Abstract:
The present invention provides a liquid crystal display (LCD) panel, comprising: a plurality of scan lines, data lines and sense lines, display cells and sensor elements. Each sensor element includes a first bottom electrode, a thin film transistor (TFT), a second bottom electrode, and a switch. When the switch is pressed down, the first bottom electrode is electrically connected to the second bottom electrode. The present invention also provides an inspection method for touching the above-mentioned LCD panel, comprising: opening one of the scan lines; electrically connecting the pixel electrode with an inspection circuit; comparing the input voltage to the threshold voltage, while the inspection circuit sends a control signal, representing that the display cell has been pressed.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to China Application Serial Number 200910261136.7, filed Dec. 28, 2009, which is herein incorporated by reference. 
       FIELD OF INVENTION 
       [0002]    The present invention relates to a liquid crystal display (LCD) panel. More particular, the present invention relates to an LCD panel having both functions of press inspection and image display. 
       BACKGROUND ART 
       [0003]    Currently, with development of the semiconductor technology and the fabrication process, the thin film transistor liquid crystal display (TFT-LCD) has been widely used in various fields because of its high quality, low power consumption, little radiation and light weight. 
         [0004]    The LCD panel typically includes: an array substrate, a color filter substrate, and a liquid crystal molecules layer interposed between the array substrate and the color filter substrate. In detail, a plurality of pixels is located on the array substrate, which is defined as the intersection point of the data line and corresponding scan line. And these pixels are driven by the pixel driver circuit consisting of the electronic components. Usually, the color filter substrate is a transparent glass substrate, on which the transparent conductive film layer is formed of sputtering the materials such as ITO or IZO. Such transparent conductive film layer (as common electrode) electrically connects to the common electrode source, together with the corresponding pixel electrode across the array substrate to generate the predetermined voltage, and thereby to control the twist of the liquid crystal molecules. 
         [0005]    Illustrating the touch panel as an example, in the prior art, a photo spacer is generally designed to locate on the color filter substrate, and the photo spacer protrudes towards the orientation of the array substrate. Also, a transparent conductive film layer, such as ITO layer, is sputtered on the photo spacer&#39;s surface and the total surface of the color filter substrate. When the user presses the touch screen, the ITO layer on the photo spacer electrically connects to the sensor on the array substrate. Thus, the display cell of the LCD panel may be inspected to have been pressed down according to the voltage signal from the sensor. Otherwise, when the user does not press the touch screen, the ITO layer on the photo spacer keeps disconnecting to the sensor in the array substrate. 
         [0006]    However, in the above described LCD panel, both the surfaces of the color filter substrate and the photo spacer are sputtered a continuous transparent conductive film layer, so that the voltage level achieved from the sensor is approximately equal to the voltage level of the color filter substrate, when the display cell is pressed. That is, the sidewall of the photo spacer must be coated with the ITO conductive layer, and it will lead to some problems about the stability and complexity of the fabrication process. Further, when the color filter substrate electrically connects to the common power source, the system has to supply the direct current (DC) power, and thereby the system power consumption increases. Once the alternative current (AC) power is loaded, if we press the LCD panel, then the sensor will be conductive to the ITO layer in the color filter substrate via the photo spacer, and thus the sensor has an instable voltage. 
       SUMMARY OF THE INVENTION 
       [0007]    Aiming at the above-described defects regarding the conventional techniques for the usage of the LCD panel, the present invention provides a new LCD panel, and also provides an inspection method with respect to such panel. 
