JPH0488160A - Production of metallized polypropylene film for capacitor - Google Patents

Abstract

PURPOSE:To improve adhesive strength between a film and a metallic vapor deposited layer by subjecting the surface of a biaxially oriented polypropylene film to low temp. plasma treatment under reduced pressure and then forming a metallic vapor deposited layer on the resulting treated surface. CONSTITUTION:Low temp. plasma treatment is previously applied to the surface of a biaxially oriented polypropylene film under a reduced pressure of about 0.005-5Torr. It is desirable to form fine ruggedness of 0.01-0.1mum diameter in a density of 100-10,000 pieces/mum<2>, preferably 500-5,0000 pieces/mum<2>, in the surface. Further, Al, Zn, Cu, Sn, Zn-Al alloy, etc., are vapor-deposited onto the treated surface. By this method, the adhesion between the film layer and the metallic vapor deposited layer is performed without deteriorating the characteristics of the film, and a superior metallized polypropylene film for capacitor is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a metallized polypropylene film for capacitors that has excellent adhesion between a metallized layer and a film layer.

(Prior Art) Biaxially oriented polypropylene film (hereinafter referred to as OPP film) has the characteristics of low dielectric loss and high dielectric breakdown voltage, and is widely used as a dielectric layer of oil-immersed capacitors.

In this case, the electrode layer is made of vapor-deposited aluminum, zinc, or a mixture thereof, but the adhesion between the film dielectric layer and the vapor-deposited metal layer is poor, and when it is immersed in insulating oil, There were problems such as the vapor deposited layer peeling off from the film layer and the vapor deposited metal layer scattering and falling off due to partial discharge of the capacitor when high voltage was applied.

As a method to increase the adhesion between the film layer and the vapor deposited layer,
A method using corona treatment and a method using a metal with good adhesion such as copper or silver for pre-evaporation have also been proposed, but neither method has yielded satisfactory results. In particular, corona treatment is a method commonly used at present, but its effectiveness is insufficient, and the uneven amount of air caught between the corona treatment roll and the film causes uneven film modification. There were problems such as partial peeling of the vapor deposited layer. In particular, since corona discharge is a high-voltage discharge under atmospheric pressure, sparks are likely to occur due to uneven electric field strength, resulting in pinholes on the film surface and mechanical The electrical strength and electrical insulation properties were impaired.

For these reasons, there has been a demand for the development of a metallized film for capacitors that has improved adhesion between the metal layer and the film layer.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a metallized film for a capacitor that has excellent adhesion between a two-wheeled stretched polypropylene film and a metal vapor deposition layer, without impairing the inherent characteristics of the film. The purpose is to provide a method that can be easily obtained.

(Means for Solving the Problems) A method for manufacturing a metallized polypropylene film for capacitors according to the present invention includes performing low-temperature plasma treatment on the surface of a biaxially oriented polypropylene film under a reduced pressure of 0.005 to 5 torr, and preferably There diameter 0.01~0.17a
fine irregularities with a density of 100 to 10,000 pieces/gn
”, and then a metal vapor deposition layer is formed on the treated surface.

To explain this, as a result of intensive research into the above-mentioned problem, the present inventors performed low-temperature plasma treatment on the surface of a biaxially oriented polypropylene film in advance under a reduced pressure of 0.005 to 5 Torr, and desirably There diameter 0.01
~0. The fine irregularities of the ip have a density of 100 to 10,000.
piece/4. After forming preferably 500 to 5,000 pieces/p2, A1. Zn, Cu-S
The present inventors discovered that by vapor-depositing Zn, Zn-Al alloy, etc., the film layer and the metal vapor-deposited layer are in close contact with each other without impairing the properties of the film, and an excellent metallized polypropylene film for capacitors can be obtained.9 The present invention has been achieved. This is what I did.

In plasma processing according to the method of the present invention, an OPP film is installed in a plasma processing apparatus capable of reducing pressure, and the pressure is o, 0.
This is carried out by applying high frequency power with a frequency of, for example, KHz to several hundred KHz between the electrodes while aerating the inorganic gas under conditions of 0.005 to 5 Torr.

Note that as the discharge frequency band, in addition to the above-mentioned high frequency, low frequency, microwave, direct current, etc. can be used. In addition, the types of low-temperature plasma generators include internal electrode type, external electrode type, coil type capacitive coupling, inductive coupling, etc.
Among these, the internal electrode type is preferred because it can provide excellent adhesion with a short treatment time.

The characteristic of plasma treatment is that it is a low voltage discharge in an atmosphere under a reduced pressure of 0.005 to 5 torr, so it does not generate sparks like that caused by corona discharge and has little negative impact on the base film. . However, the OPP film used as a capacitor film is an extremely thin film with a thickness of 5 to 20 m, and the surface treatment requires more careful setting of conditions.

