left for 6 hours while heating in an oil bath adjusted to 60 ° C. Thereafter, the mixture was vigorously stirred for 1 hour while heating in an oil bath adjusted to 60 ° C. The cellulose subjected to such pretreatment was swollen and crushed to form a fluff shape. The reaction vessel was placed in an ice water bath at 5 ° C. for 1 hour to sufficiently cool the cellulose. Separately, a mixture of 103 g of propionic anhydride and 1.0 g of sulfuric acid was prepared, cooled to −20 ° C., and then added to the pretreated cellulose at once. After 30 minutes, the external temperature was raised to 20 ° C. and reacted for 3 hours. The reaction vessel was cooled in an ice water bath at 5 ° C., and 120 g of 25% aqueous acetic acid was added over 30 minutes. The internal temperature was raised to 30 ° C. and stirred for 2 hours. 10 g of a 50% aqueous solution of magnesium acetate tetrahydrate was added and stirred for 30 minutes. 75 g of 25% aqueous acetic acid and 250 g of water were gradually added to precipitate cellulose acetate propionate. After washing with hot water at 70 ° C. until the pH of the washing solution becomes 6-7, the mixture is stirred in 0.005% aqueous calcium hydroxide solution for 0.5 hour, and then with water until the pH of the washing solution becomes 7. Washing was performed. The obtained cellulose acetate propionate was dried at 70 ° C. According to ¹ H-NMR and GPC measurement, the obtained cellulose acetate propionate had an acetylation degree of 0.16, a propionylation degree of 2.80, and a polymerization degree of 287.

Synthesis example 3
(Synthesis of cellulose acetate butyrate B-5)
10 g of cellulose (hardwood pulp) and 13.5 g of acetic acid were placed in a 500 ml separable flask equipped with a reflux apparatus and left for 6 hours while heating in an oil bath adjusted to 80 ° C. Thereafter, the mixture was vigorously stirred for 1 hour while heating in an oil bath adjusted to 60 ° C. The cellulose subjected to such pretreatment was swollen and crushed to form a fluff shape. The reaction vessel was placed in an ice water bath at 5 ° C. for 1 hour to sufficiently cool the cellulose. Separately, a mixture of 108 g of butyric anhydride and 1.0 g of sulfuric acid was prepared, cooled to −20 ° C., and then added to the pretreated cellulose at once. 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 120 g of 25% aqueous acetic acid was added over 30 minutes. The internal temperature was raised to 30 ° C. and stirred for 1.5 hours. 10 g of a 50% aqueous solution of magnesium acetate tetrahydrate was added and stirred for 30 minutes. 75 g of 25% aqueous acetic acid and 250 g of water were gradually added to precipitate cellulose acetate butyrate. After washing with hot water at 70 ° C. until the pH of the washing solution becomes 6-7, the mixture is stirred in 0.005% aqueous calcium hydroxide solution for 0.5 hour, and then with water until the pH of the washing solution becomes 7. Washing was performed. The obtained cellulose acetate butyrate was dried at 70 ° C. According to ¹ H-NMR and GPC measurement, the obtained cellulose acetate butyrate had a degree of acetylation of 0.84, a degree of butyrylation of 2.14, and a degree of polymerization of 270.

Synthesis example 4
(Synthesis of cellulose acetate propionate P-1)
150 g of cellulose (hardwood pulp) and 75 g of acetic acid were placed in a separable flask equipped with a reflux apparatus and stirred vigorously for 2 hours while heating in an oil bath adjusted to 60 ° C. The cellulose subjected to such pretreatment was swollen and crushed to form a fluff shape. The reaction vessel was placed in an ice water bath at 2 ° C. for 30 minutes and cooled. Separately, a mixture of 1545 g of propionic anhydride and 10.5 g of sulfuric acid was prepared, cooled to −30 ° C., and then added to the pretreated cellulose at once. After 30 minutes, the external temperature was gradually increased, and the internal temperature was adjusted to 25 ° C. after 2 hours from the addition of the acylating agent. The reaction vessel was cooled in an ice water bath at 5 ° C., and the internal temperature was adjusted to 10 ° C. 3.5 hours after the addition of the acylating agent. 120 g of 25% aqueous acetic acid cooled to 5 ° C. was added over 1 hour. The internal temperature was raised to 40 ° C. and stirred for 1.5 hours. A solution of magnesium acetate tetrahydrate dissolved in 2-fold mol of sulfuric acid in 50% aqueous acetic acid was added and stirred for 30 minutes. 1 L of 25% aqueous acetic acid, 500 ml of 33% aqueous acetic acid, 1 L of 50% aqueous acetic acid and 1 L of water were added in this order to precipitate cellulose acetate propionate. Washing was performed with hot water at 70 ° C. until the pH of the washing solution became 6-7, and then the mixture was stirred in a 0.005 wt% calcium hydroxide aqueous solution at 20 ° C. for 0.5 hours and washed with water. . The obtained cellulose acetate propionate was vacuum dried at 70 ° C. According to ¹ H-NMR and GPC measurement, the obtained cellulose acetate propionate had an acetylation degree of 0.30, a propionylation degree of 2.65, and a polymerization degree of 326.

