JP2005313364A - Isotropic polyimide film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily manufacturing an isotropic polyimide film, especially a polyimide film isotropic over the whole width of the film. <P>SOLUTION: The manufacturing method of the continuously produced polyimide film has a step for feeding a gel film of polyamic acid through a heating furnace while fixing both ends thereof. This step includes a step for fixing and feeding the gel film so that the tension in the width direction (TD direction) of the film becomes substantially zero and a step for stretching the film in the TD direction and the heating furnace is composed of a plurality of at least two heating furnaces and the temperature irregularity in the width direction in the first heating furnace is set to 100°C or below. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing an isotropic polyimide film in which the degree of molecular orientation of the polyimide film is very small. More specifically, the present invention relates to a novel method for producing an isotropic polyimide film having a very small molecular orientation in the entire width of a continuously produced polyimide film.

  For example, in the technical field of electronics, lightweight and simple electronic devices have been put to practical use, and there is an increasing demand for light weight and high functionality for members used for electronic devices. In particular, there is an increasing demand for small and highly functional electric and electronic equipment typified by mobile phones.

  In particular, in the technical field using a flexible printed wiring board (hereinafter referred to as FPC) used for a substrate of an electronic member or high-density wiring, it is lightweight and highly functional (in the case of FPC, it means that high-density mounting is possible). The demand is getting higher.

  At present, a polyimide film is widely used for FPC as a material excellent in high insulation, high heat resistance, flexibility, low thermal expansion coefficient, high elastic modulus, and sliding flexibility. Furthermore, polyimide films are widely used for TAB (Tape Automated Bonding) films, COF (chip on film) substrates, and the like.

  However, it is necessary to advance the imidization reaction at a high temperature during the production of the polyimide film. For this reason, a tenter furnace that transports the inside of a high-temperature heating furnace while holding the end of the film having a self-supporting property by drying. It is a general manufacturing method that is manufactured using a method of baking, and in that case the problem is that the film physical property value at the edge of the film, which is called the bowing phenomenon, varies greatly depending on the direction (in terms of molecular orientation) When the anisotropy is expressed, the following) is expressed, and there is a problem that the film at the site cannot be used. Therefore, a polyimide film having a small difference in physical property values depending on the direction of the full width film (the molecular orientation is called isotropic) has been desired.

  As a method for solving the above bowing phenomenon and obtaining an isotropic polyimide film, there are 1) a method using stretching, 2) a method for controlling the heating furnace temperature, 3) a method for controlling the film width in the tenter furnace, etc. Has been used effectively.

  As a method using stretching, Patent Document 1 and Patent Document 2 have a self-supporting property by casting an organic solvent solution of a polyamic acid containing a ring-closing catalyst and a dehydrating agent on the surface of the support and imidizing the polyamic acid. A gel film continuum having a solid content of 5 to 50% by weight is formed, the gel film is stretched 1.1 to 1.9 times in the running direction, and the draw ratio in the running direction is 0.9 to 1.3 in the width direction. Although an isometric polyimide film production method characterized by stretching at a double magnification is described, a large-scale apparatus for stretching is required, and it is difficult to adapt easily.

  As a method for controlling the heating furnace temperature, for example, in Patent Document 3, when both ends of a green sheet (gel film) are fixed and passed through the heating furnace, the orientation axis angles at both ends of the raw film are positive. A method is disclosed in which the film determines the temperature conditions in the furnace depending on whether it is negative or negative. In Patent Document 4, a gel film, which is a precursor of a polyimide film, is transported and fired by a tenter method to a heating furnace whose heating start temperature is controlled to a support temperature + 100 ° C. or lower and 150 to 250 ° C. A method for continuously producing an isotropic polyimide film is described.

  Furthermore, as a method for controlling the film width in the tenter furnace, for example, Patent Document 5 discloses that a resin solution obtained by dissolving a polyamic acid or polyimide as a polyimide precursor in an organic solvent solution is continuously applied onto an endless belt or drum. The polyimide film has a glass transition point in the method for producing a polyimide film, which is applied to the substrate and dried until self-supporting property is obtained, and then fixed at both ends of the film and conveyed in a heating furnace. The maximum temperature of the heating furnace is equal to or higher than the glass transition temperature, the distance between the fixed ends is set so that the film width is gradually reduced in the first half of the heating furnace, and the fixed end is set so that the film width is gradually increased in the latter half of the heating furnace. A method for setting an inter-distance is disclosed.

Although the methods of Patent Documents 3 to 5 are all effective methods for obtaining an isotropic film, the method of defining the fixed state of the film in the heating furnace and the temperature spots of the heating furnace according to the present invention, The approach is different.
JP-A-5-237828, paragraphs 0023-0025 JP 2004-2880 paragraphs 0023-0025 JP 2002-154168 paragraph 0029 JP 2003-165850 paragraph 0021 JP 2000-290401 paragraph 0032

  It is an object of the present invention to provide a method for easily producing an isotropic film, particularly an isotropic polyimide film in the full width of the film, which is considered particularly useful in the technical field of electronics such as FPC. .

This invention can achieve the said subject with the following novel manufacturing methods and a polyimide film.
1) In the process for producing a continuously produced polyimide film, at least the following (A) a step of polymerizing polyamic acid (B) a composition containing polyamic acid and an organic solvent is cast and applied on a support, and then gel Forming a film;
(C) Step of peeling off the gel film and fixing both ends (D) Step of conveying the inside of the heating furnace while fixing both ends of the film,
A method for producing a polyimide film comprising:
The step (D)
(D-1) a step of transporting the film so that the tension in the film width direction (TD direction) is substantially no tension;
(D-2) including a step of stretching the film in the TD direction;
And,
The said heating furnace consists of two or more several heating furnaces, and the temperature spot of the width direction in a 1st heating furnace is 100 degrees C or less, The manufacturing method of the isotropic polyimide film characterized by the above-mentioned.
2) The method for producing an isotropic polyimide film according to 1), wherein the step (D-1) is performed at an entrance of a heating furnace.
3) The method for producing an isotropic polyimide film according to 2), wherein the heating furnace includes two or more heating furnaces, and the temperature of the first heating furnace is 300 ° C. or less.
4) In the step (D-1), when the distance between the fixed ends on both ends is X and the width of the film between the fixed ends on both ends is Y, the tension in the TD direction so that X and Y satisfy the following formula: The method for producing an isotropic polyimide film according to any one of 1) to 3), wherein both ends are fixed so as to be substantially tension free.
20.0 ≧ (Y−X) / Y × 100> 0.00
5) In the step (D-2), when the distance between the fixed ends at both ends in the TD direction before stretching is Z, and the distance between the fixed ends at both ends when the film is stretched in the furnace is W, Z The method for producing an isotropic polyimide film according to any one of 1) to 4), wherein the film is stretched in the TD direction so that W and W satisfy the following formula:
40.0 ≧ (W−Z) / Z × 100> 0.00
6) An isotropic polyimide film produced using the method for producing a polyimide film according to any one of 1) to 5).

  According to the method for producing a polyimide film of the present invention, an isotropic polyimide film can be obtained over the entire width of a continuously produced polyimide film.

The present invention provides a process for producing a continuously produced polyimide film, wherein at least the following (A) step of polymerizing polyamic acid (B) after casting and coating a composition containing polyamic acid and an organic solvent on a support A step of forming a gel film,
(C) Step of peeling off the gel film and fixing both ends (D) Step of conveying the inside of the heating furnace while fixing both ends of the film,
A method for producing a polyimide film comprising:
(1) The step (D)
(D-1) a step of transporting the film so that the tension in the film width direction (TD direction) is substantially no tension;
(D-2) including a step of stretching the film in the TD direction;
And,
(2) The heating furnace comprises a plurality of heating furnaces of two or more, and the temperature variation in the width direction in the first heating furnace is 100 ° C. or less. is there. Hereinafter, each process will be described in detail.

