JP4734379B2 - Method for producing cellulose acylate film - Google Patents

Description

  The present invention relates to a method for producing a cellulose acylate film.

Cellulose acylate films are used in various photographic materials and optical materials because of their toughness, flame retardancy, and optical isotropy. These cellulose acylate films are generally produced by a solvent cast (solution casting) method. That is, a solution (dope) in which cellulose acylate is dissolved is cast on a support, and the solvent is evaporated to form a film. Conventional solvent 70 wt% or more including salts Motokei solvent Axis chloromethane has been used.
However, these chlorinated solvents have been studied replacement from the viewpoint of environmental protection to non-chlorinated solvent agent. For example, acetone, methyl acetate, tetrahydrofuran, 1,3-dioxolane, nitromethane, 1,4-dioxane, epichlorohydrin, N-methylpyrrolidone and the like are known. However, these solvents are not practical because they cannot be dissolved at a sufficiently high concentration, cannot be dried because the boiling point is too high, and are liable to generate a peroxide during drying, which may cause explosion.
Patent Documents 1 to 3 disclose a method of cooling and dissolving after dispersing in a non-chlorinated solvent such as ether, ketone (eg, acetone) or ester (eg, methyl acetate). However, in these methods, continuous film formation for a long time is likely to cause an increase in filtration pressure due to clogging, and a tailing failure due to noro generated in the casting die, and improvement has been desired.
JP-A-9-95544 JP-A-9-95538 Japanese Patent Laid-Open No. 10-45804

  It is an object of the present invention to provide a method for producing a cellulose acylate film having excellent long-term continuous film-forming properties.

The said subject of this invention can be achieved by implementing the method of following (1)-(11).
(1) The cellulose acylate is washed with an acetone / water mixed solvent having a mixing weight ratio of 0.2 / 0.8 to 0.8 / 0.2, thereby adjusting the iron content to 0 ppm to 50 ppm. Step: Cellulose acylate having an iron content of 0 ppm to 50 ppm and a water content of 0% to 0.5% is dissolved in an organic solvent, and the cellulose acylate is dissolved so that the radius of inertia is 40 nm to 200 nm. A method for producing a cellulose acylate film, comprising : preparing a cellulose acylate solution, and forming a film of the cellulose acylate solution.

(2) The method for producing a cellulose acylate film according to (1), wherein the iron content of the cellulose acylate is adjusted to 0 ppm or more and 20 ppm or less.
(3) The method for producing a cellulose acylate film according to (1), wherein the viscosity average polymerization degree of the cellulose acylate is 250 to 550 .
(4) The method for producing a cellulose acylate film according to (1) , wherein the cellulose acylate is washed by stirring in an acetone / water mixed solvent at a temperature of 30 ° C. to 70 ° C. for 30 minutes to 3 hours.
(5) The method for producing a cellulose acylate film according to (4), wherein the cellulose acylate is washed by stirring in an acetone / water mixed solvent at a temperature of 40 ° C. to 60 ° C. for 50 minutes to 2 hours.

(6) The method for producing a cellulose acylate film according to (1) , wherein washing is performed 2 times or more and 5 times or less.

(7) The method for producing a cellulose acylate film according to (1), wherein the water content of the cellulose acylate is 0% or more and 0.2% or less.
(8) The method for producing a cellulose acylate film according to (1) , wherein the cellulose acylate is washed and then dried at 80 ° C. to 200 ° C. for 10 minutes to 10 hours.
(9) The method for producing a cellulose acylate film according to (8), wherein the cellulose acylate is washed and then dried at 110 ° C. to 160 ° C. for 30 minutes to 5 hours.

(10) The cellulose acyl according to (1), wherein the organic solvent is selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms. A method for producing a rate film.

(11) The method for producing a cellulose acylate film according to (1), wherein the step of dissolving cellulose acylate in an organic solvent is performed in dry air or dry nitrogen .

The present invention has achieved a method for producing a cellulose acylate film having excellent long-term continuous film-forming properties by improving the method for dissolving a cellulose acylate solution (dope).
For example, in a method for producing a cellulose acylate film by dissolving cellulose acylate in an organic solvent, casting the cellulose acylate solution, and drying the solution, the inertial square radius of the cellulose acylate solution is 40 nm or more and 200 nm. A cellulose acylate film excellent in long-term continuous film-forming properties can be obtained by a method for producing a cellulose acylate film that dissolves as follows.

Examples of cellulose as a cellulose acylate raw material include cotton linter and wood pulp. You may mix and use raw material cellulose. The cellulose acylate obtained from these celluloses satisfies the following formulas (I) to (III) in terms of the degree of substitution of cellulose with hydroxyl groups. Further, the following (IV) may be satisfied.
(I) 2.6 ≦ A + B ≦ 3.0
(II) 2.0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 0.8
(IV) 1.9 <AB

In the formula, A and B represent a substituent of an acyl group substituted with a hydroxyl group of cellulose, A is a substitution degree of an acetyl group, and B is a substitution degree of an acyl group having 3 to 5 carbon atoms. Cellulose has three hydroxyl groups in one glucose unit, and the above number represents the degree of substitution with respect to the hydroxyl group 3.0, and the maximum degree of substitution is 3.0. The degree of substitution can be obtained by calculating the degree of binding of acetic acid substituted with a hydroxyl group of cellulose and a fatty acid having 3 to 5 carbon atoms. As a measuring method, it can carry out according to ASTM D-817-91.
Those with B = 0 are called triacetylcellulose (TAC), while those with B> 0 are also called cellulose mixed fatty acid esters. More preferred is TAC.
TAC satisfies the formulas (V) and (VI).
(V) 2.6 ≦ A ≦ 3.0
(VI) 0 = B

The cellulose mixed fatty acid ester contains an acyl group having 3 to 5 carbon atoms in addition to the acetyl group, and is preferably a propionyl group (C ₂ H ₅ CO—), a butyryl group (C ₃ H ₇ CO—) ( n-, an iso-), valeryl _{(C 4 H 9 CO -)} (n-, iso-, sec-, tert-) are preferred, propionyl group is preferred.
As an acylating agent for these acyl groups, in the case of an acid anhydride or acid chloride, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent. As the catalyst, a protic catalyst such as sulfuric acid is preferably used. When the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), a basic compound is used. The most common method in the industry is to use cellulose for fatty acids corresponding to acetyl groups and other acyl groups (acetic acid, propionic acid, butyric acid, valeric acid) or their anhydrides (acetic anhydride, propionic anhydride, butyric anhydride). The cellulose acylate is synthesized by acylation with a mixed organic acid component containing valeric anhydride. About a specific manufacturing method, it is compoundable by the method described in Unexamined-Japanese-Patent No. 10-45804, for example.
The degree of polymerization (viscosity average) of the cellulose acylate of the present invention is preferably 200 to 700, more preferably 250 to 550, and still more preferably 250 to 350. Thereby, the mechanical strength can be satisfied. The viscosity average degree of polymerization can be measured with an Ostwald viscometer, and is determined from the measured intrinsic viscosity [η] of cellulose acylate by the following formula.
DP = [η] / Km (where DP is the viscosity average degree of polymerization and Km is a constant 6 × 10 ⁻⁴ )

Such cellulose acylate is dissolved in a solvent, but the present invention dissolves so as to satisfy the following requirements.
(1) Dissolve so that the radius of inertia is 40 nm to 200 nm, more preferably 45 nm to 170 nm, and still more preferably 50 nm to 150 nm. In the conventional dissolution method, polymer molecules such as cellulose acylate are completely dissolved. In contrast, the present invention is characterized in that cellulose acylate molecules are associated in a solution to increase the radius of inertia. In other words, by intentionally forming an aggregate, minute nuclei are formed, and generation of large aggregates (noro) that cause filtration clogging and tailing is suppressed. On the other hand, the inertial square radius of cellulose acylate which is dissolved by the conventional method and does not form an association is 10 to 20 nm.

(2) The second virial coefficient is −2 × 10 ⁻⁴ or more and 4 × 10 ⁻⁴ or less, more preferably −1.5 × 10 ⁻⁴ or more and 3 × 10 ⁻⁴ or less, and further preferably −1.0 × 10. ^-4 or more and 2.5 x 10 ^-4 or less. The second virial coefficient is an index indicating the affinity between the polymer molecule and the solvent. The higher the absolute value in the positive direction, the higher the affinity, and the higher the absolute value in the negative direction, the lower the affinity. Is shown. In general, the second virial coefficient is 8 × 10 ⁻⁴ or more when completely dissolved, but in such a state, the polymer molecule is likely to increase in viscosity because the molecular chain is widened. Even if a tailing fault occurs, it is difficult to level and disappear. On the other hand, the molecular chain is folded compactly within the range of the second virial coefficient of the present invention, and the viscosity is hardly increased. As a result, the tailing failure is easy to eliminate.

