JPH06107828A - Method for modifying surface of fluororesin film - Google Patents

Abstract

PURPOSE:To provide the title method by which a fluororesin film excellent in adhesive properties is obtd. CONSTITUTION:The surface of a fluororesin film is modified by using a treating apparatus of air-to-air type having air seal sections in front of an behind a treating chamber and exposing the film to electric discharge in the chamber by applying a high voltage W between a high-voltage apply electrode and a counter electrode supporting the film. The discharge is conducted in a gaseous atmosphere contg. at least 70mol.% at least one rare gas selected from the group consisting of He, Ne, Ar, Kr, and Xe, at least one gas selected from the group consisting of CO2 and hydrocarbons of the formula: CnH2n+2 (wherein n is 1-4), and oxygen in an amt. of 500ppm or lower and under a pressure of 100-1,000Torr. Thus, a fluororesin film having adhesive properties practically enough is obtd.

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 fluorine film.

[0002]

2. Description of the Related Art Today, fluorine films have been used in various fields such as corrosion resistant materials, lining materials, insulating materials, and wire coating materials, but their poor adhesion is a problem. For this reason, various surface modification methods such as corona discharge treatment, plasma treatment, chemical etching treatment, and sandblast treatment have been investigated. In particular, the dry process such as corona discharge treatment and plasma treatment does not require a cleaning step and is an effective surface modification method.

Several surface modification methods have been proposed for fluorine films.

US Pat. No. 3,296,011 proposes a method of corona discharge treatment in a gas containing an organic compound such as glycidyl methacrylate and hexane, and Japanese Patent Publication No. Sho 49-1.
2900 discloses a method of corona discharge treatment in acetone vapor.

On the other hand, Japanese Patent Application Laid-Open No. 1-146930 discloses 1 to 1000.
Torr of C _n H _2n + 2 a (n = 1 to 8) in a gas atmosphere containing 1 mol% or more, has been proposed a method of low-temperature plasma treatment.

[0006]

However, in the method by corona discharge treatment, the surface of the fluorine film is modified,
Although the adhesiveness is improved, it has the following drawbacks.

[0007] The adhesive strength is largely reduced due to a change with time, and is particularly deteriorated under high temperature and high humidity, and when irradiated with ultraviolet rays.

With respect to the fluorine film, there is a great demand to modify only one side of the film and to utilize the characteristics of the fluorine film itself on the other side. However, in these processes, a so-called show-through phenomenon that the back surface of the processing surface is sparsely processed often occurs.

[0009] The surface treatment develops thermal adhesiveness below the melting point of fluorine, but the temperature is still high, which is not practical. For example, in the case of tetrafluoroethylene-hexafluoropropylene copolymer, heat fusion occurs at about 240 ° C.
Use at 20 ° C. or lower is desired.

On the other hand, according to the method of Japanese Patent Laid-Open No. 1-146930, there is little change with time, there is no set-off, and heat-sealing property at 200 ° C. or less and other adhesive properties can be obtained. Especially 100To
The processing in a gas atmosphere of rr or higher does not require an exhaust system and a strong air seal mechanism. An air seal mechanism is provided before and after the processing chamber to guide the film from the atmosphere into the processing chamber and then into the atmosphere. This is a method that makes it possible to perform processing with a device having a so-called air-to-air mechanism. However, it has been found that when the treatment is carried out by an air-to-air type treatment device, the treatment effect is not stable even if the same gas composition is obtained.

The present invention has been devised in view of the above-mentioned drawbacks of the prior art, and an object thereof is to provide a surface treatment method for a fluorine film, which can obtain a stable treatment effect.

[0012]

The object of the present invention is as follows.
Discharge obtained by applying a high voltage between a high voltage applying electrode and a counter electrode supporting a fluorine film in the processing chamber using an air-to-air type processing device having an air seal part before and after the processing chamber. A method of modifying the surface of a fluorine film by using He, N
70 mol% or more of at least one rare gas selected from e, Ar, Kr, and Xe, CO _2, and a chemical formula C _n H _{2n + 2}
Fluorine film containing at least one of hydrocarbons represented by (n = 1 to 4) and having a pressure of 100 to 1000 Torr in a gas atmosphere having an oxygen concentration of 500 ppm or less. It is achieved by the surface modification method of.

The fluorine film used in the present invention includes tetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkoxyethylene copolymer. Polymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), trifluoroethylene chloride (PCTFE),
Polymers and copolymers of fluorine-based monomers such as vinylidene fluoride (PVDF), copolymers of these monomers with non-fluorine-based monomers, and mixtures of these polymers with other polymer compounds Can be mentioned. Among them, PTFE, FEP, PFA, ET
FE and the like are preferable.

