Liquid crystal apparatus and driving method

• US 5,691,740 A
• Filed: 05/04/1995
• Issued: 11/25/1997
• Est. Priority Date: 04/03/1987
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tsuboyama, Akira, Inoue, Hiroshi, Mizutome, Atsushi, Taniguchi, Osamu, Onitsuka, Yoshihiro, Mihara, Tadashi
• Primary Examiner(s): BRIER, JEFFERY A
• Application Number:
  US08/434,990
• Time in Patent Office: 936 Days
• Field of Search: 345/94-97, 359/55, 359/56, 359/84, 359/85, 349/33, 349/34, 349/37
• US Class Current: 345/96
• CPC Class Codes: G09G 2310/0224 Details of interlacing
• 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 2310/065 Waveforms comprising zero voltage phase or pause
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2320/041 Temperature compensation
• 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 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A liquid crystal display apparatus having scanning electrodes, data electrodes, and ferroelectric liquid crystal material placed between the scanning electrodes and the data electrodes. Scanning signals are applied sequentially to the scanning electrodes to select a scanning electrode. Data signals are applied in synchronization with the scanning signals to place a voltage at the intersection of the data electrode and the selected scanning electrode which will place the ferroelectric material at the intersection into the desired optical state. The scanning signals and the data signals are such that pixels located at the intersection of the non selected scanning electrodes and data electrodes receive an AC voltage superimposed onto a DC voltage. Pixels on selected scanning electrodes may also receive the AC voltage superimposed onto the DC voltage. The DC voltage has its polarity inverted with every vertical scanning period.

Claims

1. A liquid crystal apparatus, comprising

a liquid crystal device comprising scanning electrodes and data electrodes intersecting with the scanning electrodes, and a chiral smectic liquid crystal disposed between the scanning electrodes and the data electrodes and assuming a first orientation state and a second orientation state depending on a voltage polarity applied thereto so as to form a pixel at each intersection of the scanning electrodes and the data electrodes;

and

voltage application means for;

applying a scanning selection signal and a scanning non-selection signal to the scanning electrodes, the scanning selection signal having a voltage of one polarity or a voltage of the other polarity with respect to a voltage level of a non-selected scanning electrode,

in synchronism with the scanning selection signal, selectively applying data signals each comprising an AC waveform having a voltage of one polarity and a voltage of the other polarity with respect to the voltage level of a non-selected scanning electrode to the data electrodes so that pixels at the intersections of a selected scanning electrode receiving the scanning selection signal and selected data electrodes receive a voltage causing a switching from the first orientation state to the second orientation state or a switching from the second orientation state to the first orientation state, and pixels at the intersections of a non-selected scanning electrode and the data electrodes receive an AC voltage superposed with a DC voltage not causing a switching from the first orientation state to the second orientation state or a switching from the second orientation state to the first orientation state, and

inverting the polarity of the DC voltage for each prescribed period.

2. An apparatus according to claim 1, wherein said voltage of one polarity and said voltage of the other polarity of a data signal have mutually different peak values.

3. An apparatus according to claim 1, wherein said prescribed period for inverting the polarity of the DC voltage corresponds to a frame period or a field period.

4. An apparatus according to claim 2, wherein said voltage of one polarity and said voltage of the other polarity of the scanning selection signal are applied to an odd-numbered frame or field and an even numbered frame or field, respectively.

5. An apparatus according to claim 1, wherein said scanning selection signal includes bipolar voltage signals having said voltage of one polarity and said voltage of the other polarity, and the bipolar voltage signals of the scanning selection signal applied in an odd-numbered frame or field and in an even-numbered frame or field are of mutually anti-phases.

6. An apparatus according to claim 1, wherein said scanning selection signal includes bipolar voltage signals having said voltage of one polarity and said voltage of the other polarity;

the bipolar voltage signals of the scanning selection signal applied to a particular scanning electrode in an odd-numbered frame or field and in an even-numbered frame or field are of mutually anti-phases; and

the bipolar voltage signals of scanning selection signal applied to an odd-numbered scanning electrode and an even-numbered scanning electrode in a particular frame or field are of mutually anti-phases.

7. An apparatus according to claim 1, wherein the scanning selection signal is periodically repetitively applied to the scanning electrodes, and the polarity of the scanning selection signal applied to a particular scanning electrode is periodically inverted with respect to the voltage level of a non-selected scanning electrode so that an average with respect to time of the voltage applied to the particular scanning electrode is zero.

