Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Patent
1987-07-28
1988-11-15
Griffin, Donald A.
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
427 81, H01G 101, B05D 506
Patent
active
047853743
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a zinc-metallized film and a vacuum-deposited zinc metallized paper for making metallized capacitors (hereinafter called "zinc-metallized base material for capacitors" generically), and is particularly concerned with a zinc-metallized base material for capacitors functioning remarkably well for use to make heat-pressed capacitor elements and a process for its production.
TECHNICAL FIELD
A metallized base material for use in capacitors, in which an electrode is formed by vacuum depositing a metal, such as zinc, aluminum or the like, on a film, such as polypropylene film, polyester film and the like or on a thin capacitor paper, is very popular presently. The thickness of the vacuum-deposited metal layer of the base material is very thin normally from 100 to 600 .ANG.. Therefore, the metal layer is easily to a hydroxide or an oxide because of the water content or oxygen in the air when it is left to stand. The electric conductivity deteriorates consequently so that the metal layer is not useful as a capacitor electrode. The metal layer is severely denatured when it is left for a long time under high-temperature and high-humidity conditions in a half-finished state for example, as a winding material or capacitor element, particularly at the time of capacitor manufacture.
The most common metals for vacuum depositing indlude aluminum and zinc. They have outstanding electrical characteristics because the capacitance variation is minimized when they are used to make a capacitor and their current resistance is high. As compared with aluminum, zinc is inferior particularly in its resistance to humidity.
In view of the circumstances described above, manufacturers of the metallized base materials exercise a strict quality control so as avoid the aforementioned denaturation on the base material a product. The fact is that the metallized base material is packaged in a high barrier film which exhibits less humidity permeability and oxygen permeability, a desiccating agent (such as silica gel or the like) is sealed in the interior of package so as to lower the humidity during warehousing and transportation, and, further, the warehousing temperature is controlled not to exceed 30.degree. C. Thus, direct measures for preventing the aforementioned metallized base material from being denatured (deteriorated) by humidity absorption and oxidation have not been taken hitherto. Rather, attention has been paid solely to a packaging control for storage to, thus coping with the situation by means of an indirect method.
DISCLOSURE OF THE INVENTION
In view of the actual circumstances mentioned above, the invention is intended for solving the aforementioned problem directly instead of taking the indirect means for prevention of denaturation of the metal layer as above mentioned. That is, according to the aforementioned indirect means, the metallized base material is exposed to denaturation once it is unpacked and hence it must be used as quickly as possible, and still worse, the temperature and humidity must be taken into consideration even in the process for manufacturing the capacitors, thus involving various problems. In order to solve such problems thoroughly, the inventors provide such means as will prevent humidity absorption and oxidation from occurring thereafter by forming a protective layer on the surface of the metallized base material concurrently with or after manufacture of the base material.
The invention solves the problems by employing technical means as defined in the claims. However, the following case has been found to have something to do with the invention by the inventors, which will be referred to hereunder accordingly. That is, the case refers to an invention relating to a metallized film for an AC capacitor as disclosed in Japanese Patent Laid-Open No. Sho 59-227115. This is not intended for protecting the metallized base material against denaturation but rather, it employs the following means in view solely of the working of the capacitor as
REFERENCES:
patent: 2727297 (1955-12-01), Fralish et al.
Ibaraki Takamasa
Imai Makoto
Kamotani Hisatoshi
Nagai Susumu
Yamauchi Tsunetatsu
Griffin Donald A.
Honshu Seishi Kabushiki Kaisha
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