Consequently examples of the crosslinked polymer include, among the above-mentioned thermoplastic resin, thermosetting resin, elastomer and rubber which give light transmitting properties, polymers obtained by crosslinking resins such as a polyurethane resin, an epoxy resin, a polyacrylic resin, an unsaturated polyester resin and a vinyl ester resin (except for a polyacrylic resin), a diene-based