As mentioned above, the method of the present invention is preferably carried out using the internal electrode method, but there are no particular restrictions on the shape of the electrodes, and the input-side electrode and the ground-side electrode may have the same shape or different shapes. They can have any shape, such as a flat plate, a ring, a rod, a cylinder, etc., and even have a shape in which the metal inner wall of the processing device is grounded as one electrode. It's okay. Note that the input side electrode is generally copper or iron.

Aluminum or the like is used, but in order to maintain stable discharge, it is preferable that these input electrodes be insulating coated with glass, enamel, ceramic, or the like having a withstand voltage of 10,000 V or more. In particular, rod-shaped electrodes coated with insulation are suitable for generating locally effective plasma.

Regarding the electric power applied between the electrodes, if it is too large, it is undesirable because it will cause deformation and deterioration of the film due to heat generation. Preferably controlled.

Inorganic gases used in the present invention include He, Ne, A
There are r, H,, N2.0□, air, CO, CO2, etc., and these can be used alone or in combination of two or more.

The gas pressure during low temperature plasma treatment is 0.005 to 5 torr;
In particular, 0.01 to 1 torr is preferable, and 0.005)
- If the gas pressure is less than 5 torr or more than 5 torr, it may be difficult to generate plasma, or damage may occur to the film due to abnormal discharge, resulting in a decrease in film strength, pinhole formation, thermal deformation, or the resulting electrical discharge of the film. This results in deterioration of characteristics, etc.

Further, it is preferable that the irradiation time of the low temperature plasma be within 100 seconds, particularly within 30 seconds; outside this range, the same phenomenon as described above will occur, so it is not preferable.

By performing the low-temperature plasma treatment under the above conditions, fine irregularities with a diameter of 0.01 to 0.11 are formed on the surface at a density of 100 to 10,000 pieces/immediately 2, preferably 500 to 2.
An OPP film having s, ooo pieces/μm2 is obtained.

○PP film with such fine irregularities on the surface can be used without deteriorating the mechanical strength or electrical properties of the film.
Adhesion with the vapor-deposited metal layer can be significantly improved.

The thus obtained OPP film having fine irregularities is sent to the next surface metallization step to become a final product.

Well-known methods such as vacuum evaporation and sputtering are used to form a metal layer on the surface of an OPP film having fine irregularities, but among these, vacuum evaporation using an electron beam is particularly effective. A product with excellent adhesion can be obtained.

In addition, the materials of the metal layer include A1, Zn, Cu, Sn.
, Zn-Al alloy, etc., but Al or Zn-Al alloy is particularly preferred for use in capacitor films.

Hereinafter, specific aspects of the present invention will be explained with reference to Examples.
The present invention is not limited to this example.

(Example) After an OPP film was installed in a low temperature plasma processing apparatus, the pressure inside the apparatus was reduced to 0.002 torr.

In this state, argon gas was vented, the pressure was adjusted and maintained at 0.05 Torr, and then the power was increased to 110kHz, 20kW per positive electrode.
Plasma treatment was performed for about 3 seconds by applying a power of /m2.

The surface of this PP film was observed using an electron microscope, and the diameter was 0. O1~0.051#, density r, ooo
The presence of -2°000 unevenness/mF was confirmed. This film was vacuum-deposited using an electron beam method to a thickness of 0.05 mm on the surface. A metal layer of Zn-Al alloy (Zn content 10%) was formed to produce a metalized oPP film.

The adhesion of this metal evaporated layer was measured by a tape peel test (when a tape is pasted on a metal evaporated surface, it is rapidly peeled off to evaluate the adhesion) and compared with that of a normal corona discharge treatment. Thus, it was found that the product of the present invention is superior.

(Effects of the Invention) According to the present invention, a metallized film for a capacitor having excellent adhesion between a biaxially oriented polypropylene film and a metal vapor-deposited layer can be easily obtained without impairing the inherent characteristics of the film.

Patent applicant: Shin-Etsu Chemical Co., Ltd.

Claims (2)

[Claims] 1. 0.0 on the surface of the biaxially stretched polypropylene film
After performing low temperature plasma treatment under reduced pressure of 05-5 torr,
A method for producing a metallized polypropylene film for a capacitor, the method comprising forming a metal vapor deposition layer on the treated surface. 2. Polypropylene film after low temperature plasma treatment
Fine irregularities with a diameter of 0.01 to 0.1 μm are formed on the surface.
The method for producing a metallized polypropylene film for a capacitor according to claim 1, having a density of 100 to 10,000 pieces/μm^2.