Method of driving a ferroelectric liquid crystal matrix panel

• US 5,011,269 A
• Filed: 09/05/1986
• Issued: 04/30/1991
• Est. Priority Date: 09/06/1985
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Uemura, Tsuyoshi, Wakita, Naohide, Ohba, Noriko, Ota, Isao, Ohnishi, Hiroyuki
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US06/903,772
• Time in Patent Office: 1,698 Days
• Field of Search: 350/332, 350/350 S, 350/333, 340/784, 340/805, 340/811, 340/802
• US Class Current: 345/89
• 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 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

A driving method in accordance with the present invention permits the simple time sharing driving of a ferroelectric liquid crystal matrix panel at high scanning frequency and high multiplexing ratio. A predetermined pulse is applied to a scanning electrode when another scanning electrode is selected to reset the pixel. The pixel is inverted or kept by the action of a pulse applied to the pixel when selected and, under this condition, a desired brightness is written in a short scanning period. Besides, the representation of a number of grey levels is obtained by multiple scanning at reset timing varying with the scanning.

Claims

1. A method of driving a liquid crystal matrix panel of the type in which ferroelectric liquid crystal is held between scanning electrodes and signal electrodes to form a matrix-arrayed pixels, characterized by:

applying a first group of pulse voltages during a reset phase to an Nth scanning electrode connected to pixels in an Nth row when pixels in another row are selected, said first group of pulse voltages having enough peak value and pulse width to bring the pixels in the Nth row into a constant state of either bright or dark, thereby to reset said pixels in said Nth row; and

applying, during a selected phase in which the pixels in said Nth row are to be selected, a second group of pulse voltages so that the pixels in said Nth row are either inverted or keep their state in accordance with signal voltages applied to the signal electrodes, wherein one grey-level is obtained by making a multiple number of field scannings while applying said first group of pulse voltages at different timing with each field scanning.

2. A method as claimed in claim 1, wherein, the number of grey-levels each obtainable by a single pixel in one field scanning is an integer K, field scannings are effected n times in each of which the reset phase is taken as generally 1/kⁱ (i=0, 1, . . . , n-1) from the start of the field scanning period, and signal voltages each corresponding to the coefficient of Kⁱ of grey level data are applied to the signal electrodes in an ith field scanning, so as to thereby obtain Kⁿ grey levels.