In the present invention, preferably conventional synthetic resins are used as the organic resin, for example, polyamides, such as nylon 6, nylon 11, nylon 66 and nylon 612; polyesters, such as polyethyleneterephthalate and polybutylene-terephthalate; polycarbonates, such as poly-bis-phenol A and carbonate; polyamide-imide; polyphenylene-sulfide; polyphenylene oxide; polysulfone; polyolefin; styre