JPH0848795A - Novel polyimide film and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Purpose] A polyimide film with a thickness of more than 125 μm.
It retains mechanical strength and has excellent punchability,
It is an object of the present invention to provide a novel polyimide film which does not require a laminating step for use as a stiffener. [Structure] A polyamic acid polymer solution is formed into a film, the film of the polyamic acid polymer is fixed to a support frame, and the temperature is gradually raised, and the maximum firing temperature is 200 to 450 ° C.
By heating for 5 minutes or more, a novel polyimide film having a thickness of 125 μm or more and a tear propagation resistance of 0.3 g / μm or more was produced. Such a polyimide film has excellent mechanical strength and punchability,
One piece of polyimide film can be suitably used as a stiffener, and the laminating step can be omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel polyimide film and a method for producing the same, and more particularly, it is suitable as a reinforcing plate (stiffener) for a connector portion and a component mounting portion of a flexible printed wiring board (hereinafter referred to as FPC). The present invention relates to a novel polyimide film that can be used for and a manufacturing method thereof.

[0002]

2. Description of the Related Art FPC is a flexible and thin base film on which a circuit pattern is formed.
The surface of the FPC has a basic structure, and in recent years, the FPC has been widely used in the field of electronic technology due to its excellent functions such as flexibility. Further, due to recent progress in mounting technology, the demand for high-density mounting has rapidly increased, and component mounting FPCs for directly mounting components on FPCs have been widely used. In such a component mounting FPC, a reinforcing material is lined or an insulating film is thickened.

From the viewpoints of production and use, FPC base films and cover lay films have required properties such as mechanical properties, electrical properties, chemical resistance, heat resistance, and environment resistance, and these are sufficient. At present, polyimide film is most widely used as a durable material. Polyimide films are also widely used as stiffeners for component mounting FPCs.
It is formed to a thickness of about 0 μm and used.

By the way, the polyimide film is 4,
An aromatic diamine typified by 4'-diaminodiphenyl ether and an aromatic tetracarboxylic dianhydride typified by pyromellitic dianhydride were polymerized in an organic solvent to obtain a polyamic acid polymer solution. After that, the polyamic acid polymer solution is formed into a film, which is thermally and / or
Alternatively, it can be obtained by chemically performing dehydration ring closure, that is, by imidization. Specifically, a polyamic acid polymer solution,
Alternatively, a solution obtained by adding a stoichiometric or higher amount of dehydrating agent and a catalytic amount of a tertiary amine is cast or applied onto a drum or an endless belt to form a film, and the film is formed at a temperature of 150 ° C or lower. After drying for about 5 to 90 minutes, a coating film of a polyamic acid polymer having self-supporting property is obtained. Then, this is peeled off from the support to fix the end portion, and gradually heated to about 100 to 500 ° C, and the maximum firing temperature is 450 to 550 ° C.
By heating for about 5 minutes, the polyamic acid is converted to polyimide, and a polyimide film is obtained.

However, with such a method, the thickness is 125
When a polyimide film having a thickness of μm or more is produced, mechanical strength becomes poor, and there is a problem in punchability such as layer breakage on the end face after punching. Therefore, when a thick polyimide film of about 200 μm is required as in the case of using as a stiffener, usually two sheets (for example, 50 μm and 125 μm) are used to maintain mechanical strength.
It is used by adhering the polyimide film of m) with an adhesive. However, the process of laminating two polyimide films in this way is time-consuming and costly, and easily peels off from the adhesive and cracks in the adhesive layer are observed on the end face after punching. It had a problem of punchability.

Therefore, the present inventors have solved the above-mentioned problems and made a polyimide film having a thickness of more than 125 μm, which retains mechanical strength and is excellent in punching property, so that a laminating step is unnecessary for use as a stiffener. As a result of intensive studies, the present invention has been accomplished with the aim of providing a novel polyimide film.

[0007]

The gist of the novel polyimide film according to the present invention is that the thickness is 125 μm.
m or more and the tear propagation resistance is 0.3 g / μm or more.

The gist of the novel method for producing a polyimide film according to the present invention is that a polyamic acid polymer solution is formed into a film and then thermally and / or chemically imidized to obtain a thickness of 125 μm. In the above method for producing a polyimide film, the firing conditions are that the maximum firing temperature is 200 to 450 ° C. and the heating time is 5 minutes or more.

[0009]

The novel polyimide film according to the present invention has a thickness of 125 μm or more and a tear propagation resistance of 0.3 g /
It is characterized by having a thickness of at least μm, and is a polyimide film that retains mechanical strength. Further, it has excellent punching property, and one polyimide film can be suitably used as a stiffener without sticking two polyimide films with an adhesive as in the conventional case. Therefore, the bonding step can be omitted for use as a stiffener, and peeling from the adhesive does not occur.

