Method of driving a ferroelectric liquid crystal matrix panel

• US 5,095,377 A
• Filed: 08/02/1990
• Issued: 03/10/1992
• Est. Priority Date: 08/02/1990
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Gohara, Yoshihiro, Wakita, Naohide, Kobayashi, Yoshinori
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US07/561,576
• Time in Patent Office: 586 Days
• Field of Search: 350/332, 350/333, 350/350 S, 340/784, 340/805
• 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 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

In a method of driving a liquid crystal matrix panel, a group of voltage pulses are applied to each pixel connected to a scanning line during a reset period prior to a selection period so as to reset the state of each pixel before writing data. When the voltage pulse group contains a voltage pulse having a voltage whose absolute value is at least equal an absolute value of a threshold voltage of the liquid crystal, the group also contains, before or after the voltage pulse, a voltage pulse having a voltage whose absolute value is smaller than the absolute value of the threshold voltage and whose polarity is opposite to that of the former voltage pulse.

Claims

1. A method of driving a liquid crystal matrix panel for realizing a desired light transmission state, in a liquid crystal matrix panel for forming pixels arranged in a matrix by interposing a ferrodielectric liquid crystal between a pair of substrates having scanning and signal lines on confronting surfaces, by applying to the pixels a first pulse voltage group possessing a sufficient voltage value and pulse width for setting all pixels selected by a desired scanning line in a reset period of the scanning line in one of either a "bright" or a "dark" state regardless of a voltage applied to a signal line, and either inverting or maintaining the same state by a display data by a second pulse voltage group applied to the pixels in a selection period;

wherein the application period of the first pulse voltage group is at least an integer multiple of 2 of the application period of the second pulse voltage group;

wherein the first pulse voltage group consists of a first half pulse voltage group and a second half pulse voltage group, and

wherein when one of the first half and second half pulse voltage groups contains a first voltage pulse whose absolute value of voltage is at least equal to an absolute value of a threshold voltage of the liquid crystal, said one of the first half and second half pulse voltage groups also contains a second voltage pulse whose absolute value of voltage is smaller than the absolute value of the threshold voltage of the liquid crystal and whose polarity is opposite to that of the first voltage pulse, said second voltage pulse being applied immediately before said first voltage pulse in the first half pulse voltage group and immediately after said first voltage pulse in the second half pulse voltage group.

2. A method according to claim 1, wherein when a maximum voltage value of the voltage pulses applied to the pixels is V₀, said first voltage pulse is V₀ and said second voltage pulse is -V₀ /a (where a≧

2).

3. A method according to claim 2, wherein a voltage value of voltage pulses applied to the pixels in periods other than the periods of applying the first pulse voltage group and the second pulse voltage group is ±

V₀ /a.

4. A method according to claim 1, wherein if said first voltage pulse is +V₀, said second voltage pulse immediately before or after said first voltage pulse of +V₀ is -V₀ /a (where a≧

2), and if said first voltage pulse is -V₀, said second voltage pulse immediately before or after said first voltage pulse of -V₀ is +V₀ /a.

5. A method according to claim 1, wherein an average value of voltage of said first half pulse voltage group and an average volume of voltage of said second half pulse voltage group are the same in absolute value and reverse in polarity to each other so that an average value of voltage of said first pulse voltage group is zero.