JPH0834870A - Method for improving adhesion of polyimide film and polyimide film having improved adhesion - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a method for improving the adhesiveness of a polyimide film and a polyimide film having improved adhesiveness, by which the surface of the film is made stable hydrophilic and an excellent adhesiveness improving effect is obtained. And [Structure] A polyimide film 20 is run at a constant line speed, a coupling agent solution is applied by a bar coater 24 immersed in a coupling agent tank 26, and then the solution adhering to the film surface is dried in a drying oven 14. After that, by introducing into the corona discharge treatment device 16 and performing the corona discharge treatment, a stable and excellent effect of improving the adhesiveness of the polyimide film was obtained. A polyimide film surface-treated by such a method has a film of a coupling agent formed on the surface of the film to have a uniform surface property, and since the surface is subjected to corona discharge treatment, the film surface is compatible with the adhesive. It has a hydrophilic group as well as a hydrophilic affinity group and exhibits excellent adhesiveness.

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 improved adhesiveness. More specifically, it has a stable and excellent adhesiveness improving effect without affecting the adhesive. 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. Therefore, for the purpose of improving the adhesiveness on the surface of the polyimide film, it is generally used after being subjected to corona discharge treatment.

That is, it is considered that the poor adhesion of the surface of the polyimide film is due to the high water repellency of the film surface. Therefore, the corona discharge treatment is applied to the film surface to impart hydrophilicity to the surface. It improves the adhesion. The reason why the surface hydrophilicity is increased by the corona discharge treatment is considered to be that the film surface is oxidized and a hydrophilic functional group such as a hydroxyl group, a carboxylic acid group or a carbonyl group is newly generated on the film surface.

[0004]

By the way, a polyimide film can be obtained by condensation polymerization by a solution casting method, and when its surface is mixed with stabilizers, additives, etc.,
These preferentially bleed and surface fragile layer (WBL; We
ak Boundary Layer)
It is known academically that the migration of low molecular weight polymers such as oligomers to the surface as BL-forming products may be accelerated. 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.

It is conceivable that the formation of these layers may determine the surface characteristics of the polyimide film and may be a factor that hinders its adhesiveness. Further, when the WBL or the contaminated layer is formed on the surface of the polyimide film in this manner, when the corona discharge treatment is applied from above the layer, the surface to which hydrophilicity is imparted by the corona discharge treatment is fragile and easily peeled off. Therefore, the adhesive strength cannot be essentially improved.

Particularly, the surface characteristics of the polyimide film are remarkably changed depending on the conditions during film formation.
For example, there are cases where the formation of the WBL or the contaminated layer becomes remarkable or not depending on the conditions at the time of film formation, even if the films having the same characteristics are manufactured at the same time. That is, the surface properties of the polyimide film become non-uniform, and even if the surface of the polyimide film is subjected to corona discharge treatment, sufficient treatment effects may not be obtained, and it is difficult to achieve stable surface modification. There is.

[0007] Therefore, the present inventors provide a method for improving the adhesiveness of a polyimide film which can solve the above-mentioned problems and stably obtain an excellent adhesiveness improving effect, and a polyimide film having improved adhesiveness. As a result of intensive studies for the purpose, the present invention has been achieved.

[0008]

The gist of the method for improving the adhesion of a polyimide film according to the present invention is to attach a coupling agent solution to the surface of a polyimide film, then dry the solution, and dry the solution. Corona discharge treatment is applied to the film thus made.

In the method for improving the adhesiveness of the polyimide film, the concentration of the coupling agent solution is
0.005 to 30 wt%, more preferably 0.01 to 5 wt%
%.

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 adhesiveness of a polyimide film according to the present invention is characterized in that a coupling agent solution is attached to the surface of the polyimide film, the solution is dried, and then a corona discharge treatment is performed. Although the mechanism of improving the adhesive strength by is not clear, the surface properties are made uniform by attaching a coupling agent, and the introduction of hydrophilic groups is stabilized by performing corona discharge treatment on the uniformized film surface, It is considered that the adhesive strength is improved.