         [0008]    In one aspect, the present invention is directed to an LCD panel, which comprises: a plurality of scan lines, a plurality of data lines, a plurality of sense lines, a plurality of pixel units. The data lines are arranged to perpendicularly intersect across the scan lines, and the sense lines are arranged to be parallel to the data lines. Each of pixel units comprises a display cell and a sensor element, wherein the display cell is electrically connected with one scan line and one data line, and the sensor element comprises a first sensing electrode, a thin film transistor, a second sensing electrode, and a switch element. The thin film transistor comprises a gate electrode electrically connected to the scan line connected with the display cell; a first electrode electrically connected to one sense line; and a second electrode electrically connected to the first sensing electrode. The second sensing electrode is arranged on the same plane together with the first sensing electrode, and the second sensing electrode and the first sensing electrode separate from each other. And the switch element is arranged over the first and second sensing electrodes, wherein the switch element electrically connects the first sensing electrode with the second sensing electrode when the switch element is pressed to touch the first and second sensing electrodes. 
         [0009]    In one embodiment, the switch element is a conductive material layer disposed on the top surface of a photo spacer and the photo spacer is disposed on a first substrate opposite to a second substrate having the thin film transistor thereon. Preferably, the conductive material layer is a transparent material of ITO or IZO. Preferably, the conductive material layer is electrically insulated to a common electrode disposed on the first substrate. 
         [0010]    In another embodiment, the second sensing electrode is electrically connected to a storage capacitance bottom electrode or a next scan line adjacent to the sensor element. 
         [0011]    In a further embodiment, the first sensing electrode is a low-level voltage when the switch is pressed down. 
         [0012]    In another aspect, the present invention is directed to an LCD panel, which comprises: a plurality of scan lines, a plurality of data lines, a plurality of display pixel cells, an inspection circuit and a switch. The data lines are arranged to perpendicularly intersect across the scan lines. Each of the display pixel cells comprises a sensing bottom electrode, a display electrode, a thin film transistor and a sensing conductive layer, wherein the sensing bottom electrode is electrically connected to a reference power source; the display electrode is arranged on the same plane together with the sensing bottom electrode, and the display electrode and the sensing bottom electrode separate from each other; the thin film transistor comprises a gate electrode electrically connected to one scan line and a first electrode electrically connected to one data line and a second electrode electrically connected to the display electrode; and the sensing conductive layer disposed over the sensing bottom electrode and the display electrode. And the sensing conductive layer electrically connects the sensing bottom electrode and display electrode when the sensing conductive layer is pressed down to touch the sensing bottom electrode and display electrode. The inspection circuit is used to inspect the voltage of the display electrode; and a switch is electrically connecting to the data line for handing over the first electrode electrically connecting to the inspection circuit through the data line, and when the display signal is written into the display electrode, the switch connects the first electrode with a data driving circuit. 
         [0013]    In one embodiment, the sensing conductive layer is made of transparent conductive materials. Moreover, the transparent conductive material is ITO or IZO. 
         [0014]    In another embodiment, the sensing conductive layer is located on the top surface of a photo spacer and the photo spacer is disposed on a first substrate opposite to a second substrate having the thin film transistor thereon. Preferably, the sensing conductive layer is insulated to a common electrode disposed on the first substrate. 
         [0015]    In a further embodiment, the display electrode is the reference voltage level when the sensing conductive layer is pressed down. 
         [0016]    In yet further embodiment, the inspection circuit comprises a voltage comparator. Preferably, a first input terminal of the voltage comparator connects to the display electrode via the switch, and a second input terminal of the voltage comparator electrically connects to a reference voltage. In addition, the inspection circuit further comprises a resistor, disposed between the first input terminal and the switch. 
         [0017]    In one embodiment, the LCD panel further comprises a resistor arranged between the inspection circuit and the switch. 
         [0018]    In another aspect, the invention provides an inspection method for the LCD panel comprising a resistor arranged between the inspection circuit and the switch. The method comprises: opening the scan line linking to the gate electrode, and handing over the switch to connect the display electrode with the inspection circuit; and transmitting electrical signal of the display electrode to the inspection circuit, wherein the inspection circuit sends out a control signal representing that the display cell has been pressed and the sensing conductive layer electrically connects the display electrode to the sensing bottom electrode, when the electrical signal of the display electrode is derived from the reference power source. 
