JP3333640B2 - Method for improving adhesion of polyimide film and polyimide film having improved adhesion - Google Patents

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 particularly, the present invention relates to a polyimide film having an improved adhesiveness without affecting the adhesive. The present invention relates to a method for improving the adhesion of a polyimide film to be obtained and a polyimide film having improved adhesion by the method for improving the adhesion.

[0002]

2. Description of the Related Art Usually, a polyimide film is bonded to a metal foil (mainly a copper foil) using an adhesive, or is formed by a vapor deposition method.
It is used as a base film of an FPC (Flexible Printed Wiring Board) by being processed into a laminated board composed of a film layer and a metal layer by a plating method or a sputtering method.
However, the problem is that the conventional polyimide film has poor surface adhesiveness, and as it is, it causes a product failure. Therefore, in order to improve the adhesiveness of the surface of the polyimide film, it is common to use it after performing a plasma treatment.

That is, the poor adhesion of the polyimide film surface is considered to be due to the high water repellency of the film surface. Therefore, the film surface is subjected to plasma treatment to impart hydrophilicity to the surface. It improves the adhesion. The reason that the plasma treatment increases the hydrophilicity of the surface is that hydroxyl groups, carboxylic acid groups,
This is because a hydrophilic functional group such as a carbonyl group is newly generated.

[0004]

By the way, a polyimide film is obtained by condensation polymerization by a solution casting method. However, when a surface thereof is mixed with a stabilizer, an additive, etc.,
These bleed preferentially, and the surface fragile layer (WBL; We
ak Boundary Layer), and also W
It is scientifically known that the transfer to the surface of a low-molecular polymer such as an oligomer may be accelerated as a BL-formed product. It is also conceivable that a contaminant such as oil generated from equipment during the film forming process or present in the air adheres to the film to form a contaminated layer.

It is considered that the formation of these layers determines the surface characteristics of the polyimide film and may be a factor that hinders the adhesion. In addition, if a WBL or a contaminant layer is formed on the surface of the polyimide film as described above, when a plasma treatment is performed on such a layer, the surface provided with hydrophilicity by the plasma treatment is brittle and easily peels off. Essentially, the adhesion cannot be improved.

In particular, the surface characteristics of a polyimide film vary significantly depending on the conditions at the time of film formation.
For example, even if films having the same characteristics are manufactured at the same time, the formation of WBL or a contaminated layer may or may not be significant depending on the conditions at the time of film formation. In other words, the surface properties of the polyimide film become non-uniform, and even if plasma treatment is performed on the surface of the polyimide film, a sufficient treatment effect may not be obtained, and it is difficult to achieve stable surface modification. is there.

Therefore, the present inventors have solved the above-mentioned problems and provided a method for improving the adhesion of a polyimide film and a polyimide film with improved adhesion which can stably obtain an excellent effect of improving the adhesion. As a result of intensive research for the purpose, the present invention has been achieved.

[0008]

SUMMARY OF THE INVENTION The gist of the method for improving the adhesion of a polyimide film according to the present invention is to deposit a coupling agent solution on the surface of a polyimide film, and then drying the solution. It is to perform a plasma treatment on the film thus made.

In the method for improving the adhesion of a polyimide film, the concentration of the coupling agent solution may be as follows:
0.005 to 30 wt%, more preferably 0.01 to 5 wt%
%.

[0010] Next, the gist of the polyimide film having improved adhesion according to the present invention is to use the method for improving adhesion of polyimide film described in any of the above.
By performing the surface treatment, a hydrophilic group is formed on the film surface.
It is something that can be obtained by being introduced .

[0011]

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 adhered to the surface of a polyimide film, the solution is dried and then subjected to plasma treatment. Although the mechanism for improving the adhesive strength is not clear, the surface properties are made uniform by attaching the coupling agent, and the introduction of the hydrophilic group is stabilized by performing the plasma treatment on the uniformed film surface, and the adhesive strength is improved. Is considered to be improved.

