TOUCH PANEL AND DRIVING METHOD OF TOUCH PANEL

• US 20110109591A1
• Filed: 10/28/2010
• Published: 05/12/2011
• Est. Priority Date: 11/06/2009
• Status: Abandoned Application

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: IKEDA, Takayuki, YAMAZAKI, Shunpei, KUROKAWA, Yoshiyuki, TAMURA, Hikaru
• Application Number:
  US12/914,626
• Publication Number:
  US 20110109591A1
• Time in Patent Office: Days
• US Class Current: 345/175
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/1354 having a particular photoconducting structure or material
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

Disclosed is a touch panel including a plurality of pixels each including a display element and a photosensor. The display element includes a transistor having an oxide semiconductor layer. The photosensor includes a photodiode, a first transistor, and a second transistor, and the first and second transistors include an oxide semiconductor layer. A driving method of the touch panel is also disclosed by which high-speed imaging is realized.

Claims

1. A touch panel comprising;

a pixel comprising a display element and a photosensor,

wherein the photosensor comprises a photodiode and a first transistor which are electrically connected to each other, and

wherein the first transistor comprises an oxide semiconductor layer in which a channel formation region is formed.

2. The touch panel according to claim 1,

wherein the photosensor further comprises a second transistor,

wherein the photodiode is electrically connected to a gate of the first transistor,

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

wherein the second transistor comprises an oxide semiconductor layer in which a channel formation region is formed.

3. The touch panel according to claim 1,

wherein the oxide semiconductor layer of the first transistor contains indium, gallium, and zinc.

4. The touch panel according to claim 2,

wherein the oxide semiconductor layer of the second transistor contains indium, gallium, and zinc.

5. The touch panel according to claim 1,

wherein a hydrogen concentration of the oxide semiconductor layer of the first transistor is less than or equal to 5×

10¹⁹/cm³.

6. The touch panel according to claim 2,

wherein a hydrogen concentration of the oxide semiconductor layer of the second transistor is less than or equal to 5×

10¹⁹/cm³.

7. The touch panel according to claim 1,

wherein the display element is selected from a liquid crystal element and a light emitting diode.

8. The touch panel according to claim 2,

wherein the photosensor further comprises:

a first signal line;

a second signal line;

a third signal line; and

a fourth signal line,

wherein the first signal line is electrically connected to the photodiode,

wherein the second signal line is electrically connected to a second terminal of the second transistor,

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

wherein the fourth signal line is electrically connected to a second terminal of the first transistor.

9. A driving method of a touch panel comprising a plurality of pixels,

wherein the plurality of pixels are arranged in a matrix form having a plurality of rows,

wherein at least one of the plurality of pixels comprises a display element and a photosensor,

wherein the photosensor comprises a photodiode and a first transistor which are electrically connected to each other, and

wherein the first transistor comprises an oxide semiconductor layer in which a channel formation region is formed,

the driving method comprising a step of performing a reset operation, an accumulating operation, and a selection operation in that order for each of the plurality of rows,

wherein the reset operation of one of the plurality of rows and the selection operation of another one of the plurality of rows are performed simultaneously.

10. The driving method according to claim 9,

wherein the oxide semiconductor layer of the first transistor contains indium, gallium, and zinc.

11. The driving method according to claim 9,

wherein the photodiode is electrically connected to a gate of the first transistor,

wherein the photosensor further comprises:

a first signal line electrically connected to the photodiode;

a second transistor whose first terminal is electrically connected to a first terminal of the first transistor; and

a second signal line electrically connected to a second terminal of the second transistor,

wherein the second transistor comprises an oxide semiconductor layer, in which a channel formation region is formed, and

wherein the reset operation includes the steps of;

setting a potential of the first signal line to a first potential so that a forward bias is applied to the photodiode, and

precharging the second signal line.

12. The driving method according to claim 11,

wherein the oxide semiconductor layer of the second transistor contains indium, gallium, and zinc.

13. The driving method according to claim 11,

wherein the accumulating operation includes a step of setting the potential of the first signal line to a second potential to allow a potential of the gate of the first transistor to be decreased.

14. The driving method according to claim 11,

wherein the photosensor further comprises a third signal line electrically connected to a gate of the second transistor,

wherein the selection operation includes a step of setting a potential of the third signal line to a third potential so that the second transistor exists in a conduction state, which is followed by a step of setting the potential of the third signal line to a fourth potential so that the second transistor exists in an off state.

15. The driving method according to claim 9,

wherein a hydrogen concentration of the oxide semiconductor layer of the first transistor is less than or equal to 5×

10¹⁹/cm³.

16. The driving method according to claim 11,

wherein a hydrogen concentration of the oxide semiconductor layer of the second transistor is less than or equal to 5×

10¹⁹/cm³.

17. The driving method according to claim 9,

wherein the display element is selected from a liquid crystal element and a light emitting diode.

18. A driving method of a touch panel comprising a plurality of pixels,

wherein the plurality of pixels are arranged in a matrix form having first to n^th rows where n is a natural number larger than 2,

wherein at least one of the plurality of pixels comprises a display element and a photosensor,

wherein the photosensor comprises a photodiode and a first transistor which are electrically connected to each other, and

wherein the first transistor comprises an oxide semiconductor layer in which a channel formation region is formed,

the driving method comprising a step of performing a reset operation, an accumulating operation, and a selection operation in that order for each of the first to n^th rows,

wherein, in a period between an end of the reset operation of the m^th row and a start of the sequential reset operation of the (m+1)th row, the selection operation of another one of the first to n^th rows is performed, and

wherein m is a natural number less than n.

19. The driving method according to claim 18,

wherein the oxide semiconductor layer of the first transistor contains indium, gallium, and zinc.

20. The driving method according to claim 18,

wherein the photodiode is electrically connected to a gate of the first transistor,

wherein the photosensor further comprises:

a first signal line electrically connected to the photodiode;

a second transistor whose first terminal is electrically connected to a first terminal of the first transistor; and

a second signal line electrically connected to a second terminal of the second transistor,

wherein the second transistor comprises an oxide semiconductor layer in which a channel formation region is formed, and

wherein the reset operation includes the steps of;

setting a potential of the first signal line to a first potential so that a forward bias is applied to the photodiode, and

precharging the second signal line.

21. The driving method according to claim 20,

wherein the oxide semiconductor layer of the second transistor contains indium, gallium, and zinc.

22. The driving method according to claim 20,

wherein the accumulating operation includes a step of setting the potential of the first signal line to a second potential to allow a potential of the gate of the first transistor to be decreased.

23. The driving method according to claim 20,

wherein the photosensor further comprises a third signal line electrically connected to a gate of the second transistor,

wherein the selection operation includes a step of setting a potential of the third signal line to a third potential so that the second transistor exists in a conduction state, which is followed by a step of setting the potential of the third signal line to a fourth potential so that the second transistor exists in an off state.

24. The driving method according to claim 18,

wherein a hydrogen concentration of the oxide semiconductor layer of the first transistor is less than or equal to 5×

10¹⁹/cm³.

25. The driving method according to claim 20,

wherein a hydrogen concentration of the oxide semiconductor layer of the second transistor is less than or equal to 5×

10¹⁹/cm³.

26. The driving method according to claim 18,

wherein the display element is selected from a liquid crystal element and a light emitting diode.