8. A liquid crystal apparatus, comprising:

a liquid crystal device comprising scanning electrodes, data electrodes intersecting with the scanning electrodes, and a chiral smectic liquid crystal having a threshold voltage disposed between the scanning electrodes and the data electrodes so as to form a pixel at each intersection of the scanning electrodes and the data electrodes, and

voltage application means for;

applying a scanning selection signal to the scanning electrodes,

applying data signals to the data electrodes in synchronism with the scanning selection signal so that pixels at the intersection of a non-selected scanning electrode not receiving the scanning selection signal and the data electrodes receive an AC voltage superposed with a DC voltage not exceeding the threshold voltage of the chiral smectic liquid crystal, and

inverting a polarity of the DC voltage.

9. An apparatus according to claim 8, wherein said data signals each have a voltage of one polarity and a voltage of the other polarity with respect to the voltage level of a non-selected scanning electrode, the voltages of one polarity and the other polarity having mutually different peak values.

10. An apparatus according to claim 8, wherein said prescribed period for inverting the polarity of the DC voltage is synchronized with a frame period or a field period.

11. An apparatus according to claim 8, wherein said prescribed period for inverting the polarity of the DC voltage is synchronized with one scanning selection period.

12. An apparatus according to claim 8, wherein said scanning selection signal has a voltage of one polarity or a voltage of the other polarity with respect to the voltage level of a non-selected scanning electrode.

13. An apparatus according to claim 12, wherein the polarity of said voltage of one polarity or the other polarity of the scanning signal is inverted at each prescribed period.

14. An apparatus according to claim 13, wherein said prescribed period for polarity inversion is synchronized with a frame period or a field period.

15. An apparatus according to claim 13, wherein said prescribed period for polarity inversion is synchronized with one scanning selection period.

16. An apparatus according to claim 12, wherein the polarity of said voltage of one polarity or the other polarity of the scanning selection signal is inverted at each one scanning selection period and at each frame or field period.

17. An apparatus according to claim 8, wherein said scanning selection signal has a voltage of one polarity and a voltage of the other polarity with respect to the voltage level of a non-selected scanning electrode.

18. An apparatus according to claim 17, wherein the polarities of said voltage of one polarity and the other polarity of the scanning selection signal are inverted at each prescribed period.

19. An apparatus according to claim 18, wherein said prescribed method for polarity inversion is synchronized with a frame period or a field period.

20. An apparatus according to claim 18, wherein said prescribed period for polarity inversion is synchronized with one scanning selection period.

21. An apparatus according to claim 17, wherein the polarities of said voltage of one polarity and the other polarity of the scanning selection signal are inverted at each one scanning selection period and at each frame or field period.

22. An apparatus according to claim 8, wherein said chiral smectic liquid crystal is disposed in a layer thin enough to release its own helical structure in the absence of an electric field.

23. A liquid crystal apparatus, comprising:

(a) A liquid crystal device comprising scanning electrodes and data electrodes intersecting the scanning electrodes so as to form an electrode matrix, and a chiral smectic liquid crystal disposed between the scanning electrodes and the data electrodes so as to form a pixel at each intersection of the scanning electrodes and the data electrodes, said chiral smectic liquid crystal switching from a first orientation state to a second orientation state by application of a voltage exceeding a first threshold and switching from the second orientation state to the first orientation state by application of a voltage exceeding a second threshold;

(b) voltage application means for;

sequentially applying a scanning selection signal to the scanning electrodes to effect one vertical scanning, the scanning selection signal having a voltage of a first polarity or a voltage of a second polarity with reference to a voltage level of a scanning electrode not receiving the scanning selection signal,

applying data signals to the data electrodes in synchronism with the scanning selection signal, thereby to apply a voltage signal causing a switching from the first orientation state to the second orientation state or a switching from the second orientation state to the first orientation state to pixels at intersections of a scanning electrode receiving the scanning selection signal and the data electrodes, and to apply to intersections of scanning electrodes not receiving the scanning selection signal and the data electrodes a voltage signal which does not exceed either the first or second threshold and comprises an AC waveform superposed with a constant DC voltage in one vertical scanning period, and

(c) means for periodically changing a polarity of the constant DC voltage.

