JP2002086469A - Method for producing cellulose acylate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a cellulose acylate film, in which aging stability of liquid after dissolution is improved and optical characteristics, mechanical strength and dimensional stability are excellent. SOLUTION: In the method for producing the cellulose acylate film, in which cellulose acylate is dissolved in a solvent substantially constituted of an unchlorinated solvent and thereafter film making is performed, such a solvent is used as the solvent that dipole moment is in a range of 0.2-3.3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a cellulose acetate film.

[0002]

2. Description of the Related Art 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 prepared by solvent casting (solution casting).
It is manufactured by the 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. Conventionally, a chlorine-based solvent containing 70% by weight or more of dichloromethane has been used. However, replacement of these chlorinated solvents with other non-chlorinated solvents has been studied from the viewpoint of environmental protection, and measures have been urgently needed.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a cellulose acylate film having improved stability over time after dissolution and excellent mechanical properties and optical properties of a film.

[0004]

According to the present invention, by implementing the following methods (1) to (9), the following films (10) and (11) solving the above problems can be manufactured. (1) A method for producing a cellulose acylate film in which a cellulose acylate is dissolved in a solvent substantially composed of a non-chlorinated solvent and then formed into a film, wherein the dipole moment of the solvent is 0.2 to 3. 2. A method for producing a cellulose acylate film, which is in the range of 2.

(2) The method for producing a cellulose acylate film according to (1), wherein the mixed solvent comprises 60 to 98% by mass of a main solvent and 40 to 2% by mass of an alcohol. (3) The main solvent is a solvent consisting essentially of a single or plural mixed solvents having 3 to 12 carbon atoms and having at least one oxygen-containing functional group in the molecule.
3. The method for producing a cellulose acylate film according to item 1.

(4) The method for producing a cellulose acylate film according to (3), wherein the oxygen-containing group is a functional group selected from an ether group, a carbonyl group, and an ester group. (5) The method for producing a cellulose acylate film according to (2), wherein the main solvent and the alcohol have a boiling point of 250 ° C. or lower.

(6) The method for producing a cellulose acylate film according to (1), wherein the cellulose acylate is substituted with a hydroxyl group of cellulose so as to satisfy all of the formulas (I) to (IV): 2.6 ≦ A + B ≦ 3.0 (II) 2.0 ≦ A ≦ 3.0 (III) 0 ≦ B ≦ 0.8 (IV) 1.9 <AB (where A and B are And A is a substituent of an acyl group substituted by a hydroxyl group of cellulose, A is a degree of substitution of an acetyl group, and B is a degree of substitution of an acyl group having 3 to 5 carbon atoms.

(7) The method for producing a cellulose acylate film according to (1), wherein the cellulose acylate is cellulose acetate. (8) The method for producing a cellulose acylate film according to (1), wherein the dissolution of the cellulose acylate includes a step of cooling the mixture to a temperature of −80 ° C. or more and 0 ° C. or less. (9) The dissolution of the cellulose acylate is 40 ° C. or more 2
The method for producing a cellulose acylate film according to (1), comprising a step of heating the film to 00 ° C. or lower.

(10) A cellulose acylate film formed by the method according to any one of (1) to (9). (11) The cellulose acylate film according to (10), further comprising silica particles, a plasticizer, and an ultraviolet absorber. Loin acylate film.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Cellulose as a cellulose acylate raw material used in the present invention includes cotton linter and wood pulp. Cellulose acylate obtained from any of the raw material celluloses can be used, or mixed and used. May be. In the cellulose acylate of the present invention obtained from these celluloses, the degree of substitution of the cellulose with hydroxyl groups satisfies all of the following formulas (I) to (IV). (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 substituents of an acyl group substituted by a hydroxyl group of cellulose, A represents the degree of substitution of an acetyl group, and B represents the substitution degree of an acyl group having 3 to 5 carbon atoms. Degrees. Cellulose contains 3 per glucose unit
And the above-mentioned number represents the degree of substitution for the hydroxyl group 3.0, with the maximum degree of substitution being 3.0. The degree of substitution is obtained by measuring the degree of binding between acetic acid and a fatty acid having 3 to 5 carbon atoms that substitute for the hydroxyl group of cellulose, and calculating the degree of substitution. ASTM's D-
817-91. Those with B = 0 are called triacetylcellulose (TAC),
On the other hand, those having B> 0 are also called cellulose mixed fatty acid esters. More preferably, it is TAC. TAC satisfies the formulas (V) and (VI). (V) 2.6 ≦ A ≦ 3.0 (VI) 0 = B