In the present invention, the discharge is 100 to 1000.
It is formed by applying a high frequency high voltage between a high voltage applying electrode and a counter electrode supporting the film in a gas atmosphere of Torr.

The pressure of the atmosphere for discharging is 100 to 10
The range is 00 Torr, but more preferably 600 to
A pressure range of 900 Torr is good. Pressure is 100 Tor
If it is less than r, a highly accurate air-to-air device is required, and if it is 1000 Torr or more, it becomes difficult to start the discharge.

The high voltage applying electrode may have any shape, but a rod shape is preferable. Gas atmosphere is 10
When the pressure is 0 Torr or more, the discharge is easily transferred to the arc discharge, so that it is preferable to coat the electrode with the dielectric. As the dielectric, any material such as glass, ceramics and rubber can be used. The dielectric coating thickness is 0.1 to 5 mm, more preferably 0.5 to 3 mm. If the thickness is less than 0.1 mm, dielectric breakdown is likely to occur, and if the thickness is greater than 5 mm, a high voltage is required for discharge, and the electrode is easily damaged.

It is preferable that the high-voltage applying electrode has a hollow structure and is cooled, and examples of the coolant flowing through the inside include water, air, freon, and the like, and water is preferable. If the cooling is not performed, the temperature of the electrode becomes high due to the energy of plasma, so that the processing film or the electrode is easily damaged.

The counter electrode for supporting the film may have any shape as long as the film is in close contact with the film. However, in the case of continuously processing a long film, the film can be supported in a drum shape so that it can be freely conveyed. Electrodes are preferred. It is preferable that the size thereof is, for example, twice or more the diameter of the rod-shaped high voltage applying electrode. It is important that at least a portion of the drum-shaped electrode where the discharge is formed is coated with a dielectric material like the high voltage applying electrode, and the same material as the high voltage applying electrode such as thickness and material is used.

It is not necessary that the number of high-voltage applying electrodes and the number of counter electrodes supporting the film are the same, and it is preferable to provide two or more high-voltage applying electrodes for one counter electrode.

The gap between the electrodes is preferably set to 0.1 to 10 mm, more preferably 0.5 to 5 mm. If the gap is shorter than 0.1 mm, it becomes difficult to obtain the precision of the gap, and if it is wider than 10 mm, it is easy to shift to arc discharge, and a large amount of electric power cannot be supplied, which is not preferable.

The frequency of the high voltage applied to the high voltage applying electrode is not particularly limited, but it is preferably selected in the range of 20 kHz to 55 MHz, and more preferably 50 kHz to 5 MHz.
It is 00 kHz.

The counter electrode may be grounded, or the electrode may be floated from the ground and connected to an output terminal that forms a pair of connection terminals with the high voltage electrode of the high voltage power supply.

Further, it is preferable that the high voltage power source has a matching circuit.

In the present invention, the gas composition of the atmosphere is extremely important, and the rare gas, C _n H _{2n + 2} (n = 1 to 4) and C
It consists of three components, O ₂ .

As the C _n H _{2n + 2} compound, those having n = 1 to 4 are used alone or in a mixture, and preferably n =
It is a simple substance or a mixed gas of 1 and 2 of CH ₄ and C ₂ H ₆ . If these compounds are not contained, sufficient adhesive force cannot be obtained or no adhesive force can be obtained at all.

It is important that the atmosphere gas contains a rare gas in an amount of 70 mol% or more, preferably 80 mol% or more. When it is less than 70 mol%, the discharge region is narrowed and spark discharge is apt to occur, so that a sufficient effect cannot be obtained or treatment unevenness is not preferable.

The rare gas used is Ar, Ne,
A simple substance or a mixed gas selected from He, Kr, and Xe can be mentioned, but Ar and He are preferable, and A is more preferable.
r is a simple substance.

In the present invention, it is necessary to include CO ₂ in the processing gas. Adhesive strength cannot be obtained without CO ₂ .

[0029] In the present invention, C _n H _{2n +} composition ratio of ₂ and CO ₂ is, C _n H composition ratio of _{2n + 2} and CO ₂ C _n H _{2n +} 2 / C
The value of O ₂ is preferably in the range of 0.6 or more and 50 or less, and more preferably in the range of 1.0 or more and 40 or less. If it is out of these ranges, a sufficient adhesive force cannot be obtained, which is not preferable.

