The Generation of Biaxial Optical Anisotropies in Polyimide Films by an Uniaxial Stretch Method

摘要

A new biaxial-retardation film prepared from the uniaxial-stretched polyimide (PI) film was developed for compensating the viewing angle of liquid-crystal displays. A new aliphatic PI showing high transparence and low glass-transition temperature was firstly prepared for the biaxial-retardation film purpose. Both retardations in x-y and x-z planes of PI films were highly increased after stretching them uniaxially at 260℃. Good uniformity of birefringence in well-stretched PI films was observed visually with two crossed polarizers. The birefringence variations of ax - ny (difference of refractive indexes between x- and y-axes) and nx - nz during the stretching process were highly affected by PI structure.