ELECTRIC-FIELD CONTROLLED COLOR EFFECT IN CHOLESTERIC LIQUID-CRYSTALSAND POLYMER-DISPERSED CHOLESTERIC LIQUID-CRYSTALS

In cholesteric liquid crystals with positive dielectric anisotropy an electric-field induced texture with unusual properties was observed. T his texture appears after the reduction of the electric field during t he transition from the homeotropic nematic state into the planar chole steric one. The angular and the electric-field dependence of the spect ral characteristics indicate that this state possesses diffractive gra ting properties. A voltage controlled color shift and a laser beam def lection are possible. An electric-field controlled cholesteric diffrac tive grating texture was also observed in polymer-dispersed films. In this case the electric-field induced transition into the homeotropic s tate is not necessary. (C) 1996 American Institute of Physics.