KR101147085B1 - Liquid crystal display device having touch sensor embedded therein - Google Patents

Abstract

The present invention discloses a liquid crystal display device with a built-in touch sensor that can simplify the structure of an embedded touch sensor.
A liquid crystal display device with a touch sensor according to the present invention includes: an upper substrate on which a color filter array is formed; A lower substrate on which the thin film transistor array is formed; A liquid crystal layer between the upper and lower substrates; A first column spacer for maintaining a cell gap between the upper and lower substrates; A second column spacer formed on the upper substrate at a lower height than the first column spacer and having a gap with the lower substrate; A floating electrode covering the second column spacer independently; A first sensor electrode and a second sensor electrode forming a touch capacitor, which serves as a touch sensor formed to overlap the floating electrode and the liquid crystal layer on the lower substrate, wherein the first sensor electrode is a gate line; The second sensor electrode is a lead out line or data line.

Description

Liquid crystal display with built-in touch sensor {LIQUID CRYSTAL DISPLAY DEVICE HAVING TOUCH SENSOR EMBEDDED THEREIN}

The present invention relates to a liquid crystal display device with a built-in touch sensor, and more particularly, to a liquid crystal display device with a built-in touch sensor that can minimize the reduction of the aperture ratio by simplifying the structure of the built-in touch sensor.

Today, a touch screen capable of inputting information by touch on screens of various display devices is widely applied as an information input device of a computer system. Since the touch screen moves or selects display information by simply touching the screen with a finger or a stylus, it can be easily used by anyone of all ages.

The touch screen detects the touch and the touch position generated on the display device screen to output touch information, and the computer system analyzes the touch information to perform a command. As the display device, a flat panel display device such as a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting diode (OLED) display, or the like is mainly used.

Touch screen technologies include resistive, capacitive, infrared, ultrasonic, and electromagnetic methods, depending on the sensing principle. Among these, the resistive film type and the capacitive type are widely used in view of manufacturing cost.

The resistive touch screen detects a touch by detecting a voltage change generated by contact between upper and lower resistive films (transparent conductive films) by touch pressure. However, the resistive touch screen has a disadvantage in that the touch screen or the display device is easily damaged by the touch pressure, and the transmittance is low due to the light scattering effect of the air layer between the resistive films.

The capacitive touch screen, which can compensate for the disadvantages of the resistive film, senses a touch by detecting a change in capacitance generated by a small amount of charge moving to a touch point when a conductor such as a human body or a stylus touches the touch. Capacitive touch screens are attracting attention because they can use tempered glass, which is not only durable, high transmittance, excellent touch sensing capability, and multi-touch.

In general, the touch screen is manufactured in the form of a panel and attached to an upper portion of the display device to perform a touch input function. However, since the display device with a touch panel needs to be manufactured separately from the display device and attached to the display device, the manufacturing cost increases and the thickness and weight of the entire system increase, resulting in poor mobility or limited design. There is a problem that follows.

In order to solve this problem, recently, a technology for embedding a capacitive touch sensor in a liquid crystal display has been developed. A capacitive touch sensor embedded in a liquid crystal display includes touch sensor pixels formed between a plurality of pixels. As shown in FIG. 1, each touch sensor pixel includes a common electrode 4 covering the sensor column spacer 3 formed on the upper substrate 2, a sensor electrode 7 formed on the lower substrate 6, and a common electrode. A touch sensor capacitor Ct formed of the liquid crystal layer 8 between the 4 and the sensor electrode 7 is provided. The sensor column spacer 3 is formed lower than the cell gap maintaining column spacer 5 so that the common electrode 4 and the sensor electrode 7 maintain a predetermined sensor gap. The touch capacitor Ct outputs a touch sensing signal by varying capacitance due to a change in a sensor gap according to a touch. For this purpose, the touch sensor pixel must have at least one thin film transistor (not shown) for supplying a driving signal to the sensor electrode 7 of the touch sensor capacitor Ct or for outputting a sensing signal from the sensor electrode 7.