24. A liquid crystal apparatus, comprising:

(a) a liquid crystal panel comprising scanning electrodes and data electrodes intersecting the scanning electrodes so as to form an electrode matrix, and a chiral smectic liquid crystal disposed so as to form a pixel at each intersection of the scanning electrodes and the data electrodes, and

(b) drive means for;

sequentially applying a first scanning selection signal to the scanning electrodes to effect a first vertical scanning, said first scanning selection signal comprising a voltage signal of a first polarity and a voltage signal of a second polarity in a first phase and a second phase, respectively; and

sequentially applying a second scanning selection signal to the scanning electrodes to effect a second vertical scanning, the second scanning selection signal comprising a voltage of the second polarity and a voltage of the first polarity in the first phase and the second phase, respectively;

the first polarity and the second polarity being determined with reference to a voltage level of a scanning electrode not receiving any of the first and second scanning selection signals, the first phase being longer than the second phase;

applying to pixels at intersection of scanning electrodes not receiving any of the first and second scanning selection signals and the data electrodes a voltage signal of an AC waveform superposed with a DC component which is constant in one vertical scanning period; and

inverting a polarity of the DC component for each one vertical scanning.

25. A liquid crystal apparatus, comprising:

(a) a liquid crystal device comprising scanning electrodes and data electrodes intersecting the scanning electrodes so as to form an electrode matrix, and a liquid crystal disposed between the scanning electrodes and the data electrodes so as to form a pixel at each intersection of the scanning electrodes and the data electrodes, said liquid crystal having a memory characteristic of switching from a first memory state to a second memory state by application of a voltage exceeding one threshold and switching from the second memory state to the first memory state by application of a voltage exceeding another threshold, and

(b) voltage application means for

sequentially applying a scanning selection signal to the scanning electrodes to effect one vertical scanning, said scanning selection signal having a voltage of one polarity or a voltage of the other polarity with reference to a voltage level of a scanning electrode not receiving the scanning selection signal; and

applying to the data electrodes data signals in synchronism with the scanning selection signal and a DC voltage which has a polarity alternating in a period synchronized with said one vertical scanning period,

thereby to apply a voltage signal causing a switching from the first memory state to the second memory state or a switching from the second memory state to the first memory state to pixels at intersections of a scanning electrode receiving the scanning selection signal and the data electrodes, and to apply to intersections of scanning electrodes not receiving the scanning selection signal and the data electrodes a voltage signal which does not exceed either said one or another threshold.

26. A liquid crystal apparatus, comprising:

(a) a liquid crystal device comprising scanning electrodes and data electrodes intersecting the scanning electrodes so as to form an electrode matrix, and a chiral smectic liquid crystal disposed between the scanning electrodes and the data electrodes so as to form a pixel at each intersection of the scanning electrodes and the data electrodes, said chiral smectic liquid crystal switching from a first orientation state to a second orientation state by application of a voltage exceeding one threshold and switching from the second orientation state to the first orientation state by application of a voltage exceeding another threshold, and

(b) voltage application means for

sequentially applying a scanning selection signal to the scanning electrodes to effect one vertical scanning, said scanning selection signal having a voltage of one polarity of a voltage of the other polarity with reference to a voltage level of a scanning electrode not receiving the scanning selection signal, and

applying to the data electrodes data signals in synchronism with the scanning selection signal and a DC voltage which has a polarity alternating in a period synchronized with said one vertical scanning period,

thereby to apply a voltage signal causing a switching from the first orientation state to the second orientation state or a switching from the second orientation state to the first orientation state to pixels at intersections of a scanning electrode receiving the scanning selection signal and the data electrodes, and to apply to intersections of scanning electrodes not receiving the scanning selection signal and the data electrodes a voltage signal which does not exceed either said one or another threshold.

27. A liquid crystal apparatus, comprising:

(a) a liquid crystal device comprising scanning electrodes and data electrodes intersecting the scanning electrodes so as to form an electrode matrix, and a liquid crystal disposed between the scanning electrodes and the data electrodes so as to form a pixel at each intersection of the scanning electrodes and the data electrodes, said liquid crystal having a memory characteristic of switching from a first optical state to a second optical state by application of a voltage exceeding one threshold and switching from the second optical state to the first optical state by application of a voltage exceeding another threshold, and

(b) voltage application means for

sequentially applying a scanning selection signal to the scanning electrodes to effect one vertical scanning, said scanning selection signal having a voltage of one polarity or a voltage of the other polarity with reference to a voltage level of a scanning electrode not receiving the scanning selection signal, and

applying to the data electrodes data signals in synchronism with the scanning selection signal and a DC voltage which has a polarity alternating in a period synchronized with said one vertical scanning period,

thereby to apply a voltage signal causing a switching from the first optical state to the second optical state or a switching from the second optical state to the first optical state to pixels at intersections of a scanning electrode receiving the scanning selection signal and the data electrodes, and to apply to intersections of scanning electrodes not receiving the scanning selection signal and the data electrodes a voltage signal which does not exceed either said one or another threshold.