Liquid crystal flat display

Abstract

We present here a new principle of flat panel using a smectic A liquid crystal. It is a "passive" matrix working in a thermoelectric mode : at rest, the liquid crystal is transparent while is strongly scatters the light when it is heated by mean of one set of electrodes ; but if an electric field is applied on the liquid crystal, the intensity of the scattered light, decreases. We showed on a prototype that the addressing time of a line can be 60/us or less ; the relaxation times of the liquid crystal for both transitions transparent → scattering and the reverse is less than 2ms. So the frame change time can be adjust from 30ms to several seconds depending on the application. This smectic A matrix display which is simple to realize -as the "passive" matrices- presents characteristics for the contrast ratio, the resolution and the response times which, were only obtained with active matrices.