Guest-host liquid crystal display device

Claim 1

In a liquid crystal display device having a pair of transparent plates each formed with a transparent electrode and a liquid crystal layer interposed therebetween, in which an electric field is applied to the transparent electrodes to control the transmission of unpolarized light through the liquid crystal layer, the improvement wherein: said liquid crystal layer comprises a pleochroic liquid crystal mixture composed of a guest pleochroic material and a host liquid crystal material, said liquid crystal layer having helical molecular ordering in the absence of said electric field and homeotropic molecular ordering in the presence of said electric field; the molecular axis of said pleochroic liquid crystal mixture is inclined at an angle of between 10 and 80 degrees with respect to the normal to said transparent plates; and the orientation of the liquid crystal molecules at the surface of one of said pair of transparent plates crosses the orientation of the liquid crystal molecules at the surface of the other of said pair of transparent plates at an angle Δφ which satisfies the following relation 2π(d/Po-m+1/4)<Δφ<2π(d/Po-m+3/4) where d is the thickness of said liquid crystal layer, Po is the inherent helical pitch of said pleochroic liquid crystal mixture, and m is the maximum integer which does not exceed d/Po.