The mixed fatty acid ester of cellulose contains an acyl group having 3 to 5 carbon atoms in addition to an acetyl group, and is preferably a propionyl group (C ₂ H ₅ CO 2).
-), butyryl _{(C 3 H 7 CO -)} (n-, iso
-), valeryl _{(C 4 H 9 CO -)} (n-, iso
-, Sec- and tert-) are preferable, and an n-propionyl group is particularly preferable. When the acylating agent for these acyl groups is an acid anhydride or an 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 industrial method is to convert cellulose into fatty acids (acetic acid, propionic acid, butyric acid, valeric acid) or their anhydrides (acetic anhydride, propionic anhydride, butyric anhydride) corresponding to acetyl and other acyl groups. , Valeric anhydride) to synthesize cellulose acylate. A specific production method can be synthesized by, for example, a method described in JP-A-10-45804. The polymerization degree (average viscosity) of the cellulose acylate of the invention is 200 to 700.
Is more preferably 250 to 550, and still more preferably 250 to 350. Thereby, mechanical strength can be satisfied. The viscosity average degree of polymerization can be measured by an Ostwald viscometer, and is determined from the measured intrinsic viscosity [η] of cellulose acylate by the following equation. DP = [η] / Km (where DP is the viscosity average polymerization degree,
Km is a constant of 6 × 10 ^-4 )

In the present invention, a solution (dope) in which cellulose acylate having such a composition is dissolved in a mixed solvent of a main solvent substantially composed of a non-chlorinated solvent and an alcohol is used.
And cast it to form a film. Here, the substantially non-chlorine solvent means that the content of the solvent containing one or more chlorine atoms in the structural formula is 0 vol% to 40 vol%, more preferably 0 vol% to 15 vol%, and further preferably 0 vol%. %
It is. Examples of the solvent containing one or more chlorine atoms in the structural formula include halogenated hydrocarbons having 1 to 7 carbon atoms, and specific examples include dichloromethane, dichloroethane, and chlorobenzene. 60 vol% or more of solvent 10
0 vol% or less, more preferably 60 vol% or more and 98 vol%
The non-chlorine solvent, which is a main solvent occupying 60 vol% or more and 90 vol% or less, preferably comprises a solvent having 3 to 12 carbon atoms and has an ether group, a carbonyl group (ketone) and an ester group in the molecule. It is preferable to use at least one kind of solvent having at least one of the following. These ethers, ketones and esters may have a linear structure, a branched structure or a cyclic structure. ether,
Functional groups of ketones and esters (ie, -O-,-
A compound having two or more of any of CO— and —COO—) can also be used.

Next, the dipole moment of the solvent will be described. The dipole moment is a pair of positive and negative arms separated by a distance l,
= Ql. The distribution of the charge of the solvent greatly affects the solubility of the cellulose acylate molecule. By selecting a solvent having a dipole moment in the range of 0.2 to 3.3, the solvation of the cellulose acylate molecule can be improved. As a result of intensive studies by the present inventors, it has become clear that melting occurs and dissolution is possible, which has led to the present invention. Preferred solvents in the present invention are shown below together with their dipole moments. Examples of ethers having 3 to 12 carbon atoms include dibutyl ether (dipole moment 1.2
2D), dimethoxyethane (1.79D), 1,4-dioxane (0.23D), 1,3,5-trioxane (2.18D), tetrahydrofuran (1.71D),
Anisole (1.20D) and phenetole (1.0
0D). Examples of ketones having 3 to 12 carbon atoms include acetone (2.69D), methyl ethyl ketone (2.76D), diethyl ketone (2.70D),
Methyl pentyl ketone (2.59D), cyclopentanone (3.21D), cyclohexanone (3.01D) and acetophenone (2.96D). Examples of the esters having 3 to 12 carbon atoms include ethyl formate (1.77D), n-propyl formate (1.89D), n-pentyl formate (1.90D), and methyl acetate (1.61D).
D), ethyl acetate (1.88D) and n-pentyl acetate (1.91D). Examples of the organic solvent having two or more types of functional groups include ethyl 2-ethoxyacetate (2.25D) and 2-methoxyethanol (2.04D).
D) and 2-butoxyethanol (2.08D), ethyl acetoacetate (3.22D). These solvents may be used as a mixture.

As the solvent of the present invention, an alcohol is used in combination. The alcohol is preferably a monoalcohol having 1 to 8 carbon atoms or a dialcohol, more preferably methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol are mentioned. These may be added alone or as a mixture of two or more. These alcohols are 2 vol% or more and 40 vol% in all solvents.
Below, more preferably 3 vol% or more and 30 vol% or less, still more 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 / γ-butyrolactone / methanol / ethanol (= X / (70-X) / 5
/ 5/5, parts by weight) cellulose acylate / methyl acetate / dioxane / cyclopentanone / methanol / 1-butanol (= X /
(60-X) / 12/12/5/3, 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,
Here, X represents a part by weight of cellulose acylate, preferably 10 to 25, and particularly preferably 15 to 23.
It is.

The solvent of the present invention has 2 to 10 carbon atoms.
The following fluoroalcohols may be contained in an amount of 10% by weight or less of the total solvent amount. Specifically, 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,
3,3-tetrafluoro-1-propanol is mentioned. Further, 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.

