Abstract:
A touch sensing display device includes a first substrate; a second substrate parallel to the first substrate, a plurality of scanning lines and sensing lines being disposed on the second substrate, and the scanning lines being interlaced with the sensing lines; a plurality of touch switches disposed on the second substrate, each touch switch being connected between one scanning line and one sensing line in series; and a plurality of spacers disposed on the first substrate corresponding to the touch switches, respectively, each spacer having a conductive layer disposed on a bottom side facing to the corresponding touch switch, and having isolating surfaces on the other sides, wherein each touch switch has a turned-on state and a turned-off state, and the conductive layer of the spacer corresponding thereto causes said touch switch to be changed from the turned-off state to the turned-on state when a touch event is received.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a display device, and more particularly, to a touch sensing display device. 
     BACKGROUND OF THE INVENTION 
     A touch sensing display device is a display device that receives a user&#39;s input commands via a touch panel having a function of sensing touches. Generally, an adhesive material is utilized to assemble the touch panel and display device as the touch sensing display device. Nowadays, a technique for directly disposing sensors on the display device to detect a touch event has been developed. The display device utilizing this technique is called an embedded touch sensing display device. 
     Please refer to  FIG. 1 , which is a diagram showing a cross-sectional view of a structure of a conventional touch sensing display device. The conventional touch sensing display device is a liquid crystal display (LCD) device disposed with touch sensors. The LCD panel includes a thin-film transistor (TFT) array substrate  10 , a color filter (CF) substrate  20 , and a liquid crystal layer (not shown) disposed therebetween. A dielectric layer  12  and a passivation layer  14  are disposed on the TFT array substrate  10 . Indium tin oxide (ITO) layers  15 ,  25  are respectively disposed on the TFT array substrate  10  and the CF substrate  20  for serving as a pixel electrode and a common electrode to orient liquid crystal molecules. 
     A spacer  35  is disposed on the CF substrate  20 . The spacer  35  is covered by the ITO layer  25 , which is used as the common electrode. When a user touches the panel at a position where the spacer  35  is located, the spacer  35  moves downward so that the ITO layer  25  under the spacer  35  touches the ITO layer  15  on the TFT array substrate  10 . At this moment, the ITO layers  15 ,  25  contact to be shorted with each other. The ITO layer  15  is a resistive film. When the ITO layers  15 ,  25  at different positions of the panel contact to be shorted with each other, different voltages will be detected. Therefore, a two-dimensional coordinate of a touch point can be determined according to the detected voltage. 
     Please refer to  FIG. 2   a , which is a diagram showing a cross-sectional view of a structure of another conventional touch sensing display device. The same components are indicated by the same reference numbers as in  FIG. 1 . As shown in  FIG. 2   a , two separate metal pads  17  are disposed on a TFT array substrate  10 . The two metal pads  17  are disposed in correspondence to a spacer  35  on a CF substrate  20  as shown. When a user touches the panel at a position where the spacer  35  is located, the ITO layer  25  under the spacer  35  contacts both the two metal pads  17 , and thus electrically connecting the two metal pads  17 . The voltage at the ITO layer  25  serving as a common electrode is thereby transmitted to the metal pads  17 . 
     Please refer to  FIG. 2   b , showing a layout of the conventional touch sensing display device in  FIG. 2   a . As shown in  FIG. 2   b , an X independent sensing line (XL) parallel to a source line (SL) and a Y independent sensing line (YL) parallel to a gate line (GL) are disposed on the display panel. The gate line (GL) transmits a scan signal to control a thin-film transistor, and the source line (SL) transmits pixel data. The X independent sensing line (XL) and Y independent sensing line (YL) are respectively connected to the two metal pads  17 . When the ITO layer  25  contacts the two metal pads  17 , the voltage of the ITO layer  25  is transmitted to the X independent sensing line (XL) and Y independent sensing line (YL). The two-dimensional coordinate of a touch point can be determined according to a voltage variation of the X sensing line (XL) and a voltage variation of the Y sensing line (YL) on the display panel. 
