JPS6274607A - Manufacture of polyimide film - Google Patents

Abstract

PURPOSE:To make the stable heat treatment of a film possible by eliminating the running of the film off from holding parts and the breakage of the film by a method wherein at least two sheets of the film, which is obtained by casting polyimide solution or polyamide acid solution over a base plate and drying, are simultaneously fed to a heat treatment furnace. CONSTITUTION:At least two sheets of dry film 3, which is obtained by drying polymer solution cast over a base plate in a drying furnace and, after that, peeling off the base plate, are simultaneously charged in a heat treatment furnace 1 so as to heat-treat the sheets under a state that both the edge parts 6 of the respective sheets of film are held in a state being in contact with each other. As a result, no phenomenon such as the running of the film off from edge holding parts 6, breakage of the film and the like during heat treatment occurs and the heat treatment of the film can be performed under stable state. On the other hand, the film portions 7 excluding the edge holding parts are strongly applied by tension in width direction due to the contractile force of the film and consequently no adhesion of the film occurs in the direction of the thickness of the film.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing a polyimide film.

[Conventional technology]

Conventionally, methods for obtaining polyimide heat-resistant films include:
Contains polyimide or polyamic acid, concentration 5-30
% solution by weight is cast onto a metal substrate, such as a stainless steel belt substrate, the solution is dried to form a dry film, and then both ends (edges) of the film are cast in a high temperature oven at 250-450°C. A method is used in which heat treatment is performed while holding and transporting the parts.

[Problem that the invention seeks to solve]

In such conventional methods, a solution casting drying device and a heat treatment device are installed in combination in -M, and the process from the casting process to the heat treatment process is integrated, and a polyimide film can be manufactured rationally. It is taken. Therefore,
If a problem such as film cutting occurs in one part of the process, it will affect the entire process, resulting in significant losses. Further, in the casting process, it is necessary that the dry film be easily peeled off from the base material. Furthermore, in the heat treatment process, shrinkage and elongation of the film in a high-temperature furnace, etc.
Due to complex behavior, phenomena such as the film coming off or tearing from the gripped ear are likely to occur.
Countermeasures are necessary.

In addition, in order to obtain the film thickness accuracy as targeted,
In particular, it is natural that it is necessary to improve the thickness accuracy of the casting solution. As described above, there are many points to be controlled in order to stably produce polyimide films, but among them, the most important is countermeasures against troubles in cutting the film during the heat treatment process. In this heat treatment step, the film placed in the heat treatment furnace first shrinks. This is because the dried film contains 10 to 40% by weight of residual solvent, and this residual solvent stale in the high-temperature atmosphere of the heat treatment furnace, resulting in a shrinkage force in the film. At this time, stress is concentrated on the lug-gripping portion of the film, making it easier to cut the film from this portion. In the case of a polyimide film using a polyamic acid film as a starting material, an imide ring-closing dehydration reaction of the amic acid occurs in a heat treatment furnace, and at this time the film shrinks again. That is, two large shrinkage forces act on the polyimide film during the heat treatment process, but it is necessary to resist these shrinkage forces and firmly maintain the lug gripping portion of the film so as not to cut the film. The present invention aims to provide a stable heat treatment method for polyimide films.

[Means for solving problems]

The method for producing a polyimide film of the present invention is characterized in that when a polyimide solution or a polyamic acid solution is cast onto a substrate and the film obtained by drying is heat-treated, at least two or more films are simultaneously supplied to a heat treatment furnace. shall be. At this time, in the heat treatment furnace, the tab gripping portions of each film are brought into contact with each other so strongly that they are in close contact with each other.

The polyimide film of the present invention has a structure represented by general formula (1).

Here, R5 represents a tetravalent aromatic group, and R2 represents a divalent aromatic group or an aliphatic group. Specifically, (1) is pyromellitic dianhydride, 3.3', 4. It is obtained as a reaction product of a tetracarboxylic dianhydride containing R1, such as 4'-biphenyltetracarboxylic dianhydride, and a diamine containing R2, such as 4,4'-diaminodiphenyl ether and para-phenylene diamine.

The polyimide solution of the present invention is a solution of a polymer having the above structure.

Further, the polyamic acid solution is a solution of polyamic acid CIIF) which is a precursor substance of polyimide (1).

Here, polyamic acid (II) is converted into polyimide by a dehydration reaction.

These polyimide or polyamic acid solutions include
Additives such as a lubricant, an antioxidant, a coloring agent, and a conductivity imparting material can be added as necessary. In addition, other heat-resistant resins such as polyether sulfone, polysulfone,
It is also possible to mix resins such as polyarylate, polyphenylene sulfide, and polyetherimide.

Examples of organic solvents used in the present invention include N, N-
Dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, p,-chlorophenol, m-chlorophenol, p-cresol, m-cresol , dimethyl sulfone, tetramethyl sulfone, dimethyl sulfoxide and the like are used alone or in combination of two or more. Furthermore, benzene,
It can also be used in combination with a non-solvent such as toluene, xylene, dioxane, cyclohexane, acetone, etc.

