Liquid crystal display device and driving method of the same

• US 8,890,859 B2
• Filed: 03/19/2014
• Issued: 11/18/2014
• Est. Priority Date: 08/06/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Toyotaka, Kouhei, Miyake, Hiroyuki, Arasawa, Ryo, Kusunoki, Koji, Murakawa, Tsutomu
• Primary Examiner(s): Amadiz, Rodney
• Application Number:
  US14/219,275
• Publication Number:
  US 20140204073A1
• Time in Patent Office: 244 Days
• Field of Search: 345 87-100, 345/204, 345211-213, 361/56
• US Class Current: 345/212
• 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 2330/04 Display protection
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

Provided is a liquid crystal display device having a pixel including a transistor and a liquid crystal element and a protection circuit electrically connected to one of a source and a drain of the transistor through a data line. The protection circuit includes a first terminal supplied with a first power supply potential and a second terminal supplied with a second power supply potential higher than the first power supply potential. In a moving image display mode, an image signal is input from the data line to the liquid crystal element through the transistor, and the first power supply potential is set at the first potential. In a still image display mode, supply of the image signal is stopped, and the first power supply potential is set at the second potential. The second potential is substantially the same as the minimum value of the image signal.

Claims

1. A display device comprising:

a pixel portion comprising;

a data line; and

a plurality of pixels arranged along the data line, each of the plurality of pixels comprising;

a display element comprising a pixel electrode and a common electrode; and

a first transistor electrically connected to the data line and the pixel electrode;

a data driver electrically connected to the data line; and

a protection circuit electrically connected to the data line,

wherein the pixel portion is located between the data driver and the protection circuit, and

wherein the protection circuit comprises a second transistor and a third transistor each comprising a first terminal, a second terminal, and a gate,

wherein the first terminal of the second transistor is electrically connected to the gate of the second transistor, and

wherein the second terminal of the second transistor is electrically connected to the data line, the first terminal of the third transistor, and the gate of the third transistor.

2. The display device according to claim 1, further comprising a first resistor and a first capacitor which are electrically connected in parallel between the first terminal of the second transistor and the gate of the second transistor.

3. The display device according to claim 1, further comprising:

a fourth transistor and a fifth transistor each comprising a first terminal, a second terminal, and a gate,

wherein the first terminal of the fourth transistor is electrically connected to the first terminal of the second transistor and the gate of the fourth transistor,

wherein the second terminal of the fourth transistor is electrically connected to the first terminal of the fifth transistor and the gate of the fifth transistor, and

wherein the second terminal of the fifth transistor is electrically connected to the second terminal of the third transistor.

4. The display device according to claim 1, further comprising a sixth transistor electrically connected to the common electrodes.

5. The display device according to claim 1, wherein the first transistors each comprise a semiconductor layer which comprises an oxide semiconductor.

6. The display device according to claim 1,

wherein the pixel portion further comprises a gate line electrically connected to at least one of the first transistors, and

wherein the second terminal of the third transistor is configured to be input with a high-power supply potential which is higher than a potential applied to the common electrodes and equal to or lower than a potential applied to the gate line to turn on the first transistor.

7. The display device according to claim 6,

wherein the first terminal of the second transistor is configured to be input with a low-power supply potential which is lower than the high-power supply potential,

wherein the low-power supply potential is configured to be set at a first potential or a second potential which is higher than the second potential, and

wherein the first potential is lower than a minimum potential input to the data line or equal to a potential applied to the gate line to turn off the first transistor.

8. The display device according to claim 1, wherein the first transistor is configured to be input with a positive signal and a negative signal alternately.

9. An electronic device comprising the display device according to claim 1.

10. A display device comprising:

a pixel portion comprising;

a data line; and

a plurality of pixels arranged along the data line, each of the plurality of pixels comprising;

a display element comprising a pixel electrode and a common electrode; and

a first transistor electrically connected to the data line and the pixel electrode;

a data driver electrically connected to the data line; and

a protection circuit electrically connected to the data line,

wherein the pixel portion is located between the data driver and the protection circuit, and

wherein the protection circuit comprises a second transistor, a third transistor, a fourth transistor, and a fifth transistor, each of which comprises a first terminal, a second terminal, and a gate,

wherein the first terminal of the second transistor is electrically connected to the gate of the second transistor,

wherein the second terminal of the second transistor is electrically connected to the first terminal of the third transistor and the gate of the third transistor,

wherein the second terminal of the third transistor is electrically connected to the data line, the first terminal of the fourth transistor, and the gate of the fourth transistor, and

wherein the second terminal of the fourth transistor is electrically connected to the first terminal of the fifth transistor and the gate of the fifth transistor.

11. The display device according to claim 10,

wherein the gate of the second transistor is electrically connected to the gate of the third transistor, and

wherein the gate of the fourth transistor is electrically connected to the gate of the fifth transistor.

12. An electronic device comprising the display device according to claim 11.

13. The display device according to claim 10, further comprising a sixth transistor electrically connected to the common electrodes.

14. The display device according to claim 10, wherein the first transistors each comprise a semiconductor layer which comprises an oxide semiconductor.

15. The display device according to claim 10,

wherein the pixel portion further comprises a gate line electrically connected to at least one of the first transistors, and

wherein the second terminal of the third transistor is configured to be input with a high-power supply potential which is higher than a potential applied to the common electrodes and equal to or lower than a potential applied to the gate line to turn on the first transistor.

16. The display device according to claim 15,

wherein the first terminal of the second transistor is configured to be input with a low-power supply potential which is lower than the high-power supply potential,

wherein the low-power supply potential is configured to be set at a first potential or a second potential which is higher than the second potential, and

wherein the first potential is lower than a minimum potential input to the data line or equal to a potential applied to the gate line to turn off the first transistor.

17. The display device according to claim 10, wherein the first transistor is configured to be input with a positive signal and a negative signal alternately.