Method for driving liquid crystal display device

• US 8,922,537 B2
• Filed: 11/25/2013
• Issued: 12/30/2014
• Est. Priority Date: 12/18/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun, Miyake, Hiroyuki
• Primary Examiner(s): Zhou, Hong
• Application Number:
  US14/089,025
• Publication Number:
  US 20140078132A1
• Time in Patent Office: 400 Days
• Field of Search: 345204-211, 345 87-100, 345173-174, 257/43, 257/59
• US Class Current: 345/204
• CPC Class Codes: G02F 1/1345 Conductors connecting electrodes to cell terminals
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2320/0219 Reducing feedthrough effects in active matrix panels, i.e. voltage changes on the scan electrode influencing the pixel voltage due to capacitive coupling
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• 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 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 2354/00 Aspects of interface with display user
• CPC Class Codes: G09G 3/3618 with automatic refresh of the display panel using sense/write circuits
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• 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 3/3696 Generation of voltages supplied to electrode drivers

Abstract

The liquid crystal display device includes a first substrate provided with a terminal portion, a switching transistor, a driver circuit portion, and a pixel circuit portion including a pixel transistor and a plurality of pixels, a second substrate provided with a common electrode electrically connected to the terminal portion through the switching transistor, and liquid crystal between a pixel electrode and the common electrode. In a period during which a still image is switched to a moving image, the following steps are sequentially performed: a first step of supplying the common potential to the common electrode; a second step of supplying a power supply voltage to the driver circuit portion; a third step of supplying a clock signal to the driver circuit portion; and a fourth step of supplying a start pulse signal to the driver circuit portion.

Claims

1. A driving method of a display device which comprises:

a display panel comprising a pixel circuit portion, the pixel circuit portion comprising a pixel electrode and a transistor electrically connected to the pixel electrode, wherein the transistor comprises an oxide semiconductor layer including a channel formation region; and

a touch panel superimposed on the display panel,

the driving method comprising;

displaying a moving image in a first period at a first refresh rate; and

displaying a still image in a second period at a second refresh rate which is smaller than the first refresh rate,

wherein an off current per micrometer in a channel width of the transistor is less than or equal to 1×

10<sup>−

17</sup> A/μ

m.

2. The driving method according to claim 1, wherein the off current is at a room temperature.

3. The driving method according to claim 1, wherein the touch panel is a capacitive type.

4. The driving method according to claim 1, wherein the display panel is a liquid crystal device.

5. The driving method according to claim 1, wherein the display panel is a reflective type liquid crystal device.

6. A driving method of a display device which comprises:

a display panel comprising a pixel circuit portion and a gate line driver circuit for driving the pixel circuit portion; and

a touch panel superimposed on the display panel,

the driving method comprising;

displaying a moving image in a first period at a first refresh rate;

stopping supply of a start pulse to the gate line driver circuit in a second period after the first period;

stopping supply of a clock signal to the gate line driver circuit in the second period after stopping the supply of the start pulse; and

displaying a still image in a third period after the second period at a second refresh rate which is smaller than the first refresh rate,

wherein the pixel circuit portion comprises a pixel electrode and a first transistor electrically connected to the pixel electrode, the first transistor comprising a first oxide semiconductor layer including a channel formation region over a substrate, and

wherein the gate line driver circuit comprises a second transistor, the second transistor comprising a second oxide semiconductor layer including a channel formation region over the substrate.

7. The driving method according to claim 6,

wherein an off current per micrometer in a channel width of the first transistor is less than or equal to 1×

10<sup>−

17</sup> A/μ

m, and

wherein the off current is at a room temperature.

8. The driving method according to claim 6, wherein the touch panel is a capacitive type.

9. The driving method according to claim 6, wherein supply of a high power potential and a low power supply potential to the gate line driver circuit is continued during displaying the still image in the third period.

10. The driving method according to claim 6, wherein the display panel is a reflective type liquid crystal device.

11. The driving method according to claim 6, wherein the second transistor comprises a gate electrode and a conductive layer over the gate electrode with the channel formation region of the second oxide semiconductor layer interposed therebetween, the gate electrode and the conductive layer being supplied with a same potential.

12. The driving method according to claim 6, wherein the display panel comprises a memory for storing data regarding a threshold value of an electric signal of the touch panel.

13. A display device comprising:

a display panel comprising a pixel circuit portion and a gate line driver circuit for driving the pixel circuit portion;

a touch panel superimposed on the display panel;

a comparison circuit configured to compare image signals in each of pixels in order to determine if an image is a moving image or a still image; and

a display control circuit configured to control operation of the gate line driver circuit in accordance with a determination by the comparison circuit,

wherein, when the image is a moving image, the display control circuit is configured to control the gate line driver circuit so that the moving image is displayed at a first refresh rate,

wherein, when the image is a still image, the display control circuit is configured to control the gate line driver circuit so that the still image is displayed at a second refresh rate smaller than the first refresh rate,

wherein the pixel circuit portion comprises a pixel electrode and a first transistor electrically connected to the pixel electrode, the first transistor comprising a first oxide semiconductor layer including a channel formation region over a substrate,

wherein the gate line driver circuit comprises a second transistor, the second transistor comprising a second oxide semiconductor layer including a channel formation region over the substrate, and

wherein an off current per micrometer in a channel width of the first transistor is less than or equal to 1×

10<sup>−

17</sup> A/μ

m.

14. The display device according to claim 13, wherein the off current is at a room temperature.

15. The display device according to claim 13, wherein the touch panel is a capacitive type.

16. The display device according to claim 13, wherein supply of a high power potential and a low power supply potential to the gate line driver circuit is continued during displaying the still image.

17. The display device according to claim 13, wherein the display panel is a reflective type liquid crystal device.

18. The display device according to claim 13, wherein the second transistor comprises a gate electrode and a conductive layer over the gate electrode with the channel formation region of the second oxide semiconductor layer interposed therebetween, the gate electrode and the conductive layer being supplied with a same potential.

19. The display device according to claim 13, wherein the display panel comprises a memory for storing data regarding a threshold value of an electric signal of the touch panel.