Semiconductor device and method of driving the same

• US 9,916,793 B2
• Filed: 05/16/2013
• Issued: 03/13/2018
• Est. Priority Date: 06/01/2012
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kozuma, Munehiro, Ikeda, Takayuki, Kurokawa, Yoshiyuki, Tamura, Hikaru, Aoki, Takeshi
• Primary Examiner(s): Hong, Richard
• Application Number:
  US13/895,568
• Publication Number:
  US 20130321366A1
• Time in Patent Office: 1,762 Days
• Field of Search: 345204
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G09G 3/34 by control of light from an independent source

Abstract

To reduce the effect of external light and to improve the accuracy of detecting the location of a touch. In an image-capture period, light emission from a self-light-emitting element is controlled, and imaging data at the time of displaying white on a display screen and imaging data at the time of displaying black on the display screen are output from each sensor pixel. The location of a sensor pixel where a difference between the two pieces of imaging data output from the same sensor pixel is the greatest is detected. Thus, the location of a touch of the object on the display screen is detected with high accuracy. By utilizing a difference between imaging data at the time of reverse display, the effect of external light can be reduced.

Claims

1. A semiconductor device comprising:

a display pixel comprising;

a first transistor;

a second transistor;

a light-emitting element;

a first display pixel control signal line; and

a second display pixel control signal line, and

a sensor pixel comprising;

a third transistor;

a fourth transistor;

a light-receiving element;

a capacitor;

a first image-capture pixel control signal line; and

a second image-capture pixel control signal line,

wherein a gate terminal of the first transistor and the first display pixel control signal line are electrically connected to each other,

wherein a gate terminal of the second transistor and the second display pixel control signal line are electrically connected to each other,

wherein a gate terminal of the third transistor and the first image-capture pixel control signal line are electrically connected to each other,

wherein a gate terminal of the fourth transistor and the second image-capture pixel control signal line are electrically connected to each other,

wherein one of a source terminal and a drain terminal of the first transistor and the light-emitting element are electrically connected to each other at a first node,

wherein one of a source terminal and a drain terminal of the second transistor and the light-emitting element are electrically connected to each other at the first node,

wherein one of a source terminal and a drain terminal of the third transistor and the light-receiving element are electrically connected to each other,

wherein one of a source terminal and a drain terminal of the fourth transistor and another of the source terminal and the drain terminal of the third transistor are directly connected to each other,

wherein a first electrode of the capacitor is directly connected to the one of the source terminal and the drain terminal of the fourth transistor, and

wherein a second electrode of the capacitor is directly connected to another of the source terminal and the drain terminal of the fourth transistor.

2. The semiconductor device according to claim 1, wherein the first transistor, the second transistor, and the third transistor each comprise an oxide semiconductor layer.

3. The semiconductor device according to claim 2, wherein the oxide semiconductor layer includes indium, gallium, and zinc.

4. The semiconductor device according to claim 2, wherein the oxide semiconductor layer includes a c-axis aligned crystal.

5. The semiconductor device according to claim 1, wherein the third transistor overlaps with the light-emitting element.

6. The semiconductor device according to claim 1, wherein a plurality of display pixels is provided with respect to one sensor pixel.

7. The semiconductor device according to claim 1, wherein the semiconductor device is a touch panel.

8. The semiconductor device according to claim 1, wherein the semiconductor device is a portable information terminal.

9. A method for driving a semiconductor device, the semiconductor device comprising a touch panel comprising a plurality of display pixels and a plurality of sensor pixels, comprising:

obtaining a first imaging data by using the sensor pixels in a first period where white is displayed on a display screen of the touch panel;

obtaining a second imaging data by using the sensor pixels in a second period where black is displayed on the display screen of the touch panel; and

detecting a sensor pixel where a difference between the first imaging data and the second imaging data is greatest,

wherein the plurality of display pixels each comprise a first transistor and a second transistor,

wherein the plurality of sensor pixels each comprise a third transistor, a fourth transistor, and a capacitor,

wherein a gate terminal of the third transistor is electrically connected to a first image-capture pixel control signal line,

wherein a gate terminal of the fourth transistor is electrically connected to a second image-capture pixel control signal line,

wherein one of a source terminal and a drain terminal of the third transistor and one of a source terminal and a drain terminal of the fourth transistor are directly connected to each other,

wherein a first electrode of the capacitor is directly connected to the one of the source terminal and the drain terminal of the fourth transistor,

wherein a second electrode of the capacitor is directly connected to another of the source terminal and the drain terminal of the fourth transistor, and

wherein, in the first period and the second period, a first high potential is applied to the first image-capture pixel control signal line, and a first low potential is applied to the second image-capture pixel control signal line.

10. The method for driving a semiconductor device according to claim 9,

wherein a gate terminal of the first transistor is electrically connected to a first display pixel control signal line,

wherein a gate terminal of the second transistor is electrically connected to a second display pixel control signal line,

wherein, in the first period, a second low potential is applied to the first display pixel control signal line, and a second high potential is applied to the second display control signal line, and

wherein, in the second period, the second low potential is applied to the first display pixel control signal line, and a third low potential is applied to the second display control signal line.

11. The method for driving a semiconductor device according to claim 9, further comprising:

displaying a still image or a moving image by input of a video signal potential to the plurality of display pixels between the first period and the second period.

12. The method for driving a semiconductor device according to claim 9, wherein the plurality of display pixels each comprise a light-emitting element.

13. The method for driving a semiconductor device according to claim 9, wherein the plurality of sensor pixels each comprise a light-receiving element.

14. The method for driving a semiconductor device according to claim 9, wherein the semiconductor device is a portable information terminal.