More specifically, as a method of adhering the coupling agent solution, for example, applying the coupling agent solution to the film surface, rubbing the film surface with the coupling agent solution, spraying the coupling agent solution on the film surface, Can be immersed in a coupling agent solution. Examples of the coupling agent in the present invention include silane-based, titanate-based, aluminum-based, and zirconium-based coupling agents. These coupling agents have both a functional group reactive with the film and a functional group reactive with the adhesive in the molecule, and strive to mediate to increase the affinity between the film and the adhesive. is there. Therefore, by attaching the coupling agent solution to the film surface, 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 film surface. The surface properties can be made uniform.

Thereafter, after the solution is dried, the surface of the polyimide film having the uniform surface properties is subjected to plasma treatment, whereby a hydrophilic group can be stably introduced into the film surface. An excellent adhesiveness improving effect can be obtained.

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

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for improving the adhesion of a polyimide film according to the present invention will be described below in detail with reference to the drawings. The polyimide film mentioned here means a film in a broad sense including a thin film having a thickness of several μm to a sheet having a thickness of several hundred μm, and the molecular structure of the polyimide film does not matter.

The method for improving the adhesiveness of a polyimide film is characterized in that after a coupling agent solution is applied to the surface of the polyimide film, the solution is dried and then subjected to a plasma treatment. The processing can be performed using the processing apparatus 10. This surface treatment apparatus 10 is an apparatus 1 for applying a coupling agent solution.
2, a drying furnace 14 and a plasma processing apparatus 16. Then, the polyimide film 20 sent out 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 adhered to the film surface is dried in the drying furnace 14. Subsequently, the polyimide film 20 is introduced into the plasma processing apparatus 16 and subjected to plasma processing, and the surface-treated polyimide film 20 is taken up by the winding apparatus 2.
2.

More specifically, the apparatus 12 for applying the coupling agent solution includes a bar coater 24 for applying the coupling agent solution, a coupling agent tank 26 for storing the coupling agent solution, and a holding roll 28. Part of the bar coater 24 is immersed in the solution in the coupling agent tank 26. As the drying furnace 14 and the plasma processing apparatus 16, conventionally known apparatuses are used, and the plasma processing apparatus 1 is used.
6 is a gas introduction unit 3 for introducing gas into the device 16.
0, a power supply 32 for starting a discharge by flowing a current into the device 16 is provided so that plasma processing can be performed while maintaining the gas atmosphere in the device 16 at a constant composition and a constant pressure. I have. In addition, reference numeral 34 denotes a transport roll, which makes the polyimide film 20 run well in the apparatus 10.

More specifically, in the apparatus 12 for applying a coupling agent solution, the polyimide film 2
0 is adjusted so as to come into contact with the bar coater 24 by the holding roll 28. Therefore, 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, the film surface Can be coated with a coupling agent solution.
At this time, the direction in which the bar coater 24 rotates may be the traveling direction of the film, or may be rotated in the direction opposite to the traveling direction of the film. The base material of the bar coater 24 is not particularly limited, and a roll made of a base material such as a nonwoven fabric, a rubber roll, a mesh roll, or the like can be used. preferable.

In the surface treatment apparatus 10, a method of applying the coupling agent solution by using a bar coater 24 is used, but other methods such as a surface treatment apparatus 36 shown in FIG. , The polyimide film 20 is sandwiched between two rolls 38 and 40, and the polyimide film 2 is
Alternatively, a method in which the coupling agent solution is applied by rotating the roller 40 and rotating the roll 40 may be used. In addition, in addition to the roll coater method using such rolls, the spreader method using a doctor knife, Meyer bar coating gravure roll coating, reverse roll coating, brush coater method, air plate method, spray coater method, curtain Various other methods such as a coater method and an immersion coater method can be used, and the coating may be performed by any coating method.