Accordingly, the conventional embedded touch sensor has a problem in that the aperture ratio of the liquid crystal display is reduced due to the complicated structure of the touch sensor pixel. In addition, the conventional embedded touch sensor has a structure without an electrode on the upper substrate such as an in-plane switching (IPS) mode or a fringe field switching mode using a horizontal electric field by using the upper common electrode. There is a problem that is difficult to apply.

The present invention has been made to solve the above-mentioned problems of the prior art, the problem to be solved by the present invention is to provide a liquid crystal display device with a built-in touch sensor that can minimize the reduction of the aperture ratio by simplifying the structure of the built-in touch sensor will be.

Another object of the present invention is to provide a liquid crystal display device with a built-in touch sensor that can be applied to all liquid crystal driving modes using a vertical electric field and a horizontal electric field.

In order to solve the above problems, the liquid crystal display device with a touch sensor according to an embodiment of the present invention includes an upper substrate formed with a color filter array; A lower substrate on which the thin film transistor array is formed; A liquid crystal layer between the upper and lower substrates; A first column spacer for maintaining a cell gap between the upper and lower substrates; A second column spacer formed on the upper substrate at a lower height than the first column spacer and having a gap with the lower substrate; A floating electrode covering the second column spacer independently; First and second sensor electrodes are formed on the lower substrate to form a touch capacitor which serves as a touch sensor formed to overlap the floating electrode and the liquid crystal layer.

The touch capacitor has a structure in which a first touch capacitor formed between the first sensor electrode and the floating electrode and a second touch capacitor formed between the floating electrode and the second sensor electrode are connected in series.

A first sensor electrode is a gate line included in the thin film transistor array; The second sensor electrode is a readout line included in the thin film transistor array and intersects the gate line and the insulating layer therebetween; The floating electrode overlaps an intersection of the gate line and the readout line.

The present invention includes a gate driver for driving the gate line; A data driver for driving data lines included in the thin film transistor array; And a readout circuit for sensing a touch by inputting an output signal from the touch capacitor through the readout line.

The readout circuit includes an amplifier connected to the readout line; A capacitor connected between the input and output terminals of the amplifier; And a switch connected between the input and output terminals of the amplifier.

The amplifier may include the touch capacitor between the gate line and the lead-out line when the gate signal supplied to the gate line falls from the gate on voltage to the gate off voltage or rises from the gate off voltage to the gate on voltage. A touch signal is determined by outputting a sensing signal proportional to a capacitance change of.

The switch is turned off only during the output period of the sensing signal, and is turned on in the remaining period to initialize the readout line to the reference voltage.

The absolute value of the output voltage of the amplifier is proportional to the ratio of the capacitance of the touch capacitor and the capacitance of the capacitor of the readout circuit, and the difference voltage between the gate on voltage and the gate off voltage.

On the other hand, the first sensor electrode is a gate line included in the thin film transistor array; The second sensor electrode is a data line included in the thin film transistor array and intersects the gate line and the insulating layer therebetween; The floating electrode overlaps an intersection of the gate line and the data line.

The present invention includes a gate driver for driving the gate line; A data driver for driving data lines included in the thin film transistor array; And a readout circuit connected between the output terminal of the data line and a blocking capacitor, and configured to sense a touch by inputting an output signal from the touch capacitor through the data line.

The readout circuit includes an amplifier connected to an output terminal of the data line with the blocking capacitor interposed therebetween; A capacitor connected between the input and output terminals of the amplifier; And a switch connected between the input and output terminals of the amplifier.

The amplifier may be configured when the gate signal supplied to the gate line falls from the gate on voltage to the gate off voltage or when the gate signal rises from the gate off voltage to the gate on voltage. A touch signal is determined by outputting a sensing signal proportional to the capacitance change amount.

