JPH073055A - Method for treating surface of polyimide film - Google Patents

Abstract

PURPOSE:To readily obtain a film improved in adhesive strength by treating the surface of a polyimide film with an alkali solution and successively with an acid solution. CONSTITUTION:The surface of a polyimide film is treated with an alkali solution, preferably, an aqueous solution of potassium hydroxide or sodium hydroxide and successively with an acid solution such as aqueous solution of boric acid, hydrochloric acid, sulfuric acid, acetic acid, etc., to provide the objective film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for a polyimide film, and more particularly to a surface treatment method for a polyimide film for improving adhesive strength.

[0002]

2. Description of the Related Art Polyimide films are excellent in heat resistance and electric insulation, and therefore, magnet wires for electric equipment, flexible printed boards, flat cables,
Used for insulating tubes, spacers, etc. In use, it is generally necessary to adhere to a metal material such as copper or iron, especially a metal foil.

In order to improve the adhesive strength of the polyimide film, it has been attempted to mechanically roughen the adhered surface of the polyimide film by sandblasting, plasma treatment or treatment with an alkaline aqueous solution.
Practically satisfactory results have not been obtained. Further, after the alkali treatment, a treatment with a metal salt having a smaller ionization tendency than that of an alkali metal (Japanese Patent Publication No. 52-36778) and a treatment with a silane coupling agent after the alkali treatment (Japanese Patent Laid-Open No. 63- No. 68641) is known, but these methods are methods of substituting with a heavy metal or coating the activated surface with a silane coupling agent, and roughening or activating by alkali treatment. The formed surface is not directly utilized for adhesion with an adhesive.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to improve the drawbacks of the prior art. As a result, the polyimide film is subjected to alkaline treatment and then to acid treatment, so that the adhesive strength is significantly increased by a simple operation. It has been found to be improved.

[0005]

The present invention relates to a method for treating the surface of a polyimide film, which comprises treating with an alkali solution and then treating with an acid solution.

The polyimide film in the present invention is not limited to a polyimide film, but a film having an imide structure such as polyamideimide, polyesterimide, polyetherimide, polyamideesterimide, polyimidazopyrroloneimide, polyhydantoinimide, polyoxazoleimide, etc. Can be used.

As the alkaline solution, an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium alcoholate, potassium alcoholate, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide or the like is generally used. However, an aqueous solution of sodium hydroxide and potassium hydroxide is particularly preferable. The concentration of alkali in the alkaline solution and the temperature and time for treating the polyimide film are
Depending on the desired degree of treatment, the concentration is generally 0.1 to 50% by weight, preferably 3 to 30% by weight, the temperature is 5 to 45 ° C, preferably room temperature to 35 ° C.
The time is 3 to 60 seconds, preferably 5 to 30 seconds. The surface treatment of the polyimide film with the alkaline solution is performed by dipping or the like, and after the treatment, it is washed with water.

As the acid solution, an aqueous solution of boric acid, hydrochloric acid, sulfuric acid, acetic acid or the like is generally used. The acid concentration in the acid solution is not particularly limited, but is generally 0.1 to 30% by weight, preferably 3 to 10% by weight. The temperature and time of the acid treatment are not particularly limited, but generally the temperature is 5 to 4
5 ° C., preferably room temperature to 35 ° C., time 3-60
Seconds, preferably 5 to 30 seconds. The treatment with the acid solution is carried out by dipping or the like, followed by washing with water and drying.

The adhesive resin solution is applied to the surface of the polyimide film treated as described above, or after the adhesive resin film is laminated, it is laminated with a metal foil or the like and heated and optionally pressed to obtain a strong adhesive film. A laminate with adhesion is obtained. As the adhesive resin, a heat resistant adhesive such as polyimide, polybenzimidazole, polyester, polyurethane or epoxy resin is preferable.

[0010]

[Function] By treating the polyimide film with an alkali, the treated surface is roughened or activated, and by further treating with an acid, roughening or activation of the treated surface is further promoted, so that the adhesive strength is remarkably improved. It is thought to be done.

[0011]

Example 1 A 25 μm-thick polyimide film (Kapton, manufactured by Toray DuPont) was immersed in an aqueous solution of 10% by weight potassium hydroxide at 30 ° C. for 10 seconds and then washed with water. Then, it was immersed in a 3.8% by weight aqueous solution of boric acid at room temperature for 10 seconds, washed with water and dried.

On the treated surface of the polyimide film, a two-component urethane adhesive (TYFORCE AD-865,
TYFORCE CL-100M (manufactured by Dainippon Ink and Chemicals, Inc.) was mixed at a weight ratio of 100: 15, and applied so that the solid content was 18 g / m ^2, and then 100
It was dried with hot air at 1 ° C for 1 minute. Then 35 μm thick on top of it
Copper foil (manufactured by Nippon Mining Co., Ltd.) is overlaid, and the temperature is 100 ° C and the pressure is about 8.
It was pressed at 5 kg / cm ² for 3 seconds, aged at room temperature for 24 hours, and then cut into 30 mm width. This test piece is JIS-Z
According to the test method of 180 degree peeling of -0237, 2
A peeling test was performed at a speed of 00 mm / min. The test results are shown in Table 1.

[0013]

Example 2 The same operation as in Example 1 was performed except that a 10 wt% aqueous solution of hydrochloric acid was used instead of the 3.8 wt% aqueous solution of boric acid. The test results are shown in Table 1.

[0014]

Example 3 The same operation as in Example 1 was carried out except that a 10 wt% aqueous solution of sulfuric acid was used instead of the 3.8 wt% aqueous solution of boric acid. The test results are shown in Table 1.

[0015]

Comparative Example 1 A 25 μm thick polyimide film ((Kapton, manufactured by Toray DuPont) was immersed in a 10% by weight aqueous solution of potassium hydroxide at 30 ° C. for 10 seconds and then washed with water. Example 1 below
The same operation was performed. The test results are shown in Table 1.

[0016]

Comparative Example 2 A 25 μm thick polyimide film ((Kapton, manufactured by Toray Deyupon Co., Ltd.) was immersed in a 3.8 wt% aqueous solution of boric acid for 30 seconds at room temperature, washed with water and dried. Then, the same operation as in Example 1 was performed, and the test results are shown in Table 1.

[0017]

Comparative Example 3 The same operation as in Comparative Example 2 was performed except that a 10 wt% aqueous solution of hydrochloric acid was used instead of the 3.8 wt% aqueous solution of boric acid. The test results are shown in Table 1.

[0018]

COMPARATIVE EXAMPLE 4 The same operation as in Comparative Example 2 was carried out except that a 10 wt% aqueous solution of sulfuric acid was used instead of the 3.8 wt% aqueous solution of boric acid. The test results are shown in Table 1.

[0019]

COMPARATIVE EXAMPLE 5 The same operation as in Example 1 was carried out without the potassium hydroxide and boric acid treatments in Example 1. The test results are shown in Table 1.

[0020]

[Table 1]

[0021]

EFFECTS OF THE INVENTION By subjecting a polyimide film to an alkali treatment and then an acid treatment, a polyimide film having a significantly improved adhesive strength can be obtained by a simple operation, and its industrial value is great.

Claims (1)

[Claims] 1. A method for treating the surface of a polyimide film, which comprises treating the polyimide film with an alkali solution and then with an acid solution.