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

• US 20110128461A1
• Filed: 11/29/2010
• Published: 06/02/2011
• Est. Priority Date: 11/30/2009
• 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 8,531,618 B2
• Time in Patent Office: Days
• US Class Current: 349/42
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2202/10 semiconductor
• 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 2360/10 Display system comprising arrangements, such as a coprocessor, specific for motion video images
• CPC Class Codes: G09G 3/3659 the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 5/005 Adapting incoming signals to the display format of the display terminal
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO

Abstract

The liquid crystal display device includes a pixel portion including a plurality of pixels to which image signals are supplied; a driver circuit including a signal line driver circuit which selectively controls a signal line and a gate line driver circuit which selectively controls a gate line; a memory circuit which stores the image signals; a comparison circuit which compares the image signals stored in the memory circuit in the pixels and detects a difference; and a display control circuit which controls the driver circuit and reads the image signal in accordance with the difference. The display control circuit supplies the image signal only to the pixel where the difference is detected. The pixel includes a thin film transistor including a semiconductor layer including an oxide semiconductor.

Claims

1. A liquid crystal display device comprising:

a pixel portion including a plurality of pixels arranged so that at least a first image signal and a second image signal are supplied;

a driver circuit including a signal line driver circuit configured to control a signal line selectively and a gate line driver circuit configured to control a gate line selectively;

a memory circuit configured to store the first image signal and the second image signal;

a comparison circuit configured to compare the first image signal and the second image signal stored in the memory circuit in the pixel and to detect a difference between the first image signal and the second image signal; and

a display control circuit configured to control the driver circuit and to read the second image signal in accordance with the difference,

wherein the display control circuit is configured to supply the second image signal only to the pixel where the difference is detected,

wherein the pixel includes a thin film transistor,

wherein a gate of the thin film transistor is electrically connected to the gate line, a first terminal of the thin film transistor is electrically connected to the signal line, and a second terminal of the thin film transistor is electrically connected to a pixel electrode, and

wherein the thin film transistor includes a semiconductor layer including an oxide semiconductor.

2. The liquid crystal display device according to claim 1, wherein a concentration of hydrogen in the oxide semiconductor that is measured by secondary ion mass spectroscopy is 1×

10¹⁶/cm³ or lower.

3. The liquid crystal display device according to claim 1, wherein a carrier concentration of the oxide semiconductor is lower than 1×

10¹⁴/cm³.

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

wherein the pixel portion includes the pixel electrode in each pixel and is provided over a first substrate together with a terminal portion and a switching transistor,

wherein a counter electrode is provided on a second substrate,

wherein a liquid crystal is held 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 a semiconductor layer included in the switching transistor includes an oxide semiconductor.

5. The liquid crystal display device according to claim 4, wherein a concentration of hydrogen in the semiconductor layer of the switching transistor that is measured by secondary ion mass spectroscopy is 1×

10¹⁶/cm³ or lower.

6. The liquid crystal display device according to claim 4, wherein a carrier concentration of the semiconductor layer of the switching transistor is lower than 1×

10¹⁴/cm³.

7. An electronic device comprising the liquid crystal display device according to claim 1.

8. A liquid crystal display device comprising:

a pixel portion including a plurality of pixels arranged so that at least a first image signal and a second image signal are supplied;

a driver circuit including a signal line driver circuit configured to control a signal line and a selection line selectively and a gate line driver circuit configured to control a gate line selectively with a decoder circuit;

a memory circuit configured to store the first image signal and the second image signal;

a comparison circuit configured to compare the first image signal and the second image signal stored in the memory circuit in the pixel and to detect a difference between the first image signal and the second image signal; and

a display control circuit configured to control the driver circuit and to read the second image signal in accordance with the difference,

wherein the display control circuit is configured to supply the second image signal only to the pixel where the difference is detected by control of the decoder circuit,

wherein the pixel includes a first thin film transistor and a second thin film transistor,

wherein a gate of the first thin film transistor is electrically connected to the gate line, a first terminal of the first thin film transistor is electrically connected to the signal line, and a second terminal of the first thin film transistor is electrically connected to a first terminal of the second thin film transistor,

wherein a gate of the second thin film transistor is electrically connected to the selection line and a second terminal of the second thin film transistor is electrically connected to a pixel electrode, and

wherein the first thin film transistor and the second thin film transistor each include a semiconductor layer including an oxide semiconductor.