         [0019]    In one embodiment, the electrical signal is a current signal. 
         [0020]    In another aspect, the invention provides an inspection method for touching the LCD panel. The method comprises: opening the scan line linking to the gate electrode, and handing over the switch to connect the display electrode with the inspection circuit; and transmitting a voltage signal of the display electrode to the inspection circuit, wherein the inspection circuit sends out a control signal representing that the display cell has been pressed and the sensing conductive layer electrically connects the display electrode to the sensing bottom electrode, when the voltage signal of the display bottom electrode is derived from the reference power source. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    These and other features of the invention will become more apparent from the following description, in which reference is made to the appended drawings, wherein: 
           [0022]      FIG. 1  is an exemplary structure diagram illustrating the LCD panel according to one aspect of the invention; 
           [0023]      FIG. 2A  illustrates one state of the structure when the LCD panel in  FIG. 1  has not been pressed, while  FIG. 2B  illustrates another state as such LCD panel has been pressed; 
           [0024]      FIG. 3  is an exemplary structure diagram illustrating the LCD panel according to another aspect of the invention; 
           [0025]      FIG. 4  is a circuit schematic diagram of implementing the press inspection and image display in the LCD panel of  FIG. 3 ; and  FIG. 4A  illustrates the exemplary inspection circuit of the circuit schematic diagram of  FIG. 4 ; 
           [0026]      FIG. 5  is a flow chart of a first embodiment of performing the press inspection by the inspection circuit of  FIG. 4A ; and 
           [0027]      FIG. 6  is a flow chart of a second embodiment of performing the press inspection by the inspection circuit of  FIG. 4A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    One or more currently preferred embodiments have been described by way of example. It will be apparent to the skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims. 
         [0029]    Seen from the screen function of the LCD panel, all TFT-LCD panels may be substantially divided into two types: contact-based panels and noncontact-based panels. For the contact-based panels, the user may directly touch the certain position in the screen, so that the system receives the response information and executes various operations. As a result, it is a more convenient and comfortable experience. During this interaction, the LCD panel should inspect and determine if the panel is pressed, besides that it displays the image in some display cells by controlling the scan lines and the data lines. 
         [0030]      FIG. 1  is an exemplary structure diagram illustrating the LCD panel according to one aspect of the invention. 
         [0031]    An LCD panel includes a plurality of pixel cells  10 , each pixel cell  10  includes a sense line  100 , a scan line  102 , a data line  104 , a scan line or a common line  106 , a readout TFT  108 , a display TFT  110 , display electrodes  112 ,  114  and  116 , a conductive layer  118  and a photo spacer  120 . The pixel cell  10  includes a display cell  101  and a sensor cell  103 , the display cell includes the display TFT  110  and display electrode  116  and the sensor cell  103  includes readout TFT  108 , display electrodes  112 ,  114 , a conductive layer  118  and a photo spacer  120 . 
         [0032]    In a similar way, the gate electrode of TFT  110  is electrically connected to the scan line  102 , the source electrode of TFT  110  is electrically connected to the data line  104 , and the drain electrode of TFT  110  is electrically connected to the display electrode  116 . It should be understood that, TFT  110  is used to display image, and here the relevant description is omitted. 
