Organic/Inorganic-Polyimide Nanohybrid Materials for Advanced Opto-Electronic Applications Shinji Ando * Department of Chemistry & Materials Science, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo 152-8552, JAPAN ABSTRACT Nano-hybridization techniques based on the pyrolytic reactions of organo-soluble metallic precursors dissolved in poly(amic acid)s followed by spontaneous precipitation of metal/inorganic nano-particles in solid polyimide (PI) films is facile and effective for functionalization of PI optical and electronic materials. The organic/inorganinc PI nanohybrid materials, which were recently developed by the authors, having a variety of functionalities such as a) high refractive indices, b) low refractive indices, c) controlled thermo-optical property and its anisotropy, d) high polarizing property, and e) high thermal conductivity are reviewed with future prospects on their advanced opto-electronic applications. Keywords: Nanohybrid, nano-particles, polyimide, refractive index, birefringence, thermo-optic coefficient, polarizer, thermal conductivity, phase separation, double percolation 1. INTRODUCTION The advantages of polymers in the application to optical components, such as micro-lens for CCD/CMOS image sensors, thin films and anti-reflective coatings for flat-panel displays (LCD and OLED), and waveguide circuits in optical interconnects and telecommunications, are 1) facile formation of thin films at lower temperatures, 2) light-weight, toughness, and flexibility, 3) micro-patternability by phtolithography or imprinting, 4) wide range of molecular design, and 5) facile incorporation of metallic or inorganic dopants or nano-particles. 1-5 In contrast, the drawbacks of polymeric materials are a) low thermal stability, b) high moisture absorption, c) low environmental stability and durability, d) narrow range of controllable optical properties such as transmittance, wavelength range with high transparency, refractive indices, birefringence, and thermo-optic coefficients, and e) low thermal conductivity. Recently, with the rapid development of nano-science and nanotechnology, various methods to provide functional optical polymers have been revealed. In particular, nano-hybridization of polymers with metallic or inorganic nano-particles is a promising technique to overcome the drawbacks without reducing their inherent advantages. 6-9 When the sizes of nano-particles are smaller than 40 nm (~1/10 of the visible wavelengths), nanohybrid films are generally transparent. The sol-gel method is a wet- chemical process for the fabrication of metal oxide starting from a organic solution undergoing hydrolysis and polycondensation reactions followed by drying and thermal curing for further condensation and consolidation, and it is a promising technology. Since the sol-gel process uses organo-soluble compounds as source materials, it can afford metal oxide such as SiO 2 , ZrO 2 , ZnO, TiO 2 , Al 2 O 3 at much lower temperatures than thermal fusion method. Furthermore, polyimides (PIs) are generally cured at higher temperatures (250~400°C) than conventional optical polymers, which enables to use wider range of precursors as source materials for metallic and inorganic nano-particles. 10-14 2. HIGH REFRACTIVE POLYIMIDES High refractive index (high-n) and low birefringence (Δn) combined with good thermal stability and high transparency are the basic concerns in designing polymer coatings for micro-lens applications. According to the Lorentz-Lorenz equation (1), the wavelength (λ)-dependent refractive index (n λ ) of a solid polymer can be expressed as vdw V K n n λ p 2 λ 2 λ 3 π 4 2 1 α = + − , (1) Invited Paper Organic Photonic Materials and Devices XI, edited by Robert L. Nelson, François Kajzar, Toshikuni Kaino Proc. of SPIE Vol. 7213, 72130B · © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.814976 Proc. of SPIE Vol. 7213 72130B-1