As a method of casting a polyimide solution or a polyamic acid solution onto a substrate, most commonly a method such as a die coater or a roll coater is used.

A metal substrate such as a stainless steel substrate is used as the substrate, but a plastic film can also be used as the substrate.

The polymer solution cast onto the substrate is dried in a drying oven and then peeled off from the substrate. The peeled film usually still contains some solvent. If the solvent is completely removed, the peelability of the film from the substrate will be extremely reduced, uneven peeling force will occur, and a film with a smooth surface will not be obtained.

The dry film is heat treated in the next step. In the present invention, at least two or more dry films are placed into a heat treatment furnace at the same time, and the films are heat treated while the films are gripped at both edges so as to be in close contact with each other. As for the gripping method,
There are methods such as using a clip or inserting a film into a pin, but the clip method has a large yield loss, so in most cases pins are used. When using pins, two or more dry films can be stacked and inserted into the pins at the same time, or the insertion positions can be shifted and the films can be inserted one after another. This method is shown in FIG.

By putting the dried films in a stacked state into the heat treatment furnace 1 in this way, phenomena such as the film coming off from the lug grip portion 6 or tearing do not occur during heat treatment, and the heat treatment is performed in a very stable state. be able to. In the case of the present invention, in order to grip two or more films at the same time,
At the ear gripping portion 6, the films adhere to each other and are strengthened.

On the other hand, in the film portion 7 other than the ear gripping portion, the film has a strong tension in the width direction due to shrinkage force, and is not adhered in the thickness direction. This phenomenon is clear from FIG.

The film that has passed through the heat treatment furnace is sequentially opened at its selvage gripping portions, and the tightly attached selvage portions are cut and removed, and then each film is separated and wound up to form a product.

In FIG. 1, the heat treatment furnace is of a horizontal type, but is of course not limited to this, and can be of various types, such as a vertical type or an inclined type.

When the present invention is considered from an economic point of view, it can be said that it is an extremely significant method. That is, according to the inventors' considerations,
Of the amount of heat consumed in a heat treatment furnace, the amount of heat received by the film itself is only 5 to 10%. other 90-9
5% of the energy is carried away with the hot air discharged outside the system or used to heat the heat treatment furnace body. Therefore, as in the present invention, even if the amount of dried film charged into the heat treatment furnace increases, the energy consumption of the entire heat treatment process increases only by a minimal amount. Also,
By implementing the present invention, it is possible to heat treat multiple films without making the heat treatment furnace particularly large.
Productivity is greatly improved.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

2 of polyamic acid obtained by equimolar reaction of pyromellitic dianhydride and 4.4 diaminodiphenyl ether.
A 0% by weight dimethylacetamide solution was cast onto a stainless steel belt using a slit die and dried at 120° C. to obtain a dry film with a thickness of 38 μm and a width of 600 mm.

This dry film had a solvent content of 28% by weight measured at 350°C. Next, two sheets of the above-mentioned dried film were stacked and put into a heat treatment furnace having a structure using pins as a gripping method, and a polyimide film of 26 μm was obtained at a maximum temperature of 400° C. At this time, the film did not come off or be cut from the gripped portion, making it possible to perform extremely stable processing.

Furthermore, when this film was finished in the heat treatment oven, the lug-gripping parts were in a state of strong adhesion, but the film parts other than the lug parts were not adhered at all and were as smooth as if they had been heat-treated as a single sheet. It was in a flat state.

On the other hand, when only one dried film was heat-treated under the same conditions, the film sometimes came off from the gripping portion and lacked stability.

〔Effect of the invention〕

The present invention has made it possible to produce polyimide films using extremely stable heat treatment means. Also,
According to the method of the present invention, a plurality of films can be heat treated in the same heat treatment furnace, so the method is extremely economical in terms of energy consumption and equipment costs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a method of introducing a dry film into a heat treatment furnace and a method of winding up the film after heat treatment, as an embodiment of the present invention. FIG. 2 is a diagram showing the state of the film gripping portion (lug) and other film portions during heat treatment in the practice of the present invention. Explanation of symbols 1 Heat treatment furnace 2 Pin (film gripping jig) 3 Dry film 4 Product film (unwinding)
(Take-up) 5 Bottle transport stand 6
Closely attached ear gripping part 7 Film parts other than the gripping part! ! fart:
Yumi゛・mu〉−°−＼ Agent Patent Attorney Kunihiko Wakabayashiz;':'−.

Claims (1)

[Claims] 1. A method for producing a polyimide film, characterized in that at least two or more films are simultaneously supplied to a heat treatment furnace when heat treating the film obtained by casting a polyimide solution or polyamic acid solution onto a substrate and drying it. .