Step (A) Step (A) is a step of polymerizing polyamic acid. As a method for producing the polyamic acid, a known method can be used. Usually, at least one aromatic dianhydride and at least one diamine are dissolved in a substantially equimolar amount in an organic solvent, The resulting organic solvent solution is produced by stirring under controlled temperature conditions until polymerization of the acid dianhydride and diamine is completed. These organic solvent solutions are usually obtained at a solid concentration of 5 to 40 wt%, preferably 10 to 30 wt%. When the solid content concentration is in this range, an appropriate molecular weight and solution viscosity are obtained.
Any known method can be used as the polymerization method, and the following method is particularly preferable as the polymerization method. That is,
1) A method in which an aromatic diamine is dissolved in an organic polar solvent and this is reacted with a substantially equimolar amount of an aromatic tetracarboxylic dianhydride for polymerization.
2) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Then, the method of superposing | polymerizing using an aromatic diamine compound so that an aromatic tetracarboxylic dianhydride and an aromatic diamine compound may become substantially equimolar in all the processes.
3) An aromatic tetracarboxylic dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding an aromatic diamine compound here, using the aromatic tetracarboxylic dianhydride so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. How to polymerize.
4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent and then polymerized using an aromatic diamine compound so as to be substantially equimolar.
5) A method of polymerizing by reacting a substantially equimolar mixture of aromatic tetracarboxylic dianhydride and aromatic diamine in an organic polar solvent.
And so on.

  The organic solvent suitably used for the polymerization of the polyamic acid is not particularly limited, but ureas such as tetramethylurea, N, N′-dimethylethylurea, dimethyl sulfoxide, diphenylsulfone, tetramethylsulfone Such as sulfoxide or sulfones, N, N′-dimethylacetamide (abbreviation DMAc), N, N′-dimethylformamide (abbreviation DMF), N-methyl-2-pyrrolidone (abbreviation NMP), γ-butyllactone, hexa Amides such as methylphosphoric triamide, or aprotic solvents such as phosphorylamides, alkyl halides such as chloroform and methylene chloride, aromatic hydrocarbons such as benzene and toluene, phenols such as phenol and cresol, Dimethyl ether, diethyl ether Can ethers such as p- cresol methyl ether. These organic solvents are usually used alone, but two or more kinds may be used in appropriate combination. Among these organic solvents, aprotic polar solvents are preferably used, and amides such as DMF, DMAc, and NMP are more preferably used.

  The acid dianhydride used as the monomer raw material for the polyamic acid is not particularly limited, but specific examples include p-phenylenebis (trimellitic acid monoester acid anhydride), p-methylphenylene. Bis (trimellitic acid monoester acid anhydride), p- (2,3-dimethylphenylene) bis (trimellitic acid monoester acid anhydride), 4,4′-biphenylenebis (trimellitic acid monoester acid anhydride) ), 1,4-naphthalenebis (trimellitic acid monoester anhydride), 2,6-naphthalenebis (trimellitic acid monoester anhydride) 2,2-bis (4-hydroxyphenyl) propanedibenzoate- 3,3 ′, 4,4′-tetracarboxylic dianhydride; furthermore, ethylenetetracarboxylic acid, 1,2,3,4-butanetetra Carboxylic acid, cyclopentanetetracarboxylic acid, pyromellitic acid, 1, 2, 3, 4-benzenetetracarboxylic acid, 3, 3 ', 4, 4'-biphenyltetracarboxylic acid, 2, 2, 3, 3-biphenyl Tetracarboxylic acid, 3, 3 ′, 4, 4′-benzophenone tetracarboxylic acid, 2, 2 ′, 3, 3′-benzophenone tetracarboxylic acid, bis (2,3-dicarboxyphenyl) methane, bis (3, 4-Dicarboxyphenyl) methane, 1,1-bis (2,3-dicarboxyphenyl) ethane, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (2,3- Dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) ether, bis (2,3-dicarboxyphenyl) ether, bis (2,3-dicarboxyphenyl) sulfone, 2,3,6,7-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 2,3,6,7-anthracenetetracarboxylic acid Acid, 1, 2, 7, 8-phenanthrenetetracarboxylic acid, 3, 4, 9, 10-perylenetetracarboxylic acid, 4, 4- (p-phenylenedioxy) diphthalic acid, 4, 4- (m-pheny An aromatic tetracarboxylic acid such as (rangeoxy) diphthalic acid, 2,2-bis [(2,3-dicarboxyphenoxy) phenyl] propane, or an acid dianhydride of the acid.

  Among these, pyromellitic acid, 1, 2, 3, 4-benzenetetracarboxylic acid, 3, 3 ', 4, 4'-biphenyltetracarboxylic acid, 2, 2', 3, 3'-biphenyltetracarboxylic acid 3, 3 ′, 4, 4′-benzophenone tetracarboxylic acid, 2, 2 ′, 3, 3′-benzophenone tetracarboxylic acid, aromatic tetracarboxylic acid of p-phenylenebis (trimellitic acid monoester acid) or An acid dianhydride of the acid is preferably used.

  It is preferable that at least one of these compounds is used. Moreover, these compounds may use only 1 type and may be used in combination of 2 or more types as appropriate.

  The diamine used as a monomer raw material for the polyamic acid is not particularly limited, but p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3, 4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3 '-Diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3, 3'-diaminodiphenylmethane, 3,4'-diamino Diphenylmethane, 4,4′-diaminodiphenylmethane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (3-aminophenyl) propane, 2- (3-aminophenyl) -2- (4- Aminophenyl) propane, 2,2-bis (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-bis (3-aminophenyl) -1,1,1 , 3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) ben, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3 − (3-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 3, 3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5-phenoxybenzophenone, 4,4 ' -Bis (4-aminophenoxy) biphenyl, 3,3'-bis (4-aminophenoxy) biphenyl, 3,4'-bis (3-aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] Ketone, bis [4- (3-aminophenoxy) phenyl] ketone, bis [3- (4-aminophenoxy) phenyl Nyl] ketone, bis [3- (3-aminophenoxy) phenyl] ketone, 3,3′-diamino-4,4′-diphenoxydibenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone 3,4′-diamino-4,5′-diphenoxybenzophenone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [3- (4-aminophenoxy) phenyl] sulfide, bis [4- ( 3-aminophenoxy) phenyl] sulfide, bis [3- (4-aminophenoxy) phenyl] sulfide, bis [3- (3-aminophenoxy) phenyl] sulfide, bis [3- (4-aminophenoxy) phenyl] sulfone Bis [4- (4-aminophenyl) sulfone, bis [3- (3-aminophenoxy) phenyl] sulfur Hong, bis [4- (3-aminophenyl) sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, bis [3- (3-aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] methane, bis [3- (3-aminophenoxy) Phenyl] methane, bis [3- (4-aminophenoxy) phenyl] methane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) Phenyl] propane, 2,2-bis [3- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1, , 3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [ 3- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [3- (4-aminophenoxy) phenyl] -1,1,1, 3,3,3-hexafluoropropane, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3- Bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3-amino-4-phenoxybenzoyl) benzene, 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,3 Bis (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-amino-5-biphenoxybenzoyl) benzene, 1,3-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3- Bis [4- (4-amino-6-fluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, Examples include [alpha] -dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-cyanophenoxy)-[alpha], [alpha] -dimethylbenzyl] benzene, diaminopolysiloxane and the like.

  At least one of these compounds is preferably used. Moreover, these compounds may use only 1 type and may use it in combination of 2 or more types as appropriate.

  Among these, p-phenylenediamine, m-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, and 4,4′-diaminodiphenyl ether are preferably used. It is done.

  In particular, in the present invention, the combination of the following acid dianhydrides and diamines can be more preferably used as a monomer raw material because the degree of molecular orientation of the resulting polyimide film can be easily controlled within a preferable range.

