Integrated thermally compensated liquid crystal display device

• US 4,029,393 A
• Filed: 04/29/1976
• Issued: 06/14/1977
• Est. Priority Date: 04/29/1976
• 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: Micheli, Adolph L., Dungan, Dennis F.
• Primary Examiner(s): Bauer, Edward S.
• Application Number:
  US05/681,472
• Time in Patent Office: 411 Days
• Field of Search: 350/160 R, 350/160 P, 350/160 LC, 338/22 R, 338/22 SD
• US Class Current: 349/161
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• 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 reflective mode liquid crystal cell having an integral self-actuating heater for maintaining a liquid crystal material in the cell above a temperature at which it solidifies. In this cell, the liquid crystal material is disposed between a transparent member, and a member having a nontransparent barium titanate portion. The barium titanate positive temperature coefficient of electrical resistance has a preselected Curie temperature above the temperature at which the liquid crystal material solidifies. A single power source can be used for electro-optic display, and heat generated by current flow through the barium titanate.

Claims

1. A reflective mode liquid crystal cell having an integral heater that is self-actuating below a predetermined ambient temperature to permit liquid crystal displays at lower ambient temperatures without significantly increasing the complexity of the liquid crystal cell or a system including it, said reflective mode liquid crystal cell comprising:

a first member having a substantially flat surface portion thereon formed of barium titanate having a preselected positive temperature coefficient of electrical resistance;

a reflective electrically conductive coating on said barium titanate flat surface portion serving as one liquid crystal electrode;

a second member adjacent to said first member and having a transparent portion with a substantially flat surface facing said barium titanate surface portion, said transparent portion flat surface and said barium titanate flat surface portion being mutually spaced and substantially parallel;

a conductive transparent coating on said second member transparent portion flat surface serving as a complementary liquid crystal electrode;

a liquid crystal between said first and second members that exhibits an electro-optic effect in response to a voltage applied between said reflective and transparent coatings;

means retaining said liquid crystal between said members; and

at least one additional electrically conductive coating on said barium titanate spaced from said reflective electrode and serving as an additional electrode for maintaining a preselected electrical potential across said barium titanate plate that produces a significant electrical current flow therethrough and an attendant electrical heating therein only at ambient temperatures below a predetermined temperature, whereby said liquid crystal is maintained above said predetermined temperature without external control.

2. A reflective mode liquid crystal cell having an integral heater that is self-actuating below a predetermined ambient temperature to permit liquid crystal displays at lower ambient temperatures without significantly increasing the complexity of the liquid crystal cell or a system including it, said reflective mode liquid crystal cell comprising:

a barium titanate generally plate-like member having a preselected positive temperature coefficient of electrical resistance, said member having a predetermined thickness commensurate with its specific resistivity and rate of change thereof with temperature to present a low electrical resistance below a predetermined temperature and a high electrical resistance above said predetermined temperature;

a reflective electrically conductive coating on one major surface of said barium titanate member serving as a combination heating and electro-optic electrode;

a transparent generally plate-like member spaced adjacent said barium titanate member with its major surfaces generally parallel thereto;

a conductive transparent coating on the major surface of the transparent member facing the barium titanate member and serving as a complementary electrode to said combination electrode;

at least one of said combination and complementary electrodes being appropriately segmented for producing a selected alpha-numeric display;

a dielectric coating completely covering at least one of said combination and complementary electrodes in areas where it could contact a liquid crystal composition, whereby electrical conduction through said liquid crystal is inhibited;

a liquid crystal between said plate-like members and extending from the coating on one member to the coating on the other member;

means retaining said liquid crystal between said plate-like members and in contact with said coatings for producing an electro-optic effect in said liquid crystal; and

an electrode on the opposite major surface of said barium titanate member for maintaining a preselected electrical potential across the thickness of said barium titanate that produces an electrical current flow therethrough and attendant electrical heating therein only at ambient temperatures below said predetermined temperature, whereby said liquid crystal between said plate-like members is maintained above said predetermined temperature without external control.

3. A reflective mode liquid crystal cell having an integral heater that is self-actuating below a predetermined ambient temperature to permit liquid crystal displays at lower ambient temperatures without significantly increasing the complexity of the liquid crystal cell or a system including it, said reflective mode liquid crystal cell comprising:

a barium titanate generally plate-like member having a preselected positive temperature coefficient of electrical resistance, said member having a predetermined thickness less than about 0.2 cm that is commensurate with its specific resistivity and rate of change thereof with temperature, so as to present electrical resistance of the order of 5 ohms and significant electrical heating therein below a predetermined temperature and an electrical resistance above said predetermined temperature that restricts electrical heating therein;

a reflective electrically conductive coating about 1000-3000 angstroms thick on one major surface of said barium titanate member serving as a combination heating and electro-optic electrode;

a transparent generally plate-like member with one major surface spaced about 10-10,000 microns away from said barium titanate member and generally parallel thereto;

a conductive transparent coating about 1000-3000 angstroms thick on the major surface of the transparent member facing the barium titanate member and serving as a complementary electrode to said combination electrode;

at least one of said combination and complementary electrodes being appropriately segmented for producing a selected alpha-numeric display;

a dielectric coating about 1000-3000 angstroms thick covering at least one of said combination and complementary electrodes in areas where it could contact a liquid crystal composition, whereby electrical conduction through said liquid crystal is inhibited;

a liquid crystal between said plate-like members and extending from the coating on one member to the coating on the other member,

means retaining said liquid crystal between said plate-like members and in contact with said coatings for producing an electro-optic effect in said liquid crystal;

an electrode on the opposite major surface of said barium titanate member for maintaining a preselected electrical potential across the thickness of said barium titanate that produces an electrical current flow therethrough and attendant electrical heating therein only at ambient temperatures below said predetermined temperature, whereby said liquid crystal between said plate-like members is maintained above said predetermined temperature without external control; and

means for applying a voltage of one polarity to said combination electrode while simultaneously applying a voltage of opposite polarity to both of said complementary electrode and said opposite surface barium titanate electrode.