GB1435591A - Liquid crystal devices - Google Patents

Abstract

1435591 Modulating light WESTERN ELECTRIC CO Inc 22 June 1973 [23 June 1972 (2)] 29766/73 Heading H4F The molecules of one side of a liquid crystal layer are given a tendency to align in a single predetermined direction by the layer being in contact with a surface of non-liquid crystalline material containing a plurality of substantially parallel linear elevational variations of between 5 Š and 10<SP>4</SP> Š, spaeed by from 1 x 10<SP>4</SP> to 2 Î 10<SP>4</SP> Š. A device incorporating such an arrangement may be a light modulator, in which the alignment in the predetermined direction may occur either before or after the application of a suitable constraint, e.g. a magnetic or electric field, or a mechanical or thermal signal, or it may be a passive optical polarizer wherein alignment necessarily occurs as a result of the elevational variations. Such a device often has a second aligning surface in contact with the other side of the liquid crystal layer, the alignment direction not necessarily being parallel. In the case of the passive polarizer the liquid crystal material preferably contains a dichroic dye to increase the polarizing effect. Surfactants may be used either to aid the alignment of the liquid crystal material in the predetermined direction, or, in the case of a modulator wherein alignment occurs after energization, to produce a different alignment before energization. For example a nematic phase may be homotropically aligned per se and align parallel to the surface and to the elevational variations when an electric field is applied. The non-liquid crystalline surface may be partially covered by the elevational variations for a localized effect, and/or different areas of the surface may contain pluralities of elevational variations which extend in different respective directions. The elevational variations may be produced by mechanical scoring, casting, etching, photolithography, ion bombardment or melting, vapour or liquid deposition, or by laser interference techniques, inter alia. The surface thus treated, e.g. if a substrate or an electrode and/or dielectric layer or a photo-resist over the substrate, may be the surface contacting the liquid crystal layer, or alternatively a treated substrate may underlie a thin film electrode and/or dielectric layer which contacts the liquid crystal layer and conforms to the elevational variations in the substrate surface. Many known types of liquid crystal light modulators are referred to, e.g. dynamic scattering, the fast turn-off mode, those with memory scattering effects or showing a change of state or phase, those including additives such as dichroic dyes, and those having a twisted nematic structure. They may be reflective or transmissive, and may include integral plane polarizers.