JP3976036B2 - Method for producing polymer film - Google Patents

Description

  The present invention relates to a method for producing a polymer film by a so-called casting film forming method.

  A casting film forming method is known as a method for producing a polymer film. The casting film forming method includes a step of forming a coating film containing the polymer compound on the support by applying a solution obtained by dissolving the polymer compound in a solvent onto the support, And a step of drying the coating film. The casting film forming method is widely implemented on various scales from a laboratory scale to an industrial scale (Patent Documents 1 to 4).

  When the cast film forming method is performed on an industrial scale, a mirror-polished metal roll or a so-called endless belt is used as a support (Patent Documents 5 to 7). The method using a metal belt as a support is widely used in the casting film forming method because it is easy to lengthen the drying process length after coating. In order to increase the productivity of the casting film forming method, it is effective to increase the drying speed. To that end, it is conceivable to take measures such as increasing the drying temperature and increasing the amount of drying air. However, if the drying temperature is too high, the volatilization rate of the solvent at the time of drying may increase so that bubbles may be generated. Further, if the amount of drying air is excessively increased, wind-like wrinkles may be generated on the surface of the coating film, or undulation of the entire coating film may be generated due to vibration caused by the wind of the support belt itself. Thus, the above-mentioned means are not necessarily effective from the viewpoint of the quality of the obtained film.

Thus, since it was difficult to improve both productivity and film quality in the casting film forming method, conventionally, when producing a high-quality film, the drying speed is reduced, in other words, I had to dry it slowly over a long period of time.
JP 2003-260715 A Japanese Patent Laid-Open No. 5-237928 JP-A-6-56992 Japanese National Patent Publication No. 11-504369 JP-A-9-207151 JP-A-9-29852 Japanese Patent Laid-Open No. 9-57772

  However, a drying process that takes a long time not only reduces productivity, but also causes another problem of causing unwanted side reactions during drying. In particular, as in the case of the production of a polyimide film, when the precursor film (film containing polyamic acid) obtained by the casting film forming method needs to be further heat-treated to form a film, the above-mentioned another problem becomes serious. Become. This is because the precursor (compound) of the precursor film does not necessarily have high chemical stability. For example, since the polyamic acid of the polyamic acid film that is a precursor of the polyimide film is likely to be hydrolyzed, the volatilization of the solvent and the molecular weight reduction due to the hydrolysis of the polyamic acid occur simultaneously in the drying step. Therefore, when a polyamic acid film is obtained and dried for a long time, the molecular weight of the finally obtained polyimide is lowered, which causes the mechanical strength to be lowered.

  The present invention provides a casting film-forming method capable of producing a high-quality film with high productivity, in particular, mechanical characteristics and electrical characteristics associated with a decrease in molecular weight when applied to the formation of a polyimide film precursor. It aims at providing the casting film forming method which can prevent deterioration.

As a result of intensive studies, the present inventors have completed the following invention.
(1) forming a coating film containing the polymer compound on the support by applying a solution containing the polymer compound having an imide bond or an amide bond in the main chain on the support; and on the support And a step of drying the coating film under a condition that the atmospheric temperature on the lower side of the coating film is higher by 10 to 50 ° C. than the atmospheric temperature on the upper side of the coating film.
(2) the polymer compound is a polyimide precursor, the (1) Symbol placement method for producing a polymer film.
( 3 ) The method for producing a polymer film according to (1) or (2) , wherein the polymer compound contained in the solution has a benzazole ring in the main chain.
( 4 ) The polymer film according to any one of (1) to ( 3 ), wherein the support is composed of an organic polymer film having a tensile elastic modulus of 3 GPa or more in both the longitudinal direction and the width direction. Manufacturing method.

  The method for producing a polymer film of the present invention can suppress film quality problems such as generation of bubbles during the drying process in casting and can finish drying in a short time. For this reason, the side reaction at the time of drying feared by long-time drying can be suppressed to the minimum.

