New supertwisted nematic liquid crystal display geometry with improved response times and optical characteristics

Abstract

A new general formalism for finding the optical fields propagating obliquely in layered-inhomogeneous anisotropic media has been obtained and can he used to obtain a general analytic solution for the optical fields in the general inhomogeneous anisotropic media. The results were applied to study the optical properties of general twisted nematic (TN) and supertwisted nematic (STN) liquid crystal displays (LCDs). From the general expression for the field-off state optical transmission for the STN LCDs, we obtained a simple expression for the polarizer orientations, for which the field-off state transmission has an extreme value under parallel or crossed polarizers. For the 180° STN LCDs with parallel polarizers configuration, there are two possible optimized polarizer orientations; one polarizer condition describes the standard 180° STN LCD, and the second polarizer condition describes the black and white 180° optical mode interference (OMI) LCD. However, with crossed polarizers, a new STN geometry with different polarizer arrangement and different optimal conditions from the conventional STN is obtained. The new STN LCD gives a factor of about one-half improvement in both the switching-on and switching-off time constants, and oilers a much improved optical response as compared to the conventional STN LCD. © SPIE.