METHOD FOR PRODUCING COLORLESS AND TRANSPARENT POLYIMIDE FILM IMPREGNATED WITH GLASS FABRIC AND PLANARIZING SURFACE THEREOF

摘要

The present invention relates to a method for producing a polyimide film, the method comprising a two-stage planarization step for planarizing the surface of a colorless and transparent polyimide (CPI) film impregnated with a glass fabric by a roll-to-roll process, and the purpose of the present invention is to solve a problem of an increase in the surface roughness of a polyimide substrate, which inevitably occurs when a glass fabric is impregnated into a colorless and transparent polyimide film in order to improve thermal and mechanical properties of a film that is used for a flexible display substrate and a cover window of a flat panel display or a cellular phone. According to the present invention, the surface of a colorless and transparent polyimide film impregnated with a glass fabric is planarized such that the roughness thereof is reduced from a range of about several tens of nanometers to several microns to about several nanometers, which enables a TFT process to be carried out on a substrate made of the colorless and transparent polyimide film, and increases the optical transmittance and transparency of the colorless and transparent polyimide film, thereby allowing the colorless and transparent polyimide film to be used for a flexible display substrate and a cover window of a flat panel display or a cellular phone.