Roughening surfaces for homeotropic layers of smectic LCD's

• US 4,411,494 A
• Filed: 11/21/1980
• Issued: 10/25/1983
• Est. Priority Date: 01/18/1978
• Status: Expired due to Term

• Current Assignee: STC PLC (f/k/a Standard Telephones and Cables)
• Original Assignee: International Standard Electric Corporation (ITT, Inc.)
• Inventors: Coates, David, Crossland, William A.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Lewis, David
• Application Number:
  US06/209,235
• Time in Patent Office: 1,068 Days
• Field of Search: 350/340, 350/341, 350/350 S
• US Class Current: 349/138
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers

Abstract

An internally electroded smectic liquid crystal display cell having a layer of a smectic material sandwiched between two electroded plates having electrodes that overlap at least in part wherein each said electrode is covered with an electrically insulating coherent layer whose surface has been treated to provide it with a rough texture provides a liquid crystal display cell of low voltage threshold characteristics.

Claims

1. A liquid crystal display comprising:

a pair of spaced opposed glass plates each having an inward facing surface;

a pair of opposed transparent electrodes each supported by a different one of said inward facing surfaces;

liquid crystal material in homeotropic alignment sandwiched between said electrodes; and

a layer of transparent electrically insulating coherent silica deposited on each of said electrodes, each of said layers having an etch roughened surface comprising a plurality of peaks in the range of about 50-190 peaks of 20 A or greater per mm length across an associated one of said electrodes to provide a rough surface for said associated one of said electrodes adjacent said material so that said display has a low switching voltage threshold.

2. A method of forming a smectic cell having a low switching voltage threshold comprising the steps of:

providing two spaced, parallel glass plates each having an inwardly facing surface;

disposing a transparent electrode on each of said inwardly facing surfaces;

depositing by a chemical vapor reaction a transparent layer of silica on each of said electrodes;

etching each of said layers for a predetermined period of time to provide a roughened inwardly facing surface of a predetermined roughness for each of said electrodes so that said display has said low switching voltage threshold;

assembling said plates to define a cell;

filling said cell with a smectic material;

and

sealing said cell.