Abstract
The effect of varying the dielectric anisotropy, Δε on the electro-optic behaviour of an achiral SC layer has been studied using the frequency dependent dielectric anisotropy of a pyrimidine mixture. A field dependence of the optical extinction angle was observed at frequencies corresponding to Δε >0, Δε = 0 and Δε<0. Switching at frequencies for which Δε = 0 is interpreted using a biaxial dielectric tensor. It is proposed that dielectric biaxiality causes the AC field effects observed in ferroelectric liquid crystal devices with the surface stabilized geometry.