Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Patent
1996-05-24
1998-02-17
Nakarani, D. S.
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
361313, 3613211, 361322, 361324, 428213, 428215, 428216, 428336, 428448, 428450, 428451, 428452, 428469, 428472, 427 79, 427 81, H01G 406
Patent
active
057197415
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zinc-deposited base material for metallized capacitors, such as those used in power capacitors and the like, and a method of manufacture thereof, and in particular relates to technology for improving moisture resistance.
2. Description of the Prior Art
Power capacitors have been used, for example, in power plants and substations for power factor improvement, voltage regulation and power flow adjustment and the like. In recent years, as such power capacitors, metallized capacitors are practically employed. The metallized capacitor includes electrodes which are formed by depositing a metal such as zinc or aluminum onto a film, such as polypropylene film, polyester film or the like, or a thin condenser paper (condenser tissue).
One type of such metallized capacitors found in the prior art is disclosed in Japanese Patent Publication Number SHO-57-51251 (hereinafter, referred to as "Prior Art Reference 1") filed by the applicant of this application. As described in Prior Art Reference 1, a metal and metalloid or nitride is deposited onto a dielectric surface in accordance with the degree of roughness of such surface, and then a metallic electrode layer is formed thereon by vapor deposition.
For example, after depositing silicon monoxide on one side surface of an insulating paper to form a layer having a thickness of approximately 0.5 mm, zinc is deposited over such layer, excepting a non-deposited portion which is left as it is to form an insulating portion on the layer, thereby forming a metallized paper. Then, two of these metallized papers are stacked together and rolled up to form capacitor elements. In this way, the dielectric dissipation factor can be made small, thus making it possible to obtain high dielectric characteristics.
Unfortunately, however, in the metallized capacitor disclosed in Prior Art Reference 1, no consideration is taken to its moisture resistance. Namely, because the layer of zinc which is deposited is extremely thin at a thickness of 5-60 nm, exposure at all times to oxygen and moisture in the surrounding air is likely to cause such layer to transform into oxides and hydroxides, which results in lowering the conductivity of such layer. As a result, the metal-deposited layer of which conductivity has been lowered can not be used as an electrode.
In this connection, in order to improve moisture resistance of the zinc-deposited capacitors, the applicant of this application proposed another type of a zinc-deposited capacitor which is disclosed in Japanese Laid-Open Patent Application Number SHO-62-130503 (hereinafter, referred to as "Prior Art Reference 2"). As described in Prior Art Reference 2, in the zinc-deposited capacitor, a layer having a 0.7-50 nm thickness which is formed of silicon oil, fatty acid or paraffin wax or the like is applied on a zinc-deposited layer under constant vapor pressure.
Further, Japanese Laid-Open Patent Application Number HEI-1-158714 (hereinafter, referred to as "Prior Art Reference 3") discloses a capacitor having a zinc-deposited layer which is covered by a 0.3-20 mg/m.sup.2 protective coating made from silicon and silicon oxide. Furthermore, in Japanese Laid-Open Patent Application Number SHO-62-279819 (hereinafter, referred to as "Prior Art Reference 4"), there is disclosed another capacitor with an improved self-protective function which is achieved by preventing the electrode from oxidizing by blocking off oxygen. For this purpose, the capacitor includes a metallized plastic having a metallized surface which is covered with an insulating oxide layer having 5-100nm thickness and made from silicon oxide, aluminum oxide or the like.
However, the method disclosed in Prior Art Reference 2 which uses the protective layer having a 0.7-50 nm thickness and made from silicon oil, fatty acid or paraffin wax or the like and the method disclosed in Prior Art Reference 3 which uses the protective layer having a 0.3-20mg/m.sup.2 thickness of silicon and silicon oxide are ins
REFERENCES:
patent: 4785374 (1988-11-01), Nagai et al.
patent: 5061568 (1991-10-01), Kessel et al.
Ikeda Hideki
Imai Makoto
Murata Mamoru
Takagi Toshiyuki
Takahashi Yasuo
Nakarani D. S.
Oji Paper Co. Ltd.
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