New Colorless Substrates Based on Polynorbornene-Chlorinated Polyimide Copolymers and Their Application for Flexible Displays

Novel polynorbornene (PNB)-polyimide (PI) copolymers were synthesized based on poly(N-phenyl-exo-norbornene-5,6-dicarboximide) (PPhNI) and chlorinated PI (BPDA/TCDB). Polynorbornene copolymers (PNCs) with diverse compositions of anhydride were synthesized via ring opening metathesis polymerization (ROMP) of N-phenyl-exo-norbornene-5,6-dicarboximide (PhNI) and exo-7-oxanorbornene-5,6-dicarboxylic anhydride(exo-NA), followed by copolymerization through a reaction with aromatic dianhydride (3,3',4,4'-biphenyltetra-carboxylic dianhydride, BPDA) and tetrachlorinated diamine (2,2',5,5'-tetrachlorobenzidine, TCDB). The copolymer (PNIC) films exhibited good optical transparency with a transmittance of around 70% at 400 nm and a good thermal stability with a glass transition temperature at 276-300 degrees C . These flexible films also resisted most organic solvents and chemicals, such as methanol, acetone, tetrahydrofuran, N-methyl pyrrolidone, ethyl acetate, hydrochloric acid, sodium hydroxide, and hydrogen peroxide, etc. Indium tin oxide (ITO) coated thin films were prepared at various substrate deposition temperatures with a radio frequency (r.f.) planar magnetron sputtering system. The ITO thin films that were deposited onto the PNIC copolymer substrates had good electrical and optical properties. An organic light-emitting device (OLED) was fabricated using the PNIC copolymer substrate with a structure of PNIC08/ ITO (anode)/hole-transporting layer (HTL)/emitting & electron-transporting layer (EM&ETL)/aluminum (cathode). The flexible OLED fabricated on the ITO-grown PNIC substrate exhibited a performance that was comparable to corresponding ITO-grown glass substrates. Therefore, the ITO-grown PNIC substrate could possibly be a promising candidate as a substrate for flexible displays. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1806-1814, 2010