  Specifically, (1) a combination using p-phenylenediamine, 4,4′-diaminodiphenyl ether, pyromellitic dianhydride, p-phenylenebis (trimellitic acid monoester anhydride), ( 2) Combination using p-phenylenediamine, 4,4′-diaminodiphenyl ether, pyromellitic dianhydride, 3, 3 ′, 4, 4′-biphenyltetracarboxylic dianhydride, (3) p -Phenylenediamine, 4,4'-diaminodiphenyl ether, pyromellitic dianhydride, a combination using 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, (4) p-phenylenediamine 4,4'-diaminodiphenyl ether, pyromellitic dianhydride, p-phenylenebis (trimellitic acid monoester anhydride), 3, 3 ', 4, Combination using '-biphenyltetracarboxylic dianhydride, (5) p-phenylenediamine, 4,4'-diaminodiphenyl ether, 3, 3', 4, 4'-biphenyltetracarboxylic dianhydride (6) 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, combination using pyromellitic dianhydride, (7) 4,4′-diaminodiphenyl ether By using a combination of tellurium, p-phenylenediamine, and pyromellitic dianhydride, the molecular orientation degree of the finally obtained polyimide film can be easily controlled within a preferable range.

  Moreover, the one where the elasticity modulus of a polyimide film is high is preferable from the point of the handleability when a film is exposed to high temperature. Specifically, for example, p-phenylenediamine as a diamine raw material, pyromellitic dianhydride, p-phenylenebis (trimellitic acid monoester acid anhydride), 3, 3 ′, 4, 4 as an acid dianhydride raw material. By using '-biphenyltetracarboxylic dianhydride, 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride, the elastic modulus can be increased. The tensile elastic modulus is preferably 4.0 GPa or more. A higher elastic modulus is preferable, but from the viewpoint of film forming property (if the elastic modulus is too high, the film may be broken during imidization) and flexibility in handling may be lacking. Therefore, the upper limit is preferably 12.0 GPa or less.

  The average molecular weight of the polyamic acid thus obtained is preferably 10,000 or more in terms of GPC PEG (polyethylene glycol) in view of film properties.

(B) Step (B) A step of forming a gel film after casting and applying a composition containing a polyamic acid and an organic solvent (also referred to as a polyamic acid solution) on a support. The composition used in step (B) may be a composition to which other components such as a reactive agent capable of reacting with polyamic acid are added.

  The viscosity of the polyamic acid solution was kept in a water bath kept at 23 ° C. for 1 hour. 7 is measured at 4 rpm, and the viscosity is preferably 50 Pa · s or more and 1000 Pa · s or less, more preferably 100 Pa · s or more and 500 Pa · s or less, and most preferably 200 Pa · s or more and 350 Pa · s or less. It is most preferable from the viewpoint that it is easy to handle when producing a film molded body.

  Moreover, the solid content concentration of the polyamic acid in the polyamic acid solution used in the step (B) is preferably 5 to 40 wt%, preferably 10 to 30 wt%, and more preferably 13 to 25 wt%. If it is in the said range, when manufacturing a film molded object, it exists in the tendency which becomes easy to handle.

  If necessary, the viscosity and concentration of the polyamic acid solution can be adjusted by adding an organic solvent such as the polyamic acid polymerization solvent exemplified in step (A).

  A conventionally well-known method can be used about the method of manufacturing a polyimide film from these polyamic-acid solutions. This method includes a thermal imidization method and a chemical imidization method. The thermal imidization method is a method for promoting imidization only by heating. The heating conditions can vary depending on the type of polyamic acid, the thickness of the film, and the like. Furthermore, it is desirable that the polyamic acid solution is mixed with a release agent, a thermal imidation catalyst, etc. as appropriate for imidization. The chemical imidization method is a method in which an imidization catalyst and a dehydrating agent are allowed to act on a polyamic acid organic solvent solution. Examples of the dehydrating agent include aliphatic acid anhydrides such as acetic anhydride and aromatic acid anhydrides such as benzoic anhydride. Examples of the imidization catalyst include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, picoline, and isoquinoline.

  The amount of the imidization catalyst to be used is not particularly limited, but is preferably an imidization catalyst / amide group in polyamic acid = 0.01 to 10 in molar ratio. More preferably, imidation catalyst / amide group in polyamic acid = 0.5 to 5 is preferable.

  When the dehydrating agent and the imidization catalyst are used in combination, the dehydrating agent / amide acid in polyamic acid is preferably 0.01 to 10 in molar ratio, and the imidization catalyst / amide acid in polyamic acid is preferably 0.01 to 10. Preferably there is. More preferably, dehydrating agent / amide group in polyamic acid = 0.5 to 5 is preferable, and imidization catalyst / amide group in polyamic acid = 0.5 to 5 is preferable. In this case, a reaction retarder such as acetylacetone may be used in combination. The content of the dehydrating agent and the imidization catalyst with respect to the polyamic acid may be defined by the time (pot life) from when the polyamic acid and the dehydrating agent / catalyst mixture are mixed at 0 ° C. until the viscosity starts to increase. good. Generally, the pot life is preferably 0.1 minute to 120 minutes, more preferably 1 minute to 60 minutes.

  Further, additives such as a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a pigment, a dye, a fatty acid ester, and an organic lubricant (for example, wax) may be added and used. In addition, clay, mica, titanium oxide, calcium carbonate, kaolin, talc, wet or dry silica, colloidal silica, calcium phosphate, phosphoric acid are used to impart surface slipperiness, abrasion resistance, scratch resistance, etc. Inorganic particles such as calcium hydrogen, barium sulfate, alumina and zirconia, organic particles containing acrylic acid, styrene and the like as constituent components may be added.

  When obtaining a polyamic acid solution containing the above-mentioned imidation catalyst, dehydrating agent, additives, etc., it is necessary to provide a process for removing insoluble raw materials and mixed foreign matters with a filter or the like before mixing them. It is preferable in reducing the amount. The aperture of the filter is preferably 1/2, preferably 1/5, and more preferably 1/10 of the thickness of the obtained film.

  The polyamic acid solution thus obtained is continuously cast and applied onto a support and dried to obtain a gel film. Any support can be used as long as it can withstand the heating required to remove the organic solvent solution of the synthetic resin solution without being dissolved by the solution resin. Particularly preferably, an endless belt or a metal drum produced by joining metal plates is preferable for drying a coating solution in the form of a solution. The material of the endless belt or drum is preferably a metal, and among them, a SUS material is preferably used. Because the surface is plated with a metal such as chromium, titanium, nickel, cobalt, etc., the adhesion of the solvent on the surface is improved, or the dried organic insulating film is easy to peel off. Plating treatment is preferably performed. The endless belt and the metal drum preferably have a smooth surface, but it is also possible to produce and use innumerable irregularities on the endless belt or the metal drum. It is preferable that the unevenness processed on the endless belt or the metal drum has a diameter of 0.1 to 100 μm and a depth of 0.1 to 100 μm. By producing irregularities on the metal surface, it becomes possible to produce fine protrusions on the surface of the organic insulating film, and the protrusions can generate scratches due to friction between films, or improve the slipperiness between films. Is possible.

The gel film in the present invention refers to a film in which a part of an organic solvent or a reaction product (these are referred to as residual components) remains in a polyimide film by heating and drying the polyamic acid solution. In the production process of the polyimide film, the organic solvent dissolving the polyamic acid solution, the imidization catalyst, the dehydrating agent, the reaction product (water absorbing component of the dehydrating agent, water), and the additive remain as remaining components in the gel film. . The ratio of the remaining component remaining in the gel film is the weight of the remaining component b (g) relative to the weight of the gel film after drying (hereinafter also referred to as the completely dry synthetic resin weight) a (g) present in the gel film. ) Is a value calculated by the following calculation formula, the residual component ratio is preferably 500% or less, more preferably 25% or more and 200% or less, and particularly preferably Is preferably 30% or more and 150% or less.
c = b / a × 100 (Formula 2)
If it exceeds 500%, in the step of transporting the inside of the heating furnace while fixing both ends of the film to be described later (D), the resulting polyimide film may crack due to an increase in the amount of film shrinkage accompanying the removal of the organic solvent. .

  The gel film weight a after drying and the residual component weight b were calculated by measuring the gel film weight d of 100 mm × 100 mm, drying the gel film in an oven at 450 ° C. for 20 minutes, and then cooling to room temperature. Thereafter, the weight is measured to obtain a completely dry synthetic resin weight a. The residual component weight b is calculated from the gel film weight d and the completely dry synthetic resin weight a using the formula b = da.

