JPH051160A - Surface modification of polyimide resin - Google Patents

Abstract

PURPOSE:To accomplish the subject uniform modification by treatment with stabilized electric discharge produced by applying high voltage between a metallic high-voltage-applying electrode having metallic projections and specific counter electrode in a rare gas atomosphere. CONSTITUTION:The objective modification treatment of the surface of a polyimide resin can be accomplished by electric discharge produced, in a gaseous atmosphere at 100-10000 Torr containing >=20mol% of a rare gas, by applying high voltage with a frequency of pref. 20 KHz to 100 MHz between (A) a metallic high-voltage-applying electrode having 4-25/cm<2> of metallic projections pref. 2-30mm in height with the ratio b<2>/a within the range 0.04-5.1(where, (b) is projection's height, and (a) is its bottom area) and (B) counter electrode supporting the object to be treated and coated with a dielectrics such as rubber, glass or ceramic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying the surface of a polyimide resin such as a polyimide film.

[0002]

2. Description of the Related Art Polyimide resins are widely used because of their high heat resistance and high insulation, but the poor adhesion of their surfaces has always been a problem. Corona discharge treatment, plasma treatment , Various surface modification techniques such as sand plast treatment and chemical etching treatment have been studied.

For example, Japanese Patent Application Laid-Open No. 61-141532 proposes a technique for modifying an aromatic polyimide film by low temperature plasma treatment. This technology is 3 × 10
^{-3 to} 30 Torr, preferably 0.01 to 10 Torr, which is processed by a discharge generated under a low pressure. This method easily forms a stable discharge, that is, a glow discharge. There is an advantage that the surface is modified. However, this low-temperature plasma treatment method requires the formation of a low-pressure atmosphere region, requires a vacuum container and large exhaust equipment, and is extremely costly, and is not suitable for adjusting the predetermined pressure atmosphere or changing conditions. Since there is a problem that it takes a long time, there is a problem that the processing cost is high.

On the other hand, as a plasma processing method which does not require a vacuum container and a large exhaust equipment, 100 to 100 containing at least 20 mol% of rare gas elements is used.
In a gas atmosphere of 1000 Torr, a high heat resistance is obtained by the discharge formed by the high voltage applied between the electrode coated with the dielectric material supporting the polymer film and the opposite electrode also coated with the dielectric material. A method for treating a molecular film is known (Japanese Patent Laid-Open No. 1-138242).
No.).

This method is advantageous in terms of the apparatus because it does not use a vacuum, but since the high-voltage applying electrode is also covered with a dielectric material, an intermediate support cannot be performed, and a wide electrode has its own weight. However, there is a problem in that the accuracy of the distance from the counter electrode that supports the object to be processed becomes poor and uniform processing cannot be performed. On the other hand, when a metal rod or the like is used as a high-voltage applying electrode, an intermediate support or the like is easy, but even if the parallelism with the counter electrode is good, the discharge is concentrated at one or two points and uniform treatment cannot be performed. There is a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object thereof is to provide a surface modification method for a polyimide resin which gives stable quality. .

[0007]

The object of the present invention is as follows.
When modifying the surface of the polyimide resin, the ratio of the square of the height b to the area a of the bottom surface (b) in a gas atmosphere of 100 to 1000 Torr containing at least 20 mol% of a rare gas.
² / a) has metallic projections in the range of 0.04 to 5.1.
A metal high-voltage applying electrode having a range of 25 pieces / cm ² to 4 pieces / cm ² and arranged so as to face the protruding portion of the electrode,
A method of modifying the surface of a polyimide resin, characterized in that a surface is coated with a dielectric and a discharge is formed by applying a high voltage between a counter electrode supporting an object to be processed. .

The form of the polyimide resin used in the present invention is not particularly limited, but a film form is particularly preferable. The discharge in the present invention is provided with a metallic high voltage applying electrode having a protrusion and a counter electrode which is provided so as to face the protrusion of the electrode and which supports an object to be processed whose discharge surface is covered with a dielectric. Formed between.

FIG. 2 is an explanatory view of a preferred example of the high voltage applying electrode used in the present invention. In FIG. 2, the high-voltage applying electrode is composed of a metal substrate 10, a quadrangular pyramid-shaped metal protrusion 11 provided on one surface of the metal substrate 10 at a predetermined interval, and a cooling metal pipe 12 arranged on the opposite surface. There is. In this example, the cooling medium is passed through the metal pipe 12 to be cooled. However, in the present invention, the cooling medium may be provided without the metal pipe 12 so that the cooling medium may flow into the metal substrate 10.

