Driving method for liquid crystal devices

• US 6,028,579 A
• Filed: 06/09/1997
• Issued: 02/22/2000
• Est. Priority Date: 06/12/1996
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tsuboyama, Akira, Iba, Jun, Katakura, Kazunori
• Primary Examiner(s): Luu, Matthew
• Application Number:
  US08/871,375
• Time in Patent Office: 988 Days
• Field of Search: 345/87, 345/94, 345/95, 345/100, 345/97
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• 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 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3633 with transmission/voltage characteristic comprising multiple loops, e.g. antiferroelectric liquid crystals

Abstract

A liquid crystal device of the type including a pair of substrates having thereon a group of scanning electrodes and a group of data electrodes, and a chiral smectic liquid crystal disposed between the substrates so as to form a pixel at each intersection of the scanning electrodes and the data electrodes, is driven by a driving method causing less crosstalk. The driving method includes the steps of sequentially applying a scanning selection signal to the scanning electrodes, and applying data signals to the data electrodes in synchronism with the scanning selection signal. The scanning selection signal includes a writing pulse having a pulse width ΔT for determining an optical state of the chiral smectic liquid crystal in cooperation with a data signal. Each data signal includes a data pulse for determining an optical state of the chiral smectic liquid crystal in cooperation with the writing pulse. A plurality of data signals are each designed to have a waveform determined based on a combination of data applied to pixels on at least two consecutively selected scanning electrodes. At least one of said plurality of data signals include an auxiliary pulse having a pulse width shorter than ΔT.

Claims

1. 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, and a chiral smectic 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:

sequentially applying a scanning selection signal to the scanning electrodes, and

applying data signals to the data electrodes in synchronism with the scanning selection signal, wherein

the scanning selection signal comprises a writing pulse having a pulse width Δ

T for determining an optical state of the chiral smectic liquid crystal in cooperation with a data signal,

each data signal comprises a data pulse for determining an optical state of the chiral smectic liquid crystal in cooperation with the writing pulse,

a data signal applied to a data line is determined based on data to be displayed at a particular pixel on the data line and a current scanning electrode and also on data to be displayed at a subsequent pixel on the data line and a subsequently selected scanning electrode, and

at least one of said plurality of data signals includes an auxiliary pulse having a pulse width shorter than Δ

T.

2. A driving method according to claim 1, wherein at least one of said plurality of data signals has a DC component within a selection period for one line of scanning electrode.

3. A driving method according to claim 1, wherein said chiral smectic liquid crystal is a ferroelectric liquid crystal.

4. A driving method according to claim 1, wherein said chiral smectic liquid crystal is an anti-ferroelectric liquid crystal.

5. A driving method according to claim 2, wherein said plurality of data signals include a first data signal including an auxiliary pulse having a pulse width shorter than Δ

T and a second data signal including an auxiliary signal having a pulse width equal to Δ

T, and only one of said first and second data signals has a DC component within a selection period for one line of scanning electrode.

6. A driving method according to claim 1, wherein at least one of said plurality of data signals has a zero voltage period at a first portion or a final portion of a selection period for one line of scanning electrode.

7. A driving method according to claim 1, wherein, in a case where consecutively applied two data are different from each other, a data signal corresponding to one of said two data includes a zero voltage period.

8. A driving method according to any one of claims 1-7, wherein, in a case where consecutively applied two data are identical to each other, a data signal corresponding to the identical data has a DC component of zero.

9. A driving method according to claim 7, wherein said data signal including a zero voltage period has a non-zero DC component.

10. 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, 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:

sequentially applying a scanning selection signal to the scanning electrodes, and

applying data signals to the data electrodes in synchronism with the scanning selection signal, wherein

a data signal applied to a data line includes an auxiliary pulse having a first pulse width when a current pixel and a subsequent pixel on the data line are to display different data, and a data signal applied to a data line includes an auxiliary signal having a second pulse width longer than the first pulse when a current pixel and a subsequent pixel on the data line are to display identical data.