  In the process of producing the gel film, the conditions for heating and drying on the support (drying temperature, hot air velocity when exhausting at the time of drying, exhaust speed, drying time, etc.) are such that the remaining component ratio is within the above range. It is preferable to set as appropriate. In particular, in the process of producing a polyimide film, it is preferable to heat and dry the film at a temperature in the range of 50 to 200 ° C, and it is particularly preferable to heat and dry at 50 to 180 ° C. Moreover, it is preferable to dry within the range for 20 second-60 minutes. Drying is preferably performed by multi-stage temperature control.

(C) Process
(C) A process is a process of peeling off a gel film from a support body and fixing the both ends of a gel film continuously. In the present invention, the step of fixing the end portion of the gel film is a step of gripping the end portion of the gel film using a gripping device generally used in a film manufacturing apparatus such as a pin sheet or a clip.

  In addition, when fixing the edge part of a gel film of this (C) process as a method of fixing so that the tension | tensile_strength of TD direction may become substantially no tension in at least one part in the (D) process mentioned later. The tension in the TD direction may be fixed so as to be substantially no tension. This is a method in which the tension in the TD direction becomes substantially no tension at the stage of fixing the film, and the film is sent to the step (D) as it is. Specifically, when the end portion is fixed, the film is loosened and fixed.

(D) Process
(D) A process is a process of conveying the inside of a heating furnace, fixing the both ends of a film. As a heating furnace to be used, a known heating furnace may be used. For example, (1) a hot air furnace of a system in which hot air of 100 ° C. or more is jetted and heated from the upper surface or the lower surface of the film or both surfaces, (2) A far-infrared furnace equipped with a far-infrared generator that irradiates far-infrared rays to fire the film is preferably used.
In the present invention, the conditions for conveying the inside of the heating furnace are not particularly limited, but it is important to connect a plurality of two or more heating furnaces and to control temperature spots in the first heating furnace. That is, it is important that a plurality of heating furnaces are connected, the temperature is raised stepwise, and the temperature spots of the first heating furnace are 100 ° C. or lower. In particular, in the first heating furnace, the film is preferably heated by hot air from above and below by a hot air spraying device (for example, 17 in FIG. 1) that generates hot air.

  The plurality of heating furnaces used at this time are not particularly limited, and a hot air furnace or a far-infrared furnace may be used alone or in combination. Specifically, for example, by connecting a plurality of the hot blast furnaces and far-infrared furnaces together, a stepwise heating furnace that raises the heating temperature stepwise can be obtained. In the case of a stage-type heating furnace, it is preferable that a device for partitioning each furnace is provided so that heat from the preceding heating furnace is not transmitted to the subsequent heating furnace. It is preferable to appropriately change the number of heating furnaces and the temperature of each heating furnace depending on the firing conditions.

  The temperature variation in the width direction in the first heating furnace in the present invention is the width of the film lower portion between both ends of the film transport apparatus (1 in FIG. 1) when the film passes through the furnace (19 in FIG. 1). The temperature may be measured at five points in the direction (20 to 24 in FIG. 1), and the difference between the highest temperature and the lowest temperature may be regarded as a temperature spot. For example, in FIG. 1, 20 and 24 are installed within 5 cm from the film conveying apparatus (1 in FIG. 1), and 20 to 21, 21 to 22, 22 to 23, and 23 to 24 in FIG. Install in. The temperature spots thus measured are preferably 100 ° C. or lower, more preferably 80 ° C. or lower, particularly preferably 50 ° C. or lower. By controlling the temperature below this temperature, it is difficult for abnormalities in molecular orientation due to temperature spots to occur, and it is possible to produce an isotropic polyimide film over the entire width.

In the present invention, the heating temperature (initial heating temperature) of the first heating furnace in which the gel film gripped at both ends is first conveyed is preferably 300 ° C. or lower, and a temperature range of 60 ° C. or higher and 250 ° C. or lower. More preferably, it is 100 degreeC or more and 200 degrees C or less. If it is this temperature range, it will become easy to obtain an isotropic film in the polyimide film obtained.
Furthermore, the bowing phenomenon of a polyimide film can be suppressed by making the heating temperature at the time of first heating into 300 degrees C or less. This makes it possible to produce an isotropic film at the end of the polyimide film.
The temperature of the second heating furnace is preferably set to 50 ° C. or more and 300 ° C. or less than the temperature of the first heating furnace. Particularly preferably, the temperature is set to 60 ° C. or more and 250 ° C. or less than the temperature of the first heating furnace in order to control the degree of molecular orientation of the polyimide film to be small.
On the other hand, even if the temperature of the first heating furnace is less than 60 ° C., it is possible to produce a polyimide film, which is preferable in controlling the molecular orientation axis of the film, but drying does not proceed. When the heating temperature is less than 60 ° C, the temperature of the second heating furnace is preferably set to a temperature of 100 ° C or higher and 250 ° C or lower. When the temperature of the 1st heating furnace is 60 degrees C or less, it becomes easy to obtain an isotropic film by setting the temperature of a 2nd heating furnace to the said temperature.
In addition, the heating temperature in the heating furnace (the heating furnace after the third heating furnace) after the first heating furnace and the second heating furnace can be heated stepwise in a temperature range from 200 ° C to about 600 ° C. It is preferable to set so. When the maximum firing temperature is low, the imidation rate may not be complete, and therefore it is preferable to perform sufficient heat treatment step by step.

  Here, it demonstrates concretely by the example using a step-type heating furnace. As shown in FIGS. 2 (a) and 2 (b), the staged heating furnace 40 is composed of five heating furnaces 41 to 45, the first heating furnace 41, the second heating furnace 42, the third heating furnace 41, and the third heating furnace 41. The heating furnace 43, the fourth heating furnace 44, and the fifth heating furnace 45 are arranged in this order along the transport direction (MD direction: direction D1) of the film 50. 2B is a schematic view of the stepped heating furnace 40 as viewed from above, and FIG. 2A is a view of the stepped heating furnace 40 as viewed from the side together with the polyimide film winding device 46. It is.

  As shown in FIG. 2A, the gel film 50 is fixed without slack by a pair of gripping members 52 at both ends in the width direction (TD direction) and conveyed to the first heating furnace 40.

  At least a part of the step (D) includes a step of fixing and conveying the tension in the film width direction (TD direction) substantially without tension (hereinafter referred to as a step (D-1)). It is important in terms of obtaining an isotropic film over the entire width.

Here, the fact that the tension in the TD direction is substantially tensionless means that the tensile tension due to mechanical handling is not applied in the TD direction other than the tension due to the weight of the film. This means that the film width (61 in FIG. 3) between the fixed ends on both ends is substantially larger than the distance between the fixed ends on the both ends (V ₁ in FIGS. 2 and 3). A film under such a condition is called a film under substantially no tension. Referring to FIG. 3, the film is fixed by a gripping device. The width of the fixing distance at the start of fixing (distance fixing starting end distance) is V ₀ in FIG. The fixed film is conveyed into the furnace while being fixed by the both-end fixing device. Inter-device distance when the distance is narrowed between the most film holding device is conveyed (both ends fixed minimum distance) 2, at a point where the length of the V ₁ of the FIG. 3 is the most contracted both ends fixed device end Is the distance. Normally, both ends of the film at the start of fixing are in tension with the pins, and the both ends fixing start end distance V ₀ and the film width 61 between both ends fixing starting ends are the same. However, as described in the step (C), there is no problem even if the end portion is fixed so that the film sags. In the present invention, as shown in FIG. 3, it is desirable that the both-end fixed minimum distance V ₁ and the film width 61 therebetween are different, and the distance between the both-end fixed ends is small. Specifically, the film is loosened and fixed at the portion of the both ends fixed minimum distance. In the present invention, at the entrance of the heating furnace in the step (D), it is fixed that the tension in the TD direction is substantially tensionless, with the orientation axis directed in the MD direction over the entire width of the film. It is preferable from the point of manufacturing a film. In order to fix and transport the tension in the TD direction so as to be substantially no tension at the entrance of the heating furnace, when fixing the end of the gel film in the step (C) described above, In addition to the method of fixing the tension so that it is substantially tensionless and sending it to the step (D) as it is (method 1), after the step (C), the operation of temporarily reducing the distance between the fixed ends of both ends (see FIG. (Method of shrinking from V ₀ to V ₁ described in 2) and sending to step (D) (Method 2) is mentioned, but the latter method is easy and preferable. Of course, after entering the heating furnace in the step (D), an operation of reducing the distance between the fixed ends of both ends may be performed (method 3), or a combination of these methods may be performed. In Method 3, the operation of reducing the distance between the fixed ends of both ends is preferably performed in a temperature range of 300 ° C. or lower, more preferably 250 ° C. or lower, particularly 200 ° C. or lower. When Method 3 is performed in a temperature range higher than 300 ° C., it tends to be difficult to obtain an isotropic film, and an isotropic film can be obtained particularly at the film edge. It tends to be difficult.

