Ferroelectric display panel of varying thickness and driving method therefor

• US 4,712,877 A
• Filed: 01/15/1986
• Issued: 12/15/1987
• Est. Priority Date: 01/18/1985
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tsuboyama, Akira, Okada, Shinjiro, Inaba, Yutaka, Kanbe, Junichiro
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Gallivan, Richard F.
• Application Number:
  US06/819,070
• Time in Patent Office: 699 Days
• Field of Search: 350/333, 350/334, 350/350 S, 350/336
• US Class Current: 349/85
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/134345 Subdivided pixels, e.g. for grey scale or redundancy
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G02F 2203/30 Gray scale
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• 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 3/207 by domain size control G09G3/3637 takes precedence
• CPC Class Codes: G09G 3/3637 with intermediate tones displayed by domain size control domain size control in flat matrix panels other than liquid crystal displays having memory effects G09G3/207
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

A driving method for a liquid crystal device of the type comprising a picture element formed by a first electrode, a second electrode oppositely spaced from the first electrode, and a ferroelectric liquid crystal disposed at the opposite portion between the first and second electrodes and having a varying layer thickness. The driving method comprises: a first step of applying a voltage signal between the first and second electrodes for orienting a region extending over the whole area of the picture element to either one of a first and a second state, and a second step of applying a pulse with a waveform corresponding to gradation information between the first and second electrodes to switch the state of a region defining a prescribed area of the picture element from one state resultant in the first step to the other state.

Claims

1. A liquid crystal device, comprising:

a pair of oppositely spaced electrodes and a ferroelectric liquid crystal layer disposed between the pair of oppositely spaced electrodes, said ferroelectric liquid crystal layer having a varying thickness.

2. The liquid crystal device according to claim 1, wherein said pair of oppositely spaced electrodes comprise a plurality of scanning electrodes and a plurality of signal electrodes intersecting with the scanning electrodes, the ferroelectric liquid crystal layer disposed at each intersection of the scanning electrodes and the signal electrodes having a varying layer thickness.

3. The liquid crystal device according to claim 1, wherein said ferroelectric liquid crystal layer thickness varies continuously or stepwise.

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

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

6. The liquid crystal device according to claim 1, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal having a non-helical structure.

7. A driving method for a liquid crystal device of the type comprising a picture element formed by a first electrode, a second electrode oppositely spaced from the first electrode, and a ferroelectric liquid crystal disposed at the space between the first and second electrodes and having a varying layer thickness;

said driving method comprising;

a first step of applying a voltage signal between the first and second electrodes for orienting a region extending over the whole area of the picture element to either one of a first and a second state and,

a second step of applying a pulse with a waveform corresponding to gradation information between the first and second electrodes to switch the state of a region defining a prescribed area of the picture element from one state resultant in the first step to the other state.

8. A driving method for a liquid crystal device of the type comprising a matrix electrode structure having a plurality of scanning electrodes and a plurality of signal electrodes intersecting with the scanning electrodes, and a ferroelectric liquid crystal disposed at each intersection of the scanning and signal electrodes and having a varying layer thickness;

said driving method comprising;

a first step of applying at a time an electric signal between all or a part of the scanning electrodes and all or a part of the signal electrodes so that substantially the whole area at each intersection between said all or a part of the scanning and signal electrodes is oriented to either one of a first and a second state, and

a second step of applying a scanning selection signal to the scanning electrodes sequentially and row by row and, in phase with the scanning selection signal, applying a pulse signal with a waveform corresponding to gradation information to selected signal electrodes so that a prescribed area at each selected intersection is switched from one state resultant in the first step to the other state.

9. The driving method according to claim 8, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a voltage height varying depending on the gradation information.

10. The driving method according to claim 8, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a pulse duration varying depending on the gradation information.

11. The driving method according to claim 8, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a number of pulses varying depending on the gradation information.

12. The driving method according to claim 8, wherein the ferroelectric liquid crystal has a layer thickness varying continuously or stepwise.

13. A driving method for a liquid crystal device of the type comprising a matrix electrode structure having a plurality of scanning electrodes and a plurality of signal electrodes intersecting with the scanning electrodes, and a ferroelectric liquid crystal disposed at each intersection of the scanning and signal electrodes and having a varying layer thickness;

said driving method comprising;

a first step of sequentially applying a first scanning selection signal to the scanning electrodes and, in phase with the first scanning selection signal, applying a clearing signal to all or a prescribed part of the signal electrodes, so that substantially the whole area at each of all or a prescribed part of the intersections on the scanning electrodes is oriented to either one of a first and a second state, and

a second step of sequentially applying a second scanning selection signal to the scanning electrodes and, in phase with the second scanning selection signal, applying a pulse signal with a waveform corresponding to gradation information to selected signal electrodes so that a prescribed area at each selected intersection is switched from one state resultant in the first step to the other state.

14. The driving method according to claim 13, wherein said first and second scanning selection signals are applied to one scanning electrode consecutively in different phases.

15. The driving method according to claim 13, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a voltage height varying depending on the gradation information.

16. The driving method according to claim 13, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a pulse duration varying depending on the gradation information.

17. The driving method according to claim 13, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a number of pulses varying depending on the gradation information.

18. A liquid crystal device, comprising:

a pair of oppositely spaced electrodes and a ferroelectric liquid crystal layer disposed between the pair of oppositely spaced electrodes;

said ferroelectric liquid crystal layer having a varying thickness, said pair of oppositely spaced electrodes having a varying spacing therebetween.

