Studies on the Synthesis of Ladder-structured Polysilsesquioxane for Flexible Cover Window

Abstract

As the flexible display market expands, there is an increasing demand for displays with reliable characteristics in various environments. In particular, the cover window located at the top of the display, unlike existing rigid types, needs to possess physical, mechanical, and optical properties while also withstanding the stresses caused by bending. Therefore, this study presents a coating layer for wear-resistance, anti-fragile properties, and low-temperature bending on ultra-thin glass (UTG). To accomplish this objective, we introduced a direct coating of ladder-like polysilsesquioxane (PSQ) onto UTG, aiming to attain flexibility and protective characteristics simultaneously. The resulting cover window demonstrated a pencil hardness of 8H, 1000 cycles of wear-resistance with 91% optical transmittance, and 200,000 reliable 3R in-bending. In addition, the properties of the PSQ coating layer at low temperatures were also studied. To complement the characteristics of PSQ, which brittles at low temperatures, we synthesized a poly(ethylene) glycol-based additive that can enhance the low- temperature bending characteristics of PSQ resin. As a result, we showed that the additive was effective for the PSQ coating on bending property at -20°C.