The metal protrusions formed on the metal substrate preferably have a protrusion structure having a specific bottom area and height, and the shape thereof is, for example, a needle shape, a cone, a triangular pyramid or a quadrangular pyramid. Alternatively, a hemispherical shape may be used. Alternatively, the metal projections having these shapes and the metal projections having a columnar structure such as a column can be used in combination. As shown, these metal projections are joined and fixed at their bottom surfaces to one side of the metal base.

In the present invention, the metal projection formed on one surface of the metal substrate has a ratio (b ² / a) of the square of the height b to the area a of the bottom surface b ² (b ² / a) of 0.04 to 5.1. It is important to be in the range so that even if a long workpiece is processed at high speed by applying a large amount of power, the workpiece is not damaged by heat and the pressure is 100 to 1000 To.
A stable discharge can be maintained at rr.
If (b ² / a) is less than 0.04, arc discharge is likely to occur, and if (b ² / a) is more than 5.1, the cooling efficiency of the metal projection tips is lowered, causing thermal damage to the workpiece. Easy to give.
More preferably, (b ² / a) is in the range of 0.05 to 1.3. Further, in order to make the discharge gap constant, it is preferable that the heights of the metal protrusions are uniform with a dimensional error of 0.5 mm or less, and the height is preferably 2 to 30 mm.

The density of the metal projections provided on the metal substrate is 0.25 from the viewpoint of preventing unevenness of treatment and uniformity of discharge.
It is important to be in the range of 4 pieces / cm ² to 4 pieces / cm ² . The density of the metal projections is preferably in the range of 0.4 / cm ² to 2 / cm ² . The arrangement of the metal protrusions is not particularly limited, but it is preferable to arrange the metal protrusions uniformly as illustrated in FIG. In particular, when continuously processing a long object to be processed while traveling, it is preferable to arrange the metal projections so that they are arranged as close to each other as possible when viewed from the traveling direction of the object.

Since discharge occurs only between the tip of the protrusion and the counter electrode, when processing a wide film or the like,
A support can be provided on the back surface of the high-voltage applying electrode to prevent bending and the like, and the distance from the counter electrode can be kept constant to perform uniform processing. The material for the high voltage applying electrode is not particularly limited, and metals such as brass, copper, iron, SUS, and aluminum are used. The shape of the counter electrode supporting the object to be processed is selected according to the form of the object to be processed, but in the case of a long object such as a film, it is preferably a drum electrode. It is important to cover at least the surface of the counter electrode where a discharge is formed with a dielectric material, and examples of the material of the dielectric material include rubber, glass and ceramics, and the thickness thereof is 0.1 mm.
It is preferably -5 mm.

It is not necessary that the number of high-voltage applying electrodes and the number of counter electrodes supporting the object to be treated be the same, but it is preferable to provide two or more high-voltage applying electrodes with respect to the electrodes supporting the object to be treated. The pressure of the atmosphere in which the discharge treatment is performed is 100 to
It is important that the range is 1000 Torr,
If it is less than rr, an advanced vacuum exhaust device or the like is required, and if it exceeds 1000 Torr, it becomes difficult to start the discharge. The pressure range of 600 to 900 Torr is more preferable.

It is important for the gas composition of the atmosphere to contain at least 20 mol% of a rare gas element, and by doing so, even if the discharge is in a gas atmosphere of 100 to 1000 Torr, the discharge is a normal spark. It is not a discharge (corona discharge) but a discharge similar to glow discharge under vacuum, and more electric power can be supplied to the discharge than spark discharge. Further, it is more preferable that the atmosphere gas contains a rare gas element in an amount of 50 mol% or more, and the rare gas elements used are He, Ne, Ar, Kr and X.
Examples include e, but Ar is most preferred. Examples of the gas that can be used as a mixture with the rare gas include CO ₂ , N ₂ and organic gas, but are not limited to these. Oxygen is not preferable as the gas composition of the atmosphere, and it is preferable to avoid positive addition of oxygen as the composition of the gas introduced from the gas introduction system. The oxygen concentration in the vicinity of the discharge area inside the processing chamber is preferably maintained at 1 vol% or less.

The frequency of the high voltage applied to the high voltage applying electrode is preferably selected in the range of 20 kHz to 100 MHz. Discharge is difficult to start below 20 kHz, and matching is difficult to exceed above 100 MHz. A more preferable frequency is 50 kHz to 500 kHz. The electrode supporting the object to be processed may be grounded, or the electrode may be floated from the ground and connected to an output terminal which is a pair of connection terminals of the high voltage power supply and the high voltage power supply. Of course, it is preferable that the high voltage power supply has a matching circuit.

