Browse Prior Art Database

Liquid Crystal Display Device

IP.com Disclosure Number: IPCOM000074844D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Bush, RF: AUTHOR [+2]

Abstract

A voltage activated display is shown, wherein light present in a thin plate is coupled into a liquid crystal medium and then to an observer. Changing the voltage on the display cuts off the light by altering the index of refraction of the liquid crystal sufficiently so that total internal reflection occurs at the plate-liquid crystal interface.

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Liquid Crystal Display Device

A voltage activated display is shown, wherein light present in a thin plate is coupled into a liquid crystal medium and then to an observer. Changing the voltage on the display cuts off the light by altering the index of refraction of the liquid crystal sufficiently so that total internal reflection occurs at the plate-liquid crystal interface.

The display unit comprises a light pipe 1 through which a light source is transmitted. A liquid crystal 2 is disposed on the surface of light pipe 1. A glass plate 3 having an index of refraction which is between the indices of refraction of liquid crystal 2, is situated on liquid crystal 2. Transparent addressing electrodes 4 are placed on the surfaces of plates 1 and 3 adjacent to the liquid crystal in the usual crossed-grid geometry.

With no voltage applied (on state) the ratio of the glass to liquid crystal indices of refraction is such as to permit light to pass from light pipe 1 to the liquid and on through to the observer. With a voltage applied (off state) the dielectric constant is decreased to a valve such that the light in the light pipe is cut off from the liquid crystal by total internal reflection, so that the display is now dark. This mode of operation assumes the usual alignment of the liquid molecules parallel to the glass plates. For homeotropic alignment the states designated on and off are reversed from the above. A diffuser, not shown, can also be added to avoid highly dir...