The data line includes a data writing period for supplying and storing data for each pixel; Time-divided and driven in a touch sensing period for supplying a signal corresponding to the amount of change in capacitance from the touch capacitor to the readout circuit; The switch is turned off only in the touch sensing period and turned on in the data writing period.

A common connection with the plurality of readout lines of the amplifier outputs a voltage corresponding to the sum of the output signals output from the plurality of readout lines.

The amplifier outputs the sum of the output voltages in time whenever the gate signal changes while a plurality of gate lines are driven.

According to an exemplary embodiment of the present invention, a liquid crystal display device having a touch sensor includes a touch capacitor Ct using an upper floating electrode overlapping a gate line and a data line or a gate line and a lead-out line to form a touch capacitor. It is possible to minimize the reduction of the aperture ratio of the liquid crystal display by being simple.

In addition, the liquid crystal display device having the touch sensor according to the present invention may be applied to both a vertical field type in which a common electrode is formed on an upper substrate as well as a horizontal field type liquid crystal display in which no common electrode is formed by using the upper floating electrode. .

1 is a schematic cross-sectional view of a liquid crystal display device having a conventional touch sensor.
2 is a vertical cross-sectional view of a horizontal electric field type liquid crystal display with a touch sensor according to an exemplary embodiment of the present invention.
3 is a vertical cross-sectional view of a vertical field type liquid crystal display with a touch sensor according to an embodiment of the present invention.
4 is an equivalent circuit diagram of a liquid crystal display with a touch sensor according to an exemplary embodiment of the present invention.
FIG. 5 is a driving waveform diagram of the liquid crystal display having the touch sensor illustrated in FIG. 1.
FIG. 6 is another driving waveform diagram of the liquid crystal display having the touch sensor illustrated in FIG. 1.
7 is an equivalent circuit diagram of a liquid crystal display with a touch sensor according to another embodiment of the present invention.
FIG. 8 is a driving waveform diagram of the liquid crystal display having the touch sensor illustrated in FIG. 7.

2 is a vertical cross-sectional view of a horizontal electric field type liquid crystal display with a touch sensor according to an exemplary embodiment of the present invention.

The horizontal field type liquid crystal display device having the touch sensor illustrated in FIG. 2 includes a liquid crystal layer 50 formed between the upper substrate 20 and the lower substrate 40, the upper and lower substrates 20 and 40, and the upper and lower substrates 20,. A first column spacer 28 maintaining a cell gap between the first and second cell spacers 40, a second column spacer 30 formed on the upper substrate 20 and having a predetermined gap with the lower substrate 40, and upper and lower substrates 20, respectively. A touch capacitor Ct formed of a touch sensor is provided between 40.

The upper substrate 20 includes a black matrix 22 defining each pixel, a color filter array including red, green, and blue color filters 24 corresponding to the pixels, and an overcoat layer 26 covering the color filter array. ), First and second column spacers 28 and 30 formed to have different heights in the overcoat layer 26, and a floating electrode 32 that individually covers the second column spacer 30. Since the first column spacer 28 is to maintain a cell gap between the upper and lower substrates 20 and 40, the first column spacer 28 is formed to contact the lower substrate 40. Since the second column spacer 32 is to form the touch capacitor Ct between the upper and lower substrates 40, the second column spacer 32 is formed at a lower height than the first column spacer 28 to have a gap with the lower substrate 40. The first and second column spacers 28 and 30 having different heights may be simultaneously formed by a photolithography process and an etching process using a halftone mask.

A thin film transistor array is formed on the lower substrate 40 to drive the liquid crystal layer 50 in the IPS mode or the FFS mode by applying a horizontal electric field to the liquid crystal layer 50 in each pixel unit. The thin film transistor array includes a thin film transistor (not shown) connected to a gate line GL and a data line DL intersecting each other with an insulating layer 43 interposed therebetween, and a pixel electrode supplied with a data signal through the thin film transistor. (Not shown) and a common electrode (not shown) supplied with a common voltage through a common line (not shown). In addition, the thin film transistor array may further include a readout line ROL parallel to the data line DL.