Examples of the coupling agent in the present invention include silane-based, titanate-based, aluminum-based, and zirconium-based coupling agents. These coupling agents can be used alone or in combination. A mixture of several types may be used and can be set empirically, but it is particularly preferable to use a silane coupling agent. Among them, aminosilane-based coupling agents are more preferable. These are reactive groups (methoxy group, ethoxy group, etc.) that have a bond with the surface component of the polyimide film and reactive groups (acrylic group, amino group, epoxy group, etc.) that have a bond with the adhesive component in the molecule. And mediate (coupling) the bonding between the film and the adhesive, thereby increasing the affinity between the two.

When such coupling agents are specifically enumerated, among silane coupling agents, acryl-silane-based γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyl Methyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ
-Acryloxypropylmethyldimethoxysilane and the like.

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.

In the epoxysilane system, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ
-Glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, and the like.

As the titanate-based coupling agent, isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, tetraisopropyl bis ( Dioctyl phosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl)
Phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate, isopropyltrioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl isostearyl diacryl titanate, isopropyl tri (dioctyl phosphate) titanate Isopropyl tricumylphenyl titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, dicumiphenyloxyacetate titanate, diisostearoylethylene titanate, and the like.

Other aluminum-based coupling agents include alkyl acetoacetate-aluminum-
Diisopropylate is a methacrylate zircoaluminate as a zirconium-based coupling agent.

The above-mentioned coupling agent is used as a solution by dissolving it in a solvent.
Examples thereof include alcohol solvents such as ethanol, propanol, isopropanol or a mixed solvent thereof such as Solmix, ketone solvents such as acetone, MEK, 2-pentanone and 3-pentanone, and aromatic hydrocarbon solvents such as toluene and xylene. Can be These may be used alone, may be used by mixing several kinds, or may be used by mixing with water. Particularly, methanol is preferably used.

The concentration of the coupling agent solution is 0.1.
It is preferably from 005 wt% to 30 wt%, more preferably from 0.01 wt% to 5 wt%. If the concentration of the coupling agent is too high, unevenness is observed on the surface of the polyimide film, which is not preferable in appearance. Conversely, if the concentration of the coupling agent is too low, a sufficient effect is not exhibited.

In this way, the coupling agent solution is uniformly attached to the surface of the film, whereby 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 to which the coupling agent solution has been applied in the above-described processing step and the surface properties of which have been made uniform is led to the drying furnace 14, and the solution attached to the film surface is dried in the drying furnace 14. Done. The drying conditions are not particularly limited, and are appropriately set empirically. Then, the polyimide film 20 that has undergone the drying step is introduced into the plasma processing apparatus 16 and subjected to plasma processing in the plasma processing apparatus 16. In the plasma processing apparatus 16, the inlet and outlet of the film are sealed, and a gas having an appropriate composition is introduced from the gas inlet 30 and is maintained at a predetermined gas pressure. And power supply 3
When the switch 2 is turned on, discharge is started and plasma is generated in the device 16. At this time, a gas composition and a gas pressure are appropriately selected so that a glow discharge is obtained.

Here, the gas pressure of the atmosphere in which the plasma processing is performed is not particularly limited, but it is preferable to perform the plasma processing under a pressure in the range of 100 to 1000 Torr. At a pressure of 100 Torr or less, a vacuum device or the like is required, and at a pressure of 1000 Torr or more, discharge becomes difficult. In particular, the workability of the plasma treatment is improved by performing the treatment under the atmospheric pressure, and the polyimide film having excellent adhesion obtained by performing the surface treatment by the adhesion improvement method according to the present invention can be obtained with high productivity. preferable. Although the gas composition of the plasma treatment is not particularly limited, it is preferable to perform the plasma treatment in a single gas or mixed gas atmosphere of a rare gas element so that the discharge at 100 to 1000 Torr also performs a glow discharge (not a spark discharge).
It is particularly preferable that the air in the apparatus is replaced with the rare gas element, but air may be mixed in such a degree that glow discharge is not hindered.

By such a treatment step, a hydrophilic functional group (hydroxyl group, carboxylic acid group, carbonyl group, etc.) can be introduced by chemically modifying the film surface, and the hydrophilicity of the film surface is improved.

