JP2008284701A - Method for producing polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably producing an extremely thin and lengthy film of a polyimide film excellent in heat resistance and mechanical properties. <P>SOLUTION: In the production method for forming a polyimide film 7.5 μm or below in thickness, by a film end part fixing type clip tenter of a process for imidating a polyimide precursor film, a grip in both side end parts in the width direction of the film, the polyimide precursor film is overlaid with a narrow film prepared separately, and a part overlaid with the narrow film is pinched with a clip and fixed to be gripped. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a polyimide film, and in particular, a clip tenter when a polyimide precursor film is subjected to high-temperature heat treatment to form a polyimide film during final heat treatment in producing a polyimide film having a thickness of 7.5 μm or less. It is related with the manufacturing method of the polyimide film which has the characteristics in the film holding | grip in the both-sides edge part of the width direction of a film in a formula (film conveyance) process part.

When producing a polyimide film, a polyimide precursor film (also referred to as a green film) in which a part of the solvent remains is imidized at a high temperature. In this case, drying and heat treatment are carried out by heating the polyimide precursor film while it is being transported. However, a film that has at least these solvents generally shrinks as it is dried. In such film transport / drying / heat treatment, as an apparatus for manufacturing a film by transporting the film in the stretched width direction by holding both ends in the width direction of the film with a large number of pins and clips, A film tenter type conveying device called a so-called tenter is known (see Patent Document 1).
In addition, it is also known to use a tenter type conveying device for manufacturing a polyimide film (see Patent Document 2).

The film conveying apparatus has been well known for a long time to be used for drying so as not to cause wrinkles in the drying process after dyeing the cloth. In addition to drying the cloth, it is also used for drying an undried plastic film by a solvent casting method while transporting it in the drying step. By using the film conveying apparatus, it is possible to suppress shrinkage of the film in the width direction due to heat during drying and heat treatment, and to prevent wrinkles due to shrinkage from occurring in the film after drying and heat treatment.
Film shrinkage occurs not only in the width direction of the film but in all directions, but the film transport direction is said to have a restraining effect on the shrinkage because the transport tension is acting, but the film thickness is extremely When the thickness is reduced, damage to the gripping portion due to shrinkage or the like also increases in the film transport direction. Thus, when the undried film is heat-treated, it is transported using a film tenter-type transport device, thereby ensuring the strength and flatness necessary for the dried and heat-treated film.

  Among the film tenter type conveying devices, the tenter type conveying device for the film that holds the film stretched in the width direction by biting a large number of pins along both side edges of the film was arranged in parallel A large number of pins are arranged on a pin sheet supported in a row by a pair of moving chains. This film tenter type transport device is simpler in structure than the film transport device such as the clip, or can be structured to reverse the transport conveyor path in the drying chamber. On the other hand, since the fine pieces of the film generate dust when the pins are bitten into the film, it is necessary to reduce the number of pins as much as possible. Moreover, when the shrinkage force of the film becomes large, there are problems such as the holes that have pinned the film surface break into long holes in the width direction of the film.

For these improvements, a method in which a film having a large tear strength is additionally used for reinforcement in the grip portion by the pin of the film has been proposed (see Patent Document 3), but the technique has a low tear strength. When processing a polymer resin film having a thickness of 50 to 150 μm with a film end fixed type tenter, particularly when stretched in the width direction, the sheet gripping portion at the film end has a higher tear strength than the film. In addition, the method is a method of stably tentering a polymer resin film having a low tear strength, in which the film and the reinforcing film that can be attached are overlapped and attached, and the reinforcing film is subjected to a force treatment. If the film to be processed is a polyimide film, not an ultra-thin polyimide film, it has such a strength that it does not need to be reinforced by the gripping part as long as it is such a thickness. The imidization is a high temperature treatment reaching 500 ° C.
Conventional film tenter type transport devices are prone to quality defects such as problems of breaking in the width direction of the film at the part where both ends of the film are sandwiched and caught by clips, and wrinkles, causing production loss. At the same time, the production efficiency was lowered, which was not satisfactory for the user.
In particular, when an extremely thin polyimide film is manufactured by a tenter type conveying method, the above-mentioned problem becomes remarkable and cannot be overcome by the conventional proposed technique.