The touch capacitor Ct, which serves as a touch sensor, overlaps the floating electrode 32 with the floating electrode 32 and the first and second sensing electrodes 42 spaced apart from each other with the liquid crystal layer 50 interposed therebetween. 44). The gate line GL is used as the first sensing electrode 42, and the data line DL or the readout line ROL is used as the second sensing electrode 44. In other words, the floating electrode 32 on the upper substrate 20 intersects the gate line GL and the data line DL or the gate line GL on the lower substrate 40 with the liquid crystal layer 50 interposed therebetween. ) And a touch capacitor Ct are formed by overlapping the intersection region of the lead-out line ROL. The touch capacitor Ct includes the first touch capacitor Ct1 between the first sensing electrode 42 (gate line GL) and the floating electrode 32 electrode, and the second sensing electrode 44 (data line DL or readout line ROL). ) And the second touch capacitor Ct2 between the floating electrode 32 are connected in series.

The capacitance of the touch capacitor Ct is changed by decreasing the gap between the floating electrode 32 and the first and second sensing electrodes 42 and 44 according to the touch pressure at which the touch object touches the surface of the upper substrate 20. (Increase) to vary the sensing signal. The readout circuit reads the change (increase) of the sensing signal according to the capacitance variation of the touch capacitor Ct through the data line DL or the readout line ROL to detect whether the touch is performed. The sensing signal is output by the capacitive coupling phenomenon of the touch capacitor Ct whenever the gate voltage applied to the gate line GL varies.

The liquid crystal display further includes upper and lower polarizers attached to the outer surfaces of the upper and lower substrates 20 and 40 and the optical axes are perpendicular to each other, and upper and lower alignment layers formed on the inner surface in contact with the liquid crystal to set the pretilt angle of the liquid crystal.

3 is a vertical cross-sectional view of a vertical field type liquid crystal display with a touch sensor according to another embodiment of the present invention.

The vertical field type liquid crystal display device having the touch sensor illustrated in FIG. 3 is spaced apart from the floating electrode 32 covering the second column spacer 30 on the upper substrate 20 as compared to the horizontal field type liquid crystal display device illustrated in FIG. 1. The upper common electrode 36 is further formed to form a vertical electric field with the pixel electrode on the lower substrate 40 to drive the liquid crystal layer 50 in twisted nematic (TN) mode or vertical alignment (VA) mode. Since the same components are provided, descriptions of overlapping components will be omitted.

On the overcoat layer 26 having the first and second column spacers 28 and 30 having different heights, the upper common electrode 36 is commonly formed in the region except the second column spacer 30, and the second The floating electrode 32 spaced apart from the upper common electrode 36 while covering the column spacer 30 is independently formed for each second column spacer 30.

Accordingly, the first sensing electrode 42 (gate line GL) and the second sensing electrode 44 which overlap the floating electrode 32 and the floating electrode 32 and are spaced apart with the liquid crystal layer 50 interposed therebetween. A touch capacitor Ct is formed between the data line DL or the readout line ROL.

As such, the liquid crystal display including the touch sensor according to the present invention uses an upper floating electrode spaced apart from and overlapped with the gate line GL and the data line DL, or the gate line GL and the readout line ROL. By forming the touch capacitor Ct, the structure of the touch sensor is very simple, thereby reducing the aperture ratio of the liquid crystal display.

4 is an equivalent circuit diagram of a liquid crystal display device with a touch sensor according to an exemplary embodiment of the present invention, and FIGS. 5 and 6 are different driving waveform diagrams of the liquid crystal display device shown in FIG. 4.

4 includes a plurality of pixels connected to the gate line GL and the data line DL, and a touch capacitor formed between the gate line GL and the readout line ROL. A display unit having Ct, a gate driver 10 for driving a plurality of gate lines GL, a data driver 12 for driving a plurality of data lines DL, and a plurality of readout lines ROL. And a readout circuit 14 for driving.

