Mechanical Reliability Prediction of Foldable Displays Using Subcritical Crack Growth in Siloxane-Based Cover Window by Two-Point Bending Test

Abstract

Various novel materials have been researched to improve the performance of foldable displays. The foldable display includes thin-film multilayers and the cover window for anti-scratch is located at the top, making it the most vulnerable to breakage. Siloxane hybrid polymer is considered the most promising material for anti-scratch ability and flexibility. However, information for calculating the long-term reliability of such materials is seriously lacking. This paper suggests a method to predict the mechanical reliability of a foldable display based on the principles of fracture mechanics and statistics. Mechanical properties of siloxane coating were determined using two-point bending test that is non-contact test method suitable for mechanical test of thin films. The elastic moduli and Weibull characteristic strength of the polymer were obtained from the two-point bending test. Stress corrosion susceptibility parameter by subcritical crack growth was determined by measuring the fracture strain at various faceplate velocity conditions. Using Weibull characteristic strength and stress corrosion susceptibility parameter, the long-term reliability of the foldable display was predicted under various curvatures. The suggested method can be used to evaluate the long-term reliability of foldable displays more accurately.