Further, in order to produce such a novel polyimide film, the firing conditions are set to be lower and longer than those of the conventional one, the maximum firing temperature is set to 200 to 450 ° C., and the heating time is set to 5
When the maximum firing temperature is high, the polyimide film having a thickness of 125 μm or more cannot maintain the mechanical strength and the punchability becomes poor. That is, by obtaining a polyamic acid polymer coating film by a known method, fixing the coating film on a supporting frame, and then gradually raising the temperature and heating at a maximum firing temperature of 200 to 450 ° C. for 5 minutes or more. It is possible to obtain a novel polyimide film according to the present invention, which has excellent mechanical strength with a tear propagation resistance of 0.3 g / μm or more and is excellent in punchability even when the thickness of the polyimide film is more than 125 μm. Of.

[0011]

EXAMPLES Examples of the novel polyimide film and the method for producing the same according to the present invention will be described below.

The polyimide film applied to the present invention comprises an aromatic diamine typified by 4,4'-diaminodiphenyl ether and an aromatic tetracarboxylic dianhydride typified by pyromellitic dianhydride as an organic solvent. After polymerization in the solution to obtain a polyamic acid polymer solution, if necessary, a dehydrating agent (curing agent) is mixed and processed into a film by a casting method or the like, and the solvent is dried by heating and conversion to a polyimide. Go and get.

More specifically, the polyamic acid polymer solution is obtained by a conventionally known method, and as the aromatic diamine, diaminodiphenyl ether, paraphenylenediamine, bis (3-aminophenoxyphenyl) is used.
Propane etc. can be mentioned, and other various diamine components can be used. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride and biphenyltetracarboxylic dianhydride, and various other acid anhydride components can be used. These diamine component and acid anhydride component are gradually added in an organic solvent until substantially all of the acid anhydride component and all of the diamine component are equimolar, and polymerized by sufficient stirring to produce a polyamic acid polymer. Although a solution is obtained, the diamine component and the acid anhydride component may be used alone, or two or more kinds may be mixed and used for copolymerization.

A polyimide film can be obtained by forming the polyamic acid polymer solution obtained by the above method into a film and converting the polyamic acid into a polyimide by dehydration ring closure (imidization). Specifically, there are two types of methods, a thermal method of thermally dehydrating and a chemical method using a dehydrating agent. Either method may be used, and the chemical method and the thermal method are used in combination. May be.

Specifically, the polyamic acid polymer solution is cast or coated on a drum or an endless belt to form a film, and the film is dried at a temperature of 150 ° C. or lower for about 5 to 90 minutes and self-supported. A coating film of polyamic acid polymer having properties is obtained. Then, peel off this from the support to fix the end, gradually heat to imidize, and after cooling, remove from this, a polyimide film can be obtained. By setting the firing temperature to 200 to 450 ° C. and heating for 5 minutes or more,
Therefore, the novel polyimide film according to the present invention can be obtained. When a polyimide film having a thickness of more than 125 μm is produced, sufficient mechanical strength such as tensile strength and elongation is obtained at a maximum firing temperature of less than 200 ° C., regardless of the length of firing time (heating time). I can't. When the maximum firing temperature is 450 ° C, a film having a tear propagation resistance of 0.3 g / μm or more cannot be obtained if the firing time is less than 5 minutes, but if the firing time is 5 minutes or more, the tear propagation resistance is increased. A film having a resistance of 0.3 g / μm or more can be obtained. Furthermore, the maximum firing temperature is 45
If the temperature exceeds 0 ° C, a film having a tear propagation resistance of 0.3 g / μm or more cannot be obtained regardless of the length of baking time. The firing time is set depending on the thickness of the film to be obtained and the firing temperature, but it is usually preferable to heat for 5 to 10 minutes.

The novel polyimide film according to the present invention obtained by such a method has a thickness of 125 μm or more,
In addition, it exhibits excellent mechanical strength with a tear propagation resistance of 0.3 g / μm or more, and has excellent punchability. Therefore, such a polyimide film can be preferably used as a stiffener with one piece of polyimide film,
The laminating step can be omitted. Although a polyimide film having a thickness of 125 μm or less may be produced, in this case, a polyimide film having sufficient mechanical strength can be obtained even under conventional heating conditions. In particular, a polyimide film having a thickness of 150 μm to 250 μm has high availability as a stiffener and can be preferably used.

Although one embodiment of the present invention has been described above, the present invention can be implemented in other modes. For example, in the above examples, the polyamic acid is imidized by a thermal method, but in the polyamic acid polymer solution,
A chemical method and a thermal method are used in combination, such as adding a dehydrating agent in a stoichiometric amount or more and a catalytic amount of a tertiary amine to form a polyamic acid polymer coating film, and then heating under the above conditions. May be. Industrially, a method of using a chemical method and a thermal method in combination is preferable because it is excellent in handleability and mechanical properties such as elongation and tensile strength of a polyimide film to be formed are excellent.

