Smectic liquid crystal devices

Claim 1

A liquid crystal device capable of being switched into two different liquid crystal molecular alignment states comprising: two cell walls; a layer of a tilted chiral smectic liquid crystal material contained between said two cell walls each of said cell walls including electrodes and surface treated to give homogeneous alignment direction to the liquid crystal molecules, the alignment directions being substantially parallel, said cell walls, said layer and electrodes forming a liquid crystal cell; and two polarizers arranged one on each side of said liquid crystal cell with the optical axis of one polarizer substantially crossed with respect to the optical axis of the other polarizer and with the optical axis of one polarizer substantially parallel to said alignment direction on said cell wall, and the liquid crystal material having a tilted chiral smectic phase at normal device operating temperatures and a cholesteric phase at a higher temperature, with a cholesteric pitch of at least the layer thickness in the cholesteric phase at least 0.1° C. above the cholesteric to smectic transition temperature, a net spontaneous polarization coefficient greater than 0.1 nC/cm 2 and the following phase with increasing temperatures: chiral smectic - cholesteric - isotropic.