Method for driving liquid crystal display device

• US 9,852,703 B2
• Filed: 12/22/2010
• Issued: 12/26/2017
• Est. Priority Date: 12/25/2009
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Miyake, Hiroyuki
• Primary Examiner(s): Sharifi-Tafreshi, Koosha
• Application Number:
  US12/976,431
• Publication Number:
  US 20110157131A1
• Time in Patent Office: 2,561 Days
• Field of Search: 345 87-104, 345204, 345690
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 2300/0404 Matrix technologies
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: G09G 5/18 Timing circuits for raster scan displays specially adapted for television H04N ; synchronisation between the display unit and other display units, videodisc player G09G5/12

Abstract

An object is to suppress deterioration of a displayed image even when a refresh rate is reduced in displaying a still image. A liquid crystal display device includes a pixel transistor electrically connected to a pixel electrode, and a capacitor having one electrode electrically connected to the pixel electrode and the other electrode electrically connected to a capacitor line. The pixel transistor is turned on and a voltage based on an image signal is supplied to the pixel electrode, and then, the pixel transistor is turned off so that a holding period during which the pixel electrode holds the voltage based on the image signal starts. A holding signal corresponding to change of the voltage based on the image signal in the pixel electrode in the holding period is supplied to the capacitor line so that a potential of the pixel electrode is constant.

Claims

1. A method for driving a liquid crystal display device that is capable of displaying a still image and a moving image, the liquid crystal display device comprising a transistor electrically connected to a pixel electrode, and a capacitor having a first electrode electrically connected to the pixel electrode and a second electrode electrically connected to a capacitor line, wherein a gate of the transistor is electrically connected to a gate line,

the method comprising the steps of:

supplying an image signal to the pixel electrode through the transistor by turning on the transistor in a writing period;

holding a potential of the pixel electrode by turning off the transistor in a holding period to display the still image; and

changing a potential of the capacitor line throughout the holding period,

wherein one frame period comprises the writing period and the holding period,

wherein a channel formation region of the transistor comprises an oxide semiconductor,

wherein the liquid crystal display device further comprises a current source circuit being electrically connected to the second electrode of the capacitor through the capacitor line, and

wherein current flows in the current source circuit when the liquid crystal display device displays the still image.

2. The method for driving a liquid crystal display device, according to claim 1, wherein the liquid crystal display device is driven with frame inversion driving, common inversion driving, source line inversion driving, gate line inversion driving, or dot inversion driving per frame period.

3. The method for driving a liquid crystal display device, according to claim 1, wherein the potential of the capacitor line is lowered while the potential of the pixel electrode is held.

4. The method for driving a liquid crystal display device, according to claim 1, wherein the potential of the capacitor line is raised while the potential of the pixel electrode is held.

5. The method for driving a liquid crystal display device according to claim 1, wherein the oxide semiconductor comprises In, Ga, Zn and oxygen.

11. The method for driving a liquid crystal display device according to claim 1, wherein the potential of the capacitor line keeps changing during the holding period and the writing period.

13. The method for driving a liquid crystal display device according to claim 1,

wherein the liquid crystal display device comprises a plurality of pixels arranged in a column,

wherein each of the plurality of pixels comprises the transistor and the capacitor, and

wherein the second electrodes of the capacitors of the plurality of pixels arranged in the column are electrically connected to the same capacitor line.

20. The method for driving a liquid crystal display device according to claim 1, wherein the potential of the capacitor line is lowered or raised monotonically throughout the holding period.

6. A method for driving a liquid crystal display device that is capable of displaying a still image and a moving image, the liquid crystal display device comprising a transistor electrically connected to a pixel electrode, and a capacitor having a first electrode electrically connected to the pixel electrode and a second electrode electrically connected to a capacitor line, wherein a gate of the transistor is electrically connected to a gate line, the method comprising the steps of:

supplying an image signal to the pixel electrode through the transistor by turning on the transistor in a writing period; and

holding a potential of the pixel electrode by turning off the transistor in a holding period to display the still image,

wherein a potential of the capacitor line is changed throughout the holding period,

wherein a refresh rate during display of the still image is lower than a refresh rate during display of the moving image,

wherein one frame period comprises the writing period and the holding period,

wherein a channel formation region of the transistor comprises an oxide semiconductor,

wherein the liquid crystal display device further comprises a current source circuit being electrically connected to the second electrode of the capacitor through the capacitor line, and

wherein current flows in the current source circuit when the liquid crystal display device displays the still image.

7. The method for driving a liquid crystal display device according to claim 6, wherein the liquid crystal display device is driven with frame inversion driving, common inversion driving, source line inversion driving, gate line inversion driving, or dot inversion driving per frame period.

8. The method for driving a liquid crystal display device according to claim 6, wherein the potential of the capacitor line is lowered while the potential of the pixel electrode is held.

9. The method for driving a liquid crystal display device according to claim 6, wherein the potential of the capacitor line is raised while the potential of the pixel electrode is held.

10. The method for driving a liquid crystal display device according to claim 6, wherein the oxide semiconductor comprises In, Ga, Zn and oxygen.

12. The method for driving a liquid crystal display device according to claim 6, wherein the potential of the capacitor line keeps changing during the holding period and the writing period.

14. The method for driving a liquid crystal display device according to claim 6,

wherein the liquid crystal display device comprises a plurality of pixels arranged in a column,

wherein each of the plurality of pixels comprises the transistor and the capacitor, and

wherein the second electrodes of the capacitors of the plurality of pixels arranged in the column are electrically connected to the same capacitor line.

21. The method for driving a liquid crystal display device according to claim 6, wherein the potential of the capacitor line is lowered or raised monotonically throughout the holding period.

15. A method for driving a liquid crystal display device, the liquid crystal display device comprising a transistor electrically connected to a pixel electrode, and a capacitor having a first electrode electrically connected to the pixel electrode and a second electrode electrically connected to a capacitor line,,

the method comprising the steps of:

supplying an image signal to the pixel electrode through the transistor by turning on the transistor in a writing period; and

holding a potential of the pixel electrode by turning off the transistor in a holding period,

wherein a potential of the capacitor line is lowered or raised monotonically at least during the holding period,

wherein one frame period comprises the writing period and the holding period,

wherein a channel formation region of the transistor comprises an oxide semiconductor,

wherein the liquid crystal display device further comprises a current source circuit being electrically connected to the second electrode of the capacitor through the capacitor line, and

wherein current flows in the current source circuit when the liquid crystal display device displays a still image.

16. The method for driving a liquid crystal display device according to claim 15,

wherein the liquid crystal display device is capable of displaying a still image and a moving image, and

wherein a refresh rate during display of the still image is lower than a refresh rate during display of the moving image.

17. The method for driving a liquid crystal display device according to claim 15, wherein the oxide semiconductor comprises In, Ga, Zn and oxygen.

18. The method for driving a liquid crystal display device according to claim 15, wherein the potential of the capacitor line keeps changing during the holding period and the writing period.

19. The method for driving a liquid crystal display device according to claim 15,

wherein the liquid crystal display device comprises a plurality of pixels arranged in a column,

wherein each of the plurality of pixels comprises the transistor and the capacitor, and

wherein the second electrodes of the capacitors of the plurality of pixels arranged in the column are electrically connected to the same capacitor line.