After the coupling agent solution is applied in this manner, the plasma treatment is performed continuously,
A film of a coupling agent is formed on the surface of the film, and plasma treatment can be performed on the surface of the film having a uniform surface property, and a hydrophilic group (hydroxyl group, carboxylic acid group, carbonyl group, etc.) can be stably formed on the film surface. Can be introduced. That is, a hydrophilic group (hydroxyl group, carboxylic acid group, carbonyl group, etc.) is stably introduced into the film surface along with an amino group, an acrylic group, an epoxy group, etc., which have an affinity for the adhesive in the molecule of the coupling agent. In addition, it is possible to stably obtain a further excellent adhesiveness improving effect.

The embodiment of the method for improving the adhesiveness of a polyimide film according to the present invention has been described above. Before attaching the coupling agent solution as described above, a physical mechanical A step of removing WBL and a contaminated layer in advance by applying force or treating the film surface with alkali may be provided. By previously removing the WBL and the contaminated layer, the surface properties of the film can be made more uniform.

As a means for attaching the coupling agent solution, a coating method, a dipping method, a spraying method, or the like may be used as described above, or a rubbing method using a coupling agent solution may be used. . In addition,
Rubbing with a coupling agent solution refers to applying physical mechanical force to the film surface in the presence of the coupling agent solution. Specifically, rubbing the film surface with a cloth or the like impregnated with the coupling agent solution (or Wiping), rubbing the film surface in a coupling agent solution, and rubbing the film surface to which the coupling agent solution is attached.

For example, the surface treatment device 42 shown in FIG.
The film 20 is introduced and dipped into the coupling agent tank 26 by the transport roll 34, and the film 20 is nipped by a rubbing roll 44 made of a base material such as a nonwoven fabric.
The rubbing roll 44 is rotated to rub the film surface, so that the film surface can be rubbed with a coupling agent solution. In FIG. 3, a squeeze roll 46 is provided so that uniformity can be obtained on the coated surface. In the case where the film is immersed in a coupling agent solution for processing, the squeeze roll 46 is used. It is preferable to provide the roll 46. By rubbing the surface of the film with the coupling agent solution and attaching the coupling agent solution in this manner, the coupling agent is introduced onto the film surface, and at the same time, the WBL on the film surface is
And the contamination tank can be removed, and the surface properties can be made more uniform.

In addition, as described above, the treatment for attaching the coupling agent solution and the plasma treatment may not be continuously performed, but may be performed in separate steps. In addition, the present invention is not limited to only these examples, and the present invention is based on the knowledge of those skilled in the art without departing from the spirit thereof.
The present invention can be implemented with various improvements, changes, and modifications.

The polyimide film surface-treated by the method for improving the adhesion of the polyimide film is as follows:
A film of the coupling agent is formed on the film surface, the surface properties are made uniform, and it has an amino group, an acrylic group, an epoxy group, etc., which have an affinity for the adhesive in the molecule of the coupling agent, and furthermore, by a plasma treatment It has a stable hydrophilized film surface and exhibits superior adhesion compared to conventional polyimide films surface-treated only by plasma treatment. ).
Further, a metal layer can be uniformly formed on the film surface by a vapor deposition method, a plating method, or a sputtering method. That is, the polyimide film having improved adhesiveness according to the present invention can be suitably used as a base film of an 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 an apparatus shown in FIG. 1, an aromatic diamine represented by 4,4'-diaminodiphenyl ether and an aromatic tetracarboxylic dianhydride represented by pyromellitic dianhydride were known. After a coupling agent solution was applied using the polyimide film having a thickness of 25 μm obtained by the method described above, plasma treatment was continuously performed to perform surface treatment of the polyimide film. Processing speed is 2m / min line speed
And γ-aminopropyltriethoxysilane (silane coupling agent KBE90) as a coupling agent solution.
3: A 0.1 wt% methanol solution of Shin-Etsu Chemical Co., Ltd.) was applied by a bar coater rotating at 250 rpm in a direction opposite to the direction of film advance, and dried at 80 ° C. for 1 minute.
Then, the plasma processing conditions were changed such that the gas composition in the apparatus was Ar /
Substitution was performed so that He = 6/4, the pressure was set to 760 Torr, and the power density was set to 1500 w · min / m ² , and the film was subjected to surface treatment.