         [0033]    The gate electrode of TFT  108  is electrically connected to the scan line  102 , the source electrode of TFT  108  is electrically connected to the sense line  100 , and the drain electrode of TFT  108  is electrically connected to the display electrode  112 . As described above, the readout TFT  108  and display TFT  110  are disposed on the array substrate, and the liquid crystal molecules are located between the array substrate  202  and an opposite substrate  204 , which is opposite to the array substrate  202 , referring to  FIG. 2A . The photo spacer  120  is on the opposite substrate  204 , and its bottom surface is in contact with the opposite substrate, while its top surface protrudes towards the array substrate and does not contact with the array substrate. The conductive layer  118  is on the top surface of the photo spacer  120 . When the pixel cell  10  is pressed down, the display electrodes  112  and  114  electrically connect together through the conductive layer  118 . In this embodiment, the conductive layer  118  serves as a circuit path linking the display electrode  112  and the display electrode  114 . Therefore, unlike the conventional techniques, it must be electrically connected to the common electrode and the transparent conductive film layer must be formed on the sidewall of the photo spacer. In this embodiment, since the display electrode  114  connects with the scan line  106 , then the pixel cell  10  will be determined to appear in pressed state when the display electrode  112  positioned on the sensor cell  103  is inspected at a low voltage level. It should be understood by the skilled in the art, the respective source electrode and drain electrode of TFT  108  and TFT  110  are interchangeable. For example, the drain electrode of TFT  108  may also connect with the sense line  100 , and the source electrode of TFT  108  connects with the display electrode  112 . It should be further understood that, the display electrode  114  is not restricted to electrically connect to the scan line  106  adjacent to the scan line  102 , it may connect with a reference power source, such as the storage capacitance bottom electrode of the pixel cell  10 . In other words, when the voltage level from the sensor of the display electrode  112  is equal to that of the display electrode  114 , it means that the display cell has been pressed. 
         [0034]      FIG. 2A  is an exemplary diagram illustrating the state when the LCD panel as shown in  FIG. 1  has not been pressed, while  FIG. 2B  illustrates the state of such LCD panel having been pressed. In  FIG. 2A , only a patterned transparent conductive film layer  200  is sputtered on the part of the surface of the opposite substrate  204 , and the transparent conductive film layer  200  is connected to the common electrode, to load the common voltage VCOM. The photo spacer  120  is formed on the opposite substrate, and the conductive layer  118  is disposed on the top surface of the spacer. The transparent conductive film layer  200  and the conductive layer  118  are made of a transparent material such as ITO or IZO. It should be emphasized that, ITO conductive layer  118  is only needed to form on the top surface of the photo spacer  120  rather than the sidewall. Thus, the climbing ability of ITO material, which is formed on the sidewall of the photo spacer  120 , is no longer a specific requirement, so that the fabrication process will be increasingly simplified. When the pixel cell  10  is not pressed, the display electrode  112  and display electrode  114  stay in an electrically insulation state, and the voltage inspected by the sensor cell  103  will have no change. 
         [0035]    When the pixel cell  10  is pressed, as shown in  FIG. 2B , the photo spacer  120  moves towards the array substrate  202 , so that the display electrode  112  electrically connects to the display electrode  114  via the conductive layer  118 . As the display electrode  114  connects to the scan line  106  ( FIG. 1 ), when the scan line  102  is enabled to open the readout TFT  108  and display TFT  110 , the scan line  106  remains a low voltage level. Therefore, the display electrode  112  electrically connecting to the display electrode  114  also remains the low voltage level. As a result, we can determine if the pixel cell  10  is pressed by inspecting the voltage of the display electrode  112  of the sensor cell  103  in real time. It should be understood by the skilled in the art, the conductive layer  118  on the top surface of the photo spacer  120  is electrically connected to the display electrodes  112  and  114  when the pixel cell  10  is pressed. That is, once a reference power source is provided to connect with the display electrode  114 , whether the pixel cell  10  is pressed can be inspected by the display electrode  112  of the sensor cell  103 . For such consideration, the display electrode  114  is not limited to electrically connect to the next scan line  106 , and it may also connect to the other reference power source, such as the common electrode. 
         [0036]    In the LCD panel of  FIG. 1 , the conductive layer  118  on the top surface of the photo spacer  120  serves as a switch, and the display electrodes  112  and  114  are electrically connected by use of the conductive layer  118 . In the sense, the realization that display electrodes  112  and  114  are electrically connected or electrically insulated is not limited to use the photo spacer  120 . Since the display electrode  114  is connected to the scan line  106 , we can determine that the pixel cell  10  is pressed according to the voltage (i.e., low voltage level) from the sensor on the display electrode  112 . Comparatively, the prior art not only requires sputtering an ITO transparent conductive layer on the total surface of the opposite substrate, but requires sputtering the ITO transparent conductive layer on the sidewall and top surface of the photo spacer, and thereby the fabrication process is very complex. 
