KR20080105791A - Display device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, comprising: a sensing element for generating a sensing signal in response to an external contact, a switching element for periodically interrupting the output of the sensing element and a sensing element when the switching element is turned off And a reset device for turning off. As a result, the detection capability of the display device may be improved by removing unnecessary signal components due to minute contact or leakage currents.

Description

Display device {DISPLAY DEVICE}

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of a pixel including a pressure detector in a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a schematic cross-sectional view for describing a sensing operation of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a signal waveform diagram for describing an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

The present invention relates to a display device, and more particularly to a display device having a touch sensing function.

A typical liquid crystal display (LCD) includes two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix form and connected to a switching element such as a thin film transistor (TFT) to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the display panel and receives a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor, and the liquid crystal capacitor becomes a basic unit that forms a pixel together with a switching element connected thereto.

A touch screen panel refers to a device that touches a finger or a touch pen on the screen to write and draw characters or pictures, or executes icons to perform a desired command to a machine such as a computer. A liquid crystal display with a touch screen panel may find out whether a user's finger or a touch pen touches the screen and contact position information. However, such a liquid crystal display device has problems such as a cost increase due to a touch screen panel, a decrease in yield due to a process of adhering the touch screen panel to a liquid crystal panel, a decrease in luminance of the liquid crystal panel, and an increase in product thickness.

Therefore, in order to solve these problems, a technology for embedding a sensing element in a liquid crystal display device instead of a touch screen panel has been developed. The sensing element detects a change in light or pressure applied to a screen by a user's finger or the like so that the liquid crystal display may determine whether the user's finger or the like has touched the screen and contact position information.

Such a sensing element includes a switching element such as a thin film transistor, and the sensing element is turned on at a moment of contact to transmit a sensing signal. However, the sensing element transmits an unnecessary signal component due to a minute contact or leakage current, and the unnecessary signal component brings about a deterioration in the sensing capability of the display device.

Accordingly, an aspect of the present invention is to provide a display device capable of improving a sensing capability.

According to an aspect of the present invention, there is provided a display device including: a sensing element generating a sensing signal in response to a contact from the outside; a switching element periodically intermittently outputting the sensing element; and And a reset device for turning off the sensing device when it is turned off.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

Now, a liquid crystal display as an embodiment of the display device according to the present invention will be described in detail with reference to FIGS. 1 to 3.

1 is a block diagram of a liquid crystal display according to an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of a pixel including a pressure sensing unit in the liquid crystal display according to an embodiment of the present invention, and FIG. A schematic cross-sectional view for describing a sensing operation of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, a data driver 500, and a gray voltage generator connected thereto. The unit 550, the detection signal processor 800, and a signal controller 600 for controlling them are included.

The liquid crystal panel assembly 300 may include a plurality of signal lines G ₁ -G _n , D ₁ -D _m , P ₁ -P _m , and a plurality of pixels connected to the plurality of signal lines in an equivalent circuit and arranged in a substantially matrix form. (PX).

The signal lines G ₁ -G _n , D ₁ -D _m , and P ₁ -P _m are a plurality of gate lines G ₁ -G _n transmitting gate signals, and image data lines D ₁ transferring image data signals. -D _m ) and sense data lines P ₁ -P _m that carry sense data signals. The gate lines G ₁ -G _n extend approximately in the row direction and are substantially parallel to each other, and the image data lines D ₁ -D _m and the sensing data lines P ₁ -P _m extend approximately in the column direction. Almost parallel to each other

As shown in Fig. 2 and Fig. 3, each pixel PX, for example, the i-th (i = 1, 2, ..., n) gate line G _i and the j-th (j = 1, 2) , ..., m) The pixel PX connected to the image data line D _j and the sensing data line P _j includes a display unit DC and a pressure sensing unit SC.

The display unit DC includes a switching element Qs1, a liquid crystal capacitor Clc, and a storage capacitor Cst. Holding capacitor Cst can be omitted as needed.