(3) The weight average molecular weight of the cellulose acylate in the solution determined by the light scattering method is 300,000 to 4,000,000, more preferably 400,000 to 2,000,000, more preferably 500,000 to 1,200,000. Dissolve in When the molecular weight is obtained by the light scattering method, it is measured without applying an external stress, and thus the measured value more reflects the association state. (On the other hand, when a shear stress is applied in the column as in the GPC (gel permeation chromatography) method, the molecular weight of a single molecule is obtained because the measurement is performed while destroying the association state.) In the solution used in the present invention When the molecular weight of the cellulose acylate is measured by the GPC method, it is 50,000 to 180,000. That the weight average molecular weight calculated | required by the light-scattering method is larger than the weight average molecular weight measured by GPC method means that the aggregate is formed.
The formation of such an aggregate can improve the peelability from the support of the solution casting film forming apparatus during film formation. When a cellulose acylate film is formed by the solution casting film forming method, the cellulose acylate solution is cast on a support (band or drum), then the solvent is volatilized and peeled off from the support and further dried. Film. In the cellulose acylate solution that does not form an aggregate, cellulose acylate molecules are dissolved and solvated. Therefore, when a cellulose acylate solution that does not form an aggregate is cast, the volatilization of the solvent is delayed at the time of drying on the support, and it takes time to peel off. Therefore, the casting film forming speed cannot be increased. On the other hand, when a cellulose acylate solution forming an aggregate is used, since the solution is not solvated, the drying efficiency is good and the film formation rate can be increased.

(4) Melting is performed so that the heat of dissolution is 100 J / g or more and 900 J / g or less, more preferably 200 J / g or more and 800 J / g or less, more preferably 300 J / g or more and 700 J / g or less. When dissolved at the molecular level by a normal method, it is 20 to 30 J / g. On the other hand, in the present invention, an aggregate is formed as described in (1) above, and heat is generated at that time. Therefore, by setting the heat of dissolution within this range, generation of noro can be suppressed.
(5) It is dissolved so that the reduced viscosity is 0.1 or more and 0.3 or less, more preferably 0.12 or more and 0.27 or less, and further preferably 0.14 or more and 0.24 or less. Usually, the viscosity of the cellulose acylate solution well dissolved at the molecular level is 0.5 or more, but in the present invention, it is folded compactly as described in the above (2) and becomes the reduced viscosity. As a result, it is effective in reducing tailing faults.

A cellulose acylate solution having such characteristics can be achieved by the following method.
In other words, the present invention finds that the association inhibitor is water and iron molecules.
(1) The iron content in cellulose acylate is 0 ppm to 50 ppm, more preferably 0 ppm to 30 ppm, and still more preferably 0 ppm to 20 ppm. Such a cellulose acylate is a final step of acylating cellulose, using an acetone / water (0.2: 0.8 to 0.8: 0.2) mixed solvent, 30 ° C. or more and 70 ° C. or less, More preferably, it is 35 ° C. or more and 65 ° C. or less, more preferably 40 ° C. or more and 60 ° C. or less, 30 minutes or more and 3 hours or less, more preferably 40 minutes or more and 2.5 hours or less, more preferably 50 minutes or more and 2 hours or less This can be achieved with sufficient agitation. That is, iron can be completely washed to the inside by swelling cellulose acylate with acetone. This washing is preferably carried out 1 to 5 times, more preferably 2 to 5 times, and even more preferably 2 to 4 times. Then, it is filtered, dried and used for dissolution.

(2) The water content of cellulose acylate before dissolution is 0% to 0.5%, more preferably 0% to 0.3%, and still more preferably 0% to 0.2%. For this, the cellulose acylate film is dissolved at 80 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 180 ° C. or lower, more preferably 110 ° C. or higher and 160 ° C. or lower, more preferably 10 minutes or longer and 10 hours or shorter, more preferably before dissolution. It is achieved by drying for 20 minutes or more and 8 hours or less, more preferably 30 minutes or more and 5 hours or less. This drying may be performed in the air or under vacuum, but the latter is more efficient.
(3) Dissolution is performed in dry air or in an inert gas. Thereby, water vapor mixed into the solvent during dissolution can be reduced, and the water concentration in the solution can be reduced.

Cellulose has three hydroxyl groups (second, third, and sixth positions) per glucose unit. The substitution rate of the hydroxyl group at the 6-position with an acyl group is 30% or more and 40% or less, more preferably 31% or more and 39% or less, and further preferably 32% or more and 38% or less, promoting the formation of aggregates. can do.
In general, the hydroxyl groups at the 2, 3, and 6 positions of cellulose are not evenly substituted by 1/3 by an acyl group. The substitution rate of the hydroxyl group at the 6-position with an acyl group is less than that at the 2- and 3-positions, and the substitution rate at the 6-position is usually 28%. The present invention is characterized in that the substitution rate at the 6-position is increased. Thereby, it becomes easy to form an aggregate and the drying efficiency of the cellulose acylate solution can be increased. The hydroxyl groups at positions 2 and 3 of cellulose are directly bonded to the glucopyranose ring, but the hydroxyl group at position 6 is bonded via a methylene group, so that the acyl group bonded to position 6 is more mobile, It tends to be entangled with other molecules. It is presumed that this becomes a weak cross-linked structure and easily forms an aggregate.

Further, when cellulose acylate having a 6-position substitution rate of 30% to 40%, more preferably 31% to 39%, and further preferably 32% to 38% is used, formation of aggregates can be promoted. .
Generally, the hydroxyl groups at the 2, 3, and 6 positions of cellulose acylate are not evenly distributed by 1/3, but the degree of acetylation of the hydroxyl group at the 6 position is less than that at the 2 and 3 positions, and the substitution at the 6 position is usually performed. The rate is 28%. The present invention is characterized in that the acylation rate at the 6-position is increased. This makes it easy to form an aggregate and can impart the dissolved physical properties of the present invention. In other words, the hydroxyl groups at positions 2 and 3 are directly attached to the glucopyranose ring, but the hydroxyl group at position 6 is attached via a methylene group, so that the acetyl group substituted here is more mobile, Prone to entanglement. It is presumed that this becomes a weak cross-linked structure and easily forms an aggregate.
Such a cellulose acylate having a high 6-degree acetylation can be prepared as follows with reference to JP-A-11-5851.
Cellulose raw materials such as wood pulp are pretreated with an appropriate amount of acetic acid, then put into a precooled acetylated mixture to be acylated ester, and complete cellulose acylate (with 2-, 3- and 6-position acyl substitution degrees) The total is approximately 3.00). By maintaining this at 50 to 90 ° C. in the presence of a small amount of acetylation reaction catalyst (generally, remaining sulfuric acid), saponification aging is carried out to change to cellulose acylate having a desired degree of acetyl substitution and degree of polymerization. . At this time, reducing the amount of the sulfuric acid catalyst and increasing the time of the acetylation reaction are the points that increase the 6-position substitution degree. When the sulfuric acid catalyst is large, the progress of the acetylation reaction is accelerated, but a sulfate ester is formed between the cellulose and the cellulose according to the amount of the catalyst, and is released at the end of the reaction to generate a residual hydroxyl group. Sulfate esters are more produced at the 6-position, which is highly reactive. Therefore, when there is much sulfuric acid catalyst, the acyl substitution degree of 6-position will become small.
Thereafter, the catalyst remaining in the system is neutralized, or the cellulose acylate solution is put into water or dilute sulfuric acid without neutralization (or water or dilute sulfuric acid is added to the cellulose acylate solution). The cellulose acylate is separated, and the cellulose acylate is obtained by washing and stabilizing treatment.

