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Fluorocarbon Surface Aligning Agents for Nematic Liquids

IP.com Disclosure Number: IPCOM000080872D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 22K

Publishing Venue

IBM

Related People

Bush, RF: AUTHOR [+3]

Abstract

In the use of nematic liquids in electro-optic display devices and other applications, it is necessary that the optic axis of the liquid lie in a predetermined direction uniformly over the entire sample. To obtain a homeotropic alignment, i.e., wherein the optic axis is perpendicular to the enclosing surface, heretofore, there have been employed such techniques as the addition of quaternary ammonium salts to the liquids, or the treatment of the surfaces with silanes or lipids. The feature common to these techniques is the providing of an interfacial layer with the liquid crystal being adjacent to hydrocarbon chains. Methods are also known for aligning liquid crystals with the optic axis lying parallel to the plane of the surface.

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Fluorocarbon Surface Aligning Agents for Nematic Liquids

In the use of nematic liquids in electro-optic display devices and other applications, it is necessary that the optic axis of the liquid lie in a predetermined direction uniformly over the entire sample. To obtain a homeotropic alignment,
i.e., wherein the optic axis is perpendicular to the enclosing surface, heretofore, there have been employed such techniques as the addition of quaternary ammonium salts to the liquids, or the treatment of the surfaces with silanes or lipids. The feature common to these techniques is the providing of an interfacial layer with the liquid crystal being adjacent to hydrocarbon chains. Methods are also known for aligning liquid crystals with the optic axis lying parallel to the plane of the surface.

While the above-cited techniques are generally applicable to certain types of nemetic liquid materials, it has been found that the important classes of nematic liquids such as chlorostilbenes and diesters are found to resist alignment by such methods.

It has been discovered in accordance with the technique described herein that when indium oxide glass plates, which are the commonly used transparent electrodes in display devices, are treated with a solution of perfluorooctanoic acid, nematic liquid assumes a homeotropic alignment upon enclosure by a pair of these plates. With such treatment, there has been achieved homeotropy with chlorostilbenes and diesters.

It has also been discovered in accordance with the technique that in-plane alignment of high quality is obtained with liquid crystals, if a microscopic interfacial layer of polytetrafluoroethylene (TEFLON* TFE) is provided on the solid substrate prior to the usual rubbing procedure. Such a layer is provided by transfer due to sliding contact of the substrate with bulk polytetrafluoroethylene, as described by Makinson and Tabor, Proc. Roy. Soc. 281A, 49 (1964). An alternative method of transfer consists of spraying with "FLUORO-GLIDE**, Chemically Pure Grade" and wiping the discrete, micron fine particles off with a clean cloth. In the case of t...