JPH0523046B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to metallized film capacitors,
In particular, it relates to improvements in metallized film capacitors using polypropylene film as the dielectric and zinc as the thin film electrode.

Conventional Structure and Problems Conventionally, in metallized film capacitors using polypropylene film as a dielectric, it has been common to perform corona discharge treatment only on the surface on which thin film electrodes are deposited. On the other hand, by applying corona discharge treatment to the surface on which the thin film electrode was not deposited, it was discovered that the thin film electrode of the metallized film and the polypropylene film had weak adhesive strength, and the metallized film It has come to be used as a means of suppressing partial discharges that occur between the layers of capacitors. However, it has also become clear that this adhesive force is weaker with zinc thin film electrodes than with aluminum thin film electrodes, which have conventionally been commonly used for polypropylene films. This is related to the fact that a thin film of zinc cannot be deposited on a polypropylene film unless a metal for nucleation is deposited during vapor deposition, and that the mechanical strength of a thin film of zinc is lower than that of a thin film of aluminum. It is thought that As a result, in metallized film capacitors in which zinc thin film electrodes are provided on a polypropylene film that has been subjected to corona discharge treatment on both sides, partial discharges cannot be sufficiently suppressed due to insufficient adhesion between the layers, especially during continuous durability tests at temperatures below 0°C. There was a problem that I couldn't do it.

OBJECT OF THE INVENTION The object of the present invention is to improve the adhesion between the layers of a metallized film capacitor using a metalized film consisting of a polypropylene film subjected to double-sided corona discharge treatment and a thin film electrode of zinc. ) is to suppress partial discharge. As a result, it is possible to suppress a decrease in CR value and deterioration of withstand voltage during a low-temperature continuous durability test.

Structure of the Invention In the case of a single-sided metalized film, a metalized film capacitor is provided in which a single-sided metalized film is wound or laminated, in which a zinc thin film electrode is provided on one side of a polypropylene film subjected to corona discharge treatment on both sides. , is characterized in that the thickness of the zinc thin film electrode on the opposing part is set to a film resistance value of 20Ω/□ or more. In addition, when using a double-sided metallized film and a laminated film, a double-sided metalized film consisting of a double-sided corona discharge treated polypropylene film with zinc thin film electrodes on both sides and a double-sided corona discharge treated polypropylene film are used. A wound or laminated metallized film capacitor is characterized in that the thickness of the zinc thin film electrode on the opposing part has a film resistance value of 20Ω/□ or more.

DESCRIPTION OF EMBODIMENTS Hereinafter, the configuration of the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows a cross-sectional view of a pair of single-sided metallized films having a zinc thin film electrode 3 provided on one side of a polypropylene film 1 which has been subjected to corona discharge treatment on both sides. Activated layers 2 formed by corona discharge treatment are present on both surfaces of the polypropylene film 1. Further, the facing portion of the thin film electrode 3 is thinner than the edge portion on the side where the end electrode is formed. In the present invention, by setting the thickness of the thin film electrode 3 in the facing portion to a film resistance value of 20Ω/□ or more, it is intended to suppress partial discharge occurring between the metallized film capacitor layers. This structure was derived from the fact that when two polypropylene films that have been treated with corona discharge treatment on both sides, which inherently exhibit strong adhesive strength, are interposed with a zinc thin film electrode, the adhesive strength is significantly reduced. In addition,
In order to strongly bond polypropylene films that have been treated with corona discharge on both sides, it is necessary to apply a certain pressure and temperature after they are wound and laminated.
This also applies to the case where a zinc thin film electrode is interposed.

In order to reduce the gap between the layers of a metallized film capacitor and to increase the adhesion force, the thinner the zinc thin film electrode is, the better.

However, in general, if the metal is made into a thin film, the film resistance value will increase, and the loss due to the current flowing through this part will also increase, so especially for AC applications, the thickness of the thin film electrode should be 20Ω/ □~200Ω/□ can withstand use. In direct current applications, the physical and chemical stability of the thin film electrode itself is more of a problem than current loss, but it is possible to use thin film electrodes that are even thinner than in alternating current applications.

The surface roughness of the polypropylene film also affects the adhesive strength and the size of the gap between the layers, where partial discharge occurs, but in order to increase the adhesive strength and reduce the gap between the layers, The smoother the surface, the better.

FIG. 2 shows a structure using a double-sided metallized film, and the laminated film in this case is a polypropylene film that has been subjected to corona discharge treatment on both sides. In Figures 1 and 2, the nuclear metal used between the corona discharge treated polypropylene film and the zinc thin film electrode is omitted, but of course copper, silver, etc. are used during vapor deposition. Uses nuclear metal.

