Liquid crystal display device, driving method of the same, and electronic device using the same

• US 20070279374A1
• Filed: 05/22/2007
• Published: 12/06/2007
• Est. Priority Date: 06/02/2006
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime, Umezaki, Atsushi, Yamazaki, Shunpei
• Granted Patent: US 8,154,493 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/133555 Transflectors
• 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 2300/0456 with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
• CPC Class Codes: G09G 2300/0491 Use of a bi-refringent liquid crystal, optically controlled bi-refringence [OCB] with bend and splay states, or electrically controlled bi-refringence [ECB] for controlling the color
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• 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 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

It is an object to provide a display module which can display a correct gray scale by a field sequential driving method and an electronic device including the display module. One frame period is divided into a plurality of lighting periods, and in each of the plurality of lighting periods, signals are supplied to a pixel a plurality of times, whereby the transmissivity of a liquid crystal element is changed over time. Accordingly, even with the use of a liquid crystal element with low response speed as a display element, a correct gray scale can be expressed. In addition, the transmissivity of the liquid crystal element is set at 0% or a backlight is controlled not to emit light in switching of lighting of a backlight or switching of lighting periods, whereby a more correct gray scale can be expressed.

Claims

1. A method for driving a liquid crystal display device which comprises a plurality of pixels arranged in a matrix, a source driver, a gate driver, and a backlight, the method comprising:

scanning the plurality of pixels a plurality of times and supplying digital signals into the scanned plurality of pixels a plurality of times in each of a plurality of lighting periods of one frame period,

wherein a wavelength of light of the backlight is changed in each of the plurality of lighting periods.

2. A liquid crystal display device using the method for driving a liquid crystal display device according to claim 1.

3. A liquid crystal display device according to claim 2, wherein a plurality of red light-emitting diodes, a plurality of green light-emitting diodes, and a plurality of blue light-emitting diodes are used as the backlight.

4. A liquid crystal display device according to claim 2, wherein each of the plurality of pixels includes a reflective region and a transmissive region, and a color filter is provided in the reflective region.

5. An electronic device using the liquid crystal display device according to claim 2.

6. A method for driving a liquid crystal display device according to claim 1, wherein the digital signals are ternary signals.

7. A method for driving a liquid crystal display device which comprises a plurality of pixels arranged in a matrix, a source driver, a gate driver, and a backlight, the method comprising:

scanning the plurality of pixels a plurality of times and supplying digital signals into the scanned plurality of pixels a plurality of times in each of a plurality of lighting periods of one frame period,

wherein a wavelength of light of the backlight is changed in each of the plurality of lighting periods, and

wherein the backlight emits no light when the plurality of pixels are scanned and emits light when the plurality of pixels are not scanned.

8. A liquid crystal display device using the method for driving a liquid crystal display device according to claim 7.

9. A liquid crystal display device according to claim 8, wherein a plurality of red light-emitting diodes, a plurality of green light-emitting diodes, and a plurality of blue light-emitting diodes are used as the backlight.

10. A liquid crystal display device according to claim 8, wherein each of the plurality of pixels includes a reflective region and a transmissive region, and a color filter is provided in the reflective region.

11. An electronic device using the liquid crystal display device according to claim 8.

12. A method for driving a liquid crystal display device according to claim 7, wherein the digital signals are ternary signals.

13. A method for driving a liquid crystal display device which comprises a plurality of pixels arranged in a matrix, a source driver, a gate driver, and a backlight, the method comprising:

scanning the plurality of pixels a plurality of times and supplying digital signals into the scanned plurality of pixels a plurality of times in each of a plurality of lighting periods of one frame period,

wherein a wavelength of light of the backlight is changed in each of the plurality of lighting periods, and

wherein signals having a value which turn the plurality of pixels into a non-emission state are supplied to the plurality of pixels at an end of scanning in each of the plurality of lighting period.

14. A liquid crystal display device using the method for driving a liquid crystal display device according to claim 13.

15. A liquid crystal display device according to claim 14, wherein a plurality of red light-emitting diodes, a plurality of green light-emitting diodes, and a plurality of blue light-emitting diodes are used as the backlight.

16. A liquid crystal display device according to claim 14, wherein each of the plurality of pixels includes a reflective region and a transmissive region, and a color filter is provided in the reflective region.

17. An electronic device using the liquid crystal display device according to claim 14.

18. A method for driving a liquid crystal display device according to claim 13, wherein the digital signals are ternary signals.

19. A method for driving a liquid crystal display device which comprises a plurality of pixels arranged in a matrix, a source driver, a gate driver, and a backlight, the method comprising:

scanning the plurality of pixels a plurality of times and supplying digital signals into the scanned plurality of pixels a plurality of times in each of a plurality of lighting periods of one frame period,

wherein a wavelength of light of the backlight is changed in each of the plurality of lighting periods, and

wherein no light enters a pixel to which one of the digital signals is supplied from the source driver at a beginning of the lighting period.

20. A liquid crystal display device using the method for driving a liquid crystal display device according to claim 19.

21. A liquid crystal display device according to claim 20, wherein a plurality of red light-emitting diodes, a plurality of green light-emitting diodes, and a plurality of blue light-emitting diodes are used as the backlight.

22. A liquid crystal display device according to claim 20, wherein each of the plurality of pixels includes a reflective region and a transmissive region, and a color filter is provided in the reflective region.

23. An electronic device using the liquid crystal display device according to claim 20.

24. A method for driving a liquid crystal display device according to claim 19, wherein the digital signals are ternary signals.