Method 1 is preferably a method of fixing both ends of the gel film so as to satisfy (Equation 3), and Method 2 reduces the distance between the fixed ends so as to satisfy (Equation 3). (Shrink from V _{0 to} V ₁ ) is preferable. In particular, since it is easy to control the molecular orientation in the MD direction, when the distance V ₁ of the fixed distance at both ends is X and the width 61 of the film between the fixed ends at both ends is Y, X and Y are given by It is preferably fixed so as to satisfy.
20.0 ≧ (Y−X) / Y × 100> 0.00 (formula 3)
If (Y-X) / Y × 100 (this may be referred to as TD shrinkage for convenience) is made larger than the above range, it becomes difficult to stably control the slackness of the film, and the amount of slackness is less than the progress method. May change. In some cases, the film may come off from the end gripping device due to the slackness of the film, and further wrinkles may be generated at the end, so that stable film production may not be possible. More preferably, 15.0 ≧ (Y−X) / Y × 100> 0.00. Most preferably, 10.0 ≧ (Y−X) / Y × 100> 0.00.

  In addition, as a method of performing the step (D-1) in which the film is fixed and transported so that the tension in the film width direction (TD direction) is substantially no tension in at least a part of the step (D), the step (D) It is preferable that the tension in the TD direction is fixed so as to be substantially no tension at the entrance of the heating furnace in FIG. There is a method in which the step of shrinking is terminated before the film is inserted into the furnace. In this case, the fact that there is substantially no tension can also be expressed as follows. That is, when V1 of the both-end fixed minimum distance is X and the width 61 of the film between the both-end fixed start ends is Y, it means that X and Y are fixed so as to satisfy the following formula.

Y-X> 0.00 ... (Formula 4)
It is also important that the step (D) further includes a step of stretching the film in the TD direction (hereinafter referred to as (D-2) step).

The step (D-2) in the present invention is a step of stretching the film in the TD direction in the heating furnace after the step (D-1). In the step (D-1), the film is fixed and transported so that the tension in the film width direction (TD direction) is substantially no tension, but when the film is heated in the heating furnace, the film contracts to some extent. . After shrinking and the film is no longer slack, the film is stretched in the TD direction. The amount to be stretched (referred to as TD expansion coefficient for convenience) is the width of the fixed ends at both ends in the TD direction Z (V _{1 in} FIG. 2A) before stretching, and the film was stretched in the TD direction in the furnace. When the width of the fixed ends at both ends is W (V ₂ or V _{3 in} FIG. 2A), it is preferable to satisfy the following formula 5.
40.0 ≧ (W−Z) / Z × 100> 0.00 (Formula 5)
If (W−Z) / Z × 100 (this may be referred to as the TD expansion coefficient for convenience) is made larger than the above range, it may be difficult to control the molecular orientation of the film to be small. More preferably, 30.0 ≧ (W−Z) / Z × 100> 0.00. Particularly preferably, 20.0 ≧ (W−Z) / Z × 100> 0.00.
Further, the shrinkage may be performed again after the step (D-2) as necessary, and the film width may be increased. It is preferable to appropriately select the TD shrinkage and the TD expansion. A particularly preferable value is a value calculated by TD shrinkage ratio ≧ TD expansion coefficient in order to control the degree of molecular orientation to a small value in the entire width.

  When the polyimide film is a film whose elastic modulus decreases at a high temperature, the temperature at which the step (D-2) is performed is preferably stretched at a temperature of (temperature at which the elastic modulus changes) ± 100 ° C. In particular, 300 ° C. or more and 500 ° C. or less, particularly preferably 350 ° C. or more and 480 ° C. or less is preferable because the elastic modulus of the polyimide film is lowered and the film is easily stretched. In addition, when a polyimide film is conveyed in a furnace at a stretching temperature, the film may be softened and stretched completely. In that case, it is preferable to set the temperature outside the above range as appropriate.

  In the present invention, the shrinkage in the step (D-1), the stretching in the step (D-2), and the film tension in the MD direction, the residual component weight of the gel film, and the heating temperature are appropriately determined. A film with a small degree of molecular orientation may be manufactured by adjusting. In the case of a polyimide film, the heating temperature and heating time of the film are completely different depending on whether chemical imidization or thermal imidization is performed. If the control is performed inside, the target film can be obtained.

  In addition, in this invention, it is preferable that the tension | tensile_strength given to MD direction of a gel film is 1-20 kg / m, Especially preferably, it is 1-15 kg / m so that a gel film may not loosen when conveyed in a furnace. m is preferable. When the tension is 1 kg / m or less, it may be difficult to stably transport the film, and it tends to be difficult to produce a stable film by gripping the film. Further, when the tension applied to the film is 20 kg / m or more, it tends to be difficult to produce an isotropic film particularly at the end of the film. The tension generator applied to the gel film transported into the furnace includes a load roll that applies a load to the gel film, a roll that adjusts the rotation speed of the roll to change the load, and the gel film is sandwiched between two rolls to control the tension. Although the tension | tensile_strength to a gel fill can be adjusted using various methods, such as the system using a two-ply roll which performs, it is not limited to this. The tension applied to the film is preferably adjusted appropriately within the above range depending on the thickness of the polyimide film.

(E) Other steps In the present invention, the step of producing a polyimide film may include other steps of the above steps (A) to (D), for example, as shown in Fig. 2 (b). Thus, after passing a heating furnace, the process (46 of FIG. 2) to wind up to a winding apparatus is mentioned. Furthermore, you may provide the apparatus which apply | coats a different varnish to the film surface in a process, and the apparatus which processes a surface.

  Moreover, you may perform arbitrary processes, such as heat processing, shaping | molding, surface treatment (plasma treatment, corona discharge treatment), lamination, coating, printing, embossing, etching, etc. with respect to a polyimide film.

<Polyimide film>
The thickness of the film obtained by the production method of the present invention is preferably 1 to 200 μm, and particularly preferably 1 to 100 μm. When the thickness of the film is 200 μm or more, the flexibility of the film is lowered, which is not preferable.

By using the production method of the present invention, it is possible to produce an isotropic polyimide film over the entire width. The isotropy of the film is confirmed by the MORc value (the value obtained by correcting the thickness correction of the film with a value converted to 75 μm) when the molecular orientation degree of the film is measured using a molecular orientation meter MOA2012A manufactured by Oji Scientific Instruments. I can. Here, the measurement is preferably performed at 12 GHz. The film obtained by the production method of the present invention preferably has a MORc value of 1.40 or less, and if it is less than this value, the physical property value of the polyimide film is less dependent on the direction, and the film physical property value is almost equal in all directions. Can be considered. A more preferable range of the MORc value is 1.35 or less. The MORc value is a value calculated from the following formula from the MOR value.
MORc = ((MOR−1) / film thickness (μm) × 75) +1 (formula 6)
Furthermore, if it is within the above range, for example, in a metal laminate (such as FPC) in which an adhesive layer is laminated on the polyimide film surface and attached with metal, the dimensional change after metal removal or the dimensional change due to shrinkage after heating Is preferable.

  As the MORc, a value converted to a thickness of 75 μm under the conditions of a temperature of 20 to 23 ° C. and a humidity of 40 to 70% is used. The polyimide film obtained by the production method of the present invention is preferably isotropic over the entire width. Specifically, the total width of the polyimide film means an isotropic polyimide film at a site of 70% or more (700 mm or more in the case of a 1000 mm film) with respect to the film width in the TD direction.