The switching element Qs1 is a three-terminal element of a thin film transistor or the like provided in the thin film transistor array panel 100, the control terminal of which is connected to the gate line G _i , and the input terminal of the image data line D _j . The output terminal is connected to the liquid crystal capacitor Clc and the holding capacitor Cst.

The liquid crystal capacitor Clc has a pixel electrode (not shown) of the thin film transistor array panel 100 and a common electrode 270 of the common electrode display panel 200 as two terminals, and a liquid crystal layer between the pixel electrode and the common electrode 270. (3) functions as a dielectric. The pixel electrode is connected to the switching element Qs1, and the common electrode 270 is formed on the front surface of the common electrode display panel 200 and receives the common voltage Vcom. Unlike in FIG. 3, the common electrode 270 may be provided in the thin film transistor array panel 100. In this case, at least one of the pixel electrode and the common electrode 270 may be linear or rod-shaped.

The storage capacitor Cst, which serves as an auxiliary part of the liquid crystal capacitor Clc, is formed by overlapping a separate signal line (not shown) and a pixel electrode of the thin film transistor array panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage Vcom is applied to the signal line. However, the storage capacitor Cst may be formed by the pixel electrode overlapping the front gate line directly above the insulator.

The pressure sensing unit SC includes a switching element Qs2, a reset element Qr, and a sensing element PU.

The switching element Qs2 is a three-terminal element such as a thin film transistor provided in the thin film transistor array panel 100, the control terminal of which is connected to the gate line G _i , and the input terminal of which is connected to the sensing element PU. The output terminal is connected to the sense data line P _j .

The reset element Qr is a three-terminal element such as a thin film transistor, the control terminal of which is connected to the next gate line (G _{i +1} ), the input terminal of which is connected to the gate line (G _i ), The output terminal is connected to the control terminal n1 of the sensing element Qp.

The sensing element PU includes a pressure switch S and a driving transistor Qp.

The pressure switch S is connected between the control terminal n1 of the driving transistor Qp and the common voltage Vcom, and according to the pressure accompanying the contact applied to the liquid crystal panel assembly 300, the driving transistor Qp. Is connected to the common voltage (Vcom). For example, when pressure is applied, an electrode (not shown) to which the common voltage Vcom is applied may approach the control terminal n1 of the driving transistor Qp and may touch each other. However, the pressure switch S may be another physical quantity capable of connecting the driving transistor Qp to the common voltage Vcom, in which case the pressure switch S will be called under another name.

The driving transistor Qp is a three-terminal element whose control terminal n1 is connected to the output terminal of the pressure switch S and the reset element Qr, and the input terminal n2 is connected to the sensing input voltage Vd. The output terminal n3 is connected to the input terminal of the switching element Qs2.

Referring to Figure 3 will be described in detail the actual structure of the pressure switch (S).

Referring to FIG. 3, the control terminal 124 of the sensing element Qp is formed to be insulated from the input terminal n2 and the output terminal n3 on the substrate 110 of the thin film transistor array panel 100. The interlayer insulating layer 160 and the passivation layer 180 are formed.

A part of the control terminal 124 is exposed through the contact hole 185 formed in the interlayer insulating film 160 and the passivation film 180. In addition, a contact member 192 is formed on the passivation layer 180, and the contact member 192 is connected to the control terminal 124 through the contact hole 185.

Meanwhile, the common electrode 270 is formed on the substrate 210 of the common electrode display panel 200, and the protrusion 280 is formed between the substrate 210 and the common electrode 270. The protrusion 280 faces the contact member 192.

The pressure switch S is formed by the contact member 192, the control terminal 124 of the sensing element Qp connected thereto, and the portion of the common electrode 270 protruding by the protrusion 280. The pressure switch S performs on / off operation according to a change in distance between the thin film transistor array panel 100 and the common electrode display panel 200 by contact.