Comparative Example 1
(Synthesis of cellulose acetate propionate C-1, C-2, cellulose acetate butyrate C-3)
11 g of acetic acid was infiltrated into 10 g of cellulose (hardwood pulp) and left at 20 ° C. for 6 hours. Thereafter, the mixture was vigorously stirred at room temperature for 1 hour. Cellulose subjected to such pretreatment was mixed with fluffy and incompletely swelled sheet. The reaction vessel was placed in an ice water bath at 5 ° C. for 1 hour to sufficiently cool the cellulose. Separately, a mixture of 18 g of acetic anhydride, 62 g of propionic anhydride and 0.5 g of sulfuric acid was prepared, cooled to −20 ° C., and then added to the pretreated cellulose at once. After 30 minutes, the external temperature was raised to 30 ° C. for reaction. It took 12 hours to complete the reaction. The reaction vessel was cooled in an ice water bath at 5 ° C., and 120 g of 25% aqueous acetic acid was added over 30 minutes. The internal temperature was raised to 30 ° C. and stirred for 2 hours. 5 g of a 50% aqueous solution of magnesium acetate tetrahydrate was added and stirred for 30 minutes. 75 g of 25% aqueous acetic acid and 250 g of water were gradually added to precipitate cellulose acetate propionate. Wash with hot water at 70 ° C. until the pH of the cleaning solution becomes 6-7, then leave it in a saturated calcium hydroxide aqueous solution at 20 ° C. for 12 hours, and wash with water until the pH of the cleaning solution becomes 7. went. The obtained cellulose acetate propionate was dried at 70 ° C. According to ¹ H-NMR and GPC measurement, the obtained cellulose acetate propionate, C-1, had a degree of acetylation of 1.42, a degree of propionylation of 1.43, and a degree of polymerization of 224.

Also, comparative compounds C-2 and C-3 were synthesized by the same acylation method as in Synthesis Examples 2 and 3 except that cellulose pretreated at the same low temperature as in Comparative Example 1 was used. . The time required for acylation was 7 hours for C-2 and 9 hours for C-3.
It can be seen that the pretreatment of the production method of the present invention contributes to shortening of the reaction time and is also effective for obtaining a cellulose acylate having a high degree of polymerization.
In addition, other cellulose acylates described in Table 1 (P-2 to P-3, P-5 to P-9, P-11 to P-14, B-1 to B-4, B-6, and B7 ), The amounts of “pretreatment temperature”, “acetic acid” used in the pretreatment, “acetic anhydride”, “propionic anhydride”, “butyric anhydride” used in the acylation, and “ The synthesis was carried out in the same manner as in Synthesis Example 2 under the condition of “acylation reaction time”. “Acylate” in the table represents the synthesized cellulose acylate, “DSAc” represents the substitution degree of the acetyl group, “DSPr” represents the substitution degree of the propionyl group, and “DSBu” represents the substitution degree of the butyryl group. Represent.

Example 2
(Melting film formation)
The measurement method used in the present invention is described below.
(1) Fine Polarized Foreign Material The sample film after melt film formation or after stretching was observed at a magnification of 100 times using a polarizing microscope in which polarizers were orthogonalized. The number of white foreign matters of 1 μm or more and less than 10 μm observed here was visually measured and expressed as the number per 1 mm ² .

