Driving method for liquid crystal cell and liquid crystal apparatus

• US 4,917,470 A
• Filed: 11/16/1988
• Issued: 04/17/1990
• Est. Priority Date: 01/14/1985
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Okada, Shinjiro, Kanbe, Junichiro
• Primary Examiner(s): Heyman, John S.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US07/273,745
• Time in Patent Office: 517 Days
• Field of Search: 350/331 R, 350/332, 350/333, 350/346, 350/350 S, 350/339 R, 350/341, 340/765, 340/784, 340/805, 340/811
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A driving method for a liquid crystal cell of the type comprising a pair of oppositely spaced electrodes and a memory type liquid crystal disposed between the oppositely spaced electrodes, the driving method comprising: applying a driving voltage waveform provided with an attenuation slope at the falling part thereof.

Claims

1. A driving method for a liquid crystal cell of the type constructed without a photoconductive layer comprising a pair of oppositely spaced electrodes forming a matrix electrode structure, a dielectric layer disposed on either one or both sides of the pair of electrodes, and a memory type ferroelectric liquid crystal disposed between the oppositely spaced electrodes, said driving method comprising the step of:

applying to the liquid crystal cell a driving voltage having a rectangular waveform of a duration provided with an attenuation slope at the falling part thereof.

2. The driving method according to claim 1, wherein said attenuation slope is expressed by a linear or exponential function.

3. The driving method according to claim 1, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal.

4. The driving method according to claim 1, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal having at least two stable states.

5. The driving method according to claim 1, wherein said ferroelectric liquid crystal is a bistable chiral smectic liquid crystal.

6. The driving method according to claim 1, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal with a non-spiral structure.

7. The driving method according to claim 1, which further comprises a dielectric layer of an insulating material between the pair of oppositely spaced electrodes.

8. A liquid crystal apparatus, comprising:

(a) a liquid crystal cell without a photoconductive layer comprising a pair of oppositely spaced electrodes forming a matrix electrode structure, a dielectric layer disposed on either one or both sides of the pair of electrodes, and a memory type ferroelectric liquid crystal disposed between the oppositely spaced electrodes;

(b) means for applying a driving voltage between the pair of electrodes, said means comprising means for applying a scanning voltage signal having a rectangular waveform of a duration provided with an attenuation slope at the falling part thereof; and

(c) means for detecting an optical change based on a change in orientation of the memory type ferroelectric liquid crystal.

9. The liquid crystal apparatus according to claim 8, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal having at least two stable states.

10. The liquid crystal apparatus according to claim 8, wherein said attenuation slope is expressed by linear or exponential function.

11. The liquid crystal apparatus according to claim 8, wherein one of said pair of electrodes is connected to a scanning side driver circuit and is supplied with a pulse voltage waveform comprising a rectangular rising part followed by a constant amplitude and a attenuated falling slope.