  The production method of the present invention is a method for producing a polymer film by a casting film formation method characterized by temperature control during the drying process. The casting film forming method includes a step of forming a coating film containing the polymer compound on the support by applying a solution containing the polymer compound on the support, and drying the coating film on the support. A process for producing a polymer film.

  In the present invention, the step of forming a coating film containing a polymer compound on the support may be performed by applying a solution containing the polymer compound on the support. It can be taken in as appropriate.

  As the application method, squeegee coating, bar coating, comma coating, reverse coating, continuous screen printing, gravure coating, etc., can be used as appropriate depending on the viscosity of the solution, the thickness of the film to be obtained, and the thickness accuracy. Good.

  The support on which the solution containing the polymer compound is applied is not particularly limited, such as a belt or a drum, and is preferably an endless belt made of a bendable material having a thickness of 5 mm or less, preferably 3 mm or less, more preferably 1 mm or less. It is. If the thickness of the support is too thick, there may be a difficulty in curving. The width and length of the support are not particularly limited, and the width is preferably 30 cm or more, more preferably 50 to 200 cm, and the length is preferably 100 cm or more, more preferably 300 to 5000 cm. When the support is an endless belt, the “length of the support” is the length of one end of the endless belt.

  The material of the support used in the present invention is not particularly limited as long as it is a material that does not cause significant deformation or dimensional change at the drying temperature of the polymer to be formed into a film, regardless of whether it is metal or nonmetal. Examples of the metal material include iron, stainless steel (SUS), nickel, titanium, tantalum, copper, and hastelloy. Further, the surface of the belt may be subjected to plating or surface treatment with chrome, gold, silver, nickel, or the like, if necessary, in order to improve corrosion resistance, hardness, decrease adhesiveness, or the like. Examples of surface treatments include chromium thin film hydrated oxide film formation, silicone or fluorine film formation.

  Hereinafter, the aspect in case a support body is an organic polymer film is described in detail. An organic polymer film is a film containing an organic polymer as a main component. The organic polymer is not particularly limited, and specific examples include polyester resins, polyimide resins, polyphenylene oxide resins, polyphenylene sulfide resins, polysulfone resins, and the like. Examples of the polyester resin include polyethylene terephthalate, polyethylene naphthalate, polypropylene terephthalate, polybutylene terephthalate, and polypropylene naphthalate. These may be used alone or in combination of two or more. These polyester resins may be copolymerized with other dicarboxylic acid components or diol components. The support used in the present invention may be a laminate of different organic resin films. The support is preferably made of a polyester film, more preferably a polyethylene terephthalate film, because it is excellent in heat resistance, inexpensive, easy to process, and excellent in chemical resistance.

  The thickness of the organic polymer film used as a support in the present invention is preferably 3 to 300 μm. When the organic polymer film is thicker than 300 μm, it is difficult to handle, and when it is thinner than 3 μm, wrinkles are likely to occur during the casting film forming method. Considering dimensional stability and strength, the thickness of the organic polymer film is more preferably 10 μm or more, and further preferably 20 μm or more.

  The center line average roughness (Ra) of the organic polymer film used as a support in the present invention is preferably 0.1 to 1.0 nm. When Ra is within the above range, the polymer film obtained by the production method of the present invention has a high quality with few undesirable irregularities. The method for measuring Ra is described in the column of Examples.

  The tensile modulus of the organic polymer film used as the support in the present invention is 3 GPa or more, preferably 4 GPa or more, in both the longitudinal direction and the width direction. When the tensile elastic modulus is less than 3 GPa, the organic polymer film is deformed at the time of transportation because of inferior dimensional stability, and the resulting polymer film may be curled, sagging, or wrinkled. The upper limit of the tensile elastic modulus is not particularly defined, but 20 GPa and the like can be mentioned in consideration of ease of handling as a support and availability. The method for measuring the tensile modulus is described in the column of Examples.