In the display unit, a plurality of gate lines GL and a plurality of data lines DL are insulated from each other, and the readout line ROL has a plurality of data lines DL therebetween. It is formed side by side with.

Each pixel includes a thin film transistor TFT connected to a gate line GL and a data line DL, a liquid crystal capacitor Clc and a storage capacitor Cst connected in parallel with the thin film transistor TFT. The liquid crystal capacitor Clc includes a pixel electrode connected to the thin film transistor TFT, a common electrode formed on the upper substrate or the lower substrate, and a liquid crystal layer between the pixel electrode and the common electrode. The storage capacitor Cst is formed by overlapping a pixel electrode and a common electrode of a lower substrate with an insulating layer interposed therebetween. The thin film transistor TFT charges the data signal from the data line DL to the liquid crystal capacitor Clc and the storage capacitor Cst in response to the gate signal of the gate line GL, and the liquid crystal capacitor Clc is charged. The liquid crystal is driven according to the voltage, and the storage capacitor Cst keeps the charging voltage of the liquid crystal capacitor Clc stable.

The touch capacitor Ct is formed between the gate line GL and the readout line ROL. As illustrated in FIGS. 2 and 3, the touch capacitor Ct is formed by overlapping the floating electrode on the upper substrate with the liquid crystal layer between the gate lines GL and the lead-out line ROL. The touch capacitor Ct senses a sensing signal by changing the voltage output to the lead-out line by a capacitive coupling phenomenon whenever the gate voltage on the gate line GL changes, that is, whenever the gate voltage rises or polls. Outputs In particular, the touch capacitor Ct is a sensing signal in which the capacitance of the touch capacitor Ct is changed (increased) due to a decrease in the interval of the touch capacitor Ct according to the touch pressure when a touch event occurs and is output to the lead-out line ROL. The variable is expressed by increasing (variing).

The gate driver 10 sequentially drives the plurality of gate lines GL.

The data driver 12 converts a digital data signal input from the outside into an analog data signal and supplies the data signal to the plurality of data lines DL each time the gate line GL is driven.

The readout circuit 14 initializes the reference voltage Vref to the readout line ROL and senses the outputted through the readout line ROL in response to a change in capacitance of the touch capacitor Ct due to a touch event. Touch is detected by detecting the amount of change in the signal. The readout circuit 14 also detects the touch position (XY coordinate) based on the positional information (X coordinate) of the leadout line ROL and the positional information (Y coordinate) of the gate line GL. The readout circuit 14 may also detect multi-touch generated simultaneously at different points through the touch capacitor Ct and the readout line ROL.

The readout circuit 14 includes an amplifier 16 connected to each readout line ROL, and a capacitor Cint and a switch SW connected in parallel between input / output terminals of the amplifier 16. The amplifier 16 outputs the sensing signal Vout by comparing the reference voltage Vref input to the non-inverting terminal + with the output voltage of the readout line ROL input to the inverting terminal −. The switch SW initializes the readout line ROL to the reference voltage Vref in the data writing period, and outputs the sensing signal Vout according to the voltage variation of the readout line ROL in the touch sensing period.

Specifically, the gate driver 10 sequentially supplies gate pulses that do not overlap with adjacent gate pulses to the n−1 th and n th gate lines GLn−1 and GLn as shown in FIG. 5. The data driver 12 supplies a data signal to the data line DL every time the gate pulse is supplied and writes the data signal to the corresponding pixel. At this time, the readout circuit 14 turns on the switch SW to initialize the readout line ROL to the reference voltage Vref.

