Liquid crystal apparatus with temperature compensation control circuit

• US 5,033,822 A
• Filed: 08/10/1989
• Issued: 07/23/1991
• Est. Priority Date: 08/17/1988
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tsuboyama, Akira, Inoue, Hiroshi, Ooki, Akiko
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Trice, Ron
• Application Number:
  US07/392,010
• Time in Patent Office: 712 Days
• Field of Search: 350/332, 350/331 T, 350/331 R, 350/350 S, 350/333, 340/784
• US Class Current: 345/101
• 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: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/36 using liquid crystals

Abstract

A liquid crystal apparatus is provided a liquid crystal display comprising scanning electrodes, data electrodes disposed opposite to and intersecting with the scanning electrodes so as to form an electrode matrix, and a ferroelectric liquid crystal disposed between the scanning electrodes and data electrodes. A first circuit is further provided for applying a scanning selection signal having a duration of one scanning selection period 1H to the scanning electrodes and applying data signals to the data electrodes in synchronism with the scanning selection signal so as to apply a drive voltage having an amplitude V_OP to the liquid crystal. A control circuit controls the first circuit so as to change the one scanning selection period 1H by a change Δ1H and the drive voltage amplitude V_OP by a change ΔV_OP corresponding to a change in ambient temperature, the changes Δ1H and ΔV_OP satisfying the following formula (1):

-0.8≧Δlog 1H/Δlog V.sub.OP ≧-1.4 (1),

wherein Δlog 1H¹ =log(1H₁ +Δ1H)-log 1H, and Δlog V_OP =log(V_OP1 +ΔV_OP)-log V_OP1, 1H₁ being one scanning selection period before the change, V_OP1 being the drive voltage amplitude before the change.

Claims

1. A liquid crystal apparatus, comprising:

(a) a liquid crystal device comprising scanning electrodes, data electrodes disposed opposite to and intersecting with said scanning electrodes so as to form an electrode matrix, and a ferroelectric liquid crystal disposed between said scanning electrodes and data electrodes;

(b) first means for applying a scanning selection signal having a duration of one scanning selection period 1H to said scanning electrodes and applying data signals to said data electrodes in synchronism with the scanning selection signal so as to apply a drive voltage having an amplitude V_OP to said liquid crystal; and

(c) control means for controlling said first means so as to change the one scanning selection period 1H by a change Δ

1H and the drive voltage amplitude V_OP by a change Δ

V_OP corresponding to a change in ambient temperature, the changes Δ

1H and Δ

V_OP satisfying the following formula (1);

space="preserve" listing-type="equation">-0.8≧

Δ

log 1H/Δ

log V.sub.OP ≧

-1.4 (1),

wherein Δ

log 1H =log (1H₁ +Δ

1H)-log 1H₁, and Δ

log V_OP =log(V_OP1 +Δ

V_OP)-log V_OP1, 1H₁ being one scanning selection period before the change, V_OP1 being the drive voltage amplitude before the change.

2. An apparatus according to claim 1, wherein said control means includes means for re-setting the changed drive voltage amplitude caused by the change in temperature to the drive voltage amplitude before the change thereof due to the change in temperature after a prescribed number of vertical scanning operations.

3. An apparatus according to claim 1, wherein the magnitude of the change Δ

1H caused by a temperature change is preliminarily set for each prescribed temperature-changing point.

4. An apparatus according to claim 1, wherein the magnitude of the change Δ

V_OP caused by a temperature change is preliminarily set for each prescribed temperature-changing point.

