JPS629615A - Formation of coated dielectric film - 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 method for forming a coating dielectric film for a film capacitor used in electronic and electrical equipment.

BACKGROUND OF THE INVENTION The dielectric material of conventional film capacitors has been a film formed by melting or solution-casting plastic. However, in recent years, as devices have become smaller, there has been a growing demand for smaller film capacitors.

Therefore, a method was devised in which a thin film of plastic is formed on both sides of a double-sided metallized film and then laminated or wound to form a film capacitor. This method eliminates the need to handle a thin film alone and has very high productivity. On the other hand, polycarbonate is the only plastic material that has been put into practical use as a dielectric material.

Problems that the invention seeks to solve The methods described above, that is, the method of forming a thin film of plastic on a double-sided metallized film, include a method of coating and curing a thermosetting plastic, and a method of dissolving a soluble plastic in a solvent. It can be roughly divided into two methods: coating and drying. The former is very difficult to apply in the form of a thin film, and a large amount of energy must be applied to cure it.

On the other hand, in the latter method, since a thin film is formed from plastic dissolved in a solvent, it is not necessary to achieve the desired film thickness at the time of coating, and it is sufficient to achieve the desired film thickness after drying. In addition, the energy required for drying is less than the energy required for curing the former, and productivity is high.

Furthermore, since the coated dielectric material formed into a thin film is used as a dielectric material, uniformity of the film is important. The characteristics required of the coating film as a dielectric are not only the above-mentioned uniformity, but also the amount of solvent remaining in the dielectric after forming the coating dielectric (hereinafter referred to as residual solvent), the surface roughness of the coating dielectric, etc. It becomes a problem. For example, when polyphenylene oxide is dissolved in a single solvent and applied and dried, the resulting coating dielectric film has problems such as a very rough surface and a short pot life for the solution containing polyphenylene oxide. arise.

Next, when forming a coating dielectric film, the wettability of the paint for forming the coating dielectric film with the base material is important. If the wettability is poor, the paint will repel and be uniform when applied to the base material. Problems arise, such as the inability to form a suitable film.

Furthermore, if a paint with good wettability and low viscosity is used, the paint will run off before it dries after being applied, resulting in the inconvenience of being applied to areas other than the intended areas.

There are many problems when trying to form a coating dielectric film suitable for the above purposes.

It is very difficult to solve all these problems when using a single solvent, and many types of solvents must be used. The method of mixing and using many types of solvents is
For example, it has been put to practical use in household paints and other paints. However, the application of the present invention is completely different from that of household paint, and in this case, the requirements are very strict.

In order to solve this problem, the present invention proposes a combination of solvents that can dissolve polyphenylene oxide and satisfy the uniformity of the coating dielectric film, the amount of residual solvent, and the pot life of the solution in which polyphenylene oxide is dissolved. In the present invention, a coating material is formed on a base material by dissolving 3 percent by weight or more of polyphenylene oxide in a tr mixed solvent containing at least dichloromethane and monochlorobenzene.

In the present invention, we have discovered a solvent system whose main components are dichloromethane, which easily dissolves polyphenylene oxide, that is, has high solubility, and monochlorobenzene, which increases the stability (pot life) of paints in which polyphenylene oxide is dissolved. It is.

In addition, dichloromethane has a low boiling point (40"C), so it requires low energy when drying. Monochlorobenzene has a high boiling point, and when drying, it remains even after the dichloromethane is vaporized and gradually dries, forming a film after coating. Minimize surface roughness.

Furthermore, in the case of the application of the present invention, the base material is often a plastic film metalized with metal such as aluminum or zinc. This problem can also be solved.

Example Polyphenylene oxide was dissolved at 5% by weight in a solvent mixed with 1 part dichloromethane, 1 part monochlorobenzene, and 1 part toluene, and applied by gravure coating onto a substrate made of 6 micron thick polyethylene terephthalate with aluminum vacuum-deposited. The mixture was passed through a hot air tank at 60° C. for three times to dryness. In this case, the thickness of the coating dielectric after drying is approximately 1 micron, and the surface roughness is approximately 1 micron.
・It was 16 microns, and the minimum thickness was 0.9 microns.

When a multilayer capacitor was manufactured using the film formed by the method described above, the withstand voltage level was approximately 50V, which was excellent.

FIG. 1 shows a comparison of breakdown voltage levels between a coated dielectric film produced by the manufacturing method of the present invention and a coated dielectric film formed by dissolving only dichloromethane.

In this example, 6% by weight of polyphenylene oxide was dissolved, but if it is 3% by weight or more, there is no problem, but in the following cases, the influence of the solvent is large, causing problems with uniformity and residual solvent. Further, when coating the dielectric film thickly, the mixed solvent of the present invention has problems such as leaving too much residual solvent, but it is effective when coating the dielectric film to a thickness of 0.2 to 6 microns.

Effects of the Invention As described above, according to the present invention, it is possible to form a thin film by dissolving polyphenylene oxide in a solvent, applying and drying it, and by using monochlorobenzene and dichloromethane as the main components of the solvent, a uniform capacitor can be formed. Excellent properties can be obtained as a dielectric material for applications.

[Brief explanation of drawings]

The diagram shows the breakdown voltage level and single unit of the coating dielectric film of the present invention.
FIG. 3 is a diagram showing a comparison of breakdown voltage levels of coated dielectric films made with solvents.

Claims (1)

[Claims] (1) A paint made by dissolving 3 percent by weight or more of polyphenylene oxide resin in a mixed solvent containing at least dichloromethane and monochlorobenzene is applied onto the base material as a polyphenylene oxide film in a thickness of 0.2 to 5 microns and dried. A method for forming a coating dielectric film, characterized in that: