UNIAXIALLY ORIENTED POLYETHYLENE TEREPHTHALATE FILM FOR LIQUID CRYSTAL DISPLAY ELEMENT

摘要

PURPOSE:To prevent the coloration by the interference of liquid and the generation of a flaw, etc. on the surface of a film by adjusting the differences in the respective values of the refractive indices in the three directions of the film and dispersing the inorg. pulverous particles of specific grain sizes in the film. CONSTITUTION:The inorg. particles having 0.01-2mum average grain size are dispersed at 0.001-0.1wt% in the film having (nalpha-nbeta) ranging 0.08-0.12 and (nalpha-ngamma) ranging 0.15-0.21, where nalpha is the refractive index in the main orientation direction, nbeta is the refractive index in the direction perpendicular to the main orientation direction and nalpha is the refractive index of the film thickness direction. The differences in the respective values of the refractive indices nalpha, nbeta, ngamma of the uniaxially oriented polyethylene terephthalate film are kept within the above-mentioned ranges, by which the coloration by the interference of light is eliminated. The generation of defects such as flaws owing to the ruggedness of the film is prevented by dispersing the particles in the film in the above-mentioned manner. The liquid crystal display element using this film is free from the coloration to rainbow colors and spot-like defects. The display thereof is therefore easily readable and the resistance to heat and moisture is improved. Such element is used for various liquid display apparatus.