LIQUID CRYSTAL DISPLAY DEVICE HAVING TOUCH SENSOR EMBEDDED THEREIN, METHOD FOR DRIVING THE SAME, AND METHOD FOR FABRICATING THE SAME

• US 20120038585A1
• Filed: 12/29/2010
• Published: 02/16/2012
• Est. Priority Date: 08/10/2010
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: KIM, CHEOL-SE
• Granted Patent: US 8,553,013 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: H01L 27/1259 Multistep manufacturing methods

Abstract

Disclosed is a liquid crystal display device having touch sensors embedded therein. The liquid crystal display device includes a liquid crystal layer interposed between upper and lower substrates, pixels, each of which includes pixel and common electrodes applying a horizontal electric field to the liquid crystal layer, a pixel thin film transistor to drive the pixel electrode, and a common thin film transistor to drive the common electrode, touch sensors, each of which forms a sensing capacitor between an object and the common electrode, sensor power lines, readout lines, and sensor gate lines. Each touch sensor includes the common electrode, a first sensor thin film transistor charging the common electrode with the sensing driving voltage in response to control of the previous sensor gate line, and a second sensor thin film transistor outputting the sensing signal to the readout line in response to control of the current sensor gate line.

Claims

1. A liquid crystal display comprising:

a liquid crystal layer interposed between upper and lower substrates;

a plurality of pixels, respectively formed in pixel regions of the lower substrate, each of the plurality of pixels including a pixel electrode and a common electrode applying a horizontal electric field to the liquid crystal layer, a pixel thin film transistor connected with a gate line and a data line to drive the pixel electrode, and a common thin film transistor connected with the gate line and a common line to drive the common electrode;

touch sensors, each forming a sensing capacitor between an object touching the upper substrate and the common electrode to sense touch and then to output a sensing signal;

sensor power lines to supply sensing driving voltage to the respective touch sensors;

readout lines to output the sensing signal from the respective touch sensors; and

sensor gate lines formed parallel with gate lines, wherein each of the touch sensors includes;

the common electrode formed in plural pixels;

a first sensor thin film transistor to charge the common electrode with the sensing driving voltage from the corresponding sensor power line in response to control of the previous sensor gate line; and

a second sensor thin film transistor to output the sensing signal from the common electrode to the corresponding readout line in response to control of the current sensor gate line.

2. The liquid crystal display device according to claim 1, wherein during touch sensing, the first sensor thin film transistor charges the common electrode with the sensing driving voltage, and then the second sensor thin film transistor outputs the sensing signal from the common electrode to the corresponding readout line.

3. The liquid crystal display device according to claim 1, wherein the first and second sensing thin film transistors are formed in pixels located at both ends among the plurality of pixels in which each of the touch sensors is formed.

4. The liquid crystal display device according to claim 1, wherein:

each sensor power line and each readout line are formed in parallel with the data lines under the condition that each touch sensor is formed between each sensor power line and each readout line, and are connected in common to plural touch sensors arranged in the vertical direction; and

each sensor gate line is connected in common to plural touch sensors arranged in the horizontal direction.

5. The liquid crystal display device according to claim 1, wherein:

the pixel thin film transistor includes a gate electrode connected with the gate line, a source electrode connected with the data line, and a drain electrode connected with the pixel electrode;

the common thin film transistor includes a gate electrode connected with the same gate line as the pixel thin film transistor, a source electrode connected with the common line, and a drain electrode connected with the common electrode;

the first sensor thin film transistor includes a gate electrode connected with the previous sensor gate line, a source electrode connected with the corresponding sensor power line, and a drain electrode connected with one terminal of the common electrode; and

the second sensor thin film transistor includes a gate electrode connected with the current sensor gate line, a source electrode connected with the corresponding readout line, and a drain electrode connected with the other terminal of the common electrode.

6. The liquid crystal display device according to claim 5, wherein the common electrode is connected with the drain electrode of the common thin film transistor through a first contact hole penetrating a first insulating layer, and is respectively connected with the drain electrodes of the first and second sensor thin film transistors through second and third contact holes penetrating the first insulating layer.

