JPH11292989A - Production of cellulose triacetate film and cellulose triacetate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cellulose acetate film capable of reducing viscosity without greatly changing the concentration of a dope being readily made into a film, having excellent planarity and mechanical properties. SOLUTION: This method for producing a cellulose acetate film comprises a process for mixing two lots having the difference in viscosity average polymerization degree of 50-300 in the weight ratio of 20/80-80/20 selected from plural lots having 59.0-62.5% average acetyl content and 150-550 viscosity-average polymerization degree to give a cellulose triacetate and dissolving the cellulose triacetate in an organic solvent to prepare a dope and a film forming process by solution casting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose triacetate film useful for a silver halide photographic light-sensitive material or a liquid crystal image display and a method for producing a cellulose triacetate film.

[0002]

2. Description of the Related Art Cellulose triacetate film is
Because of its transparency and optical isotropy, it is useful for photographic materials and optical materials, and particularly, a support for a silver halide photographic light-sensitive material, a protective film for a polarizing plate in a liquid crystal display device, a color filter, and the like are typical. Use. Cellulose triacetate film is conventionally produced by a solution casting film forming method, which comprises casting a solution of cellulose triacetate dissolved in an organic solvent (hereinafter sometimes referred to as a dope) on a support, and supporting the solution. This is a method in which a web solidified on a body is peeled from a support, and an organic solvent is evaporated and dried to form a film.

In the solution casting film forming method, a prepared dope is sent to a casting apparatus by a pump, and is cast as a casting apparatus on a mirror-finished metal support running endlessly from a die, for example, and dried. The dope film (also referred to as a web) is peeled off when the support has made one round, and the drying device (whether transporting through a group of rolls or transporting the web with clips on both ends by a tenter) is performed. It is a method of applying a subbing layer or an antistatic layer with a subbing device as necessary, further drying and winding, and producing a cellulose triacetate film, which is used as a conventional means in the art. ing.

[0004] In the solution casting method, it is necessary to evaporate the solvent remaining in the cellulose triacetate film. Therefore, in order to form a film at a high speed, it is necessary to increase the drying speed. . For this reason, conventionally, a measure has been taken by increasing the drying temperature, but there is a limit to increasing the drying temperature. That is, when the cellulose triacetate film is transported in the drying step, it receives a transport tension in the transport direction, and a compressive force is easily generated in the width direction,
The high-temperature drying causes the elastic modulus of the cellulose triacetate film to drop sharply, causing buckling deformation of the cellulose triacetate film and deteriorating the flatness.

On the other hand, JP-A-62-37113 discloses a high-speed dope in which a high-concentration dope is cast on a cooling drum at 10 ° C. or lower, and then conveyed and dried while holding the width with a tenter. A method for forming a film has been proposed. In this method, since the dope is highly concentrated and gels immediately on the cooling drum, there is no fluidity of the dope film,
Even if the width is maintained by a tenter later, there is a disadvantage that the deterioration of the flatness that occurs immediately after casting cannot be corrected.

On the other hand, as a method for reducing the viscosity of the dope, Japanese Patent Application Laid-Open No. 9-40792 proposes a method using cellulose triacetate having increased amorphousness.
According to this method, low-viscosity cellulose triacetate is obtained by converting low-molecular-weight cellulose triacetate to ketones,
By washing with acetates, cellosolves, etc. to remove low molecular weight components that cause crystallization, and at the stage of producing cellulose triacetate, a sulfuric acid catalyst is used in an amount of 10 to 15% by weight with respect to cellulose, Is slightly reduced.

[0007]

Conventionally, a high-concentration dope or a dope that gels after casting has been used for high-speed film formation. However, with these dopes, leveling immediately after casting is difficult. It was difficult to obtain a cellulose triacetate film having excellent finished film flatness. The method of using the high-concentration dope, the leveling of the dope on the support immediately after casting is insufficient,
When cast from a die, melt fracture may occur and shark skin may occur in the doped film.

Conversely, in the method using a dope having a low concentration of a cellulose triacetate film, it takes time to evaporate a large amount of an organic solvent in addition to easy leveling, and it is considered that cellulose triacetate having a low polymerization degree is used. However, there is a problem that the mechanical strength (for example, tear strength, etc.) of the obtained film is significantly reduced. In the method of JP-A No. 9-40792, which uses a product from which low-molecular-weight cellulose triacetate has been removed, the cost, solvent, time and equipment for extraction are higher than that of ordinary cellulose triacetate. There is a method of slightly lowering the degree of acetylation by allowing the reaction to be carried out by including the amount by weight, and the former is complicated in processing and may increase the cost. There is a problem that it is difficult to adopt it as a practical problem due to the possibility that the mechanical strength is reduced.

It is an object of the present invention to provide a cellulose triacetate film which is reduced in viscosity without changing the concentration of the dope, is easy to form a film, and has excellent flatness and mechanical properties.

[0010]

Means for Solving the Problems As a result of diligent studies on the above-mentioned problems, the present inventors have succeeded in solving various problems which have been regarded as disadvantages by using a dope having a relatively low viscosity.
That is, in order to lower the viscosity of the dope, paying attention to the viscosity average polymerization degree of cellulose triacetate, even if a low viscosity average polymerization degree coexists, the mechanical properties are enhanced by the presence of a certain percentage of high cellulose triacetate or more. They found that it could be raised, and succeeded in lowering the viscosity.

The above object of the present invention has been attained by the following constitutions.

(1) Average degree of acetylation is 59.0 to 62.5%
Out of a plurality of lots having a viscosity average degree of polymerization in the range of 150 to 550, two lots having a difference in viscosity average degree of polymerization of 50 to 300 as weight ratios of 20/80 to 80 /
20. A method for producing a cellulose triacetate film, comprising: dissolving the cellulose triacetate mixed in Step 20 in an organic solvent to prepare a dope; and producing the dope through a solution casting film forming step.

(2) The method for producing a cellulose triacetate film according to (1), wherein the concentration of cellulose triacetate in the dope is 10 to 35% by weight.

(3) The method for producing a cellulose triacetate film according to (1) or (2), wherein the dope contains 5 to 30% by weight of a plasticizer based on cellulose triacetate.