Further, the novel method for producing a polyimide film in the present invention comprises molding a quasi-imide material such as polyamide-imide or polyether-imide, in addition to the polyimide film obtained by imidizing the above polyamylamidic acid polymer. The novel polyimide film in the present invention is a concept including these. Further, the polyimide film used in the present invention may be formed by adding various fillers, reinforcing agents, etc., and is not limited at all. In addition, the present invention can be carried out in a mode in which various improvements, changes and modifications are made based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A polyamic acid polymer solution was obtained by a known method using 4,4′-diaminodiphenyl ether as an aromatic diamine and pyromellitic dianhydride as an aromatic tetracarboxylic dianhydride. It was Then, the polyamic acid polymer solution was cast-coated on a glass plate, dried at about 100 ° C. for about 8 minutes, the coating film of the polyamic acid polymer was peeled off from the glass plate, and the coating film was fixed to a supporting frame. . After that, the temperature is gradually raised, and the dehydration ring closure (imidization) is performed by heating under the conditions of a maximum firing temperature of 200 ° C. and a heating time of 5 minutes, 7 minutes, and 10 minutes, respectively, and a thickness of 150 μm, 200 μm, 25
A thick polyimide film of 0 μm was obtained.

Regarding the polyimide film thus produced, tear propagation resistance (ASTM D1938),
Edge tear resistance (ASTM D1004) was measured to evaluate mechanical strength. Also, observe the state of the end surface after punching,
The quality of punchability was evaluated. Table 1 shows the evaluation results.

[0022]

[Table 1]

Example 2 A coating film of a polyamic acid polymer obtained in the same manner as in Example 1 was fixed on a support frame. Then, the maximum firing temperature is 45
A thickness of 15 °
Thick polyimide films of 0 μm, 200 μm, and 250 μm were obtained. In the same manner as in Example 1, the mechanical strength and punchability of the polyimide film thus produced were evaluated. Table 2 shows the evaluation results.

[0024]

[Table 2]

Comparative Example 1 For comparison, a coating film of the polyamic acid polymer obtained in the same manner as in Example 1 was fixed on a supporting frame. Then, it was heated at a maximum firing temperature of 450 ° C. for 3 minutes for dehydration ring closure (imidization) to obtain thick polyimide films having a thickness of 150 μm, 200 μm, and 250 μm. In the same manner as in Example 1, the mechanical strength and punchability of the polyimide film thus produced were evaluated. The evaluation results are shown in Table 3.

[0026]

[Table 3]

Comparative Example 2 For comparison, a coating film of the polyamic acid polymer obtained in the same manner as in Example 1 was fixed on a support frame. Then, the maximum firing temperature is 550 ° C., and the heating time is 5 minutes, 7 minutes, 1
By heating at the conditions of 0 minutes to cyclodehydration (imidization), to give a thickness 150 [mu] m, 200 [mu] m, the thickness thereof polyimide film 250 [mu] m. In the same manner as in Example 1, the mechanical strength and punchability of the polyimide film thus produced were evaluated. The evaluation results are shown in Table 4.

[0028]

[Table 4]

Comparative Example 3 For comparison, dehydration ring closure (imidization) was carried out by heating at a maximum firing temperature of 500 ° C. for a heating time of 1 minute, 2 minutes, and 3 minutes, and thicknesses of 50 μm, 75 μm, and 1
A 25 μm polyimide film is prepared and 50 μm and 125 μm, and 75 μm and 125 are made by using a commercially available adhesive.
A μm polyimide film was laminated. The mechanical strength and punchability of the laminated polyimide film thus produced were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 5.

[0030]

[Table 5]

As is clear from Tables 1 to 5, when a polyimide film having a thickness of more than 125 μm is produced, the maximum firing temperature exceeds 450 ° C. or 450 ° C.
However, if the heating time is less than 5 minutes, only a film having poor mechanical strength and punchability can be obtained. However, by setting the firing conditions to be lower and longer than the conventional conditions, that is, the maximum firing temperature. It can be seen that a polyimide film excellent in mechanical strength and punching property can be obtained by heating at a temperature of 200 to 450 ° C. for a heating time of 5 to 10 minutes. Further, although the conventional laminated polyimide film is excellent in mechanical strength, cracks and cracks in the adhesive layer are observed on the end surface after punching, which shows that there is a problem in punching property.

[0032]

As described above, in the novel polyimide film according to the present invention, the firing conditions for imidizing the polyamic acid are such that the maximum firing temperature is 200 to 450 ° C. and the heating time is 5 minutes or more. Obtained with a thickness of 125
A polyimide film having an excellent mechanical strength of not less than μm and a tear propagation resistance of not less than 0.3 g / μm and excellent punchability can be realized. That is, the novel polyimide film is a polyimide film having a thickness of 125 μm or more, which is excellent in mechanical strength and punchability, and realizes a polyimide film which can be suitably used as a stiffener. Further, when such a new polyimide film is used, the laminating step can be omitted, so that the manufacturing process of the FPC can be simplified, and since one polyimide film is used, it can be peeled off from the adhesive and then punched out. There is no visible cracking of the adhesive layer on the end face of the.

Claims (2)

[Claims] 1. A novel polyimide film having a thickness of 125 μm or more and a tear propagation resistance of 0.3 g / μm or more. 2. In a method for producing a polyimide film having a thickness of 125 μm or more obtained by forming a polyamic acid polymer solution into a film and then thermally and / or chemically imidizing the film, the firing conditions are the maximum firing temperature. Is 200-4
A novel method for producing a polyimide film, which comprises heating at 50 ° C. for 5 minutes or more.