LIQUID CRYSTAL DISPLAY DEVICE AND ELECTRONIC APPLIANCE

• US 20110267381A1
• Filed: 04/26/2011
• Published: 11/03/2011
• Est. Priority Date: 04/28/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun, Yamazaki, Shunpei
• Granted Patent: US 9,019,320 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• 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 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• 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 2340/06 Colour space transformation
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 2380/14 Electronic books and readers
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO

Abstract

An object is to provide a display device that achieves low power consumption and an improved quality of moving and still images. A display device comprises: a display panel provided with a plurality of pixels each including sub-pixels with color filters of red, green, and blue, and a sub-pixel for controlling a transmission of white light; a backlight area including light sources of red, green, blue, and white; an image switch circuit that switches the display panel between a moving image mode and a still image mode; and a display control circuit that controls in the moving image mode a luminance of the light sources of red, green, and blue included in the backlight area, and controls in the still image mode a luminance of a light source of white included in the backlight area.

Claims

1. A display device comprising:

a first color light source and a second color light source;

pixels configured to control transmission of light emitted by the first color light source and the second color light source, and comprising a first sub-pixel with a color filter and a second sub-pixel configured to control only intensity of transmitted light;

a display switch circuit configured to switch the display device between a moving image mode and a still image mode; and

a display control circuit configured to control light transmittance of the pixels, luminance of the first color light source in the moving image mode, and luminance of the second color light source in the still image mode, in accordance with an image signal.

2. A display device according to claim 1,

wherein the pixels include liquid crystals.

3. A display device according to claim 1,

wherein the first color light source is one of a red light source, a green light source and a blue light source;

and

wherein the second color light source is one of a white light source and a yellow light source.

4. A display device according to claim 1, the display control circuit further comprising:

an image signal converter circuit configured to convert the image signal to a second image signal to be input to the first sub-pixel and to the second sub-pixel;

a moving image display control circuit configured to control light transmittance of the pixels and luminance of the first color light source in the moving image mode, in accordance with the second image signal; and

a still image display control circuit configured to control light transmittance of the pixels and luminance of the second color light source in the still image mode, in accordance with the second image signal.

5. A display device according to claim 4, the display control circuit further comprising:

a moving image timing signal generator circuit configured to control the pixels so that the pixels can display an image based on the second image signal in the moving image mode by using a plurality of write periods; and

a still image timing signal generator circuit configured to control the pixels so that the pixels can display an image in the still image mode by using write periods and holding periods.

6. A display device according to claim 5,

wherein the holding periods last for one minute or more.

7. A display device according to claim 1, the display switch circuit further comprising:

a memory circuit configured to store successive image signals; and

a comparator circuit configured to judge whether the successive image signals are to display a moving image or a still image.

8. A display device according to claim 1, further comprising:

an external switch unit configured to switch the display device between the moving image mode and the still image mode.

9. A display device according to claim 1, further comprising a signal line driver circuit and a scan line driver circuit,

wherein the display device is configured to stop operation of the signal line driver circuit and the scan line driver circuit during a holding period.

10. A display device according to claim 1,

wherein the first sub-pixel and the second sub-pixel each include an oxide semiconductor layer.

11. A display device according to claim 1, wherein the first color light source and the second color light source are light-emitting diodes.

12. An electronic appliance including the display device according to claim 1.

13. A liquid crystal display device comprising:

a backlight area including first light sources of red light, green light and blue light, and second light sources of one of white light and yellow light;

a display panel provided with pixels configured to control transmission of light emitted by the first light sources and the second light sources, and comprising a first sub-pixel with a red color filter, a second sub-pixel with a green color filter, a third sub-pixel with a blue color filter and a fourth sub-pixel configured to control only intensity of transmitted light;

a display switch circuit configured to switch the display panel between a moving image mode and a still image mode; and

a display control circuit configured to control light transmittance of the pixels, luminance of the first light sources in the moving image mode, and luminance of the second light sources in the still image mode, in accordance with an image signal.

14. A liquid crystal display device according to claim 13,

wherein the pixels include liquid crystals.

15. A liquid crystal display device according to claim 13, the display control circuit further comprising:

an image signal converter circuit configured to convert the image signal to a second image signal to be input to the first to fourth sub-pixels;

a moving image display control circuit configured to control light transmittance of the pixels and luminance of the first light sources in the moving image mode, in accordance with the second image signal; and

a still image display control circuit configured to control light transmittance of the pixels and luminance of the second light sources in the still image mode, in accordance with the second image signal.

16. A liquid crystal display device according to claim 15, the display control circuit further comprising:

a moving image timing signal generator circuit configured to control the pixels so that the pixels can display an image based on the second image signal in the moving image mode by using a plurality of write periods; and

a still image timing signal generator circuit configured to control the pixels so that the pixels can display an image in the still image mode by using write periods and holding periods.

17. A liquid crystal display device according to claim 16,

wherein the holding periods last for one minute or more.

18. A liquid crystal display device according to claim 13, the display switch circuit further comprising:

a memory circuit configured to store successive image signals; and

a comparator circuit configured to judge whether the successive image signals are to display a moving image or a still image.

19. A liquid crystal display device according to claim 13, further comprising:

an external switch unit configured to switch the liquid crystal display device between the moving image mode and the still image mode.

20. A liquid crystal display device according to claim 13, further comprising a signal line driver circuit and a scan line driver circuit;

wherein the liquid crystal display device is configured to stop operation of the signal line driver circuit and the scan line driver circuit during a holding period.

21. A liquid crystal display device according to claim 13,

wherein the first to fourth sub-pixels each include an oxide semiconductor layer.

22. A liquid crystal display device according to claim 13, wherein the first light sources and the second light sources are light-emitting diodes.

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

24. A display device comprising:

a display panel comprising pixels configured to control light transmission;

a display control switch circuit;

a moving image display control circuit electrically connected to the display panel; and

a still image display control circuit electrically connected to the display panel,

wherein the display control switch circuit is configured to input a first signal into one of the moving image display control circuit and the still image display control circuit, in accordance with a second signal.

25. A display device according to claim 24, further comprising:

a display switch circuit configured so that the first signal and the second signal originate from the display switch circuit, and electrically connected to the display control switch circuit.

26. A display device according to claim 24, further comprising:

a backlight area comprising a first color light source and a second color light source; and

a first sub-pixel with a color filter and a second sub-pixel configured to control only intensity of transmitted light in the pixels,

wherein the moving image display control circuit and the still image display control circuit are electrically connected to the backlight area.

27. A display device according to claim 24,

wherein the pixels include liquid crystals.

28. A display device according to claim 26,

wherein the first color light source is one of a red light source, a green light source and a blue light source;

and

wherein the second color light source is one of a white light source and a yellow light source.

29. A display device according to claim 25, the display switch circuit further comprising:

a memory circuit configured to store successive image signals; and

a comparator circuit configured to compare the successive image signals.

30. A display device according to claim 24, further comprising:

an external switch unit configured to switch the display device between a moving image mode and a still image mode.

31. A display device according to claim 24, further comprising a signal line driver circuit and a scan line driver circuit,

wherein the display device is configured to stop operation of the signal line driver circuit and the scan line driver circuit during a holding period.

32. A display device according to claim 24,

wherein the pixels each include an oxide semiconductor layer.

33. A display device according to claim 26, wherein the first color light source and the second color light source are light-emitting diodes.

34. An electronic appliance including the display device according to claim 24.