JPS5821814B2 - kenkaigata capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wound type capacitor that uses an inorganic dielectric material as a dielectric material and has greatly improved its withstand voltage characteristics, dielectric constant, and dissipation.

Currently, in wound type capacitors, plastic film or capacitor paper is used as the dielectric material.

If a wound type capacitor is made by thinning an inorganic dielectric material with excellent electrical properties, it is expected to be a major improvement over the currently used wound type capacitors.

Regarding aluminum electrolytic and tantalum electrolytic capacitors, the dielectric material is aluminum oxide or tantalum oxide, but the electrical properties of the dielectric material itself are not fully utilized, and the electrolyte is used. Therefore, it is not the same type or the same technology as the capacitor mentioned here. There are various methods for thinning an inorganic dielectric material, and there are many materials that can be used as a substrate.

Methods for thinning the film include chemical precipitation, vacuum evaporation, sputtering, and the like.

Among them, taking metal oxide as an example, there are cases in which a single metal film is oxidized, and cases in which the metal oxide itself is formed by vacuum evaporation or sputtering.

Generally, when thinning an inorganic dielectric material, the substrate temperature becomes an important factor in the crystallization process.

Here, the substrate material may be a plastic film, glass sheet, metal foil, etc., but metal foil is most suitable from a thermal standpoint.

This is because various thicknesses, materials, etc., are easily available.

In the case of such a capacitor, its performance is controlled by the electrical characteristics of the dielectric thin film, and the electrical characteristics of the dielectric thin film are influenced by the crystallinity, impurities, etc. of the film.

Regarding the crystallinity of dielectric thin films, there are different critical substrate temperatures depending on the material, but not all materials have been studied at present.

Generally, when the substrate temperature is high, crystallinity tends to improve.

Further, although the influence of the substrate temperature during film formation is also a problem, at the same time, high crystallinity and high purity can be achieved by heat treatment after film formation.

This heat treatment temperature is generally -200 DEG C. or higher, and most common plastic films are unsatisfactory in terms of thermal deformation, deterioration, etc.

Therefore, in the present invention, by using a metal foil (particularly aluminum) as a substrate and vacuum-depositing a metal oxide thereon, it was possible to obtain a wound capacitor with the originally expected performance.

The configuration of this wound type capacitor is explained using a drawing.
1 is a metal foil such as aluminum, and on one surface of this metal foil 1, an inorganic dielectric thin film 2 such as SiO, SiO2, T+02, etc. is formed.

3 is a plastic film such as 1 polyester, and on one side of this plastic film 3, that is, the surface facing the inorganic dielectric thin film 2 of the metal foil 1, a conductive metal thin film 4 made of aluminum or the like is formed by vapor deposition. .

These are stacked and wound to form a wound capacitor, and the drawing shows a cross section of a portion of the capacitor.

Next, an example will be explained.

Experimental example Silicon was continuously deposited on aluminum foil 1.

Since the vapor deposition was carried out continuously on the rolled aluminum foil, the substrate temperature during vapor deposition was 0 to 60°C.

The substrate after vapor deposition was heat treated in normal pressure steam at 500° C. for 20 hours, resulting in a silicon oxide film 2 having sufficient performance as a dielectric for a capacitor.

In addition, a plastic film (
In this case, a polyester film (3) with aluminum (4) vacuum-deposited thereon was laminated to form a wound capacitor.

This capacitor has not only the good characteristics of the silicon oxide film 2 but also the self-healing property characteristic of metallized capacitors, and is smaller and has a larger capacity than conventional plastic film capacitors.

Moreover, such an effect can be obtained from other metal oxides (Ti.

Similar results were obtained with oxides of Ta, W, Wh, etc.).

Furthermore, in principle, other metal foils are also possible, and in the case of Ni foil, the same effect as in the case of aluminum foil was obtained.

As described above, the wound type capacitor of the present invention has two electrodes, one in which an inorganic dielectric thin film is formed on a metal foil, and one in which a conductive metal thin film is formed in a plastic film as the other electrode. Since the substrate on which the inorganic dielectric thin film is formed is a metal foil, it is possible to increase the heat treatment temperature to increase the crystallization of the formed inorganic dielectric thin film, which results in an extremely high dielectric material. Therefore, it is possible to obtain an inorganic dielectric thin film with a high efficiency, and therefore to obtain a smaller capacitor.

[Brief explanation of drawings]

The drawing is a sectional view of essential parts showing an embodiment of the wound type capacitor of the present invention. 1...Metal foil, 2...Inorganic dielectric thin film, 3...Plastic film, 4...
・Conductive metal thin film.

Claims (1)

[Claims] 1. A wound type capacitor characterized in that one electrode is a metal foil on which an inorganic dielectric thin film is formed, and the other electrode is a plastic film on which a conductive metal thin film is formed.