Japanese Examined Patent Publication No. 39-029211. JP 09-188863 A Japanese Patent Laid-Open No. 11-254521

  The present invention is a polyimide film excellent in flatness and homogeneity that is suitable as a base material or insulating material for electronic parts, and excellent in heat resistance that does not change even when subjected to high-temperature treatment, and has a thickness of 7.5 μm or less. When an ultra-thin polyimide film is held and manufactured at both ends of the film by the clip tenter type conveying method, it is efficiently broken at the portion sandwiched by the clips in the width direction and longitudinal direction of the film. It aims at providing the manufacturing method of the polyimide film for eliminating the subject which the quality defect by performing etc. tends to generate | occur | produce.

That is, this invention is based on the following structures.
(1) A polyamic acid obtained by reacting an aromatic tetracarboxylic acid and an aromatic diamine is cast and dried to obtain a polyimide precursor film, and the polyimide precursor film is formed at both end portions in the width direction of the film. A polyimide film having a thickness of 7.5 μm or less is obtained by imidizing with a clip tenter method in which the film is conveyed in a state where the film is sandwiched between a plurality of clips and stretched in the width direction and / or the conveying direction. A thin film prepared separately is overlapped with a portion sandwiched between clips at both end portions in the width direction of the polyimide precursor film, with the film gripping at both end portions in the width direction of the polyimide precursor film. It is performed by sandwiching and fixing a portion where thin films are stacked with a clip. Method for producing Li imide film.
(2) The above-mentioned item 1, wherein the aromatic tetracarboxylic acid is at least one selected from pyromellitic acids and biphenyltetracarboxylic acids, and the aromatic diamine is at least one selected from p-phenylenediamines and diaminodiphenyl ethers. A method for producing a polyimide film.
(3) The manufacturing method of the polyimide film in any one of said 1 or 2 whose width | variety of a polyimide film is 500-10000 mm and length is 100-100000 m.
(4) The method for producing a polyimide film as described in any one of 1 to 3, wherein the narrow film is a polyimide precursor film, and the width is 20 to 60 mm.

  The method for producing a polyimide film according to the present invention is a clip tenter type processing unit (conveying device) for manufacturing a polyimide film having a thickness of 7.5 μm or less. By overlapping the film with the width and holding it with a clip, the film breaks, and it is possible to solve the problem that the yield and the quality defect are likely to occur. As a result, the quality of the manufactured polyimide film The above problems can be solved, contributing to the productivity of ultra-thin polyimide film production, and extremely effective industrially.

  The polyimide film of the present invention includes aromatic tetracarboxylic acids (anhydrides, acids, and amide bond derivatives are collectively referred to as classes hereinafter) and aromatic diamines (amines, and amide bond derivatives are collectively referred to as classes). A polyamic acid solution obtained by reacting with the same) is cast, dried and heat-treated to form a polyimide film. Examples of the solvent used in these solutions include polar organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, and N, N-dimethylacetamide.

The method for producing a polyimide film of the present invention is most preferably applied particularly when a casting film forming method using a solution of polyamide acid such as N-methyl-2-pyrrolidone or N, N-dimethylacetamide as a polyimide precursor is used. Can do.
The reaction between an aromatic diamine for obtaining a polyimide film, which can be preferably applied to the present invention, and an aromatic tetracarboxylic acid is carried out by reacting an aromatic diamine and an aromatic tetracarboxylic acid (anhydride) in a solvent. (Ring-opening) A polyamic acid solution is obtained by subjecting it to a polyaddition reaction, and then the polyamic acid solution is formed into a film and then dried to obtain a polyimide precursor film (also referred to as a green film). It is produced by imidization (heat treatment or dehydration condensation).

Although the polyimide film in this invention is not specifically limited, The combination of the following aromatic diamine and aromatic tetracarboxylic acid (anhydride) is mentioned as a preferable example.
A. A combination of an aromatic diamine having a diaminodiphenyl ether skeleton and an aromatic tetracarboxylic acid having a pyromellitic acid skeleton.
B. A combination of an aromatic diamine having a phenylenediamine skeleton and an aromatic tetracarboxylic acid having a biphenyltetracarboxylic acid skeleton.
C. One or more combinations of the above AB.