When dissolving cellulose acylate in these solvents, the container may be filled with an inert gas such as nitrogen gas. The viscosity of the cellulose acylate solution immediately before film formation may be within a range that can be cast at the time of film formation.
It is preferable that the pressure be adjusted in the range of 0 ps · s to 2000 ps · s, and particularly 30 ps · s to 400 ps · s. This dissolution is carried out by adding the above-mentioned cellulose acylate while stirring the solvent in the tank at room temperature according to a usual method. To further shorten the dissolution time, it is also preferable to use one or both of the following cooling dissolution method and high temperature dissolution method.

In the cooling dissolution method, first, a temperature around room temperature (-1)
(0 to 40 ° C.), the cellulose acylate is gradually added to the organic solvent with stirring. When a plurality of solvents are used, the order of addition is not particularly limited. For example, after adding cellulose acylate to the main solvent, another solvent (eg, a gelling solvent such as alcohol) may be added, or conversely, after the gelling solvent is wetted in advance by the cellulose acylate. May be added, which is effective in preventing heterogeneous dissolution. It is preferable to adjust the amount of cellulose acylate so that the mixture contains 10 to 40% by weight. More preferably, the amount of cellulose acylate is 10 to 30% by weight. Further, an optional additive described below may be added to the mixture. next,
The mixture is -100 to -10C, more preferably -80 to
It is cooled to -10C, more preferably -50C to -20C, most preferably -50C to -30C. 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.
/ Sec or more is preferred. In addition, it is desirable to use a closed container in order to avoid water contamination due to dew condensation during cooling. When heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., and most preferably 0 to 50 ° C.) after cooling, a solution in which the cellulose acylate flows in the organic solvent is obtained. The temperature may be raised only by leaving it at room temperature or may be heated in a warm bath. Further, if the pressure is increased during cooling using a pressure-resistant container and the pressure is reduced during heating, the dissolution time can be shortened. To perform pressurization and decompression,
Is desirable. These cooling and heating operations may be performed once or may be repeated two or more times.

In the high-temperature melting method, the temperature around room temperature (−10 to
At 40 ° C.), the cellulose acylate is gradually added to the organic solvent with stirring. When using multiple solvents,
The order of addition is not particularly limited. For example, after adding cellulose acylate to the main solvent, another solvent (eg, a gelling solvent such as alcohol) may be added, or conversely, after the gelling solvent is wetted in advance by the cellulose acylate. May be added, which is effective in preventing heterogeneous dissolution. The cellulose acylate solution of the present invention is preferably added with cellulose acylate in a mixed organic solvent containing various solvents and swelled in advance. In that case,-
In any one of the solvents at 10 to 40 ° C., the cellulose acylate may be gradually added with stirring, or may be swelled in advance with a specific solvent in some cases, and then mixed with another solvent, followed by uniform addition. A swelling liquid may be used, or the remaining solvent may be added after swelling with two or more solvents. The dissolution concentration of cellulose acylate is 5% by weight to 30%.
% By weight, more preferably 15% to 30% by weight, and even more preferably 17% to 25% by weight. Next, the cellulose acylate and the solvent mixture are mixed in a pressure vessel at a pressure of 0.2 to 30 MPa under a pressure of 70 to 240 MPa.
° C, more preferably 80 to 220 ° C, still more preferably 1 to
It is heated to 00-200C, most preferably 100-190C. Thereafter, the mixture is cooled to a temperature lower than the lowest boiling point of the solvent used. In that case, it is common to cool to −10 to 50 ° C. and return to normal pressure. The cooling may be performed only at room temperature, and more preferably a coolant such as cooling water may be used. These heating and cooling layers may be performed once or may be repeated two or more times.

The optical characteristics of the present invention will be described. First, the in-plane retardation (Re) of the film is described by an ellipsometer (Ellipsometer AEP).
-100: manufactured by Shimadzu Corporation) at a wavelength of 63
It is obtained by multiplying the in-plane vertical and horizontal refractive index difference at 2.8 nm by the film thickness, and is obtained by the following equation. Re = (nx−ny) × d nx: refractive index in the horizontal direction, ny: refractive index in the vertical direction A smaller value indicates that there is no optical anisotropy in the in-plane direction. Used. or,
The retardation (Rth) in the thickness direction of the film is also important, and is obtained by multiplying the birefringence in the thickness direction at a wavelength of 632.8 nm by the film thickness, and is obtained by the following equation. Rth = {(nx + ny) / 2-nz} × d nx: refractive index in the horizontal direction, ny: refractive index in the vertical direction, nz:
A smaller refractive index in the thickness direction indicates that there is no optical anisotropy in the thickness direction, but a preferable range is determined depending on the intended use. Generally, Rth of the cellulose ester film of the present invention is 0 nm to 600 nm per 100 μm.
And further used at 0 nm to 400 nm.

