Reflective liquid-crystal television display

Abstract

A new reflective television display, operating off the air, is described. The display uses the dynamic scattering mode (DSM) in nematic liquid crystals and can be viewed in high-brightness ambients. The liquid crystal cell, 6 to 12 µm thick, was addressed in real time by means of an electron beam using a wire-mosaic faceplate on a demountable cathode ray tube. Two different liquid crystal materials--anasylidene paraamino phenyl acetate (APAPA) and an RCA proprietary room temperature liquid crystal--were tested with similar results except for the difference in operating temperature (82 to 110° C and room temperature, respectively). The resolution of the 3.1-cm-square display was somewhat less than that required for commercial television (∼150 lines), limited by the mosaic structure but not the liquid crystal. Adequate resolution should be achievable in slightly larger displays. The contrast was not optimized (7.5 to 1) but several techniques are available to improve this value to 15 or 20 to 1 as has been demonstrated in static displays. The subjective evaluation of this display points out the attractiveness of reflective television panels; under suitable external illumination the panel has a wide viewing angle (±45° approximately). The current and voltage requirements to achieve the DSM in liquid crystals are such as to raise hopes that an integrated addressing approach suitable for flat television panels can be found.