  The linear expansion coefficient of the organic polymer film used as a support in the present invention is preferably 2 to 30 ppm / ° C in both the longitudinal direction and the width direction. If the organic resin film exhibits a linear expansion coefficient within the above range, the dimensional change due to heating for drying is small, so that the polymer film obtained by the production method of the present invention is less likely to curl, sag, wrinkle, etc. . The linear expansion coefficient is more preferably 2 to 25 ppm / ° C. The method for measuring the linear expansion coefficient is described in the column of Examples.

  Organic resin films exhibiting the above-described physical properties are known. Such an organic resin film is used as an optical film belonging to a technical field completely different from the casting film forming method. Examples of the commercially available film that can be used as a support in the present invention include Cosmo Shine A4100 (manufactured by Toyobo Co., Ltd.), which is an optical polyethylene terephthalate film.

  The polymer compound contained in the solution to be coated on the support is not particularly limited as long as it is a polymer compound that forms a film through a drying process. Specific examples of the polymer compound contained in the solution coated on the support include a polymer compound having an imide bond or an amide bond in the main chain, such as polyamide imide, polyimide precursor, polyimide soluble in a solvent, and cellulose acetate. , Polycarbonate, polyvinyl chloride, and aramids. The polyimide precursor is a compound that can be converted into polyimide by a treatment such as heating, and is typically polyamic acid. Preferably, the polymer compound has a benzazole ring in the main chain. The benzazole ring is a condensed ring of an azole ring and a benzene ring, and the azole ring is preferably an oxazole ring, a thiazole ring, or an imidazole ring. Particularly preferably, the polymer compound is a polyimide benzoxazole precursor, in other words, a polyamic acid having a benzoxazole ring in the main chain.

  The solvent for preparing the polymer compound solution used in the present invention is not particularly limited, and a solvent used in the conventional casting film forming method may be appropriately used. Specific examples of the solvent include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, methylene chloride, tetrahydrofuran, methanol, metacresol and the like.

  As a specific guideline for selecting a solvent, a guideline for selecting a solvent that dissolves the polymer compound and does not dissolve the support is general. Preferable examples of the solution containing the polymer compound include N-methyl-2-pyrrolidone solution and N, N-dimethylacetamide solution of polyamideimide, N-methyl-2-pyrrolidone solution of polyamic acid (polyimide precursor), N , N-dimethylformamide and N, N-dimethylacetamide solution, N-methyl-2-pyrrolidone solution and N, N-dimethylacetamide solution of polyimide soluble in solvent, methylene chloride solution and methanol solution of cellulose acetate, polycarbonate Examples include a methylene chloride solution and a metacresol solution, a tetrahydrofuran solution of polyvinyl chloride, and an N-methyl-2-pyrrolidone solution of aramids.

  Among them, the production method of the present invention is preferably applied to a solution of polyamic acid N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide or the like, which is a precursor of polyimide benzoxazole. . Hereinafter, means for obtaining a solution containing polyamic acid which is a precursor of polyimide benzoxazole will be described in detail. However, the production method of the present invention can be applied to the production of films containing the following polymers.

  In this embodiment, an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid anhydride are subjected to a ring-opening polyaddition reaction in a solvent in order to prepare a polymer solution to be coated on a support. . The polymer solution (polyamic acid solution) thus obtained is applied onto a support and dried, and then further subjected to dehydration condensation (imidization) to obtain a polyimide film.

<Aromatic diamines>
Specific examples of the aromatic diamine having a benzoxazole structure used in the present invention include the following.

  Among these, from the viewpoint of easy synthesis, each isomer of amino (aminophenyl) benzoxazole is preferable, and 5-amino-2- (p-aminophenyl) benzoxazole is more preferable. Here, “each isomer” refers to each isomer in which two amino groups of amino (aminophenyl) benzoxazole are determined according to the coordination position (eg, the above “formula 1” to “formula 4”). Each compound described in the above. These diamines may be used alone or in combination of two or more.

