DRIVING METHOD OF LIQUID CRYSTAL DISPLAY DEVICE

• US 20110175883A1
• Filed: 01/13/2011
• Published: 07/21/2011
• Est. Priority Date: 01/20/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: TOYOTAKA, Kouhei, KUSUNOKI, Koji
• Granted Patent: US 9,214,121 B2
• Time in Patent Office: Days
• US Class Current: 345/211
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/027 Arrangements or methods related to powering off a display
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

It is an object to provide a liquid crystal display device and a driving method of a liquid crystal display device in each of which deterioration of an image display function can be suppressed and power consumption can be sufficiently reduced. In the liquid crystal display device, a fixed potential is input to a capacitor before a power source is turned off, so that a potential difference between electrodes of the capacitor disappears (capacitance becomes almost zero) such that electric field is not applied to liquid crystals, whereby the liquid crystals are in an initial state. When the supply of the power source is stopped after an initial-state image is displayed, unnecessary electric field is not continuously applied to the liquid crystals in an off state, whereby the liquid crystals can be in the stable initial state; therefore, the liquid crystals can be prevented from deteriorating.

Claims

1. A driving method of a liquid crystal display device, comprising the steps of:

displaying an image on a screen provided with pixels each including a capacitor, a liquid crystal element, and a semiconductor element by supplying a power source potential from a power source so that liquid crystals of the liquid crystal element responds;

supplying a stop signal by a stop unit;

writing a fixed potential to the capacitor in each of the pixels in accordance with the stop signal so that a state of the liquid crystals changes from a response state to a non-response state; and

stopping the supply of the power source potential from the power source after writing the fixed potential to the capacitor,

wherein the semiconductor element comprises an oxide semiconductor.

2. The driving method of a liquid crystal display device according to claim 1, wherein an initial-state image is displayed on the screen by writing the fixed potential to the capacitor in each of the pixels.

3. The driving method of a liquid crystal display device according to claim 2,

wherein an all white image is displayed on the screen as the initial-state image.

4. The driving method of a liquid crystal display device according to claim 2,

wherein an all black image is displayed on the screen as the initial-state image.

5. The driving method of a liquid crystal display device according to claim 1, further comprising the step of comparing image signals in successive frame periods with respect to each of the pixels.

6. The driving method of a liquid crystal display device according to claim 1,

wherein a second image signal is not written in a case where a first image signal corresponding to a first frame and the second image signal corresponding to a second frame are the same wherein the first frame and the second frame are successive frames.

7. The driving method of a liquid crystal display device according to claim 1,

wherein the power source potential is supplied to a driver circuit portion in the step of supplying the power source potential from the power source, and

wherein the supply of the power source potential to the driver circuit portion is stopped in the step of stopping the supply of the power source potential from the power source.

8. The driving method of a liquid crystal display device according to claim 1,

wherein the power source potential is supplied to a driver circuit portion and a backlight portion in the step of supplying the power source potential from the power source, and

wherein the supply of the power source potential to the driver circuit portion and the backlight portion is stopped in the step of stopping the supply of the power source potential from the power source.

9. A driving method of a liquid crystal display device, comprising the steps of:

displaying an image on a screen provided with pixels each including a capacitor, a liquid crystal element, and a semiconductor element by supplying a power source potential from a power source so that liquid crystals of the liquid crystal element responds;

supplying a stop signal by a stop unit;

writing a fixed potential to the capacitor in each of the pixels in accordance with the stop signal so that a state of the liquid crystals changes from a response state to a non-response state; and

stopping the supply of the power source potential from the power source after writing the fixed potential to the capacitor.

10. The driving method of a liquid crystal display device according to claim 9,

wherein a transistor including an oxide semiconductor layer is used as the semiconductor element, and

wherein the capacitor and the liquid crystal element are electrically connected in parallel.

11. The driving method of a liquid crystal display device according to claim 9,

wherein an initial-state image is displayed on the screen by writing the fixed potential to the capacitor in each of the pixels.

12. The driving method of a liquid crystal display device according to claim 11,

wherein an all white image is displayed on the screen as the initial-state image.

13. The driving method of a liquid crystal display device according to claim 11,

wherein an all black image is displayed on the screen as the initial-state image.

14. The driving method of a liquid crystal display device according to claim 9, further comprising the step of comparing image signals in successive frame periods with respect to each of the pixels.

15. The driving method of a liquid crystal display device according to claim 9,

wherein a second image signal is not written in a case where a first image signal corresponding to a first frame and the second image signal corresponding to a second frame are the same wherein the first frame and the second frame are successive frames.