7. The liquid crystal display device according to claim 6, wherein:

the source electrode of the common thin film transistor is overlapped with the common line under the condition that a second insulating layer is interposed between the source electrode of the common thin film transistor and the common line, and a first contact electrode to connect the source electrode of the common thin film transistor and the common line through a fourth contact hole penetrating the first insulating layer and the second insulating layer is further provided at the overlapped portion; and

a second contact electrode to connect the gate electrode of the second sensor thin film transistor and the corresponding sensor gate line is further provided, and the second contact electrode is respectively connected to the gate electrode of the second sensor thin film transistor and the corresponding sensor gate line through fifth and sixth contact holes penetrating the first and second insulating layers.

8. The liquid crystal display device according to claim 1, wherein the common electrode is independently formed in the unit of each touch sensor including the plurality of pixels, and is used as a common electrode to drive the liquid crystal layer during data recording and used as a sensing electrode to form the sensing capacitor during touch sensing.

9. The liquid crystal display device according to claim 8, wherein the common thin film transistor in each pixel is connected with the same gate line as the pixel thin film transistor, and is turned on simultaneously with the pixel thin film transistor and thus supplies common voltage from the common line to the common electrode during data recording.

10. The liquid crystal display device according to claim 1, wherein the sensing signal is proportional to capacitance of the sensing capacitor and a difference between the sensing driving voltage and reference voltage supplied to the corresponding readout line, respectively.

11. The liquid crystal display device according to claim 1, wherein each sensor gate line is connected in common to at least one sensor gate line.

12. The liquid crystal display device according to claim 1, further comprising:

a gate driver to drive the gate lines;

data drivers to drive the data lines;

a readout circuit to sense the touch using the sensing signal output from the corresponding readout line and to sense a touch position based on position data of the corresponding readout line and the corresponding sensor gate line; and

a sensor gate driver to drive the sensor gate lines.

13. The liquid crystal display device according to claim 12, wherein the readout circuit is embedded in the data drivers, or the sensor gate driver is embedded in the gate driver or is separately formed at a position opposite to the gate driver.

14. The liquid crystal display device according to claim 12, wherein:

the gate driver and the data drivers respectively drive the gate lines and the data lines during a data recording period; and

the sensor gate driver and the readout circuit respectively drive the sensor gate lines and the readout line during a touch sensing period.

15. The liquid crystal display device according to claim 1, wherein one frame is divided into a data recording period and a touch sensing period.

16. The liquid crystal display device according to claim 15, wherein the frame is divided into a plurality of horizontal periods and the data recording period and the touch sensing period are alternated every horizontal period.

17. The liquid crystal display device according to claim 1, wherein the liquid crystal layer is driven in an IPS mode or an FFS mode.

18. A liquid crystal display device having touch sensors embedded therein, comprising:

a liquid crystal layer interposed between upper and lower substrates;

a plurality of pixels, respectively formed in pixel regions of the lower substrate, each of the plurality of pixels including a pixel electrode and a common electrode applying a horizontal electric field to the liquid crystal layer, a pixel thin film transistor connected with a gate line and a data line to drive the pixel electrode, and a common thin film transistor connected with the gate line and a common line to drive the common electrode;

touch sensors, each forming a sensing capacitor between an object touching the upper substrate and the common electrode to sense touch and then to output a sensing signal;

readout lines to supply sensing driving voltage to the touch sensors and to output the sensing signal from the respective touch sensors; and

sensor gate lines formed in parallel with gate lines, wherein each of the touch sensors includes;

the common electrode formed in plural pixels; and

a sensor thin film transistor to charge the common electrode with the sensing driving voltage from the corresponding readout line and then to output the sensing signal from the common electrode to the corresponding readout line in response to control of the corresponding sensor gate line.

19. The liquid crystal display device according to claim 18, wherein during touch sensing, the sensor thin film transistor charges the common electrode with the sensing driving voltage in response to a first gate pulse supplied to the corresponding sensor gate line, and then outputs the sensing signal from the common electrode to the corresponding readout line in response to a second gate pulse supplied to the corresponding sensor gate line.

20. The liquid crystal display device according to claim 19, wherein during touch sensing, the sensing driving voltage is supplied to the corresponding readout line during a period of time in which the first gate pulse is supplied, and reference voltage that is lower than the sensing driving voltage is supplied to the corresponding readout line during the remaining period of time.