  The polyimide film obtained by the production method of the present invention may be used by coating one or more other polymer layers on one or both sides of the film. For example, thermoplastic polyimide (which means a resin having a glass transition temperature of 400 ° C. or less measured using a general DSC measuring device), polyester, polyolefin, polyamide, polyvinylidene chloride and acrylic polymer are directly or bonded. You may laminate | stack through layers, such as an agent. Further, when the thermoplastic polyimide resin is laminated, the thermoplastic polyimide resin and the heat-resistant polyimide film may be simultaneously applied to the support surface from one or more slit openings, and a gel film may be produced and fired. . In the method for producing a polyimide film of the present invention, one or more polymer resin solutions to be cast and applied may be applied simultaneously or sequentially so as to be laminated on a support to produce a polyimide film laminate. You can also. Furthermore, after the polyimide gel film is prepared, the film is immersed in a polyamic acid solution, or immersed in an imide solution, or a polyamic acid solution or a polyimide solution is applied to the surface of the film using a coater. You may produce a film with the form which bakes the produced polyimide gel film.

  The polyimide film obtained by the production method of the present invention can be subjected to heat treatment, molding, surface treatment (corona treatment, vacuum plasma treatment, atmospheric pressure plasma treatment), lamination, coating, printing, embossing, etching (alkali etching) as necessary. , Plasma etching), laser processing, or any other processing may be performed.

  The use of the polyimide film obtained by the production method of the present invention is not particularly limited, but for flexible printed circuit boards, TAB tape substrates or base films for high-density recording media, etc., for magnetic recording media, It is particularly preferably used for electrical insulation applications.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples. In particular, the present invention describes an example of a method for producing a polyimide film.

(Example 1)
In this example, in N, N-dimethylformamide (DMF), 4,4-diaminodiphenyl ether (ODA) 50 mol%, paraphenylenediamine (p-PDA) 50 mol%, p-phenylenebis (tri Mellitic acid monoester anhydride (TMHQ) 50 mol% and pyromellitic dianhydride (PMDA) 50 mol% were added in this order in this order and polymerized to synthesize a polyamic acid solution. To this polyamic acid solution, 2.0 times equivalent acetic anhydride and 1.0 times equivalent isoquinoline are added to the equivalent of amic acid, and cast onto an endless belt with a thickness of 820 mm and a thickness of 20 μm after firing. Then, it was dried with hot air so that the remaining component ratio was 60% by weight at 100 ° C. to 130 ° C. for about 5 minutes to obtain a gel film having self-supporting properties. After that, it was peeled off from the belt. The peeled gel film was baked by being transported into a tenter furnace with a tension of 2.0 kg / m applied in the MD direction as a tension so as not to loosen when the gel film was transported. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the pin width was 800 mm and fixed without slack (the gel width was 800 mm). The gel film was prepared at 130 ° C. (first heating furnace; hot air oven), 260 ° C. (second heating furnace; hot air oven), 360 ° C. (third heating furnace; hot air oven), 450 ° C. (fourth heating oven). Baking stepwise with a heating furnace; hot air oven) and 515 ° C. (fifth heating furnace; far-infrared furnace) to form a polyimide film. At this time, the temperature spot in the first heating furnace was 30 ° C. In this example, the polyimide film was transported so that the TD shrinkage rate was 2.0 and the TD expansion rate was 4.0. The step of reducing the both-end fixed end distance so as to be fixed so as to be substantially tension-free in the film TD direction ends before the film is inserted into the furnace. Performed in four furnaces. The elastic modulus of the obtained polyimide film was measured in the 45 ° direction from the MD direction at the same site as the site where the molecular orientation axis was measured in accordance with JIS C2318 6.3.3, and the average value was calculated. In the case of 6.0 GPa.
The molecular orientation degree was measured with a molecular orientation meter MOA2012 on both sides of 260 mm and 380 mm with the center of the polyimide film thus formed as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was found that an isotropic polyimide film having a molecular orientation of 1.40 or less over the entire film width can be produced.

(Example 2)
In the same polyamic acid solution as in Example 1, 2.0 times equivalent of acetic anhydride and 1.0 times equivalent of isoquinoline are added to the equivalent of amic acid, and the thickness becomes 20 μm after firing at a width of 1200 mm. The gel film was cast on an endless belt and dried at 100 ° C. to 140 ° C. for about 3 minutes so that the ratio of the remaining components was 62% by weight to obtain a self-supporting gel film. After that, it was peeled off from the belt. The peeled gel film was fired by being transported into a tenter furnace with a tension of 3.5 kg / m applied in the MD direction as a tension so as not to loosen when the gel film was transported. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the gel film was fixed without slack at both ends in the width direction with a pin width of 1100 mm. The gel film was 165 ° C (first heating furnace; hot air oven), 300 ° C (second heating furnace; hot air oven), 400 ° C (third heating furnace; hot air oven), 515 ° C (fourth heating oven). Baking stepwise with a heating furnace (far-infrared furnace) to form a polyimide film. At this time, the temperature spot in the first heating furnace was 30 ° C. The polyimide film was conveyed so that the TD shrinkage rate was 2.0 and the TD expansion rate was 2.0. The step of reducing the both-end fixed end distance so as to be fixed so as to be substantially tension-free in the film TD direction ends before the film is inserted into the furnace. Performed in 3 furnaces The molecular orientation axes were measured with a molecular orientation meter MOA2012 at sites on both sides of 260 mm, 380 mm, and 460 mm based on the center of the polyimide film thus obtained. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was revealed that a polyimide film having a molecular orientation controlled to be MORc 1.40 or less over the entire film width can be produced (Example 3).
A polyimide film was produced by the same production method as in Example 2 except that the TD shrinkage was 2.0 and the TD expansion was 2.6.
Using the molecular orientation meter MOA2012, the molecular orientation axes of the portions on both sides of 260 mm, 380 mm, and 460 mm were measured using the center of the polyimide film thus obtained as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was revealed that a polyimide film having a molecular orientation controlled to be MORc 1.40 or less over the entire film width can be produced (Example 4).
A polyimide film was produced by the same production method as in Example 2 except that the TD shrinkage was 4.0 and the TD expansion was 5.2.