The formation of such an aggregate is particularly noticeable in a non-chlorinated solvent. Substantially non-chlorine-based solvent means that the content of the solvent containing one or more chlorine atoms in the structural formula is 0 vol% or more and 40 vol% or less, more preferably 0 vol% or more and 15 vol% or less, and further preferably 0 vol%. . Examples of the solvent containing one or more chlorine atoms in the structural formula include halogenated hydrocarbons having 1 to 7 carbon atoms, specifically, dichloromethane, dichloroethane, chlorobenzene, and the like.
The non-chlorine solvent, which is the main solvent occupying 60 vol% or more and 100 vol% or less of the solvent, more preferably 85 vol% or more and 100 vol% or less, more preferably 100 vol%, is an ether or carbon atom number of 3 to 12 carbon atoms. It is preferable to use at least one kind of a ketone having 3 to 12 carbon atoms or an ester having 3 to 12 carbon atoms. These ethers, ketones and esters may have a linear structure, a branched structure or a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used.

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 ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone.
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 the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, methyl acetoacetate, 2-methoxyethanol and 2-butoxyethanol.
These solvents may be used alone or in combination.

The substantially non-chlorinated solvent of the present invention more preferably contains an alcohol. The alcohol is preferably a monoalcohol having 1 to 8 carbon atoms, or a dialcohol, and more preferably methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol. 2-methyl-2-butanol and cyclohexanol. These may be added alone or in admixture of two or more. These alcohols are 0 vol% or more and 40 vol% or less in all solvents, more preferably 3 vol% or more and 30 vol% or less, and further preferably 5 vol% or more and 20 vol% or less.
Preferred combinations of these solvents in the present invention include the following.
Cellulose acylate / methyl acetate / cyclohexanone / methanol / ethanol (= X / (70-X) / 20/5/5, parts by weight)
Cellulose acylate / methyl acetate / methyl ethyl ketone / acetone / methanol / ethanol (= X / (50-X) / 20/20/5/5, parts by weight)
Cellulose acylate / acetone / methyl acetoacetate / ethanol (= X / (75-X) / 20/5, parts by weight)
Cellulose acylate / methyl acetate / 1,3-dioxolane / methanol / ethanol (= X / (70-X) / 20/5/5, parts by weight)
Cellulose acylate / methyl acetate / dioxane / acetone / methanol / 1-butanol (= X / (60-X) / 20/12/5/3, parts by weight)
Cellulose acylate / acetone / cyclopentanone / methanol / ethanol (= X / (60-X) / 30/5/5, parts by weight)
Cellulose acylate / 1,3-dioxolane / cyclohexanone / methyl ethyl ketone / methanol / ethanol (= X / (55-X) / 20/10/5/5/5, parts by weight)
Here, X represents a weight part of cellulose acylate, preferably 10 to 25, and particularly preferably 15 to 23.

The solvent of the present invention may contain a fluoroalcohol having 2 to 10 carbon atoms in an amount of 10% by weight or less based on the total amount of the solvent. Specific examples include 2-fluoroethanol, 2,2,2-trifluoroethanol, and 2,2,3,3-tetrafluoro-1-propanol.
In addition, an aromatic or aliphatic hydrocarbon having 5 to 10 carbon atoms may be added in an amount of 0 vol% to 10 vol%. Examples include cyclohexane, hexane, benzene, toluene, and xylene.
The viscosity of the cellulose triacetate solution immediately before film formation may be within a range that allows casting, and is usually adjusted to a range of 10 ps · s to 2000 ps · s, particularly 30 ps · s to 400 ps. -S is preferable. At this time, it is more preferable to fill the container with an inert gas such as nitrogen gas.

These dissolutions may be carried out at room temperature (room temperature dissolution method), but more associated by dissolving with cooling as described below (cooling dissolution method) or by dissolution under high temperature and pressure (high temperature dissolution method). Formation is promoted. These may be carried out alone or in combination.
In the cooling dissolution method, first, cellulose acylate is gradually added to an organic solvent with stirring at a temperature around room temperature (-10 to 40 ° C.). When using a plurality of solvents, the order of addition is not particularly limited. For example, after cellulose acylate is added to the main solvent, another solvent (for example, a gelling solvent such as alcohol) may be added, or conversely after the gelling solvent is preliminarily wetted with cellulose acylate. The main solvent may be added, which is effective in preventing non-uniform dissolution. The amount of cellulose acylate is preferably adjusted so as to be contained in the mixture in an amount of 10 to 40% by weight. The amount of cellulose acylate is more preferably 10 to 30% by weight. Furthermore, you may add the arbitrary additive mentioned later in a mixture.
Next, the mixture is cooled to -100 to -10 ° C, more preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C. The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). The cooling rate is preferably as high as possible, and is preferably 100 ° C./second or more. Also, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling.
When cooled to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.) after cooling, a solution in which cellulose acylate flows in an organic solvent is obtained. The temperature may be increased by simply leaving it at room temperature or in a warm bath.
Further, if the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.
These cooling and heating operations may be performed once or may be repeated twice or more.

In the high-temperature dissolution method, cellulose acylate is gradually added to an organic solvent with stirring at a temperature around room temperature (-10 to 40 ° C.). When using a plurality of solvents, the order of addition is not particularly limited. For example, after cellulose acylate is added to the main solvent, another solvent (for example, a gelling solvent such as alcohol) may be added, or conversely after the gelling solvent is preliminarily wetted with cellulose acylate. The main solvent may be added, which is effective in preventing non-uniform dissolution. The cellulose acylate solution of the present invention is preferably swollen beforehand by adding cellulose acylate to a mixed organic solvent containing various solvents. In that case, the cellulose acylate may be gradually added to any solvent at −10 to 40 ° C. with stirring, and in some cases, a specific solvent may be added in advance followed by another combined solvent. It may be mixed to obtain a uniform swelling solution, and the remaining solvent may be added after swelling with two or more solvents.
The dissolution concentration of cellulose acylate is preferably 5 to 30% by weight, more preferably 15 to 30% by weight, and still more preferably 17 to 25% by weight.
Next, the cellulose acylate and the solvent mixed solution are 70 to 240 ° C., more preferably 80 to 220 ° C., more preferably 100 to 200 ° C., most preferably 100 to 200 ° C. under a pressure of 0.2 Mp to 30 Mpa in a pressure vessel. Heat to 190 ° C.
Then, it cools below the lowest boiling point of the solvent used. In that case, it is common to cool to -10-50 degreeC and to return to a normal pressure. The cooling may be left at room temperature, more preferably a coolant such as cooling water may be used.
These heating and cooling pedestals may be performed once or repeated twice or more.

An additive can be added to the cellulose acylate solution (dope) of the present invention. Preferable additives include plasticizers, and specifically, phosphoric acid esters, carboxylic acid esters, and glycolic acid esters are used.
Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate. Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetyl citrate (OACTE) and tributyl O-acetyl citrate (OACTB), acetyl triethyl citrate, acetyl tributyl citrate.
Examples of the carboxylic acid ester include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters.
Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, and butyl phthalyl butyl glycolate.
Among these, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl hexyl phthalate, triacetin, and ethyl phthalyl ethyl glycolate are preferable. In particular, triphenyl phosphate, diethyl phthalate, and ethyl phthalyl ethyl glycolate are preferable.
These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 5 to 30% by weight, particularly preferably 8 to 16% by weight, based on the cellulose acylate. These compounds may be added together with cellulose acylate and a solvent during the preparation of the cellulose acylate solution, or may be added during or after the solution preparation.

  In the present invention, as a plasticizer for reducing the optical anisotropy, (di) pentaerythritol esters described in JP-A No. 11-124445, glycerol esters described in JP-A No. 11-246704, JP-A No. 2000-63560 The diglycerol esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946, and the like are preferably used.

In the present invention, deterioration inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) and UV inhibitors may be added. These are disclosed in JP-A-3-199201, 5-1907073, 5-194789, 5-271471, 6-107854, 6-118233, 6-148430, 7-11056. Nos. 8-29619, 8-239509, and 7-11056.
As an example of a preferable deterioration preventing agent, butylated hydroxytoluene (BHT) can be mentioned. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by weight of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by weight.
As a preferable UV inhibitor, a hindered phenol compound is preferable, and 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxy) is preferable. Phenyl) 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. . In particular 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 most preferred. Further, 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-butyl) A phosphorus processing stabilizer such as phenyl) phosphite may be used in combination. The addition amount of these ultraviolet light inhibitors is preferably 1 ppm to 1.0% by weight with respect to cellulose acylate, more preferably 10 to 1000 ppm.