Referring back to FIG. 1, the gate driver 400 is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300 to turn on the switching elements Qs 1 and Qs 2 to turn on the gate-on voltage Von. A gate signal composed of a combination of the voltage and the gate-off voltage Voff to be turned off is applied to the gate lines G ₁ -G _n .

The data driver 500 is connected to the image data lines D ₁ -D _m of the liquid crystal panel assembly 300 to apply a data voltage representing the image signal to the image data lines D ₁ -D _m .

The gray voltage generator 550 generates two sets of gray scales in relation to the transmittance of the pixel. One of the two sets has a positive value for the common voltage Vcom and the other set has a negative value. The gray voltage generator 550 outputs the plurality of gray voltage sets to the data driver 500.

The sensing signal processor 700 is connected to the sensing data lines P ₁ -P _m of the liquid crystal panel assembly 300, and converts the analog sensing data signals from the sensing data lines P ₁ -P _m into digital signals. To generate a digital sense data signal (DSDS).

The signal controller 600 controls operations of the gate driver 400 and the data driver 500.

Each of the driving devices 400, 500, 550, and 800 may be mounted directly on the liquid crystal panel assembly 300 in the form of at least one integrated circuit chip, or may be a flexible printed circuit film (not shown). It may be mounted on the liquid crystal panel assembly 300 in the form of a tape carrier package (TCP) or mounted on a separate printed circuit board (not shown). Alternatively, these driving devices 400, 500, 550, and 800 may be integrated in the liquid crystal panel assembly 300 together with signal lines G ₁ -G _n , D ₁ -D _m , P ₁ -P _m , and the like.

Next, the display operation and the detection operation of the liquid crystal display will be described.

The signal controller 600 receives input image signals R, G, and B and control signals DE, Hsync, Vsync, and MCLK from an external graphic controller (not shown) to control the gate control signal CONT1 and data. The signal CONT2 and the sensing control signal CONT3 are generated, and the output image signal DAT is generated by processing the input image signals R, G, and B according to operating conditions.

According to the data control signal CONT2 from the signal controller 600, the data driver 500 converts the digital image signal DAT into an analog data voltage and applies it to the corresponding image data lines D ₁ -D _m .

The gate driver 400 applies the gate-on voltage Von to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600 to the gate lines G ₁ -G _n . Turn on the connected switching elements Qs1 and Qs2. Then, the data voltage applied to the image data lines D ₁ -D _m is applied to the display unit DC through the switching element Qs1 turned on, and at the same time, the pressure sensing unit SC is turned on through the switching element Qs2 turned on. The sensing data signal is output from the sensing data lines (P ₁ -P _m ).

First, the display operation of the display unit DC will be described.

The difference between the data voltage applied through the switching element Qs1 and the common voltage Vcom is shown as the charging voltage of the liquid crystal capacitor Clc, that is, the pixel voltage. The arrangement of the liquid crystal molecules varies depending on the magnitude of the pixel voltage, thereby changing the polarization of light passing through the liquid crystal layer 3. The change in polarization is represented by a change in the transmittance of light by the polarizer, through which the display unit DC displays the luminance represented by the gray level of the image signal DAT.

Next, the sensing operation of the pressure sensing unit SC will be described with reference to FIG. 2.

The turned on switching element Qs2 receives a voltage coming from the output terminal of the sensing element PU. At this time, the control terminal of the reset element Qr is turned off because it is connected to the gate line G _{i + 1} of the next stage.

When the user's finger or touch pen or the like contacts the display device at the time when the switching element Qs2 is turned on, the pressure switch S is closed, and the common voltage Vcom is applied to the control terminal n1 of the driving transistor Qp. Is entered. Then, the driving transistor Qp is turned on and the sensing input voltage Vd is output to the sensing data line P _j .

In contrast, if there is no contact at the time when the switching element Qs2 is turned on, the pressure switch S is open. Therefore, the driving transistor Qp is turned off and the sensing input voltage Vd is not output to the sensing data line P _j .