     In each of the two conventional touch sensing display devices mentioned above, the voltage of the common electrode will be affected, and this leads to an unstable problem of displaying images. In addition, the lateral or peripheral side of the spacer  35  is covered by the ITO layer  25 . This will cause a fringing electric field phenomenon so that the image displaying quality is degraded. Moreover, parasitic capacitances will be generated among the X sensing line (XL), Y sensing line (YL), gate line (GL), and source line (SL). The image displaying may be abnormal when the parasitic capacitances are considerable. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a touch sensing display device for solving a problem of fringing electric field caused between a common electrode and a pixel electrode. The fringing electric field phenomenon may affect image displaying quality. 
     Another objective of the present invention is to provide a touch sensing display device for solving an unstable problem of displaying images. This problem is resulted from the common electrode of which the voltage is interfered. 
     An objective of the present invention is to provide a touch sensing display device for reducing the manufacturing cost. 
     According to the above objectives, the present invention provides a touch sensing display device including: a first substrate; a second substrate parallel to the first substrate, a plurality of scanning lines and a plurality of sensing lines being disposed on the second substrate, and the scanning lines being interlaced with the sensing lines; a plurality of touch switches disposed on the second substrate, each touch switch being connected between one of the scanning lines and one of the sensing lines in series; and a plurality of spacers disposed on the first substrate corresponding to the touch switches, respectively, each spacer having a conductive layer disposed on a bottom side facing to the corresponding touch switch, and having isolating surfaces on the other sides, wherein each touch switch has a turned-on state and a turned-off state, and the conductive layer of the spacer corresponding thereto causes said touch switch to be changed from the turned-off state to the turned-on state when a touch event is received. 
     In another aspect, the present invention provides a touch sensing display device including: a plurality of scanning lines and a plurality of sensing lines disposed on a substrate, the scanning lines being interlaced with the sensing lines; and a plurality of touch switches and a plurality of switch elements, each touch switch and each switch element being connected between one of the scanning lines and one of the sensing lines in series for controlling electrical connection between said scanning line and said sensing line, wherein each touch switch has a turned-on state and a turned-off state, and said touch switch is on the turned-on state when a touch event is received, and wherein each switch element operates according to a scan signal, and said switch element is turned on when receiving the scan signal; wherein when said touch switch receives the touch event and said switch element receives the scan signal, said touch switch and said switch element are turned on so that said scanning line and said sensing line connected to said touch switch and said switch element are electrically connected, and a voltage of the scan signal on said scanning line is superimposed to said sensing line. 
     The present invention has advantages as listed below. (1) The conductive layer is only disposed on the bottom side of the spacer. There is no conductive material disposed on the lateral or peripheral side of the spacer. Therefore, the present invention can solve the problem of fringing electric field. (2) The voltage of the common electrode on the display panel has not been interfered or disturbed. Therefore, the present invention does not lead to an unstable problem of displaying images since the voltage of the common electrode is not drifted or varied. (3) The original gate lines and source lines in the panel are utilized for determining the coordinate of a touch point. There is no need to dispose other additional sensing lines. Therefore, the manufacturing cost is reduced. (4) The switch elements disposed between the gate lines and source lines are served as current switches. When the gate lines are not scanned, the corresponding switch elements are turned off. Therefore, since the corresponding switch elements are turned off, the voltage of the corresponding source lines will not be affected even though touch events occur thereon. Therefore, images on the screen can be updated normally. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in details in conjunction with the appending drawings. 
         FIG. 1  is a diagram showing a cross-sectional view of a structure of a conventional touch sensing display device. 
         FIG. 2   a  is a diagram showing a cross-sectional view of a structure of another conventional touch sensing display device. 
         FIG. 2   b  is a diagram showing a layout of the conventional touch sensing display device in  FIG. 2   a.    
         FIG. 3  is a diagram showing a cross-sectional view of a structure of a touch sensing display device of the present invention. 
