Liquid crystal display device having touch sensor embedded therein, method of driving the same and method of fabricating the same

• US 8,749,515 B2
• Filed: 12/29/2010
• Issued: 06/10/2014
• 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
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): XAVIER, ANTONIO J
• Application Number:
  US12/980,855
• Publication Number:
  US 20110316809A1
• Time in Patent Office: 1,259 Days
• Field of Search: 438/10
• 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 a gate line and a data line 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 sensing 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,

wherein;

the first and second sensor gate lines are connected respectively to the first and second sensor thin film transistor, are separated from the gate line connected to the thin film transistor of the pixel, and are driven independently from the gate line,

the first sensor thin film transistor is connected to the second sensor thin film transistor through the sensing electrode,

the sensing electrode directly forms the sensing capacitor with the touch object, the sensing electrode being one electrode of the sensing capacitor and the touch object being the other electrode of the sensing capacitor, and

a length of the sensing electrode corresponds to a sum of widths of the pixels included in the one group.

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 lines 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 through a second sensor thin film transistor, wherein the first sensor thin film transistor is connected to the second sensor thin film transistor through the sensing electrode,

wherein;

first and second sensor gate lines are connected respectively to the first and second sensor thin film transistors, are separated from the gate lines connected to the thin film transistors of the pixels, and are driven independently from the gate lines,

the sensing electrode directly forms the sensing capacitor with the touch object, the sensing electrode being one electrode of the sensing capacitor and the touch object being the other electrode of the sensing capacitor, and

a length of the sensing electrode corresponds to a sum of widths of the pixels included in the one group.

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.