(4) 75-98% by weight of the organic solvent
Methylene chloride and 2 to 25% by weight of carbon atom 1
The method for producing a cellulose triacetate film according to any one of (1) to (3), wherein the method further comprises: alcohols (1) to (3).

(5) 75-87% by weight of the organic solvent
The method for producing a cellulose triacetate film according to (4), wherein the method comprises (1) methylene chloride and 13 to 25% by weight of an alcohol having 1 to 6 carbon atoms.

(6) The organic solvent according to any one of (1) to (3), wherein the organic solvent contains at least 60% by weight or more of at least one selected from acetone, methyl acetate and ethyl formate. The method for producing a cellulose triacetate film according to the above item.

(7) The organic solvent is 60 to 95% by weight.
The method for producing a cellulose triacetate film according to (6), comprising at least one selected from the group consisting of methyl acetate and ethyl formate, and 5 to 40% by weight of acetone.

(8) The step of preparing the dope is performed by adding a mixture obtained by adding cellulose triacetate to an organic solvent to -10.
A step of cooling to 0 to -10 ° C;
A process of dissolving the cellulose triacetate by heating to 120 ° C., the method for producing a cellulose triacetate film according to any one of (1) to (7).

(9) In the step of preparing the dope, a mixture obtained by adding cellulose triacetate to an organic solvent is mixed with 50 to 50%.
(1) The method includes a step of holding the mixture under a pressure of 4000 kgf / cm ² and a step of successively holding the pressurized mixture under a pressure of 0.1 to 10 kgf / cm ^2.
The method for producing a cellulose triacetate film according to any one of (7) to (7).

(10) A cellulose triacetate film produced by the method according to any one of (1) to (9).

The present invention will be described in detail.

The cellulose triacetate used in the present invention has an acetylation degree of 59.0 to 62.5%. The acetylation degree is a percentage of acetic acid (CH ₃ COOH) obtained by reacting acetic acid with a hydroxyl group of cellulose, and 62.5% is obtained when the acetic acid is reacted at the maximum. AS measurement
It can be measured by the method described in Test Methods for Cellulose Acetate of TM D-817-91.

The commonly used cellulose triacetate has a viscosity average degree of polymerization of about 250 to 600. Films, fibers or molded products made from cellulose triacetate are required to have tough mechanical strength, so that the mechanical strength is required to have a viscosity-average degree of polymerization of 200 or more to be stably obtained. The same is described in "Cellulose Handbook" edited by Hiroshi Sobue and Nobuhiko Mita, Asakura Shobo (1958), and "Plastic Materials Course 17" edited by Hiroshi Marusawa and Kazuo Uda, Nikkan Kogyo Shimbun (1970).

The viscosity-average degree of polymerization of the cellulose triacetate used in the present invention is in the range of 150 to 550. Although low viscosity and low polymerization degree are not generally used because of low mechanical strength, in the present invention, it is a method of mixing this low viscosity product with a higher viscosity average polymerization degree. Then, if the viscosity average polymerization degree of the relatively low viscosity product is about 150 to 300 and the viscosity average polymerization degree of the high viscosity product is about 250 to 550, the difference between the low viscosity average polymerization degree and the high viscosity average polymerization degree is By mixing and using two lots of 50 to 300 at a ratio of 20/80 to 80/20, a low-viscosity dope can be used without lowering the mechanical strength, and the dope viscosity can be adjusted to a target dope viscosity. Can be finished. The mixing ratio varies depending on the viscosity of each lot, but the ratio of the high viscosity lot / low viscosity lot is preferably 30/70 to 70/30, and more preferably 40/60 to 60/40.

Here, a lot is an aggregate having a certain average value when cellulose triacetate is synthesized, and one synthesis may be performed in one lot or may be performed in many lots. The number of lots used in the present invention is two, but cellulose triacetate, which may be mixed with three or more lots, is generally used for cellulose such as cotton linters and wood pulp, and for the hydroxyl group of cellulose as a reactant. The reaction is carried out using an excess amount of acetic anhydride, acetic acid or methylene chloride as a reaction solvent, and sulfuric acid as a reaction catalyst. At this time, a hydrolysis reaction also occurs at the same time, and the main chain of the cellulose molecule is cleaved to lower the degree of polymerization or the degree of acetylation. Therefore, it is necessary to control the reaction by adjusting the amount of each chemical, the temperature, the time and the like with respect to the amount of cellulose. As the lot of cellulose triacetate having a low viscosity used in the present invention, a lot prepared by controlling as described above is used, but a lot of a low-viscosity product which happens to be produced can also be used.

In the present invention, from the viewpoint of cellulose raw material, cotton linter or wood pulp may be used, or a mixture thereof may be used. Further, a lot of cellulose triacetate obtained by an acetylation reaction from a linter and a lot of cellulose triacetate from wood pulp may be mixed and used as long as the degree of polymerization is different.

The cellulose triacetate used in the present invention is preferably a photographic grade, and a commercially available photographic grade can be obtained with satisfactory qualities such as viscosity average polymerization degree and acetylation degree. Manufacturers of photographic grade cellulose triacetate include Daicel Chemical Industries, Ltd., Coatles, Hoechst, Eastman Kodak and the like, and any photographic grade cellulose triacetate can be used. In addition, low-viscosity products (low-viscosity average polymerization degree products) can also be specially purchased from manufacturers.

The organic solvent used in the dope of the present invention includes:
There is no particular limitation as long as cellulose triacetate can be dissolved alone or as a solvent that can be dissolved by mixing with other solvents.However, it can be dissolved near the boiling point of each organic solvent, or can be dissolved under a pressure close to normal pressure, for example, Halogenated hydrocarbons such as methylene chloride and ethylene chloride,
Nitro compounds such as nitromethane and nitropropane,
Cyclic diether compounds having a 4- to 7-membered ring such as 1,3-dioxolane and 1,4-dioxane;
2 to 10 carbon atoms such as trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol
Is preferably used. Organic solvents which are difficult to dissolve cellulose triacetate in the above-mentioned state may be dissolved after low-temperature treatment or by treatment under high pressure. Examples of suitable organic solvents include esters such as methyl acetate and ethyl formate, ketones such as acetone, methyl ethyl ketone and cyclohexanone, and in the present invention, methyl acetate, ethyl formate and acetone are preferably used. . Any organic solvent is preferably used in an amount of 60% by weight or more based on the total organic solvent in the dope.