Additives 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 carboxylic esters include phthalic esters and citric esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and dioctyl phthalate (DO).
P), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include O-acetyl triethyl citrate (OACTE) and O-acetyl tributyl citrate (OACTB), acetyl triethyl citrate, acetyl tributyl citrate. Examples of carboxylic esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitates. Examples of glycolic acid esters include triacetin, tributyrin, butylphthalylbutyl glycolate, ethylphthalylethyl glycolate,
Examples include methylphthalylethyl glycolate and butylphthalylbutyl glycolate. Among these, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate,
Dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethylhexyl phthalate, triacetin, and ethyl phthalyl ethyl glycolate are preferred. Particularly, triphenyl phosphate, diethyl phthalate, and ethyl phthalyl ethyl glycolate are preferred. These plasticizers may be used alone or in combination of two or more. The added amount of the plasticizer is preferably 5 to 30% by weight or less, particularly preferably 8 to 16% by weight or less based on the cellulose acylate. These compounds may be added together with the cellulose acylate or the solvent when preparing the cellulose acylate solution, or may be added during or after the solution is prepared.

In the present invention, as a plasticizer for reducing the optical anisotropy, (di) pentaerythritol esters described in JP-A-11-124445,
Glycerol esters described in JP-A-246704, diglycerol esters described in JP-A-2000-63560, citrate esters described in JP-A-11-92574, and substituted phenyl phosphate esters described in JP-A-11-90946. It is preferably used.

In the present invention, a deterioration inhibitor (eg, an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, an amine) and an ultraviolet inhibitor may be added. . These are disclosed in JP-A-3-199201 and 5-1.
Nos. 907073, 5-194789, 5-271
Nos. 471, 6-107854, 6-118233
Nos., 6-148430, 7-11056, 8
Nos. -29619, 8-239509 and 7-110
No. 56 describes each. Preferred examples of the deterioration inhibitor include butylated hydroxytoluene (BHT). The amount of the deterioration inhibitor to be added is preferably 0.01 to 1% by weight, more preferably 0.01 to 0.2% by weight of the solution (dope) to be prepared. Hindered phenol compounds are preferred as preferred UV inhibitors, and 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. Especially 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. Also, a hydrazine-based metal deactivator such as N, N'-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine or tris (2,4-di-tert-butyl) A phosphorus-based processing stabilizer such as phenyl) phosphite may be used in combination. The addition amount of these UV inhibitors is preferably 1 ppm to 1.0% by weight relative to cellulose acylate,
000 ppm is more preferred.

In the present invention, a colorant compound for preventing light piping may be added. The content of the coloring agent is 10 to 1000 pp in weight ratio to the cellulose acylate.
m is preferable, and 50 to 500 ppm is more preferable. In the present invention, kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, inorganic fine particles such as alumina, calcium, heat stabilizers such as salts of alkaline earth metals such as magnesium, antistatic agents, It is also preferable to add a flame retardant, a lubricant, an oil agent and the like.

In the present invention, the dope thus prepared is cast and dried to form a film. However, it is preferable that the dope is preliminarily concentrated in order to minimize the load in a possible process.
The method for enrichment is not particularly limited, and examples thereof include the following method. A method in which a low-concentration solution is introduced between a cylindrical body and a rotation locus of the outer periphery of a rotating blade rotating in a circumferential direction inside the cylinder, and a high-concentration solution is obtained by evaporating a solvent by giving a temperature difference between the solution and the solution ( For example, a heated low-concentration solution is blown from a nozzle into a container, and is described in JP-A-4-259511.
A method in which the solvent is flash-evaporated until the solution hits the inner wall of the container from the nozzle, the solvent vapor is extracted from the container, and the high-concentration solution is extracted from the container bottom (for example,
U.S. Pat. Nos. 254,012, 2,858,229 and 4,
Nos. 414341 and 4504355)

The film formation of the cellulose acylate of the present invention comprises:
Conventionally, a solution casting film forming method and a solution casting film forming apparatus used for producing a cellulose acylate film are used. The dope having a solid content of 10 to 40% prepared from a dissolving machine (pot) is temporarily stored in a tank, and bubbles contained in the dope are defoamed, or an appropriate filter medium such as a wire mesh or flannel is used. Foreign substances such as undissolved matter, dust and impurities are removed by filtration. The dope is fed from the storage tank to the casting unit through a pressurized fixed-quantity gear pump that can send fixed-quantity liquid with high precision by, for example, the number of rotations. The casting method is as follows: a method of uniformly extruding the dope from the pressing die onto the support, a method of adjusting the film thickness of the dope once cast on the support with a blade, or a reverse rotation. Although there is a method using a reverse roll coater in which adjustment is performed using a roll, a method using a pressure die is preferable. As the pressure die, there are a coat hanger type, a T-die type and the like, all of which can be preferably used, and the pressure die is installed above the support.

