Characteristic improvements of glass-fabric reinforced hybrimer film for flexible display substrate

Abstract

Transparent flexible displays, which can be applied to various applications according to recent development of display technology, have attracted much attention in the industry. In order to make a transparent flexible display, a substrate material that is transparent and flexible is required because the bottom emission type where the back light comes from the top of the device through the substrate at the bottom. Polyimide (PI) substrate, which is mainly used as flexible substrate material, has higher heat resistance than other polymer materials, but it is not suitable for transparent display because of its lower transparency due to its deep yellow color. The colorless polyimide (CPI) film having improved transmittance has a limitation in being used as a substrate material due to its poor thermal stability and a high coefficient of thermal expansion (CTE). Therefore, in order to apply it to a substrate material, a device must be formed by a solution process, but these devices have limitations such as resolution and scan rate.

In this study, glass-fabric reinforced hybrimer films are proposed that complement the limitations of existing substrate materials. Organic-inorganic hybrid siloxane materials (hybrimers) synthesized by sol-gel reaction have high thermal stability like glass due to inorganic siloxane bond and have flexibility like polymer due to bonding of organic functional groups. The refractive index of these hybrid materials was controlled and impregnated within glass-fabric to produce glass-fabric reinforced hybrimer films with high thermal stability, transparency and low thermal expansion coefficient. And a UV curing type epoxy hybrimer based glass-fabric reinforced hybrimer film with high visible transmittance and a thermal curing type vinyl hybrimer based glass-fabric reinforced hybrimer film with excellent thermal stability are compared.

As a UV curing type epoxy hybrimer, previously reported non-hydrolytic sol-gel processed epoxy hybrimer was improved by hydrolytic sol-gel processed epoxy hybrimer, which has higher thermal stability, maintaining high optical transmittance of conventional one. The glass-fabric reinforced hybrimer film of each of the improved hydrolytic epoxy hybrimer and vinyl hybrimer were shown to be stable at 350 $^\circ C$, which is the process temperature of the oxide thin film transistor (oxide TFT). And by fabricating TFT on GFRHybrimer film, it is confirmed that GFRHybrimer film can be used as a substrate material. Furthermore, the laser lift off (LLO) process, a debonding process used in conventional displays, has been shown to be applicable to glass-fabric reinforced hybrimer film materials.