(2) Re, Rth measurement After adjusting the above sample film to 25 ° C. and 60% relative humidity for 3 hours or more, using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments), 25 ° C. At a relative humidity of 60%, the retardation value at a wavelength of 550 nm is measured from the direction perpendicular to the sample film surface and tilted by ± 40 ° from the normal to the film surface. It is calculated from the measured values in the in-plane retardation (Re), vertical direction, and ± 40 ° direction from the vertical direction.

(1) Preparation of cellulose acylate As shown in Table 1, cellulose acylates having different types of acyl groups and different degrees of substitution were prepared in the same manner as described above.

(2) Pelletization of cellulose acylate The above cellulose acylate was blown and dried at 120 ° C. for 3 hours, and a plasticizer selected from the following was added to the water content determined by the Karl Fischer method to 0.1 mass%. Furthermore, 0.05 mass% of silicon dioxide part particles (Aerosil R972V) were added to all levels.
Plasticizer A: Triphenyl phosphate
Plasticizer B: Dioctyl adipate A mixture of these was placed in a hopper of a biaxial kneading extruder and kneaded. The biaxial kneading extruder was provided with a vacuum vent and evacuated (set to 0.3 atm).
After melting in this way, it was extruded into a strand having a diameter of 3 mm in a water bath, immersed for 1 minute (strand solidification), passed through 10 ° C. water for 30 seconds, lowered in temperature, and cut to a length of 5 mm. The pellets thus prepared were dried at 100 ° C. for 10 minutes and then packaged.

(3) Melt Film Formation Cellulose acylate pellets prepared by the above method were dried with a vacuum dryer at 110 ° C. for 3 hours. This was put into a hopper adjusted to Tg-10 ° C. and melted at 190 ° C. for 5 minutes, and then the T / D ratio (lip interval / film thickness of film formation) shown in Table 1, casting drum ( CD) and the die distance (the distance between the CD and the die divided by the film formation width and expressed as a percentage). At this time, a film having a desired thickness (D) was obtained by setting the speed of the casting drum to T / D times the extrusion speed.
The casting drum was set to Tg-10 ° C. and solidified thereon to form a film. At this time, each level 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. After stripping off the solidified melt, trimming both ends (5% each of the total width) immediately before winding, and then applying a thicknessing process (knurling) of 10 mm width and 50 μm height to each end, and then winding 3000 m at 30 m / min I took it. The width of the unstretched film thus obtained is 1.5 m at each level, and the thickness is shown in Table 2.

The finely polarized foreign matter in the unstretched cellulose acylate film thus obtained was measured by the above method and listed in Table 2. The film formed from the cellulose acylate obtained by the production method of the present invention showed good characteristics, whereas the ones outside the range of the conditions defined in the production method of the present invention were polarized fine foreign matters. There were especially many.
For comparison, the results of measuring finely polarized foreign matters by the above method using cellulose acetate butyrate manufactured by Eastman Chemical Co., Ltd. are also shown.

Example 3
(Solution casting)
(1) Dissolution of cellulose acylate

A. Solvents Selected from the following solvents and listed in Table 3.
Non-chlorine system 1: methyl acetate / acetone / methanol / ethanol / butanol (80/5/7/5/3, parts by mass)
Non-chlorine 2: methyl acetate / ethanol (300/45, parts by mass)
Chlorine: dichloromethane / methanol / ethanol / butanol (85/6/5/4, parts by mass)

I. Cellulose acylate After drying until the water content became 0.5% or less, cellulose acylate was added so as to be 25 wt% with respect to the solvent, and a dope was prepared as shown in Table 3.

C. Additives The following additives were added to the dope.
Plasticizer A: Triphenyl phosphate (3% by mass)
Plasticizer B: Biphenyl diphenyl phosphate (1% by mass)
Optical anisotropy control agent; compound described in (Chemical Formula 1) described in JP-A-2003-66230 (3% by mass)
UV agent a: 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine (0.5% by mass)
UV agent b: 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole (0.2% by mass)
UV agent c: 2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole (0.1% by mass)
Fine particles: silicon dioxide (particle size 20 nm), Mohs hardness of about 7 (0.25% by mass)
・ Citric acid ethyl ester (monoester and diester mixed 1: 1, 0.2% by mass)
* The above addition amounts (mass%) are all ratios relative to cellulose acylate.

