LIQUID CRYSTAL DISPLAY DEVICE, DRIVING METHOD OF THE SAME, AND ELECTRONIC APPLIANCE INCLUDING THE SAME

• US 20110102696A1
• Filed: 10/26/2010
• Published: 05/05/2011
• Est. Priority Date: 10/30/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: YAMAZAKI, Shunpei, KOYAMA, Jun
• Granted Patent: US 9,207,511 B2
• Time in Patent Office: Days
• US Class Current: 349/42
• CPC Class Codes: G02F 1/13458 Terminal pads
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO

Abstract

An object is to provide a liquid crystal display device in which low power consumption can be achieved. A first substrate includes a terminal portion, a switching transistor, and a pixel circuit including a pixel electrode is provided. A second substrate includes a counter electrode. A liquid crystal element is interposed between the pixel electrode and the counter electrode. A potential to be input to the counter electrode is supplied from a terminal portion through the switching transistor. A semiconductor layer included in the switching transistor is an oxide semiconductor layer.

Claims

1. A liquid crystal display device comprising:

a first substrate provided with;

a terminal portion,

a switching transistor, and

a pixel circuit including a pixel, the pixel having a pixel transistor and a pixel electrode electrically connected to the pixel transistor;

a second substrate provided with a counter electrode; and

a liquid crystal interposed between the pixel electrode and the counter electrode,

wherein the counter electrode is electrically connected to the terminal portion through the switching transistor, and

wherein each of the pixel transistor and the switching transistor includes an oxide semiconductor layer.

2. The liquid crystal display device according to claim 1,

wherein a gate line driver circuit and a signal line driver circuit are provided over the first substrate.

3. The liquid crystal display device according to claim 1,

wherein a hydrogen concentration of the oxide semiconductor layer is 1×

10¹⁶/cm³ or less.

4. The liquid crystal display device according to claim 1,

wherein a carrier concentration of the oxide semiconductor layer is less than 1×

10¹⁴/cm³.

5. An electronic appliance including the liquid crystal display device according to claim 1.

6. The liquid crystal display device according to claim 1, wherein the oxide semiconductor layer includes In—

Ga—

Zn—

O based semiconductor.

7. The liquid crystal display device according to claim 1, wherein the oxide semiconductor layer has a thickness of 50 nm or less.

8. The liquid crystal display device according to claim 1, wherein the counter electrode is electrically connected to the switching transistor through a conductive particle.

9. The liquid crystal display device according to claim 8, further comprising:

a sealing material in contact with and surrounding the liquid crystal; and

a resin layer in contact with the sealing material,

wherein the conductive particle is provided in the resin layer.

10. A liquid crystal display device comprising:

a first substrate provided with;

a terminal portion,

a switching transistor, and

a pixel circuit including a pixel, the pixel having a pixel transistor and

a pixel electrode electrically connected to the pixel transistor;

a second substrate provided with a counter electrode; and

a liquid crystal interposed between the pixel electrode and the counter electrode,

wherein the counter electrode is electrically connected to the terminal portion through the switching transistor,

wherein the pixel transistor and the switching transistor each include an oxide semiconductor layer, and

wherein each of the pixel transistor and the switching transistor has a bottom-gate structure.

11. The liquid crystal display device according to claim 10,

wherein a gate line driver circuit and a signal line driver circuit are provided over the first substrate.

12. The liquid crystal display device according to claim 10,

wherein a hydrogen concentration of the oxide semiconductor layer is 1×

10¹⁶/cm³ or less.

13. The liquid crystal display device according to claim 10,

wherein a carrier concentration of the oxide semiconductor layer is less than 1×

10¹⁴/cm³.

14. An electronic appliance including the liquid crystal display device according to claim 10.

15. The liquid crystal display device according to claim 10, wherein the oxide semiconductor layer includes In—

Ga—

Zn—

O based semiconductor.

16. The liquid crystal display device according to claim 10, wherein the oxide semiconductor layer has a thickness of 50 nm or less.

17. The liquid crystal display device according to claim 10, wherein the counter electrode is electrically connected to the switching transistor through a conductive particle.

18. The liquid crystal display device according to claim 17, further comprising:

a sealing material in contact with and surrounding the liquid crystal; and

a resin layer in contact with the sealing material,

wherein the conductive particle is provided in the resin layer.

19. A driving method of a liquid crystal display device including a first substrate provided with a terminal portion, a switching transistor having a first oxide semiconductor layer, and a pixel circuit including a pixel having a pixel transistor having a second oxide semiconductor layer and a pixel electrode electrically connected to the pixel transistor, a second substrate provided with a counter electrode electrically connected to the terminal portion through the switching transistor, and a liquid crystal interposed between the pixel electrode and the counter electrode, comprising the steps of:

in a first period where a moving image is displayed, making a first terminal of the switching transistor and a second terminal of the switching transistor into a conduction state so as to supply a common potential to the counter electrode; and

in a second period where a still image is displayed, making the first terminal and the second terminal into a non-conduction state so as to make the counter electrode into an electrically floating state.

20. The driving method of a liquid crystal display device according to claim 19, further comprising:

in the first period, supplying a first signal for driving the pixel transistor from a gate line driver circuit to the pixel transistor and a second signal from a signal line driver circuit to the pixel transistor; and

in the second period, stopping the first signal and the second signal.

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

wherein a conduction state or a non-conduction state between the counter electrode and the terminal portion to which the common potential is supplied is controlled by the switching transistor in accordance with a signal supplied from the terminal portion to a gate terminal of the switching transistor.