Examples of the aromatic diamine having a diaminodiphenyl ether skeleton in the present invention include 4,4′-diaminodiphenyl ether (DADE), 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, and derivatives thereof. Examples of the aromatic diamine having a phenylenediamine skeleton in the invention include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine and derivatives thereof, and these diamines are used in an amount of 70 mol% or more of the total diamine. It is preferable.
In the polyimide film of the present invention, the following aromatic diamines not limited to the above may be used in an amount of less than 30 mol% based on the total diamines.

  For example, 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, 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-aminobenzylamine, p-aminobenzylamine, 3,3′-diaminodiphenyl 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-aminophenoxy) 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) pheny ] Propane,

1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-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-aminophenoxy) -3-methylphenyl] propane, 2- [4- ( 4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3,5-dimethylphen Le] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane,
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-aminophenoxy) 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} phenyl] 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′-diphenoxybenzophenone, 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′-diamino-4,5′-dibiphenoxybenzophenone, 3,3′-diamino- 4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4′- Amino-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-biphenoxybenzoyl) 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 Some or all of the hydrogen atoms on the aromatic ring in benzonitrile and the aromatic diamine are halogen atoms, alkyl groups having 1 to 3 carbon atoms or alkoxyl groups, cyano groups, or some hydrogen atoms of alkyl groups or alkoxyl groups. Or the aromatic diamine etc. which were substituted by the C1-C3 halogenated alkyl group or alkoxyl group by which all were substituted by the halogen atom are mentioned.

As aromatic tetracarboxylic acids that can be preferably used in the polyimide film of the present invention, aromatic tetracarboxylic acids having a pyromellitic acid skeleton, that is, pyromellitic acid and anhydrides or halides thereof, and aromatic tetracarboxylic acids having a biphenyltetracarboxylic acid skeleton are used. Examples thereof include carboxylic acids, that is, biphenyltetracarboxylic acid and anhydrides or halides thereof, and these are preferably used in an amount of 70 mol% or more of the total acids.
Without being limited thereto, the following aromatic tetracarboxylic acid may be used if it is less than 30 mol% of the total acids.

これらのテトラカルボン酸は単独で用いてもよいし、二種以上を併用してもよい。

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

  The solvent used when polyamic acid is obtained by polymerizing aromatic diamines and aromatic tetracarboxylic acid anhydrides is particularly limited as long as it dissolves both the raw material monomer and the polyamic acid to be produced. Although not preferred, polar organic solvents are preferred, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide Hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, halogenated phenols and the like, among which N-methyl-2-pyrrolidone and N, N-dimethylacetamide are preferably applied. 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 mass, The amount is preferably 10 to 20% by mass.

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 30 minutes. 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 mass, more preferably 10 to 30% by mass, 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.
The reduced viscosity (ηsp / C) of the polyamic acid in the present invention is not particularly limited, but is preferably 1.5 dl / g or more, more preferably 2.0 dl / g or more, still more preferably 2.5 dl / g or more. preferable.
Moreover, you may perform superposition | polymerization by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction. Examples of the end capping agent include compounds having a carbon-carbon double bond such as maleic anhydride. The amount of maleic anhydride used is preferably 0.001 to 1.0 mol per mol of aromatic diamine.
Vacuum degassing during the polymerization reaction is effective in producing a good quality polyamic acid solution.
Furthermore, in order to obtain the polyimide film of the present invention, it is possible to remove bubbles and dissolved gas in the solution in advance by treatment such as decompression when casting and applying a polyamic acid solution described below onto the support. This is an effective process.