Using the molecular orientation meter MOA2012, the molecular orientation axes of the portions on both sides of 260 mm, 380 mm, and 460 mm were measured using the center of the polyimide film thus obtained as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was found that a polyimide film having a molecular orientation controlled to be MORc 1.40 or less over the entire film width can be produced (Example 5).
In the same polyamic acid solution as in Example 1, 2.0 times equivalent of acetic anhydride and 1.0 times equivalent of isoquinoline are added to the equivalent of amic acid, and the thickness becomes 20 μm after firing at a width of 1200 mm. The gel film was cast on an endless belt and dried at 100 ° C. to 150 ° C. for about 3 minutes so that the remaining component ratio was 73% by weight to obtain a self-supporting gel film. . After that, it was peeled off from the belt. The peeled gel film was baked by being transported into a tenter furnace with a tension of 4.0 kg / m applied in the MD direction so as not to loosen when the gel film was transported. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the gel film was fixed without slack at both ends in the width direction with a pin width of 1100 mm. The gel film was subjected to 160 ° C. (first heating furnace; hot air oven), 300 ° C. (second heating furnace; hot air oven), 450 ° C. (third heating furnace; hot air oven), 515 ° C. (fourth heating oven). Baking stepwise with a heating furnace (far-infrared furnace) to form a polyimide film. At this time, the temperature spot in the first heating furnace was 18 ° C. The polyimide film was transported so that the TD shrinkage was 2.0 and the TD expansion was 3.1. The step of reducing the both-end fixed end distance so as to be fixed so as to be substantially tension-free in the film TD direction ends before the film is inserted into the furnace. Performed in 3 furnaces.
Using the molecular orientation meter MOA2012, the molecular orientation axes of the portions on both sides of 260 mm, 380 mm, and 460 mm were measured using the center of the polyimide film thus obtained as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was found that a polyimide film having a molecular orientation controlled to be MORc 1.40 or less over the entire film width can be produced (Example 6).
A polyimide film was produced by the same production method as in Example 5 except that the TD shrinkage was 2.0 and the TD expansion was 3.5.
Using the molecular orientation meter MOA2012, the molecular orientation axes of the portions on both sides of 260 mm, 380 mm, and 460 mm were measured using the center of the polyimide film thus obtained as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was revealed that a polyimide film having a molecular orientation controlled to be MORc 1.40 or less over the entire film width can be produced (Example 7).
A polyimide film was produced by the same production method as in Example 5 except that the TD shrinkage was 2.0 and the TD expansion was 4.0.
Using the molecular orientation meter MOA2012, the molecular orientation axes of the portions on both sides of 260 mm, 380 mm, and 460 mm were measured using the center of the polyimide film thus obtained as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was revealed that a polyimide film having a molecular orientation controlled to be MORc 1.40 or less over the entire width of the film can be produced (Example 8).
A polyimide film was produced by the same production method as in Example 5, except that the TD shrinkage was 1.0 and the TD expansion was 4.9.
Using the molecular orientation meter MOA2012, the molecular orientation axes of the portions on both sides of 260 mm, 380 mm, and 460 mm were measured using the center of the polyimide film thus obtained as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was revealed that a polyimide film having a molecular orientation controlled to be MORc 1.40 or less over the entire film width can be produced (Example 9).
A polyimide film was produced by the same production method as in Example 5 except that the TD shrinkage was 1.0 and the TD expansion was 4.0.
The molecular orientation degree was measured with a molecular orientation meter MOA2012 on both sides of 260 mm, 380 mm, and 460 mm with reference to the center of the polyimide film thus formed. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was found that a polyimide film having a molecular orientation controlled to be MORc 1.40 or less over the entire film width can be produced (Example 10).
In this example, in N, N-dimethylformamide (DMF), 75 mol% of 4,4-diaminodiphenyl ether (ODA), 25 mol% of paraphenylenediamine (p-PDA), pyromellitic dianhydride (PMDA) 100 mol% was added in this order in this order and polymerized to synthesize a polyamic acid solution. To this polyamic acid solution, 2.0 times equivalent acetic anhydride and 1.0 times equivalent isoquinoline are added to the equivalent of amic acid, and cast onto an endless belt with a thickness of 820 mm and a thickness of 20 μm after firing. Then, it was dried with hot air so that the remaining component ratio was 60% by weight at 100 to 150 ° C. for about 5 minutes to obtain a gel film having self-supporting property. After that, it was peeled off from the belt. The peeled gel film was baked by being transported into a tenter furnace with a tension of 2.0 kg / m applied in the MD direction as a tension so as not to loosen when the gel film was transported. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the gel film was fixed without slack at both ends in the width direction with a pin width of 800 mm. The gel film was prepared at 130 ° C. (first heating furnace; hot air oven), 260 ° C. (second heating furnace; hot air oven), 360 ° C. (third heating furnace; hot air oven), 450 ° C. (fourth heating oven). Baking stepwise with a heating furnace; hot air oven) and 515 ° C. (fifth heating furnace; far-infrared furnace) to form a polyimide film. At this time, the temperature spot in the first heating furnace was 45 ° C. The film was conveyed while shrinking and expanding the polyimide film in the TD direction so that the TD shrinkage was 3.9 and the TD expansion was 4.2. The step of reducing the both-end fixed end distance so as to be fixed so as to be substantially tension-free in the film TD direction ends before the film is inserted into the furnace. Performed in four furnaces.
It was 4.2 GPa when the elasticity modulus of the 45 degree direction from MD direction was measured for the elasticity modulus of the obtained polyimide film by the method of 6.3.3 of JISC2318.
The molecular orientation degree was measured with a molecular orientation meter MOA2012 on both sides of 260 mm and 380 mm with the center of the polyimide film thus formed as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was found that a polyimide film having a molecular orientation controlled to MORc 1.40 or less over the entire width of the film can be produced. Even if the type of the polyimide film is changed, a polyimide film oriented in the MD direction can be produced if the polyimide film has a modulus of elasticity of 4.0 GPa or more.

(Example 11)
In this example, in N, N-dimethylformamide (DMF), 45 mol% of 4,4-diaminodiphenyl ether (ODA), 55 mol% of paraphenylenediamine (p-PDA), pyromellitic dianhydride (PMDA) 80 mol% and biphenyltetracarboxylic dianhydride 20 mol% were added in this order in this order and polymerized to synthesize a polyamic acid solution. To this polyamic acid solution, 2.0 times equivalent acetic anhydride and 1.0 times equivalent isoquinoline are added to the equivalent of amic acid, and cast onto an endless belt with a thickness of 820 mm and a thickness of 20 μm after firing. Then, it was dried with hot air so that the remaining component ratio was 60% by weight at 100 to 150 ° C. for about 5 minutes to obtain a gel film having self-supporting property. . After that, it was peeled off from the belt. The peeled gel film was baked by being transported into a tenter furnace with a tension of 2.0 kg / m applied in the MD direction as a tension so as not to loosen when the gel film was transported. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the gel film was fixed without slack at both ends in the width direction with a pin width of 800 mm. The gel film was prepared at 130 ° C. (first heating furnace; hot air oven), 260 ° C. (second heating furnace; hot air oven), 360 ° C. (third heating furnace; hot air oven), 450 ° C. (fourth heating oven). Baking stepwise with a heating furnace; hot air oven) and 515 ° C. (fifth heating furnace; far-infrared furnace) to form a polyimide film. At this time, the temperature spot in the first heating furnace was 42 ° C. The film was conveyed while shrinking and expanding the polyimide film in the TD direction so that the TD shrinkage was 3.9 and the TD expansion was 4.2. The step of reducing the both-end fixed end distance so as to be fixed so as to be substantially tension-free in the film TD direction ends before the film is inserted into the furnace. Performed in four furnaces.
When the elastic modulus of the obtained polyimide film was measured in a 45 ° direction from the MD direction by a method based on JIS C2318 6.3.3, it was 5.5 GPa.
The molecular orientation degree was measured with a molecular orientation meter MOA2012 on both sides of 260 mm and 380 mm with the center of the polyimide film thus formed as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was found that a polyimide film having a molecular orientation controlled to MORc 1.40 or less over the entire width of the film can be produced. Even if the type of the polyimide film is changed, a polyimide film oriented in the MD direction can be produced if the polyimide film has a modulus of elasticity of 4.0 GPa or more.

(Example 12)
In the same polyamic acid solution as in Example 1, 2.0 times equivalent of acetic anhydride and 1.0 times equivalent of isoquinoline are added to the equivalent of amic acid, and the thickness becomes 20 μm after firing at a width of 1200 mm. The gel film was cast on an endless belt and dried at 100 ° C. to 140 ° C. for about 3 minutes so that the ratio of the remaining components was 62% by weight to obtain a self-supporting gel film. After that, it was peeled off from the belt. The peeled gel film was fired by being transported into a tenter furnace with a tension of 3.5 kg / m applied in the MD direction as a tension so as not to loosen when the gel film was transported. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the gel film was fixed without slack at both ends in the width direction with a pin width of 1100 mm. The gel film was 165 ° C. (first heating furnace; hot air oven), 300 ° C. (second heating furnace; hot air oven), 400 ° C. (third heating furnace; hot air oven), 515 ° C. (fourth heating oven). Baking stepwise with a heating furnace (far-infrared furnace) to form a polyimide film. At this time, the temperature spot in the first heating furnace was 60 ° C. The film was conveyed while shrinking and expanding the polyimide film in the TD direction so that the TD shrinkage ratio was 2.0 and the TD expansion ratio was 2.0. The step of reducing the both-end fixed end distance so as to be fixed so as to be substantially tensionless in the film TD direction ends before the film is inserted into the furnace, and the step of extending the both-end fixed end distance includes It was done in three furnaces.
The molecular orientation axis was measured with a molecular orientation meter MOA2012 at sites on both sides of 260 mm, 380 mm, and 460 mm based on the center of the polyimide film thus formed. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was found that a polyimide film in which the molecular orientation was controlled to be MORc 1.40 or less over the entire width of the film could be produced.

