JPH0834865A - Method for improving adhesion of polyimide film and polyimide film having improved adhesion - Google Patents

Abstract

(57) [Summary] [Objective] An object of the present invention is to provide a method for improving the adhesiveness of a polyimide film capable of obtaining an excellent effect of improving the adhesiveness that satisfies the recent demand for high adhesiveness, and a polyimide film having the improved adhesiveness. And [Structure] A polyimide film 18 is run at a constant line speed, an abrasive is sprayed onto the film surface from a sandblasting nozzle 22 of a sandblasting treatment device 12 to perform a surface treatment, and then the film is introduced into a corona discharge treatment device 14. By subjecting the surface to corona discharge treatment, an excellent effect of improving the adhesiveness of the polyimide film was stably obtained. Polyimide film surface-treated by such a method, unevenness is formed on the film surface to increase the adhesive area and the surface fragile layer and the contaminated layer are removed, and the surface is hydrophilized to provide excellent adhesiveness. It is shown.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the adhesiveness of a polyimide film and a polyimide film having an improved adhesiveness, more specifically, it does not affect the adhesive and can stably obtain an excellent adhesiveness improving effect. The present invention relates to a method for improving adhesion of a polyimide film, and a polyimide film having improved adhesion by the method for improving adhesion.

[0002]

2. Description of the Related Art Generally, a polyimide film is laminated with a metal foil (mainly a copper foil) using an adhesive, a vapor deposition method,
It is used as a base film of an FPC (flexible printed wiring board) after being processed into a laminated plate composed of a film layer and a metal layer by a plating method or a sputtering method.
However, the conventional polyimide film has a problem that the surface has poor adhesiveness, and as it is, it has been a cause of product defects.

By the way, the surface of the polyimide film is
As a result of casting a solution and conducting condensation polymerization to form a film in the film forming step, the surface shape of the film becomes smooth even when a stabilizer, an additive or the like is mixed. It is considered that one of the causes of the poor adhesion of the surface of the polyimide film is the smooth surface shape.
That is, if the surface shape of the film is smooth, the actual adhesive area between the film and the adhesive becomes relatively small, and it is considered that sufficient adhesive strength cannot be obtained.

Further, the surface of the polyimide film thus obtained by the solution casting method is predominantly bleeded with the stabilizers and additives mixed during the film formation, and the surface fragile layer (WBL: Weak Boundary Layer). ) Is formed, and in addition to this, the transfer to the surface of a low molecular weight polymer such as an oligomer as a WBL forming product may be accelerated in some cases. It is also conceivable that contaminants such as oil components generated in the equipment during the film forming process or existing in the atmosphere may adhere to the film to form a contaminated layer. Since these layers are easily peeled from the film surface, it is not possible to strongly adhere to the molecular scale of the film when adhered with an adhesive or the like, and the presence of such a layer also becomes a factor that inhibits the adhesiveness of the film. It is considered.

Therefore, for the purpose of improving the adhesiveness of the surface of the polyimide film, the film surface is subjected to a sandblasting treatment by blowing silica sand or other sand with compressed air or centrifugal force to treat the film surface with unevenness. Is used to increase the contact area between the film and the adhesive, and at the same time to remove the WBL and the contaminated layer on the film surface to improve the adhesiveness.

[0006]

However, the sand blast treatment is a method of forming irregularities on the surface of the polyimide film and expecting an increase in the adhesive strength due to the anchor effect with the adhesive, so that the strength of the polyimide film is reduced. It is necessary to limit to processing conditions that do not exist. For this reason, there is a limit to the improvement of the adhesive strength in the sandblast treatment, and there is a problem in that the adhesiveness that satisfies the recent demand for high adhesion cannot be obtained.

[0007] Therefore, the inventors of the present invention have solved the above-mentioned problems and improved the adhesiveness improving method and the adhesiveness of a polyimide film capable of obtaining an excellent adhesiveness improving effect of further improving the adhesiveness of the polyimide film. As a result of intensive studies for the purpose of providing such a polyimide film, the present invention has been achieved.

[0008]

Means for Solving the Problem The gist of the method for improving the adhesiveness of a polyimide film according to the present invention is that after performing a surface treatment by projecting an abrasive having a fine grain size onto the surface of the polyimide film at a high speed, Corona discharge treatment is applied to the surface.

Further, in the method for improving the adhesiveness of the polyimide film, the surface treatment for projecting the abrasive at a high speed is a sandblast treatment.

Next, the gist of the polyimide film having improved adhesion according to the present invention is that it is obtained by surface treatment by the method for improving adhesion of a polyimide film described in any of the above.

