Liquid-crystal mixtures for use in liquid-crystal displays

Abstract

Abstract Mixtures of nematic-phase liquid-crystal materials that contain a sufficient amount of p-cyanobenzal-p'-n-butylaniline or the like, possibly together with other materials, will exhibit the nematic phase at about room temperature and over a considerable temperature range above and below, and at the same time, a positive dielectric anisotropy. This enables the production of a liquid-crystal unit comprising first and second pieces of flat glass, each coated on one side with a transparent electroconductive oxide coating and each having its so-coated surface rubbed with cotton cloth or the like in one direction, with the two surfaces so rubbed then being spaced about 1/4 to 2 mils apart and with the above-mentioned nematic-phase liquid-crystal material in between, and with the directions of rubbing being oriented substantially perpendicular to each other. Such a liquid-crystal unit has the particular property that when there is no potential applied to the electroconductive coatings and the unit is placed between crossed polarizers, light is transmitted, but the application of but a relatively low voltage across the two above-mentioned coatings, something on the order of 5 volts, will generate an electric field that causes the nematic-phase liquid-crystal material to "untwist," so that it no longer permits transmission of light through the structure comprising the liquid-crystal unit and the crossed polarizers. The effect is quick-acting and reversible. Conversely, with parallel polarizers stationed to each side of such a unit, the effect is the opposite; with no voltage applied, no light is transmitted through the structure, but the application of sufficient voltage makes light transmission possible.

Inventors

• 👤 James L. Fergason

Bibliographic Details