Two or more pressure dies may be provided to co-cast two or more cellulose acylate solutions. Specifically, the following method is mentioned. 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, JP-A-61-158414,
JP-A-1-122419, JP-A-11-198285
The method described in the item can be applied). A cellulose acylate solution is cast from two casting ports (for example, JP-B-60-27562, JP-A-61-9).
No. 4724, JP-A-61-947245, JP-A-61-947245
The methods described in JP-A-104813, JP-A-61-158413, and JP-A-6-134933 can be applied. (A method described in JP-A-56-162617 is applicable). Using two casting ports, the film formed 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 Patent Publication No. 44-20235). The method described can be applied). These co-cast cellulose acylate solutions may be the same solution or different cellulose acylate solutions, and are not particularly limited. Multiple functional layers (eg, adhesive layer, dye layer, antistatic layer, antihalation layer, UV
It is also possible to simultaneously cast an absorbing layer and a polarizing layer.

The dope extruded in this manner is uniformly cast on a support (a band or a drum running endlessly). The surface of the support is preferably finished in a mirror surface state, and a drum finished in a mirror surface by chrome plating or a stainless steel band finished in a mirror surface by surface polishing is preferable. The surface temperature of these supports is preferably 10 ° C. or less. At the peeling point where the support has made one round, the freshly dried dope film (also called web) is peeled from the support. During this time, the point is to volatilize the solvent from the dope to obtain a target residual solvent. That is,
If the solvent concentration in the vicinity of the surface of the belt in the thickness direction of the dope film is too high, the dope remains on the belt when peeled off, which hinders the next casting. Further, the web strength must be strong enough to withstand the peeling force. 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 conducting heat from the belt or drum back surface is more effective than the method of drying by blowing air from the dope surface. Can be reduced. Drying of the dope generally involves applying hot air from the front side of the support (drum or belt), that is, the surface of the dope on the support, applying hot air from the back of the drum or belt, or controlling the temperature of the liquid. A liquid heat transfer method is available in which the surface of the belt or the drum is brought into contact with the dope from the side opposite to the dope casting surface, and the surface temperature is controlled by heating the drum or the belt by heat transfer. The surface temperature of the support before casting may be any number of times as long as it is lower than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose the fluidity on the support, it is necessary to set the temperature to 1 to 10 ° C. lower than the boiling point of the solvent having the lowest boiling point among the solvents used. preferable. The preferable drying temperature is 40 to 250 ° C, particularly preferably 70 to 180 ° C. In order to further remove the residual solvent, drying at 50 to 160 ° C., and in that case, drying with a high-temperature air having a sequentially changed temperature to evaporate the residual solvent is preferably used. The above method is described in Tokuhei 5-1.
No. 7844 describes this. According to this method, the time from casting to stripping can be reduced.
The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, and may be appropriately selected according to the type and combination of the solvents used. The amount of the residual solvent in the final film is preferably 2% by weight or less, more preferably 0.4% by weight or less in order to obtain a film having good dimensional stability.

In the drying step of the web peeled off 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 this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point, for example, a method of drying all the steps or a part of the steps as described in JP-A-62-46625 while holding both ends of the width of the web with clips in the width direction (tenter method) Is preferred.

In the present invention, a dried web (film) is used.
It is also preferable to positively stretch in the width direction. For example,
JP-A-62-115035, JP-A-4-152125
Nos. 4-284221, 4-298310, and 11-48271. 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 stretching of the film is performed at normal temperature or under heating conditions. The heating temperature is preferably equal to or lower than the glass transition temperature of the film. The stretching of the film may be uniaxial stretching or biaxial stretching. The film can be stretched during the drying process, and is particularly effective when the solvent remains.
For example, if the speed of the film transport roller is adjusted so that the film winding speed is higher than the film peeling speed, the film is stretched. The film can also be stretched by transporting the film while holding the width of the tenter and gradually increasing the width of the tenter. After drying the film, it can be uniaxially stretched using a stretching machine. A preferred stretching ratio of the film (ratio of increase by stretching to the original length) is 10 to 30%. The steps from casting to post-drying may be performed under an air atmosphere or under an inert gas atmosphere such as nitrogen gas.

The winding machine relating to the production of the cellulose acylate film of the present invention may be a commonly used one, such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with constant internal stress, and the like. Can be wound up. The thickness of the finished (after drying) 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 thickness of the film may be adjusted by adjusting the concentration of the solid content contained in the dope, the slit gap of the die, the extrusion pressure from the die, the speed of the support, and the like so as to obtain the desired thickness. In addition to these film-forming methods, various methods for casting a film of a conventionally known cellulose acylate solution (for example, JP-A Nos. 61-94724 and 61-1480).
No. 13, JP-A-4-85011 and JP-A-4-286611
No. 5,185,443, No. 5-185445, No. 6-278149, No. 8-207210) can be preferably used, taking into account the difference in the boiling point of the solvent used. By setting the conditions, the same effects as those described in the respective publications can be obtained.
The cellulose acylate film of the invention may be provided with an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. by coating after film formation.