In the case where methylene chloride is used for dissolution at almost normal pressure, the ratio of methylene chloride to the total organic solvent in the dope is 75% by weight to 98% by weight.
Or less, more preferably 75% by weight or more and 87% by weight or less. In this case, it is preferable that 2 to 25% by weight of an alcohol having 1 to 6 carbon atoms coexist in order to enhance solubility or enable high-speed film formation. In particular, it is preferable to contain the alcohol in an amount of 13% by weight to 25% by weight for high-speed film formation.

In addition to methylene chloride, it has high solubility,
1,3-dioxolan and 2,2,2-trifluoroethanol having a low boiling point and a small drying load can be preferably used. Of course, these solvents may be used as a mixture with methylene chloride, acetone, methyl acetate, ethyl formate and the like.

Methyl acetate, ethyl formate and acetone as organic solvents used in the dissolution of the dope of the present invention by cooling or high-pressure dissolving do not dissolve cellulose triacetate at room temperature but only swell. -95
No. 538 or JP-A-9-95544, or the high-pressure melting method developed by the present inventors can be used for melting. However, the cellulose triacetate solution obtained by this method tends to have a high viscosity, but the present inventors can reduce the viscosity of the cellulose triacetate solution by using acetone in combination with methyl acetate or ethyl formate. I found As the ratio of using acetone in combination, methyl acetate or ethyl formate is used in an amount of 60 to 95% by weight based on the total amount of the organic solvent, and
It is particularly preferable to use them together at a ratio of ４０40% by weight.

The above organic solvent may further be mixed with a poor solvent (a solvent which does not dissolve the cellulose ester alone but swells or dissolves). For example, the above carbon atom number 1
Alcohol No. 6 was used, but these alone did not have the ability to dissolve cellulose triacetate.However, by coexistence, the solubility was improved, or a methylene chloride solution of cellulose triacetate to which a large amount of alcohol was added as a poor solvent was used. Although the viscosity is increased, when cast on a support maintained at a low temperature, the cellulose triacetate solution gels and the strength is increased, so that there is an advantage that the cellulose triacetate solution can be easily peeled off from the belt or drum of the support. However, by mixing and using the cellulose triacetate of the present invention, the viscosity of the dope can be reduced and gelation can be achieved. Examples of the poor solvent used in the present invention include methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol and t-butanol.
1 to 6 carbon atoms such as butanol and cyclohexanol
And methyl ethyl ketone, methyl isobutyl ketone, propyl acetate, monochlorobenzene, benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, ethylene glycol, monomethyl ether, toluene and the like. Among them, methanol, ethanol, propanol, n-butanol and cyclohexane are preferred. The ratio of adding these poor solvents is preferably 2 to 12% by weight for the purpose of improving the solubility of cellulose triacetate. For the purpose of gelling the cellulose triacetate solution at a low temperature, the content is preferably 13 to 25% by weight.

The method for preparing the dope according to the present invention includes a usual dissolving method prepared at a temperature lower than the boiling point of the organic solvent used in the usual method and at almost normal pressure, and a cooling dissolution prepared at a low temperature of -10 ° C. or less. And a high-pressure dissolution method prepared under high pressure.

The method of dissolving at normal pressure used in the present invention can be obtained by putting cellulose triacetate and a solvent in a dissolving vessel and stirring and mixing at room temperature or at a temperature at which the solvent does not boil. It is preferable that the stirring and mixing be performed by an apparatus or a method in which no liquid film remains inside the container. The container may be filled with an inert gas such as nitrogen gas to suppress decomposition. If necessary, the mixture may be stirred and mixed under a pressurized condition using a pressurized container or the like.

The details of the cooling dissolution method used in the present invention can be referred to the method described in the above-mentioned JP-A-9-95538. In this method, cellulose triacetate is gradually added to an organic solvent while stirring. At this stage, the cellulose triacetate is in a state of being swollen in the solvent. Next, the mixture is cooled. The cooling temperature may be a temperature equal to or higher than the freezing point of the solvent, and is in a temperature range of -100 to -10C. The lower the temperature, the shorter the dissolution time. Next, when the cooled product is heated to a temperature of 0 to 120 ° C., the cellulose triacetate dissolves in the solvent to obtain a uniform solution. The higher the heating temperature, the shorter the dissolving time can be, but the solvent may foam and bubbles may enter the cellulose triacetate solution. In this case, lower the temperature in the container to a temperature that does not foam,
The foaming may be suppressed by increasing the pressure. In order to further accelerate the dissolution, cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by visually observing the appearance of the solution. In the cooling dissolution method, it is preferable to use a closed container in order to avoid mixing of moisture due to condensation during cooling. Further, in the cooling operation, when the pressure is increased during cooling and the pressure is decreased during heating, the dissolution time can be further reduced. In order to perform pressurization and decompression, it is preferable to use a pressure-resistant container.

Further, in the high-pressure dissolution method used in the present invention, a mixture of an organic solvent and cellulose triacetate is placed in a container (for example, a bag-shaped aluminum container) in which pressure can be applied from all directions as much as possible. The cellulose triacetate solution can be prepared by dissolving by keeping the mixture under pressure and then releasing the pressure and keeping the mixture under normal pressure.In the present invention, it is preferably used as a method for dissolving an organic solvent other than methylene chloride. Can be done. First, an organic solvent (acetone, methyl acetate,
In a solvent such as ethyl formate, 1,3-dioxolan, 1,4-dioxane, or cyclohexanone, cellulose triacetate is gradually added with stirring. At this stage, the cellulose triacetate is in a state of being swollen in the solvent. The mixture is then kept under high pressure. The effect is recognized when the pressure is 50 kgf / cm ² or more. The higher the pressure, the shorter the dissolving time can be. However, if the pressure is too high, the equipment becomes too large, and the effect of shortening the dissolving time gradually becomes saturated. / Cm
If it is ² or less, a sufficient effect can be obtained. Next, the pressure is released, and the mixture is kept under a pressure of 0.1 to 10 kgf / cm ² , whereby the cellulose triacetate dissolves in the solvent to obtain a uniform solution. In addition, in order to accelerate dissolution, the operation of pressurization and release may be repeated. Whether or not the dissolution is sufficient can be determined by visually observing the appearance of the solution. The container to be dissolved is not particularly limited as long as it has strength and structure that can withstand pressure. It may be carried out batchwise using a closed container or the like, or may be carried out continuously using a single-screw or twin-screw extruder, kneader or the like.
Further, when cooling is performed in the pressurizing operation and heating is performed in the releasing operation, the dissolving time can be further reduced.

