1. Department of Solid State Electronics, Osaka Electro-Communication University, 18-8 Hatsu-cho, Neyagawa, Osaka 572, Japan
2. Chemical Research Center(Ube), Central Glass Co. Ltd, 5253 Okiube, Ube, Yamaguchi 755, Japan
3. Division of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606, Japan