Method and apparatus for driving liquid crystal display having memory effect

• US 5,583,534 A
• Filed: 02/16/1994
• Issued: 12/10/1996
• Est. Priority Date: 02/18/1993
• Status: Expired due to Fees

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Tsuboyama, Akira, Katakura, Kazunori
• Primary Examiner(s): Tung, Kee Mei
• Assistant Examiner(s): CHOW, DOON Y
• Application Number:
  US08/197,319
• Time in Patent Office: 1,028 Days
• Field of Search: 345/98, 345/87, 345/94, 345/87, 345/95, 345/97, 345/88, 348/790, 348/792, 348/793, 359/54, 359/55, 359/56
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/0227 related to multiple interlacing, i.e. involving more fields than just one odd field and one even field
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

There are method and apparatus for driving a liquid crystal display apparatus which has a liquid crystal and electrodes arranged in a matrix form and in which a number of pixels having a memory effect are provided. Image information is displayed by a refresh scanning by using the liquid crystal display apparatus and is displayed by a non-refresh scanning without substantially changing the image information displayed by the liquid crystal display apparatus. A signal to fluctuate a transmission light amount of the pixel is applied to the electrode during the execution of the display by the non-refresh scanning. A smectic liquid crystal or a ferroelectric liquid crystal is used as a liquid crystal.

Claims

1. A driving method on a display device, said method comprising:

a first step of presenting a display by refresh scanning, on the basis of image information, on a liquid crystal display device which has a liquid crystal and scanning and information electrodes arranged in a matrix form and in which a plurality of pixels having a memory effect are provided; and

a second step of presenting a display by non-refresh scanning without substantially changing the image information,

wherein a non-zero voltage signal to fluctuate a transmission light amount of the plurality of pixels is applied to the information electrodes during said second step, and wherein in the first step a scanning selection signal is successively supplied to the scanning electrodes, and in the second step, the scanning selection signal is not supplied to the scanning electrodes.

12. A driving method according to claim 1, wherein the signal to fluctuate the transmission light amount is an A.C. pulse signal.

13. A driving method according to claim 1,

wherein said refresh scanning provides all scanning electrodes with a reference voltage, and provides all information electrodes with an A.C. pulse signal.

2. An apparatus for driving a display device, comprising:

refresh scanning means for refresh scanning to present a display of image information on a liquid crystal display device which has a liquid crystal and scanning and information electrodes arranged in a matrix form and in which a plurality of pixels having a memory effect are provided; and

non-refresh scanning means for non-refresh scanning to present a display without substantially changing the image information,

wherein said non-refresh scanning means applies a signal to fluctuate a transmission light amount of the plurality of pixels to the information electrodes during the non-refresh scanning operation, wherein the refresh scanning means supplies a scanning selection signal successively to the scanning electrodes, and the non-refresh scanning means does not supply the scanning selection signal to the scanning electrodes.

5. An apparatus according to any one of claims 2 to 4, wherein said liquid crystal is a smectic liquid crystal.

6. An apparatus according to any one of claims 2 to 4, wherein said liquid crystal is a ferroelectric liquid crystal.

7. An apparatus according to any one of claims 2 to 4, wherein each of said plurality of pixels has a transistor.

8. An apparatus according to any one of claims 2 to 4, wherein each of said plurality of pixels has a non-linear device.

9. An apparatus according to any one of claims 2 to 4, wherein an amplitude or pulse width of said signal to fluctuate said transmission amount is time-sequentially decreased.

10. An apparatus according to any one of claims 2 to 4, wherein said signal to fluctuate said transmission light amount is a signal whose amplitude or pulse width is time-sequentially decreased and, after a predetermined period of time, a different signal, whose amplitude or pulse width is time-sequentially increased, is applied to the information electrodes.

11. An apparatus according to any one of claims 2 to 4, wherein said signal to fluctuate said transmission light amount is a signal whose amplitude or pulse width is time-sequentially constant.

14. An apparatus according to any one of claims 2 to 4, wherein the signal to fluctuate the transmission light amount is an A.C. pulse signal.

15. An apparatus according to any one of claims 2 to 4, wherein said refresh scanning provides all scanning electrodes with a reference voltage, and provides all information electrodes with an A.C. pulse signal.

3. An apparatus for driving and controlling a liquid crystal display apparatus, comprising:

display means which has a liquid crystal and scanning and information electrodes arranged in a matrix form and in which a plurality of pixels having a memory effect are provided;

scanning means for scanning the pixels to display image information on said display means; and

selecting means for selecting either one of a refresh scanning mode for refresh scanning to display the image information on the liquid crystal display device and a non-refresh scanning mode for non-refresh scanning to display without substantially changing the image information,

wherein, in the non-refresh scanning mode, said scanning means is controlled so as to supply a signal to fluctuate a transmission light amount of the plurality of pixels from said scanning means to said information electrodes, wherein in the refresh scanning mode a scanning selection signal is successively supplied to the scanning electrodes, and in the non-refresh scanning mode the scanning selection signal is not supplied to the scanning electrodes.