The concentration of cellulose triacetate in the dope of the present invention is preferably as high as possible from the viewpoint of drying efficiency in forming a cellulose triacetate film, but if the concentration is too high, the viscosity of the solution becomes too large. Since the planarity of the film cannot be sufficiently improved in some cases, the preferable doping concentration is in the range of 10 to 40% by weight. Further, a range of 15 to 35% by weight is preferable.

In the present invention, the concentration of cellulose triacetate in the dope may be in the range of 10 to 40% by weight from the beginning, as described above. A preferred method is to evaporate the solvent immediately before spreading to prepare a high-concentration solution. The concentration of cellulose triacetate in the low concentration solution is preferably 1 to 10% by weight, and the concentration of cellulose triacetate in the highly concentrated solution is preferably in the above range. There is no particular limitation on the concentration method.For example, a low-concentration solution is guided between the cylindrical body and the rotation trajectory of the outer periphery of the rotating blade rotating in the circumferential direction inside the cylinder, and a temperature difference is given between the solution and the solution. Method to obtain a highly concentrated solution while evaporating the solvent (for example,
JP-A-4-259511), a heated low-concentration solution is blown into a container from a nozzle, and the solvent is flash-evaporated until the solution hits the inner wall of the container from the nozzle. A method of extracting the solution from the bottom of the container (for example, USP 2,541,
012, 2,858,229, 4,414,3
No. 41, 4,504, 355, etc.) and the like.

The dope of the present invention has a low viscosity, and it is very easy to remove foreign substances such as undissolved matter, dust, and impurities by filtration, and can improve filtration efficiency.

In any of the dope preparation steps of the present invention, various additives can be added according to the intended use.

For a silver halide photographic material, a plasticizer, a colorant for preventing light piping or an ultraviolet inhibitor for improving mechanical properties or imparting water resistance, and a heat resistant material for a liquid crystal display device. It is preferable to add an antioxidant or the like that imparts moisture resistance.

As the plasticizer, phosphoric acid esters, carboxylic acid esters, glycolic acid esters and the like are preferably used. Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.Examples of carboxylate esters include dimethyl phthalate. , Diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethylhexyl phthalate, acetyl triethyl citrate, acetyl tributyl citrate, butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate, trimellitic acid ester, and the like. Examples of glycolic acid esters Triacetin, tributyrin, butylphthalylbutyl glycolate, ethylphthalylethyl glycolate, methyl Phthalyl ethyl glycolate, and butyl phthalyl butyl glycolate and the like. Of 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 plasticizer is added in an amount of 5 to 30% by weight, especially 8% by weight, based on cellulose triacetate.
~ 16% by weight is preferred. These compounds may be added together with the cellulose triacetate and the solvent during the preparation of the cellulose triacetate solution, or may be added during or after the solution preparation.

Further, the following general formula (I), (II) or (II)
Compounds represented by I) may be added.

[0045]

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In the formulas (I), (II) and (III),
R is an alkyl group having 1 to 4 carbon atoms. Examples of the compound represented by the above general formula (I), (II) or (III) include sodium 2,2'-methylenebis (4,6-di-t-butylphenyl) phosphate (ADEKA STAB NA-10, Asahi Denka Co., Ltd.) and screws (p
-Ethylbenzylidene) sorbitol (NC-4, manufactured by Mitsui Toatsu Chemicals, Inc.).

As the antioxidant, those represented by the following general formula (IV) are used.

[0048]

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R _{1 in the} general formula (IV) represents an alkyl group,
R ₂ , R ₃ and X each represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, an alkoxy group,
Alkenoxy group, aryloxy group, alkylthio group,
Represents an alkenylthio group, an arylthio group, a heterocyclic oxy group, a hydroxy group, an amino group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a halogen atom, a nitro group, a cyano group, an acyl group, and an acyloxy group. m represents an integer of 0 to 2. R ₂ , R ₃ and X may be the same or different. Examples of the alkyl group include a linear, branched, or cyclic alkyl group such as methyl, ethyl, propyl, i-propyl, t-butyl, cyclohexyl, t-hexyl, t-octyl, dodecyl, hexadecyl, octadecyl, and benzyl. Wherein the alkenyl group represents, for example, a linear, branched, or cyclic alkenyl group such as vinyl, allyl, 2-pentenyl, cyclohexenyl, hexenyl, dodecenyl, and octadecenyl; and the aryl group includes, for example, phenyl, Represents a benzene monocyclic or condensed polycyclic aryl group such as naphthyl and anthranyl, and the heterocyclic group includes, for example, nitrogen atom, sulfur atom, oxygen atom such as furyl, pyrrolyl, imidazolyl, pyridyl, prenyl, chromanyl, pyrrolidyl, and morpholinyl. Consisting of a 5- to 7-membered ring containing at least one atom A representative. Among them, hindered phenol compounds are preferable, and 2,6-di-t-butyl-p-cresol, pentaerythrityl-
Tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4
-Hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4
-Bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3
5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N,
N'-hexamethylenebis (3,5-di-t-butyl-
4-hydroxy-hydrocinnamamide), 1,3,5-
Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris-
(3,5-di-t-butyl-4-hydroxybenzyl)
-Isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-
Tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4
-Hydroxyphenyl) propionate] is most preferred. Further, for example, N, N'-bis [3- (3,5-di-
t-butyl-4-hydroxyphenyl) propionyl]
A hydrazine-based metal deactivator such as hydrazine or a phosphorus-based processing stabilizer such as tris (2,4-di-t-butylphenyl) phosphite may be used in combination. The addition amount of these compounds is preferably 1 ppm to 1.0% by weight relative to cellulose triacetate,
pm is more preferred.

Examples of the coloring agent for preventing light piping include compounds represented by the following formulas (V) and (VI).