In the present invention, a colorant compound for preventing light piping may be added. The content of the colorant is preferably from 10 to 1000 ppm, more preferably from 50 to 500 ppm, by weight with respect to cellulose acylate.
Further, in the present invention, thermal stabilizers such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, alumina and the like, and alkaline earth metal salts such as calcium and magnesium, antistatic agents, It is also preferable to add a flame retardant, a lubricant, an oil agent or the like.

In the present invention, the dope thus prepared is cast and dried to form a film, but it is also preferable to thicken the dope in advance in order to reduce the load in the drying process as much as possible. Although the method of thickening is not specifically limited, For example, the following method is mentioned.
(1) The low concentration solution is guided between the cylinder and the rotation trajectory of the outer periphery of the rotating blade rotating in the circumferential direction, and the high concentration solution is removed while evaporating the solvent by giving a temperature difference between the solution and the solution. A method of obtaining (for example, JP-A-4-259511).
(2) A method in which a heated low-concentration solution is blown into the container from the nozzle, the solvent is flash-evaporated between the nozzle and the inner wall of the container, and the solvent vapor is extracted from the container to extract the high-concentration solution from the bottom (For example, the methods described in US Pat. Nos. 2,410,212, 2,858,229, 4,414,341, and 4,504,355).

For the film formation of the cellulose acylate of the present invention, a solution casting film forming method and a solution casting film forming apparatus conventionally used for cellulose triacetate film production are used.
A dope having a solid content of 10 to 40% prepared from a dissolving machine (kettle) is temporarily stored in a tank, and bubbles contained in the dope are defoamed, or using an appropriate filter medium such as a wire net or flannel, Remove foreign matters such as undissolved matter, dust and impurities by filtration. The dope is fed from the storage tank to the casting part through a pressurized metering gear pump capable of feeding a metered amount with high accuracy by, for example, the number of rotations.
The casting method is as follows: (1) A method of uniformly extruding a dope from a pressure die onto a support; (2) A doctor blade for adjusting the film thickness of the dope once cast on the support with a blade. (3) or a method using a reverse roll coater adjusted with a reverse rotating roll, etc., but the method using the pressure die of (1) is preferred. Although there exist a coat hanger type, a T-die type, etc. in a pressurization die, all can be used preferably and it is installed above a support.

Two or more pressure dies may be installed to co-cast two or more cellulose acylate solutions. Specifically, the following methods are mentioned.
(1) A solution containing cellulose acylate is cast and laminated from a plurality of casting ports provided at intervals in the traveling direction of the support (for example, Japanese Patent Laid-Open No. 61-158414, Japanese Patent Laid-Open No. 1-122419). And the method described in JP-A-11-198285 can be applied).
(2) Casting a cellulose acylate solution from two casting ports (for example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-61-104813, The methods described in JP-A 61-158413 and JP-A 6-134933 can be applied).
(3) A casting method in which a flow of a high-viscosity cellulose acylate solution is wrapped with a low-viscosity cellulose acylate solution, and the high- and low-viscosity cellulose acylate solution is simultaneously extruded (described in JP-A-56-162617) Method is applicable).
(4) Using two casting ports, the film cast on the support is peeled off by the first casting port, and the second casting is performed on the side in contact with the support surface (Japanese Examined Patent Publication 44- The method described in No. 20235 can be applied).
These co-cast cellulose acylate solutions may be the same solution or different cellulose acylate solutions, and are not particularly limited. A plurality of functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorption layer, and a polarizing layer) can be cast at the same time.

The dope thus extruded is uniformly cast on a support (band or drum running endlessly). The surface of the support is preferably finished in a mirror state, and a drum that is mirror-finished by chrome plating or a stainless steel band that is mirror-finished by surface polishing is preferred. The surface temperature of these supports is preferably 10 ° C. or less.
The raw dry dope film (also referred to as a web) is peeled off from the support at the peeling point where the support has almost gone around. During this time, the point is to volatilize the solvent from the dope to obtain the desired residual solvent. That is, when the solvent concentration in the vicinity of the belt surface in the thickness direction of the dope film is too high, the dope remains on the belt when it is peeled off, which hinders the next casting. Furthermore, a web strength sufficient to withstand the peeling force is required. The amount of residual solvent at the time of peeling differs depending on the drying method on the belt or drum, and the method of transferring heat from the belt or drum back is more effective than the method of drying by blowing air from the dope surface. Can be reduced.
The dope is generally dried by a method in which hot air is applied from the surface of the support (drum or belt), that is, from the surface of the dope on the support, a method in which hot air is applied from the back of the drum or belt, or a temperature-controlled liquid. There is a liquid heat transfer method in which the surface of the drum or belt is heated by heat transfer to control the surface temperature by contacting the belt or drum from the back side opposite to the dope casting surface of the belt or drum, but the back surface liquid heat transfer method is preferred. The surface temperature of the support before casting may be any number as long as it is not higher than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose fluidity on the support, the temperature should be set to 1 to 10 ° C. lower than the boiling point of the lowest boiling solvent among the solvents used. Is preferred. A preferable drying temperature is 40 to 250 ° C, particularly 70 to 180 ° C. Further, in order to remove the residual solvent, it is preferably used to dry at 50 to 160 ° C., and in that case, the residual solvent is evaporated by drying with high-temperature air whose temperature is changed successively. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. The drying temperature, the amount of drying air, and the drying time differ depending on the solvent used, and may be appropriately selected according to the type and combination of the solvents used. The residual solvent amount of the final finished film is preferably 2% by weight or less, and more preferably 0.4% by weight or less in order to obtain a film having good dimensional stability.

  In the drying process of the web peeled from the support, the film tends to shrink in the width direction, and the shrinkage increases as the film is dried at a higher temperature. Drying while suppressing the shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point, for example, a method of drying the entire drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 while holding the width at both ends of the web with a clip in the width direction (tenter method) ) Is preferred.

In the present invention, it is also preferable to positively stretch the dried web (film) in the width direction. For example, the methods described in JP-A-62-115035, JP-A-4-152125, JP-A-4284221, JP-A-4-298310, JP-A-11-48271 and the like can be used. Thereby, the in-plane retardation value of the cellulose acylate film can be controlled. That is, the retardation value can be increased by stretching the film.
The film is stretched at room temperature or under heating conditions. The heating temperature is preferably not higher than the glass transition temperature of the film. The film may be stretched uniaxially or biaxially. The film can be stretched by a treatment during drying, and is particularly effective when the solvent remains. For example, by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed, the film is stretched. The film can also be stretched by conveying the film while holding it with a tenter and gradually widening the tenter. After the film is dried, it can be uniaxially stretched using a stretching machine.
The preferred film draw ratio (the ratio of the increase due to stretching relative to the original length) is 10 to 30%.
These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas.

The winder relating to the production of the cellulose acylate film of the present invention may be generally used, such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, etc. It can be wound up by the method.
The thickness (after drying) of the cellulose acylate film of the present invention varies depending on the purpose of use, but is usually in the range of 5 to 500 μm, more preferably in the range of 40 to 250 μm, and most preferably in the range of 30 to 150 μm. preferable. The film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the support speed, and the like so as to obtain a desired thickness.
In addition to these film forming methods, various known methods for casting a cellulose triacetate solution (for example, JP-A-61-94724, JP-A-61-148013, JP-A-4-85011, JP-A-4850) -286611, 5-185443, 5-185445, 6-278149, 8-207210, etc. can be preferably used, taking into account differences in the boiling point of the solvent used, etc. By setting each condition, the same effects as described in the respective publications can be obtained.
The cellulose acylate film of the present invention may be provided with an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. by coating after film formation.
As a material of the conductive layer of the present invention, a conductive metal oxide or a conductive polymer is preferable. A transparent conductive film by vapor deposition or sputtering may be used. Examples of metal oxides are preferably ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₂ , V ₂ O ₅ , or a composite oxide thereof. In particular, ZnO, SnO ₂ or V ₂ O ₅ is preferable. As examples of hetero atoms of the composite oxide, addition of Al, In, Ta, Sb, Nb, halogen, and Ag is effective, and the addition amount is preferably in the range of 0.01 mol% to 25 mol%. Further, the volume resistivity of these conductive metal oxide powders is 107 Ω-cm, particularly 105 Ω-cm or less, and the primary particle diameter is 10 nm or more and 0.2 μm or less. It is preferable that the conductive layer contains a powder having a specific structure having a major axis of 30 nm or more and 6 μm or less in a volume fraction of 0.01% or more and 20% or less. The amount of the conductive fine particles is preferably 0.01~5.0g / ^{m 2,} in particular 0.005~1g / ^{m 2} is preferred.
For the conductivity of the present invention, the conductive fine particles may be dispersed in a binder and provided on the support layer, or the support may be subjected to a subbing treatment, and the conductive fine particles may be deposited thereon. In addition, a heat-resistant agent, weathering agent, inorganic particles, water-soluble resin, emulsion, etc. may be added to the layer made of the metal oxide of the present invention for matting and improving the film quality within the range not inhibiting the effect of the present invention. good. The binder for dispersing the conductive fine particles is not particularly limited as long as it has a film-forming ability. For example, proteins such as gelatin and casein, carboxymethyl cellulose, hydroxyethyl cellulose, acetyl cellulose, diacetyl cellulose, and triacetyl cellulose. Cellulose compounds such as dextran, agar, sodium alginate, starch derivatives, etc., polyvinyl alcohol, polyvinyl acetate, polyacrylic acid ester, polymethacrylic acid ester, polystyrene, polyacrylamide, poly-N-vinylpyrrolidone, polyester, poly Examples thereof include synthetic polymers such as vinyl chloride and polyacrylic acid.