D. Swelling / dissolution The cellulose acylate, solvent and additives were added to the solvent while stirring. When the addition was completed, stirring was stopped and the slurry was swelled at 25 ° C. for 3 hours to prepare a slurry. This was stirred again to completely dissolve the cellulose acylate.

E. Filtration / concentration After that, the mixture was filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (manufactured by Toyo Filter Paper Co., Ltd., # 63), and further filtered with a filter paper having an absolute filtration accuracy of 2.5 μm (manufactured by Pall, FH025).

(2) Formation of unstretched film The above-mentioned dope was heated to 35 ° C. and cast by any of the following methods (described in Table 3).

[Band method]
The film was cast on a mirror surface stainless steel support having a band length of 60 m set at 15 ° C. through a Giesser. The Gieser used was similar to that described in JP-A-11-314233. The casting speed was 60 m / min and the casting width was 250 cm.
After peeling off the residual solvent at 100% by mass, the temperature was raised between 40 ° C. and 120 ° C. at the rate shown in Table 1 (removed temperature), and then dried at 120 ° C. for 5 minutes and further at 145 ° C. for 20 minutes. Then, it slowly cooled at the speed | rate shown in Table 1, and obtained the cellulose triacylate film. The obtained film was trimmed at both ends by 3 cm, and then knurled with a height of 100 μm was imparted to portions 2 mm to 10 mm from both ends, and wound into a 3000 m roll.

[Drum method]
It was cast through a Gieser into a 3 m diameter mirror surface stainless steel drum set at -15 ° C. The Gieser used was similar to that described in JP-A-11-314233. The casting speed was 100 m / min and the casting width was 250 cm.
After peeling off the residual solvent at 200% by mass, the temperature was raised between 40 ° C. and 120 ° C. at the speed shown in Table 1 (removed temperature), and then dried at 120 ° C. for 5 minutes and further at 145 ° C. for 20 minutes. Then, it slowly cooled at the speed | rate shown in Table 1, and obtained the cellulose triacylate film. The obtained film was trimmed at both ends by 3 cm, and then knurled with a height of 100 μm was imparted to portions 2 mm to 10 mm from both ends, and wound into a 3000 m roll.

(4) Characteristic evaluation of unstretched film Re, Rth and the amount of these fine foreign matters were measured by the above-mentioned method, and are listed in Table 3. The film produced from the cellulose acylate obtained by the production method of the present invention showed preferable characteristics in which minute foreign matters were not substantially observed, whereas the cellulose acylate outside the range defined in the production method of the present invention. It can be seen that the product manufactured from the above has a lot of minute foreign matter.
Further, in accordance with Example 1 of the Japan Society for Invention and Innovation Technical Report (Public Technical No. 201-1745), three-layer co-casting using the dope was carried out, and similarly good results were obtained.

Example 4
(Creation of polarizing plate)

(1) Stretching The unstretched film described in Examples 2 and 3 was stretched and stretched by 15% MD at 100% / second and 50% at 20% / second at a temperature 10 ° C. higher than the Tg of each cellulose acylate film. TD stretched. Tg was measured by the following method.
Such stretching was selected from sequential stretching in which transverse stretching was performed after longitudinal stretching and simultaneous biaxial stretching in which longitudinal and lateral stretching were performed simultaneously.

(Tg measurement)
20 mg of sample is placed in the DSC measuring pan. This is heated from 30 ° C. to 250 ° C. at 10 ° C./min in a nitrogen stream (1st-run), and then cooled to 30 ° C. at −10 ° C./min. Thereafter, the temperature is raised again from 30 ° C. to 250 ° C. (2nd-run). Tg (temperature at which the baseline starts to be displaced from the low temperature side) obtained by 2nd-run was used.

(2) Saponification Unstretched and stretched cellulose acylate films were saponified by the following immersion saponification method.

