DISPLAY DEVICE AND ELECTRONIC DEVICE INCLUDING THE SAME

• US 20110115839A1
• Filed: 11/12/2010
• Published: 05/19/2011
• Est. Priority Date: 11/13/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: TAKAHASHI, Kei, YAMAZAKI, Shunpei
• Granted Patent: US 9,520,411 B2
• Time in Patent Office: Days
• US Class Current: 345/698
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0286 Details of a shift registers arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 29/78672 Polycrystalline or microcrystalline silicon transistor
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/122 Pixel-defining structures or layers, e.g. banks
• CPC Class Codes: H10K 59/123 Connection of the pixel electrodes to the thin film transistors [TFT]

Abstract

A display device includes a pixel portion including a plurality of pixels each including a first transistor, a second transistor, and a light-emitting element, in which a gate of the first transistor is electrically connected to a scan line, one of a source and a drain of the first transistor is electrically connected to a signal line, and the other of them is electrically connected to a gate of the second transistor; one of a source and a drain of the second transistor is electrically connected to a power supply line and the other of them is electrically connected to the light-emitting element, and the first transistor includes an oxide semiconductor layer. A period when the display device displays a still image includes a period in which output of a signal to all the scan lines in the pixel portion is stopped.

Claims

1. A display device comprising:

a pixel portion comprising a plurality of pixels each including a first transistor, a second transistor, and a light-emitting element having a pair of electrodes,

wherein a first gate of the first transistor is electrically connected to a scan line, one of a first source and a first drain of the first transistor is electrically connected to a signal line, and the other of the first source and the first drain of the first transistor is electrically connected to a second gate of the second transistor,

wherein one of a second source and a second drain of the second transistor is electrically connected to a power supply line and the other of the second source and the second drain of the second transistor is electrically connected to one of the pair of electrodes of the light-emitting element, and

wherein the first transistor comprises a first oxide semiconductor layer a hydrogen concentration of which is 5×

10¹⁹/cm³ or less.

2. The display device according to claim 1, wherein a period when the display device displays a still image includes a period when output of a signal to all the scan lines in the pixel portion is stopped.

3. The display device according to claim 1, wherein the plurality of pixels each further comprises a luminous layer.

4. The display device according to claim 1, wherein a carrier concentration of the first oxide semiconductor layer is less than 1×

10¹⁴/cm³.

5. The display device according to claim 1, wherein a band gap of the first oxide semiconductor layer is 2 eV or more.

6. The display device according to claim 1, wherein the second transistor comprises a second oxide semiconductor layer a hydrogen concentration of which is 5×

10¹⁹/cm³ or less.

7. The display device according to claim 1, wherein the second transistor comprises a polycrystalline silicon layer.

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

9. A display device comprising:

a pixel portion comprising a plurality of pixels each including a first transistor, a second transistor, and a light-emitting element having a pair of electrodes,

a driver circuit portion for driving the pixel portion;

a signal generation circuit for generating a control signal for driving the driver circuit portion and an image signal supplied to the plurality of pixels;

a memory circuit for storing image signals of respective frame periods;

a comparison circuit for detecting a difference between image signals of successive frame periods among the image signals of the respective frame periods stored in the memory circuit;

a selection circuit for selecting and outputting the image signals of the successive frame periods when the comparison circuit detects the difference; and

a display control circuit for supplying the control signal and the image signal output from the selection circuit to the driver circuit portion when the comparison circuit detects the difference, and stopping supply of the control signal to the driver circuit portion when the comparison circuit does not detect the difference,

wherein a first gate of the first transistor is electrically connected to a scan line, one of a first source and a first drain of the first transistor is electrically connected to a signal line, and the other of the first source and the first drain of the first transistor is electrically connected to a second gate of the second transistor,

wherein one of a second source and a second drain of the second transistor is electrically connected to a power supply line and the other of the second source and the second drain of the second transistor is electrically connected to one of the pair of electrodes of the light-emitting element, and

wherein the first transistor comprises a first oxide semiconductor layer a hydrogen concentration of which is 5×

10¹⁹/cm³ or less.

10. The display device according to claim 9, wherein a period when the display device displays a still image includes a period when output of a signal to all the scan lines in the pixel portion is stopped.

11. The display device according to claim 9, wherein the control signal is a high power supply potential, a low power supply potential, a clock signal, a start pulse signal, or a reset signal.

12. The display device according to claim 9, wherein the plurality of pixels each further comprises a luminous layer.

13. The display device according to claim 9, wherein a carrier concentration of the first oxide semiconductor layer is less than 1×

10¹⁴/cm³.

14. The display device according to claim 9, wherein a band gap of the first oxide semiconductor layer is 2 eV or more.

15. The display device according to claim 9, wherein the second transistor comprises a second oxide semiconductor layer a hydrogen concentration of which is 5×

10¹⁹/cm³ or less.

16. The display device according to claim 9, wherein the second transistor comprises a polycrystalline silicon layer.

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

18. A display device comprising:

a pixel portion comprising a plurality of pixels each including a first transistor, a second transistor, and a light-emitting element,

a driver circuit portion for driving the pixel portion;

a signal generation circuit for generating a control signal for driving the driver circuit portion and an image signal to be supplied to the driver circuit portion;

a memory circuit for storing image signals of respective frame periods;

a comparison circuit for detecting and outputting a difference between image signals of successive frame periods among the image signals of the respective frame periods stored in the memory circuit;

a selection circuit for outputting the image signals to be supplied to the driver circuit portion in accordance with an output from the comparison circuit; and

a display control circuit for controlling the control signal from the signal generation circuit and the image signal outputted from the selection circuit to the driver circuit portion in accordance with the output from the comparison circuit,

wherein the first transistor comprises a first oxide semiconductor layer.

19. The display device according to claim 18, wherein the display control circuit is configured so as not to output the control signal to the driver circuit portion in accordance with the output from the comparison circuit.

20. The display device according to claim 18, wherein the control signal is a high power supply potential, a low power supply potential, a clock signal, a start pulse signal, or a reset signal.

21. The display device according to claim 18, wherein the plurality of pixels each further comprises a luminous layer.

22. The display device according to claim 18, wherein a carrier concentration of the first oxide semiconductor layer is less than 1×

10¹⁴/cm³.

23. The display device according to claim 18, wherein a band gap of the first oxide semiconductor layer is 2 eV or more.

24. The display device according to claim 18, wherein the second transistor comprises a second oxide semiconductor layer a hydrogen concentration of which is 5×

10¹⁹/cm³ or less.

25. The display device according to claim 18, wherein the second transistor comprises a polycrystalline silicon layer.

26. An electronic device comprising the display device according to claim 18.