16. The driving method of a liquid crystal display device according to claim 9,

wherein the power source potential is supplied to a driver circuit portion in the step of supplying the power source potential from the power source, and

wherein the supply of the power source potential to the driver circuit portion is stopped in the step of stopping the supply of the power source potential from the power source.

17. The driving method of a liquid crystal display device according to claim 9,

wherein the power source potential is supplied to a driver circuit portion and a backlight portion in the step of supplying the power source potential from the power source, and

wherein the supply of the power source potential to the driver circuit portion and the backlight portion is stopped in the step of stopping the supply of the power source potential from the power source.

18. A driving method of a liquid crystal display device, comprising the steps of:

displaying an image on a screen provided with pixels each including a capacitor, a liquid crystal element, and a semiconductor element by supplying a power source potential from a power source so that liquid crystals of the liquid crystal element responds;

supplying a stop signal by a stop unit;

writing a fixed potential to the capacitor in each of the pixels in accordance with the stop signal so that a state of the liquid crystals changes from a response state to a non-response state; and

stopping the supply of the power source potential from the power source after writing the fixed potential to the capacitor,

wherein the liquid crystal element comprises a nematic liquid crystal.

19. The driving method of a liquid crystal display device according to claim 18,

wherein the semiconductor element comprises an oxide semiconductor layer.

20. The driving method of a liquid crystal display device according to claim 18,

wherein a transistor including an oxide semiconductor layer is used as the semiconductor element.

21. The driving method of a liquid crystal display device according to claim 18,

wherein an initial-state image is displayed on the screen by writing the fixed potential to the capacitor in each of the pixels.

22. The driving method of a liquid crystal display device according to claim 21,

wherein an all white image is displayed on the screen as the initial-state image.

23. The driving method of a liquid crystal display device according to claim 21,

wherein an all black image is displayed on the screen as the initial-state image.

24. The driving method of a liquid crystal display device according to claim 18, further comprising the step of comparing image signals in successive frame periods with respect to each of the pixels.

25. The driving method of a liquid crystal display device according to claim 18,

wherein a second image signal is not written in a case where a first image signal corresponding to a first frame and the second image signal corresponding to a second frame are the same wherein the first frame and the second frame are successive frames.

26. The driving method of a liquid crystal display device according to claim 18,

wherein the power source potential is supplied to a driver circuit portion in the step of supplying the power source potential from the power source, and

wherein the supply of the power source potential to the driver circuit portion is stopped in the step of stopping the supply of the power source potential from the power source.

27. The driving method of a liquid crystal display device according to claim 18,

wherein the power source potential is supplied to a driver circuit portion and a backlight portion in the step of supplying the power source potential from the power source, and

wherein the supply of the power source potential to the driver circuit portion and the backlight portion is stopped in the step of stopping the supply of the power source potential from the power source.

28. A driving method of a liquid crystal display device, comprising the steps of:

displaying an image on a screen provided with pixels each including a capacitor, a liquid crystal element, and a semiconductor element by supplying a power source potential from a power source to a driver circuit portion and a backlight portion so that liquid crystals of the liquid crystal element responds;

supplying a stop signal by a stop unit;

stopping the supply of the power source potential from the power source to the backlight portion;

writing a fixed potential to the capacitor in each of the pixels in accordance with the stop signal so that a state of the liquid crystals changes from a response state to a non-response state; and

stopping the supply of the power source potential from the power source to the driver circuit portion after wiring the fixed potential to the capacitor.

29. The driving method of a liquid crystal display device according to claim 28,

wherein the semiconductor element comprises an oxide semiconductor layer.

30. The driving method of a liquid crystal display device according to claim 28,

wherein a transistor including an oxide semiconductor layer is used as the semiconductor element.

31. The driving method of a liquid crystal display device according to claim 28,

wherein an initial-state image is displayed on the screen by writing the fixed potential to the capacitor in each of the pixels.

32. The driving method of a liquid crystal display device according to claim 31,

wherein an all white image is displayed on the screen as the initial-state image.

33. The driving method of a liquid crystal display device according to claim 31,

wherein an all black image is displayed on the screen as the initial-state image

34. The driving method of a liquid crystal display device according to claim 28, further comprising the step of comparing image signals in successive frame periods with respect to each of the pixels.

35. The driving method of a liquid crystal display device according to claim 28,

wherein a second image signal is not written in a case where a first image signal corresponding to a first frame and the second image signal corresponding to a second frame are the same wherein the first frame and the second frame are successive frames.