P‐6.7: End‐Capped Transparent Polyimide Films with Improved Thermal Durability for Optoelectronic Application

Abstract

To meet the application demands as flexible substrate materials in optoelectronic display fields, the thermal durability at high temperature of transparent polyimide (PI) films faces a great challenge. Eight types of end‐capped transparent PI films were prepared using four end‐capping reagents through thermal and chemical imidization methods, respectively. The effects of end‐capping reagents with different chemical structures and imidization methods on optical properties of end‐capped films were investigated systematically. Their thermal durability in transparency was evaluated by changes of light transmittance and yellow parameter (ΔT and Δb) between the original and reheated end‐cappedfilms at 300 °C in the air. The results proved that end‐capping reagents and imidization methods have an important effect on optical properties of end‐capped PI films. It is also demonstrated that optimal end‐capping reagent combined with appropriate imidization method can enhance the thermal durability of transparent PI films. It provides an effective method to solve the discoloration problem of transparent PI films caused by high temperature during device manufacturing.

High-Transparency and Colorless Polyimide Film Prepared by Inhibiting the Formation of Chromophores

“…In previous studies, norbornene [ 37 ] or dianhydride [ 38 ] end-cappers were introduced into photosensitive polyimide’s precursor, to obtain polyimide films with desirable mechanical properties, or used in thermosetting polyimides known as bisnadimide (or PMR) resin; bisphthalonitrile [ 39 ], phenylethynyl groups [ 40 ], and acetylene-terminated polyimides [ 41 ] were also used to prepare the thermo-cured resin; polycyclic arenes were used as blockers to synthesize hyperbranched polyimides [ 42 ]; and acetic anhydride, hexahydrophthalic anhydride, o-phthalic anhydride, and endic anhydrides were used as end-capping reagents to prepare transparent PI films [ 43 ], but these anhydrides might produce the colored Morkit units as shown in Scheme 1 .…”