[0051]

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[0052] wherein, X represents an oxygen atom of the general formula (V) and (VI), or represents NR _23. R _{1 to} R ₈ and R _{12 to} R ₂₃ are
A hydrogen atom, a hydroxyl group, an aliphatic group, an aromatic group, a heterocyclic group, a halogen atom, a cyano group, a nitro group, COR ₉ ,
COOR ₉ , NR ₉ R ₁₀ , NR ₁₀ COR ₁₁ , NR ₁₀ SO ₂
R ₁₁ , CONR ₉ R ₁₀ , SO ₂ NR ₉ R ₁₀ , COR ₁₁ , S
O ₂ R ₁₁ , OCOR ₁₁ , NR ₉ CONR ₁₀ R ₁₁ , CONH
Represents SO ₂ R ₁₁ or SO ₂ NHCOR _11, and represents R ₉ , R ₁₀
Represents a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group, and R ₁₁ represents an aliphatic group, an aromatic group, or a heterocyclic group.

The aliphatic group represented by R _{1 to} R ₂₃ is an alkyl group having 1 to 20 carbon atoms (eg, methyl, ethyl, n-
Butyl, isopropyl, 2-ethylhexyl, n-decyl, n-octadecyl), a cycloalkyl group having 1 to 20 carbon atoms (eg, cyclobenzyl, cyclohexyl) or an allyl group, which further has a substituent (eg, a halogen atom) A hydroxyl group, a cyano group, a nitro group, a carboxylic acid group, an aryl group having 6 to 10 carbon atoms, an amino group having 0 to 20 carbon atoms, an amide group having 1 to 20 carbon atoms, a carbamoyl group having 1 to 20 carbon atoms, carbon An ester group having 2 to 20 carbon atoms, an alkoxy group or an aryloxy group having 1 to 20 carbon atoms, 1 carbon atom
It may have a sulfonamide group of 20 to 20, a sulfamoyl group of 0 to 20 carbon atoms, or a 5- or 6-membered heterocyclic ring. R
₁ aromatic group represented by to R ₂₃ is from 6 to 10 carbon atoms, phenyl, aryl groups such as naphthyl, the substituents and methyl having 1 to 20 carbon atoms mentioned above, ethyl, n- butyl, t It may have a substituent consisting of an alkyl group such as -butyl and octyl. The heterocyclic group represented by R _{1 to} R ₁₁ represents a 5- or 6-membered heterocyclic ring, and may have the substituent described above. The following general formulas (V) and (V)
Preferred examples of the compounds represented by I) (V-1) to (V-
25) and (VI-1) to (VI-4).

[0054]

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[0055]

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[0056]

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[0057]

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[0058]

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[0059]

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The content of the colorant is preferably from 10 to 1000 ppm, more preferably from 50 to 500 ppm by weight based on cellulose triacetate. By including the coloring agent in this manner, light piping of the cellulose triacetate film can be reduced, and the yellow tint can be improved. These compounds may be added together with cellulose triacetate or an organic solvent during the preparation of the dope, or may be added during or after solution preparation.

Further, various additives may be added to the dope of the present invention as needed at any stage after the preparation of the solution or after the preparation. As additives, ultraviolet absorbers,
Inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina; heat stabilizers such as salts of alkaline earth metals such as calcium and magnesium; antistatic agents; flame retardants; lubricants; Oils and the like.

It is preferable that the dope to which these additives are added is subjected to filtration and removal of foreign substances such as undissolved matter, dust, and impurities by using a suitable filter medium such as a wire mesh or flannel before casting.

A method for forming a cellulose triacetate film using the dope of the present invention will be described.

As the equipment for producing the cellulose triacetate film of the present invention, the equipment of the solution casting method conventionally used for the production of cellulose triacetate film can be used. The dope prepared by the above-described preparation apparatus is sent to a pressurized die through a pressurized fixed-quantity gear pump that can perform high-precision fixed-quantity liquid supply by, for example, the number of rotations. The dope sent from the precision gear pump to the pressure die is uniformly cast from the die (slit) of the pressure die onto the support that is rotating endlessly. As a web, the support is dried while being passed through a set of rotating rolls, and the dried film is conveyed and wound up to a predetermined length by a winder.

As a casting method useful in the present invention, a method in which the prepared dope is uniformly extruded from a pressure die onto a support, and a film thickness of the dope once cast on the support is adjusted by a blade. There is a casting apparatus such as a method using a doctor blade or a method using a reverse roll coater that adjusts with a roll that rotates in the reverse direction, but a method using a pressure die is preferable. The pressure die includes a coat hanger type and a T-die type, and any of them can be preferably used. Also,
In addition to the methods mentioned here, various methods for casting cellulose triacetate from a conventionally known cellulose triacetate solution (for example, JP-A-61-94724).
No. 61-148013, JP-A-4-85011
Nos. 4-286611, 5-185443, 5-185445, 6-278149, and 8-2
No. 07210) can be preferably used, and by setting each condition in consideration of the difference in the boiling point of the solvent to be used, the same effects as those described in the respective publications can be obtained.

As the support running endlessly used for producing the cellulose triacetate film of the present invention, a drum whose surface is mirror-finished by chrome plating or a stainless steel belt (such as a band) whose surface is mirror-finished by surface polishing is used. May be used).

The arrangement of the pressure die used for producing the cellulose triacetate film of the present invention on the support is as follows.
Or two or more units may be installed. Preferably it is one or two. When two or more units are installed, the amount of the dope to be cast may be divided into various ratios for each die, and a plurality of precision metering gear pumps separate the dope into the die at each ratio.

The drying of the dope on the support in the production of the cellulose triacetate film of the present invention is generally carried out by a method in which hot air is blown from the surface of the drum or belt, that is, from the surface of the web on the support. A method in which hot air is applied from the back of the belt, and a liquid whose temperature is controlled is brought into contact with the back of the belt or drum opposite the dope casting surface, and the drum or belt is heated by heat transfer to control the surface temperature. However, the backside liquid heat transfer method is preferable.

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 accelerate the drying and to lose the fluidity on the support, the temperature should be set to 1 to 10 ° C. lower than the boiling point of the solvent having the lowest boiling point among the solvents used. preferable.