4. An apparatus for displaying, comprising:

liquid crystal display means which has a liquid crystal and scanning and information electrodes arranged in a matrix form and in which a plurality of pixels having a memory effect are provided;

scanning means for scanning said liquid crystal display means to display image information; and

selecting means for selecting either one of a refresh scanning mode for refresh scanning to display the image information and a non-refresh scanning mode for non-refresh scanning to display without substantially changing the image information displayed in said liquid crystal display means,

wherein in said non-refresh scanning mode, said scanning means is controlled so as to supply a signal to fluctuate a transmission light amount of the plurality of pixels from said scanning means to the information electrodes and wherein in the refresh scanning mode a scanning selection signal is successively supplied to the scanning electrodes, and in the non-refresh scanning mode the scanning selection signal is not supplied to the scanning electrodes.

16. A display apparatus comprising:

a liquid crystal display panel in which pixels are constructed by a group of scanning electrodes and a group of information electrodes in a matrix form;

a liquid crystal which is arranged in said liquid crystal display panel and is driven by an electric field applied through said group of scanning electrodes and said group of information electrodes;

an image information storing circuit to store image information to be displayed by said liquid crystal display panel;

a change detection circuit to detect whether the image information stored in said image information storing circuit has changed;

first driving means for applying a scanning signal to said group of scanning electrodes and applying an information signal to said group of information electrodes on the basis of the image information stored in said image information storing circuit; and

second driving means for applying a waveform which produces, on said liquid crystal, a luminance that is almost equal to a luminance produced in a scanning non-selection period by said first driving means to said liquid crystal display panel while maintaining the display state on said display panel by application of the electric field to the group of scanning electrodes and the group of information electrodes in accordance with the result of the detection by said change detection circuit.

17. An apparatus according to claim 16, wherein a ratio between the luminance in said scanning non-selection period of time by said first driving means and the luminance by said second driving means lies within a range from 0.95 to 1.05.

18. An apparatus according to claim 16, wherein said liquid crystal is a ferroelectric liquid crystal.

19. A display apparatus comprising:

a liquid crystal display panel in which pixels are constructed by a group of scanning electrodes and a group of information electrodes in a matrix form, and a liquid crystal, said panel being driven by an electric field which is applied through the group of scanning electrodes and the group of information electrodes;

an image information storing circuit to store image information to be displayed by said liquid crystal display panel;

driving means for applying a scanning signal to the group of scanning electrodes and applying an information signal to the group of information electrodes on the basis of the image information stored in said image information storing circuit;

memory display means for holding display contents on the liquid crystal display panel without applying any voltage to the liquid crystal;

a change detection circuit to detect whether the image information stored in said image information storing circuit has changed; and

a driving control circuit for switching a display mode of said liquid crystal between an ordinary display mode to be executed by said driving means and a memory display mode to be executed by said memory display means and for gradually changing a waveform that is applied to the liquid crystal after a predetermined switching period of time when said display mode is switched wherein, during a time period for gradually changing a waveform, the display contents is not changed.

20. An apparatus according to claim 19, wherein said driving control circuit changes an amplitude of a driving waveform in said switching period of time.

21. An apparatus according to claim 19, wherein said driving control circuit changes a pulse width of a driving waveform in said switching period of time.

22. An apparatus according to claim 19, wherein said liquid crystal is a ferroelectric liquid crystal.

23. A driving device of a display device with a memory effect, comprising:

means for performing one of first and second modes, wherein the first mode comprises successively applying a scanning selection signal to a scanning electrode of the display device and applying an information signal to an information electrode of the display device to perform an image display wherein the image can be rewritten, and the second mode comprises performing the image display using the memory effect without applying the scanning selection signal no the scanning electrode of the display device, wherein rewriting of the image is not performed; and

means for switching the display device between the first and second modes,

wherein, during the second mode, a non-zero voltage of a level which does not cause image rewriting is applied to the information electrode of the display device.

25. A device according to claim 23 or 24, wherein said display device includes a smectic liquid crystal.

26. A device according to claim 23 or 24, wherein said display device includes a ferroelectric liquid crystal.

24. A driving device of a display device with a memory effect, comprising:

means for performing one of first, second and third modes, wherein the first mode comprises successively applying a scanning selection signal to a scanning electrode of the display device and applying an information signal to an information electrode of the display device to perform an image display wherein the image can be rewritten, the second mode comprises performing the image display using the memory effect without applying the scanning selection signal to the scanning electrode of the display device, wherein rewriting of the image is not performed, and the third mode comprises performing the image display using the memory effect without applying the scanning selection signal to the scanning electrode of the display device and without applying the information signal to the information electrode wherein the rewrite of the image is not performed; and

means for switching the device between the first, second and third modes,

wherein a non-zero voltage of a level which does not cause the image rewrite is applied to the information electrode of the display device during the second mode, and no voltage is applied at the intersection between the scanning electrode and the information electrode of the display device during the third mode, and wherein a mode change between the first and third modes are performed by performing the second mode between the first and third modes.