Driving method for liquid crystal device and liquid crystal apparatus

• US 6,452,581 B1
• Filed: 04/10/1998
• Issued: 09/17/2002
• Est. Priority Date: 04/11/1997
• Status: Expired due to Fees

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Tsuboyama, Akira, Okada, Shinjiro, Iba, Jun, Katakura, Kazunori
• Primary Examiner(s): Saras, Steven
• Assistant Examiner(s): Spencer, William C.
• Application Number:
  US09/058,205
• Time in Patent Office: 1,621 Days
• Field of Search: 345/204, 345/97, 345/101
• US Class Current: 345/101
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• 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 device of the type comprising a pair of substrates and a chiral smectic liquid crystal disposed between the substrates so as to form at least one pixel, is driven by a driving method including applying a signal waveform to a selected pixel. The driving method includes the step of applying the signal waveform which includes a clear pulse for placing the liquid crystal in a first state and a writing pulse subsequent to the clear pulse for selectively placing the liquid crystal in a second state depending on input data. The writing pulse includes a higher voltage portion and a pair of lower voltage portions sandwiching the higher voltage portion. The writing pulse is effective in reducing power consumption while ensuring a wider drive margin.

Claims

1. A driving method for a liquid crystal device of the type comprising a pair of substrates and a chiral smectic liquid crystal disposed between the substrates so as to form at least one pixel, said driving method comprising:

detecting a temperature of the liquid crystal device by temperature detection means to determine whether the temperature is in a higher temperature range or a lower temperature range, and

selectively applying a higher temperature-signal waveform to one selected pixel when the detected temperature is in the higher temperature range and applying a lower temperature-signal waveform different from the higher temperature-signal waveform to said one selected pixel when the detected temperature is in the lower temperature range,

wherein the higher temperature-signal waveform comprises a clear pulse for placing the liquid crystal in a first state and a writing pulse subseqent to the clear pulse for selectively placing the liquid crystal in a second state depending on input data, and

said writing pulse comprises a higher voltage portion and a pair of lower voltage portions sandwiching the higher voltage portion.

2. A driving method according to claim 1, wherein the higher voltage portion has a voltage value being at least two times a larger value of those of the lower voltage portions.

3. A driving method according to claim 1, wherein the higher voltage portion has a pulse width equal to or longer than a total pulse width of the lower voltage portions.

4. A liquid crystal apparatus, comprising a pair of substrates and a chiral smectic liquid crystal disposed between the substrates so as to form at least one pixel,

temperature detection means for detecting a temperature of the liquid crystal device by temperature detection means to determine whether the temperature is in a higher temperature range or a lower temperature range, and

signal waveform application means for selectively applying a higher temperature-signal waveform to one selected pixel when the detected temperature is in the higher temperature range and applying a lower temperature-signal waveform different from the higher temperature-signal waveform to said one selected pixel when the detected temperature is in the lower temperature range,

wherein the higher temperature-signal waveform comprises a clear pulse for placing the liquid crystal in a first state and a writing pulse subsequent to the clear pulse for selectively placing the liquid crystal in a second state depending on input data, and

said writing pulse comprises a higher voltage portion and a pair of lower voltage portions sandwiching the higher voltage portion.

5. A liquid crystal apparatus according to claim 4, wherein the higher voltage portion has a voltage value being at least two times a larger value of those of the lower voltage portions.

6. A liquid crystal apparatus according to claim 4, wherein the higher voltage portion has a pulse width equal to or longer than a total pulse width of the lower voltage portions.