New type positive contrast guest-host display

Two versions of a new dichroic guest-host liquid crystal display are described, exhibiting a positive contrast (i.e. dark digits on a bright background) and using a mixture of nematic liquid crystal with positive dielectric anisotropy, an optically active material and a dichroic dye. The working principle is based on the fact that in the area outside the digits critical conditions are established which do not allow the cholesteric structure to form so giving rise to homeotropic structure and therefore a transparent state, while in the digit areas helicoidal structure forms (in off state) and absorbs the ligth.