Further, an ionic polymer compound may be used as the conductive substance. Examples thereof include anionic polymer compounds such as those described in JP-B-49-23828 and JP-A-49-23827; JP-B 55-734, JP-A 50-54672, JP-B 59-14735, and the like. Ionene type polymer having a dissociation group in the main chain as seen; having a cationic dissociation group in the side chain as seen in JP-B-53-13223, 57-15376, and 61-27853 A cationic pendant polymer; and the like. The ionic polymer compound may be used alone or in combination of several kinds of ionic conductive substances. And is preferably such ionic polymer compounds are used in a range of 0.005g~2.0g / ^{m 2,} preferably used in particular in the range of 0.01g~1.0g / ^{m 2} .
The electrical resistance of these conductive layers is preferably 10 ¹² Ω (25 ° C., 10% RH) or less, more preferably 10 ¹⁰ Ω or less, and particularly preferably 10 ⁹ Ω or less.

  The film of the present invention is preferably provided with a hydrophilic binder layer as an adhesion layer. For example, a -COOM group-containing vinyl acetate-maleic acid copolymer compound, a hydrophilic cellulose derivative (for example, methyl cellulose, carboxymethyl cellulose, hydroxyalkyl cellulose, etc.), a polyvinyl alcohol derivative (for example, vinyl acetate-vinyl alcohol copolymer, polyvinyl Acetal, polyvinyl formal, polyvinyl benzal, etc.) natural polymer compounds (for example, gelatin, casein gum arabic, etc.) and hydrophilic group-containing polyester derivatives (for example, sulfone group-containing polyester copolymers).

The cellulose acylate film of the present invention thus obtained can be used for the following uses.
(1) Optical Compensation Sheet for Liquid Crystal Display Device The cellulose acylate film of the present invention is particularly effective when used as an optical compensation sheet for liquid crystal display devices. In the cellulose acylate film of the present invention, the film itself can be used as an optical compensation sheet. When the film itself is used as the optical compensation sheet, the transmission axis of the polarizing element (described later) and the slow axis of the optical compensation sheet made of cellulose acylate film are arranged so as to be substantially parallel or perpendicular. It is preferable. Such an arrangement of the polarizing element and the optical compensation sheet is described in JP-A-10-48420. The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing element. An optical compensation sheet is arranged.
The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 80 to 500 μm.
The optical compensation sheet is a birefringent film for removing the color of the liquid crystal screen. The cellulose acylate film itself of the present invention can be used as an optical compensation sheet. In addition, in order to improve the viewing angle of the liquid crystal display device, the cellulose acylate film of the present invention may be used as an optical compensation sheet by superimposing a film showing birefringence (positive / negative relationship) opposite thereto. . The range of the thickness of the optical compensation sheet is the same as the preferable thickness of the above-described film of the present invention.
Examples of the polarizing film of the polarizing element include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. Any polarizing film is generally produced using a polyvinyl alcohol film. The protective film of the polarizing plate preferably has a thickness of 25 to 350 μm, and more preferably 50 to 200 μm. The liquid crystal display device may be provided with a surface treatment film. The functions of the surface treatment film include hard coat, anti-fogging treatment, anti-glare treatment and antireflection treatment.
As described above, there has also been proposed an optical compensation sheet in which an optically anisotropic layer containing a liquid crystal (particularly a discotic liquid crystalline molecule) is provided on a support (Japanese Patent Application Laid-Open Nos. 3-9325 and 6-148429). Nos. 8-50206 and 9-26572). The cellulose acylate film of the present invention can also be used as a support for such an optical compensation sheet.

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

(3) VA liquid crystal display device The cellulose acylate film of the present invention is particularly advantageously used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell. In the optical compensation sheet used for the VA liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the VA liquid crystal display device are determined by the optical properties of the optically anisotropic layer, the optical properties of the support, and the arrangement of the optically anisotropic layer and the support. . When two optical compensation sheets are used in the VA liquid crystal display device, the in-plane retardation of the optical compensation sheet is preferably in the range of −5 nm to 5 nm. Therefore, the absolute value of the in-plane retardation of each of the two optical compensation sheets is preferably 0 to 5. When one optical compensation sheet is used in the VA liquid crystal display device, it is preferable that the in-plane retardation of the optical compensation sheet be in the range of −10 nm to 10 nm.

(4) OCB type liquid crystal display device and HAN type liquid crystal display device The cellulose acylate film of the present invention is an optical component of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or an HAN type liquid crystal display device having a HAN mode liquid crystal cell. It is also advantageously used as a support for a compensation sheet. In the optical compensation sheet used for the OCB type liquid crystal display device or the HAN type liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the OCB type liquid crystal display device or the HAN type liquid crystal display device are also the optical properties of the optical anisotropic layer, the optical properties of the support, and the optical anisotropic layer and the support. Is determined by the arrangement of

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

The measurement method used in the present invention will be described below.
(1) Radius of inertia, second virial coefficient, weight average molecular weight determined by light scattering method Measured by static light scattering method according to the following method. Note that these measurements are made in a dilute region for the convenience of the apparatus, but these measured values reflect the behavior of the dope in the high concentration region.
(1-1) Cellulose acylate is dissolved in a solvent used for the dope to prepare solutions of 0.1 wt%, 0.2 wt%, 0.3 wt%, and 0.4 wt%. In order to prevent moisture absorption, the cellulose acylate is dried at 120 ° C. for 2 hours and measured at 25 ° C. and 10% rh.
(1-2) The solution and the solvent are filtered through a 0.2 μm Teflon (registered trademark) filter.
(1-3) These static light scatterings are measured at intervals of 10 degrees from 30 degrees to 140 degrees at 25 ° C. using a light scattering measuring apparatus (DLS-700 manufactured by Otsuka Electronics Co., Ltd.).
(1-4) These data are obtained by the BERRY plot method using the attached data analysis software. In addition, the refractive index required for this analysis uses the value of the solvent calculated | required with the Abbe refractive system, and the refractive index gradient (dn / dc) uses the differential refractometer (Otsuka Electronics Co., Ltd. product DRM-1021). Measure using the solvent and solution used for light scattering measurement.

(2) Heat of dissolution Measured using a calorimeter (Multipurpose Calorimeter MPC-116 manufactured by Tokyo Riko Co., Ltd.) according to the following method. Note that these measurements are made in a dilute region for the convenience of the apparatus, but these measured values reflect the behavior of the dope in the high concentration region.
(2-1) Weigh cellulose acylate in 250 mg glass ampoules. In order to prevent moisture absorption, the cellulose acylate is dried at 120 ° C. for 2 hours and measured at 25 ° C. and 10% RH.
(2-2) Add 60 ml of the solvent used for the dope into the sample cell of the calorimeter, and set the ampoule on this. Place only solvent in the reference cell.
(2-3) Wait for the calorimeter to stabilize at 27 ° C. while slowly stirring with the stirring bar attached to the cell. After this, break the ampoule with the attached jig and measure the amount of heat generated.
(2-4) The calorific value is calibrated by using the relationship between the calorific value when the electric resistance (100Ω) attached to the cell is energized at 2 V for 15 minutes and the area of the exothermic peak that appears.

