KR101909985B1 - Liquid crystal display apparatus and method for driving the same - Google Patents

Abstract

The present invention relates to an in-cell touch type liquid crystal display device (LCD) capable of improving touch sensing performance and a driving method thereof.
A driving method of a liquid crystal display device according to an embodiment of the present invention is a driving method of a liquid crystal display device in which an in-cell touch type touch sensor is formed in a liquid crystal panel, And a common electrode is supplied to a common electrode to display an image. In the second period, the pixel electrode or the common electrode is divided into a first period and a second period, A touch sensing signal is supplied to drive the pixel electrode or the common electrode as the touch electrode, and the presence or absence of the user's touch and the touch position are detected during the blink period for distinguishing the previous frame from the next frame.

Description

Technical Field [0001] The present invention relates to a liquid crystal display device and a method of driving the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device including a touch sensor, and more particularly, to an in-cell touch liquid crystal display device (LCD) capable of improving touch sensing performance and a driving method thereof.

As mobile electronic devices such as mobile communication terminals and notebook computers are developed, there is a growing demand for flat panel display apparatuses applicable thereto.

Of the flat panel display devices, liquid crystal display devices are being applied to the fields of development of mass production technology, ease of driving means, low power consumption, high image quality and large screen realization.

As an input device of a flat panel display device, a touch screen (touch sensor) has been applied in place of a conventionally used input device such as a mouse or a keyboard so that a user can input information directly to the screen using a finger or a pen. Such a touch screen is being applied due to its ease of operation by anyone.

2. Description of the Related Art In recent years, in the application of a touch screen to a liquid crystal display device, a touch screen is built in a liquid crystal panel for slimming. In particular, an in-cell touch type liquid crystal display device which detects a user's touch by utilizing an existing structure formed on a lower substrate (TFT array substrate) and an upper substrate (color filter array substrate) as a touch sensing electrode Is being developed.

A pixel of a liquid crystal panel is switched by a thin film transistor (TFT), and a TFT is formed of amorphous silicon (a-Si).

1 is a view illustrating a driving method of a liquid crystal display device including a touch sensor of an in-cell touch type according to the related art.

Referring to FIG. 1, a liquid crystal display device including an in-cell touch-type touch sensor performs display driving and touch sensing driving of an image. In this case, a time division driving method is applied. That is, an image is displayed during a part of one frame, and a touch sensing drive is performed during the remaining period of one frame.

As described above, in the liquid crystal display device and the driving method thereof according to the related art, flicker is generated due to the operational characteristics of the amorphous silicon (a-Si) when an image is displayed at 60 Hz or less.

In particular, amorphous silicon (a-Si) has poor off-current characteristics and therefore has a holding characteristic deteriorating, causing flicker at a low frequency of 60 Hz or less, resulting in deterioration of image display quality.

Accordingly, in order to reduce or prevent the occurrence of flicker in an image, the image must be driven at a frequency of 120 Hz or higher, and image display and touch sensing are enabled by the time division driving method. As an example, it is possible to display an image for 8.3 ms and perform touch sensing for 8.3 ms through time-division driving of a frequency of 120 Hz.

In the case of driving at 120 Hz, the touch sensing period is reduced and the touch sensing performance is lowered. Furthermore, when the display device is driven at 240 Hz in order to enhance the display quality of an image, the touch sensing period is further shortened, thereby further deteriorating the touch sensing performance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and provides a liquid crystal display device and a method of driving the same that can improve the touch sensing performance without deteriorating display quality of an image.

SUMMARY OF THE INVENTION The present invention provides a liquid crystal display device and a method of driving the same that enable time-divisional driving of image display and touch sensing in low-speed driving of 60 Hz or less.

SUMMARY OF THE INVENTION The present invention is directed to a liquid crystal display device and a method of driving the same, which can improve touch sensing performance by sufficiently securing a touch sensing time through low-speed driving at 60 Hz or less.

Other features and advantages of the invention will be set forth in the description which follows, or may be obvious to those skilled in the art from the description and the claims.

A driving method of a liquid crystal display device according to an embodiment of the present invention is a driving method of a liquid crystal display device in which an in-cell touch type touch sensor is formed in a liquid crystal panel, And a common electrode is supplied to a common electrode to display an image. In the second period, the pixel electrode or the common electrode is divided into a first period and a second period, A touch sensing signal is supplied to drive the pixel electrode or the common electrode as the touch electrode, and the presence or absence of touch and the touch position of the user are detected during a blink period in which a previous frame and a next frame are distinguished from each other.

