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

• US 20110316809A1
• Filed: 12/29/2010
• Published: 12/29/2011
• Est. Priority Date: 06/25/2010
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Kim, Cheol-Se, Jung, Ji-Hyun
• Granted Patent: US 8,749,515 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 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0443 with several sub-pixels for the same colour in a pixel, not specifically used to display gradations G09G3/364 takes precedence
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

A liquid crystal display device having a touch sensor embedded therein is disclosed. The present invention includes a liquid crystal layer between first and second substrates, a pixel on the second substrate to apply a horizontal electric field to the liquid crystal layer, a touch sensor on the second substrate, the touch sensor detecting a touch by forming a touch capacitor with a touch object for touching the first substrate, and a readout line outputting a sensing signal from the touch sensor. The touch sensor includes a sensing electrode on the second substrate to form the sensing capacitor with the touch object, first and second sensor gate lines, a first sensor thin film transistor supplying a sensing driving voltage to the sensing electrode in response to a control of the first sensor gate line, and a second sensor thin film transistor supplying electric charges of the sensing electrode as the sensing signal in response to a control of the second sensor gate line.

Claims

1. A touch sensor embedded liquid crystal display device comprising:

a liquid crystal layer between first and second substrates;

a pixel provided for each pixel area of the second substrate to apply a horizontal electric field to the liquid crystal layer in the pixel area using a pixel electrode supplied with a data signal via a thin film transistor connected to gate and data lines and a common electrode connected to a common line;

a touch sensor provided for each space between one group of pixels and another group of pixels on the second substrate, the touch sensor detecting a touch by forming a touch capacitor with a touch object for touching the first substrate; and

a readout line outputting a sensing signal from the touch sensor,

wherein the touch sensor comprises a sensing electrode provided to the second substrate to form the sensing capacitor with the touch object, first and second sensor gate lines, a first sensor thin film transistor supplying a sensing driving voltage to the sensing electrode in response to a control of the first sensor gate line, and a second sensor thin film transistor supplying electric charges of the sensing electrode as the sensing signal in response to a control of the second sensor gate line.

2. The touch sensor embedded liquid crystal display device of claim 1, wherein the first and second sensor gate lines are sequentially driven.

3. The touch sensor embedded liquid crystal display device of claim 1, wherein a size of the sensing signal is proportional to the capacitance (Cf) of the sensing capacitor.

4. The touch sensor embedded liquid crystal display device of claim 1, wherein the sensing signal is proportional to a sum (Cf+Cpara) of the capacitance (Cf) of the sensing capacitor and a parasitic electrostatic capacitance (Cpara) of the sensing electrode and a voltage difference (Vd−

Vref) between the sensing driving voltage supplied to the sensing electrode and a reference voltage supplied to the readout line.

5. The touch sensor embedded liquid crystal display device of claim 1, wherein the sensing electrode and the first and second sensor gate lines are formed of the same gate metal of the gate line or the sensing electrode is formed of the same metal of the common electrode or the pixel electrode.

6. The touch sensor embedded liquid crystal display device of claim 1, wherein the first sensor thin film transistor includes a gate electrode connected to the first sensor gate line, a source electrode connected to a power line or the common line and a drain electrode connected to the sensing electrode and wherein the second sensor thin film transistor includes a gate electrode connected to the second sensor gate line, a source electrode connected to the readout line and a drain electrode connected to the sensing electrode.

7. The touch sensor embedded liquid crystal display device of claim 1, wherein the sensing electrode is independently formed by a unit of the touch sensor, wherein the readout line is formed in parallel with the data line by leaving a plurality of data lines in-between to be connected to a plurality of touch sensors arranged in length direction, and wherein the first and second sensor gate lines are formed in parallel with the gate line to be connected to a plurality of touch sensors arranged in width direction.

8. The touch sensor embedded liquid crystal display device of claim 7, wherein each of the first and second sensor gate lines is connected in common to at least one of other first and second sensor gate lines.

9. The touch sensor embedded liquid crystal display device of claim 2, further comprising:

a gate driver driving the gate line;

a data driver driving the data line;

a readout circuit detecting the touch using the sensing signal outputted from the readout line, the readout circuit detecting a position of the touch based on position information of the readout line and the first and second sensor gate lines; and

a sensor gate driver driving the first and second sensor gate lines.

10. The touch sensor embedded liquid crystal display device of claim 9, wherein the readout circuit is built in the data driver and wherein the sensor gate driver is built in the gate driver.

11. The touch sensor embedded liquid crystal display device of claim 9, wherein the gate and data drivers drive the gate and data lines in a data write interval, respectively and wherein the sensor gate driver drives the first and second sensor gate lines in a touch sensing interval.

12. The touch sensor embedded liquid crystal display device of claim 11, wherein a frame is divided into the data write interval and the touch sensing interval.

13. The touch sensor embedded liquid crystal display device of claim 11, wherein a frame is divided into a plurality of horizontal interval units to enable the data write interval and the touch sensing interval to alternate with each other in each horizontal interval.

14. A method of driving a liquid crystal display device, in which a touch sensor is embedded, comprising the steps of:

storing data in a plurality of pixels by driving gate and data lines in a data write interval;

applying a horizontal electric field according to data to a liquid crystal layer of each pixel; and

detecting a touch according to an electrostatic capacitance formed between a touch object touching a top substrate of the liquid crystal display device and the touch sensor by driving the touch sensor provided to each space between one group of pixels and another group of pixels,

the touch detecting step comprising the steps of;

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

outputting electric charges of the sensing electrode generated from the touch detection to a readout line as a sensing signal.

15. The method of claim 14, wherein a frame is divided into the data write interval and the touch sensing interval.

16. The method of claim 14, wherein a frame is divided into a plurality of horizontal interval units to enable the data write interval and the touch sensing interval to alternate with each other in each horizontal interval.

17. A method of fabricating a touch sensor embedded liquid crystal display device, comprising the steps of:

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

forming a common electrode connected to the common line;

forming a gate insulating layer on the substrate having the gate metal pattern and the common electrode formed thereon;

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

forming a data metal pattern including source and drain electrodes of the pixel and first and second sensor thin film transistors on the gate insulating layer having the semiconductor layers formed thereon together with a data line, a power line and a readout line;

forming a passivation layer to cover the data metal pattern;

forming a plurality of contact holes in the passivation layer;

forming a pixel electrode on the passivation layer to be connected to the drain electrode of the pixel thin film transistor via the contact hole to form a horizontal electric field with the common electrode; and

forming a sensing electrode together with the gate line, the common electrode, or the pixel electrode.

18. The method of claim 17, wherein the gate, source and drain electrodes of the first sensor thin film transistor are connected to the first sensor gate line, the power line and one end portion of the sensing electrode, respectively and wherein the gate, source and drain electrodes of the second sensor thin film transistor are connected to the second sensor gate line, the readout line and the other end portion of the sensing electrode, respectively.

19. The method of claim 17, wherein the sensing electrode is independently formed for each touch sensor, wherein the readout line and the power line are formed in parallel with the data line by leaving a plurality of data lines in-between to be connected to a plurality of touch sensors arranged in length direction, and wherein the first and second sensor gate lines are formed in parallel with the gate line to be connected to a plurality of touch sensors arranged in width direction.