The support on which the polyamic acid solution is cast (applied) only needs to have smoothness and rigidity sufficient to form the polyamic acid solution into a film, and the surface is made of metal, plastic, glass, porcelain, etc. A certain drum or a belt-like rotating body may be used. A method using a polyimide film having moderate rigidity and high smoothness is also a preferred embodiment. Among them, the surface of the support is preferably a metal, more preferably stainless steel that does not rust and has excellent corrosion resistance. The surface of the support may be plated with metal such as Cr, Ni, or Sn. The surface of the support can be mirror-finished or processed into a satin finish as required. The air volume and temperature in drying may be appropriately selected and adopted depending on the difference in the support, and the polyamic acid solution can be applied to the support by casting from a nozzle with a slit, extrusion by an extruder, squeegee coating, reverse coating, die Including, but not limited to, coating, applicator coating, wire bar coating and the like, conventionally known solution application means can be used as appropriate.
In the imidization step, a ring closure (imidation) catalyst or a polyamic acid solution that does not contain a dehydrating agent is used for heat treatment to advance the imidization reaction (so-called thermal ring closure method) or a ring closure catalyst in the polyamic acid solution. And a chemical ring closure method in which a dehydrating agent is contained and an imidization reaction is performed by the action of the ring closing catalyst and the dehydrating agent.
The heat treatment temperature of the thermal ring closure method is preferably 150 to 500 ° C. If the heat treatment temperature is lower than this range, it is difficult to sufficiently close the ring, and if it is higher than this range, the deterioration proceeds and the film tends to become brittle. A more preferable embodiment includes a two-stage heat treatment step having an initial stage heat treatment and a subsequent stage heat treatment in which a heat treatment is carried out at 350 to 500 ° C. for 3 to 20 minutes after treatment at 150 to 250 ° C. for 3 to 20 minutes.
The timing for adding the ring-closing catalyst to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine, and betapicoline. Among them, heterocyclic tertiary amines are mentioned. At least one amine selected from is preferred. Although the usage-amount of a ring-closing catalyst with respect to 1 mol of polyamic acids does not have limitation in particular, Preferably it is 0.5-8 mol.
The timing of adding the dehydrating agent to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride. Among them, acetic anhydride, benzoic anhydride, etc. Acids or mixtures thereof are preferred. Moreover, the usage-amount of the dehydrating agent with respect to 1 mol of polyamic acids is not particularly limited, but is preferably 0.1 to 4 mol. When a dehydrating agent is used, a gelation retarder such as acetylacetone may be used in combination.

  Whether the thermal ring-closing reaction or the chemical ring-closing method, the polyimide film precursor film (also called green film) formed on the support is peeled off from the support before imidization. Is preferred in the present invention.

The thickness of the polyimide film in this invention is 7.5 micrometers or less, More preferably, it is 5 micrometers or less.
Conventionally, it has been difficult to industrially stably produce a long film of a polyamide film of 7.5 μm or less, particularly 5 μm or less, but the method for producing a polyimide film of the present invention does not solve this problem. It is. The thickness of the polyimide film can be easily controlled by the amount applied when the polyamic acid solution is applied to the support and the concentration of the polyamic acid solution.
The width | variety of the polyimide film in this invention is 500-10000 mm, for example, and length is 100-100000 m, and can be utilized also for continuous production of the component of an electronic device, a machine part, etc.

In the polyimide film of the present invention, it is preferable to improve the slipping property of the film by adding fine lubricant to the surface of the film by adding a lubricant to the polyimide.
As the lubricant, inorganic or organic fine particles having an average particle diameter of about 0.03 to 1 μm can be used. Specific examples include titanium oxide, alumina, silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium pyrophosphate, Examples include magnesium oxide, calcium oxide, and clay minerals.

In the present invention, when the polyimide precursor film is imidized with a film end fixed clip tenter, the film end gripping at both side end portions in the width direction of the film is performed on both sides of the film by a number of clips. In a polyimide film manufacturing method having a clip tenter type processing section that transports a film in a state of being stretched in the width direction and / or the transport direction, the film is processed at a portion that grips both side edges of the film with a clip. It is a manufacturing method which makes it essential to fix and hold onto a clip in a state where a thin film prepared separately from the polyimide precursor film is overlapped.
Here, the thin film prepared separately is not particularly limited, but preferably has the same quality as the polyimide precursor film to be processed, and the same polyamic acid solution is used separately from the polyimide film to be manufactured. Another polyimide precursor film is prepared by casting and drying, and is prepared by slitting in advance to a narrow width. The width of the narrow film is preferably 20 to 200 mm, particularly preferably 20 to 60 mm. The thickness of the thin film prepared separately from the polyimide precursor film to be treated is not particularly limited, but preferably the same thickness as the polyimide precursor film to be produced as a polyimide film. Preferably, it is 0.5 to 4 times the thickness of the polyimide precursor film, for example 5 to 20 μm. When the thickness is thin and less than 5 μm, the reinforcement effect of the overlay tends to be reduced, and when it is too thick and exceeds 20 μm, the overlay reinforcement effect may vary.