19. The liquid crystal device according to claim 18, wherein said pair of oppositely spaced electrodes comprises a plurality of scanning electrodes and a plurality of signal electrodes intersecting with the scanning electrodes, the ferroelectric liquid crystal disposed at each intersection of the scanning electrodes and the signal electrodes has a varying layer thickness, and each pair of the scanning electrode and signal electrode sandwiching the ferroelectric liquid crystal at each intersection have a varying spacing therebetween.

20. The liquid crystal device according to claim 18, wherein both the thickness of the ferroelectric liquid crystal and the spacing between the oppositely spaced electrodes vary continuously or stepwise.

21. The liquid crystal device according to claim 18, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal having at least two stable orientation states.

22. The liquid crystal device according to claim 18, wherein said ferroelectric liquid crystal is a bistable chiral smectic liquid crystal.

23. The liquid crystal device according to claim 18, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal having a non-helical structure.

24. A driving method for a liquid crystal device of the type comprising a picture element formed by a first electrode, a second electrode oppositely spaced from the first electrode so as to form a varying spacing therebetween, and a ferroelectric liquid crystal disposed at the opposite portion between the first and second electrodes and having a varying layer thickness;

said driving method comprising;

a first step of applying a voltage signal between the first and second electrodes for orienting a region extending over the whole area of the picture element to either one of a first and a second state and,

a second step of applying a pulse with a waveform corresponding to gradation information between the first and second electrodes to switch the state of a region defining a prescribed area of the picture element from one state resultant in the first step to the other state.

25. The driving method according to claim 24, wherein both the thickness of the ferroelectric liquid crystal layer and the spacing between the oppositely spaced electrodes vary continuously or stepwise.

26. A driving method for a liquid crystal device of the type comprising a matrix electrode structure having a plurality of scanning electrodes and a plurality of signal electrodes intersecting with the scanning electrodes and a ferroelectric liquid crystal disposed at each intersection of the scanning and signal electrodes and having a varying layer thickness, each pair of the scanning electrode and signal electrode sandwiching the ferroelectric liquid crystal at each intersection having a varying spacing therebetween;

said driving method comprising;

a first step of applying at a time an electric signal between all or a part of the scanning electrodes and all or a part of the signal electrodes so that substantially the whole area at each intersection between said all or a part of the scanning and signal electrodes is oriented to either one of a first and a second state, and

a second step of applying a scanning selection signal to the scanning electrodes sequentially and row by row and, in phase with the scanning selection signal, applying a pulse signal with a waveform corresponding to gradation information to selected signal electrodes so that a prescribed area at each selected intersection is switched from one state resultant in the first step to the other state.

27. The driving method according to claim 26, wherein both the thickness of the ferroelectric liquid crystal layer and the spacing between the oppositely spaced electrodes vary continuously or stepwise.

28. The driving method according to claim 26, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a voltage height varying depending on the gradation information.

29. The driving method according to claim 26, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a pulse duration varying depending on the gradation information.

30. The driving method according to claim 26, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a number of pulses varying depending on the gradation information.

31. A driving method for a liquid crystal device of the type comprising a matrix electrode structure having a plurality of scanning electrodes and a plurality of signal electrodes intersecting with the scanning electrodes, and a ferroelectric liquid crystal disposed at each intersection of the scanning and signal electrodes and having a varying layer thickness, each pair of the scanning electrode and the signal electrode sandwiching the ferroelectric liquid crystal at each intersection having a varying spacing therebetween;

said driving method comprising;

a first step of sequentially applying a first scanning selection signal to the scanning electrodes and, in phase with the first scanning selection signal, applying a clearing signal to all or a prescribed part of the signal electrodes, so that substantially the whole area at each of all or a prescribed part of the intersections on the scanning electrodes is oriented to either one of a first and a second state, and

a second step of sequentially applying a second scanning selection signal to the scanning electrodes and, in phase with the second scanning selection signal, applying a pulse signal with a waveform corresponding to gradation information to selected signal electrodes so that a prescribed area at each selected intersection is switched from one state resultant in the first state to the other state.

32. The driving method according to claim 31, wherein both the thicknesses of the ferroelectric liquid crystal layer and the spacings between the oppositely spaced electrodes vary continuously or stepwise.

33. The driving method according to claim 31, wherein said first and second scanning selection signals are applied to one scanning electrode consecutively in different phases.

34. The driving method according to claim 31, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a voltage height varying depending on the gradation information.

35. The driving method according to claim 31, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a pulse duration varying depending on the gradation information.

36. The driving method according to claim 31, wherein said pulse signal with a waveform corresponding to gradation information is a signal having a number of pulses varying depending on the gradation information.

37. A liquid crystal device, comprising:

a first base plate, a second base plate;

a pair of electrodes disposed respectively on the first and second base plates, an insulating film disposed on at least one of said pair of electrodes and having a varying thickness, and a ferroelectric liquid crystal layer disposed between the first and second base plates and having a varying thickness.

38. The liquid crystal device according to claim 37, wherein the thicknesses of both the insulating layer and the ferroelectric liquid crystal layer vary continuously or stepwise.

39. The liquid crystal device according to claim 37, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal having at least two stable orientation states.

40. The liquid crystal device according to claim 37, wherein said ferroelectric liquid crystal is a bistable chiral smectic liquid crystal.

41. The liquid crystal device according to claim 37, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal having a non-helical structure.