The speed of producing the cellulose triacetate film varies depending on the length of the belt, the drying method, the composition of the dope solvent and the like, but is almost determined by the amount of the residual solvent when the web is peeled off from the belt. In other words, if 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 peeled off and hinders the next casting, so that the remaining peeling is absolutely necessary. This is because the web must have sufficient strength to withstand the peeling force. The amount of residual solvent at the time of peeling differs depending on the method of drying on the belt or drum, and the method of transferring heat from the belt or drum back surface is more effective than the method of drying by blowing air from the dope surface. The amount can be reduced.

The web involved in the production of the cellulose triacetate film of the present invention (where the web is referred to as the web from the peeled dope film to the dried film, but their boundaries are not clear. ) The drying method is described. The web peeled at the peeling position just before the support makes one round is transported alternately through a group of rolls arranged in a staggered manner, or the both ends of the peeled web are gripped with clips so as to be contactless. Drying is performed by a method of blowing air at a predetermined temperature to both surfaces of the web being conveyed or a method using a heating means such as a microwave while conveying by a conveying method or the like. Since rapid drying may impair the flatness of the web, it is preferable to dry at a temperature at which the solvent does not foam at the initial stage of drying, and to dry at a high temperature after the drying has progressed.

In the drying step after peeling from the support, the web tends to shrink in the width direction due to evaporation of the solvent. The higher the temperature, the greater the shrinkage. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the resulting 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 drying both ends of the web with clips in the width direction (tenter method) Is preferred.

Further, there is also a method of positively stretching in the width direction. In the present invention, for example, JP-A-62-115035
And JP-A-4-152125 and JP-A-4-284221.
And the stretching methods described in JP-A Nos. 4-298310 and 4-298310 can also be used.

The drying temperature in the drying step of the cellulose triacetate film of the present invention is preferably from 40 to 250 ° C., particularly preferably from 70 to 180 ° C. 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. Residual solvent content of final finished film is less than 2% by weight, further 0.4% by weight
The following is preferable in order to obtain a film having good dimensional stability.

The steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas.

The winding machine relating to the production of the cellulose triacetate film of the present invention may be a commonly used winding machine, 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. It can be wound by a winding method.

The thickness of the finished (after drying) cellulose triacetate film of the present invention varies depending on the purpose of use, but is usually in the range of 5 to 500 μm, and is preferably 40 to 500 μm.
To 250 μm is preferable, and especially 60 to 125 μm
Is most preferable. The thickness of the film may be adjusted by adjusting the concentration of the solid content contained in the dope, the slit gap between the die caps, the extrusion pressure from the die, the speed of the support, and the like so as to obtain the desired thickness.

Here, a method for measuring the acetylation degree and the viscosity average polymerization degree will be described.

1) Degree of acetylation (%) of cellulose triacetate Degree of acetylation is measured according to ASTM D817-91 and measured by a saponification method. The dried cellulose triacetate is precisely weighed, dissolved in a mixed solvent of acetone and dimethylsulfoxide (volume ratio: 4: 1), and a predetermined 1N aqueous sodium hydroxide solution is added thereto, followed by saponification at 25 ° C for 2 hours. Phenolphthalein is added as an indicator and excess sodium hydroxide is titrated with 1 N sulfuric acid (concentration factor; F). A blank test is performed in the same manner as described above. Then, the degree of acetylation (%) is calculated as follows.

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, and B is
Is the amount of 1N sulfuric acid required for the blank test (ml), F is 1
The factor of N sulfuric acid, W, indicates the sample weight.

2) Viscosity-average degree of polymerization (DP) of cellulose triacetate About 0.2 g of absolutely dried cellulose triacetate is precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride and ethanol (weight ratio 9: 1). This is measured for drop seconds at 25 ° C. using an Ostwald viscometer, and the degree of polymerization is determined by the following equation.

Ηrel = T / Ts [η] = (lnηrel) / CDP = [η] / Km where, T: number of seconds of falling of the sample to be measured Ts: number of seconds of falling of the solvent, C: concentration (g / l) Km: 6 × 10 ⁻⁴

[0083]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

The amount of residual solvent in the film was measured as follows.

The weight (W) of the test film or web containing the organic solvent was precisely weighed, and then the film or web was heated at 150 ° C. for 3 hours, and then cooled to room temperature so as not to absorb moisture. Weigh. As the weight (D) of the absolutely dried film or the absolutely dried web, the amount of residual solvent (%) = {(WD) / D} × 100.

The methods of measuring and evaluating the dope viscosity, film flatness, haze, tear strength, tensile strength, elastic modulus and bending resistance in the examples were as follows. Here, the film refers to a dried film cut out after winding in the winding step in the final stage of the cellulose triacetate film manufacturing step.

<Measurement of Dope Viscosity> The viscosity of the dope was measured with a viscometer type B (manufactured by Tokimec Co.) while maintaining the solution temperature at 30 ° C.

<Flatness> A black paper was stuck on a flat desk, a sample film of 100 cm × 40 cm was placed on it, and three fluorescent lamps arranged diagonally above were projected on the film to bend the fluorescent lamps. The flatness was evaluated according to the condition, and ranked according to the following criteria.

A: All three fluorescent lamps appear straight B: Fluorescent lamp looks slightly bent C: Fluorescent lamp looks bent D: Fluorescent lamp looks large ridge

<Haze> The haze was measured using a haze meter (model 1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS K-6714.

<Tear Strength> The film was conditioned in a room conditioned at a temperature of 23 ° C. and a relative humidity of 55% RH for 4 hours.
Cut out sample size 50mm x 64mm, ISO 63
83 / 2-1983.

<Tensile strength and elastic modulus>
After conditioning for 4 hours in a room conditioned at 55 ° C. and a relative humidity of 55% RH, the sample was cut to a width of 10 mm and a length of 200 mm.
/ Min was determined by conducting a tensile test.

<Folding Degree> The film was conditioned in a room conditioned at a temperature of 23 ° C. and a relative humidity of 55% RH for 4 hours, cut into a sample length of 120 mm, and subjected to ISO 8776 / 2-.
According to 1988, the number of times of bending until cutting by bending was measured.

