Driving method for liquid crystal device

• US 4,800,382 A
• Filed: 12/24/1985
• Issued: 01/24/1989
• Est. Priority Date: 12/28/1984
• 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): Brigance, Gerald L.
• Assistant Examiner(s): Brier, Jeffery A.
• Application Number:
  US06/813,239
• Time in Patent Office: 1,127 Days
• Field of Search: 340/784, 340/805, 350/331 R, 350/350 S
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/063 Waveforms for resetting the whole screen at once
• 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 device of the type comprising a matrix electrode structure having scanning lines and data lines, and a ferroelectric liquid crystal. In the driving method, (a) in a first period, a scanning selection signal is applied to a scanning line and applying an information signal is applied to a data line in synchronism with the scanning selection signal, and (b) in a second period, an alternating auxiliary signal is applied to the data line.

Claims

1. A liquid crystal apparatus, comprising:

a ferroelectric liquid crystal device having;

a group of scanning electrodes;

a group of signal electrodes disposed to intersect the scanning electrodes; and

a ferroelectric liquid crystal having a first and a second threshold voltage of one and another polarity, respectively, disposed between the scanning electrodes and the signal electrodes so as to form a picture element at each intersection; and

voltage signal application means for;

(a) applying to a selected scanning electrode a scanning selection signal comprising;

a voltage of one polarity or another polarity with respect to the voltage level of a non-selected scanning electrode; and

a same level voltage which is at the same voltage level as that of the non-selected scanning electrode;

(b) applying to a selected electrode an information signal comprising;

a first voltage signal providing a voltage exceeding the first or second threshold voltage in synchronism with said voltage of one polarity or another polarity; and

an alternating voltage signal commencing with a voltage of a polarity opposite to that of the first voltage signal with respect to the voltage level of the non-selected scanning electrode in the application period of said same level voltage; and

(c) applying to another signal electrode an information signal comprising;

a second voltage signal providing a voltage not exceeding the first or second threshold voltage of the ferroelectric liquid crystal in synchronism with said voltage of one polarity or the another polarity; and

an alternating voltage signal commencing with a voltage of a polarity opposite to that of the second voltage signal with respect to the voltage level of the non-selected scanning electrode in the application period of said same level voltage.

2. The apparatus according to claim 1, wherein the average voltage of each of the information signals is at the same level as the voltage level of the non-selected scanning electrode throughout the application period of the scanning selection signal.

3. The apparatus according to claim 1, wherein the voltage level of the non-selected scanning electrode is zero.

4. The apparatus according to claim 1, wherein each of the first and second voltage signals has a pulse duration T and each of the alternating voltage signals comprises pulses having unit pulse duration T₀ which is shorter than T.

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

6. The apparatus according to claim 5, wherein said chiral smectic liquid crystal assumes a non-spiral structure.

7. The apparatus according to claim 5, wherein said chiral smectic liquid crystal is in the C phase, the H phase, the I phase, the J phase, the K phase, the G phase or the F phase.

8. The apparatus according to claim 1, wherein each of the alternating voltage signals is applied after the first or second voltage signal and another alternating voltage signal is applied before the first or second voltage signal.

9. A liquid crystal apparatus, comprising:

a ferroelectric liquid crystal device comprising;

a group of scanning electrodes;

a group of signal electrodes disposed to intersect the scanning electrodes; and

a ferroelectric liquid crystal having a first and a second threshold voltage of one and another polarity, respectively, disposed between the scanning electrodes and the signal electrodes so as to form a picture element at each intersection; and

voltage signal application means for;

(a) applying to a selected scanning electrode a scanning selection signal comprising;

a voltage of one polarity and a voltage of another polarity, respectively, with respect to the voltage level of a non-selected scanning electrode; and

a same level voltage at the same voltage level as that of the non-selected scanning electrode;

(b) applying to a selected signal electrode an information signal comprising;

a first voltage signal providing a voltage exceeding the first threshold voltage in synchronism with said voltage of one polarity; and

an alternating voltage signal commencing with a voltage of a polarity opposite to that of the first voltage signal with respect to the voltage level of the non-selected scanning electrode in the application period of said same level voltage; and

(c) applying to another signal electrode an information signal comprising;

a second voltage signal providing a voltage exceeding the second threshold voltage of the ferroelectric liquid crystal in synchronism with said voltage of another polarity; and

an alternating voltage signal commencing with a voltage of a polarity opposite to that of the second voltage signal with respect to the voltage level of the non-selected scanning electrode in the application period of said same level voltage.

