DISPLAY DEVICE

• US 20120092302A1
• Filed: 02/26/2010
• Published: 04/19/2012
• Est. Priority Date: 06/25/2009
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Imai, Hajime, Watanabe, Takuya, Murai, Atsuhito, Kitagawa, Hideki
• Granted Patent: US 8,749,528 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• 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 3/3225 using an active matrix
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 31/03682 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/03762 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/1136 the device being a metal-insulator-semiconductor field-effect transistor
• CPC Class Codes: H10K 59/13 comprising photosensors that control luminance
• CPC Class Codes: Y02E 10/546 Polycrystalline silicon PV cells
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells

Abstract

It is an object of the present invention to provide a display device equipped with a display panel that is provided with a photo-detection section with improved accuracy of detecting a touch position. A display panel (11) of an organic EL display device (10) includes a photo-detection section (40) that detects reflected light when a screen is touched by a finger or the like. The photo-detection section (40) includes a photodiode (41) that receives the reflected light, and an output amplifier (42) that outputs an output voltage corresponding to the amount of the received light. If an a-Si diode is used for such a photodiode (41), a sufficiently large signal difference in sensitivity between the bright state and the dark state can be achieved. Also, if a p-Si amplifier is used for the output amplifier (42), the output voltage becomes the saturation voltage at the time of read-out. This allows the p-Si amplifier to directly output the large sensitivity difference detected by the a-Si diode as a large difference in the output voltage.

Claims

1. A display device that is capable of detecting a touch position, comprising:

a display panel including a plurality of image display sections that display an image at a brightness corresponding to image data, and a plurality of photo-detection sections that generate a signal corresponding to an amount of received light;

a display driver circuit that writes a signal corresponding to the image data in the image display sections; and

a sensor driver circuit that reads the signal corresponding to the amount of the received light from the photo-detection sections,

wherein each of the photo-detection sections includes a photodiode that generates electric charges corresponding to an incident light amount, a capacitor that accumulates the electric charges generated in the photodiode and that retains a voltage corresponding to the accumulated electric charge amount, and a thin film transistor that outputs an output signal based on the voltage retained by the capacitor,

wherein the photodiode is made of a semiconductor film having a higher photosensitivity than that of a semiconductor film included in the thin film transistor, and

wherein the thin film transistor is made of a semiconductor film having a higher mobility than that of the semiconductor film included in the photodiode.

2. The display device according to claim 1, wherein the semiconductor film included in the photodiode is an amorphous semiconductor film, and

wherein the semiconductor film included in the thin film transistor is a polycrystalline semiconductor film.

3. The display device according to claim 1, wherein said display panel comprises a first substrate and a second substrate that are bonded to face each other,

wherein the thin film transistor is formed on the first substrate and the photodiode is formed on the second substrate, and

wherein the thin film transistor and the photodiode are electrically connected by a conductive connecting member formed between the first substrate and the second substrate.

4. The display device according to claim 3, wherein the connecting member comprises a columnar portion made of an insulating material and a first conductive film formed on a surface of the columnar portion, and

wherein the columnar portion maintains a predetermined spacing between the first substrate and the second substrate by its height.

5. The display device according to claim 1, wherein said image display section comprises a display element, part of which is formed of a second conductive film made of a same material as that of the first conductive film.

6. The display device according to claim 1, wherein the image display section comprises three sub-pixels that display images in red, green, and blue, respectively, and

wherein the three sub-pixels respectively include said photodiode, said thin film transistor, and said capacitor.

7. The display device according to claim 1, wherein the photodiode is a thin film transistor in which a control terminal and one conductive terminal constitute an anode terminal and the other conductive terminal is a cathode terminal.

8. The display device according to claim 1, wherein said display panel is an organic EL display panel.

9. The display device according to claim 1, wherein said display panel is a liquid crystal display panel.