Liquid crystal display and heater control circuit for use with said display

• US 5,744,819 A
• Filed: 09/16/1992
• Issued: 04/28/1998
• Est. Priority Date: 09/20/1991
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Noda, Shigeru, Yamamoto, Takashi, Takabayashi, Hiroshi, Uehara, Makoto, Yokomizo, Hiroyuki, Iwayama, Mitsuo
• Primary Examiner(s): Thomas, Tom
• Assistant Examiner(s): Abraham, Fetsum
• Application Number:
  US07/945,625
• Time in Patent Office: 2,050 Days
• Field of Search: 359/44, 359/86, 349/58, 349/192, 349/72, 257/72, 257/59
• US Class Current: 257/59
• 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
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals

Abstract

There is disclosed a liquid crystal display comprising a liquid crystal panel having a pair of boards each formed with an electrode and arranged opposedly, and a liquid crystal disposed between said boards, a heater provided near or adjacent said panel, means for detecting the temperature of said panel, and a control circuit for controlling the amount of heat generated by said heater in accordance with a comparison result between an output of said detecting means and a first set temperature for use when said liquid crystal panel is in a service state, or a second set temperature for use when said liquid crystal panel is in a non-service state.

Claims

1. A liquid crystal display comprising:

a liquid crystal panel having a pair of boards, a pair of electrodes, and a liquid crystal disposed between said boards, said panel having a service state in which an image is displayed on said panel and a non-service state in which no image is displayed on said panel;

a heater provided near or adjacent said panel;

means for detecting a temperature of said panel; and

a control circuit for controlling an amount of heat generated by said heater in accordance with a comparison result between an output of said detecting means and either a first set temperature for use when said liquid crystal panel is in said service state, or a second set temperature, lower than said first set temperature, for use when said liquid crystal panel is in said non-service state,

wherein said first set temperature is lower than a minimum temperature necessary for re-aligning said liquid crystal panel.

2. The liquid crystal display according to claim 1, characterized that said liquid crystal is a ferroelectric liquid crystal.

3. The liquid crystal display according to claim 2, characterized that said ferroelectric liquid crystal is a chiral smectic liquid crystal.

4. The liquid crystal display according to claim 1, further comprising selection means for selecting at least one of said first set temperature and said second set temperature.

5. The liquid crystal display according to claim 1, wherein said heater is a substantially planar or planar heater.

6. The liquid crystal display according to claim 1, further comprising setting means for setting said first set temperature and said second set temperature.

7. The liquid crystal display according to claim 1, wherein an upper limit of a temperature adjustment range of said non-service state is lower than a lower limit of a temperature adjustment range that of said service state.

8. A heater control circuit for a liquid crystal display having a panel and a heater for generating heat with a supply of electric power, comprising:

a. a power supply circuit for controlling the electric power to be supplied to the heater;

b. a plurality of temperature decision circuits each for deciding whether a detected temperature of the panel is above a respective predetermined value based on an electric signal obtained by temperature detection means;

c. a clock circuit that indicates time after starting the supply of electric power to the heater; and

d. a control circuit that controls said power supply circuit in response to said temperature decision circuits and said clock circuit,

wherein the panel has a necessary minimum temperature for re-alignment and, when the detected temperature of the panel is not above a set temperature no higher than the necessary temperature within a predetermined time after starting the supply of electric power to the heater, the supply of electric power is compulsorily terminated.

9. The heater control circuit according to claim 8, characterized in that said power supply circuit conducts electricity to the heater, said temperature decision circuits decide when the panel reaches a predetermined temperature, and said control circuit terminates the conduction of electricity to the heater when the predetermined temperature is reached.

10. The heater control circuit according to claim 8, characterized in that a second predetermined time after the panel reaches a predetermined temperature, the supply of electric power to the heater is terminated and the re-alignment is terminated.

11. The heater control circuit according to claim 8, characterized in that the set temperature is equal to the necessary temperature.

12. The heater control circuit according to claim 8, characterized in that when a temperature signal indicated by the temperature detection means falls below a second set temperature set lower than a normal service temperature range, a failure of the temperature detection means is judged and re-alignment is compulsorily terminated.

13. The heater control circuit according to claim 8, wherein said electric power supply circuit is a switch circuit for tuning on/off the electric power.

14. A liquid crystal display comprising:

a. a liquid crystal drive circuit for driving said liquid crystal panel;

b. a heater provided near or adjacent said liquid crystal panel;

c. a first control circuit for controlling the amount of heat generated by said heater by detecting the temperature of said panel;

d. a first power source for supplying the electric power to a liquid crystal drive circuit and said first control circuit;

e. a connector for connecting a second control circuit externally of said liquid crystal display for controlling the amount of heat generated by said heater with an electric power supplied from a second power source different from said first power source by detecting the temperature of said panel.

15. The liquid crystal display according to claim 14, characterized in that said liquid crystal is a ferroelectric liquid crystal.

16. The liquid crystal display according to claim 14, characterized in that said ferroelectric liquid crystal is a chiral smectic liquid crystal.

17. A liquid crystal display characterized by comprising:

a. a liquid crystal panel having a pair of opposed boards each provided with an electrode, and a liquid crystal disposed between said boards;

b. a liquid crystal drive circuit for driving said liquid crystal panel;

c. a heater provided near or adjacent said liquid crystal panel;

d. a first control circuit for controlling the amount of heat generated by said heater by detecting the temperature of said panel;

e. a connector for connecting a second control circuit externally of said liquid crystal display for controlling the amount of heat generated by said heater by detecting the temperature of said panel.

18. The liquid crystal display according to claim 17, characterized in that when said second control circuit is connected to the unit, the power source for said first control circuit and said liquid crystal drive circuit is interrupted.

19. The liquid crystal display according to claim 17, characterized in that the interruption of a power supply to said first control circuit, and the switching of a signal line from said first control circuit to said second control circuit are performed by inserting a circuit board connectable via a connector to said first control circuit into said second control circuit.

20. The liquid crystal display according to claim 17, characterized in that said liquid crystal is a ferroelectric liquid crystal.

21. The liquid crystal display according to claim 17, characterized in that said ferroelectric liquid crystal is a chiral smectic liquid crystal.