In the present invention, the clip portion of the end fixing tenter for heat-treating the polyimide film is not particularly limited as long as it is a known clip portion, but preferably uses a breathable heat-resistant material for the clip portion, The form and properties are not particularly limited, but preferably a breathable heat-resistant material that is a porous object or fiber aggregate having a thermal decomposition temperature of 400 ° C. or lower is used. Porous ceramics can be used as the breathable heat-resistant material in the present invention. There is no particular restriction on the material of the ceramic itself, and it is sufficient to use a single material or a plurality of materials such as alumina, calcia, magnesia, silica, etc. The porosity indicating the degree of porosity is preferably 30% or more by volume ratio, preferably 40% or more. Is more preferably 50% or more. When the degree of porosity is lower than this range, free emission of volatile components from the polymer film is prevented. On the other hand, if it exceeds 90%, the ceramic itself becomes brittle and becomes impractical. Similarly, as the porous body, foamed cement, gypsum, glass, metal, and other inorganic solids such as phosphates, carbonates, sulfates, and metal acid salts can be used.
As the breathable heat-resistant material in the present invention, an aggregate of inorganic fibers can be used. As the inorganic fibers used in the present invention, carbon fibers, alumina wool, glass wool, asbestos, various glass fibers, and the like can be used. These may be woven, non-woven, or thick like felt.
An aggregate of metal fibers can be used as the breathable heat-resistant material in the present invention. As the metal species, a stainless steel material having excellent corrosion resistance is preferable.
An aggregate of heat-resistant polymer fibers can be used as the breathable heat-resistant material in the present invention. As the heat resistant polymer fiber, aromatic polyamide fiber, polyimide fiber, polybenzoxazole fiber, polybenzothiazole fiber, polybenzimidazole fiber, polyimide benzoxazole fiber, or the like can be used.

It is more preferable that the tenter of the present invention formed by sandwiching the film end gripping with a plurality of clips has means for cooling so that the temperature of the gripping portion where the clip is in contact with the film is less than 180 ° C.
Hereinafter, the clip cooling means will be described in detail. A tenter using such a clip as a fixing means is called a clip tenter. Clip tenter clips are often combined with drive chains and installed as endless tracks. As for the drive chain of the clip tenter, a type that passes through the inside of the processing furnace is known for both reciprocation, and a type that the return path passes through the inside of the processing furnace is known. It is preferable to apply to. In the case of such a type, the entire apparatus can be made compact.
As shown in FIG. 3, in a processing chamber that receives a heat treatment or the like, a large number of clip blocks in which clips are arranged are arranged at both ends of the film, and these clips grip and convey both ends of the film. These clips run parallel to each other at both ends of the film, and are kept at a very high temperature for heat treatment of the film. At least in this processing chamber, the clips are also exposed to high temperature, and the film heat treatment is completed. It turns and grips the film again in its original position.
In the present invention, the cooling of the clip and the clip block is preferably performed between the return path of the drive chain on the inlet side of the processing furnace and the clipping zone.

In the conventional tenter type transfer device, when these clips grip the both ends of the film and start to transfer, one end is heated to a heat treatment temperature of 490 ° C., for example, 490 ° C., and there is no cooling means or temperature control means, and temperature variation is maintained at a high temperature. In the gripping of both ends of the film by the clip, the film gripping uniformity is difficult to be maintained, film thickness spots and cracks are likely to occur in the vicinity of the portion sandwiched between the clips, and the film breaks easily due to the expansion of the cracks. Furthermore, the distortion of the whole film increases and the film thickness unevenness increases. Therefore, in the present invention, a cooling means is provided at a position immediately before the clip is turned after the film heat treatment is finished and returns to the position where film gripping is started, and the clip is sufficiently cooled and temperature controlled at the time of starting film gripping. Therefore, uniformity of film gripping by the clip can be maintained, tearing in the vicinity of the clip, distortion reduction in the entire film, and reduction in film thickness unevenness can be achieved.
As a cooling means in the present invention, either air cooling or water cooling may be used, and a refrigerant other than air or water may be used. From the viewpoint of cooling efficiency, it is preferable to use a liquid refrigerant. Further, considering that the tenter itself is heated above the ignition point of a general organic solvent, it is most preferable to use a cooling means based on water cooling specifications. In order to prevent dew condensation in the vicinity of the cooling part, it is preferable to control the dew point of the cold air when air is used as the atmosphere and the refrigerant.
Furthermore, in the present invention, it is preferable to include a means for measuring the temperature of the clip portion and a control system for controlling the degree of cooling according to the measurement result. As the temperature measuring means, a known means such as a thermocouple or a radiation thermometer can be used. The control system may use normal negative feedback control.