[0011]

The method for improving the adhesion of a polyimide film according to the present invention is characterized in that a surface treatment is performed by projecting an abrasive having a fine grain size onto the surface of the polyimide film at high speed, and then the surface is subjected to corona discharge treatment. By projecting an abrasive on the film surface at high speed, unevenness can be formed on the film surface to increase the contact area with the adhesive, and further, the WBL and the contamination layer formed on the film surface can be removed. it can. Further, by the corona discharge treatment, a hydrophilic group (hydroxyl group, carboxylic acid group, carbonyl group, etc.) can be introduced into the film surface to improve the hydrophilicity of the polyimide film surface.

Here, the causes of the low adhesion of the polyimide film are that the film surface is smooth and has a small adhesion area, that the adhesion on a molecular scale is not possible due to the presence of WBL and a contaminated layer, and the water repellency of the film surface is It is conceivable that the adhesive is not evenly adhered evenly. Therefore, the adhesiveness of the polyimide film is improved by removing these causes.

That is, the abrasives are projected onto the film surface at a high speed to form irregularities on the film surface, and the WBL and the contamination layer formed on the film surface are removed. However, by further performing corona discharge treatment after such treatment, unevenness is formed and the film surface from which the WBL and the contaminated layer are removed is hydrophilized, resulting in poor adhesion. The problem of water repellency on the film surface, which is another factor, can be solved. As a result, the adhesiveness of the film surface can be dramatically improved.

As a means for projecting the abrasive on the film surface at high speed, there is a method of spraying the abrasive on the film surface with compressed air or centrifugal force. Further, the compressed air method may be a dry method or a wet method. . Further, in the abrasive, silica sand, synthetic resin particles, glass beads, steel grid, copper slag, etc. are considered, but especially sandblasting using silica sand or other sand as the abrasive material,
It is preferable because the treatment conditions can be easily optimized and the surface treatment can be performed without lowering the strength of the film.

[0015]

The method for improving the adhesiveness of a polyimide film according to the present invention will be described below in detail with reference to the drawings. The polyimide film as used herein means a film in a broad sense including a thin film having a thickness of several μm to a sheet-like material having a thickness of several hundred μm, and the molecular structure of the polyimide film is not limited.

Such a method for improving the adhesiveness of a polyimide film is characterized in that a surface treatment is carried out by projecting an abrasive having a fine grain size onto the surface of the polyimide film at a high speed, and then the surface is subjected to corona discharge treatment. , Figure 1
The surface treatment apparatus 10 shown in FIG. The surface treatment device 10 performs a corona discharge treatment after performing a sandblast treatment, and includes a sandblast treatment device 12 and a corona discharge treatment device 14. Then, the polyimide film 18 delivered from the delivery device 16 is sprayed with an abrasive material on the film surface by the sandblasting device 12, and subsequently introduced into the corona discharge device 14 to be subjected to corona discharge treatment. The treated polyimide film 18 is wound around the winding device 20.

As the sand blast treatment device 12 and the corona discharge treatment device 14, conventionally known devices are used, and there is no particular limitation. Specifically, the sandblasting apparatus 12 sends a sandblasting nozzle 22 that blows an abrasive, an adjusting valve 24 that adjusts the blowout amount (blast amount) from the nozzle 22, a hopper 26 that stores the abrasive, and compressed air. Air chamber 28
The sand blast blowing nozzle 22 can be variably adjusted to adjust the angle and interval (blast angle, blast distance) with the polyimide film 18.
The sandblasting process is performed by setting the blasting amount, the blasting angle, and the blasting distance to optimal conditions. In addition, the corona discharge treatment device 14 includes a pair of highly insulated rolls 30 and 3
The corona electrode 32 is arranged in the vicinity of 0, and the corona electrode 32 is fixed to the frame 36 via a plurality of insulators 34, and when high energy is applied to the corona electrode 32, the corona electrode 32 is corona electrode 32. It is configured to cause a discharge. Note that reference numeral 38 is a transport roll, which is provided to allow the film 18 to travel favorably.

More specifically, the sandblasting process is
The surface treatment is performed by blowing the abrasive on the film surface with compressed air or centrifugal force. In the sandblasting apparatus 12, the abrasive is blown from the sandblast blowing nozzle 22 to remove the polyimide film 1.
The amount of blast of abrasive (blast amount) is adjusted by the adjusting valve 24.
The angle and the interval (blast angle, blast distance) between the nozzle 8 and the sandblast blowing nozzle 22 are adjusted by changing the nozzle 22. Then, the abrasive in the hopper 26 is blown out from the sandblast blowing nozzle 22 by the compressed air sent from the air chamber 28 and is blown onto the polyimide film 18, so that the sandblasting is performed under the optimized processing conditions.

Here, the treatment conditions in the sandblast treatment must be such that the abrasive or the object to be ground does not remain on the surface of the polyimide film after the treatment and the strength of the polyimide film does not decrease. The processing conditions can be appropriately set empirically.

