Method and apparatus for driving ferroelectric liquid crystal device

• US 4,844,590 A
• Filed: 05/22/1986
• Issued: 07/04/1989
• Est. Priority Date: 05/25/1985
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Okada, Shinjiro, Enari, Masahiko
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Duong, Tai van
• Application Number:
  US06/865,867
• Time in Patent Office: 1,139 Days
• Field of Search: 350/350 S, 350/332, 350/333, 340/805, 340/811, 340/713, 340/714, 340/802, 340/784
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3681 suitable for passive matrices only
• CPC Class Codes: G09G 3/3692 suitable for passive matrices only

Abstract

A driving method for a ferroelectric liquid crystal device having a matrix electrode arrangement comprising a plurality of scanning lines and a plurality of data lines, and a ferroelectric liquid crystal disposed between the scanning lines and the data lines and having a threshold voltage for swtiching, a picture element being formed at each intersection of the scanning lines and the data lines. The driving method has a previous scanning period in which a prescribed number of scanning lines are scanned line-sequentially; a subsequent scanning period in which a prescribed number of subsequent scanning lines are scanned line-sequentially; and an auxiliary signal-application period provided between the previous and subsequent scanning periods, in which an auxiliary signal below the threshold voltage is applied to all or a prescribed part of the picture elements.

Claims

1. A ferroelectric liquid crystal apparatus comprising:

a ferroelectric liquid crystal device having a matrix electrode arrangement comprising a plurality of scanning lines and a plurality of data lines, and a ferroelectric liquid crystal disposed between the scanning lines and the data lines, a picture element being defined at each intersection of the scanning lines and the data lines;

first means for serially applying a scanning signal to said plurality of scanning lines and for applying in parallel data signals of a first voltage level and a given polarity to at least one selected data line of said plurality of data lines and data signals of a second voltage level at least one non-selected data line of said plurality of data lines;

second means for detecting data signals consecutively applied to said data lines by said first means and outputting a detection signal when consecutive data signals of the same voltage polarity, with respect to the second voltage level of one of said non-selected scanning lines, are applied to a particular data line; and

third means for controlling said first means responsive to the detection signal so as to apply a voltage signal at the same level as the second voltage level and so as to apply an auxiliary signal of a voltage polarity opposite to the given polarity to said particular data line in synchronism with the voltage signal.

2. An apparatus according to claim 1, wherein said ferroelectric liquid crystal comprises a chiral smectic liquid crystal.

3. An apparatus according to claim 1, wherein said ferroelectric liquid crystal comprises a chiral smectic liquid crystal showing a first stable state and a second stable state in the absence of an applied electric field.

4. An apparatus according to claim 1, wherein said second means issue a detection signal when 5 consecutive data signals of the same type are applied to said particular data line.