Example 1 50 parts by weight of cellulose triacetate having an acetylation degree of 61.0% and a viscosity average degree of polymerization of 200, and cellulose triacetate 5 having an acetylation degree of 61.0% and a viscosity average degree of polymerization of 350
0 parts by weight and triphenyl phosphate (plasticizer) 1
0 parts by weight was dissolved in a mixed organic solvent of 376 parts by weight of methylene chloride and 24 parts by weight of ethanol to prepare a cellulose triacetate solution. The dope was allowed to stand at 30 ° C. overnight and subjected to a defoaming operation. After that, the dope was subjected to Azumi Filter Paper No. After filtration using 244, the mixture was subjected to film formation.

The obtained dope was fed to a die by a constant-rate gear pump, and was cast on a rotating stainless steel belt so that the film thickness after drying became 120 μm. The first half was dried on a belt whose temperature was controlled by contacting warm water at 30 ° C. from the back surface, and the web was dried by blowing dry air at 40 ° C. in the second half. The web is peeled off from the belt where the belt makes one round, and 100 ° C. while holding both ends of the web with clips.
For 5 minutes, and then dried at 120 ° C. for 20 minutes while being conveyed by a roll to finally obtain a cellulose triacetate film having a thickness of 120 μm. The amount of residual solvent in the film is 0.
9%.

Example 2 The film thickness was changed in the same manner as in Example 1 except that the cellulose triacetate having a viscosity average polymerization degree of 200 was changed to 20 parts by weight and the cellulose triacetate having a viscosity average polymerization degree of 350 was changed to 80 parts by weight. A 120 μm cellulose triacetate film was obtained. The residual solvent content of the film is 0.9
%Met.

Example 3 The film thickness was changed in the same manner as in Example 1 except that the cellulose triacetate having a viscosity average degree of polymerization of 200 was changed to 80 parts by weight, and the cellulose triacetate having a viscosity average degree of polymerization of 350 was changed to 20 parts by weight. A 120 μm cellulose triacetate film was obtained. The residual solvent content of the film is 0.9
%Met.

Example 4 A cellulose triacetate having a viscosity average polymerization degree of 200 had a viscosity average polymerization degree of 280 and a viscosity average polymerization degree of 35.
Of cellulose triacetate having a viscosity average polymerization degree of 33
Except that the film thickness was changed to 0,
A μm cellulose triacetate film was obtained. The residual solvent content of the film was 0.9%.

Example 5 Cellulose triacetate having a viscosity average degree of polymerization of 200 was set to a viscosity average degree of polymerization of 150, and cellulose triacetate having an acetylation degree of 61.0% and a viscosity average degree of polymerization of 350 was prepared. 0.5% and a viscosity average degree of polymerization of 40.
Except that the film thickness was changed to 0,
A μm cellulose triacetate film was obtained. The residual solvent content of the film was 0.9%.

Comparative Example 1 A cellulose triacetate having an acetylation degree of 61.0% and a viscosity average polymerization degree of 200 was changed to a viscosity average polymerization degree of 300, and 50 parts by weight thereof was changed to 100 parts by weight to one lot. In the same manner as in Example 1, a cellulose triacetate film having a thickness of 120 μm was obtained. The residual solvent content of the film was 0.9%.

Example 6 Example 1 was repeated except that 376 parts by weight of methylene chloride, 320 parts by weight of ethanol, 60 parts by weight of ethanol, and 20 parts by weight of 1-butanol were added to the mixed organic solvent. Similarly, a cellulose triacetate film having a thickness of 120 μm was obtained. The residual solvent content of the film was 0.9%.

Comparative Example 2 50 parts by weight of cellulose triacetate having an acetylation degree of 61.0% and a viscosity-average degree of polymerization of 350 was changed to 100 parts by weight, and 368 parts by weight of methylene chloride was changed to 320 parts by weight. In the same manner as in Example 1, except that 24 parts by weight of ethanol was changed to 60 parts by weight and further to 20 parts by weight of 1-butanol, a mixed organic solvent was used.
A 0 μm cellulose triacetate film was obtained. The amount of residual solvent in the film was 0.9%. Example 7 50 parts by weight of cellulose triacetate having an acetylation degree of 60.0% and a viscosity average polymerization degree of 200, and an acetylation degree of 60.0%
And 50 parts by weight of cellulose triacetate having a viscosity average degree of polymerization of 350 and 10 parts by weight of triphenyl phosphate were mixed with a mixed organic solvent of 637 parts by weight of methyl acetate and 33 parts by weight of ethanol to form a mixture. At room temperature, the cellulose triacetate was in a swollen state. Next, the mixture was placed in a container having a double structure, and the mixture was slowly stirred and H was controlled at −75 ° C. as a refrigerant in the outer jacket.
FE-7100 (manufactured by Sumitomo 3M Limited) was introduced. This allowed the mixture in the inner vessel to cool to -70 ° C. Cooling was continued for 30 minutes to dissolve the mixture until the mixture was uniformly cooled, then the refrigerant in the jacket outside the vessel was evacuated and warm water was instead introduced into the jacket. Subsequently, the content was stirred, the temperature was raised to 30 ° C. over 40 minutes, and stirring was continued for another 20 minutes. This series of cooling and heating operations was repeated three times to obtain a transparent dope. The dope was allowed to stand at 30 ° C. overnight and subjected to a defoaming operation. After that, the dope was subjected to Azumi Filter Paper No. After filtration using 244, the mixture was subjected to film formation.

The obtained dope was fed to a die by a constant-quantity gear pump, and cast on a rotating stainless steel belt so that the film thickness after drying became 120 μm. 50 ° C from the back
The first half of drying was performed on a belt whose temperature was controlled by contacting the same with warm water, and the second half was dried by blowing dry air at 90 ° C. to dry the web. The web is peeled off from the belt when the belt makes one round, and both ends of the web are gripped with clips to remove the web.
5 minutes at 140 ° C., then 20 minutes at 140 ° C.
After drying for a minute, a cellulose triacetate film having a thickness of 120 μm was finally obtained. At each level, the residual solvent amount of the film was 0.8%.

Comparative Example 3 Cellulose triacetate 5 having a viscosity average degree of polymerization of 200
A cellulose triacetate film having a film thickness of 120 μm was obtained in the same manner as in Example 7, except that 0 part by weight was changed to 300, the viscosity average degree of polymerization was set to 300, and 50 parts by weight was changed to 100 parts by weight. The amount of residual solvent in the film is 0.
8%.