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 (or N, N-dimethylacetamide) so that the polymer concentration was 0.2 g / dl was measured at 30 ° C. with an Ubbelohde type viscosity tube. (When the solvent used for preparing the polyamic acid solution was N, N-dimethylacetamide, the polymer was dissolved using N, N-dimethylacetamide and measured.)

2. The thickness of the polyimide film The thickness was measured using a micrometer (Millitron 1254D manufactured by Fine Reef).

3. Specimen obtained by cutting a polyimide film to be measured into a strip of 100 mm × 10 mm in the flow direction (MD direction) and the width direction (TD direction), respectively. It was. Using a tensile tester (manufactured by Shimadzu Corporation, Autograph (trade name), 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 of elasticity in each of the MD direction and TD direction, Tensile rupture strength and tensile rupture elongation were measured.

4). Film linear expansion coefficient (CTE)
The expansion / contraction rate was measured under the following conditions, and the range from 30 to 300 ° C. was divided at 15 ° C. intervals and obtained from the average value of the expansion / contraction rate / temperature of each divided range. The meanings of the MD direction and the TD direction are the same as described above.
Device name: TMA4000S manufactured by MAC Science
Sample length; 20mm
Sample width: 2 mm
Temperature rise start temperature: 25 ° C
Temperature rising end temperature: 400 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Argon

[Reference Example 1]
(Preliminary dispersion of inorganic particles)
7.6 parts by mass of amorphous silica spherical particles Seahoster KE-P10 (manufactured by Nippon Shokubai Co., Ltd.), 390 parts by mass of N-methyl-2-pyrrolidone, and the infusion part are austenitic stainless steel SUS316L And stirred for 1 minute at a rotation speed of 1000 rpm with a homogenizer T-25 basic (manufactured by IKA Labortechnik) to obtain a preliminary dispersion.
(Preparation of polyamic acid solution)
Nitrogen introduction pipe, thermometer, wetted part of vessel equipped with stir bar, and infusion pipe were replaced with nitrogen in reaction vessel made of austenitic stainless steel SUS316L, and then 200 parts by mass of 4,4′-diaminodiphenyl ether Put. Next, after 3800 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, 390 parts by mass and 217 parts by mass of pyromellitic dianhydride were added to the preliminary dispersion obtained above. When stirred for 5 hours at 0 ° C., a brown viscous polyamic acid solution A was obtained. The reduced viscosity (ηsp / C) was 3.7 dl / g.

[Reference Example 2]
(Preliminary dispersion of inorganic particles)
3.7 parts by weight of amorphous silica spherical particle Seahoster KE-P10 (manufactured by Nippon Shokubai Co., Ltd.), 420 parts by weight of N-methyl-2-pyrrolidone, the liquid contact part of the container, and the infusion pipe are austenitic stainless steel SUS316L And stirred for 1 minute at a rotation speed of 1000 rpm with a homogenizer T-25 basic (manufactured by IKA Labortechnik) to obtain a preliminary dispersion.
(Preparation of polyamic acid solution)
The wetted part of the vessel equipped with a nitrogen introduction tube, a thermometer, a stirring rod, and the infusion pipe were purged with nitrogen in the reaction vessel made of austenitic stainless steel SUS316L, and then 108 parts by mass of p-phenylenediamine was added. . Next, after 3600 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, 420 parts by mass and 292.5 parts by mass of 3,3 ′, 4,4 ′ -Diphenyltetracarboxylic dianhydride was added and stirred at 25 ° C for 12 hours to obtain a brown viscous polyamic acid solution B. The reduced viscosity (ηsp / C) was 4.5 dl / g.

