Liquid crystal apparatus and driving method

• US 5,602,562 A
• Filed: 11/24/1993
• Issued: 02/11/1997
• Est. Priority Date: 04/03/1987
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tsuboyama, Akira, Inoue, Hiroshi, Mizutome, Atsushi, Taniguchi, Osamu, Onitsuka, Yoshihiro, Mihara, Tadashi
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): STOLL, KARA FARNANDEZ
• Application Number:
  US08/156,976
• Time in Patent Office: 1,175 Days
• Field of Search: 345/87, 345/94, 345/95, 345/97, 345/101, 359/36, 359/43, 359/54, 359/55, 359/56, 359/86, 359/100, 359/104
• US Class Current: 345/101
• CPC Class Codes: G09G 2310/0224 Details of interlacing
• 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 2310/065 Waveforms comprising zero voltage phase or pause
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/207 by domain size control G09G3/3637 takes precedence
• 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 including scanning electrodes, data electrodes and a ferroelectric liquid crystal disposed between the scanning electrodes and the data electrodes. A scanning selection signal and a scanning nonselection signal are applied to the scanning electrodes. The data signals are applied to the data electrodes in phase with the scanning selection signal. The average voltage values of the data signals are varied during the period of applying a scanning selection signal.

Claims

1. A liquid crystal apparatus, comprising:

a liquid crystal device comprising scanning electrodes and data electrodes intersecting with the scanning electrodes, and a chiral smectic liquid crystal disposed between the scanning electrodes and the data electrodes, the chiral smectic liquid crystal having a first threshold voltage of one polarity for switching into a first optical state and a second threshold voltage of the other polarity for switching into a second optical state; and

voltage application means for;

applying a scanning selection signal and a scanning non-selection signal to the scanning electrodes, the scanning selection signal having a voltage of one polarity and a voltage of the other polarity with respect to a voltage level of a non-selected electrode, the scanning selection signal being periodically repetitively applied to the scanning electrodes, the polarity of the scanning selection signal applied to a particular scanning electrode being periodically inverted with respect to the voltage level of a non-selected scanning electrode so that an average with respect to time of the voltage applied to the particular scanning electrode is zero,

applying data signals to the data electrodes in phase with the scanning selection signal so as to apply an AC voltage to the intersections of the scanning electrodes and the data electrodes, said data signals having a voltage of one polarity and a voltage of the other polarity with respect to a voltage level of a non-selected scanning electrode,

superposing a DC offset voltage on the data signals, and

changing the DC offset voltage such that the DC offset voltage is decreased for an increase in operational temperature of the chiral smectic liquid crystal device and the DC offset voltage is increased for a decrease in the operational temperature in order to suppress temperature dependence of contrast in said apparatus.

2. An apparatus according to claim 1, wherein said chiral smectic liquid crystal is disposed in a layer thin enough to release its own helical structure in the absence of an electric field applied thereto.