Method of driving ferroelectric liquid crystal element

• US 5,227,900 A
• Filed: 03/19/1991
• Issued: 07/13/1993
• Est. Priority Date: 03/20/1990
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Inaba, Yutaka, Kurematsu, Katsumi, Kaneko, Shuzo
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US07/671,449
• Time in Patent Office: 847 Days
• Field of Search: 359/56, 359/57, 359/85, 359/100, 340/784, 340/805, 340/811
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• 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 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/367 with a nonlinear element in series with the liquid crystal cell, e.g. a diode, or M.I.M. element

Abstract

A method of driving a liquid crystal display element in which a switching element is provided for each of pixel electrodes arranged in a matrix manner and a ferroelectric liquid crystal is sandwiched between the pixel electrodes and a counter electrode includes the steps of applying a reset voltage for resetting the entire pixel to a first stable state of the ferroelectric liquid crystal across the pixel electrode and the counter electrode, partially transiting the pixel to a second stable state by a tone signal voltage having a pole opposite to that of the reset voltage, and reversing the pole of the reset voltage every predetermined period. Assuming that a state reverse ratio of the ferroelectric liquid crystal is T(V)% when the tone signal voltage is V, a tone signal voltage V₁ after negative resetting and a corresponding tone signal voltage -V₂ after positive resetting satisfy the following relation:

T(V.sub.1)+T(V.sub.2)=100

Claims

1. A method of driving a liquid crystal display element in which a switching element is provided for each of pixel electrodes arranged in a matrix manner and a ferroelectric liquid crystal is sandwiched between said pixel electrodes and a counter electrode, wherein the method displays a gradational picture on the display element through one cycle scanning and comprises the steps of:

applying a reset voltage for resetting the entire pixel to a first stable state of said ferroelectric liquid crystal across said pixel electrode and said counter electrode;

partially transiting said pixel to a second stable state by a tone signal voltage having an opposite polarity to that of the reset voltage; and

reversing the polarity of the reset voltage every predetermined period,

wherein if a state reverse ratio of said ferroelectric liquid crystal is indicated as T(V) when the tone signal voltage is V, a tone signal voltage V₁ after negative resetting and a corresponding tone signal voltage -V₂ after positive resetting satisfy the following relation;

space="preserve" listing-type="equation">T(V.sub.1)+T(V.sub.2)=100.

2. A method according to claim 1, wherein the predetermined period is a scanning period of one frame.

3. A method according to claim 1, wherein reset voltages of neighboring scanning lines have opposite poles.

4. A method according to claim 1, wherein said first stable state corresponds to a black status.

5. A ferroelectric liquid crystal device for displaying a gradational image picture and having a switching element provided for each of pixel electrodes arranged in a matrix array and ferroelectric liquid crystal interposed between opposite electrodes, comprising:

means for alternately applying a reset voltage and a tone signal voltage to the opposite electrodes, the reset voltage being a voltage of resetting the whole pixels into a first stable state and the tone signal voltage being a voltage in an opposite polarity to the reset voltage and transitting part of the pixels into a second stable state;

means for reversing the polarity of the reset voltage at every predetermined period; and

means for reversing the polarity of the tone signal voltage at every predetermined period, and

wherein if a state reverse ratio of said ferroelectric liquid crystal is indicated as T(V) when the tone signal voltage is V, a tone signal voltage V₁ after negative resetting and a corresponding tone signal voltage -V₂ after positive resetting satisfy the following relation;

space="preserve" listing-type="equation">T(V.sub.1)+T(V.sub.2)=100.

6. A ferroelectric liquid crystal device according to claim 5, wherein the predetermined period is a scanning period of one frame.

7. A ferroelectric liquid crystal device according to claim 5, wherein reset voltages of neighboring scanning lines have opposite poles.

8. A ferroelectric liquid crystal device according to claim 5, wherein said first stable state corresponds to a black status.