DISPLAY DEVICE INCLUDING OPTICAL SENSOR AND DRIVING METHOD THEREOF

• US 20110148835A1
• Filed: 12/09/2010
• Published: 06/23/2011
• Est. Priority Date: 12/18/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Granted Patent: US 9,087,489 B2
• Time in Patent Office: Days
• US Class Current: 345/207
• CPC Class Codes: G02F 1/13312 Circuits comprising photodetectors for purposes other than feedback
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2310/0202 Addressing of scan or signal lines
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• 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 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

An object is to provide a display device with low power consumption and good display quality. A first substrate is provided with a terminal portion, a pixel electrode, a switching transistor including an oxide semiconductor, a first optical sensor having high optical sensitivity to visible light, and a second optical sensor having optical sensitivity to infrared light and having lower optical sensitivity to visible light than the first optical sensor. The illuminance or color temperature around a display device is detected using the first and second optical sensors, and the luminance or color tone of a display image is adjusted. A second substrate is provided so as to face the first substrate, and is provided with a counter electrode. In a period for displaying a still image, the switching transistor is turned off so that the counter electrode is brought into a floating state.

Claims

1. A display device comprising:

a first substrate, wherein a terminal portion, a switching transistor, a first optical sensor, a second optical sensor, a pixel circuit including a plurality of pixels, and a driver circuit between the pixel circuit and a substrate edge are provided on the first substrate,

a second substrate provided with a counter electrode, the second substrate facing with the first substrate,

wherein the switching transistor includes an oxide semiconductor,

wherein the first optical sensor includes a first photoelectric conversion element including an amorphous semiconductor, and a first amplifier circuit,

wherein the second optical sensor includes a second photoelectric conversion element including a polycrystalline semiconductor, and a second amplifier circuit, and

wherein the counter electrode is electrically connected to the terminal portion through the switching transistor.

2. The display device according to claim 1, wherein the first photoelectric conversion element includes amorphous silicon.

3. The display device according to claim 1, wherein the second photoelectric conversion element includes polycrystalline silicon or microcrystalline silicon.

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

10¹⁴/cm³.

5. The display device according to claim 1, wherein the driver circuit includes a single crystal semiconductor.

6. The display device according to claim 1, wherein at least one of the first amplifier circuit and the second amplifier circuit have a transistor including an oxide semiconductor.

7. The display device according to claim 1, wherein the driver circuit is connected by a COG method, a wire bonding method, or a TAB method.

8. The display device according to claim 1, further comprising:

a wiring formed along the substrate edge,

wherein the wiring connects the switching transistor and the terminal portion.

9. The display device according to claim 1, wherein the counter electrode is in a floating state when the switching transistor is turned off.

10. The display device according to claim 1, wherein the display device is a liquid crystal display device.

11. A display device comprising:

a first substrate, wherein a terminal portion, a switching transistor, a first optical sensor, a second optical sensor, a pixel circuit including a plurality of pixels, and a gate line driver circuit between the pixel circuit and a first substrate edge, and a signal line driver circuit between the pixel circuit and a second substrate edge are provided on the first substrate,

a second substrate provided with a counter electrode, the second substrate facing with the first substrate,

wherein the switching transistor includes an oxide semiconductor,

wherein the first optical sensor includes a first photoelectric conversion element including an amorphous semiconductor, and a first amplifier circuit,

wherein the second optical sensor includes a second photoelectric conversion element including a polycrystalline semiconductor, and a second amplifier circuit, and

wherein the counter electrode is electrically connected to the terminal portion through the switching transistor.

12. The display device according to claim 11, wherein the first photoelectric conversion element includes amorphous silicon.

13. The display device according to claim 11, wherein the second photoelectric conversion element includes polycrystalline silicon or microcrystalline silicon.

14. The display device according to claim 11, wherein the oxide semiconductor has a carrier concentration of less than 1×

10¹⁴/cm³.

15. The display device according to claim 11, wherein each of the gate line driver circuit and the signal line driver circuit includes a single crystal semiconductor.

16. The display device according to claim 11, wherein at least one of the first amplifier circuit and the second amplifier circuit have a transistor including an oxide semiconductor.

17. The display device according to claim 11, wherein each of the gate line driver circuit and the signal line driver circuit is connected by a COG method, a wire bonding method, or a TAB method.

18. The display device according to claim 11, further comprising:

a wiring provided on the first substrate,

wherein a wiring connects the switching transistor and the terminal portion.

19. The display device according to claim 11, wherein the counter electrode is in a floating state when the switching transistor is turned off.

20. The display device according to claim 11, wherein the display device is a liquid crystal display device.

21. A method for driving a display device comprising a first substrate provided with a terminal portion, a pixel electrode, a switching transistor including, a first optical sensor, and a second optical sensor, and a second substrate provided with a counter electrode, the method comprising the steps of:

detecting an illuminance around the display device by using the first optical sensor and the second optical sensor; and

adjusting a luminance of a display image in accordance with the illuminance,

wherein the switching transistor includes an oxide semiconductor,

wherein the first optical sensor has maximum sensitivity at a wavelength of approximately 0.6 μ

m, and detects visible light,

wherein the second optical sensor has maximum sensitivity at a wavelength of approximately 0.7 μ

m, and detects visible light and infrared light,

wherein the second optical sensor has lower optical sensitivity to visible light than the first optical sensor, and

wherein a potential is supplied from the terminal portion to the counter electrode through the switching transistor.

22. The method for driving the display device according to claim 21, wherein the illuminance is detected by using the first optical sensor in the case where a signal which the first optical sensor outputs is not saturated, or by using the second optical sensor in the case where a signal which the first optical sensor outputs is saturated

23. The method for driving the display device according to claim 21, further comprising the step of:

detecting an infrared light illuminance around the display device with use of a difference between outputs of the first optical sensor and the second optical sensor.

24. The method for driving the display device according to claim 21, wherein the switching transistor is turned off in a period for displaying a still image so that the counter electrode is in a floating state.

25. A method for driving a display device comprising a first substrate provided with a terminal portion, a pixel electrode, a switching transistor including, a first optical sensor, and a second optical sensor, and a second substrate provided with a counter electrode, the method comprising the steps of:

detecting a color temperature around the display device by using the first optical sensor or the second optical sensor, and

correcting a color tone of a display image in accordance with the color temperature,

wherein the switching transistor includes an oxide semiconductor,

wherein the first optical sensor has maximum sensitivity at a wavelength of approximately 0.6 μ

m, and detects visible light,

wherein the second optical sensor has maximum sensitivity at a wavelength of approximately 0.7 μ

m, and detects visible light and infrared light,

wherein the second optical sensor has lower optical sensitivity to visible light than the first optical sensor, and

wherein a potential is supplied from the terminal portion to the counter electrode through the switching transistor.

26. The method for driving the display device according to claim 25, wherein the color temperature detected by using the first optical sensor in the case wherein a signal which the first optical sensor outputs is not saturated, or by using the second optical sensor in the case wherein a signal which the first optical sensor outputs is saturated.

27. The method for driving the display device according to claim 25, further comprising the step of:

detecting an infrared light color tone around the display device with use of a difference between outputs of the first optical sensor and the second optical sensor.

28. The method for driving a display device according to claim 25, wherein the switching transistor is turned off in a period for displaying a still image so that the counter electrode is in a floating state.