Fabrication and Characteristics of Bend-durable,Colorless Transparent Polyimide Films for Flexible Display Cover Applications
As the display industry evolves,the research and development of colorless transparent polyimide(CPI)films for use in flexible display covers have become increasingly prominent.This study leverages commercial anhydrides and diamine monomers to fine-tune the main chain structure,fluorine content,and intermolecular hydrogen bonding,thereby achieving an equilibrium among transparency,dimensional stability,thermal resistance,and mechanical strength of the films.The produced CPI-2-TF film showcases exceptional optical average transmittance(Tav>88%),along with minimal coefficients of thermal expansion(CTE)(<1.3×10-5 K-1),elevated glass transition temperatures(Tg)(≥380 ℃),and superior mechanical properties.These attributes establish a robust foundation for the commercialization and mass production of CPI.Moreover,this study specifically examines the bend-durability of CPI-2-TF.After 2×105 bending cycles,the film maintained over 99%of their original average transmittance(Tav)and exhibited a mere 4%decrease in mechanical properties.Upon extending the bending to 400k cycles,the films retained virtually unchanged optical performance and over 92%of their mechanical integrity,demonstrating high potential for applications in folding screen smartphones and similar devices.