A liquid crystal display device according to an embodiment of the present invention includes: a liquid crystal panel having a touch sensor for touch detection of a user; A backlight unit for supplying light to the liquid crystal panel; And a driving circuit unit for driving a light source of the liquid crystal panel and the backlight unit and detecting a touch of a user, wherein a plurality of pixels are formed on the liquid crystal panel, ). ≪ / RTI >

The liquid crystal display device and the driving method thereof according to the embodiment of the present invention can improve the touch sensing performance without degrading the display quality of the image.

The liquid crystal display device and the driving method thereof according to the embodiment of the present invention enable time-division driving of image display and touch sensing at a low driving speed of 60 Hz or less.

The liquid crystal display device and the driving method thereof according to the embodiment of the present invention can sufficiently secure the touch sensing time through the low-speed driving of 60 Hz or less and improve the touch sensing performance.

In addition, other features and advantages of the present invention may be newly understood through embodiments of the present invention.

1 is a view illustrating a driving method of a liquid crystal display device including a touch sensor of an in-cell touch type according to the related art.
2 is a view illustrating a liquid crystal display device according to an embodiment of the present invention.
3 is a view showing an example of a touch electrode applied to a liquid crystal display device according to an embodiment of the present invention.
4 is a view showing another example of a touch electrode applied to a liquid crystal display device according to an embodiment of the present invention.
5 is a view showing operating characteristics of an oxide TFT applied to a liquid crystal display device according to an embodiment of the present invention.
6 illustrates a method of driving a liquid crystal display device according to an embodiment of the present invention.

Hereinafter, a liquid crystal display device and a driving method thereof according to an embodiment of the present invention will be described with reference to the accompanying drawings.

In describing embodiments of the present invention, when it is described that a structure (electrode, line, wiring, layer, contact) is formed over or on another structure, and below or below, It should be interpreted as including the case where the third structure is interposed between these structures as well as when they are in contact with each other.

The liquid crystal display device has been developed in various ways such as TN (Twisted Nematic) mode, VA (Vertical Alignment) mode, IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode according to a method of adjusting the arrangement of liquid crystal layers.

In the TN mode and the VA mode, a pixel electrode is formed on a lower substrate and a common electrode is formed on an upper substrate to control the alignment of the liquid crystal layer through a vertical electric field.

In the IPS mode and the FFS mode, a pixel electrode and a common electrode are disposed on a lower substrate, and the arrangement of the liquid crystal layer is adjusted by an electric field between the pixel electrode and the common electrode.

In the IPS mode, the pixel electrode and the common electrode are alternately arranged in parallel so that a horizontal electric field is generated between both electrodes to adjust the alignment of the liquid crystal layer. In such an IPS mode, the alignment of the liquid crystal layer is not adjusted in the pixel electrode and the upper portion of the common electrode, so that the transmittance of light is reduced in the region.

The FFS mode is designed to solve the shortcomings of the IPS mode. In the FFS mode, the pixel electrode and the common electrode are spaced apart with an insulating layer therebetween.

At this time, one electrode is formed in a plate shape or a pattern and the other electrode is formed in a finger shape, and the arrangement of the liquid crystal layer is controlled through a fringe field generated between the electrodes Method.

The liquid crystal display device according to the embodiment of the present invention can be applied to both the vertical electric field system (TN mode, VA mode) and the horizontal electric field system (IPS mode, FFS mode) without any mode restriction.

2 is a view illustrating a liquid crystal display device according to an embodiment of the present invention.

2, a liquid crystal display device according to an embodiment of the present invention includes:

A liquid crystal panel 100 in which an in-cell touch type touch sensor (touch screen) is incorporated; A backlight unit 600; And a driving circuit unit.

In FIG. 2, the touch driving circuit unit 700 and the touch sensing circuit unit 800 are shown as separate components, but they may be integrated into one driving circuit unit.

In the liquid crystal panel 100, a plurality of pixels for displaying an image are arranged in a matrix form, and a touch sensor for detecting a touch position of a user is built in an in-cell touch type.

FIG. 3 is a view showing an example of a touch electrode applied to a liquid crystal display device according to an embodiment of the present invention, FIG. 4 is a view showing another example of a touch electrode applied to a liquid crystal display device according to an embodiment of the present invention to be.

FIG. 3 shows the structure of the touch electrode in the liquid crystal panel of the vertical electric field system, and FIG. 4 shows the structure of the touch electrode in the horizontal electric field liquid crystal panel.

