P‐250: Highly Transparent Optical Window Film with Outstanding Mechanical Strength and Folding Reliability for Flexible Displays

Abstract

This research presents a new approach to developing an optical window film, leveraging the concept of charge‐transfer complex (CTC) intensification of colorless polyimide The window film demonstrates exceptional characteristics, including a tensile modulus of 8.4 GPa, a high total light transmittance of approximately 90%, and a yellow index below 3. This is the best‐recorded balance between mechanical strength and optical properties for a highly flexible optical film. Furthermore, the resulting film exhibits a pencil hardness grade surpassing 2H, alongside remarkable folding reliability, sustaining over 200,000 cycles of folding and unfolding. The excellent properties are ascribed to the unique supramolecular structure characterized by multiple hydrogen bonding and salt complexation interactions, significantly enhancing CTC intensification.