Liquid crystal display device and electronic device

• US 8,508,561 B2
• Filed: 04/04/2011
• Issued: 08/13/2013
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei, Koyama, Jun
• Primary Examiner(s): Cheng, Joe H
• Application Number:
  US13/079,035
• Publication Number:
  US 20110249038A1
• Time in Patent Office: 862 Days
• Field of Search: 345/87, 345/88, 345/102, 345/690, 349 61- 65, 340/815.55, 340/815.56
• US Class Current: 345/690
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A liquid crystal display device by which a color moving image displayed with a field sequential system and a monochrome still image are switched and displayed. In a moving-image mode, a driving control circuit controls the backlight portion to emit light corresponding to any one of a plurality of colors of the first light source, and controls the display panel by writing of the image signal in the display panel for each of the plurality of colors within a predetermined period. In a still-image mode, the driving control circuit controls the backlight portion to keep the second light source emitting light, and controls the display panel to hold the image signal written thereto, for a predetermined period.

Claims

1. A liquid crystal display device comprising:

a display panel;

a backlight portion including a first light source for emitting light of a plurality of colors and a second light source for emitting white light;

an image switching circuit configured to determine whether display is performed in a moving-image mode or a still-image mode in accordance with an image signal from the outside of the liquid crystal display device; and

a driving control circuit configured to control the backlight portion and the display panel,

wherein in the moving-image mode, the driving control circuit controls the backlight portion to emit light from the first light source and to switch a color of the light corresponding to any one of the plurality of colors per a predetermined period and controls the display panel by writing the image signal for each of the plurality of colors per the predetermined period, so that a color image is perceived with a mixed color of the plurality of colors of the first light source, and

wherein in the still-image mode, the driving control circuit controls the backlight portion to keep the second light source emitting light and controls the display panel to hold the image signal written thereto, for a predetermined period, so that a monochrome image is perceived.

2. The liquid crystal display device according to claim 1,

wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes a light source emitting white light.

3. The liquid crystal display device according to claim 1,

wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes the light source emitting blue light and a light source emitting yellow light.

4. The liquid crystal display device according to claim 1, wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes a light source emitting cyan light and the light source emitting red light or a light source emitting magenta light and the light source emitting green light.

5. The liquid crystal display device according to claim 1, wherein the first light source and the second light source comprise light-emitting diodes.

6. An electronic device including the liquid crystal display device according to claim 1.

7. A liquid crystal display device comprising:

a display panel including a plurality of pixels each including a pixel electrode for controlling alignment of liquid crystal, and a transistor connected to the pixel electrode,

a backlight portion including a first light source for emitting light of a plurality of colors and a second light source for emitting white light;

an image switching circuit configured to determine whether display is performed in a moving-image mode or a still-image mode in accordance with an image signal from the outside of the liquid crystal display device; and

a driving control circuit configured to control the backlight portion and the display panel,

wherein in the moving-image mode, the driving control circuit controls the backlight portion to emit light from the first light source and to switch a color of the light corresponding to any one of the plurality of colors per a predetermined period and controls the display panel by writing the image signal for each of the plurality of colors per the predetermined period, so that a color image is perceived with a mixed color of the plurality of colors of the first light source, and

wherein in the still-image mode, the driving control circuit controls the backlight portion to keep the second light source to emit light and controls the display panel to hold the image signal written thereto, for a predetermined period, so that a monochrome image is perceived.

8. The liquid crystal display device according to claim 7, wherein the transistor includes an oxide semiconductor layer.

9. The liquid crystal display device according to claim 7,

wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes a light source emitting white light.

10. The liquid crystal display device according to claim 7,

wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes the light source emitting blue light and a light source emitting yellow light.

11. The liquid crystal display device according to claim 7, wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes a light source emitting cyan light and the light source emitting red light or a light source emitting magenta light and the light source emitting green light.

12. The liquid crystal display device according to claim 7, wherein the first light source and the second light source comprise light-emitting diodes.

13. An electronic device including the liquid crystal display device according to claim 7.

14. A liquid crystal display device comprising:

a display panel, the display panel comprising;

a plurality of pixels, each including a transistor and a pixel electrode; and

a driver circuit configured to drive the plurality of pixels,

a backlight portion, the backlight portion comprising;

a first light source for emitting light of a plurality of colors;

a second light source for emitting white light; and

a backlight control circuit configured to drive the first light source and the second light source,

an image switching circuit, the image switching circuit comprising;

a memory circuit configured to store image signals;

a comparison circuit configured to detect a difference among the image signals of successive frame periods stored in the memory circuit;

a selection circuit configured to select and output the image signals of the successive frame periods in accordance with the difference detected in the comparison circuit; and

a display control circuit configured to output the image signals output from the selection circuit and a first signal; and

a driving control circuit configured to control the display panel and the backlight portion in accordance with the first signal,

wherein the driving control circuit controls the backlight control circuit so that the first light source emits light by the light of the plurality of colors sequentially, in case the comparison circuit detects the difference, and

wherein the driving control circuit controls the backlight control circuit so that the second light source emits the white light in case the comparison circuit does not detect the difference.

15. The liquid crystal display device according to claim 14, wherein the transistor includes an oxide semiconductor layer.

16. The liquid crystal display device according to claim 14,

wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes a light source emitting white light.

17. The liquid crystal display device according to claim 14,

wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes the light source emitting blue light and a light source emitting yellow light.

18. The liquid crystal display device according to claim 14, wherein the first light source includes a light source emitting red light, a light source emitting green light, and a light source emitting blue light, and the second light source includes a light source emitting cyan light and the light source emitting red light or a light source emitting magenta light and the light source emitting green light.

19. The liquid crystal display device according to claim 14, wherein the first light source and the second light source comprise light-emitting diodes.

20. An electronic device including the liquid crystal display device according to claim 14.

21. A liquid crystal display device comprising:

a display panel, the display panel comprising;

a plurality of pixels, each including a transistor and a pixel electrode; and

a driver circuit configured to drive the plurality of pixels,

a backlight portion, the backlight portion comprising;

a first light source for emitting light of a first color;

a second light source for emitting light of a second color;

a third light source for emitting light of a third color;

a fourth light source for emitting light of a fourth color; and

a backlight control circuit configured to drive the first light source, the second light source, the third light source and the fourth light source,

an image switching circuit, the image switching circuit comprising;

a memory circuit configured to store image signals;

a comparison circuit configured to detect a difference among the image signals of successive frame periods stored in the memory circuit;

a selection circuit configured to select and output the image signals of the successive frame periods in accordance with the difference detected in the comparison circuit; and

a display control circuit configured to output a signal and the image signals output from the selection circuit; and

a driving control circuit configured to control the display panel and the backlight portion in accordance with the signal from the display control circuit,

wherein the driving control circuit controls the backlight control circuit so that the first light source, the second light source and the third light source are sequentially lit, in case the comparison circuit detects the difference, and

wherein the driving control circuit controls the backlight control circuit so that the fourth light source and any one of the first light source, the second light source and the third light source are lit at the same time, in case the comparison circuit does not detect the difference.

22. The liquid crystal display device according to claim 21,

wherein the transistor includes an oxide semiconductor layer.

23. The liquid crystal display device according to claim 21,

wherein the fourth color is a complementary color of any one of the first color, the second color, and the third color.

24. The liquid crystal display device according to claim 21,

wherein the first color is red, the second color is green and the third color is blue, and

wherein the fourth color is any one of cyan, magenta and yellow.