(Production of narrow film)
The polyamic acid solution obtained in Reference Examples 1 and 2 was coated on the non-lubricant surface of polyethylene terephthalate film A-4100 (manufactured by Toyobo Co., Ltd.) using a comma coater (coating width 1240 mm), and 90 ° C. For 60 minutes. The polyamic acid film which became self-supporting after drying was peeled off from the support and cut at both ends to obtain green film A and green film B having a thickness of 8 μm and a width of 1200 mm, respectively.
Each of the green film A and the green film B was slit to prepare a narrow long slit film A and a narrow long slit film B having a width of 30 mm.

(Manufacture of polyimide film)
<Example 1>
The polyamic acid solution obtained in Reference Example 1 was coated on the non-lubricant surface of polyethylene terephthalate film A-4100 (manufactured by Toyobo Co., Ltd.) using a comma coater (gap: 150 μm, coating width: 1240 mm). And dried at 90 ° C. for 60 minutes. The polyamic acid film which became self-supporting after drying was peeled from the support and cut at both ends to obtain respective green films having a thickness of 8 μm and a width of 1200 mm.
The obtained green film is a clip shown in FIGS. 1 to 2 having a fiber diameter of 8 μm as a material of a portion in contact with the film while the narrow slit film A having a width of 30 mm is superposed on both end portions. Using a clip made of Naslon fiber felt (thickness of about 2 mm), equipped with a temperature measuring means for the clip gripping part by a radiation thermometer, and further provided with a cooling part as schematically shown in FIG. Pass through the tenter, clip sheet spacing is 1140mm, that is, each 30mm of green film is gripped with clips, the first stage is 170 ° C for 5 minutes, the second stage is 220 ° C for 5 minutes, the third stage is 480 ° C for 5 minutes Then, the imidization reaction was allowed to proceed. The temperature at the clip gripping part was controlled in the range of 160 ° C. plus or minus 5 ° C. Here, NASLON fiber is a stainless steel fiber manufactured by Nippon Seisen Co., Ltd.
The conveyance state of the film was good, and “clip disengagement” did not occur in the tenter. Also, almost no film tearing was observed even at the clip gripping portion at the tenter exit.
The obtained film was cooled to room temperature, portions with poor flatness at both ends of the film were cut off with a slitter, rolled up into a roll, and the polyimide film of Example 1 exhibiting brown color was obtained. Table 1 shows the properties of the obtained polyimide film.

The flatness and effective width of the film were defined as follows.
First, the obtained film was spread on a surface plate having a clean surface, and a portion where a space was left between the surface plate due to undulation at the end of the film was regarded as a portion having poor flatness. The ends of the film were not lifted from the surface of the platen, and both ends of the film were cut until the entire film was in close contact with the platen, and the film width at that time was defined as the effective width.
In addition, the tear at the clip part is determined by visually judging the film tear in the width direction and the longitudinal direction at the clip part at a portion of about 10 m from the top of the film, and those having 10 or more tear parts, About 10 to 3 pieces were evaluated as △, and 2 or less pieces as ◯.
The film peelability from the clip part is determined by visual evaluation of the state when the heat treatment (imidization) is completed and the film is peeled off from each clip by the roll, and the smooth peeling is good, and the film is caught on the clip. The case where it occurred was regarded as slightly defective, and the case where the film teared in the flow direction due to catching was regarded as defective.

<Example 2>
A polyimide film B was obtained in the same manner as in Example 1 except that the polyamic acid solution B obtained in Reference Example 2 was used and the narrow slit film B was overlapped on both side ends.
The evaluation was made in the same manner. The results are shown in Table 1.

<Comparative Example 1>
A polyimide film is produced in the same manner as in Example 1 except that the narrow-width long slit film A is processed using a green film having a thickness of 8 μm and a width of 1200 mm as it is without being overlapped on both ends. However, a long polyimide film that could be continuously evaluated could not be obtained.