Next, when the data signal is stored in the corresponding pixel, the switch SW is turned off as shown in FIG. 4, and then the gate pulse is lowered from the gate on voltage Vgh to the gate off voltage Vgl. At this time, the voltage of the readout line ROL is changed by capacitive coupling between the gate line GL and the readout line ROL by the touch capacitor Ct, thereby outputting the output voltage Vout of the amplifier 16. As shown in Equation 1 below, the difference between the capacitance ratio Ct / Cint of the touch capacitor Ct and the capacitor Cint of the readout circuit 14, the gate-on voltage Vgh, and the gate-off voltage Vgl. It is determined by the product of the voltages Vgh-Vgl. In other words, as the switch SW is turned on at the polling time of the gate pulse as shown in FIG. 4, the voltage Vout output from the amplifier 16 is the capacitor of the touch capacitor Ct and the readout circuit 14. It is determined in proportion to the capacitance ratio Ct / Cint of Cint and the difference voltages Vgh-Vgl of the gate-on voltage Vgh and the gate-off voltage Vgl.

At this time, when a touch event occurs and the capacitance of the touch capacitor Ct varies to ΔCt, as shown in Equation 2 below, the output voltage Vout of the amplifier 16 is proportional to the amount of change in the capacitance of the touch capacitor Ct. ) Also varies with? Vout. In other words, the touch ΔCt of the touch capacitor Ct increases due to the touch event, and thus, the voltage Vout output from the amplifier 16 may increase, as shown in FIG. 5, to sense the touch.

On the other hand, as shown in FIG. 6, the switch SW of the readout circuit 14 is turned on at the rising point of the gate pulse to change the output voltage Vout of the amplifier 16 according to the capacitance variation of the touch capacitor Ct. Touch can be detected.

Specifically, the gate driver 10 sequentially supplies gate pulses that do not overlap with adjacent gate pulses to the n−1 th and n th gate lines GLn−1 and GLn as shown in FIG. 6. The data driver 12 supplies a data signal to the data line DL every time the gate pulse is supplied and writes the data signal to the corresponding pixel.

In a period before the gate pulse rises from the gate-off voltage Vgl to the gate-on voltage Vgh, the readout circuit 14 turns on the switch SW so that the readout line ROL is referenced to the reference voltage Vref. Initialize with. Subsequently, the gate pulse rises from the gate off voltage Vgl to the gate on voltage Vgh and turns off the switch SW of the readout circuit 14. At this time, due to the capacitive coupling between the gate line GL and the readout line ROL, the voltage of the readout line ROL is reduced by the touch capacitor Ct as shown in Equation 3 below. And the capacitance ratio Ct / Cint of the capacitor Cint of the readout circuit 14 and the difference between the gate-on voltage Vgh and the difference voltage Vgh-Vgl of the gate-off voltage Vgl are negative. The output voltage Vout is output.

At this time, when a touch event occurs and the capacitance of the touch capacitor Ct varies to ΔCt, as shown in Equation 2 below, the output voltage Vout of the amplifier 16 is proportional to the amount of change in the capacitance of the touch capacitor Ct. ) Also varies with? Vout. In other words, a touch event may increase the capacitance ΔCt of the touch capacitor Ct and increase the absolute value of the negative voltage Vout output from the amplifier 16 as shown in FIG. 6 to sense the touch. .

FIG. 7 is an equivalent circuit diagram of a liquid crystal display with a touch sensor according to another exemplary embodiment. FIG. 8 is a driving waveform diagram of the liquid crystal display shown in FIG. 7.

In the liquid crystal display device having the touch sensor illustrated in FIG. 7, the touch capacitor Ct is formed between the gate line GL and the data line DL, in contrast to the liquid crystal display device having the touch sensor illustrated in FIG. 4. Since the readout line ROL is omitted and the readout circuit 18 is connected to the output terminal of the data line DL with the blocking capacitor Cb interposed therebetween, a redundant configuration The description of the elements will be omitted.

