Liquid crystal display device and driving method thereof

• US 20040252097A1
• Filed: 06/10/2004
• Published: 12/16/2004
• Est. Priority Date: 06/10/2003
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Hitachi Displays Limited (Japan Display Incorporated)
• Inventors: Maehara, Mutsumi, Kaneki, Takeshi
• Granted Patent: US 7,256,763 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• 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 2310/062 Waveforms for resetting a plurality of scan lines at a time
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• 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

In a liquid crystal display and a method of driving the same, the liquid crystal display includes: a liquid crystal display panel having a matrix of a plurality of pixels arrayed two dimensionally in a first direction and in a second direction crossing the first direction; and an illuminating device including a plurality of light sources facing the pixel matrix of the liquid crystal display panel. The plurality of light sources are arrayed in the first direction and grouped into a plurality of light source areas. The turn-on start timing of light sources in each light source area is set to a specific timing based on the input timing of the video signal to the selected pixel rows in the pixel matrix. Further, the turn-on and turn-off timings of the light source areas are set to specific conditions.

Claims

1. A method of driving a liquid crystal display, wherein the liquid crystal display comprises a liquid crystal display panel and an illuminating device;

wherein the liquid crystal display panel has a matrix of a plurality of pixels arrayed two-dimensionally in a first direction and in a second direction crossing the first direction, and in the pixel matrix a plurality of pixel rows each made up of a group of pixels lined in the second direction are arrayed in the first direction and sequentially selected in each frame period from one end of the pixel matrix to the other end;

wherein the illuminating device has a plurality of light sources facing the pixel matrix of the liquid crystal display panel and the plurality of light sources are arrayed in the first direction and divided into at least three light source areas facing at least three groups of pixel rows;

wherein turn-on periods of the light source areas sequentially start in the each frame period when one of the at least three groups of pixel rows corresponding to the at least three light source areas is selected and the plurality of pixels belonging to the selected group of pixel rows begin to receive video signals;

wherein the turn-on periods of the light source areas sequentially ends in the each frame period;

wherein the at least three light source areas are a first light source area, a second light source area and a third light source area,

the first light source area facing a middle area, with respect to the first direction, of the pixel matrix where a first group of the pixel rows is situated,

the second light source area facing an area of the pixel matrix adjoining the middle area in the first direction where a second group of the pixel rows is situated which is selected before the first group of the pixel rows in the each frame period,

the third light source area facing another area of the pixel matrix adjoining the middle area in the first direction where a third group of the pixel rows is situated which is selected after the first group of the pixel rows in the each frame period;

wherein the turn-on period of the second light source area, the turn-on period of the first light source area and the turn-on period of the third light source area are sequentially start and end in that order;

wherein the turn-on period of the second light source area ends after the turn-on period of the first light source area has started;

wherein the turn-on period of the third light source area starts after the turn-on period of the first light source area has started and when or before the turn-on period of the second light source area ends.

2. A liquid crystal display driving method according to claim 1, wherein a start time of the turn-on period of the third light source area coincides with an end time of the turn-on period of the second light source area.

3. A liquid crystal display driving method according to claim 1, wherein the turn-on periods of the first light source area, the second light source area and the third light source area in the frame period are equal.

4. A liquid crystal display driving method according to claim 1, wherein one of the turn-on periods of the first light source area, the second light source area and the third light source area in the frame period differs from at least one of the others.

5. A liquid crystal display driving method according to claim 4, wherein the turn-on periods of the first light source area, the second light source area and the third light source area in the frame period differ from each other.

6. A liquid crystal display driving method according to claim 1, wherein each of the plurality of light sources is a tube-like light source extending in the second direction and the illuminating device comprises the tube-like light sources arrayed in the first direction.

7. A liquid crystal display driving method according to claim 6, wherein a plurality of the tube-like light sources are arrayed in the first direction in at least one of the first light source area, the second light source area and the third light source area.

8. A liquid crystal display driving method according to claim 1, wherein the plurality of pixels belonging to the first group of pixel rows, the plurality of pixels belonging to the second group of pixel rows and the plurality of pixels belonging to the third group of pixel rows oppose the first light source area, the second light source area and the third light source area, respectively.

9. A liquid crystal display driving method according to claim 1, wherein the first light source area, the second light source area and the third light source area are arrayed in that order from the one end of the pixel matrix to the other end.

10. A liquid crystal display driving method according to claim 1, wherein in the frame period the plurality of pixel rows, after having received the video signals, are selected again to have brightness reducing voltage signals supplied to the plurality of pixels belonging to the re-selected pixel rows.

11. A liquid crystal display driving method according to claim 10, wherein the voltage signals display in black the plurality of pixels belonging to the re-selected pixel rows.