Specifically, silica sand or other abrasives are used as the abrasive, and particularly, the particle diameter is 0.05 to 10.
It is preferable to use silica sand having a diameter of 0.5 mm, more preferably 0.5 to 1 mm. Further, the blast distance is preferably 100 to 300 mm, the blast angle is 45 to 90 degrees, and further 45 to
It is preferably 60 degrees. The blast amount is 1 to 1
It is preferably 0 kg / min. This is because the abrasive or the object to be ground is not left on the surface of the polyimide film by sandblasting, and the grinding depth is further controlled. The grinding depth is preferably 0.01 to 0.1 μm so that the strength of the film is not reduced.

Although the sandblasting apparatus 12 is configured to treat one side of the polyimide film, the sandblasting nozzles 22 are arranged on both sides of the polyimide film 18 so that both sides of the film can be treated. You may comprise.

By thus sandblasting the film surface, it is possible to form irregularities on the film surface and increase the contact area between the film and the adhesive. At the same time, the WBL and the contaminated layer are removed, and the adhesive and the film surface can be adhered on a molecular scale.

Next, the polyimide film 18 having irregularities formed on its surface by the above sandblasting process is introduced into the corona discharge treatment device 14, and the surface is subjected to corona discharge treatment.

In such a corona discharge treatment device 14,
The corona electrode 32 is formed to have a length to be subjected to corona treatment, in other words, approximately the width of a polyimide film, and the polyimide film 18 is formed between the highly insulated roll 30 and the linear corona electrode 32 in the roll 30. The corona electrode 32 running along the roll 30 is fixed to a frame 36 below the polyimide film 18 running along the roll 30 via a plurality of insulators 34. Therefore, by applying high energy to the corona electrode 32 to cause corona discharge,
Corona discharge treatment can be applied to the lower surface (sandblasted surface) of the polyimide film 18.

The power density of the corona discharge treatment at this time is 1
It is preferably from 00 to 700 W · min / m ² , and is appropriately set empirically depending on the type and thickness of the film.
In addition, the material of the electrode is not particularly limited and is appropriately selected and set empirically.

The corona discharge treatment may be performed on the surface of the film that has been subjected to the sandblast treatment, and as shown in FIG. 2, the corona discharge treatment in which the linear corona electrodes 32 are arranged opposite to the two rolls 30. The device 40 may perform corona discharge treatment on both sides of the film.

When corona discharge treatment is performed, in order to prevent wrinkles caused by thermal expansion of the film, the corona discharge treatment may be performed once or plural times after the film is stretched in the width direction. Further, following the corona discharge treatment, an ionized gas having ions having a polarity opposite to the polarity of static electricity charged on the film is sprayed on the film,
You may make it remove static electricity and remove the adhered fine powder at the same time.

By such a treatment step, the film surface can be oxidized to form hydrophilic functional groups such as hydroxyl group, carboxylic acid group and carbonyl group on the film surface, and the hydrophilicity of the film surface is improved.

In this way, after the sandblasting treatment, the corona discharge treatment is continuously carried out, whereby the surface of the polyimide film having irregularities formed and having an increased adhesive area can be further hydrophilized, which is very excellent. The effect of improving the adhesiveness can be obtained. That is, it is possible to realize a dramatic improvement in the adhesiveness by removing the factors considered to be the cause of the poor adhesiveness of the polyimide film.

The embodiments of the method for improving the adhesiveness of the polyimide film according to the present invention have been described above. In the sand blasting process, the abrasives are not blown onto the film surface by compressed air as described above, but are rotated at high speed. You may make it hit on the film surface by a car.

As the abrasive, abrasive grains having a hardness higher than that of the polyimide film may be used. As means for projecting the abrasive on the surface of the polyimide film at high speed, in addition to the above sand blasting treatment, shot blasting, shot peening, It is also possible to use a method such as liquid honing. Shot blasting or shot peening is a method in which spherical steel particles (shots) are used as abrasives instead of sand, and the hardness, particle size, etc. of steel particles are optimized in addition to the blast angle, blast distance, and blast amount. I'll do it. Liquid honing is a method in which these abrasives are jetted at a high speed together with a liquid. When the abrasives are steel particles, a mixture of these with water containing a rust preventive is used. With these methods, the same effect as the sandblast treatment can be obtained.

Further, the sandblast treatment and the corona discharge treatment may not be continuously performed as described above, but may be performed in separate steps. In addition, the present invention is not limited to these examples, and the present invention is based on the knowledge of those skilled in the art within the scope not departing from the gist thereof, and various improvements,
It can be implemented in a mode in which changes and modifications are made.