The touch capacitor Ct is formed between the gate line GL and the data line DL. As illustrated in FIGS. 2 and 3, the touch capacitor Ct is formed by overlapping the floating electrode on the upper substrate with the liquid crystal layer between the gate lines GL and the data lines DL. The touch capacitor Ct senses a sensing signal by changing the voltage output to the lead-out line by a capacitive coupling phenomenon whenever the gate voltage on the gate line GL changes, that is, whenever the gate voltage rises or polls. Outputs In particular, when the touch event occurs, the touch capacitor Ct varies the sensing signal output to the readout line by varying (increasing) the capacitance of the touch capacitor Ct due to a decrease in the interval of the touch capacitor Ct according to the touch pressure. Increase).

In FIG. 7, the data line DL also serves as a readout line for supplying the output signal of the touch capacitor Ct to the readout circuit 18 as well as the data line for supplying the data signal. DL) is time-division driven into a data recording period and a touch sensing period. The blocking capacitor Cb connected in series between the output terminal of the data line DL and the readout circuit 18 prevents the driving of the data driver 12 and the driving on the readout circuit 18 from colliding with each other.

In detail, the gate driver 10 sequentially supplies gate pulses that do not overlap with adjacent gate pulses to the n−1 th and n th gate lines GLn−1 and GLn as shown in FIG. 8. The data driver 12 supplies a data signal to the data line DL every time the gate pulse is supplied and writes the data signal to the corresponding pixel, and in this data writing period, the switch SW of the readout circuit 18 is turned on. do. In this case, the inverting input terminal of the amplifier 14 is separated from the data line DL by the blocking capacitor Ct to maintain the reference voltage Vref equal to the output voltage Vout of the amplifier 14.

Next, when the data signal is stored in the corresponding pixel, the switch SW is turned off in the touch sensing period as shown in FIG. 8, and the output terminal of the data driver 12 is in a high impedance state. Subsequently, when the gate pulse falls from the gate-on voltage Vgh to the gate-off voltage Vgl, the following math is performed by capacitive coupling by the touch capacitor Ct between the gate line GL and the data line DL. As shown in Equation 5, the voltage of the data line DL is changed to the negative polarity ΔVdata and the output voltage Vout of the amplifier 16 is also changed in proportion to the negative voltage variation ΔVdata of the data line DL. .

In Equation 5, Cdata represents the parasitic capacitance of the data line DL.

At this time, when a touch event occurs and the capacitance of the touch capacitor Ct is changed to ΔCt, the output voltage Vout of the amplifier 16 also varies in proportion to the amount of change in the capacitance of the touch capacitor Ct. In other words, a touch event may increase the capacitance ΔCt of the touch capacitor Ct due to the touch event, thereby increasing the absolute value of the voltage Vout output from the amplifier 16 as shown in FIG. 8.

On the other hand, as the liquid crystal display device becomes more and more fine, the touch sensitivity is gradually decreased because there is a limit in the area for forming the touch capacitor Ct. In order to solve this problem, as described in Korean Patent Application No. 10-2008-0128867 (hereinafter referred to as a preceding application) filed by the same applicant, a method of summing output values of a plurality of touch capacitors distributed in the horizontal direction, and distributed in the vertical direction A method of temporally summing output values of a plurality of touch capacitors can be applied.

The method of summing output values of a plurality of touch capacitors distributed in the horizontal direction of the electrons is performed by connecting the plurality of readout lines with one amplifier of the readout circuit as shown in FIG. The output voltage of the amplifier can be increased in proportion to.

In the latter method, the method of summing the output values of a plurality of touch capacitors distributed in the vertical direction is performed for each lead as the gate voltage on each gate line changes while the plurality of gate lines are driven as shown in FIG. By summing the voltages output through the out line in time, the output voltage of the amplifier can be increased in proportion to the number of gate lines.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be clear to those who have knowledge of.