The processing strength is preferably a processing power density of 50 W · min / m ² or more, and more preferably a processing power density of 100 W · min / m ² or more. Here, the processing power density is the output width of the discharge part.
It is the value divided by (the axial direction of the drum-shaped electrode) and the moving speed of the electrode supporting the object to be processed. Next, although an apparatus for processing a film will be described as an example of an apparatus for carrying out the method of the present invention, the present invention is not limited thereto.

In FIG. 1, the polyimide film 1 is sent to the discharge processing section 9 by the sending roll 2. A gas having a predetermined composition is supplied from the gas introduction system 8 to the electric discharge processing section 9, and is maintained at a predetermined gas pressure by a simple exhaust device (not shown). The film 1 is formed between the high voltage applying electrode 3 and the grounded drum-shaped electrode 4 (counter electrode) by the high frequency high voltage applied from the high voltage power source 5 through the matching transformer 6 in the discharge processing section 9. After being processed by the electric discharge, it is taken up by the take-up roller 7.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Moreover, the measurement of the adhesive force was performed as follows. A thermosetting acrylic adhesive or a polyamide adhesive was applied to the treated surface of the treated film, which was then laminated with a copper foil using a laminator.

Then, using a universal tensile tester ("Tensilon" manufactured by Toyo Baldwin), 90
The adhesive force when peeled in the ° direction was measured. The value of the adhesive force was expressed as a relative value when the adhesive force between the untreated film and the copper foil was 1.0. Example 1 In the device shown in FIG. 1, a high-voltage applying electrode having a structure as shown in FIG. 2 with protrusions having a shape of a regular square pyramid having a height of 5 mm and one side of the bottom surface of 10 mm (b ² / a = 0.25, protrusion density 1
25 μm thick polyimide film (“Kapton” 100H manufactured by Toray DuPont Co., Ltd.) using 3 pieces / cm ²
Was plasma-treated in an argon gas atmosphere of 760 Torr. The width of the electrode was 300 mm, the traveling speed of the film was 15 m / min, and the input power was 1430 W. The surface of the counter electrode drum was coated with 10 mm thick silicone rubber.

The discharge occurred only between all the tips of the protrusions of the high voltage applying electrode and the drum-shaped electrode, and spread uniformly on the drum-shaped electrode. When the adhesive strength of the obtained film was measured, it showed a strong adhesive strength which was more than twice that of the untreated film. Comparative Example 1 A high voltage applying electrode having a height of 13 mm and one side of the bottom surface of 3 mm
The same discharge treatment as in Example 1 was performed except that (b ² /a=18.8, protrusion density 11.1 / cm ²⁾ was used.
The same discharge was obtained, but the tips of the projections of the high-voltage applying electrode became red-hot, and the film had irregularities due to heat shrinkage. Comparative Example 2 The same discharge treatment as in Example was performed except that a copper round bar having a diameter of 9 mm was used as the high-voltage applying electrode. The discharge occurred only at one or two points in the center of the electrode where the distance between the drum-shaped electrode and the high-voltage applying electrode was short, and at the other portions, the film was not treated at all.

[0022]

INDUSTRIAL APPLICABILITY According to the present invention, the surface of the polyimide resin contains a rare gas of at least 20 mol% or more and 100 to 1
Since a high-voltage applying electrode having a specific shape and a counter electrode coated with a dielectric were used in the discharge treatment in a gas atmosphere of 000 Torr, stable discharge can be obtained and uniform treatment can be performed. .

[Brief description of drawings]

FIG. 1 is a side view of a discharge treatment device used in the present invention.

FIG. 2 is an explanatory diagram of a high voltage applying electrode.

[Explanation of symbols]

1 film 2 delivery roll 3 High voltage application electrode 4 Drum electrode 5 High-voltage power supply 6 Matching transformer 7 Winding roll 8 Gas introduction system 9 Discharge processing part 10 Metal substrate 11 Metal projection 12 Pipe for water cooling

Claims (2)

[Claims] 1. When modifying a surface of a polyimide resin, a rare gas is contained in an amount of at least 20 mol% or more.
In a gas atmosphere of 0 to 1000 Torr, the ratio of the square of the height b to the area a of the bottom surface (b ² / a) is in the range of 0.04 to 5.1, and 0.25 metal projections / a metallic high-voltage applying electrode having a range of cm ² to 4 pieces / cm ² , and a counter electrode which faces the projection of the electrode and which has a surface covered with a dielectric and which supports a workpiece. A method for modifying the surface of a polyimide resin, characterized in that a high voltage is applied in the meantime to perform a discharge treatment. 2. The height of the protrusion of the high voltage applying electrode is 2 to 30 mm.
The method for modifying the surface of a polyimide resin according to claim 1, wherein