As the method of attaching the coupling agent solution, for example, the coupling agent solution is applied to the film surface, the film surface is rubbed with the coupling agent solution, the coupling agent solution is sprayed on the film surface, or the film is Examples thereof include a method of immersing in a coupling agent solution. Examples of the coupling agent in the present invention include silane-based, titanate-based,
An aluminum-based or zirco aluminum-based coupling agent may be used. These coupling agents have both a functional group reactive with the film and a functional group reactive with the adhesive in the molecule, and try to act as an intermediary to increase the affinity between the film and the adhesive. is there. Therefore,
By attaching the coupling agent solution to the surface of the film, the coupling agent reacts with the surface components of the film, and a film of the coupling agent having a functional group reactive with the adhesive is uniformly formed on the surface of the film. The properties can be made uniform.

After that, the solution is dried and then the surface of the polyimide film having the uniform surface properties is subjected to corona discharge treatment, whereby a hydrophilic group can be stably introduced into the film surface. It is possible to obtain an excellent effect of improving the adhesiveness.

The concentration of the coupling agent solution is
0.005 to 30 wt%, more preferably 0.01 to 5 wt%
By setting the content to%, the coupling agent can be evenly attached to the film surface evenly, and the effect of the coupling agent can be sufficiently exhibited.

[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 coupling agent solution is attached to the surface of the polyimide film, the solution is dried, and then a corona discharge treatment is carried out, for example, shown in FIG. It can be implemented using the surface treatment apparatus 10. This surface treatment apparatus 10 is an apparatus 1 for applying a coupling agent solution.
2, a drying furnace 14, and a corona discharge treatment device 16 are provided. The polyimide film 20 fed from the feeding device 18 is coated with the coupling agent solution in the device 12 for applying the coupling agent solution, and then the solution attached to the film surface is dried in the drying oven 14. Then, the polyimide film 20 is introduced into the corona discharge treatment device 16 and subjected to corona discharge treatment, and the surface-treated polyimide film 20 is wound up by the winding device 22.

More specifically, the apparatus 12 for applying the coupling agent solution comprises a bar coater 24 for applying the coupling agent solution, a coupling agent tank 26 for storing the coupling agent solution, and a press roll 28. The bar coater 24 is partially immersed in the solution in the coupling agent tank 26. Conventionally known devices are used as the drying furnace 14 and the corona discharge treatment device 16, and the corona discharge treatment device 16 includes a pair of highly insulated rolls 30 and a linear corona arranged close to the rolls 30. The corona electrode 32 is provided with an electrode 32, and the corona electrode 32 is fixed to a frame 36 via a plurality of insulators 34 so that corona discharge is generated from the corona electrode 32 when high energy is applied to the corona electrode 32. In addition, reference numeral 38 is a conveyance roll, and in the surface treatment apparatus 10, the polyimide film 20 is used.
To drive the vehicle satisfactorily.

More specifically, in the apparatus 12 for applying the coupling agent solution, the polyimide film 2 is used.
0 is adjusted so as to come into contact with the bar coater 24 by the pressing roll 28. When the polyimide film 20 is run from the feeding device 18 to the winding device 22 with a constant tension and the bar coater 24 is rotated, a cup is formed on the film surface. A ring solution can be applied. At this time, the direction in which the bar coater 24 is rotated may be the traveling direction of the film or may be opposite to the traveling direction of the film. Further, the base material of the bar coater 24 is not particularly limited, and rolls made of a base material such as a non-woven fabric, rubber rolls, mesh rolls, etc. can be used, but those which do not practically damage the film surface preferable.