  In the present invention, one or two or more diamines having no benzoxazole structure exemplified below may be used as long as they are 30 mol% or less of the total diamine. Examples of such diamines include 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, and bis [4- (3-aminophenoxy) phenyl]. Sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 3,3′-diamino Diphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-dia Nodiphenyl sulfide, 3,3′-diaminodiphenyl sulfoxide, 3,4′-diaminodiphenyl sulfoxide, 4,4′-diaminodiphenyl sulfoxide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4 , 4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4, 4′-diaminodiphenylmethane, bis [4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (4-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-amino) Phenoxy) phenyl] ethane, 1,1-bis [4- 4-aminophenoxy) phenyl] propane, 1,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, , 4-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] Butane, 2- [4- (4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-amino) Nophenoxy) -3-methylphenyl] propane, 2- [4- (4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2- Bis [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexa Fluoropropane, 1,4-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4 -Aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenyl) Noxy) phenyl] sulfoxide, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1, 3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] Benzene, 4,4′-bis [(3-aminophenoxy) benzoyl] benzene, 1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [4- (3-aminophenoxy) ) Phenyl] propane, 3,4'-diaminodiphenyl sulfide, 2,2-bis [3- (3-aminophenoxy) phenyl] 1,1,1,3,3,3-hexafluoropropane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1, 2-bis [4- (3-aminophenoxy) phenyl] ethane, bis [4- (3-aminophenoxy) phenyl] sulfoxide, 4,4′-bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4 , 4′-bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [ 4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- {4- (4-aminophenoxy) phenoxy} pheny ] Sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl Benzene, 1,3-bis [4- (4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-fluorophenoxy) ) -Α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4- Amino-6-cyanophenoxy) -α, α-dimethylbenzyl] benzene, 3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxy Benzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4 -Phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3, 4,4′-diamino-4,5′-dibiphenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4′-diamino-4- Biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3-amino-4-phenoxybenzoyl) benzene, 1,3-bis (4-amino-5-phenoxybenzoyl) benzene 1,4-bis (4-amino-5-phenoxybenzoyl) benzene, 1,3-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,4-bis (3-amino-4-biphenoxy) Benzoyl) benzene, 1,3-bis (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-amino-5-biphenoxybenzoyl) benzene, 2,6-bis [4- (4 -Amino-α, α-dimethylbenzyl) phenoxy] benzonitrile and some or all of the hydrogen atoms on the aromatic ring of the aromatic diamine are halogen atoms, carbon Substitution with a C1-C3 halogenated alkyl group or alkoxyl group in which some or all of the hydrogen atoms of the prime alkyl group, alkoxyl group, cyano group, alkyl group or alkoxyl group are substituted with halogen atoms Aromatic diamines made and the like.

<Aromatic tetracarboxylic acid anhydrides>
The tetracarboxylic acid anhydrides used in the present invention are aromatic tetracarboxylic acid anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

  These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are 30 mol% or less of the total tetracarboxylic dianhydrides. Examples of such tetracarboxylic acid anhydrides include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3 5,6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3 -(1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane-1 -(2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ', 4'-tetracarboxylic dianhydride, bicyclo [2.2.1] heptane -2,3,5,6-tetracarboxylic dianhydride, Cyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic acid A dianhydride etc. are mentioned. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  The solvent used when polymerizing diamines and tetracarboxylic acid anhydrides to obtain a polyamic acid dissolves both the raw material monomer and the polyamic acid to be produced, and a support described later. Is not particularly limited, but is preferably a polar organic solvent, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, Examples thereof include N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and halogenated phenols. These solvents can be used alone or in combination. The amount of the solvent used may be an amount sufficient to dissolve the monomer as a raw material. As a specific amount used, the weight of the monomer in the solution in which the monomer is dissolved is usually 5 to 40% by weight, The amount is preferably 10 to 30% by weight.