9. The liquid crystal display device according to claim 8, wherein a concentration of hydrogen in the oxide semiconductor that is measured by secondary ion mass spectroscopy is 1×

10¹⁶/cm³ or lower.

10. The liquid crystal display device according to claim 8, wherein a carrier concentration of the oxide semiconductor is lower than 1×

10¹⁴/cm³.

11. The liquid crystal display device according to claim 8,

wherein the pixel portion includes the pixel electrode in each pixel and is provided over a first substrate together with a terminal portion and a switching transistor,

wherein a counter electrode is provided on a second substrate,

wherein a liquid crystal is held 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 a semiconductor layer included in the switching transistor includes an oxide semiconductor.

12. The liquid crystal display device according to claim 11, wherein a concentration of hydrogen in the semiconductor layer of the switching transistor that is measured by secondary ion mass spectroscopy is 1×

10¹⁶/cm³ or lower.

13. The liquid crystal display device according to claim 11, wherein a carrier concentration of the semiconductor layer of the switching transistor is lower than 1×

10¹⁴/cm³.

14. An electronic device comprising the liquid crystal display device according to claim 8.

15. A liquid crystal display device comprising:

a pixel portion including a plurality of pixels arranged so that at least a first image signal and a second image signal are supplied;

a driver circuit including a signal line driver circuit configured to control a signal line selectively with a shift register circuit and a gate line driver circuit configured to control a gate line selectively with a decoder circuit;

a memory circuit configured to store the first image signal and the second image signal;

a comparison circuit configured to compare the first image signal and the second image signal stored in the memory circuit in the pixel and to detect a difference between the first image signal and the second image signal; and

a display control circuit configured to control the driver circuit and to read the second image signal in accordance with the difference,

wherein the display control circuit is configured to supply the second image signal to the pixel where the difference is detected by control of the decoder circuit,

wherein the pixel includes a thin film transistor,

wherein a gate of the thin film transistor is electrically connected to the gate line, a first terminal of the thin film transistor is electrically connected to the signal line, and a second terminal of the thin film transistor is electrically connected to a pixel electrode, and

wherein the thin film transistor includes a semiconductor layer including an oxide semiconductor.

16. The liquid crystal display device according to claim 15, wherein a concentration of hydrogen in the oxide semiconductor that is measured by secondary ion mass spectroscopy is 1×

10¹⁶/cm³ or lower.

17. The liquid crystal display device according to claim 15, wherein a carrier concentration of the oxide semiconductor is lower than 1×

10¹⁴/cm³.

18. The liquid crystal display device according to claim 15,

wherein the pixel portion includes the pixel electrode in each pixel and is provided over a first substrate together with a terminal portion and a switching transistor,

wherein a counter electrode is provided on a second substrate,

wherein a liquid crystal is held 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 a semiconductor layer included in the switching transistor includes an oxide semiconductor.

19. The liquid crystal display device according to claim 18, wherein a concentration of hydrogen in the semiconductor layer of the switching transistor that is measured by secondary ion mass spectroscopy is 1×

10¹⁶/cm³ or lower.

20. The liquid crystal display device according to claim 18, wherein a carrier concentration of the semiconductor layer of the switching transistor is lower than 1×

10¹⁴/cm³.

21. An electronic device comprising the liquid crystal display device according to claim 15.

22. A method for driving a liquid crystal display device including a pixel portion including a plurality of pixels to which image signals are supplied and which are provided with a thin film transistor including a semiconductor layer formed using an oxide semiconductor, a driver circuit including a signal line driver circuit and a gate line driver circuit, a memory circuit configured to store the image signals, a comparison circuit configured to compare the image signals stored in the memory circuit in the pixel and to detect a difference, and a display control circuit configured to control the driver circuit and to read the image signals, comprising the steps of:

reading and comparing first image signal and a second image signal in a series of frame periods that is stored in the memory circuit in each pixel and detecting a difference in the comparison circuit; and

controlling the driver circuit so that the display control circuit supplies the second image signal only to the pixel where the difference is detected in the comparison circuit.