The polyimide film surface-treated by the method for improving the adhesion of the polyimide film is
Since the surface fragile layer and the contaminated layer have been removed along with the unevenness formed on the film surface, and since the surface has been stably hydrophilized, compared to the conventional polyimide film surface-treated only by sandblasting. It exhibits excellent adhesiveness and can firmly bond the film and the metal foil (copper foil or the like) using an adhesive. Further, the metal layer can be uniformly formed on the film surface by the vapor deposition method, the plating method, or the sputtering method. That is, the polyimide film having improved adhesion according to the present invention can be suitably used as a base film of FPC (flexible printed wiring board).

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

Example 1 Using the same processing apparatus as shown in FIG. 1, 4, 4 '
25 obtained by a known method from an aromatic diamine typified by diaminodiphenyl ether and an aromatic tetracarboxylic dianhydride typified by pyromellitic dianhydride.
Using a polyimide film having a thickness of μm, the sandblast treatment and the corona discharge treatment were continuously performed to perform the surface treatment of the polyimide film. The processing conditions were a line speed of 1.5 m / min, and sandblasting was performed using a pressure one-step type silica sand with a grain size of 0.1 to 1 mm, and the angle and interval between the blowing nozzle and the polyimide film were 45 each.
The degree is 100 mm. The amount of blowout is 6 kg /
set to min. The corona discharge treatment uses an aluminum electrode, the distance between the electrode and the film is 3 mm, and the power density is 2
It was processed at 00 W · min / m ² .

With respect to the polyimide film thus treated, the adhesive strength was evaluated by the following method. Using an acrylic adhesive ("Pyralux" manufactured by DuPont), the above treated film and a copper foil (electrolytic copper foil "3EC" 35 μm thick manufactured by Mitsui Mining & Smelting Co., Ltd.) were laminated to form 1
The adhesive is cured at 85 ° C for 1 hour, and FCCL
(Film / copper foil laminate) was produced. The obtained FCC
A sample was cut out so that the copper pattern width of L would be 3 mm, and a tensile tester ("S-100-" manufactured by Shimadzu Corporation)
C ") 90 at peel test speed of 50 mm / min
A peeling tensile test was performed. Table 1 shows the measurement results based on the average value of n = 5. All the fractured surfaces after peeling occurred at the film / adhesive interface.

[0037]

[Table 1]

Comparative Example 1 For comparison, the 25 μm thick polyimide film used in Example 1 was used without surface treatment, and the adhesive strength was evaluated in the same manner as in Example 1. Table 1 shows the measurement results based on the average value of n = 5. All the fractured surfaces after peeling occurred at the film / adhesive interface.

Comparative Example 2 For comparison, the polyimide film having a thickness of 25 μm used in Example 1 was sandblasted and used, and the adhesive strength was evaluated in the same manner as in Example 1. The sandblast treatment was performed under the same conditions as in Example 1. n
Table 1 shows the measurement results based on the average value of = 5. All the fractured surfaces after peeling occurred at the film / adhesive interface.

[0040]

EFFECT OF THE INVENTION In the method for improving the adhesion of a polyimide film according to the present invention, a surface treatment is performed by projecting an abrasive having a fine grain size onto the surface of the polyimide film at a high speed, and then a corona discharge treatment is applied to the surface. After forming irregularities on the film surface by such a method, a hydrophilic functional group can be further introduced on the film surface. As a result, the contact area between the film surface and the adhesive is increased, the WBL and the contamination layer are removed, and the adhesive can adhere to the film surface on a molecular scale, and the film surface is stably hydrophilic. And an excellent effect of improving the adhesiveness can be obtained. The polyimide film whose adhesiveness is improved by the method for improving the adhesiveness of such a polyimide film is such that the contact area of the film surface with the adhesive is increased and the film surface is stably hydrophilized, and further, the WBL and the contamination layer are Since it does not exist, it exhibits excellent adhesiveness and can be suitably used as a base film for FPC.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a surface treatment apparatus for carrying out a method for improving adhesion of a polyimide film according to the present invention.

FIG. 2 is an explanatory view showing another corona discharge treatment apparatus for performing the corona discharge treatment step in the present invention.

[Explanation of symbols]

 10; Surface treatment device 12; Sandblast treatment device 14, 40; Corona discharge treatment device 16; Feeding device 18; Polyimide film 20; Winding device 22; Sandblast blowing nozzle 24; Adjustment valve 26; Hopper 28; Air chamber 32; Corona electrode

Claims (3)

[Claims] 1. A method for improving the adhesiveness of a polyimide film, which comprises subjecting a surface of a polyimide film to high speed projection of an abrasive having a fine grain size, and then subjecting the surface to corona discharge treatment. 2. The surface treatment for projecting the abrasive at high speed comprises:
The method for improving adhesion of a polyimide film according to claim 1, wherein the method is sandblasting. 3. A polyimide film having improved adhesiveness, which is obtained by subjecting a surface of the polyimide film according to claim 1 or 2 to a method for improving adhesiveness.