Example 8 A cellulose triacetate film having a thickness of 120 μm was obtained in the same manner as in Example 7 except that 637 parts by weight of methyl acetate was changed to 350 parts by weight, and 33 parts by weight of ethanol was changed to 150 parts by weight of acetone. . The residual solvent amount of the obtained cellulose triacetate film was 0.8% by weight.

Comparative Example 4 50 parts by weight of cellulose triacetate having a degree of acetylation of 60.0% and a viscosity average degree of polymerization of 200 were mixed with a viscosity average degree of polymerization of 30.
0, and the same lot as in Example 7, except that the lot was changed from 50 parts by weight to 100 parts by weight.
Was obtained as a cellulose triacetate film. The residual solvent content of the film was 0.8%.

Example 9 50 parts by weight of cellulose triacetate having an acetylation degree of 60.0% and a viscosity average polymerization degree of 200, and an acetylation degree of 60.0%
And 50 parts by weight of cellulose triacetate having a viscosity average polymerization degree of 350 and 10 parts by weight of triphenyl phosphate as a plasticizer were mixed with 670 parts by weight of acetone to form a mixture. At room temperature, the cellulose triacetate was in a swollen state. The mixture was transferred to a pressurized sealed container, and gradually pressurized to a final pressure of 500 kgf / cm ² . After holding for 30 minutes as it was, the pressure was released, and the mixture was further held at normal pressure for 30 minutes. Thereafter, stirring was performed for 30 minutes to obtain a transparent dope. The dope was allowed to stand at 30 ° C. overnight and subjected to a defoaming operation. After that, the dope was subjected to Azumi Filter Paper No. After filtration using 244, the mixture was subjected to film formation.

The obtained dope was fed to a die with a constant-rate gear pump, and was cast on a rotating stainless steel belt so that the film thickness after drying was 120 μm. 50 ° C from the back
The first half of drying was performed on a belt whose temperature was controlled by contacting the same with warm water, and the second half was dried by blowing dry air at 90 ° C. to dry the web. The web is peeled off from the belt when the belt makes one round, and both ends of the web are gripped with clips to remove the web.
5 minutes at 140 ° C., then 20 minutes at 140 ° C.
After drying for a minute, a cellulose triacetate film having a thickness of 120 μm was finally obtained. At each level, the residual solvent amount of the film was 0.8%.

Comparative Example 5 Cellulose triacetate 5 having a viscosity average degree of polymerization of 200
A cellulose triacetate film having a thickness of 120 μm was obtained in the same manner as in Example 9 except that the viscosity average polymerization degree was changed from 0 part by weight to 300, and from 50 parts by weight to 100 parts by weight in one lot. The amount of residual solvent in the film is 0.
8%.

Table 1 shows the results of the test.

[0111]

[Table 1]

As is evident from Table 1, the cellulose triacetate solution prepared according to the present invention has a reduced solution viscosity as compared to the solution prepared according to the comparative example.
The flatness of the obtained film is improved. In addition, it can be seen that the cellulose triacetate film obtained in the present invention has a mechanical strength, a haze, a tear strength, a tensile strength, an elastic modulus, and a fold resistance that are comparable or better.

[0113]

EFFECT OF THE INVENTION A cellulose triacetate film having excellent flatness, transparency and mechanical strength is obtained by mixing the viscosity of a cellulose triacetate solution (dope) with a low-viscosity cellulose triacetate and a high-viscosity cellulose triacetate. Can be provided.

Further, the cellulose triacetate film obtained by the present invention is useful for a silver halide photographic material or a liquid crystal image display device from the above-mentioned characteristics.

Claims (10)

[Claims] 1. A plurality of lots having an average acetylation degree of 59.0 to 62.5% and a viscosity average degree of polymerization in the range of 150 to 550, wherein the difference in viscosity average degree of polymerization is 50 to 300. 20/80 to 80/20 by weight ratio of two lots
A cellulose triacetate film produced by dissolving the cellulose triacetate mixed in (1) in an organic solvent to prepare a dope and a solution casting film forming step. 2. The method for producing a cellulose triacetate film according to claim 1, wherein the concentration of the cellulose triacetate in the dope is 10 to 35% by weight. 3. The method for producing a cellulose triacetate film according to claim 1, wherein the dope contains 5 to 30% by weight of a plasticizer based on the cellulose triacetate. 4. The organic solvent comprises 75 to 98% by weight of methylene chloride and 2 to 25% by weight of 1 to 6 carbon atoms.
2. The composition according to claim 1, wherein said alcohol is contained.
4. The method for producing a cellulose triacetate film according to any one of items 3 to 3. 5. The method according to claim 1, wherein the organic solvent comprises 75 to 87% by weight of methylene chloride and 13 to 25% by weight of carbon atoms having 1 to 1%.
The method for producing a cellulose triacetate film according to claim 4, wherein the method further comprises the alcohol of (6). 6. The organic solvent according to claim 1, wherein the organic solvent contains at least one selected from acetone, methyl acetate, and ethyl formate in an amount of 60% by weight or more. A method for producing a cellulose triacetate film. 7. The method according to claim 1, wherein the organic solvent is at least one selected from 60 to 95% by weight of methyl acetate and ethyl formate.
The method for producing a cellulose triacetate film according to claim 6, comprising about 40% by weight of acetone. 8. The step of preparing a dope comprises: adding a mixture obtained by adding cellulose triacetate to an organic solvent to -100 to
Cooling to −10 ° C .;
Heating the cellulose triacetate to 0 ° C. to dissolve the cellulose triacetate, the method for producing a cellulose triacetate film according to claim 1. 9. The step of preparing a dope comprises: adding a mixture obtained by adding cellulose triacetate to an organic solvent to 50 to 40.
8. The method according to claim 1, further comprising a step of maintaining the mixture under a pressure of 00 kgf / cm < ² > and a step of continuously maintaining the pressurized mixture under a pressure of 0.1 to 10 kgf / cm < ² >. 4. The method for producing a cellulose triacetate film according to claim 1. 10. A cellulose triacetate film produced by the method according to claim 1. Description: