Liquid crystal display

• US 20020196220A1
• Filed: 03/28/2002
• Published: 12/26/2002
• Est. Priority Date: 03/30/2001
• Status: Active Grant

• Current Assignee: Japan Display Central Incorporated (Japan Display Incorporated)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Sato, Ichiro, Yamakita, Hiroyuki, Kumagawa, Katsuhiko, Komori, Kazunori
• Granted Patent: US 7,030,848 B2
• Time in Patent Office: Days
• US Class Current: 345/87
• CPC Class Codes: G09G 2310/0224 Details of interlacing
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0266 Reduction of sub-frame artefacts
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

Disclosed is a liquid crystal display capable of ensuring brightness necessary for achieving satisfactory display by increasing ratio of light-emitting time to one frame period. A liquid crystal display is adapted to have a period (non-video signal write period) required for writing non-video signals different from video signals onto all the pixels before a video signal write period. In the non-video signal write period, the non-video signals are written onto the respective pixels, thereby starting response of the liquid crystal before the start of the video signal write period. In the non-video signal write period, a backlight is turned off, and thereby image degradation is prevented even when the non-video signals are written onto the respective pixels.

Claims

1. A liquid crystal display comprising:

an array substrate having a plurality of gate lines and a plurality of source lines arranged to cross each other, pixel electrodes provided in matrix, and switching devices respectively provided as corresponding to the pixel electrodes, for switching between a conductive state and a non-conductive state between the pixel electrodes and the source lines according to scan signals supplied through the gate lines to allow writing of video signals supplied through the source lines to the pixel electrodes;

an opposing substrate disposed opposite to the array substrate;

a liquid crystal layer disposed between the array substrate and the opposing substrate and containing filled liquid crystal;

a counter electrode provided on one of the opposing substrate and the array substrate, for generating potential difference between the counter electrode and the pixel electrodes, thereby driving the liquid crystal; and

an illuminating device including a light source for emitting lights of a plurality of colors, wherein

one frame period of the video signals is composed of a plurality of sub-frame periods, and

the illuminating device is controlled to emit light of one of the plurality of colors to the liquid crystal layer in each sub-frame period, and predetermined signals are written onto the pixel electrodes in the order of first writing and second writing in at least one sub-frame period, for allowing the video signals associated with the at least one sub-frame period to be supplied to the pixel electrodes to cause the liquid crystal to be driven to thereby allow image corresponding to the video signals to be displayed.

2. The lipid crystal display according to claim 1, wherein non-video signals different from the video signals are written onto at least part of the pixel electrodes in the first writing and the video signals are written onto the respective pixel electrodes in the second writing.

3. The liquid crystal display according to claim 2, wherein the liquid crystal is OCB-mode liquid crystal.

4. The liquid crystal display according to claim 2, wherein the liquid crystal has spontaneous polarization.

5. The liquid crystal display according to claim 2, wherein voltage corresponding to the non-video signals is 0 V or larger and not larger than an intermediate voltage between voltage for white display and voltage for black display.

6. The liquid crystal display according to claim 2, wherein first non-video signals near voltage for black display and second non-video signals near voltage for white display are written to the pixel electrodes in this order in the first writing.

7. The liquid crystal display according to claim 2, wherein the non-video signals are written onto the pixel electrodes associated with all the gate lines substantially at the same timing in the first writing.

8. The liquid crystal display according to claim 2, wherein the plurality of gate lines are divided into a plurality of blocks and scan signals are output to the gate lines of each block substantially at the same timing in the first writing, for allowing the non-video signals to be written onto the pixel electrodes associated with the gate lines of each block substantially at the sane timing.

9. The liquid crystal display according to claim 2, wherein the illuminating device is adapted to emit light from one main surface thereof and have luminance distribution in which luminance decreases according to scan direction in a plane of the main surface.

10. The liquid crystal display according to claim 1, wherein part of image to be displayed is displayed in the sub-frame period by the first writing, and whole image to be displayed is displayed by the first writing and the second writing.

11. The liquid crystal display according to claim 10, wherein the liquid crystal is OCB-mode liquid crystal.

12. The liquid crystal display according to claim 10, wherein the liquid crystal has spontaneous polarization.

13. The liquid crystal display according to claim 10, wherein a video signal to be written onto one of a plurality of adjacent pixel electrodes in the direction in which the gate lines are arranged is written onto the plurality of pixel electrodes in the first writing and video signals are written onto the remaining pixel electrodes of the plurality of pixel electrodes in the second writing.

14. The liquid crystal display according to claim 10, wherein the same signal is written onto a plurality of adjacent pixel electrodes in the direction in which the gate lines are arranged in the first writings and video signals are written onto the plurality of pixels are written in the second writing.

15. The liquid crystal display according to claim 14, wherein the same signal is one of a video signal corresponding to the highest voltage and a video signal corresponding to the lowest voltage of the video signals to be written onto the plurality of pixel electrodes.

16. The liquid crystal display according to claim 14, wherein the same signal is a signal having an average of the video signals to be respectively written onto the plurality of pixel electrodes.

17. The liquid crystal display according to claim 14, wherein the same signal is one of the video signals to be respectively written onto the plurality of pixel electrodes.

18. The liquid crystal display according to claim 14, wherein the same signal is a video signal to be written onto pixel electrodes associated with a gate line on odd row of the plurality of pixel electrodes in one of two continuous sub-frame periods and is a video signal to be written onto pixel electrodes associated with a gate line on even row of the plurality of pixel electrodes in the other sub-frame period.

19. The liquid crystal display according to claim 10, wherein signals corresponding to voltage with the same polarity are written in the first writing and the second writing.

20. The liquid crystal display according to claim 10, wherein signals are sequentially written onto respective pixel electrodes associated with the gate lines in one of predetermined two continuous sub-frame periods in a given order and the signals are written onto the respective pixel electrodes associated with the gate lines in the other sub-frame period in the order which is reverse of the given order.

21. The liquid crystal display according to claim 13, wherein a period during which the scan signals continue to be output to the respective gate lines in the first writing is longer than a period during which the scan signals continue to be output to the respective gate lines in the second writing.

22. The liquid crystal display according to claim 10, wherein white display signals are written onto at least part of the pixel electrodes in the first writing and then a video signal to be written onto one of a plurality of adjacent pixel electrodes in the direction in which the gate lines are arranged are written to the plurality of pixels in the first writing, and video signals are written onto the remaining pixel electrodes of the plurality of pixel electrodes in the second writing.

23. The liquid crystal display according to claim 22, wherein the liquid crystal is OCB-mode liquid crystal.

24. The liquid crystal display according to claim 1, wherein black display signals are written onto part of pixel electrodes and video signals are written onto the remaining pixel electrodes in the first writing, and the video signals are written onto part of the pixel electrodes and the black display signals are written onto the remaining pixel electrodes in the second writing.

25. The liquid crystal display according to claim 24, wherein black display signals are written after the video signals are written in the first writing and the second writing.

26. The liquid crystal display according to claim 24, wherein the black display signals are written onto pixel electrodes associated with a plurality of gate lines substantially at the same timing.

27. The liquid crystal display according to claim 24, wherein the liquid crystal is OCB-mode liquid crystal.

28. The liquid crystal display according to claim 24, wherein the liquid crystal has spontaneous polarization.

29. The liquid crystal display according to claim 24, wherein black is displayed in pixels corresponding to the same gate line over predetermined plural continuous sub-frame periods.

30. The liquid crystal display according to claim 24, wherein the one frame period is composed of sub-frame periods greater in number than colors of light emitted by the light source.

31. The liquid crystal display according to claim 24, wherein the illuminating device is controlled to emit light of different colors in two continuous sub-frame periods.

32. The liquid crystal display according to claim 24, wherein the illuminating device is controlled to allow sub-frame periods of specified one color of the plurality of colors in one frame period to be greater in number than sub-frame periods of the other colors.

33. The liquid crystal display according to claim 24, wherein the number of the gate lines to which the scan signals are supplied in writing of the black display signals is varied according to color of sub-frame periods.

34. The liquid Crystal display according to claim 24, wherein the illuminating device has a light source for emitting light of red, green, and blue, and

the illuminating device is controlled to allow the gate lines to which the scan signals are supplied to be the greatest in number in the sub-frame period of green and to be the least in number in the sub-frame period of blue.

35. The liquid crystal display according to claim 1, wherein the illuminating device has a light source for emitting light of red, green, and blue, and wherein

the illuminating device is controlled to emit one of light of a color of red, green, and blue and light of a combination of at least two colors of red, green, and blue to the liquid crystal layer in each sub-frame period.

36. The liquid crystal display according to claim 1, wherein the illuminating device has a light source for emitting light of at least red, blue, and green, and wherein

the illuminating device is controlled to emit light of one of the colors to the liquid crystal layer in each sub-frame period,

38. The liquid crystal display according to claim 37, wherein the liquid crystal is OCB-mode liquid crystal.

37. A liquid crystal display comprising:

an array substrate having a plurality of gate lines and a plurality of source lines arranged to cross each other, pixel electrodes provided in matrix, switching devices respectively provided as corresponding to the pixel electrodes, for switching between a conductive state and a non-conductive state between the pixel electrodes and the source lines according to scan signals supplied through the gate lines to allow writing of video signals supplied through the source lines to the pixel electrodes, and color filters of red, green and blue;

an opposing substrate disposed opposite to the array substrate;

a liquid crystal layer disposed between the array substrate and the opposing substrate and containing filled liquid crystal;

a counter electrode provided on one of the opposing substrate and the array substrate, for generating potential difference between the counter electrode and the pixel electrodes, thereby driving the liquid crystal; and

an illuminating device including a light source for emitting white light, wherein

the illuminating device is controlled to emit white light to the liquid crystal layer in part of each frame period of the video signals, and predetermined signals are written onto the pixel electrodes in the order of first writing and second writing in each frame period, for allowing the video signals associated with the frame period to be supplied to the pixel electrodes to cause the liquid crystal to be driven to thereby allow image corresponding to the video signals to be displayed.