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Liquid Crystal Polychromatic Display Device

IP.com Disclosure Number: IPCOM000077442D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Freiser, MJ: AUTHOR

Abstract

It is known that nematic liquids are optically anisotropic, uniaxial liquids. In addition, they are known to be highly birefringent having typically delta n = n(e) - n(o) = 0.25 wherein n is index of refraction, and thin films thereof can be oriented with the employment of surface forces.

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Liquid Crystal Polychromatic Display Device

It is known that nematic liquids are optically anisotropic, uniaxial liquids. In addition, they are known to be highly birefringent having typically delta n = n(e) - n(o) = 0.25 wherein n is index of refraction, and thin films thereof can be oriented with the employment of surface forces.

In this device there is considered the orientation of a thin film of a nematic liquid disposed between two tin oxide coated glass plates, such that the optic axis of the liquid lies in the plane of the film. Since the DC dielectric susceptibility of nematic liquids is anisotropic and the anisotropy can be of either sign for different nematic liquid materials, the optic axis can be oriented either parallel or perpendicular to an applied electric field. In this device, there is considered a nematic liquid material whose optic axis can be oriented parallel to the applied electric field. It is assumed that the liquid is highly purified, whereby there is avoided any disorienting effects which could result from current flow.

In a sandwich cell made up of molecules of a liquid having the parallel orientation as described hereinabove, a threshold voltage exists above which the orientation of the liquid begins to tilt toward the perpendicular to the plane of the electrodes. This critical voltage is V(c) = 2 pi/3/2/(K/delta epsilon)/1/2/ wherein K is an elastic constant of the nematic liquid (typically 10/-6/ dyne) and delta epsilon is the anisotropy of the dielectric constant (of the order of unity). Thus V(c) = 10/-2/ statvolts = 3 volts. As the applied voltage is increased, the index of refraction in the midplane of the liquid for light polarized parallel to the orientation of the quiescent nematic liquid changes from n(e) to n(o). Upon removal of the voltage, the liquid will return to the alignment of the quiescent state as dictated by the surface forces.

Figs. 1-3 show the liquid crystal at three different applied fields, respectively. Thus in Fig. 1 where the applied voltage V=0, the orientation of the molecules is parallel to the plane of the transparent electrode delta n = delta n(max) = 0.25. In Fig. 3 wherein the V is relatively large, i.e., about 10 V(c) wherein V(c) is the init...