Next, specific examples will be described.

After copper was vapor-deposited on one surface of a 6-μm-thick double-sided corona discharge-treated polypropylene film (YK-41 from Toray Industries, Inc.) to form a core metal, the film resistance of the opposing parts was 5 ± 1 Ω. ／□、10±3Ω／□、25±
5Ω/□, 50±10Ω/□, 100±30Ω/□, 250±
A zinc thin film electrode having a resistance of 50Ω/□ and a film resistance value of 4 to 6Ω/□ at the edge in contact with the end electrode was provided by vapor deposition. A pair of single-sided metallized films thus produced were stacked in the same manner as shown in Figure 1 and wound around a cylinder made of polybutylene terephthalate.
After winding paper with a thickness of 10 μm 100 times as the outer winding, zinc was metal sprayed on both end faces. This element was subjected to temperature aging at 120° C. for 15 hours in a vacuum drying oven to bond the layers. Paper is used as the outer wrapping because its elongation at 120°C is smaller than the polypropylene film or polyester film normally used for the outer wrapping, and it generates pressure from the outside to suppress the thermal expansion force of the single-sided metalized film. This is because it can be done.

After temperature aging, lead wires were welded to the end electrodes, placed in a case made of polybutylene terephthalate, and then sealed with a two-component epoxy resin. The capacitance of each sample is 10 μF.

Evaluation was carried out by low temperature continuous durability test. It should be noted that with respect to the initial partial discharge characteristics, almost no difference is observed depending on the membrane resistance value of the opposing portion. this is,
This is because a weak adhesive force exists even when the membrane resistance value of the facing portion is low, so no difference appears in a short-time evaluation. The test conditions were a temperature of -25°C and a voltage of AC440V.

FIG. 3 shows the change over time in the CR value (capacitance value C x inter-terminal insulation resistance value R, unit: F·Ω).

As is clear from Figure 3, metallized film capacitors with zinc thin film electrodes of 5 ± 1 Ω/□ and 10 ± 3 Ω/□ on the opposite side start to decrease in CR value within 500 hours. In contrast, 25± according to the present invention
5Ω/□ (minimum value is 20Ω/□), 50±10Ω/□, 100
For metalized film capacitors with ±30Ω/□ and 250±50Ω/□, no decrease in CR value is observed even after 1000 hours. A decrease in the CR value indicates that the inside of the metallized film capacitor has deteriorated due to partial discharge. Therefore, as shown in the present invention, the film resistance value of zinc is 20Ω/□ or more. It can be seen that the deterioration of metallized film capacitors in continuous low-temperature durability tests is improved compared to metallized film capacitors with membrane resistance values of less than 20Ω/□.

In addition, instead of a double-sided corona discharge treated polypropylene film, a metallized film capacitor prototyped using a single-sided corona discharge treated polypropylene film, in which only the surface on which the zinc thin film was deposited was corona discharge treated, was subjected to the same low-temperature continuous durability test. , the membrane resistance value ranges from 5±1Ω/□ to 250±
All CR before 500 hours up to 50Ω/□
value decreases. From this, it can be seen that the suppression of the decrease in the CR value of the metallized film capacitor according to the present invention, that is, the suppression of the deterioration inside the metallized film capacitor, is brought about by the improvement in self-healing property due to the increased membrane resistance value. This is considered to be the result of improved adhesion between layers.

Effects of the Invention As clarified above, according to the present invention,
By combining a polypropylene film that has been treated with corona discharge on both sides and a thin film electrode with a zinc film resistance of 20Ω/□ or more, it is possible to increase the adhesion between the layers and suppress internal partial discharge and the deterioration caused by it. .

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a main part of a single-sided metallized film capacitor according to the present invention, Fig. 2 is a cross-sectional view of a main part of a double-sided metallized film capacitor, and Fig. 3 is a metallized film capacitor with different membrane resistance values in the opposing part. FIG. 3 is a characteristic diagram showing changes in CR value over time when a film capacitor is subjected to a continuous low temperature durability test. 1... Polypropylene film subjected to double-sided corona discharge treatment, 2... Activation layer, 3... Zinc thin film electrode.

Claims (1)

[Claims] 1. In a metallized film capacitor in which a single-sided metalized film or a double-sided metalized film is wound or laminated, a zinc thin film electrode is provided on one or both sides of a polypropylene film subjected to double-sided corona discharge treatment. A metallized film capacitor with a thickness of 20Ω/□ or more in terms of membrane resistance.