  Conventionally known conditions may be applied for the polymerization reaction for obtaining the polyamic acid (hereinafter also simply referred to as “polymerization reaction”). As a specific example, in a temperature range of 0 to 80 ° C., 10 Stirring and / or mixing continuously for minutes to 30 hours. If necessary, the polymerization reaction may be divided or the temperature may be increased or decreased. In this case, the order of adding both monomers is not particularly limited, but it is preferable to add aromatic tetracarboxylic acid anhydrides to the solution of aromatic diamines. The weight of the polyamic acid in the polyamic acid solution obtained by the polymerization reaction is preferably 5 to 40% by weight, more preferably 10 to 30% by weight, and the viscosity of the solution is measured with a Brookfield viscometer (25 ° C.). From the viewpoint of the stability of liquid feeding, it is preferably 10 to 2000 Pa · s, and more preferably 100 to 1000 Pa · s.

  Next, the process of drying the coating film formed on the support will be described. In the production method of the present invention, the coating film is dried under the condition that the atmospheric temperature below the coating film is higher by 1 to 55 ° C. than the atmospheric temperature above the coating film on the support. In the description of the atmospheric temperature, the direction is defined with the direction from the coating film toward the support being the downward direction and the opposite being the upward direction. Such a description in the vertical direction is made for concisely expressing the position of the region to be noted, and is not for specifying the absolute direction of the coating film in actual production.

The “atmosphere temperature above the coating film” is a temperature in a region (usually a space) from directly above the coating film to 30 mm above the coating film, and a temperature at a position 5 to 30 mm away from the coating film in the upward direction. By measuring with a thermocouple or the like, the ambient temperature above the coating film can be determined.
The “atmosphere temperature under the coating film” is a temperature in a region (often including the support and the lower part of the support) from directly below the coating (support part) to 30 mm below the coating film. Yes, the temperature of the lower side of the coating film can be determined by measuring the temperature at a position 5 to 30 mm below the coating film with a thermocouple or the like.

  When drying, if the atmospheric temperature on the lower side of the coating film is higher by 1 to 55 ° C. than the atmospheric temperature on the upper side of the coating film, a high quality film can be obtained even if the drying temperature itself is increased to increase the drying speed of the coating film Can be obtained. If the ambient temperature below the coating is lower than the ambient temperature above the coating, or if the difference between the ambient temperature above the coating and the ambient temperature below the coating is less than 1 ° C. The upper surface of the membrane is first dried and turned into a film to become a “lid”, and then the evaporation of the solvent to be evaporated from the vicinity of the support is prevented, and an undesirable hole is opened in the film. There is a concern that the surface becomes rough. It is undesirable for the apparatus and the economy to be disadvantageous in that the ambient temperature below the coating film is higher than the ambient temperature above the coating film and the temperature difference is greater than 55 ° C. When the temperature difference is further increased, the film surface may be roughened. Preferably, at the time of drying, the atmospheric temperature on the lower side of the coating film is made higher by 10 to 50 ° C., more preferably 15 to 45 ° C. than the atmospheric temperature on the upper side of the coating film.

  The setting of the atmospheric temperature as described above may be performed throughout the entire drying process of the coating film, or may be performed in a part of the drying process of the coating film. When the coating film is dried by a continuous dryer such as a tunnel furnace, the above-mentioned atmospheric temperature may be set in the drying effective length, preferably 10 to 100%, more preferably 15 to 100%. .

  Conventionally, the drying temperature is the same on the upper and lower sides of the coating film. Conventional heating means can be used as the means for realizing the temperature control as described above, and specific examples of such means include infrared heating, hot air heating, and microwave heating.

  In the case where the polymer film produced by the production method of the present invention is a polyimide film, a film containing a polyimide precursor is obtained by the above-described drying, so that the polyimide film is obtained by imidizing the polyimide precursor. Can do. About imidation, a well-known technique can be used suitably and can be implemented.