<Comparative example 2>
A polyimide film is produced in the same manner as in Example 2, except that the narrow and long slit film B is processed by using a green film having a thickness of 8 μm and a width of 1200 mm as it is without being overlapped on both ends. However, a long polyimide film that could be continuously evaluated could not be obtained.

<Example 3>
The polyamic acid solution A was coated on the non-lubricant surface of polyethylene terephthalate film A-4100 (manufactured by Toyobo Co., Ltd.) using a comma coater (coating width 1240 mm), and dried at 90 ° C. for 60 minutes. A polyimide film was obtained in the same manner as in Example 1 while obtaining a green film having a thickness of 11.0 μm and a width of 1200 mm, and superposing the narrow slit film A having a width of 30 mm on both side ends on the obtained green film. Got. The evaluation was made in the same manner. The results are shown in Table 1.

<Example 4>
A polyimide film was obtained in the same manner as in Example 3 except that the polyamic acid solution B was used and the narrow slit film B was superposed on both side ends.
The evaluation was made in the same manner. The results are shown in Table 1.

<Example 5>
A polyimide film was obtained in the same manner as in Example 1 except that the polyamic acid solution A was used and the coating thickness of the comma coater was changed.
The evaluation was made in the same manner. The results are shown in Table 1.

<Example 6>
A polyimide film was obtained in the same manner as in Example 1 except that the polyamide acid solution B was used and the coating thickness of the comma coater was changed.
The evaluation was made in the same manner. The results are shown in Table 1.

<Comparative Example 3>
A polyimide film in the same manner as in Example 3 except that the thin long slit film A is processed by using a green film having a thickness of 5.0 μm and a width of 1200 mm as it is without being overlapped on both ends. However, a long polyimide film that could be continuously evaluated could not be obtained.

<Comparative Example 4>
A polyimide film in the same manner as in Example 4 except that a thin film having a thickness of 5.0 μm and a width of 1200 mm is used as it is without superimposing the narrow slit film B on both ends. However, a long polyimide film that could be continuously evaluated could not be obtained.

  As described above, the film gripping at both ends in the width direction of the film in the film end fixing type clip tenter in the imidizing step of the present invention is a thin film different from the polyamic acid film to be imidized. By overlapping and fixing with clips, it is possible to eliminate the problem of breakage in the longitudinal and width directions of the film, the occurrence of curling, and quality defects due to wrinkles and distortions. It is possible to stably produce a long ultrathin polyimide film having a thickness of 7.5 μm or less. A long ultrathin polyimide film having a thickness of 7.5 μm or less can be used as a part of an electronic device or a machine part.

The side surface outline of the clip part in the clip tenter of the present invention is shown. The front outline of the clip part in the clip tenter of the present invention is shown. The whole outline in the clip tenter of the present invention is shown.

Explanation of symbols

1. Clip movable part Roller 3. Clip gripping part 4. Rotating shaft 11. Cooling unit 12. Heat treatment zone 13. Clip drive chain

Claims (4)

  A polyamic acid obtained by reacting an aromatic tetracarboxylic acid and an aromatic diamine is cast and dried to obtain a polyimide precursor film, and the polyimide precursor film is coated with a large number of both end portions in the width direction of the film. A polyimide film manufacturing method for obtaining a polyimide film having a thickness of 7.5 μm or less by imidization by a clip tenter method in which a film is conveyed in a state of being gripped by being clipped and stretched in a width direction and / or a conveying direction The film holding at both ends in the width direction of the polyimide precursor film is overlapped with a thin film prepared separately on the portion sandwiched between the clips at both ends in the width direction of the polyimide precursor film. A polyimide film characterized in that it is performed by sandwiching and fixing the overlapped film with a clip. Manufacturing method of de film.   The polyimide film according to claim 1, wherein the aromatic tetracarboxylic acid is at least one selected from pyromellitic acids and biphenyltetracarboxylic acids, and the aromatic diamine is at least one selected from p-phenylenediamines and diaminodiphenyl ethers. Manufacturing method.   The width | variety of a polyimide film is 500-10000 mm, and length is 100-100000 m, The manufacturing method of the polyimide film in any one of Claim 1 or 2.   The method for producing a polyimide film according to any one of claims 1 to 3, wherein the narrow film is a polyimide precursor film, and the width is 20 to 60 mm.

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