A. Immersion saponification A 1.5 N aqueous solution of NaOH was used as a saponification solution.
The temperature was adjusted to 60 ° C., and the cellulose acylate film was immersed for 2 minutes.
Thereafter, it was immersed in a 0.1N aqueous sulfuric acid solution for 30 seconds and then passed through a water-washing bath.
In addition, although it implemented also with the following coating saponification method, the result similar to the immersion saponification method was shown.

I. Coating Saponification 20 parts by mass of water was added to 80 parts by mass of isopropyl alcohol, and KOH was dissolved in this so as to have a concentration of 1.5 mol / L, and this was adjusted to 60 ° C. and used as a saponification solution.
This was coated on a cellulose acylate film at 60 ° C. at 10 g / m ² and saponified for 1 minute. Thereafter, warm water of 50 ° C. was sprayed and sprayed at 10 L / m ² · min for 1 minute for washing.

(3) Production of Polarizing Film According to Example 1 of JP-A-2001-141926, a peripheral speed difference was given between two pairs of nip rolls, and the film was stretched in the longitudinal direction.

(4) Bonding The polarizing film thus obtained, the saponified unstretched, stretched cellulose acylate film, and the saponified Fujitac (unstretched triacetate film) were combined with PVA (PVA-117H manufactured by Kuraray Co., Ltd.). ) Using a 3% aqueous solution as an adhesive, the polarizing axis and the cellulose acylate film were laminated in the following combination so that the longitudinal direction of the film was 45 degrees.
1 polarizing plate A: stretched cellulose acylate film / polarizing film / unstretched cellulose acylate film 2 polarizing plate B: stretched cellulose acylate film / polarizing film / Fujitack 3 polarizing plate C: stretched cellulose acylate film / polarizing film / stretched Cellulose acylate film The unstretched cellulose acylate used was the same level of unstretched film.

(5) Creation of optical compensation film and liquid crystal display element)
The retardation plate A or B was used in place of a polarizing plate of 15-inch display VL-1530S (VA method) manufactured by Fujitsu Limited. At this time, as described in Table 1, when a polarizing phase difference plate was used on only one side of a pair of polarizing plates, it was described as “one side”, and when used on both polarizing plates, “both sides”. The amount of light leakage of the liquid crystal display device thus obtained was measured according to the method described above.

Light Leakage Evaluation Method The liquid crystal display device was placed in a completely dark room with a black display, and the brightness of the screen was measured with a photometer. The amount of light was divided by the value when the entire surface was displayed in white, and the amount expressed as a percentage was defined as “light leakage amount”.
What used the retardation polarizing plate using the stretched cellulose acylate film of this invention had little light leakage, and was able to produce the favorable optical compensation film. On the other hand, light leakage was remarkable in the case outside the range defined in the production method of the present invention.
Further, even when the stretched cellulose acylate film of the present invention was used in place of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-11-316378, a good optical compensation film could be produced.

In place of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-7-333433, a good optical compensation film can be produced even if an optical compensation filter film is produced by changing to the stretched cellulose acylate film of the present invention. did it.
Further, a polarizing plate and a retardation polarizing plate using the cellulose acylate film of the present invention are described in the liquid crystal display device described in Example 1 of JP-A-10-48420 and in Example 1 of JP-A-9-26572. An optically anisotropic layer containing discotic liquid crystal molecules, an alignment film coated with polyvinyl alcohol, a 20-inch VA liquid crystal display device described in FIGS. 2 to 9 of JP-A-2000-154261, and JP-A-2000-154261 When the 20-inch OCB type liquid crystal display device described in FIGS. 10 to 15 of the publication No. 10 and the IPS type liquid crystal display device described in FIG. Obtained.

Example 5
(Creation of low reflection film)
When the stretched cellulose acylate film of the present invention was used to produce a low reflection film using the stretched cellulose acylate film of the present invention in accordance with Example 47 of the Japan Institute of Invention and Technology (Publication No. 2001-1745), good optical performance was obtained. was gotten.

  Further, the low-reflection cellulose acylate film of the present invention is applied to the liquid crystal display device described in Example 1 of JP-A-10-48420, and the 20-inch VA liquid crystal described in FIGS. 2 to 9 of JP-A-2000-154261. When a display device, a 20-inch OCB type liquid crystal display device described in FIGS. 10 to 15 of JP-A No. 2000-154261, was applied to the outermost layer of the liquid crystal display device, an excellent liquid crystal display element was obtained.