3, a liquid crystal panel 100 includes a color filter array substrate 110, a TFT array substrate 120, a lower substrate, and a liquid crystal layer (not shown) interposed between the two substrates 110 and 120, .

Red, green, and blue color filters for displaying full color images are formed on the color filter array substrate 110, and a black matrix for separating pixels is formed between the color filters .

A common electrode 112 is formed on the color filter array substrate 110 and a gap spacer 114a and a pressing spacer 114b for maintaining the cell gap with the TFT array substrate 120 are formed.

Meanwhile, a plurality of pixels are formed on the TFT array substrate 120, and each of the plurality of pixels is defined by data lines DL1 to DLm and gate lines GL1 to GLn which intersect with each other.

An oxide TFT (122) and a storage capacitor (Cst) are formed for each region where the data lines and the gate lines cross each other. The gate electrode of the oxide TFT 122 is connected to the gate line, the source electrode is connected to the data line, and the drain electrode is connected to the pixel electrode 124. [

The pixel electrode 124 formed on the TFT array substrate 120 and the common electrode 112 formed on the color filter array substrate 110 are used not only for displaying an image but also for a touch electrode .

That is, one frame is divided into a first period and a second period, and signals (pixel voltage and common voltage) for displaying an image are supplied to the pixel electrode 124 and the common electrode 112 in the first period.

Then, in the second period, a touch driving signal for touch detection is supplied to the common electrode 112, and a change in capacitance formed between the pixel electrode 124 and the common electrode 112 is sensed by a user's touch, And the touch position. A specific driving method for detecting the touch position will be described later with reference to Fig.

2, the driving circuit includes a gate driver 200, a data driver 300, a D-IC, a timing controller 400, a T-con, a backlight driver 500, A touch driving circuit unit 700, a touch sensing circuit unit 800, and a power supply unit (not shown).

Here, all or a part of the driving circuit portion may be formed on the liquid crystal panel 100 by a COG (Chip On Glass) or a COF (Chip On Flexible Printed Circuit) method.

The timing controller 400 receives an externally input video signal data by using the input vertical synchronization signal V-sync, the horizontal synchronization signal H-sync, and the clock signal CLK, (R, G, B). The timing controller 400 supplies digital image data arranged in units of frames to the data driving circuit unit 300.

The timing controller 400 includes a gate control signal (GCS) for controlling the gate driving circuit unit 200 using the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, and the clock signal CLK, A data control signal (DCS) for controlling the data driving circuit unit 300, and a backlight control signal (BCS) for removing the backlight driving unit.

The timing controller 400 supplies the generated gate control signal GCS to the gate driving circuit portion 200 and supplies the data control signal DCS to the data driving circuit portion 300 and supplies the backlight control signal BCS to the backlight And supplies it to the driving unit 500.

Here, the data control signal DCS includes a source start pulse (SSP), a source sampling clock (SSC), a source output enable (SOE) and a polarity control signal (POL) ), And the like.

The gate control signal GCS may include a gate start pulse (GSP), a gate shift clock (GSC), and a gate output enable (GOE).

The timing controller 400 generates a touch control signal (TCS) for controlling the touch driving circuit unit 700 and supplies the touch control signal to the touch driving circuit unit 700.

The gate driving circuit unit 200 generates a scan signal (gate driving signal) for driving the oxide TFT 122 formed on each of the plurality of pixels based on the gate control signal GCS from the timing controller 400 do.

The gate driving circuit unit 200 sequentially supplies the generated scan signal to a plurality of gate lines formed in the liquid crystal panel 100 during one frame period, and the oxide TFT 122 formed in each pixel is driven by the scan signal Switching of pixels is done.

The data driving circuit unit 300 converts the digital image data (R, G, B) supplied from the timing controller 400 into an analog video signal, that is, a data voltage.

The data driving circuit unit 300 supplies the data voltage converted in accordance with the time when the oxide TFT 122 of each pixel is turned on to the liquid crystal panel 100 based on the data control signal DCS from the timing controller 400 To a plurality of formed data lines.

Since the liquid crystal panel 100 can not generate light by itself, an image is displayed using light supplied from the backlight unit 600.

The backlight unit 600 irradiates light to the liquid crystal panel 100 and includes a plurality of backlights that generate light and a backlight unit that guides light generated from the backlight toward the liquid crystal panel and improves the efficiency of light (A light guide plate or a diffusion plate and a plurality of optical sheets).

