JPS5826652B2 - Kinzokuka film capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a miniaturized metallized film capacitor using polyvinylidene fluoride film as a dielectric.

BACKGROUND OF THE INVENTION Recent electrical equipment, particularly communication and audio equipment such as radios, televisions, and tape recorders, has become increasingly smaller, and the electrical components used in these equipment have also been required to be smaller.

The field of film capacitors is no exception, and in order to meet this demand, research is being conducted on miniaturization, such as making dielectric films thinner, increasing the dielectric constant, and simplifying the exterior.

The polyvinylidene fluoride film obtained by uniaxially or biaxially stretching and heat treatment has a dielectric constant of io~18 and a diameter of δ0.6~
1%, volume resistivity 1 x 1015 to 5 x 1015 Ω・m
1) It has electrical properties such as a dielectric breakdown voltage of 250 to 300 kV/my/, and has a higher dielectric constant than other films, making it the most effective dielectric material in the current trend toward miniaturized film capacitors. .

Currently, polyvinylidene fluoride films up to a thickness of 4μ have been developed.

Both metal foil type and metalized film type capacitors are being considered, but the metalized film type, which does not use metal foil, is of course more advantageous in terms of miniaturization.

Furthermore, metallized film capacitors have so-called self-healing properties, in which the vapor-deposited metal film (electrical film) scatters and restores insulation even if a weak point in the film causes a minute dielectric breakdown.
It has the advantage of being able to use a thinner film than the metal foil wrapping type, which is also a major factor contributing to miniaturization.

However, studies conducted so far have revealed that polyvinylidene fluoride film has the disadvantage that property deterioration is accelerated due to its self-healing properties.

That is, when the film decomposes during self-healing, harmful hydrofluoric acid is generated, causing an increase in element δ and a decrease in insulation resistance, which eventually progresses to fatal dielectric breakdown.

Therefore, it has been extremely difficult for metallized polyvinylidene fluoride film capacitors to obtain their original characteristics and to actually use them.

The present invention has been made in view of the above points, and an object of the present invention is to provide a metallized film capacitor that exhibits only excellent dielectric properties by changing the structure of the capacitor so that the polyvinylidene fluoride film does not undergo self-healing. The purpose is to

The present invention will be explained with reference to FIG.

FIG. 1 is a diagram illustrating the structure of the metallized film capacitor of the present invention, which is already known structurally.

That is, a double-sided metallized polyvinylidene fluoride film is formed by forming vapor deposited films 3 and 3' on both sides of the polyvinylidene fluoride film 1, and using this double-sided metallized polyvinylidene fluoride film as a substrate, one or both sides of the double-sided metallized polyvinylidene fluoride film are formed. After forming an organic or inorganic insulating thin film 4.4' on the capacitor, the film is wound or laminated to obtain a gold shrink film capacitor.

Here, the thickness of the polyvinylidene fluoride film 1 of the substrate film and the thickness of the insulating thin film 4 are 4 or 4' in the case of single-sided formation.
, 4+4' in the case of double-sided formation) are approximately equal and the dielectric breakdown strength of the two is almost unchanged, it is clear that self-healing occurs at approximately the same rate for both.

However, if the insulating thin films 4 and 4' are made thinner than the polyvinylidene fluoride film 1 or made of a material with lower dielectric breakdown strength than the polyvinylidene fluoride film 1, self-recovery occurs only on the insulating thin film 4°4' side. It is possible to cause the effect to take place.

Such a metallized film capacitor of the present invention is produced by making the dielectric breakdown strength of the insulating thin films 4 and 4' lower than that of the polyvinylidene fluoride film 1, and allowing self-recovery of the capacitor to occur only in the insulating thin film. 1
This is intended to suppress the self-recovery of the polyvinylidene fluoride film 1, thereby preventing the generation of hydrofluoric acid when the polyvinylidene fluoride film 1 is decomposed.

Furthermore, it is intended to produce the effect of miniaturization by making the insulating thin films 4, 4' thinner.

The materials for the insulating thin films 4 and 4' include organic materials that can be lacquered, such as polycarbonate, acetylcellulose, polysulfone, polystyrene, and polyvinylpyridine; discharge polymerizable substances such as styrene or organic silane;
In addition, it does not matter whether it is organic or inorganic, such as inorganic materials such as 8102 and MgO.

Next, one embodiment of the present invention will be described.

Aluminum is vapor-deposited on both sides of a polyvinylidene fluoride film 1 with a thickness of 4 μm to form an electrode, and a polycarbonate lacquer film is formed on both sides so that the total thickness is 2 μm to form the desired metallization of the rolled type. Film capacitor (1μ
F) was created.

A conventional metallized polyvinylidene fluoride capacitor (1 μm) is made by overlapping a double-sided metalized polyvinylidene film (4 μm) and a polyvinylidene fluoride film (4 μm).
For comparison with m), a long-term voltage application test was conducted.

160VDC for conventional capacitors. A voltage of 130 VDC was applied to the capacitor of one example of the present invention.

The results are shown in Figure 2. In contrast to the conventional capacitor shown by the solid line in the figure whose characteristics gradually deteriorate, the capacitor of this embodiment shown by the broken line in the figure shows constant characteristics that do not change over a long period of time.

As described above, the present invention forms an insulating thin film having a lower dielectric breakdown strength than the polyvinylidene fluoride film on one or both sides of a double-sided metallized polyvinylidene fluoride film, so that the polyvinylidene fluoride film has excellent dielectric properties. By preventing deterioration of capacitor characteristics, which has been a problem in the past, it has the excellent effect of making it possible to manufacture miniaturized capacitors that meet general demands. It is.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a metallized polyvinylidene fluoride film for explaining the present invention in detail, and FIG. 2 is a graph showing the results of a long-term voltage application test between an embodiment of the present invention and a conventional capacitor. Yes, 1 is polyvinylidene fluoride film,
4 and 4' are insulating thin films.

Claims (1)

[Claims] 1. A metallized film capacitor comprising a double-sided metallized polyvinylidene fluoride film, which is wound or laminated with an insulating thin film having a lower dielectric breakdown strength than the polyvinylidene fluoride film formed on one or both sides of the film.