SEMICONDUCTOR DISPLAY DEVICE AND DRIVING METHOD THE SAME

• US 20110267297A1
• Filed: 04/26/2011
• Published: 11/03/2011
• Est. Priority Date: 04/28/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun, Yamazaki, Shunpei
• Granted Patent: US 9,218,081 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 1/3265 Power saving in display device
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• 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 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/14 Detecting light within display terminals, e.g. using a single or a plurality of photosensors
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

It is an object to provide a semiconductor display device having a touch panel, which can reduce power consumption. The semiconductor display device includes a panel which is provided with a pixel portion and a driver circuit which controls an input of the image signal to the pixel portion, and a touch panel provided in a position overlapping with the panel in the pixel portion. The pixel portion includes a display element configured to perform display in accordance with voltage of the image signal to be input, and a transistor configured to control retention of the voltage. The transistor includes an oxide semiconductor in a channel formation region. The driving frequency of the driver circuit, that is, the number of writing operations of the image signal for a certain period is changed in accordance with an operation signal from a touch panel.

Claims

1. A semiconductor display device comprising:

a panel including a pixel portion and a driver circuit, the driver circuit being configured to input an image signal to the pixel portion when a driving signal and a power supply potential are supplied, and being configured to stop an input of the image signal to the pixel portion when supply of the driving signal and the power supply potential is stopped;

a touch panel overlapping with the pixel portion;

a CPU configured to select whether or not the driving signal and the power supply potential are supplied to the driver circuit in accordance with an operation signal from the touch panel; and

a display control circuit configured to control the supply of the driving signal and the power supply potential to the driver circuit in accordance with an instruction from the CPU,

wherein the pixel portion comprises a display element configured to perform display in accordance with voltage of the image signal, and a transistor configured to control retention of the voltage, and

wherein the transistor includes a semiconductor material whose band gap is wider than a band gap of silicon and whose intrinsic carrier density is lower than intrinsic carrier density of silicon in a channel formation region.

2. The semiconductor display device according to claim 1,

wherein the driver circuit comprises a shift register, and

wherein the driving signal is a start signal and a clock signal.

3. The semiconductor display device according to claim 1, wherein the semiconductor material is an oxide semiconductor.

4. The semiconductor display device according to claim 3, wherein the oxide semiconductor is an In—

Ga—

Zn—

O-based oxide semiconductor.

5. The semiconductor display device according to claim 3, wherein concentration of hydrogen in the oxide semiconductor is less than or equal to 5×

10¹⁹/CM³.

6. The semiconductor display device according to claim 1, wherein off-state current density of the transistor is less than or equal to 100 zA/μ

m.

7. A semiconductor display device comprising:

a panel including a pixel, a pixel portion including a photosensor, and a driver circuit, the driver circuit being configured to input an image signal to the pixel portion when a driving signal and a power supply potential are supplied, and being configured to stop an input of the image signal to the pixel portion when supply of the driving signal and the power supply potential is stopped;

a CPU configured to select whether or not the driving signal and the power supply potential are supplied to the driver circuit in accordance with an operation signal from the photosensor; and

a display control circuit configured to control the supply of the driving signal and the power supply potential to the driver circuit in accordance with an instruction from the CPU,

wherein the pixel comprises a display element configured to perform display in accordance with voltage of the image signal, and a transistor configured to control retention of the voltage, and

wherein the transistor includes a semiconductor material whose band gap is wider than a band gap of silicon and whose intrinsic carrier density is lower than intrinsic carrier density of silicon in a channel formation region.

8. The semiconductor display device according to claim 7,

wherein the driver circuit comprises a shift register, and

wherein the driving signal is a start signal and a clock signal.

9. The semiconductor display device according to claim 7, wherein the semiconductor material is an oxide semiconductor.

10. The semiconductor display device according to claim 9, wherein the oxide semiconductor is an In—

Ga—

Zn—

O-based oxide semiconductor.

11. The semiconductor display device according to claim 9, wherein concentration of hydrogen in the oxide semiconductor is less than or equal to 5×

10¹⁹/cm³.

12. The semiconductor display device according to claim 7, wherein off-state current density of the transistor is less than or equal to 100 zA/μ

m.

13. A driving method of a semiconductor display device, comprising the steps of:

changing the number of writing operations of an image signal to a pixel portion for a certain period in accordance with an operation signal from a touch panel;

performing display by a display element in accordance with voltage of the image signal when the image signal is written to the pixel portion; and

maintaining the display of the display element by holding the voltage of the image signal by a transistor including a semiconductor material whose band gap is wider than a band gap of silicon and whose intrinsic carrier density is lower than intrinsic carrier density of silicon in a channel formation region.

14. The driving method of the semiconductor display device, according to claim 13, wherein the semiconductor material is an oxide semiconductor.

15. The driving method of the semiconductor display device, according to claim 14, wherein the oxide semiconductor is an In—

Ga—

Zn—

O-based oxide semiconductor.

16. The driving method of the semiconductor display device, according to claim 14, wherein concentration of hydrogen in the oxide semiconductor is less than or equal to 5×

10¹⁹/cm³.

17. The driving method of the semiconductor display device, according to claim 13, wherein off-state current density of the transistor is less than or equal to 100 zA/μ

m.

18. A driving method of a semiconductor display device, comprising the steps of:

changing the number of writing operations of an image signal to a pixel portion for a certain period in accordance with an operation signal from a photosensor;

performing display by a display element in accordance with voltage of the image signal when the image signal is written to the pixel portion; and

maintaining the display of the display element by holding the voltage of the image signal by a transistor including a semiconductor material whose band gap is wider than a band gap of silicon and whose intrinsic carrier density is lower than intrinsic carrier density of silicon in a channel formation region.

19. The driving method of the semiconductor display device, according to claim 18, wherein the semiconductor material is an oxide semiconductor.

20. The driving method of the semiconductor display device, according to claim 19, wherein the oxide semiconductor is an In—

Ga—

Zn—

O-based oxide semiconductor.

21. The driving method of the semiconductor display device, according to claim 19, wherein concentration of hydrogen in the oxide semiconductor is less than or equal to 5×

10¹⁹/cm³.

22. The driving method of the semiconductor display device, according to claim 18, wherein off-state current density of the transistor is less than or equal to 100 zA/μ

m.