10. The apparatus according to claim 9, wherein the voltage of one polarity and the voltage of the another polarity in the scanning selection signal are consecutive in time.

11. The apparatus according to claim 9, wherein the voltage level of the non-selected scanning electrode is zero.

12. The apparatus according to claim 9, wherein each of the first and second voltage signals has a pulse duration T and each of the alternating voltage signals comprises pulses having a unit pulse duration T₀ which is shorter than T.

13. The apparatus according to claim 9, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal.

14. The apparatus according to claim 13, wherein said chiral smectic liquid crystal assumes a non-spiral structure.

15. The apparatus according to claim 13, wherein said chiral smectic liquid crystal is in the C phase, the H phase, the I phase, the J phase, the K phase, the G phase, or the F phase.

16. The apparatus according to claim 9, wherein each of the alternating voltage signals is applied after the first or second voltage signal and another alternating voltage signal is applied before the first or second voltage signal.

17. The apparatus according to claim 9, wherein each of the information signals integrally assumes a voltage of the same level as the voltage level of the non-selected scanning electrode throughout the application period of the scanning selection signal.

18. A liquid crystal apparatus, comprising:

a ferroelectric liquid crystal device comprising;

a group of scanning electrodes;

a group of signal electrodes disposed to intersect the scanning electrodes; and

a ferroelectric liquid crystal having a first and a second threshold voltage of one and another polarity, respectively, disposed between the scanning electrodes and the signal electrodes so as to form a picture element at each intersection; and

voltage signal application means for;

(a) applying to a selected scanning electrode a scanning selection signal comprising;

a voltage of one polarity and a voltage of another polarity with respect to the voltage level of a non-selected scanning electrode; and

a same level voltage which is at the same voltage level as that of the non-selected scanning electrode;

(b) applying to all or a prescribed number of the signal electrodes a first voltage signal providing a voltage exceeding the first threshold voltage of the ferroelectric liquid crystal in synchronism with said voltage of one polarity; and

(c) applying to a selected signal electrode an information signal comprising;

a second voltage signal providing a voltage not exceeding the second threshold voltage of the ferroelectric liquid crystal in synchronism with said voltage of the another polarity; and

an alternating voltage signal commencing with a voltage of a polarity opposite to that of the second voltage signal with respect to the voltage level of the non-selected scanning electrode in the application period of said same level voltage.

19. The apparatus according to claim 18, wherein the voltage of one polarity and the voltage of the another polarity in the scanning selection signal are consecutive in time.

20. The apparatus according to claim 18, wherein the voltage level of the non-selected scanning electrode is zero.

21. The apparatus according to claim 18, wherein each of the first and second voltage signals has a pulse duration T and the alternating voltage signal comprises pulses having a unit pulse duration T₀ which is shorter than T.

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

23. The apparatus according to claim 22, wherein said chiral smectic liquid crystal assumes a non-spiral structure.

24. The apparatus according to claim 22, wherein said chiral smectic liquid crystal is in the C phase, the H phase, the I phase, the J phase, the K phase, the G phase or the F phase.

25. The apparatus according to claim 18, wherein the alternating voltage signal is applied after the first or second voltage signal and another alternating voltage signal is applied before the first or second voltage signal.

26. The apparatus according to claim 18, wherein said voltage of one polarity is applied to all or a prescribed number of the scanning electrodes simultaneously.