Here, the CCFL (Cold Cathode Fluorescent Lamp), EEFL (External Electrode Fluorescent Lamp), and LED (Light Emitting Diode) can be applied as the backlight.

Off time of the backlight based on the backlight control signal BCS input from the timing controller 400. The on-off time of the backlight, the on- And luminance can be controlled.

The touch driving circuit unit 700 supplies a touch sensing signal for touch detection to the touch electrode formed on the liquid crystal panel 100 based on the touch control signal TCS input from the timing controller 400. [ Here, the common electrode 112 or the pixel electrode 124 may be used as the touch electrode.

In one example, when the common electrode 112 is used as a touch electrode, a common voltage Vcom for displaying an image is supplied during a display period of one frame period. Thereafter, in the non-display period, a touch sensing signal for touch detection is supplied to the common electrode 112, so that the common electrode is driven as the touch electrode.

The touch sensing circuit unit 800 compares the capacitance formed on the touch electrode with the reference capacitance to detect the presence or absence of touch by the user and the touch position.

In the present invention, the presence or absence of a user's touch and the touch position can be detected during a reference signal (blink signal) period for distinguishing a previous frame from a next frame.

Here, the start and end of the detection of the touch position of the user may be based on the vertical synchronization signal (V-Sync), and the detection of the presence or absence of the touch and the touch position may be performed by detecting a vertical blink -blank period.

4, a pixel electrode (not shown) and a common electrode 130 are formed on a TFT array substrate 120 of a liquid crystal panel 100 when the liquid crystal display device of the present invention is driven by a horizontal electric field method .

Here, the common electrode 130 may be formed for each pixel or may be formed by blocking a predetermined number of pixels.

Here, the common electrode 130 may function not only for displaying an image but also as a touch electrode for detecting a touch position of a user.

Here, in order to detect the coordinates of the X axis and the Y axis, a plurality of common electrodes 130 arranged in the form of a matrix are arranged in the X axis direction and the X axis direction by using the first touch sensing line 132 and the second touch sensing line 134, Y axis direction.

A touch sensing signal is input from the touch driving circuit 700 to the first common electrodes 132 connected by the first touch sensing line 132 to function as a touch driving electrode.

On the other hand, the second common electrodes 134 connected by the second touch sensing line 134 are connected to the touch sensing circuit unit 800 and function as a touch sensing electrode.

Here, the common electrodes 132 and 134 may be connected by the first touch sensing line 132 and the second touch sensing line 134, and may be formed of a plurality of touch blocks.

At this time, the touch block may include a touch row block for detecting a touch position in the X-axis direction and a touch column block for detecting a touch position in the Y-axis direction. The touch row block and the touch column block are separated from each other without being contacted with each other, and the coordinates of the X axis and the Y axis according to the touch of the user can be recognized.

FIG. 5 is a view showing operation characteristics of an oxide TFT applied to a liquid crystal display device according to an embodiment of the present invention, and FIG. 6 is a view illustrating a driving method of a liquid crystal display device according to an embodiment of the present invention .

5 and 6, a liquid crystal display device according to an exemplary embodiment of the present invention includes an oxide TFT as a switching element for driving a plurality of pixels formed in a liquid crystal panel 100. FIG.

As shown in FIG. 5, when compared with amorphous silicon (a-Si) which has been applied to a conventional liquid crystal display device, the oxide TFT has excellent off current characteristics, It is possible to prevent the occurrence of flicker.

The liquid crystal display device according to the exemplary embodiment of the present invention adjusts the transmittance of light passing through the liquid crystal layer according to the data voltage applied to the pixel electrodes of the pixels and the common voltage Vcom applied to the common electrode And displays an image according to the video signal.

In the non-display period, the common electrode is driven by the touch sensing electrode to sense a change in the capacitance Ctc in response to the user's touch. Then, the touch position is detected by comparing the touch capacitance according to the user's touch with the reference capacitance.

As shown in Fig. 6, the liquid crystal panel 100 may be driven at 60 Hz or less, and one frame may be divided into a first period for displaying an image and a second period for detecting a touch.

Describing with reference to 60 Hz, one frame (16.7 ms) is divided into a first period for display of an image and a second period for touch detection.

Here, a vertical synchronization signal (V-Sync) can be used to distinguish the display period of the image from the touch detection period. A period in which the vertical synchronization signal (V-Sync) is on can be defined as a first period, and a period in which the vertical synchronization signal (V-Sync) is off can be defined as a second period.