(3) Reduced viscosity Measured using an Ostwald viscometer according to the following method. Note that these measurements are made in a dilute region for the convenience of the apparatus, but these measured values reflect the behavior of the dope in the high concentration region.
(3-1) Cellulose acylate is dissolved in a solvent used for the dope to prepare 0.1 wt%, 0.2 wt%, 0.3 wt%, and 0.4 wt% solutions. In order to prevent moisture absorption, the cellulose acylate is dried at 120 ° C. for 2 hours and measured at 25 ° C. and 10% rh.
(3-2) The solution and the solvent are filtered through a 5 μm Teflon (registered trademark) filter.
(3-3) Select a viscosity tube with a solvent falling time of 100 seconds ± 20 seconds at 25 ° C.
(3-4) Using this, the falling time t (0) of the solvent and the falling time t (x) of each concentration (X%) are measured. From these, the relative viscosity ηsp = {t (x) −t (0)} / t (0) is obtained.
(3-5) The concentration (X) is plotted on the horizontal axis, ηsp is plotted on the vertical axis, and extrapolated toward X = 0, and the intercept with the vertical axis ηsp is taken as the reduced viscosity [η].

(4) Degree of substitution of acetyl group and other acyl groups of cellulose acylate Measured by saponification method according to ASTM D817-91.
(4-1) The dried cellulose acylate is precisely weighed and dissolved in a mixed solvent of acetone and dimethyl sulfoxide (DMSO) (volume ratio 4: 1), and then a predetermined 1N-sodium hydroxide aqueous solution is added thereto at 25 ° C. Saponify for 2 hours. Phenolphthalein was added as an indicator, and excess sodium hydroxide was titrated with 1N-sulfuric acid (concentration factor: F). Moreover, the blank test was done by the method similar to the above, and substitution degree was calculated | required according to the following formula.
T [A + B] = (EM) × F / (1000 × W)
A = {162.14 × T [A + B]} / {1-42.14 × T [A + B] + (1−56.06 × T [A + B]) × (Ca / Cb)}
B = A × (Ca / Cb)
here,
T [A + B]: Total organic acid amount (mol / g)
E: Blank test titration (ml)
M: Sample titration (ml)
F: Factor of 1N-sulfuric acid W: Sample weight (g)
Ca: Amount of acetic acid (mol) measured by ion chromatography
Cb: amount of organic acid having 3 to 5 carbon atoms (moles) measured by ion chromatography
A: Degree of substitution of acetyl group B: Degree of substitution of organic acid having 3 to 5 carbon atoms

[Example 1]
(Invention 1 to Invention 11, Comparative Example 1)
(1) Preparation of cellulose acylate solution (dope) Cellulose acylate described in Table 1 (acetyl group substitution rate A and C 3-5 acyl group (in Table 1, “C 3-5 acyl group”) ), The substitution rate B, and the viscosity average polymerization degree (DP)) were washed to remove iron. The washing was carried out in an acetone / water mixed system. The conditions at this time (the ratio of acetone in the total volume of liquid and the number of washings) are shown in Table 1. Then, it dried in air | atmosphere at the temperature and time of Table 1, and dehumidified.
The amount of iron was measured using an atomic absorption method after preparing cellulose acylate to 0.1 wt% of dichloromethane.
DP was measured by the following method.
About 0.2 g of completely dried cellulose triacetate was precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride: ethanol = 9: 1 (weight ratio). This was measured with an Ostwald viscometer for the number of seconds dropped at 25 ° C., and the degree of polymerization was determined by the following equation.
ηrel = T / T0
T: Number of seconds dropped for measurement sample T0: Number of seconds dropped for solvent alone [η] = (1nηrel) / C
C: Concentration (g / l)
DP = [η] / Km
Km: 6 × 10 ⁻⁴

  These were dissolved by the method selected from the following as shown in Table 1, but all the present invention was in a dry nitrogen atmosphere (relative humidity 0% rh), and all the comparative examples were in a general environment atmosphere (relative humidity 50% rh). I went there. Silica particles (particle size: 20 nm) were 0.5% by mass of cellulose acylate, triphenyl phosphate / biphenyl phosphate mixture (mixing ratio = 1/2) was 10% by mass of cellulose acylate, and 2,4 -Bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine was added in an amount of 1.0% by mass of cellulose acylate.

(1-1) Room temperature dissolution method (described as “normal temperature” in Table 1)
The cellulose acylate described in Table 1 was gradually added to the solvent while stirring well, and allowed to swell for 3 hours at room temperature (25 ° C.). The resulting swollen mixture was dissolved in a mixing tank with a reflux condenser at 50 ° C. with stirring. All these operations were performed in a nitrogen atmosphere.

(1-2) Cooling dissolution method (described as “cooling” in Table 1)
The cellulose acylate described in Table 1 was gradually added to the solvent while stirring well, and allowed to swell for 3 hours at room temperature (25 ° C.). The obtained swollen mixture was slowly stirred at −8 ° C./min to −30 ° C., then cooled to the temperature shown in Table 1, and after 6 hours, the temperature was raised at + 8 ° C./min and the content sol At the stage where the conversion to a certain degree progressed, stirring of the contents was started. The dope was obtained by heating to 50 ° C. All these operations were performed in a nitrogen atmosphere.

(1-3) High-pressure and high-temperature dissolution (described as “high temperature” in Table 1)
The cellulose acylate described in Table 1 was gradually added to the solvent while stirring well, and allowed to swell for 3 hours at room temperature (25 ° C.). The obtained swollen mixture was placed in a double-structured stainless steel sealed container. High-pressure steam was passed through the jacket on the outside of the container, and the mixture was heated at + 8 ° C./min and held at the temperature shown in Table 1 for 5 minutes under 1 Mpa. Thereafter, 50 ° C. water was passed through the outer jacket and cooled to −50 ° C./min to 50 ° C. to obtain a dope. All these operations were performed in a nitrogen atmosphere.

  The inertial radius of these dopes, the second virial coefficient, the heat of dissolution, the reduced viscosity, and the weight average molecular weight determined by the light scattering method were measured by the above methods and are shown in Table 1.

(2) Film formation of cellulose acylate film The solution (dope) obtained by the above method is fed into a filter medium (filter paper (manufactured by Azumi Filter Paper Co., Ltd., No. 244) and Nell filter cloth) using a gear pump. The time fluctuation of the pressure gauge installed on the upstream side of the filter medium was determined to determine the increase in filtration pressure. That is, the pressure at the start was P (0), the pressure after the 20t dope was filtered was P, and the filtration pressure was increased = P / P (0). The evaluation results are shown in Table 1. The allowable range is 3 or less.
The dope after filtration is sent to a casting die by a quantitative gear pump, and this is cast using a band casting machine having an effective length of 6 m so that the dry film thickness becomes 100 μm. The band temperature was 0 ° C. It is exposed to wind for 2 seconds for drying, and when the volatile content in the film reaches 50% by weight, the film is peeled off from the band. At this time, the flow extension in which the tailing due to the slack generated in the casting die portion started to occur is shown in Table 1 as “tailing failure start length”. The allowable range is 15 km or more.
This was followed by 3 minutes at 100 ° C., 5 minutes at 130 ° C., and 5 minutes at 160 ° C., without shrinking the film, allowing it to shrink freely and drying stepwise to evaporate the remaining solvent.
Thereafter, trimming was performed at 15 cm at both ends, and knurling (thickening processing) with a height of 50 μm and a width of 1 cm was performed at both ends to obtain a cellulose acylate film with a width of 1.5 m.
All of the films of the present invention exhibited good retardation of 10 nm or less. Further, these films were stretched by 10% to 30% MD, TD at 130 ° C. online during the drying step during the film forming step or thereafter offline. These were able to increase the retardation from 40 nm to 160 nm in proportion to the draw ratio.
Haze was also measured, and the cellulose acylate film of the present invention was 0.5% or less.
Further, the dope of the present invention 1 was laminated on the band side and the present invention 2 on the air side in accordance with the co-casting method described in JP-A-06-134993, and good results were obtained in the same manner.
The cellulose acylate film thus obtained was used as a liquid crystal display device described in Example 1 of JP-A-10-48420, and an optically anisotropic layer containing discotic liquid crystal molecules described in Example 1 of JP-A-9-26572. , An alignment film coated with polyvinyl alcohol, a VA liquid crystal display device described in FIGS. 2 to 9 of JP 2000-154261 A, and an OCB liquid crystal display device described in FIGS. 10 to 15 of JP 2000-154261 A Good performance was obtained.

