Liquid crystal apparatus that changes a voltage level of a correction pulse based on a detected temperature

• US 5,903,251 A
• Filed: 01/27/1997
• Issued: 05/11/1999
• Est. Priority Date: 01/29/1996
• Status: Expired due to Fees

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Ohno, Tomoyuki, Mori, Hideo
• Primary Examiner(s): BRIER, JEFFERY A
• Application Number:
  US08/790,738
• Time in Patent Office: 834 Days
• Field of Search: 345/101, 345/94-97, 349/72
• US Class Current: 345/101
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A liquid crystal apparatus includes a liquid crystal device formed by a pair of substrates having thereon a group of scanning electrodes and a group of data electrodes intersecting the scanning electrodes so as to form an electrode matrix, and a liquid crystal disposed between the substrates so as to form a pixel at each intersection of the scanning electrodes and the data electrodes; and temperature-detection means for detecting a temperature of the liquid crystal device. The liquid crystal device is driven by applying a scanning signal comprising a clear pulse, a write pulse and a correction pulse to the scanning electrodes and for applying data signals to the data electrodes in synchronism with the scanning signal, while changing a voltage level of the correction pulse based on temperature data from the temperature-detection means. As a result, the liquid crystal device can effect a stable display over the entire area even if it has a temperature distribution therealong.

Claims

1. A liquid crystal apparatus, comprising:

a liquid crystal device comprising a pair of substrates having thereon a group of scanning electrodes and a group of data electrodes intersecting the scanning electrodes so as to form an electrode matrix, and a liquid crystal disposed between the substrates so as to form a pixel at each intersection of the scanning electrodes and the data electrodes,

temperature-detection means for detecting a temperature of the liquid crystal device,

drive means for applying a scanning signal comprising a clear pulse, a write pulse and a correction pulse to the scanning electrodes and for applying data signals to the data electrodes in synchronism with the scanning signal, and

voltage control means for changing a voltage level of the correction pulse based on temperature data from the temperature-detection means,

wherein the voltage control means changes the voltage level of the correction pulse based on a table showing a relationship between the detected temperature and a temperature distribution of the liquid crystal device.

2. An apparatus according to claim 1, wherein the voltage control means sets a smaller voltage amplitude of the correction pulse when the detected temperature is lower and a larger voltage amplitude when the detected temperature is higher.

3. An apparatus according to claim 1 or 2, wherein the voltage control means further changes the voltage level of the write pulse of the scanning signal based on the temperature data.

4. An apparatus according to claim 1 or 2, wherein the voltage control means further changes at least one of a pulse width of the write pulse and a pulse width of the correction pulse.

5. An apparatus according to claim 1 or 2, including a plurality of the temperature detection means disposed at different positions along the liquid crystal device.

6. An apparatus according to claim 1 or 2, wherein said liquid crystal is a chiral smectic liquid crystal.

7. An apparatus according to claim 1 or 2, wherein said liquid crystal is a ferroelectric liquid crystal.

8. An apparatus according to claim 1, wherein, at a lower temperature, the write pulse is set to have a larger voltage amplitude and the correction pulse is set to have a smaller voltage amplitude;

and, at a higher temperature, the write pulse is set to have a smaller voltage amplitude and the correction pulse is set to have a larger voltage amplitude.

9. An apparatus according to claim 1, wherein, at a lower temperature, the write pulse and the correction pulse are respectively set to have a larger pulse width and the correction pulse is set to have a smaller voltage amplitude;

and, at a higher temperature, the write pulse and the correction pulse are respectively set to have a smaller pulse width and the correction pulse is set to have a larger voltage amplitude.

10. An apparatus according to any of claims 1, 2 and 8-9, wherein the correction pulse is caused to have voltage levels independently set for at least two scanning electrodes depending on temperatures.

11. An apparatus according to any of claims 1, 2 and 8-9, wherein the clear pulse and the correction pulse have one polarity, and the write pulse has the other polarity, respectively with respect to a prescribed potential.

12. A driving method for a liquid crystal device of the type comprising a pair of substrates having thereon a group of scanning electrodes and a group of data electrodes intersecting the scanning electrodes so as to form an electrode matrix, and a liquid crystal disposed between the substrates so as to form a pixel at each intersection of the scanning electrodes and the data electrodes;

said driving method comprising;

detecting a temperature of the liquid crystal device by temperature detection means,

sequentially applying a scanning signal comprising a clear pulse, a write pulse and a correction pulse to the scanning electrodes and applying data signals to the data electrodes in synchronism with the scanning signal, and

changing a voltage level of the correction pulse based on temperature data from the temperature detection means,

wherein the voltage level of the correction pulse is changed based on a table showing a relationship between the detected temperature and a temperature distribution of the liquid crystal device.

13. A method according to claim 12, wherein the correction pulse is set to have a smaller voltage amplitude when the detected temperature is lower and a larger voltage amplitude when the detected temperature is higher.