         [0037]    As the conductive layer  118  is insulated with the common electrode  200  of the opposite substrate, the voltage inspected by the sensor on the display electrode  112  is not correlated to the common voltage VCOM, so the common electrode power source in the system is unnecessary to restrain as a direct current (DC) drive mode, for example, it may also use an alternative current (AC) drive mode, to reduce the power consumption. In addition, the display electrode linking with the readout TFT  108  is divided into display electrode  112  and display electrode  114 , which will improve the pixel aperture ratio of the panel. 
         [0038]    The above illustrates one embodiment of the LCD panel according to the invention. In the LCD panel of  FIG. 1 , display TFT  110 , data line  104 , display electrode  116 , scan lines  102  and  106  are used to control the display cell  101  to display the image in different gray scales; while the readout TFT  108 , sense line  100 , display electrodes  112  and  114 , conductive layer  118 , photo spacer  120  and scan lines  102  and  106  are used to inspect whether the pixel cell  10  has been pressed. Here, the display TFT and the readout TFT respectively perform the pixel display and the press inspection, and they are substantially driven and controlled by individual structures. Thus, the LCD panel needs to increase the additional sense lines and a plurality of readout TFTs, inspecting whether the pixel is pressed and displays the image in different gray scales. 
         [0039]    In another embodiment of the LCD panel of the invention,  FIG. 3  illustrates an exemplary structure of LCD panel. The LCD panel includes a plurality of pixel cells  30 , each pixel cell  30  includes a data line/sense line  300 , a scan line  302 , a next scan line  304  adjacent to scan line  302 , a readout/display TFT  306 , two display electrodes  308  and  310 , a conductive layer  312 , and a photo spacer  314 . Unlike the LCD panel  10 , the data lines and sense lines of the LCD panel utilizes a multiplex design, and the readout TFT and the display TFT are also designed as a multiplex structure. When the switch of the LCD panel (not shown) remains iii an open state or a closed state, the source electrode (or drain electrode) of the TFT correspondingly connects to the inspection circuit or the data driver. 
         [0040]    The conductive layer  312  is disposed over the display electrodes  308  and  310 , where the display electrode  308  is normally insulated to the display electrode  310 . When the photo spacer  314  is pressed, one part of the conductive layer  312  contacts with the display electrode  308 , and the other part contacts with the display electrode  310 . Thus, the connection relationship between the display electrodes  308  and  310  transforms the electrical insulation state to the electrical conductive state through the conductive layer  312 . Preferably, the display electrode  310  is electrically connected to the scan line  304 . And when the pixel is pressed, the display electrode  308  remains a low level voltage, and thereby we can determine that the pixel has been pressed by inspecting the voltage level of the display electrode  308 . In this embodiment, the conductive layer  312  is made of conductive materials, such as IZO or ITO transparent materials, which is located on the top surface of the photo spacer  314 . 
         [0041]      FIG. 4  is a circuit schematic diagram of implementing the press inspection and image display in the LCD panel of  FIG. 3 , and  FIG. 4A  illustrates the exemplary inspection circuit of the circuit schematic diagram of  FIG. 4 . The circuit structure includes a scan line  400 , a TFT  402 , a switch  404 , a data line  406 , a data driving circuit  407  and an inspection circuit  408 . The gate electrode of the TFT  402  electrically connects to the scan line  400 , and the source (or drain) electrode of the TFT  402  electrically connects to one terminal of the switch  404 , and the drain (or source) electrode of the TFT  402  electrically connects to the pixel electrode (shown as the compensation capacitance Cst and the liquid crystal capacitance Clc in  FIG. 4 ). 
