Field-induced Colour Change of Liquid Crystalline Dyes

Planar oriented nematic layers and also partially oriented smectic C phases of certain diphenyl-1,2,4,5-tetrazine compounds due to their positive dielectric anisotropy can be oriented by an electric field (Freedericksz-transition). The orientation is connected with a distinct change of absorption respectively colour. The mechanism of the effect is discussed. For both liquid crystalline phases the response times and decay times were measured.