  In the present invention, the atmospheric temperature itself in drying the coating film can be appropriately determined depending on the type of the polymer solution. In the production method of the present invention, a film of good quality can be obtained even if the drying rate is increased by drying at a higher temperature than before. For example, when manufacturing the film containing the polyamic acid which is a precursor of a polyimide, the atmospheric temperature under the coating film in drying of a coating film becomes like this. Preferably it is 80-140 degreeC, More preferably, it is 90-120 degreeC It is.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by a following example. In addition, the evaluation method of the physical property in the following examples is as follows.

1. Reduced viscosity of polyamic acid (ηsp / C)
A solution dissolved in N-methyl-2-pyrrolidone so that the polymer concentration was 0.2 g / dl was measured at 30 ° C. using an Ubbelohde type viscosity tube.

2. Film thickness Measured using a micrometer (Finereuf, Millitron 1245D).

3. Tensile modulus, tensile breaking strength and tensile breaking elongation of the film The film to be measured was cut into strips of 100 mm × 10 mm in the longitudinal direction (MD direction) and the width direction (TD direction), respectively, as test pieces. . Using a tensile tester (manufactured by Shimadzu Corp., Autograph (R) model name AG-5000A) under the conditions of a tensile speed of 50 mm / min and a distance between chucks of 40 mm, the tensile modulus and tensile strength in each of the MD and TD directions. And tensile elongation at break was measured.

4). The melting point of the film and the glass transition temperature The film to be measured was subjected to differential scanning calorimetry (DSC) under the following conditions, and the melting point (melting peak temperature Tpm) and the glass transition point (Tmg) were determined according to JIS K 7121. .
Device name: DSC3100S manufactured by MAC Science
Pan ： Aluminum pan (non-airtight)
Sample weight; 4mg
Temperature rising start temperature: 30 ° C
Temperature rising end temperature: 600 ° C
Temperature increase rate: 20 ° C / min
Atmosphere: Argon

5). Atmospheric temperature during drying The following thermocouple detectors were installed at positions 5 mm away from the upper and lower surfaces of the support. The thermocouple was provided near the center in the width direction. In the drying zone, the support was transported at the same drying speed (drying time) as in the actual coating-drying process, and the detected temperature in each zone at that time was recorded.
Thermocouple: K thermocouple (φ; 1.0mm, length 12m)
Data capture device: NR-250 manufactured by Keyence Corporation

6). Film quality (bubbles)
The presence or absence of bubbles near the film surface was confirmed visually.

7). Centerline average roughness of support (Ra)
Ra was measured in a range of 133.1 μm × 133.1 μm using a three-dimensional non-contact surface shape measurement system manufactured by Micromap.

8). Film linear expansion coefficient (CTE)
For the film to be measured, the stretch rate in the MD direction TD direction is measured under the following conditions, and the stretch rate / temperature at intervals of 30 ° C. to 40 ° C., 40 ° C. to 50 ° C.,. Measurement was performed up to 100 ° C., and an average value of all measured values was calculated as CTE.
Device name: TMA4000S manufactured by MAC Science
Sample length; 20mm
Sample width: 2 mm
Temperature rising start temperature: 30 ° C
Temperature rise end temperature: 100 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Argon

Example 1
(Preparation of polyamic acid solution)
The inside of a reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod was purged with nitrogen, and then 500 parts by weight of 5-amino-2- (p-aminophenyl) benzoxazole was added. Next, 5000 parts by weight of N-methyl-2-pyrrolidone was added and completely dissolved, and then 485 parts by weight of pyromellitic dianhydride was added and stirred at 25 ° C. for 48 hours. A polyamic acid solution was obtained. This reduced viscosity (ηsp / C) was 4.5.

(Manufacture of polyamic acid film)
The obtained polyamic acid solution was coated on a mirror-finished (surface roughness Ra: 0.5 nm) endless stainless steel belt using a squeegee (squeegee / belt gap was 650 μm). It dried on the conditions of Table 1 using the continuous-type drying furnace which has three zones. In Table 1, “on the zone” means the ambient temperature above the coating film, and “under the zone” means the ambient temperature below the coating film. The self-supporting polyamic acid film obtained by drying was peeled off from the support. In this way, a polyamic acid film having a width of 650 mm, a length of 60 m, and a thickness of 40 μm was obtained.

