JPS6046529B2 - capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitor that has the ability to self-relax an electric field concentration area and also has the ability to reduce energy during self-healing.

Conventionally, in capacitors in which only electrodes with a sheet resistance value of 2 to 4 Ω/sq are formed on a dielectric film, partial discharge occurs in the strong electric field area at the end of the electrode or around the area where self-healing occurs. Due to the low sheet resistance value of ~4Ω/sq, the energy during self-healing is large, causing electrode scattering, resulting in a decrease in capacitance and deterioration of the dielectric film, resulting in thinning of the dielectric film and breakdown voltage. It was difficult to improve. The present invention aims to eliminate such drawbacks and provide a capacitor with stable characteristics, by forming a thin film of a hydrocarbon compound containing at least fluorine on the surface of a dielectric film, and on one or both surfaces of the dielectric film. This is a capacitor constructed using a single-sided metallized film or a double-sided metalized film on which electrodes with a sheet resistance value of 5.0 Ω/sq or more are formed.

The dielectric film used in the present invention is a fluorine-free dielectric film made of polyethylene terephthalate, polypropylene, polycarbonate, etc., and a thin film of a hydrocarbon compound containing at least fluorine is formed on the surface of these dielectric films. It is. Compounds containing fluorine include polyvinylidene fluoride and polyvinyl fluoride. Various types of dielectric films, such as vinylidene fluoride and vinyl fluoride films, have been proposed as dielectric films made of these hydrocarbon compounds containing fluorine. Compared to dielectric films such as polypropylene, tan δ is worse, and it is known that the electrical withstand voltage is significantly inferior, and in fact, the film potential gradient of polyvinylidene fluoride film is about 113 to 1 that of polypropylene film. ing.
Therefore, it is only in the present invention that uses a dielectric film that does not contain fluorine that thinning of the dielectric film and improvement in breakdown voltage can be achieved.

A detailed description will be given below with reference to the drawings.

Figure 1 shows a capacitor constructed using a metalized film on one side. In the figure, 1 is a fluorine-free dielectric film such as polyethylene terephthalate, and 2 is a thin film formed on both surfaces of the dielectric film 1. A carbon hydrogen compound containing fluorine, such as polyvinylidene fluoride or polyvinyl fluoride, 3 is formed on one side by vapor deposition or the like and has a sheet resistance value of 5.
The electrode is made of copper, aluminum, etc. with a resistance of 0Ω/Sq or more. 2 and 3 show capacitors constructed using double-sided metallized films, and the same parts are given the same reference numerals.

In Fig. 2, 4 is a fluorine-free dielectric film such as polyethylene terephthalate on which a fluorine-containing hydrocarbon compound 2 is formed on both surfaces, and a capacitor is constituted by the dielectric film 4 and a double-sided metalized film. It is. FIG. 3 shows a capacitor constructed using double-sided metallized films so that adjacent electrodes have the same potential. In the capacitor configured as described above, when a voltage is applied between both electrodes and a partial discharge occurs at the end of the electrode, the mass compound 2 is decomposed by the discharge energy.

General hydrocarbon compounds vaporize in the form of hydrocarbons, but in the case of hydrocarbon compounds containing fluorine, hydrogen vaporizes in the form of hydrogen fluoride, leaving behind free carbon or a reaction with a relatively large amount of free carbon. produce a product. Due to their conductivity, these substances have the effect of relaxing the electric field at the end of the electrode and suppressing partial discharge, thereby minimizing deterioration of the dielectric film 1 and the compound 2. This effect is similar to the electric field concentration around the electrode where self-healing occurs. Therefore, scattering of the electrode caused by partial discharge can be suppressed, and as a result, changes in capacitance can be reduced. On the other hand, since the electrode 3 has a large sheet resistance value, it has the effect of reducing the energy during self-healing, which reduces the decrease in the area of the electrode, and also prevents deterioration of the dielectric and film. As a specific example, we prototyped a capacitor A using an 8 μm polyethylene terephthalate film with a 1 μm thick polyvinyl fluoride film formed on its surface in the configuration shown in FIG. A comparison with prototype capacitor B made of polyethylene terephthalate film is shown in FIG. 4 in terms of survival rate in a life test at 600C. The test voltage was applied at 450 cm. From the results shown in FIG. 4, it is clear that capacitor A has a high breakdown voltage. Incidentally, among the capacitors constructed using FIGS. 1 to 3, the capacitor shown in FIG. 3 can have a thinner film or an improved withstand voltage.

In other words, in the capacitor shown in Fig. 3, since it is constructed using double-sided metalized films, no voids are generated between the double-sided metalized films due to the same potential, and therefore no hoid discharge occurs. Since this does not occur, it is possible to make the film thinner or improve its pressure resistance.

On the other hand, in the capacitors shown in FIGS. 1 and 2, there are new areas where voids exist between the metalized films on one side and between the metalized films on both sides and the non-metalized films.
Poid discharge needs to be taken into account, and the present invention exhibits great effects in this regard as well.

That is, when a poid discharge occurs between the electrode 3 and the compound 2, the compound 2 deteriorates and decomposes, generates free carbon, and due to its conductivity, the inside of the hoid is brought to the same potential, and the hoid discharge is stopped. Therefore, it is possible to prevent the electrode 3 and the compound 2 from deteriorating, and it is possible to make the film thinner or to improve the withstand voltage. In addition, the sheet resistance value of the electrode was set to 5.0.
The effect became even more remarkable when the resistance was increased to Ω/Sq or higher.

As described above, according to the present invention, it is possible to reduce the thickness of the film or improve the withstand voltage, thereby contributing to miniaturization of the capacitor.

[Brief explanation of the drawing]

1, 2, and 3 are sectional views of a capacitor before winding in an embodiment of the present invention, respectively, and FIG. 4 is a characteristic diagram showing the relationship between capacitor life time and survival rate. 1... Dielectric film, 2... Fluorine-containing hydrocarbon compound, 3... Electrode, 4...
・Dielectric film.

Claims (1)

[Claims] 1. A single-sided or double-sided metalized film in which a hydrocarbon compound containing at least fluorine is formed in the form of a thin film on the surface of a dielectric film that does not contain fluorine, and electrodes are formed on one or both sides of the dielectric film. A capacitor characterized in that it is configured using 2. The capacitor according to claim 1, wherein the electrode has a sheet resistance value of 5.0Ω/sq or more.