Method for driving liquid crystal element employing ferroelectric liquid crystal

• US 4,508,429 A
• Filed: 04/13/1983
• Issued: 04/02/1985
• Est. Priority Date: 04/16/1982
• Status: Expired

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Nakano, Fumio, Nagae, Yoshiharu, Kawakami, Hideaki, Isogai, Masato
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Gallivan, Richard
• Application Number:
  US06/484,462
• Time in Patent Office: 720 Days
• Field of Search: 350/332, 350/333, 350/350 S
• US Class Current: 345/97
• 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

A method for driving a liquid crystal element including a ferroelectric liquid crystal sandwiched between a pair of substrates having electrodes on their opposite surfaces is disclosed. A pulse voltage for defining the light transmitting state of the liquid crystal element is applied to the ferroelectric liquid crystal. Before and/or after the application of the pulse voltage, the ferroelectric liquid crystal is applied with a voltage signal which renders the average value of voltages applied to the ferroelectric liquid crystal equal to zero.

Claims

1. A method for driving a liquid crystal element including a ferroelectric liquid crystal interposed between a pair of substrates which have electrodes on their confronting surfaces, said method comprising:

a first step of applying to said ferroelectric liquid crystal a pulse voltage which defines the light transmitting state of said liquid crystal element; and

a second step of applying to said ferroelectric liquid crystal before and/or after said first step a voltage signal which renders the average value of voltages applied to said ferroelectric liquid crystal equal to zero.

2. A method according to claim 1, wherein the DC component of said voltage signal has an opposite polarity and the same absolute value as compared with said pulse voltage.

3. A method according to claim 2, wherein said voltage signal has an opposite polarity, the same pulse width and the same pulse height as compared with said pulse voltage.

4. A method according to claim 1, wherein the pulse height of said voltage signal is smaller than the threshold voltage of said ferroelectric liquid crystal.

5. A method according to claim 1, wherein a period during which said pulse voltage is applied is relatively longer than that during which said voltage signal is applied.

6. A method according to claim 1, wherein said ferroelectric liquid crystal includes one selected from a group consisting of chiral smectic C-phase liquid crystal and chiral smectic H-phase liquid crystal.

7. A method according to claim 1, wherein a dichroic dye is mixed into said ferroelectric liquid crystal.

8. A method according to claim 1, wherein a polarizer is placed adjacent to at least one of said substrates.

9. A method according to claim 8, wherein the polarization direction of said polarizer adjacent to one of said substrates is made to nearly coincide with the direction of the long molecular axis of said ferroelectric liquid crystal when an electric field exceeding the threshold voltage of said ferroelectric liquid crystal is applied.