In the first period, the image data, that is, the data voltage, is supplied to the data lines in units of one horizontal line in accordance with the data enable (DE) signal. Thus, the data voltage is supplied to the pixel electrode during the period when the oxide TFT is on. At the same time, the common voltage Vcom is supplied to the common electrode.

In the second period, a common electrode is used as a touch electrode, and a touch sensing signal for touch sensing is supplied.

When the touch sensing signal is supplied to the common electrode functioning as the touch electrode, the capacitance formed on the touch electrode is changed by the touch of the user. At this time, the touch sensing circuit unit 800 senses a change in the capacitance caused by the touch and detects the touch position of the user. Information on the detected touch position is generated as a touch sensing signal (TSS) and output.

Here, the start and end of the detection of the touch position of the user may be based on the vertical synchronization signal (V-Sync), and the detection of the presence or absence of the touch and the touch position may be performed by detecting a vertical blink -blank period.

Specifically, in a second period in which touch detection is performed, a touch sensing signal is supplied to a touch electrode (common electrode) in units of one horizontal line in accordance with the DE signal, The touch position of the user can be detected by collecting the change in the capacitance detected in the line.

The liquid crystal display device and the driving method thereof according to the embodiment of the present invention can drive the liquid crystal panel at a low frequency of 60 Hz or less and display the image and touch detection through the time division driving, .

As the touch sensing time becomes longer, the accuracy of the touch sensing and the touch sensing performance are improved, and the touch detection can be precisely performed as compared with the related art.

As described above, when the touch time is sufficiently secured, not only the touch detection but also other application functions necessary for display and touch detection can be additionally performed in a non-display period in which no image is displayed, Can be provided.

It will be understood by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: liquid crystal panel 200: gate drive circuit part
300: Data driving circuit unit 400: Timing controller
500: backlight driving unit 600: backlight unit
700: touch driving circuit part 800: touch sensing circuit part
110: TFT array substrate 120: Color filter array substrate
112: common electrode 122: oxide TFT (oxide TFT)
124: pixel electrode

Claims (10)

A method of driving a liquid crystal display device in which an in-cell touch type touch sensor is formed in a liquid crystal panel,
One frame is divided into a first period for displaying an image and a second period for touch detection,
A data voltage is supplied to the pixel electrode formed on the liquid crystal panel in the first period, a common voltage is supplied to the common electrode to display an image,
And the touch sensing signal is supplied to the pixel electrode or the common electrode during the second period to drive the pixel electrode or the common electrode to the touch electrode,
The presence or absence of a user's touch and the touch position are detected in a blink period for distinguishing a previous frame from a next frame,
Wherein the blink period divides the boundary between the second period and the first period. The method according to claim 1,
Wherein an oxide TFT is formed as a switching element for driving a plurality of pixels arranged in a matrix form on the liquid crystal panel and an image is displayed and a touch is detected at a driving frequency of 60 Hz or less A method of driving a device. The method according to claim 1,
And performs an application function according to the display of the image and the touch detection in the second period. The method according to claim 1,
A period in which the vertical synchronization signal is turned on is defined as the first period,
A period during which the vertical synchronization signal is off is defined as the second period,
In the first period, the image data is supplied to the data lines in units of one horizontal line in accordance with the data enable (DE) signal,
And supplying a touch sensing signal to the touch electrode during the second period. delete The method according to claim 1,
And detects the touch position of the user by collecting the change in capacitance detected in all horizontal lines and vertical lines in the blink period. A liquid crystal panel having a touch sensor for touch detection of a user;
A backlight unit for supplying light to the liquid crystal panel; And
And a driving circuit for driving a light source of the liquid crystal panel and the backlight unit and detecting a user's touch,
A liquid crystal display device in which a plurality of pixels are formed in the liquid crystal panel and the plurality of pixels are switched by an oxide TFT,
One frame is divided into a first period for displaying an image and a second period for touch detection,
A data voltage is supplied to the pixel electrode formed on the liquid crystal panel in the first period, a common voltage is supplied to the common electrode to display an image,
In the second period, a pixel electrode or a common electrode formed on the liquid crystal panel is driven by a touch electrode,
A touch position and a touch position of a user are detected in a blink period for distinguishing a previous frame from a next frame,
Wherein the blink period divides the boundary between the second period and the first period. delete 8. The method of claim 7,
And performs display and touch detection of an image at a driving frequency of 60 Hz or less. 8. The method of claim 7,
And detects the touch position of the user by collecting the change in capacitance detected in all the horizontal and vertical lines during the blink period.

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