The cellulose acylate film of the present invention thus obtained can be used for the following purposes. Optical Compensation Sheet of Liquid Crystal Display The cellulose acylate film of the invention is particularly effective when used as an optical compensation sheet of a liquid crystal display. In the cellulose acylate film of the 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 the cellulose acylate film are arranged so as to be substantially parallel or perpendicular. Is preferred. The arrangement of such a polarizing element and an optical compensation sheet is described in JP-A-10-48420.
The liquid crystal display device has a liquid crystal cell holding liquid crystal between two electrode substrates, two polarizing elements disposed on both sides thereof,
And at least one optical compensatory sheet is disposed between the liquid crystal cell and the polarizing element. The liquid crystal layer of a liquid crystal cell is usually formed by enclosing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on a 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 bonding the transparent electrode layer). These layers are usually provided on a substrate. The substrate of the liquid crystal cell is generally 80 to 5
It has a thickness of 00 μm. The optical compensation sheet is a birefringent film for removing coloring of the liquid crystal screen. The cellulose acylate film of the present invention itself can be used as an optical compensation sheet. Further, in order to improve the viewing angle of the liquid crystal display device, the cellulose acylate film of the present invention and a film exhibiting the opposite birefringence (positive / negative relationship) may be used as an optical compensation sheet. . The thickness range of the optical compensation sheet is the same as the preferred thickness of the film of the present invention described above. Examples of the polarizing film of the polarizing element include an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. All polarizing films are generally manufactured using a polyvinyl alcohol-based 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 a hard coat, an anti-fog treatment, an anti-glare treatment and an anti-reflection treatment. As described above, an optical compensatory sheet in which an optically anisotropic layer containing a liquid crystal (particularly discotic liquid crystal molecules) is provided on a support has been proposed (JP-A-3-9325).
No. 6-148429, No. 8-50206, No. 9
No. 26572). The cellulose acylate film of the invention can be used as a support for such an optical compensation sheet.

Optically Anisotropic Layer Containing Discotic Liquid Crystalline Molecules It is preferable that the optically anisotropic layer is a layer containing discotic liquid crystal molecules having negative uniaxiality and being obliquely aligned. It is preferable that the angle between the discotic surface of the discotic liquid crystalline molecules and the support surface changes in the depth direction of the optically anisotropic layer (hybrid alignment).
The optical axis of the discotic liquid crystal molecule exists in the direction normal to the disk surface. Discotic liquid crystal molecules have a 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 oriented substantially horizontally with respect to the support surface.

VA Liquid Crystal Display 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 having a VA mode liquid crystal cell. In the optical compensation sheet used for the VA-mode liquid crystal display device, it is preferable that the direction in which the absolute value of the retardation is minimum does not exist in the plane of the optical compensation sheet nor in the normal direction. The optical properties of the optical compensatory 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 using two optical compensation sheets in a VA liquid crystal display device,
The in-plane retardation of the optical compensation sheet is from -5 nm to
It is preferable to be within the range of 5 nm. Therefore, the absolute value of the in-plane retardation of each of the two optical compensation sheets is preferably set to 0 to 5. When one optical compensatory sheet is used for a VA liquid crystal display device, the in-plane retardation of the optical compensatory sheet is set to -10 nm to 10 n.
It is preferable to be within the range of m.

OCB Type Liquid Crystal Display Device and HAN Type Liquid Crystal Display Device The cellulose acylate film of the present invention comprises an OCB type liquid crystal display device having an OCB mode liquid crystal cell or an HB type liquid crystal display device.
It is also advantageously used as a support for an optical compensation sheet of a HAN type liquid crystal display device having an AN mode liquid crystal cell. O
In the optical compensation sheet used for the CB 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 the 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 compensatory sheet used in the OCB type liquid crystal display device or the HAN type liquid crystal display device also include the optical properties of the optically anisotropic layer, the optical properties of the support, and the optically anisotropic layer and the support. Is determined by the arrangement.

Other Liquid Crystal Display Device The cellulose acylate film of the present invention is manufactured by using an ASM (Ax
It is also advantageously used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a liquid crystal cell of ially symmetry aligned microcell (mode) mode. 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 T
This is the same as the N-mode liquid crystal cell. Regarding the ASM mode liquid crystal cell and the ASM type liquid crystal display device, a paper by Kume et al. (Kume et al., SID 98 Digest 1089 (199)
8)). The cellulose acylate film of the invention may be used as a support for an optical compensation sheet of a TN type liquid crystal display 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. An optical compensatory sheet used for a TN type liquid crystal display device is disclosed in JP-A-3-9325.
No. 6-148429, No. 8-50206, No. 9
No. 26572.

