A novel type of inverted dichroic display employing a positive dielectric anistropy liquid crystal

Two versions of a novel dichroic guest-host liquid-crystal display are described which exhibit positive contrast and employ an optically active material, an dichroic dye, and a positive dielectric anisotropy nematic liquid crystal. The working principle is based on the fact that in the area outside the digits, critical conditions are established which prevent the formation of a cholesteric helicoidal structure. This gives rise to a homeotropic structure and, therefore, a transparent state. In the off state the digits appear colored on a bright background. In both cases electrooptic behavior and response times are compared to the normal negative contrast guest-host system described by White and Taylor.