Example 6
(1) Pelletization of cellulose acylate The acylating agent described in Synthesis Example 2 of Example 1 is a mixture of acetic anhydride, propionic anhydride, acetic acid, propionic acid and sulfuric acid, and the acetyl / propionyl ratio in the acylating agent In addition, the cellulose acylate described in Table 4 was synthesized by changing the reaction temperature. In Comparative Examples 1 and 2, cellulose acylates C-1 and C-2 of Example 1 outside the present invention were used, respectively. These cellulose acylates were blown and dried at 120 ° C. for 3 hours to adjust the water content to 0.1% by mass. To this, the plasticizer described in Table 4 and silicon dioxide part particles (Aerosil R972V) 0.05% by mass, phosphite stabilizer (P-1) 0.20% by mass, "UV absorber a" 2, 4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine (0.8% by mass), “UV absorber b” 2 (2′-Hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole (0.25 wt%) is added and the mixture is melted at 190 ° C. using a twin-screw kneading extruder. Kneaded. The biaxial kneading extruder was provided with a vacuum vent and evacuated (set to 0.3 atm). It was extruded into a strand having a diameter of 3 mm in a water bath and cut into a length of 5 mm.

(2) Melt Film Formation Cellulose acylate pellets prepared by the above method were dried with a vacuum dryer at 100 ° C. for 3 hours. This was put into a hopper adjusted to Tg−10 ° C., and a cellulose acylate was melt extruded at the following temperature using a screw with a compression ratio of 3.0 using a single screw extruder.
Screw temperature pattern: Upstream supply section (180-195 ° C)
Intermediate compression section (200-210 ° C)
Downstream metering section (210-240 ° C)

  Next, the melted cellulose acylate was passed through a gear pump to remove the pulsation of the extruder, filtered through a 3 μm filter, and cast onto a cast drum through a 230 ° C. die. At this time, a 3 kV electrode was placed at a distance of 5 cm from the melt, and electrostatic application treatment was performed at both ends of 5 cm. A cellulose acylate film having a thickness shown in Table 4 was obtained by solidifying through three casting drums having a diameter of 60 cm set to Tg-5 ° C, Tg, and Tg-10 ° C. After trimming 5 cm at both ends, a thicknessing process (knurling) with a width of 10 mm and a height of 50 μm was applied to both ends, and a sample with a width of 1.5 m, a film forming speed of 30 m / min, and a winding of 2000 m was taken. A cellulose acylate film having no surface irregularities and unevenness and having an excellent surface shape was obtained.

Re and Rth of the obtained cellulose acylate unstretched film were measured in the same manner as in Example 2 and listed in Table 4. Other physical properties were haze of 0.15%, transparency (transparency) of 93.1%, and molecular orientation axis of 0.3 °. The minute foreign matters measured in the same manner as in Example 2 are also shown in Table 4. In the examples of the present invention, the number of minute foreign matters having a length of 0.02 mm or less was less than 1 piece / m ² , and there was no 0.02 to 0.05 mm, which had excellent characteristics for optical applications. On the other hand, the cellulose acylate film of the comparative example produced by a method other than the present invention had a lot of fine foreign matters, and the performance as an optical film was inferior.

(3) Production of polarizing plate (3-1) Saponification of cellulose acylate film The cellulose acylate 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 acylate 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.

(3-2) 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 the film was stretched in the longitudinal direction to produce a polarizing film having a thickness of 20 μm.

(3-3) Bonding The polarizing film thus obtained, the saponified unstretched and stretched cellulose acylate film, and the saponified Fujitac (unstretched triacetate film) were combined with PVA (PVA manufactured by Kuraray Co., Ltd.). -117H, trade name) 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 flow direction (longitudinal method) of cellulose acylate.
Polarizing plate A: unstretched cellulose acylate film / polarizing film / Fujitac TD80U
Polarizing plate B: unstretched cellulose acylate film / polarizing film / unstretched cellulose acylate film

(3-4) Mounting Evaluation 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 type liquid crystal cells, an observer The polarizing plate on one side was peeled off, and an adhesive was used, and the polarizing plate A or B was attached instead. 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 a black display state, and in-plane uniformity. In Table 4, in the column of evaluation, ○ indicates that there is almost no light leakage and color unevenness, and that there is no problem in serving as a product in terms of in-plane uniformity, × indicates that there are many light leakage and color unevenness, Indicates inappropriateness.