[0038]

EXAMPLES In each of the examples, cellulose acylate,
The chemical and physical properties of solutions and films are
It was measured and calculated as follows.

(1) Degree of acetylation (%) of cellulose acylate The degree of oxidation was measured by a saponification method. The dried cellulose acylate is precisely weighed and dissolved in a mixed solvent of acetone and dimethyl sulfoxide (volume ratio: 4: 1), and a predetermined amount of a 1N aqueous solution of sodium hydroxide is added thereto, and saponified at 25 ° C. for 2 hours. did. Phenolphthalein was added as an indicator, and excess sodium hydroxide was titrated with 1N-sulfuric acid (concentration factor: F). A blank test was performed in the same manner as described above. Then, the degree of acetylation (%) was calculated according to the following equation. Degree of acetylation (%) = (6.05 × (BA) × F) / W In the formula, A is the amount of 1N-sulfuric acid (ml) required for titration of the sample,
B is the amount of 1N sulfuric acid (ml) required for the blank test, F
Represents a factor of 1N-sulfuric acid, and W represents a sample weight.

(2) Average molecular weight and molecular weight distribution of cellulose acylate A high performance liquid chromatography system (GPC) in which a gel filtration column is connected with a detector for detecting refractive index and light scattering.
-LALLS). The measurement conditions are as follows. Solvent: methylene chloride Column: GMH × 1 (manufactured by Tosoh Corporation) Sample concentration: 0.1 W / v% Flow rate: 1 ml / min Sample injection volume: 300 μl Standard sample: polymethyl methacrylate (Mw = 188, 200) Temperature : 23 ℃

(3) Viscosity-average degree of polymerization (DP) of cellulose acylate Approximately 0.2 g of absolutely dried cellulose acylate is precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride: ethanol = 9: 1 (weight ratio). did. This was measured for drop seconds at 25 ° C. using an Ostwald viscometer, and the degree of polymerization was determined by the following equation. ηrel = T / T0 T: Falling seconds of the measured sample [η] = (1nηrel) / C T0: Falling seconds of the solvent alone DP = [η] / Km C: Concentration (g / l) Km: 6 × 10 ^-Four

(4) Solution Stability The state of the obtained solution or slurry was observed while standing at room temperature (23 ° C.), and evaluated in the following four grades A, B, C and D. A: Transparency and liquid uniformity are shown even after 20 days. B: Transparency and liquid uniformity were maintained for 10 days, but slight cloudiness was observed after 20 days. C: At the end of liquid preparation, the liquid is transparent and uniform, but after one day, it gels and becomes a non-uniform liquid. D: The liquid is opaque and non-uniform with no swelling / dissolution.

(5) Film surface condition The film was visually observed, and its surface condition was evaluated as follows. A: The film surface is smooth. B: The film surface is smooth, but some foreign matter is observed. C: Weak irregularities are seen on the film surface, and the presence of foreign matter is clearly observed. D: Irregularities are seen on the film, and many foreign matters are seen.

(7) Film tear test A sample cut to 50 mn × 64 mm was subjected to ISO 638.
The tear load required for tearing was determined according to the standard of 3 / 2-1983.

(8) Folding test of film A sample cut to 120 mn was subjected to ISO 8776 / 2-1.
According to the standard of 988, the number of reciprocations until cutting by bending was determined.

(9) Moisture / heat resistance of the film 1 g of the sample was folded and placed in a 15 ml glass bottle.
After humidity control at a temperature of 90 ° C. and a relative humidity of 100%, the container was sealed. This was taken out after 10 days at 90 ° C. The state of the film was visually checked, and the following judgment was made. A: No abnormality is observed. B: Slightly decomposed odor is observed. C: Remarkably decomposed odor is observed. D: Decomposed odor and shape change due to decomposition are observed.

(10) Film retardation (R
e) Value A front retardation value measured from a direction perpendicular to the film surface at a wavelength of 632.8 nm was determined using an ellipsometer (Ellipsometer AEP-100: manufactured by Shimadzu Corporation).

(11) The haze of the film was measured using a haze meter (Model 1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.).

Example 1 (1-1) Preparation of Cellulose Acylate Solution Cellulose acylate solutions were prepared by the following three dissolving methods. Table 1 shows the detailed solvent composition of each Example and Comparative Example. In addition, silica particles (particle diameter 20n)
m), triphenyl phosphate / biphenyl diphenyl phosphate (1/2), 2,4-bis- (n-
Octylthio) -6- (4-hydroxy-3,5-di-
(tert-butylanilino) -1,3,5-triazine was added in an amount of 0.5% by mass of cellulose acylate,
% By mass and 1.0% by mass.

(1-1a) Room temperature dissolution (described as "room temperature" in Table 1) Cellulose acylate shown in Table 1 is gradually added to a solvent with good stirring, and the mixture is heated at room temperature (25 ° C.) for 3 hours. Leave to swell. The resulting swollen mixture was dissolved with stirring at 50 ° C. in a mixing tank with a reflux condenser.