21. The liquid crystal display device according to claim 18, wherein:

the read out lines are formed in parallel with the data lines under the condition that each touch sensor is formed between the readout lines, and each readout line is connected in common to plural touch sensors arranged in the vertical direction; and

each sensor gate line is connected in common to plural touch sensors arranged in the horizontal direction.

22. The liquid crystal display device according to claim 18, wherein:

the pixel thin film transistor includes a gate electrode connected with the gate line, a source electrode connected with the data line, and a drain electrode connected with the pixel electrode;

the common thin film transistor includes a gate electrode connected with the same gate line as the pixel thin film transistor, a source electrode connected with the common line, and a drain electrode connected with the common electrode; and

the sensor thin film transistor includes a gate electrode connected with the corresponding sensor gate line, a source electrode connected with the corresponding readout line, and a drain electrode connected with one terminal of the common electrode.

23. The liquid crystal display device according to claim 18, wherein the common electrode is independently formed in the unit of each touch sensor including the plurality of pixels, and is used as a common electrode to drive the liquid crystal layer during data recording and used as a sensing electrode to form the sensing capacitor during touch sensing.

24. The liquid crystal display device according to claim 23, wherein the common thin film transistor in each pixel is connected with the same gate line as the pixel thin film transistor, and is turned on simultaneously with the pixel thin film transistor and thus supplies common voltage from the common line to the common electrode during data recording.

25. The liquid crystal display device according to claim 18, wherein the sensing signal is proportional to capacitance of the sensing capacitor and a difference between the sensing driving voltage and reference voltage supplied to the corresponding readout line, respectively.

26. The liquid crystal display device according to claim 18, wherein each sensor gate line is connected in common to at least one sensor gate line.

27. The liquid crystal display device according to claim 18, further comprising:

a gate driver to drive the gate lines;

data drivers to drive the data lines;

a readout circuit to sequentially supply the sensing driving voltage and reference voltage to the corresponding readout line, to sense the touch using the sensing signal output from the corresponding readout line, and to sense a touch position based on position data of the corresponding readout line and the corresponding sensor gate line, during touch sensing; and

a sensor gate driver to drive the sensor gate lines.

28. The liquid crystal display device according to claim 27, wherein the readout circuit is embedded in the data drivers, or the sensor gate driver is embedded in the gate driver or is separately formed at a position opposite to the gate driver.

29. The liquid crystal display device according to claim 27, wherein:

the gate driver and the data drivers respectively drive the gate lines and the data lines during a data recording period; and

the sensor gate driver and the readout circuit respectively drive the sensor gate lines and the readout line during a touch sensing period.

30. The liquid crystal display device according to claim 18, wherein one frame is divided into a data recording period and a touch sensing period.

31. The liquid crystal display device according to claim 30, wherein the frame is divided into a plurality of horizontal periods and the data recording period and the touch sensing period are alternated every horizontal period.

32. The liquid crystal display device according to claim 18, wherein the liquid crystal layer is driven in an IPS mode or an FFS mode.

33. A method for driving a liquid crystal display device having touch sensors embedded therein, comprising:

storing data in a plurality of pixels by driving gate lines and data lines, and applying horizontal electric fields based on the data to a liquid crystal layer using a pixel electrode and a common electrode of each pixel, during a data recording period; and

sensing touch through a touch sensor using a sensing capacitor formed between an object touching an upper substrate of the liquid crystal display device and the common electrode by driving the common electrode formed in the unit of plural pixels, during a touch sensing period, wherein the touch sensing through the touch sensor includes;

supplying sensing driving voltage from a sensor power line to the common electrode of the touch sensor by driving a first sensor thin film transistor of the touch sensor; and

outputting a sensing signal generated from the common electrode by the touch sensing to a readout line by driving a second sensor thin film transistor of the touch sensor.

34. The method according to claim 33, wherein one frame is divided into a plurality of horizontal periods and a data recording period and a touch sensing period are alternated every horizontal period.