         [0042]    When the switch  404  is handed over, the source (or drain) electrode of the TFT  402  is electrically connected to the data driving circuit  407  through the data line  406 . And the gate electrode of the TFT  402  is open and the image data is sent into the display electrode via the data line  406 , to display the image. Further, when the switch  404  is handed over, the source (or drain) electrode of the TFT  402  electrically connects to the inspection circuit  408  through the data line  406 , and the electrical signal from the display electrode is transmitted to the inspection circuit  408 , when the display cell is pressed. 
         [0043]    In one embodiment of the invention, we can inspect the current signal flowing through the display electrode, and generate the corresponding voltage signal by the current/voltage conversion circuit to make a comparison. In another embodiment, we can also inspect the voltage signal of the display electrode, and compare it to the reference voltage so as to determine whether the display cell is pressed. 
         [0044]    In the following description, we will illustrate in detail the inspection method of the display cells according to the inspection circuit structure in  FIG. 4A . Moreover,  FIG. 5  is a flow chart of a first embodiment of performing the press inspection with respect to the current signal, and  FIG. 6  is a flow chart of a second embodiment of performing the press inspection with respect to the voltage signal. 
         [0045]    In step  500 , open the scan line  400 , and enable the gate electrode of the TFT  402 , to remain a conductive circuit path from the source electrode of the TFT  402  to the drain electrode of the TFT  402 . Then, continue to execute step  502 , hand over the switch  404 , and connect the display electrode to the resistor via the switch. Specifically, one terminal of the switch  404  is connected to the source electrode of the TFT, and the other terminal contacts with the resistor, which is positioned before the inspection circuit  408 . In step  504 , the current signal flowing from the display electrode is sent into the resistor. And thereafter begin to execute the step  506 . The current signal is transformed into the voltage signal and input into the inspection circuit  408 . In the following step  508 , compare the input voltage to the threshold voltage, to determine whether the display cell of the LCD panel is pressed or not. For example, the inspection circuit may have a voltage comparator, which is used to compare the input voltage to the threshold voltage. Specifically, with reference to the voltage comparator in  FIG. 4A , a first input terminal of the voltage comparator connects to the display electrode via the switch, and a second input terminal of the voltage comparator electrically connects to a reference voltage. Preferably, the inspection circuit further comprises a resistor, disposed between the first input terminal and the switch. Finally, in step  510 , if we determine that the display cell has been pressed, then the inspection circuit  408  sends out a control signal, and performs the subsequent operations. 
         [0046]    In a similar way, the inspection method based on the voltage signal will be also described as follows. In step  600 , open the scan line  400 , and enable the gate electrode of the TFT  402 , to remain a conductive circuit path from the source electrode of the TFT  402  to the drain electrode of the TFT  402 . Then, continue to execute step  602 , hand over the switch  404 , and connect the display electrode to the inspection circuit via the switch. At this time, one terminal of the switch  404  is connected to the source electrode of the TFT  402 , and the other terminal contacts with the inspection circuit  408 . In step  604 , the voltage signal of the display electrode is sent into the inspection circuit  408 . And thereafter begin to execute the step  606 , compare the input voltage to the threshold voltage. For example, the inspection circuit may have a voltage comparator, which is used to compare the voltage therebetween. Finally, in step  608 , if we determine that the display cell has been pressed, then the inspection circuit  408  sends out a control signal, and performs the follow operations. 
         [0047]    In the LCD panel of the present invention, a single TFT can be used to implement both the press inspection and the image display, thereby to reduce greatly the number of the readout TFTs in the LCD panel as well as improve significantly the pixel aperture ratio. In addition, the common electrode source of the LCD panel may be supplied in a DC drive mode, or may be supplied in an AC drive mode, to reduce the power consumption. 
         [0048]    It will be understood that the above description of embodiments is given by way of example only. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.