2, 20: upper substrate 6, 40: lower substrate
3: sensor column spacer 4, 36: common electrode
5: column spacer 7: sensor electrode
10: gate driver 12: data driver
14, 24: readout circuit 16: amplifier
22: black matrix 24: color filter
26: overcoat layer 28: first column spacer
30: second column spacer 32: floating electrode
42: first sensor electrode 44: second sensor electrode
43: insulating film

Claims (15)

An upper substrate on which the color filter array is formed;
A lower substrate on which the thin film transistor array is formed;
A liquid crystal layer between the upper and lower substrates;
A first column spacer for maintaining a cell gap between the upper and lower substrates;
A second column spacer formed on the upper substrate at a lower height than the first column spacer and having a gap with the lower substrate;
A floating electrode covering the second column spacer independently;
And a first and second sensor electrodes on the lower substrate, the first and second sensor electrodes forming a touch capacitor serving as a touch sensor overlapping the floating electrode with the liquid crystal layer interposed therebetween. Device. The method according to claim 1,
The touch capacitor
A first touch capacitor formed between the first sensor electrode and the floating electrode and a second touch capacitor formed between the floating electrode and the second sensor electrode are connected in series. Liquid crystal display. The method according to claim 2,
A first sensor electrode is a gate line included in the thin film transistor array;
The second sensor electrode is a readout line included in the thin film transistor array and intersects the gate line and the insulating layer therebetween;
And the floating electrode overlaps an intersection area of the gate line and the lead-out line. The method according to claim 3,
A gate driver for driving the gate line;
A data driver for driving data lines included in the thin film transistor array;
And a readout circuit configured to sense a touch by inputting an output signal from the touch capacitor through the readout line. The method of claim 4,
The readout circuit is
An amplifier connected with the lead out line;
A capacitor connected between the input and output terminals of the amplifier;
And a switch connected between the input and output terminals of the amplifier. The method according to claim 5,
The amplifier may include the touch capacitor between the gate line and the lead-out line when the gate signal supplied to the gate line falls from the gate on voltage to the gate off voltage or rises from the gate off voltage to the gate on voltage. And a touch sensor by outputting a sensing signal proportional to a capacitance change amount of the touch sensor. The method of claim 6,
And the switch is turned off only during the output period of the sensing signal, and is turned on in the remaining period to initialize the lead-out line to a reference voltage. The method of claim 6,
The absolute value of the output voltage of the amplifier
And a ratio of the capacitance of the touch capacitor to the capacitance of the capacitor of the readout circuit and the difference voltage between the gate on voltage and the gate off voltage. The method according to claim 2,
A first sensor electrode is a gate line included in the thin film transistor array;
The second sensor electrode is a data line included in the thin film transistor array and intersects the gate line and the insulating layer therebetween;
And the floating electrode overlaps an intersection area of the gate line and the data line. The method according to claim 9,
A gate driver for driving the gate line;
A data driver for driving data lines included in the thin film transistor array;
And a readout circuit connected between the output terminal of the data line and a blocking capacitor therebetween, and configured to sense a touch by inputting an output signal from the touch capacitor through the data line. Liquid crystal display. The method according to claim 10,
The readout circuit is
An amplifier connected with an output terminal of the data line with the blocking capacitor interposed therebetween;
A capacitor connected between the input and output terminals of the amplifier;
And a switch connected between the input and output terminals of the amplifier. The method according to claim 5,
The amplifier may be configured when the gate signal supplied to the gate line falls from the gate on voltage to the gate off voltage or when the gate signal rises from the gate off voltage to the gate on voltage. The liquid crystal display device with a built-in touch sensor, characterized in that for determining whether the touch by outputting a sensing signal proportional to the amount of capacitance change. The method of claim 12,
The data line includes a data writing period for supplying and storing data for each pixel;
Time-divided and driven in a touch sensing period for supplying a signal corresponding to the amount of change in capacitance from the touch capacitor to the readout circuit;
And the switch is turned off only in the touch sensing period and turned on in the data writing period. The method according to any one of claims 5 and 11,
And a voltage connected to the plurality of readout lines of the amplifier and outputting a voltage corresponding to the sum of the output signals output from the plurality of readout lines. The method according to any one of claims 5 and 11,
And the amplifier outputs a sum of the output voltages in time whenever the gate signals change while a plurality of gate lines are driven.

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