In the surface treatment apparatus 10, the method of applying the coupling agent solution by the bar coater 24 is used as a means for adhering the coupling agent solution. However, in addition to this, for example, like the surface treatment apparatus 40 shown in FIG. The polyimide film 20 is sandwiched between two rolls 42 and 44, and the polyimide film 2 is placed along the roll 42.
0 may be run and the roll 44 may be rotated to apply the coupling agent solution. In addition to the roll coater method using such a roll, a spreader method using a doctor knife is used as a coating method, Meyer bar coating, gravure roll coating, reverse roll coating, a brush coater method, an air blade method, a spray coater method, Curtain coater system,
Various other methods such as a dip coater method can be mentioned, and the application may be performed by any application method.

Examples of the coupling agent in the present invention include silane-based, titanate-based, aluminum-based, and zirco-aluminum-based coupling agents. These coupling agents may be used alone or Several kinds may be mixed and used, and can be set empirically, but it is particularly preferable to use a silane coupling agent. Of these, aminosilane coupling agents are more preferable. These are reactive groups (methoxy group, ethoxy group, etc.) that have bondability with the surface component of the polyimide film and reactive groups (acryl group, amino group, epoxy group, etc.) that have bondability with the adhesive component in the molecule. It is possible to enhance the affinity between the film and the adhesive by mediating (coupling) the bond between the film and the adhesive.

To specifically list such coupling agents, among silane coupling agents, acrylic silane-based coupling agents include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane and γ-methacryloxypropyl. Methyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ
Examples thereof include acryloxypropylmethyldimethoxysilane.

In the aminosilane type, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, N
-Phenyl-γ-aminopropyltrimethoxysilane,
N- (phenylmethyl) -γ-aminopropyltrimethoxysilane, N-methyl-γ-aminopropyltrimethoxysilane, N, N, N-trimethyl-γ-aminopropyltrimethoxysilane, N, N, N-tributyl -Γ
-Aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-
β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, N-ω (aminohexyl) γ-aminopropyltrimethoxysilane, N {N′-β ( Aminoethyl)}-β (aminoethyl) γ-aminopropyltrimethoxysilane and the like can be mentioned.

In the epoxysilane type, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ
Examples thereof include glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane and γ-glycidoxypropylmethyldimethoxysilane.

In the titanate coupling agent, isopropyltriisostearoyl titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropyltris (dioctylpyrophosphate) titanate, tetraoctylbis (ditridecylphosphite) titanate, tetraisopropylbis ( Dioctyl phosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl)
Phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl isostearoyl diacrylic titanate, isopropyl tri (dioctyl phosphate) titanate , Isopropyl tricumyl phenyl titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, dicumiphenyloxyacetate titanate, diisostearoyl ethylene titanate and the like.

Other aluminum coupling agents include alkyl acetoacetate-aluminum-
In the case of the zirco aluminum-based coupling agent, methacryto zircoaluminate can be mentioned as the diisopropylate.

The above coupling agent is dissolved in a solvent and used as a solution. The solvent is methanol,
Ethanol, propanol, isopropanol or alcohol solvents such as Solmix, which is a mixed solvent thereof, acetone, MEK, 2-pentanone, ketone solvents such as 3-pentanone, and aromatic hydrocarbon solvents such as toluene and xylene. To be These may be used alone, or may be used as a mixture of several kinds, or may be used as a mixture with water. Especially, methanol is preferably used.

The concentration of the coupling agent solution is 0.
It is preferably 005 wt% to 30 wt%, and more preferably 0.01 wt% to 5 wt%. This is because if the concentration of the coupling agent is too high, the surface of the polyimide film becomes uneven, which is not desirable in appearance. On the contrary, if the concentration of the coupling agent is too low, the sufficient effect cannot be obtained.

By thus uniformly attaching the coupling agent solution to the surface of the film, the surface components of the film react with the coupling agent to form a film of the coupling agent on the surface of the film. The properties can be made uniform.