Subsequently, when the gate-on voltage Von is applied to the next gate line G _{i + 1} , the gate-on voltage Von is controlled by the control terminal of the reset element Qr connected to the i-th gate line G _i . The reset element Qr is applied to turn on. Then, the reset element Qr transfers the gate-off voltage Voff input from the i-th gate line G _i to the control terminal n1 of the driving transistor Qp to turn off the driving transistor Qp.

The liquid crystal display repeats this process in units of one horizontal period (also referred to as "1H" and equal to one period of the horizontal sync signal Hsync and the data enable signal DE), thereby all gate lines G _The gate-on voltage Von is sequentially applied to ₁ -G _n ). In turn, by applying the gate-on voltage (Von) to the data voltage to all of the display unit (DC) to display an image of one frame (frame) and at the same time read the detection signal from all the pressure detector (SC).

At the end of one frame, the next frame starts and the state of the inversion signal RVS applied to the data driver 500 is controlled so that the polarity of the data voltage applied to each display unit DC is opposite to the polarity of the previous frame (" Invert frame "). At this time, even in one frame, the polarity of the data voltage flowing through one image data line is periodically changed according to the characteristics of the inversion signal RVS (eg, row inversion and point inversion), or polarity of the data voltage applied to one pixel row. Can also be different (eg invert columns, invert points).

4 is a signal waveform diagram for describing an operation of a liquid crystal display according to an exemplary embodiment of the present invention. 4 is a voltage of i-th image data line (D _i) and the j-th sensing data line pixels (PX) drive transistor (Qp) a control terminal voltage (Vn1), the output terminal of that is connected to the (P _j) ( Vn3), the voltage of the i-th gate line G _i , the voltage of the (i + 1) th gate line G _{i + 1} , and the voltage of the j-th sensing data line P _j .

2 and 4, the control terminal n1 of the driving transistor Qp receives the common voltage Vcom in the contact section where the contact occurs. The driving transistor Qp is then turned on and sends the sense input voltage Vd to the output terminal n3 of the sense element Qp. When the gate-on voltage Von is applied to the i-th gate line G _i in this contact section, the sensing data line Pj emits a sensing signal.

After that, when the sensing period ends, the gate-on voltage Von is input to the next gate line G _{i + 1} and the gate-off voltage Voff is applied through the turn-on reset element Qr to receive the driving transistor Qp. Control terminal n1 immediately drops to low level (1). In addition, the output terminal n3 of the driving transistor Qp also immediately changes to a low level at the end of the contact section.

In the driving transistor Qp of the general liquid crystal display, a voltage is applied for a predetermined period even when the contact period ends due to a minute contact or leakage current (2). However, according to the embodiment of the present invention, the level changes immediately at the end of the contact section (1). That is, the sensing capability can be improved by turning off the driving transistor Qp at the end of the contact section due to the minute contact or leakage current, thereby preventing unnecessary signal components from being transferred.

As described above, according to the exemplary embodiment of the present invention, the sensing capability of the display device may be improved by removing unnecessary signal components due to minute contact or leakage current.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (5)

A sensing element for generating a sensing signal in response to a contact from the outside, A switching device that periodically interrupts the output of the sensing device, and And a reset device for turning off the sensing device when the switching device is turned off. Display device. In claim 1, The sensing element Pressure switch closed and open according to the contact, and A driving transistor turned on or off depending on the state of the pressure switch; Display device. In claim 2, The pressure switch is First electrode, A second electrode opposite the first electrode, and A liquid crystal layer interposed between the first electrode and the second electrode, The first electrode or the second electrode includes a projection Display device. In claim 3, A first gate line transferring the first gate signal; A second gate line for transmitting a second gate signal; The switching device interrupts the output of the sensing device in accordance with the first gate signal, The reset device applies the first gate signal to the driving transistor according to the second gate signal. Display device. In claim 1, After the switching element is turned on and turned off, the reset element is turned on and turned off Display device.

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