  As is clear from the results in Table 4, the cellulose acylate film of the present invention was very excellent with no color tone change.

(3-5) Preparation of low-reflection film When the cellulose acylate film of the present invention was produced according to Example 47 of the Japan Society for Invention and Innovation (public technical number 2001-1745), a low-reflection film was produced. Indicated.

(3-6) Preparation of optical compensation film A liquid crystal layer was applied to the cellulose acylate film of the invention in accordance with Example 1 of JP-A-11-316378, and a good optical compensation film was obtained.

Claims (15)

A method for producing cellulose acylate satisfying the substitution degree of the following formula,
1) a step of adding at least one of water or a carboxylic acid having 2 to 7 carbon atoms as an activator to cellulose;
2) The manufacturing method of the cellulose acylate characterized by including the process kept at 40 degreeC or more for 1 hour or more.
2.0 ≦ A + B ≦ 3
0 ≦ A ≦ 2.5
0.3 ≦ B ≦ 3
(A represents the substitution degree of the acetyl group, and B represents the total substitution degree of the acyl group having 3 to 7 carbon atoms.) A method for producing cellulose acylate satisfying the substitution degree of the following formula,
1) a step of adding at least one of water or a carboxylic acid having 2 to 7 carbon atoms as an activator to cellulose;
2) A process of maintaining at 40 ° C. or more for 1 hour or more
3) a step of cooling the cellulose to −30 ° C. or higher and lower than 30 ° C. before acylation;
4) A step of adding an acid anhydride of a carboxylic acid having 2 to 7 carbon atoms to the cellulose thus treated, and acylating the hydroxyl group of the cellulose in the presence of Bronsted acid;
A method for producing cellulose acylate, comprising:
2.0 ≦ A + B ≦ 3
0 ≦ A ≦ 2.5
0.3 ≦ B ≦ 3
(A represents the substitution degree of the acetyl group, and B represents the total substitution degree of the acyl group having 3 to 7 carbon atoms.)   The method for producing a cellulose acylate according to claim 1 or 2, wherein the activator added to the cellulose is a carboxylic acid having 2 to 7 carbon atoms.   The said acylating agent added with respect to a cellulose is selected from an acetic acid, a propionic acid, or a butyric acid, The manufacturing method of the cellulose acylate of any one of Claims 1-3 characterized by the above-mentioned.   The said acylating agent added with respect to a cellulose is an acetic acid, The manufacturing method of the cellulose acylate of any one of Claims 1-4 characterized by the above-mentioned.   The method for producing cellulose acylate according to any one of claims 1 to 5, wherein the time for keeping the cellulose at 40 ° C or more together with the activating agent is 1 hour or more and 100 hours or less.   The method for producing cellulose acylate according to any one of claims 1 to 6, wherein the cellulose is kept at 60 ° C or higher and 90 ° C or lower together with the activator.   The method for producing cellulose acylate according to any one of claims 2 to 7, wherein the Bronsted acid is sulfuric acid.   The method for producing a cellulose acylate according to any one of claims 2 to 8, wherein a maximum reached temperature in the acylating step is 50 ° C or lower.   The method for producing cellulose acylate according to any one of claims 2 to 9, wherein a reaction terminator is added over 3 minutes to 3 hours after the acylating step.   The method for producing a cellulose acylate according to claim 10, wherein the reaction terminator is acetic acid containing 5% by mass to 80% by mass of water.   A cellulose acylate film produced by casting a cellulose acylate produced by the production method according to any one of claims 1 to 11 by solution casting.   A cellulose acylate film produced by melt casting a cellulose acylate produced by the production method according to claim 1. The cellulose acylate film according to claim 12 or 13, wherein the in-plane retardation (Re) and the thickness direction retardation (Rth) satisfy the following formula.
Rth ≧ Re
300 ≧ Re ≧ 0
500 ≧ Rth ≧ 0 The polarizing plate which has at least 1 sheet of the cellulose acylate film of any one of Claims 12-14 as a protective film of a polarizing film.