High contrast ratio of a vertically aligned liquid crystal cell using photocrosslinking alignment

Abstract

A photo-induced alignment layer for LCDs has been successfully fabricated using the polarized UV photoreaction of a photo-crosslinkable polymer with the incident UV light at some angle with respect to the cell normal. The surface alignment and electro-optic properties were investigated for various UV exposure times. The homeotropic alignment layer showed a discrete anisotropic dichroic ratio, its surface morphology became smoother as the UV exposure time increased, and the LCs were arranged in a perpendicular direction to the PUVL direction with a proper pretilt angle. The cell showed no defects under cross-polarized microscopy and the contrast ratio was as high as 550:1 in transmittance. The contrast ratio pattern was found to be very similar to that of dichroic ratio as a function of UV exposure time and depended upon the frequency change to some degree. The response time was also investigated.