[Example 2]
(Invention 12-16)
(1) Preparation of cellulose acetate solution (dope) (Invention 12)
After crushing wood pulp having an α-cellulose content of about 97% by mass, 100 parts by mass of glacial acetic acid was uniformly sprayed on 100 parts by mass of the pulp, followed by stirring and mixing at room temperature for 90 minutes. The pulp was put into a pre-cooled mixed solution of 245 parts by mass of acetic anhydride, 365 parts by mass of acetic acid and 7.5 parts by mass of sulfuric acid, and the mixture was stirred and mixed to proceed the acetylation reaction at 45 ° C or lower. The reaction system was non-uniform in the initial stage, but changed from an opaque bottle shape to a pale yellow transparent water tank shape as the reaction progressed. When no non-acetylated fiber pieces were found in the syrup-like reaction mixture, the reaction was terminated. It took about 300 minutes from the start of the reaction to the end of the reaction. At the end of the acetylation reaction, 24.7 parts by mass of magnesium acetate aqueous solution (30% by mass) is added to hydrolyze excess acetic anhydride and neutralize part of the sulfuric acid, thereby stopping the acetylation reaction did.
Next, 6.4 parts by mass of magnesium acetate aqueous solution (30% by mass) was added while raising the temperature of the reaction solution to about 60 ° C. in 30 minutes. Thereafter, water was added so that the bath concentration in the system was about 85% by mass, and the temperature was further raised to stabilize at 70 ° C. The aging reaction was continued at 70 ° C. for 30 minutes. At the end of the reaction, 25 parts by mass of magnesium acetate aqueous solution (30% by mass) was added to completely neutralize the sulfuric acid. In this way, the acetyl substitution rate at the 6-position was adjusted. The reaction-terminated solution was charged with a large amount of 10% by mass aqueous acetic acid with vigorous stirring to precipitate and separate cellulose acetate. The precipitated cellulose acetate was collected by filtration and washed with water until it was substantially free of acetic acid. Thereafter, dehydration and drying were performed to obtain powdered cellulose acetate (Invention 12).

(Invention 13)
After crushing wood pulp having an α-cellulose content of about 97% by mass, 100 parts by mass of glacial acetic acid was uniformly sprayed on 100 parts by mass of the pulp, followed by stirring and mixing at room temperature for 90 minutes. The pulp was put into a pre-cooled mixed solution of 245 parts by mass of acetic anhydride, 365 parts by mass of acetic acid and 6.5 parts by mass of sulfuric acid, stirred and mixed, and the acetylation reaction was allowed to proceed at 45 ° C. or lower. The reaction system was non-uniform in the initial stage, but changed from an opaque bottle shape to a pale yellow transparent water tank shape as the reaction progressed. When no non-acetylated fiber pieces were found in the syrup-like reaction mixture, the reaction was terminated. It took about 330 minutes from the start of the reaction to the end of the reaction. At the end of the acetylation reaction, 24.7 parts by mass of magnesium acetate aqueous solution (30% by mass) is added to hydrolyze excess acetic anhydride and neutralize part of the sulfuric acid, thereby stopping the acetylation reaction did.
Next, 6.4 parts by mass of magnesium acetate aqueous solution (30% by mass) was added while raising the temperature of the reaction solution to about 60 ° C. in 30 minutes. Thereafter, water was added so that the bath concentration in the system was about 85% by mass, and the temperature was further raised to stabilize at 70 ° C. The aging reaction was continued at 70 ° C. for 30 minutes. At the end of the reaction, 24 parts by mass of magnesium acetate aqueous solution (30% by mass) was added to completely neutralize the sulfuric acid. In this way, the acetyl substitution rate at the 6-position was adjusted. The reaction-terminated solution was charged with a large amount of 10% by mass aqueous acetic acid with vigorous stirring to precipitate and separate cellulose acetate. The precipitated cellulose acetate was collected by filtration and washed with water until it was substantially free of acetic acid. Thereafter, dehydration and drying were performed to obtain powdered cellulose acetate (Invention 13).

(Invention 14)
After crushing wood pulp having an α-cellulose content of about 97% by mass, 100 parts by mass of glacial acetic acid was uniformly sprayed on 100 parts by mass of the pulp, followed by stirring and mixing at room temperature for 90 minutes. The pulp was put into a pre-cooled mixed solution of 245 parts by mass of acetic anhydride, 365 parts by mass of acetic acid and 5.5 parts by mass of sulfuric acid, and the mixture was stirred and mixed to proceed the acetylation reaction at 45 ° C or lower. The reaction system was non-uniform in the initial stage, but changed from an opaque bottle shape to a pale yellow transparent water tank shape as the reaction progressed. When no non-acetylated fiber pieces were found in the syrup-like reaction mixture, the reaction was terminated. It took about 360 minutes from the start of the reaction to the end of the reaction. At the end of the acetylation reaction, 24.7 parts by mass of magnesium acetate aqueous solution (30% by mass) is added to hydrolyze excess acetic anhydride and neutralize part of the sulfuric acid, thereby stopping the acetylation reaction did.
Next, 6.4 parts by mass of magnesium acetate aqueous solution (30% by mass) was added while raising the temperature of the reaction solution to about 60 ° C. in 30 minutes. Thereafter, water was added so that the bath concentration in the system was about 85% by mass, and the temperature was further raised to stabilize at 70 ° C. The aging reaction was continued at 70 ° C. for 30 minutes. At the end of the reaction, 23 parts by mass of magnesium acetate aqueous solution (30% by mass) was added to completely neutralize the sulfuric acid. In this way, the acetyl substitution rate at the 6-position was adjusted. The reaction-terminated solution was charged with a large amount of 10% by mass aqueous acetic acid with vigorous stirring to precipitate and separate cellulose acetate. The precipitated cellulose acetate was collected by filtration and washed with water until it was substantially free of acetic acid. Thereafter, it was dehydrated and dried to obtain cellulose acetate (Invention 14).

(Invention 15)
After crushing wood pulp having an α-cellulose content of about 97% by mass, 100 parts by mass of glacial acetic acid was uniformly sprayed on 100 parts by mass of the pulp, followed by stirring and mixing at room temperature for 90 minutes. The pulp was put into a pre-cooled mixed solution of 245 parts by mass of acetic anhydride, 365 parts by mass of acetic acid and 4.5 parts by mass of sulfuric acid, and the mixture was stirred and mixed to proceed the acetylation reaction at 45 ° C or lower. The reaction system was non-uniform in the initial stage, but changed from an opaque bottle shape to a pale yellow transparent water tank shape as the reaction progressed. When no non-acetylated fiber pieces were found in the syrup-like reaction mixture, the reaction was terminated. It took about 420 minutes from the start of the reaction to the end of the reaction. At the end of the acetylation reaction, 24.7 parts by mass of magnesium acetate aqueous solution (30% by mass) is added to hydrolyze excess acetic anhydride and neutralize part of the sulfuric acid, thereby stopping the acetylation reaction did.
Next, 6.4 parts by mass of magnesium acetate aqueous solution (30% by mass) was added while raising the temperature of the reaction solution to about 60 ° C. in 30 minutes. Thereafter, water was added so that the bath concentration in the system was about 85% by mass, and the temperature was further raised to stabilize at 70 ° C. The aging reaction was continued at 70 ° C. for 30 minutes. At the end of the reaction, 22 parts by mass of magnesium acetate aqueous solution (30% by mass) was added to completely neutralize the sulfuric acid. In this way, the acetyl substitution rate at the 6-position was adjusted. The reaction-terminated solution was charged with a large amount of 10% by mass aqueous acetic acid with vigorous stirring to precipitate and separate cellulose acetate. The precipitated cellulose acetate was collected by filtration and washed with water until it was substantially free of acetic acid. Thereafter, dehydration and drying were performed to obtain cellulose acetate (Invention 15).

