Optical properties of a new bistable twisted nematic liquid crystal boundary layer display

In a new display cell, a holding voltage compresses the regions where the director is not essentially vertical into thin boundary layers adjacent to the surfaces. With opposite surfaces tilt biased in opposite senses, and with suitable isolation regions, the director field contains a horizontal director line. Above a certain threshold voltage the stable states are asymmetric, with the horizontal director line nearer one surface than the other. In a twist cell, these bistable states can be discriminated optically with either a dichroic dye and a single polarizer or with two polarizers using birefringence effects. A dye gives poor results because the horizontal absorbing layers are thin. However, the birefringence effects enable good contrast to be obtained. We examine the brightness and contrast by studying the transmission of monochromatic light passing normally through the cell in the two states. We include an analysis of polarized light propagating through two birefringent layers of arbitrary phase diff...