JPS6164004A - Film for capacitor and capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a capacitor film whose surface is not roughened, and a capacitor using the entire film.

Note that the term "film" here includes both sheets and films.

BACKGROUND OF THE INVENTION In recent years, with the rapid development of electronic devices, the production volume of various capacitors used in these devices has increased, and demands for their quality have also increased.

In particular, for wound type capacitors and metallized film capacitors, wound capacitors using polyethylene terephthalate film or polypropylene film have been widely studied.

Because polypropylene film has a relatively low melting point, it is not possible to raise the curing temperature of the epoxy resin used as a sealant to the required 120-140°C during capacitor manufacturing, and complete curing cannot be achieved. However, it had the disadvantage of not being sufficiently moisture resistant. Furthermore, if the temperature during curing is set to 110° C. or higher, the polypropylene film will shrink and the capacitor function will be lost.

In addition, 44 times poly-4-methylpentene-1 (hereinafter referred to as TPX) was added to a polypropylene film to improve the insulating oil impregnation properties of a capacitor using a polymer film whose surface was roughened by biaxial stretching. Also, inventions have been proposed to improve the adhesive strength of metal vapor deposition.

Problems to be Solved by the Invention The inventor first found that by combining TPXeC with polypropylene, the thermal properties of the mixed film were improved, and even if the curing temperature of the epoxy resin was increased to 120°C or 140°C,
It has been found that the mixed film does not soften or shrink and does not lose its capacitor function. By increasing the curing temperature in this way, the epoxy resin is completely cured, improving temperature resistance, which is an important characteristic of capacitors, extending capacitor life, and increasing productivity by enabling shorter curing times. I found out what to do.

Next, TPX has conventionally had excellent electrical properties and exhibited the lowest dielectric loss among synthetic resins, but it has high temperature dependence and reaches its maximum loss angle at approximately 85°C in a single film. Therefore, when used as a capacitor in AC circuits, pulse circuits, etc., self-heating is large, and its use at high frequencies and high temperatures is restricted. However, as mentioned above, by mixing it with polypropylene, the peak of dielectric loss can be reduced. It was found that the loss angle shifted to the lower temperature side and the loss angle also decreased. Therefore, the use of mixed films of TPX and polypropylene allows use in a wide range of current capacities, frequencies, and temperatures, especially for the production of high current, high frequency, high temperature capacity capacitors for electronic equipment. Since this makes it possible to use this method, its applicability to switching regulator circuits, etc., which are in high demand recently in electronic equipment, has become great.

Next, the film of the present invention is characterized in that the surface is not roughened. Therefore, even if it is not stretched or stretched, it is treated as uniaxial stretching,
The thickness should be set to a level that does not impair the layering of the film. Because the film is smooth, there is less air entrapment during element winding, and the amount of partial discharge charge is reduced, making it highly applicable as an AC capacitor. Regarding the concern that the adhesive strength to the film surface is low, there is no problem because the adhesive strength is improved by performing corona treatment before vapor deposition.

Means/effect for solving the problems Based on such excellent knowledge, the present invention has been completed. That is, the structure of the present invention is based on polypropylene and T.
This is a capacitor characterized in that the unstretched or uniaxially stretched film made of a mixture with PX, metal foil, and the metallized film on which metal is vapor-deposited are wound. The configuration requirements etc. will be explained below.

In the present invention, polypropylene refers to ordinary isotactic polypropylene homopolymers and copolymers obtained by adding other α-olefins to isotactic polypropylene, including poly-4-methylpentene-1 (TPX).
refers to the same homopolymer and a copolymer obtained by adding another α-olefin to the same homopolymer.

The mixing ratio of polypropylene and TPX is 10 to 90 rL of TPX to the total amount of both! , q%, good luck Ha3
When the ratio is 0 to 70%, the advantages of both are exhibited, and the mixture -Y may be changed as appropriate depending on the desired capacitor function.

The film can be manufactured using normal film manufacturing methods, such as tri-blending pellets of both polymers, or kneading them in an extruder, and forming a film using the standard T-Guy method or inflation method. Although non-stretching is preferable, uniaxial stretching may be performed to the extent that smoothing of the surface is not impaired.

The following is an explanation based on examples.

Example Table 1 shows the temperature values and wax values showing the dielectric loss or the best crystal value when the blend ratio of PP/TPX was changed, and the curing temperature of the epoxy resin sealant was set within 120 to 140 °C. The characteristics of the capacitor are shown below.

According to Table 1, PP/TPX = 30/90~70/3
0 indicates excellent J5 main loss and capacitor function. 5 dynamic tan δ%, 4 rad completion In addition, a capacitor using the capacitor film of the present invention has a lower dynamic tan δ% than a capacitor using a biaxially stretched film made of the same mixture of polypropylene and poly-4-methylpentene-1. It is characterized by a small rate of change in capacitance.

Effects of the Invention As detailed above, the capacitor made using the film of the present invention has a small dielectric loss, so even when used in an AC circuit, etc., it generates a small amount of heat, has good moisture resistance, and exhibits other excellent capacitor characteristics. As a capacitor for large current, high frequency, and high temperature, it is most suitable for use in the field of electronic equipment such as switching source AC circuits, pulse circuits, and resonant circuits, and therefore the present invention greatly contributes to the development of industry.

Claims (1)

[Claims] 1. A non-stretched or uniaxially stretched capacitor film made of a mixture of polypropylene and poly-4-methylpentene-1. 2. A capacitor comprising a non-stretched or uniaxially stretched film made of a mixture of polypropylene and poly-4-methylpentene-1, a metal foil, and the metallized film on which a metal is vapor-deposited.