Symmetrical internal heater for liquid crystal display

• US 4,093,355 A
• Filed: 02/04/1977
• Issued: 06/06/1978
• Est. Priority Date: 02/04/1977
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Kaplit, Michael, Smith, George W., Hayden, Daniel B.
• Primary Examiner(s): Bauer, Edward S.
• Application Number:
  US05/765,548
• Time in Patent Office: 487 Days
• Field of Search: 350/160 R, 350/160 P, 350/160 LC, 219/209, 219/214
• US Class Current: 349/161
• CPC Class Codes: G02F 1/133382 Heating or cooling of liquid crystal cells other than for activation, e.g. circuits or arrangements for temperature control, stabilisation or uniform distribution over the cell

Abstract

A liquid crystal cell having an internal resistance-type heating means for rapid cell warm-up, and for maintaining the cell at a predetermined temperature while it is operating as a visual display. The heating means comprises electrically symmetrical transparent films of resistance material on facing surfaces of transparent members sandwiching the liquid crystal material. The resistive films are covered with an insulating film, on which is disposed the control electrodes for the electro-optic display of the liquid crystal cell. Heating voltages, higher than those required to operate the visual display, can be safely applied in parallel across the films without interfering with a concurrent visual display.

Claims

1. A liquid crystal cell having a resistive-type internal heater for rapid warm-up of the liquid crystal cell and for use while the cell is functioning as an electro-optic visual display, said cell comprising:

first and second members having spaced apart facing surfaces in a visual display area, at least one of said members being transparent in said display area;

a liquid crystal between said facing surfaces for exhibiting an electro-optic efffect;

a transparent coating of resistive material on each of said facing surfaces for heating said liquid crystal material from two heat sources simultaneously, each coating being electrically symmetrical with the other for so heating said liquid crystal material without adversely affecting an electro-optic effect concurrently produced therein;

a transparent dielectric coating on each of said resistive material coatings; and

a transparent electrode on each of said dielectric coatings for producing an electro-optic effect in said liquid crystal material.

2. A liquid crystal cell having a resistance-type internal heater for rapid warm-up of the liquid crystal cell and for use while the cell is functioning as an electro-optic visual display, said cell comprising:

first and second members having spaced apart facing surfaces in a visual display area, at least one of said members being transparent in said display area;

a liquid crystal material between said facing surfaces for exhibiting an electro-optic effect upon application of a threshold voltage;

a transparent coating of resistive material on each of said facing surfaces to which a voltage can be respectively applied for heating said liquid crystal material at both of said facing surfaces, each coating being mutually electrically symmetrical with the other so that a heating voltage higher than said threshold voltage can be respectively symmetrically applied to said coatings without producing a significant electrical field component therebetween;

a transparent dielectric coating on each of said resistive material coatings; and

a transparent electrode on each of said dielectric coatings for producing an electro-optic effect in said liquid crystal material.

3. A liquid crystal cell having a resistance-type internal heater for rapid warm-up of the liquid crystal cell and for use while the cell is functioning as an electro-optic visual display, said cell comprising:

first and second members having spaced apart facing surfaces providing a visual display area, at least one of said first members being transparent in said display area;

a liquid crystal material between said facing surfaces for exhibiting an electro-optic effect upon application of a threshold voltage;

a transparent continuous coating of resistive material on each of said facing surfaces to which a voltage can be respectively applied for heating said liquid crystal material at both of said facing surfaces, each coating being of substantially the same composition and thickness as the other and having a periphery substantially symmetrical and in register with the other, whereby a symmetrically applied heating voltage greater than said threshold voltage can be applied to said coatings without also inherently producing a significant voltage differential therebetween;

a transparent dielectric coating on each of said resistive material coatings; and

a transparent display electrode on each of said dielectric coatings for producing an electro-optic effect in said liquid crystal material.

4. A liquid crystal cell having a resistance-type internal heater for rapid warm-up of the cell and for use while the cell is functioning as an electro-optic visual display, said cell comprising:

first and second transparent members having spaced apart facing surfaces providing a visual display area;

a liquid crystal material between said facing surfaces for exhibiting an electro-optic effect upon application of a threshold voltage;

a transparent continuous coating of resistive material on each of said facing surfaces to which a voltage can be respectively applied for heating said liquid crystal material at both of said facing surfaces, each coating covering substantially the entire display area and having a periphery substantially coextensive with the other, each coating further having substantially the same composition and thickness as the other and symmetrical electrical contact areas;

means electrically parallelling said symmetrical contact areas for symmetrically applying a heating voltage to each of said respective material coatings that is substantially greater than said threshold voltage without producing a significant voltage differential at any point therebetween;

a first transparent dielectric coating on each of said resistive material coatings; and

a transparent electrode on each dielectric coating for producing an electro-optic effect in said liquid crystal material.

5. In an electro-optic liquid crystal display apparatus having a visual display cell formed of two electro-optic members with a liquid crystal material in a display area therebetween, the improvement which includes:

transparent coatings of resistance material supported on facing surface portions of said members for heating said liquid crystal material from two opposite faces, the coatings being mutually electrically symmetrical for heating said liquid crystal material from said opposite faces without adversely affecting an electro-optic effect concurrently produced therein; and

means in parallel with said coatings for applying a heating voltage across each of said coatings in excess of an electro-optic visual display threshold voltage for said cell.

6. In an electro-optic liquid crystal display apparatus having a visual display cell formed of two transparent electro-optic members with liquid crystal material in a display area therebetween, the improvement which includes:

transparent continuous coatings of a resistive material on facing surface portions of said cell members for heating said liquid crystal material from two opposite faces, said coatings covering substantially the entire display areas of said members and having substantially registered peripheries and contact areas, said coatings further having the same composition and thickness;

means for electrically parallelling said registered contact areas on said coatings; and

means for applying a heating current through said electrically parallelled coatings under a voltage in excess of an electro-optic visual display threshold voltage for said cell.