JPH0476487B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a coating dielectric film for a film capacitor used in electronic and electrical equipment.

Prior Art Conventionally, film capacitors have used films made 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 the surface of a metallized film and then laminated or wound to form a film capacitor. This method eliminates the need to handle the thin film alone and has very high productivity. Polycarbonate is the only plastic material that has been put into practical use as a dielectric material.

Problems to be Solved by the Invention The methods described above, that is, the method of forming a thin film of plastic on a metallized film, include a method of coating and curing thermosetting plastic, and a method of dissolving soluble plastic in a solvent and coating and drying. It can be broadly divided into methods. 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, but it is sufficient to achieve the desired film thickness after drying. Further, the energy required for drying and solidifying is less than the energy required for curing the former, and the productivity is also high.

Furthermore, since the coating dielectric formed into a thin film is used as a dielectric, uniformity of the film is important. The characteristics required of the coating film as a dielectric are not only the uniformity mentioned above, 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 coated and dried, the resulting coating dielectric film has a very rough surface, and the solution containing polyphenylene oxide also has a short pot life. The problem arises.

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 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 you use a paint with good wettability and low viscosity, it will run off before it dries after application.
The inconvenience of being applied to areas other than the intended areas also occurs.

As described above, there are many problems when attempting to form a coating dielectric film suitable for the purpose.
It is very difficult to solve all these problems when using a single solvent, and many types of solvents must be used. A method of using a mixture of many types of solvents has been put into practical use, for example, for paints such as household paints. However, the application of the present invention is
The usage is very different from household paint etc.
In this case, the demands are very strict.

Therefore, the present invention provides a combination of solvents that dissolves polyphenylene oxide and satisfies the uniformity of the coating dielectric film, the amount of residual solvent, the pot life of the solution containing polyphenylene oxide, etc.

Means for Solving the Problem In order to solve this problem, the present invention forms a coating material on a base material by dissolving at least 3% by weight of polyphenylene oxide in a mixed solvent containing at least dichloromethane and trichloroethylene. It is something.

Function The present invention uses trichlorethylene that easily dissolves polyphenylene oxide, that is, has a high solubility, and a solvent that mainly contains trichlorethylene to increase the stability (pot life) of the paint in which polyphenylene oxide is dissolved. This is the result of finding a system. In addition, dichloromethane has a low boiling point of 40℃.
Because of this, it can be dried to dryness, which requires less energy. Trichlorethylene has a high boiling point, and when dried, it remains even after dichloromethane has been deposited and dries gradually, minimizing the roughness of the film surface after coating.

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

Example Polyphenylene oxide was mixed with 1 part of dichloromethane,
It was dissolved at 5% by weight in a solvent mixed with 1 part trichlorethylene and 1 part toluene, and applied by gravure coating onto a 5-micron-thick polyethylene terephthalate substrate with vacuum-deposited aluminum, and heated in a hot air bath at 60°C for 3 seconds. Passed through to dryness. In this case, the thickness of the coating derivative after application and drying is approximately 1 micron, and the surface roughness or maximum thickness is 1.15 μm.
The minimum thickness was 0.9 microns. When a multilayer capacitor was made using the film formed by the method described above, the withstand voltage level was approximately 50, which was excellent.

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

In this example, 5% 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. Furthermore, when applying a thick coating dielectric film, the mixed solvent of the present invention has problems such as leaving too much residual solvent, and when applying the coating to an extremely thin film of 0.2 microns or less, the present invention If a mixed solvent is used, the solvent dries too quickly and the resulting coating dielectric film has an uneven thickness. Therefore, with the mixed solvent of the present invention, the thickness of the coating dielectric film is
It is effective when applied to a thickness of 0.2 to 5 microns.

Effects of the Invention As described above, according to the present invention, polyphelene oxide can be formed into a thin film by dissolving it in a solvent and applying and drying it, and by using trichlorethylene and dichloromethane as the main components,
It is uniform and has excellent characteristics as a dielectric material for capacitors.

[Brief explanation of the drawing]

The figure is a diagram showing a comparison between the breakdown voltage level of the coating dielectric film of the present invention and the breakdown voltage level of the coating dielectric film prepared using a single solvent.

Claims (1)

[Claims] 1 A paint made by dissolving 3% or more of polyphenylene oxide resin in a mixed solvent containing at least dichloromethane and trichloroethylene,
A method for forming a coating dielectric film, which comprises coating a polyphenylene oxide film on a metallized film to a thickness of 0.2 to 5 microns and drying it.