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Driving method for ferroelectric liquid crystal optical modulation device using an auxiliary signal to prevent inversion

  • US 5,092,665 A
  • Filed: 08/08/1989
  • Issued: 03/03/1992
  • Est. Priority Date: 01/23/1984
  • Status: Expired due to Fees
First Claim
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1. A driving method for an optical modulation device having a plurality of picture elements arranged in a matrix and comprising scanning lines, data lines spaced apart from and intersecting with the scanning lines, and a chiral smectic liquid crystal assuming a first orientation state or a second orientation state depending on the direction of an electric field applied thereto interposed between the scanning lines and the data lines, each of the intersections between the scanning lines and the data lines forming one of said plurality of picture elements;

  • said driving method comprising;

    an erasure step wherein a voltage, exceeding a first threshold voltage of the chiral smectic liquid crystal for causing the chiral smectic liquid crystal to assume the first orientation state, is applied to the intersections of the scanning lines and the data lines;

    a writing step wherein a scanning selection signal comprising a voltage of one polarity and a voltage of the other polarity with respect to the voltage of a non-selected scanning line is applied to a selected scanning line, an information selection signal is applied to a selected data line, the information selection signal providing a voltage exceeding a second threshold voltage of the chiral smectic liquid crystal for causing the chiral smectic liquid crystal to assume the second orientation state at the intersection of the selected scanning line and the selected data line in combination with the voltage of one polarity of the scanning selection signal, an information non-selection signal is applied to other data lines, the information non-selection signal providing a voltage between the first and second threshold voltages of the chiral smectic liquid crystal at the intersections of the selected scanning line and said other data lines in combination with the voltage of one polarity of the scanning selection signal, and a first auxiliary signal comprising a voltage of a polarity opposite to that of said information selection signal is applied to said selected data line, or a second auxiliary signal comprising a voltage of a polarity opposite to that of said information non-selection signal is applied to said other data lines, respectively, in synchronism with the voltage of the other polarity of the scanning selection signal.

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