(Example 13)
In the same polyamic acid solution as in Example 1, 2.0 times equivalent of acetic anhydride and 1.0 times equivalent of isoquinoline are added to the equivalent of amic acid, and the thickness becomes 20 μm after firing at a width of 1200 mm. The gel film was cast on an endless belt and dried at 100 ° C. to 140 ° C. for about 3 minutes so that the remaining component ratio was 62% by weight to obtain a gel film having self-supporting properties. . After that, it was peeled off from the belt. The peeled gel film was fired by being transported into a tenter furnace with a tension of 3.5 kg / m applied in the MD direction as a tension so as not to loosen when the gel film was transported. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the gel film was fixed without slack at both ends in the width direction with a pin width of 1100 mm. The gel film was 165 ° C (first heating furnace; hot air oven), 300 ° C (second heating furnace; hot air oven), 400 ° C (third heating furnace; hot air oven), 515 ° C (fourth heating oven). Baking stepwise with a heating furnace (far-infrared furnace) to form a polyimide film. At this time, the temperature spot in the first heating furnace was 90 ° C. The film was conveyed while shrinking and expanding the polyimide film in the TD direction so that the TD shrinkage ratio was 2.0 and the TD expansion ratio was 2.0. Shrinkage in the TD direction was terminated before the film was inserted into the furnace, and expansion in the TD direction stretched the film in the 400 ° C. furnace.
Using the molecular orientation meter MOA2012, the molecular orientation axes of the portions on both sides of 260 mm, 380 mm, and 460 mm were measured using the center of the polyimide film thus obtained as a reference. The results are listed in Table 1. As a result of measuring the degree of molecular orientation, it was found that a polyimide film having a molecular orientation controlled to MORc 1.40 or less over the entire width of the film can be produced.

(Reference Example 1)
A polyimide film was produced under the same conditions as in Example 1 except that the temperature of the first heating furnace was 200 ° C. and the temperature spots in the first heating furnace were 110 ° C. Evaluation was performed using the same evaluation method as in Example 1. The results are listed in Table 2.

(Comparative Example 1)
The polyamic acid solution used in Example 1 and the same amounts of acetic anhydride and isoquinoline as in Example 1 were mixed, cast to an endless belt with a width of 1100 mm and a thickness of 20 μm after firing, 100 ° C. to 140 ° C. Then, it was dried with hot air so that the ratio of the remaining component was 54% by weight for about 3 minutes to obtain a gel film having self-supporting property. . After that, it was peeled off from the belt. The peeled gel film was baked by being transported in a tenter furnace with a tension of 8 kg / m applied in the MD direction as a tension so as not to loosen when the gel film was transported. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the gel film was fixed without slack at both ends in the width direction with a pin width of 1000 mm. 350 ° C. (first heating furnace; hot air oven), 400 ° C. (second heating furnace; hot air oven), 450 ° C. (third heating furnace; hot air oven), 515 ° C. (fourth heating oven) Baking stepwise with a heating furnace (far-infrared furnace) to form a polyimide film. At this time, the temperature spot in the first heating furnace was 45 ° C. At this time, temperature spots in the first heating furnace were within 30 ° C. The polyimide film was manufactured by conveying the inside of the heating furnace without changing the fixed end distance between both ends. The molecular orientation degree at 260 mm, 380 mm, and 460 mm sites was measured by MOA2012 with the center of the polyimide film thus obtained as a reference. The results are listed in Table 1.
When transported at the above ratio, the TD shrinkage rate is 0.0, and the TD expansion rate is 0.0.
As a result of this comparative example, it was revealed that when the TD shrinkage is 0.0 and the TD shrinkage is 0.0, a polyimide film having a large degree of molecular orientation at the end of the film is obtained.

(Comparative Example 2)
The polyamic acid solution used in Example 1 and the same amounts of acetic anhydride and isoquinoline as in Example 1 were mixed, cast onto an endless belt with a thickness of 20 μm after firing, a width of 820 mm, and 100 ° C. to 130 ° C. Then, it was dried with hot air so that the remaining component ratio was 60% by weight for about 5 minutes to obtain a gel film having self-supporting properties. After that, it was peeled off from the belt. The peeled gel film was fired by being transported into a tenter furnace with a tension of 2 kg / m applied in the MD direction as a tension so as not to loosen during the transport of the gel film. The gel film was fixed at both ends in the width direction to a pin sheet carrying a continuous film. At this time, the gel film was fixed without slack at both ends in the TD direction with a pin width of 800 mm (gel width was 800 mm). The gel film was prepared at 130 ° C. (first heating furnace; hot air oven), 260 ° C. (second heating furnace; hot air oven), 360 ° C. (third heating furnace; hot air oven), 450 ° C. (first heating oven). Fourth heating furnace; hot air oven) and 515 ° C. (fifth heating furnace; far-infrared furnace) were passed through and fired. At this time, the temperature spot in the first heating furnace was 90 ° C. The polyimide film was manufactured by conveying the inside of the heating furnace without changing the fixed end distance between both ends. The molecular orientation axis at a site of 260 mm and 380 mm was measured by MOA2012 with the center of the polyimide film thus obtained as a reference. The results are listed in Table 1.
When transported at the above ratio, the TD shrinkage rate is 0.0, and the TD expansion rate is 0.0.
As a result of this comparative example, it was revealed that when the TD shrinkage is 0.0 and the TD shrinkage is 0.0, a polyimide film having a large degree of molecular orientation at the end of the film is obtained.

Cross section of heating furnace Schematic diagram of polyimide film production equipment Schematic diagram for explaining the film gripping situation between polyimide film gripping devices

Explanation of symbols

17 Hot air spraying device 18 Furnace wall 19 Film transported in the furnace 20 Temperature measuring device in the furnace width direction 21 Temperature measuring device in the furnace width direction 22 Temperature measuring device in the furnace width direction 23 Temperature measurement in the furnace width direction Device 24 Temperature measuring device in width direction of furnace 40 Stepwise heating furnace 41 First heating furnace 42 Second heating furnace 43 Third heating furnace 44 Fourth heating furnace 45 Fifth heating furnace 46 Take-up device Winding process (Polyimide film winding device)
50 Gel film 51 Polyimide film 52 Gel film gripping member (gel film end gripping device)
53 Dies for application of polyamic acid solution 54 Substrates for application of polyamic acid solution 55 Gel film peeling site 61 Width of gel film between fixed ends at both ends

Claims (6)

In the process for producing a continuously produced polyimide film, at least the following (A) step of polymerizing polyamic acid (B) a composition containing polyamic acid and an organic solvent is cast and applied on a support, and then a gel film is formed. Forming step,
(C) Step of peeling off the gel film and fixing both ends (D) Step of conveying the inside of the heating furnace while fixing both ends of the film,
A method for producing a polyimide film comprising:
The step (D)
(D-1) a step of transporting the film so that the tension in the film width direction (TD direction) is substantially no tension;
(D-2) including a step of stretching the film in the TD direction;
And the said heating furnace consists of two or more several heating furnaces, The temperature spot of the width direction in a 1st heating furnace is 100 degrees C or less, The manufacturing method of an isotropic polyimide film characterized by the above-mentioned. The method for producing an isotropic polyimide film according to claim 1, wherein the step (D-1) is performed at an entrance of a heating furnace. The method for producing an isotropic polyimide film according to claim 2, wherein the heating furnace includes two or more heating furnaces, and the temperature of the first heating furnace is 300 ° C. or less. In the step (D-1), when the distance between the fixed ends at both ends is X and the width of the film between the fixed ends at both ends is Y, the tension in the TD direction is substantially such that X and Y satisfy the following formula. The method for producing an isotropic polyimide film according to any one of claims 1 to 3, wherein both ends are fixed so as to provide no tension.
20.0 ≧ (Y−X) / Y × 100> 0.00 In the step (D-2), Z is the distance between the fixed ends at both ends in the TD direction before stretching, and W is the distance between the fixed ends at both ends when the film is completely stretched in the furnace. The method for producing an isotropic polyimide film according to any one of claims 1 to 4, wherein the film is stretched in the TD direction so that W satisfies the following formula.
40.0 ≧ (W−Z) / Z × 100> 0.00 An isotropic polyimide film manufactured using the method for manufacturing a polyimide film according to claim 1.

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