Next, the polyimide film 20 whose surface properties have been made uniform by the above-mentioned treatment step is introduced into the drying oven 14, and the step of drying the solution adhering to the film surface in the drying oven 14 is performed. The drying condition is not particularly limited, and is appropriately set empirically. Then, the polyimide film 20 that has undergone the drying step is introduced into the corona discharge treatment device 16 and subjected to corona discharge treatment.

In such a corona discharge treatment device 16,
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 20 is provided between the highly insulated roll 30 and the corona electrode 32 of the filament in the roll 30. The corona electrode 32 running along the roll 30 is fixed to the frame 36 below the polyimide film 20 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 of the polyimide film 20 (the surface coated with the coupling agent solution).

Further, as shown in FIG. 2, when the coupling agent solution is applied to the upper surface of the film, the corona electrode 32 is arranged on the upper side of the polyimide film 20 like the corona discharge treatment device 46, and the polyimide Film 20
The corona discharge treatment may be applied to the upper surface (the surface coated with the coupling agent solution). Thus, when the coating surface of the coupling agent solution is one side,
The coated surface may be subjected to corona discharge treatment, but like the corona discharge treatment 48 in FIG. 3, the corona electrodes 32 of the filaments are arranged so as to face the two rolls 30 and the corona electrodes are provided on both sides of the film. You may comprise so that a discharge process may be performed.

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.

During corona discharge treatment, 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 coupling agent solution is attached, the corona discharge treatment is continuously carried out to form a film of the coupling agent on the surface of the film so that the surface properties are made uniform. Can be subjected to corona discharge treatment, and hydrophilic groups (hydroxyl group, carboxylic acid group, carbonyl group, etc.) can be stably introduced to the film surface. That is, hydrophilic groups (hydroxyl group, carboxylic acid group, carbonyl group, etc.) are stably introduced to the film surface along with amino groups, acrylic groups, epoxy groups, etc., which have an affinity with the adhesive in the molecule of the coupling agent. Further, it is possible to stably obtain a further excellent adhesiveness improving effect.

The examples of the method for improving the adhesiveness of the polyimide film according to the present invention have been described above. As means for attaching the coupling agent solution, in addition to the above-mentioned coating method, dipping method and spraying method Any method such as rubbing with a coupling agent solution may be used. Note that rubbing with a coupling agent solution means applying physical mechanical force to the film surface in the presence of the coupling agent solution, and specifically rubbing the film surface with a cloth impregnated with the coupling agent solution. (Or wiping), rubbing the film surface in the coupling agent solution, and rubbing the film surface to which the coupling agent solution is attached.

For example, the surface treatment apparatus 50 shown in FIG.
The film 20 is introduced and dipped in the coupling agent tank 26 by the transport roll 38, and the film 20 is nipped by the rubbing roll 52 made of a base material such as a nonwoven fabric,
The rubbing roll 52 is rotated to rub the film surface, and the film surface can be rubbed with the coupling agent solution to attach the coupling agent solution. In FIG. 3, the skis roll 54
Is provided so that the coating surface can be made uniform, and when the film is immersed in the coupling agent solution for processing as described above, it is preferable to provide the squeeze roll 54. In this way, by rubbing the film surface with the coupling agent solution to attach the coupling agent solution, it is possible to introduce the coupling agent to the film surface and at the same time remove the WBL and the contamination layer on the film surface. Can be made more uniform.
In this case, since the coupling agent solution can be attached to both sides of the film, an example in which both sides of the film are subjected to corona discharge treatment is shown, but of course, only one side may be subjected to corona discharge treatment.

Further, before the coupling agent solution is attached as described above, the film is washed with an organic solvent or the surface of the film is treated with an alkali,
A step of removing the WBL and the contaminated layer may be provided in advance. By removing the WBL and the contaminated layer in advance, the surface properties of the film can be made more uniform.

Further, as described above, the treatment of applying the coupling agent solution and the corona discharge treatment may not be continuously performed, but may be performed in separate steps. In addition, the present invention is not limited to these examples, and the present invention is 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. It is profitable.

