Abstract: A method of preparing a colorless transparent copolyamide-imide resin solution and its fabrication as a thin film has been disclosed. The method details formulations derived from a reaction between one or more units of dianhydride and one or more units of diamine monomers with one or more of the monomers containing fluorine atoms in their structural unit. It enables the fabrication of thin films with superior thermal and mechanical properties along with co-efficient of thermal expansion values as low as 2 ppm/° C. and a tensile modulus as high as 9 GPa. The transparent copolyamide-imide film thus prepared has the potential for utilization in flexible displays such as substrates for thin film transistors (TFT), touch sensor panels (TSP) and cover window in organic light emitting diode (OLED) and liquid crystal display (LCD) applications.

Abstract: A polyimide film contains fluorinated substituents and cardo structures. The polyimide film exhibits excellent heat-resistance, transparency and mechanical properties. The polyimide film has a glass-transition temperature (Tg) of at least 360° C., a coefficient of thermal expansion (CTE) of 50 ppm/° C. or lower, a modulus of at least 4.0 Gpa, a b* value of 5 or lower and yellowness index of 8 or less. The polyimide film can be used as a display substrate or an optical film in a liquid crystal display (LCD), an organic light-emitting diode (OLED) and in other fields where the characteristic features are required.