35. A method for driving a liquid crystal display device having touch sensors embedded therein, comprising:

storing data in a plurality of pixels by driving gate lines and data lines, and applying horizontal electric fields based on the data to a liquid crystal layer using a pixel electrode and a common electrode of each pixel, during a data recording period; and

sensing touch through a touch sensor using a sensing capacitor formed between an object touching an upper substrate of the liquid crystal display device and the common electrode by driving the common electrode formed in the unit of plural pixels, during a touch sensing period, wherein the touch sensing through the touch sensor includes;

allowing a sensor thin film transistor of the touch sensor to supply sensing driving voltage from a readout line to the common electrode of the touch sensor in response to a first gate pulse supplied to a sensor gate line; and

allowing the sensor thin film transistor to output a sensing signal generated from the common electrode by the touch sensing to the readout line in response to a second gate pulse supplied to the sensor gate line.

36. The method according to claim 35, wherein the readout line supplies the sensing driving voltage during a period of time in which the first gate pulse is supplied, and supplies reference voltage that is lower than the sensing driving voltage during the remaining period of time.

37. The method according to claim 35, wherein one frame is divided into a plurality of horizontal periods and a data recording period and a touch sensing period are alternated every horizontal period.

38. A method for fabricating a liquid crystal display device having touch sensors embedded therein, comprising:

forming a gate metal pattern, including gate electrodes of pixel thin film transistors, common thin film transistors, and sensor thin film transistors together with gate lines, common lines, and sensor gate lines, on a substrate;

forming a gate insulating layer on the substrate provided with the gate metal pattern formed thereon;

forming semiconductor layers of the pixel thin film transistors, the common thin film transistors, and the sensor thin film transistors on the gate insulating layer;

forming a data metal pattern, including source electrodes and drain electrodes of the pixel thin film transistors, the common thin film transistors, and the sensor thin film transistors together with data lines and readout lines, on the gate insulating layer provided with the semiconductor layers formed thereon;

forming a passivation layer covering the data metal pattern, and forming a plurality of contact holes; and

forming pixel electrodes connected with the drain electrodes of the pixel thin film transistors, common electrodes connected with the drain electrodes of the common thin film transistors and the sensor thin film transistors, first contact electrodes to connect the source electrodes of the common thin film transistors and the common lines, and second contact electrodes to connect the gate electrodes of the sensor thin film transistors and the sensor gate lines, on the passivation layer, the connection of the electrodes being achieved through the plurality of contact holes.

39. The method according to claim 38, further comprising:

forming sensor power lines together with the data lines; and

forming second sensor thin film transistors, each of which is connected between the previous sensor gate line, each sensor power line, and each common line, together with the pixel thin film transistors, the common thin film transistors, and the sensor thin film transistors.

40. The method according to claim 38, wherein the pixel electrodes are independently formed in the unit of each pixel, and the common electrodes are independently formed in the unit of each touch sensor including plural pixels.

41. A method for fabricating a liquid crystal display device having touch sensors embedded therein, comprising:

forming a gate metal pattern, including gate electrodes of pixel thin film transistors, common thin film transistors, and sensor thin film transistors together with gate lines, common lines, and sensor gate lines, on a substrate;

forming a gate insulating layer on the substrate provided with the gate metal pattern formed thereon;

forming semiconductor layers of the pixel thin film transistors, the common thin film transistors, and the sensor thin film transistors on the gate insulating layer;

forming a data metal pattern, including source electrodes and drain electrodes of the pixel thin film transistors, the common thin film transistors, and the sensor thin film transistors together with data lines and readout lines, on the gate insulating layer provided with the semiconductor layers formed thereon;

forming pixel electrodes connected with the drain electrodes of the pixel thin film transistors on the gate insulating layer provided with the data metal pattern formed thereon;

forming a passivation layer covering the pixel electrodes, and forming a plurality of contact holes; and

forming common electrodes connected with the drain electrodes of the common thin film transistors and the sensor thin film transistors, first contact electrodes to connect the source electrodes of the common thin film transistors and the common lines, and second contact electrodes to connect the gate electrodes of the sensor thin film transistors and the sensor gate lines, on the passivation layer, the connection of the common electrodes, the first contact electrodes, and the second contact electrodes being achieved through the plurality of contact holes.

42. The method according to claim 41, further comprising:

forming sensor power lines together with the data lines; and

forming second sensor thin film transistors, each of which is connected between the previous sensor gate line, each sensor power line, and each common line, together with the pixel thin film transistors, the common thin film transistors, and the sensor thin film transistors.

43. The method according to claim 41, wherein the pixel electrodes are independently formed in the unit of each pixel, and the common electrodes are independently formed in the unit of each touch sensor including plural pixels.