27. The apparatus according to claim 18, wherein the average voltage of the information signal is at the same level as the voltage level of the non-selected scanning electrode throughout the application period of the scanning selection signal.

28. A driving method for a liquid crystal device of the type comprising a matrix electrode structure having a first group of stripe electrodes and a second group of stripe electrodes disposed opposite to and intersecting the first group of stripe electrodes, and a ferroelectric liquid crystal displaying a first state and a second state and disposed between the first and second groups of stripe electrodes so as to form a picture element at each intersection of the stripe electrodes, said driving method comprising the steps of:

applying a first voltage signal to a plurality of said picture elements for orienting the ferroelectric liquid crystal in the first state in a first phase for a duration Δ

T, and applying a second voltage signal to said plurality of picture elements for orienting the ferroelectric liquid crystal in the second state in a second phase for a duration Δ

T, whereby writing is effected in the first and second phases; and

applying to the remaining picture elements an alternating voltage signal such that the maximum duration during which any voltage of one polarity of the alternating voltage is applied to the remaining picture elements is 3Δ

T.

29. The driving method according to claim 28, wherein said first and second phases are consecutive in time.

30. The driving method according to claim 29, wherein the average potential of the alternating voltage signal throughout the application period of the scanning selection signal is substantially equal to a reference potential, wherein said reference potential is zero.

31. The driving method according to claim 28, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal.

32. The driving method according to claim 31, wherein said chiral smectic liquid crystal assumes a non-spiral structure.

33. The driving method according to claim 31, wherein said chiral smectic liquid crystal is in the C phase, the H phase, the I phase, the J phase, the K phase, the G phase or the F phase.

34. The driving method according to claim 28, further comprising the step of:

applying to a selected first stripe electrode a scanning selection signal comprising a voltage of one polarity and a voltage of another polarity, respectively, with respect to the voltage level of a non-selected first strips electrode, and in synchronism with the scanning selection signal, and applying to a signal electrode an information signal which integrally assumes the same voltage level as the voltage level of the non-selected first stripe electrode throughout the application period of the scanning selection signal.

35. The driving method according to claim 34, wherein the voltage level of said non-selected first stripe electrode is zero.

36. A driving method for a liquid crystal device of the type comprising a matrix electrode structure having a plurality of first stripe electrodes and a plurality of second stripe electrodes disposed opposite to and intersecting said first stripe electrodes, and a ferroelectric liquid crystal displaying a first state and a second state and disposed between the first and second stripe electrodes so as to form a picture element at each intersection of the stripe electrodes;

said driving method comprising the steps of;

in a first phase, applying a voltage signal for orienting the ferroelectric liquid crystal in the first stage simultaneously to the intersections of all or a prescribed part of the first strips electrodes and all or a prescribed part of the second stripe electrodes;

in a second phase,

applying to a selected first stripe electrode a scanning selection signal comprising;

a voltage with a duration Δ

T of one or another polarity with respect to the voltage level of the non-selected first stripe electrode; and

a same level voltage which is at the same voltage level as that of the non-selected first stripe electrode; and

applying an information signal comprising an alternating voltage in synchronism with the scanning selection signal; and

applying to the intersections of the second stripe electrodes and a non-selected first stripe electrode an alternating voltage signal such that the maximum duration during which any voltage of one polarity of the alternating voltage is applied to said intersections is 3 Δ

T.

37. The driving method according to claim 36, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal.

38. The driving method according to claim 37, wherein said chiral smectic liquid crystal assumes a non-spiral structure.

39. The driving method according to claim 37, wherein said chiral smectic liquid crystal is in the C phase, the H phase, the I phase, the G phase or the F phase.

40. The driving method according to claim 36, wherein the voltage level of said non-selected first stripe electrode is zero.

41. The driving method according to claim 36, wherein the average voltage of the information signal is at the same voltage level as the voltage level of the non-selected first stripe electrode throughout the application period of the scanning selection signal.

42. The driving method according to claim 41, wherein the voltage level of said non-selected first stripe electrode is zero.