FIELD-INDUCED COLOR SWITCHING IN LIQUID-CRYSTAL DISPLAYS

A new electro-optical guest-host effect is described which changes its color upon the application of a voltage. It is shown that the color change depends on the voltage-induced change of the polarized absorption of dichroic dyes (guests) whose transition moments are primarily parallel (longitudinal) and perpendicular (transverse) to their respective molecular axis. The new effect does not require polarizers and can be operated at low voltages like twisted nematic displays. Its excellent brightness and contrast are much less dependent on large order parameters as compared with other guest-host effects. Analytical expressions describing the dependence of the transmission and color of the effect on dye order parameter and direction of transition moment, elastic and dielectric properties of the liquid crystal (host) matrix, viewing angle and display voltage are derived and compared with experimental results. © 1979 American Institute of Physics.