The polyimide film surface-treated by the method for improving the adhesion of the polyimide film is
A film of the coupling agent is formed on the film surface to make the surface properties uniform, and it has an amino group, an acrylic group, an epoxy group, etc. that show affinity with the adhesive in the molecule of the coupling agent, and further, corona discharge. It has a film surface that has been stably hydrophilized by treatment, and exhibits superior adhesiveness compared to a conventional polyimide film that has been surface-treated only by corona discharge treatment. It can be firmly bonded to copper foil). 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 is an FPC (flexible printed wiring board).
It can be preferably used as a base film of.

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 Using the apparatus shown in FIG. 1, known from aromatic diamine represented by 4,4′-diaminodiphenyl ether and aromatic tetracarboxylic dianhydride represented by pyromellitic dianhydride. The polyimide film having a thickness of 25 μm obtained by the above method was applied with a coupling agent solution, and then continuously subjected to corona discharge treatment to perform surface treatment of the polyimide film. The processing conditions are line speed 2m / mi
and γ-aminopropyltriethoxysilane (silane coupling agent KBE90
3; 0.1 wt% methanol solution of Shin-Etsu Chemical Co., Ltd. was applied by a bar coater rotating at 250 rpm in the direction opposite to the film advancing direction and dried at 80 ° C. for 1 minute.
Then, the corona discharge treatment was performed by using an aluminum electrode, setting the distance between the electrode and the film to 1.5 mm, and setting the power density to 20.
It was processed at 0 W · min / m ² .

The polyimide film thus treated was evaluated for adhesive strength 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.

[0044]

[Table 1]

Example 2 As a coupling agent solution, 0.1% of titanate-based isopropyltridodecylbenzenesulfonyl titanate was used.
The same treatment as in Example 1 was performed except that a wt% methanol solution was used, and the adhesive strength was evaluated. 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 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 subjected to corona discharge treatment only, and the adhesive strength was evaluated in the same manner as in Example 1. In the corona discharge treatment, the aluminum electrode was used, the distance between the electrode and the film was 1.5 mm, and the power density was 2 as in Example 1.
It was processed at 00 W · min / m ² . 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.

[0048]

EFFECT OF THE INVENTION The method for improving the adhesiveness of a polyimide film according to the present invention is characterized in that after a coupling agent solution is applied, corona discharge treatment is carried out, and a film of the coupling agent is formed on the film surface by such a method. Corona discharge treatment can be performed on the film surface that has been formed and has uniform surface properties. As a result, on the film surface, a hydrophilic group is stably introduced together with an affinity group having an affinity for the adhesive, and an excellent effect of improving the adhesiveness can be obtained.

Further, the polyimide film whose adhesiveness is improved by such a method for improving the adhesiveness of the polyimide film has an affinity group having an affinity for the adhesive on the film surface, and at the same time, the film surface is stably hydrophilized. Therefore, 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 surface treatment apparatus for carrying out the method for improving the adhesiveness of a polyimide film according to the present invention.

FIG. 3 is an explanatory view showing another surface treatment apparatus for carrying out the adhesion improving method for a polyimide film according to the present invention.

[Explanation of symbols]

 10, 40, 50; Surface treatment device 12; Device for applying coupling agent solution 14; Drying furnace 16, 46, 48; Corona discharge treatment device 18; Feeding device 20; Polyimide film 22; Winding device 24; Bar coater 26; Coupling agent tank 28; Pressing roll 32; Corona electrode 38; Conveying roll

Claims (3)

[Claims] 1. A method for improving adhesion of a polyimide film, which comprises applying a coupling agent solution to the surface of a polyimide film, drying the solution, and subjecting the dried film to corona discharge treatment. . 2. The concentration of the coupling agent solution is 0.
The method for improving the adhesiveness of a polyimide film according to claim 1, wherein the content is 005 to 30 wt%, more preferably 0.01 to 5 wt%. 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.