(Invention 16)
After crushing wood pulp having an α-cellulose content of about 97% by mass, 100 parts by mass of glacial acetic acid was uniformly sprayed on 100 parts by mass of the pulp, followed by stirring and mixing at room temperature for 90 minutes. The pulp was put into a pre-cooled mixed solution of 245 parts by mass of acetic anhydride, 365 parts by mass of acetic acid and 12.0 parts by mass of sulfuric acid, and the mixture was stirred and mixed to proceed the acetylation reaction at 45 ° C or lower. The reaction system was non-uniform in the initial stage, but changed from an opaque bottle shape to a pale yellow transparent water tank shape as the reaction progressed. When no non-acetylated fiber pieces were found in the syrup-like reaction mixture, the reaction was terminated. It took about 200 minutes from the start of the reaction to the end of the reaction. At the end of the acetylation reaction, 24.7 parts by mass of magnesium acetate aqueous solution (30% by mass) is added to hydrolyze excess acetic anhydride and neutralize part of the sulfuric acid, thereby stopping the acetylation reaction did.
Next, 6.4 parts by mass of magnesium acetate aqueous solution (30% by mass) was added while raising the temperature of the reaction solution to about 60 ° C. in 30 minutes. Thereafter, water was added so that the bath concentration in the system was about 85% by mass, and the temperature was further raised to stabilize at 70 ° C. The aging reaction was continued at 70 ° C. for 30 minutes. At the end of the reaction, 28 parts by mass of magnesium acetate aqueous solution (30% by mass) was added to completely neutralize the sulfuric acid. In this way, the acetyl substitution rate at the 6-position was adjusted. The reaction-terminated solution was charged with a large amount of 10% by mass aqueous acetic acid with vigorous stirring to precipitate and separate cellulose acetate. The precipitated cellulose acetate was collected by filtration and washed with water until it was substantially free of acetic acid. Thereafter, it was dehydrated and dried to obtain cellulose acetate (Invention 16).

Table 2 shows the substitution degree, viscosity average polymerization degree, and 6-position substitution rate of cellulose acetates obtained in the present inventions 12 to 16. In any cellulose acetate, the acetone extract was 11% by mass, and the ratio of the weight average molecular weight to the number average molecular weight was 0.5.
These cellulose acetates were processed into flakes. The average particle diameter of the flakes was 1.5 mm, and the standard deviation was 0.5 mm. These were washed in an acetone / water mixed system in the same manner as in Invention 1 in Table 1 to remove iron, and then dried in the air under the same conditions (temperature, time) as in Invention 1 in Table 1 to remove moisture. did. When the amount of iron was measured according to Example 1, all were 10 ppm. When the water content was also measured according to Example 1, all levels were 0.10%.

  Using each of the obtained cellulose acetates (flakes), a cellulose acetate solution (dope) was prepared in the same manner as in the present invention 1 except that the following composition was used. Table 2 shows the results of measurement of the inertial radius of these dopes, the second virial coefficient, the heat of dissolution, the reduced viscosity, and the weight average molecular weight determined by the light scattering method.

────────────────────────────────────────
Cellulose acetate solution composition ────────────────────────────────────────
Cellulose acetate 20 parts by weight Methyl acetate 58 parts by weight Acetone 5 parts by weight Methanol 5 parts by weight Ethanol 5 parts by weight Butanol 5 parts by weight Triphenyl phosphate (plasticizer) 1.2 parts by weight Ditrimethylolpropane tetraacetate (plasticizer) 1.2 Part by mass 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine (UV absorber) 0.2 part by mass 2 -(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole (UV absorber) 0.2 parts by mass 2- (2'-hydroxy-3', 5'- Di-tert-amylphenyl) -5-chlorobenzotriazole (UV absorber) 0.2 parts by mass C ₁₂ H ₂₅ OCH ₂ CH ₂ O—P (═O) — (OK) ₂ (Peeling agent) 0.02 parts by mass Citric acid (peeling agent) 0.02 parts by mass Silica (particle size 20 nm, Mohs hardness 7) 0.05 parts by mass ─────────────── ─────────────────────────

(2) Film Formation of Cellulose Acetate Film The obtained solution (dope) was filtered, and the evaluation results of increase in filtration pressure are shown in Table 2. The dope after filtration is sent to a casting die by a quantitative gear pump, and this is cast using a band casting machine having an effective length of 6 m so that the dry film thickness becomes 100 μm. The band temperature was 0 ° C. It is exposed to wind for 2 seconds for drying, and when the volatile content in the film reaches 50% by mass, the film is peeled off from the band. Table 2 shows the results of measuring the time until no peeling residue occurs. As the 6-position substitution degree of cellulose acetate increases, this time can be shortened and the casting speed can be increased.
Further, the flow extension in which the tailing due to the slack generated in the casting die portion has started to be generated is shown in Table 2 as the “tailing failure start length”.
This was followed by 3 minutes at 100 ° C., 5 minutes at 130 ° C., and 5 minutes at 160 ° C., without shrinking the film, allowing it to shrink freely and drying stepwise to evaporate the remaining solvent. Next, both ends of the film were trimmed by 15 cm, and knurling (thickening processing) with a height of 50 μm and a width of 1 cm was performed at both ends to obtain a cellulose acylate (cellulose acetate) film with a width of 1.5 m.

All of the films of the present invention exhibited good retardation of 10 nm or less. Further, these films were stretched by 10% to 30% MD, TD at 130 ° C. online in the drying process of the film forming process or offline thereafter. In proportion to the draw ratio, the retardation of the film could be increased in the range of 40 nm to 160 nm. Haze was also measured, and the cellulose acylate film of the present invention was 0.5% or less.
Further, according to the co-casting method, films prepared by laminating the dope prepared according to the present invention 12 on the band side and the present invention 13 on the air side were produced, and good results were similarly obtained. The co-casting method is described in Japanese Patent Application Laid-Open No. 06-134993.
Furthermore, cellulose triacetates having an acetyl substitution degree of 2.75, 2.77, and 2.85 were prepared by changing the 6-position substitution rate in the same manner as in the present inventions 12 to 16, but similar results were obtained for these. It was.
In the same manner as in the present inventions 2 and 3 in Example 1, cellulose propionate and cellulose butyrate having 6-position substitution rates of 32, 34 and 36% were prepared, respectively, and the film was formed in the same manner as in the present invention 12. As a result of evaluation, good results were obtained as well.
The cellulose acylate film thus obtained contains the liquid crystal display device described in Example 1 of JP-A-10-48420 and the discotic liquid crystal molecules described in Example 1 of JP-A-9-26572. An optically anisotropic layer, an alignment film coated with polyvinyl alcohol, a VA liquid crystal display device described in FIGS. 2 to 9 of JP-A-2000-154261, and FIGS. 10 to 15 of JP-A-2000-154261 When used in the OCB type liquid crystal display device, good performance was obtained.

  A cellulose acylate film excellent in long-term continuous film-forming property was provided by a method for producing a cellulose acylate film characterized by dissolving so that the inertial square radius is 40 nm or more and 200 nm or less.

Claims (11)

Washing cellulose acylate with an acetone / water mixed solvent having a mixing weight ratio of 0.2 / 0.8 to 0.8 / 0.2, thereby adjusting the iron content to 0 ppm to 50 ppm; Is obtained by dissolving cellulose acylate having a water content of 0% or more and 50ppm or less and a water content of 0% or more and 0.5% or less in an organic solvent, so that the cellulose acylate is dissolved so that the radius of inertia is 40 nm or more and 200 nm or less. A method for producing a cellulose acylate film, comprising : a step of preparing an acylate solution ; and a step of forming a film of the cellulose acylate solution. The manufacturing method of Claim 1 which adjusts the iron content of a cellulose acylate to 0 ppm or more and 20 ppm or less. The manufacturing method according to claim 1, wherein the cellulose acylate has a viscosity average polymerization degree of 250 to 550 . The manufacturing method of Claim 1 which wash | cleans a cellulose acylate by stirring for 30 minutes or more and 3 hours or less at the temperature of 30 degreeC or more and 70 degrees C or less in acetone / water mixed solvent.   The manufacturing method of Claim 4 which wash | cleans a cellulose acylate by stirring for 50 minutes or more and 2 hours or less at the temperature of 40 to 60 degreeC in acetone / water mixed solvent. The production method according to claim 1 , wherein the washing is performed 2 times or more and 5 times or less.   The production method according to claim 1, wherein the water content of the cellulose acylate is 0% or more and 0.2% or less. The production method according to claim 1 , wherein the cellulose acylate is washed and then dried at 80 ° C to 200 ° C for 10 minutes to 10 hours.   The manufacturing method according to claim 8, wherein the cellulose acylate is washed and then dried at 110 ° C to 160 ° C for 30 minutes to 5 hours.   The production method according to claim 1, wherein the organic solvent is selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms. The manufacturing method of Claim 1 which performs the process of melt | dissolving a cellulose acylate in the organic solvent in dry air or dry nitrogen .