5. A liquid crystal apparatus, comprising:

(a) a liquid crystal device comprising X scanning electrodes, Y data electrodes disposed intersecting said scanning electrodes to form an X-Y electrode matrix, and a ferroelectric liquid crystal disposed between said scanning electrodes and data electrodes, X and Y being positive integers;

(b) scanning electrode drive means for applying a scanning selection signal having a duration of one scanning selection period 1H to said scanning electrodes N electrodes apart(N;

a positive integer) in one vertical scanning and applying the scanning selection signal to said X scanning electrodes in N+1 times of vertical scanning;

(c) data electrode drive means for applying data signals to said data electrodes in parallel and in synchronism with the scanning selection signal so as to apply a drive voltage having an amplitude V_OP to said liquid crystal; and

(d) control means for controlling said scanning electrode drive means and data electrode drive means so as to change the one scanning selection period 1H by a change Δ

1H and the drive voltage amplitude V_OP by a change Δ

V_OP corresponding to a change in ambient temperature, the changes Δ

1H and Δ

V_OP satisfying the following formula (1);

7. An apparatus according to claim 5, wherein said control means includes means for re-setting the changed drive voltage amplitude caused by the change in temperature to the drive voltage amplitude before the change thereof due to the change in temperature after a prescribed number of vertical scanning operations.

8. An apparatus according to claim 5, wherein the magnitude of the change Δ

1H caused by a temperature change is preliminarily set for each prescribed temperature-changing point.

9. An apparatus according to claim 5, wherein the magnitude of the change Δ

V_OP caused by a temperature change is preliminarily set for each prescribed temperature-changing point.

12. An apparatus according to claim 9, wherein said control means includes means for re-setting the changed drive voltage amplitude caused by the change in temperature to the drive voltage amplitude before the change thereof due to the change in temperature after a prescribed number of vertical scanning operations.

13. An apparatus according to claim 9, wherein the magnitude of the change Δ

1H caused by a temperature change is preliminarily set for each prescribed temperature-changing point.

14. An apparatus according to claim 9, wherein the magnitude of the change Δ

V_OP caused by a temperature change is preliminarily set for each prescribed temperature-changing point.

6. -0. 8≧

Δ

log 1H/Δ

log V_OP ≧

-1.4 (1),

wherein Δ

log 1H=log (1H₁ +Δ

1H)-log 1H₁, and Δ

log V_OP =log(V_OP1 +Δ

V_OP)-log V_OP1, 1H₁ being one scanning selection period before the change, V_OP1 being the drive voltage amplitude before the change.

10. A liquid crystal apparatus, comprising:

(a) a liquid crystal device comprising scanning electrodes, data electrodes disposed intersecting said scanning electrodes to form an electrode matrix, and a ferroelectric liquid crystal disposed between said scanning electrodes and data electrodes;

(b) scanning electrode drive means for applying to a selected scanning electrode a scanning selection signal having a duration of one scanning selection period 1H and comprising a first voltage of one polarity and a second voltage of the other polarity with reference to the voltage level of a non-selected scanning electrode;

(c) data electrode drive means for applying, to a selected data electrode, a first voltage signal providing a first drive voltage causing one orientation state of the ferroelectric liquid crystal in combination with said voltage of one polarity and a second voltage signal providing a second drive voltage causing the other orientation state of the ferroelectric liquid crystal in combination with said voltage of the other polarity, and to a non-selected data electrode, a third voltage signal providing a third voltage causing the one orientation state of the ferroelectric liquid crystal in combination with said voltage of one polarity and a fourth voltage signal providing a fourth voltage not changing the orientation state of the ferroelectric liquid crystal; and

(d) control means for controlling said scanning electrode drive means and data electrode drive means so as to change the one scanning selection period 1H by a change Δ

1H and the first, second and third drive voltages by an amplitude change Δ

V_OP corresponding to a change in ambient temperature satisfying the following formula (1);

11. -0. 8≧

Δ

log 1H/Δ

log V_OP ≧

-1.4 (1),

wherein Δ

log 1H=log (1H₁ +Δ

1H)-log 1H₁, and Δ

log V_OP =log(V_OP1 +Δ

V_OP)-log V_OP1, 1H₁ being one scanning selection period before the change, V_OP1 being the drive voltage amplitude before the change.