No 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.