(1-1b) Cooling dissolution (described as "cooling" in Table 1) Cellulose acylate shown in Table 1 was gradually added to a solvent with good stirring, and the mixture was stirred at room temperature (25 ° C.) for 3 hours. Leave to swell. The resulting swelled mixture was cooled to −30 ° C. at −8 ° C./min with slow stirring, then cooled to the temperature shown in Table 1, and after 6 hours, the temperature was raised at + 8 ° C./min to increase the sol content. At a stage where the conversion to a certain extent proceeded, stirring of the contents was started. The mixture was heated to 50 ° C. to obtain a dope.

(1-1c) High pressure and high temperature melting ("High temperature" is shown in Table 1)
The cellulose acylate shown in Table 1 was gradually added to the solvent with good stirring, and allowed to stand at room temperature (25 ° C.) for 3 hours to swell. The obtained swollen mixture was placed in a double-walled stainless steel closed container. By passing high-pressure steam through the outer jacket of the vessel, it is heated at + 8 ° C / min.
It was kept at the temperature shown in Table 1 for 5 minutes. Thereafter, 50 ° C. water was passed through the outer jacket and cooled to −50 ° C. at −8 ° C./min to obtain a dope.

(1-2) Filtration of Cellulose Acylate Solution Next, the obtained dope was filtered at 50 ° C. at an absolute filtration accuracy of 0.0
Filter with 1 mm filter paper (Toyo Roshi Kaisha, Ltd., # 63),
Further, the solution was filtered through a filter paper (FH025, manufactured by Pall Corporation) having an absolute filtration accuracy of 0.0025 mm.

(1-3) Preparation of Cellulose Acylate Film The cellulose acylate solution prepared in (1-2) was cast on a glass plate so as to have a dry film thickness of 100 μm. After drying at 70 ° C. for 3 minutes and at 130 ° C. for 5 minutes, the film was peeled off from the glass plate and dried stepwise at 160 ° C. for 30 minutes to evaporate the solvent to obtain a cellulose acylate film.

[0055]

[Table 1]

(1-3) Result The obtained cellulose acylate solution and film were evaluated according to the above-mentioned items. The cellulose acylate solution and the film described in the examples have the solution stability,
No particular problem was observed in the mechanical and optical properties of the film. On the other hand, Comparative Examples 1, 2, and 3 use carbon tetrachloride, n-heptane, and acetonitrile having dipole moments of 0.00D, 0.00D, and 3.44D, respectively, so that the solubility of cellulose acylate is insufficient. And
The surface of the film was not good either.

Further, the dope of Example 1 of the present invention was laminated on the band side and the dope of Example 2 of the present invention was laminated on the air side according to the co-casting method described in JP-A-06-134993. Was done. 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. Optically anisotropic layer, alignment film coated with polyvinyl alcohol, VA type liquid crystal display device described in FIGS. 2 to 9 of JP-A-2000-154261, JP-A-2000-154261
Nos. 6,098,067 and 4,5, and excellent performance was obtained.

[0058]

[Table 2]

[0059]

According to the present invention, there is provided a method for producing a cellulose acylate film, comprising dissolving cellulose acylate in a solvent substantially composed of a non-chlorinated solvent and then forming a film. Is in the range of 0.2 to 3.3, thereby improving the stability over time of the solution after dissolution and improving the mechanical properties and optical properties of the cellulose acylate film. The rate film manufacturing method was achieved.

Claims (6)

[Claims] 1. A method for producing a cellulose acylate film, comprising dissolving cellulose acylate in a solvent substantially composed of a non-chlorinated solvent and then forming a film, wherein the dipole moment of the solvent is from 0.2 to 0.2. (3) A method for producing a cellulose acylate film, which is in the range of (3). 2. The method for producing a cellulose acylate film according to claim 1, wherein the mixed solvent comprises 60 to 98% by mass of a main solvent and 40 to 2% by mass of an alcohol. 3. The method according to claim 1, wherein the main solvent contains substantially 3 or more carbon atoms.
2. The method for producing a cellulose acylate film according to claim 1, wherein the solvent comprises at least one single or plural mixed solvent and has at least one oxygen-containing functional group in a molecule. 4. The method for producing a cellulose acylate film according to claim 3, wherein the oxygen-containing group is a functional group selected from an ether group, a carbonyl group, an ester group, and a hydroxyl group. 5. The method according to claim 1, wherein the dissolution of the cellulose acylate is -8.
The method for producing a cellulose acylate film according to claim 1, comprising a step of cooling the film to a temperature of 0 ° C or more and 0 ° C or less. 6. The method according to claim 6, wherein the dissolution of the cellulose acylate is 40 or less.
The method for producing a cellulose acylate film according to claim 1, further comprising a step of heating the film to a temperature of from 200C to 200C.