[0030] In the present invention, the residual gas and the management of the O ₂ concentration in the treated gas as associated gas is very important, in the O ₂ concentration in the processing chamber is 500ppm or less, preferably below 400ppm Need to be O
_{If the} concentration of ₂ exceeds 500 ppm, the treatment effect for improving the adhesive strength is reduced or the effect is completely absent, which is not preferable.

The processing strength is 10 to 1000 W · mi.
The processing power density is preferably n / m ² , more preferably 50 to 700 W · min / m ² . Here, the processing power density is a value obtained by dividing the product of the power input to the discharge and the time by the discharge area. In the case of processing a long film, the input power is the width of the discharge part (electrode length) and the film thickness. It is the value divided by the processing speed.

Next, one example of the apparatus for carrying out the present invention will be shown, but of course the present invention is not limited to this.

In FIG. 1, the film 1 delivered from the delivery roll 2 in the atmosphere enters the processing chamber 10 via the air seal portion 9. The processing chamber 10 is a gas supply device 8
A predetermined gas atmosphere is maintained with the supplied gas. In the processing chamber 10, the film is discharged by the high voltage applied to the high-voltage applying electrode 3, and is discharged into the atmosphere through the air seal portion 9 and wound on the winding roll 7.

[0034]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(1) Measurement of Adhesive Strength A heat sealer (manufactured by Tester Sangyo Co., Ltd., TP-701) was prepared by superposing the treated surfaces of two treated fluorine films.
S), hot plate temperature 190 ° C, seal pressure 1.5k
Thermal bonding was performed under the conditions of g / cm ² and sealing time of 10 seconds.

Then, the heat-bonded film was cut into a width of 10 mm, and the adhesive strength at the time of T peeling was measured using a universal tensile tester (manufactured by Toyo Baldwin, Tensilon). The pulling speed was 200 mm / min.

(2) Measurement of oxygen concentration The oxygen concentration at a point 5 mm from the film in the processing chamber before discharge was measured by a zirconia sensor type oxygen concentration meter (LC-800 manufactured by Toray Engineering).

Examples 1 to 4 and Comparative Examples 1 to 5 An FEP film having a thickness of 25 μm (“Toyofuron” manufactured by Toray Synthetic Film Co., Ltd.) was used under the conditions shown in Table 1 and shown in FIG.
Was processed in a gas atmosphere under atmospheric pressure. The high-voltage applying electrode was an iron tube coated with water having a thickness of 1 mm, and the inside was cooled with water, and the drum-shaped electrode was a silicone rubber coated with a thickness of 1 mm. The distance between the electrodes was 1 mm. The frequency of the high frequency power source used is 11
It is 0 kHz.

The results of evaluation of the adhesive strength are shown in Table 1. Table 1
As is clear from Examples, in Examples 1 to 4, 350 g / c
While a practically sufficient adhesive force of m or more was obtained, in Comparative Examples 1 to 5, only a weak adhesive force of 0 to 120 g / cm 2 was obtained.

[0040]

[Table 1]

[0041]

Since the present invention is constructed as described above, it is possible to obtain a stable surface modification effect of the fluorine film, particularly an effect of improving the adhesiveness.

Although the reason why such an effect is obtained is not clear, the discharge treatment causes a fluorine atom abstraction reaction on the surface of the fluorine film, and CH ₄ and CO ₂ generate an appropriate functional group on the surface. , although adhesion improving effect can be obtained, when the O ₂ is present, the generation of functional groups is believed to be hampered by the reaction of O ₂ is high.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus for carrying out the present invention.

[Explanation of symbols]

 1: Film 3: High voltage application electrode 4: Counter electrode 5: High frequency high voltage power supply 6: Matching circuit 9: Air seal part 10: Processing chamber

Claims (1)

[Claims] 1. A processing apparatus of an air-to-air system having an air seal part before and after a processing chamber is used, and a high voltage is applied between the high voltage applying electrode and a counter electrode supporting a fluorine film in the processing chamber. A method of modifying the surface of a fluorine film by the discharge obtained by the method, wherein the discharge is performed by using at least one rare gas selected from He, Ne, Ar, Kr, and Xe at 70 mol% or more, and CO ₂ And at least one of the hydrocarbons represented by the chemical formula C _n H _{2n + 2} (n = 1 to 4 is an integer), and the oxygen concentration is 5
100 to 1000 To in a gas atmosphere of 00 ppm or less
A method for modifying the surface of a fluorine film, which is carried out under a pressure of rr.