| abstract |
A transparent polyimide film with low birefringence, high glass transition temperature (T g ) consists of polyimide essentially comprising non-linear structure. This polyimide is prepared by a mixture of dianhydrides and diamines, comprising at least 10 mol % of asymmetric dianhydride and 50 mol % or less of meta-substituted diamine. This transparent polyimide film has a transmittance of 85% or more at 550 nm, a birefringence value of 0.005 or less and a T g of 300° C. or more. The present invention relates to the low birefringence required electro-optic field, including the substrate and cover window for flexible OLED and LCD displays. |