12. A liquid crystal display driving method according to claim 1, wherein a period from a point in time at which the video signals begin to be taken into the second group of pixel rows to a point in time at which the turn-on period of the second light source area begins differs from a period from a point in time at which the video signals begin to be taken into the first group of pixel rows to a point in time at which the turn-on period of the first light source area begins.

13. A liquid crystal display driving method according to claim 1, wherein a period from a point in time at which the video signals begin to be taken into the third group of pixel rows to a point in time at which the turn-on period of the third light source area begins differs from a period from a point in time at which the video signals begin to be taken into the first group of pixel rows to a point in time at which the turn-on period of the first light source area begins.

14. A method of driving a liquid crystal display, wherein the liquid crystal display comprises:

a liquid crystal display panel having a matrix of a plurality of pixels arrayed two-dimensionally in a first direction and in a second direction crossing the first direction;

a plurality of pixel rows each made up of a group of the pixels lined in the second direction, the pixel rows being arrayed in the first direction in the pixel matrix and sequentially selected in each frame period from one end of the pixel matrix to the other end; and

an illuminating device having a plurality of light sources facing the pixel matrix of the liquid crystal display panel, the plurality of light sources being arrayed in the first direction and divided into at least three light source areas facing at least three groups of pixel rows;

the liquid crystal display driving method repeating in each frame period the steps of;

sequentially starting turn-on periods of the light source areas when one of the at least three groups of pixel rows corresponding to the at least three light source areas is selected and the plurality of pixels belonging to the selected group of pixel rows begin to receive video signals;

after the turn-on periods of the at least three light source areas corresponding to the at least three groups of pixel rows have started, sequentially selecting again one of the at least three groups of pixel rows to put blanking signals for blanking the video signals into the re-selected group of pixel rows; and

ending the turn-on periods of the at least three light source areas after one of the at least three groups of pixel rows has started to receive the blanking signals;

wherein the at least three light source areas are divided into

(i) a first light source area facing a middle area, with respect to the first direction, of the pixel matrix where a first group of the pixel rows is situated,

(ii) a second light source area facing an area of the pixel matrix adjoining the middle area in the first direction where a second group of the pixel rows is situated which receives the video signals before the first group of the pixel rows in the each frame period, and

(iii) a third light source area facing another area of the pixel matrix adjoining the middle area in the first direction where a third group of the pixel rows is situated which receives the video signals after the first group of the pixel rows in the each frame period;

wherein the turn-on period of the second light source area, the turn-on period of the first light source area and the turn-on period of the third light source area sequentially start and end in that order;

wherein the turn-on period of the second light source area ends after the turn-on period of the first light source area has started;

wherein the turn-on period of the third light source area starts after the turn-on period of the first light source area has started and when or before the turn-on period of the second light source area ends;

wherein, after the turn-on period of the first light source area has ended in the each frame period before the turn-on period of the first light source area starts in a next frame period, at least one of the turn-on periods of the second light source area and the third light source area is suspended.

15. A liquid crystal display comprising:

a liquid crystal display panel having a matrix of a plurality of pixels arrayed two-dimensionally in a first direction and in a second direction crossing the first direction, the pixel matrix having a plurality of pixel rows each made up of a group of pixels lined in the second direction, the pixel rows being arrayed in the first direction and sequentially selected in each frame period from one end of the pixel matrix to the other end;

an illuminating device having a plurality of light sources facing the pixel matrix of the liquid crystal display panel, the plurality of light sources being arrayed in the first direction and divided into at least three light source areas facing at least three groups of pixel rows; and

a control unit including a display control circuit to give video signals to the pixel matrix and a light source driving circuit to control the driving of the plurality of light sources in response to a control signal from the display control circuit;

wherein the control unit executes the following steps of;

sequentially starting in the each frame period turn-on periods of the light source areas when one of the at least three groups of pixel rows corresponding to the at least three light source areas is selected and the plurality of pixels belonging to the selected group of pixel rows begin to receive video signals;

sequentially ending the turn-on periods of the light source areas in the each frame period;

using the at least three light source areas as a first light source area, a second light source area and a third light source area,

the first light source area facing a middle area, with respect to the first direction, of the pixel matrix where a first group of the pixel rows is situated,

the second light source area facing an area of the pixel matrix adjoining the middle area in the first direction where a second group of the pixel rows is situated which is selected before the first group of the pixel rows in the each frame period,

the third light source area facing another area of the pixel matrix adjoining the middle area in the first direction where a third group of the pixel rows is situated which is selected after the first group of the pixel rows in the each frame period;

sequentially starting and ending the turn-on period of the second light source area, the turn-on period of the first light source area and the turn-on period of the third light source area in that order;

ending the turn-on period of the second light source area after the turn-on period of the first light source area has started; and

starting the turn-on period of the third light source area after the turn-on period of the first light source area has started and when or before the turn-on period of the second light source area ends.