The polyimide film thus treated was evaluated for adhesive strength by the following method. The treated film and copper foil (electrolytic copper foil “3EC” manufactured by Mitsui Mining & Smelting Co., Ltd. “3EC” 35 μm thick) were laminated using an acrylic adhesive (“Pilalux” manufactured by DuPont).
A curing reaction of the adhesive is performed at 85 ° C for 1 hour, and FCCL
(Film / copper foil laminate). Obtained FCC
A sample was cut out so that the copper pattern width of L became 3 mm, and a tensile tester (S-100 manufactured by Shimadzu Corporation)
C "), 90 at a peel test speed of 50 mm / min
° Peeling tensile test was performed. Table 1 shows the measurement results based on the average value of n = 5. In addition, all the fracture surfaces after peeling occurred at the film / adhesive interface.

[0041]

[Table 1]

Example 2 The same treatment as in Example 1 was carried out except that a 0.1 wt% methanol solution of titanate-based isopropyl triisostearoyl titanate was used as a coupling agent solution, and the adhesive strength was evaluated. Table 1 shows the measurement results based on the average value of n = 5. In addition, the fracture surface after peeling is
All occurred at the film / adhesive interface.

Comparative Example 1 For comparison, the adhesion strength of the polyimide film having a thickness of 25 μm used in Example 1 was evaluated in the same manner as in Example 1 except that the polyimide film was not subjected to a surface treatment. Table 1 shows the measurement results based on the average value of n = 5. In addition, all the fracture surfaces after peeling occurred at the film / adhesive interface.

Comparative Example 2 For comparison, the adhesive strength was evaluated in the same manner as in Example 1 except that the polyimide film having a thickness of 25 μm used in Example 1 was subjected to only the plasma treatment and used. The plasma treatment was performed under the same conditions as in Example 1 (gas composition; Ar / He).
= 6/4, pressure; 760 Torr, power density; 1500 w ·
min / m ² ). Table 1 shows the measurement results based on the average value of n = 5. In addition, all the fracture surfaces after peeling occurred at the film / adhesive interface.

[0045]

The method for improving the adhesiveness of a polyimide film according to the present invention is characterized in that a plasma treatment is performed after a coupling agent solution is applied, and a film of the coupling agent is formed on the film surface by such a method. The plasma treatment can be performed on the film surface whose surface properties have been made uniform. As a result, a hydrophilic group is stably introduced into the film surface together with an affinity group exhibiting an affinity for the adhesive, and an excellent effect of improving adhesiveness can be obtained.

The polyimide film having improved adhesion by such a method for improving the adhesion of a polyimide film has an affinity group exhibiting an affinity for an 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 the drawings]

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

[Explanation of symbols]

 10, 36, 42; surface treatment device 12; device for applying coupling agent solution 14; drying furnace 16; plasma treatment device 18; feeding device 20; polyimide film 22; winding device 24; Ring agent tank 28; press roll 30; gas inlet 32; power supply 34; transport roll

Continuation of the front page (56) References JP-A-62-243627 (JP, A) JP-A-63-68641 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 7 / 00-7/18 C08J 5/12

Claims (3)

(57) [Claims] 1. A method for improving the adhesiveness of a polyimide film, comprising: attaching a coupling agent solution to the surface of a polyimide film, drying the solution, and performing a plasma treatment on the dried film. 2. The method according to claim 1, wherein 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 surface treatment using the method for improving adhesion of a polyimide film according to claim 1 or 2 .
A polyimide film having improved adhesiveness , wherein a hydrophilic group is introduced into the film surface .