Optimization of antiferroelectric liquid crystal devices at the degeneration point

Abstract

Antiferroelectric liquid crystals (AFLCs) with 45° tilt angle have been shown recently [K. D’hav’e, Per Rudquist, S. T. Lagerwall, H. Pauwels, W. Drzewinski, and R. Dabrowski, Appl. Phys. Lett. 76, 3528 (2000)] to exhibit true dark state between crossed polarizers at normal incidence. We show that this situation is possible at any incidence or any tilt angle depending on the principal dielectric constants ε1–3. In particular, when the deviation of ε1 from the average (ε2+ε3)/2 is small, the medium behaves nearly as isotropic medium. Hence using this class of AFLC materials it will be possible to build full color, high-resolution displays with large viewing angular range. The optimum viewing angular cone will be obtained when the degeneracy point corresponds to 45° incidence angle and tilt angle anywhere from 0 to 45° depending on the values of the principal dielectric constants and, in particular, on the biaxiality. For the uniaxial case this angle is practically 41°–42° without dependence on the optical anisotropy.