(Manufacture of polyimide film)
The obtained polyamic acid film was passed through a continuous heat treatment furnace and subjected to two stages of heat treatment under the conditions shown in Table 1 to advance the imidization reaction. Then, it cooled to room temperature in 5 minutes, and obtained the polyimide film which exhibits brown. The physical properties of the obtained film are shown in Table 3. In the column of “Heat treatment conditions” in Table 1, for example, “200 ° C. × 5 min → 450 ° C. × 5 min” means that the film peeled off from the support was treated at 200 ° C. for 5 minutes and then at 450 ° C. It means processing for 5 minutes.

(Example 2)
A polyimide film was obtained in the same manner as in Example 1 except that the drying conditions for obtaining the polyamic acid film were changed to the conditions shown in Table 1.

(Example 3)
480 parts by weight of pyromellitic anhydride and 480 parts by weight of 4,4′-dicyanodiphenyl ether were dissolved in 5000 parts by weight of dimethylacetamide and stirred for 48 hours while maintaining the temperature at 20 ° C. or lower. An acid solution was obtained. The reduced viscosity (ηsp / C) of the obtained solution was 4.5. A polyimide film was obtained in the same manner as in Example 1 except that this polyamic acid solution was used.

Example 4
Polyamideimide obtained by reacting 0.25 mol of 2,4-tolylene diisocyanate and 0.75 mol of o-tolidine diisocyanate with 1 mol of trimellitic anhydride instead of the above polyamic acid solution. An n-methyl-2-pyrrolidone solution containing 20 wt% resin was used. In other respects, a polyamideimide film was obtained according to the conditions described in Table 1 according to the procedure of Example 1.

(Example 5)
In the drying step, a polyester film Cosmo Shine A-4100 (manufactured by Toyobo Co., Ltd.) was used as a support instead of the stainless steel belt. The polyester film has a linear expansion coefficient in the longitudinal direction of 20 ppm / ° C., a linear expansion coefficient in the width direction of 18 ppm / ° C., Ra of 0.5 nm, and a tensile modulus in the longitudinal direction of 4.1 GPa. The tensile modulus in the width direction is 4.2 GPa. A polyamic acid solution was applied to the non-lubricating surface of the polyester film. Unlike the case of the endless stainless steel belt, the polyester film unwinding device and the winding device were installed in a dryer. A polyimide film was produced in the same manner as in Example 1 except for the above conditions.

(Comparative Examples 1-3)
A polyimide film was obtained in the same manner as in Example 1 except that the drying conditions for obtaining the polyamic acid film were changed to the conditions shown in Table 2.

(Comparative Example 4)
Using the same polyester film as in Example 5 as a support, a polyimide film was obtained under the conditions described in Table 2. Table 4 summarizes the physical properties of the polyimide films obtained in Comparative Examples 1 to 4.

  As is clear from the table below, in the examples of the present invention, films having excellent mechanical strength and quality can be obtained, while in the comparative examples, the mechanical strength is low and the quality is deteriorated such that bubbles are generated. Was also recognized.

Claims (4)

Forming a coating film containing the polymer compound on the support by applying a solution containing the polymer compound having an imide bond or an amide bond in the main chain on the support; and a coating film on the support. And a step of drying the coating film under a condition in which the atmospheric temperature below the coating film is higher by 10 to 50 ° C. than the upper atmosphere temperature. The polymer compound is a polyimide precursor, the production method of the polymer film of claim 1 Symbol placement. The method for producing a polymer film according to claim 1 or 2 , wherein the polymer compound contained in the solution has a benzazole ring in the main chain. The method for producing a polymer film according to any one of claims 1 to 3 , wherein the support is made of an organic polymer film having a tensile elastic modulus of 3 GPa or more in both the longitudinal direction and the width direction.