         FIG. 4   a  is a diagram showing a layout of a touch sensing display device implemented according to the present invention. 
         FIG. 4   b  shows a top view of the components in the touch sensing display device in  FIG. 4   a.    
         FIG. 5  is a diagram illustrating the operation principle to determine a position of touch point for the touch sensing display device in  FIG. 4   a  implemented according to the present invention. 
         FIG. 6   a  is a diagram showing a timing chart of scan signals on the gate lines (GL) in  FIG. 5 . 
         FIG. 6   b  is a diagram showing the relationship between voltage and time for a Sn+1 source line in  FIG. 5 . 
         FIG. 6   c  is a diagram showing a comparison result outputted from a voltage comparator in  FIG. 5 . 
         FIG. 7   a  is a diagram showing a layout of another touch sensing display device implemented according to the present invention. 
         FIG. 7   b  shows a top view of the components in the touch sensing display device in  FIG. 7   a.    
         FIG. 8  is a diagram illustrating the operation principle to determine a position of touch point for the touch sensing display device in  FIG. 7   a  implemented according to the present invention. 
         FIG. 9   a  is a diagram showing a timing chart of scan signals on the gate lines (GL) in  FIG. 8 . 
         FIG. 9   b  is a diagram showing the relation between voltage and time for a Sn+1 source line in  FIG. 8 . 
         FIG. 9   c  is a diagram showing a comparison result outputted from the voltage comparator in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to  FIG. 3 , which is a diagram showing a cross-sectional view of a structure of a touch sensing display device of the present invention. The touch sensing display device mainly has a mechanical switch  70  and a switch element  40  both disposed on each pixel area of the display panel. The mechanical switch  70  is utilized for detecting whether a touch event occurs on the pixel area. The switch element  40  is a current switch. The function of the switch element  40  in the entire touch control circuit will be described later. 
     As shown in  FIG. 3 , it shows an example in which the mechanical switch  70  and switch element  40  are disposed in a liquid crystal display (LCD) panel. The LCD panel includes a thin-film transistor (TFT) array substrate  10 , a color filter (CF) substrate  20 , and a liquid crystal layer  19  disposed therebetween. A black matrix (BM)  21  is disposed on the CF substrate  20  for concealing the light. As shown in  FIG. 3 , the mechanical switch  70  mainly includes a spacer  35 , a conductive layer  36 , and a touch switch  30 . The spacer  35  is an isolator disposed on the CF substrate  20 . The touch switch  30  has two separate metal pads disposed on the TFT array substrate  10 . The conductive layer  36  is disposed on a bottom side of the spacer  35  and is disposed facing to the two metal pads of the touch switch  30 . The conductive layer  36  and the metal pads are separated with an appropriate distance. When the mechanical switch  70  receives a touch event which may be done by a hand, fingertip, or other objects, a displacement of the spacer  35  is generated under the strain (e.g. a downward pressed force). This displacement causes the conductive layer  36  to contact both the two metal pads, and thus the two metal pads are electrically connected. At this moment, the touch switch  30  is turned on. When the spacer  35  is released or no more undergoes the force, the spacer  35  moves back to the original position. The conductive layer  36  and the metal pads are separated. At this moment, the touch switch is turned off. 
     In the present invention, the conductive layer  36  is only disposed on the bottom side of the spacer  35 . There is no conductive material disposed on the lateral or peripheral side of the spacer  35 . Therefore, the conductive layer  36  will not affect an electric field distribution when the liquid crystal molecules are oriented by the electric field for displaying images. The present invention can solve the problem of fringing electric field, and thus improving the image quality of the LCD panel. 
     Generally, an indium tin oxide (ITO) layer  25  is disposed on the CF substrate  20  for serving as a common electrode of the LCD panel. The pixel electrode on the TFT array substrate  10  is also an ITO film. A parallel electric field is generated between the pixel electrode and the common electrode to orient liquid crystal molecules. In the present invention, a position of a touch point is not determined according to a voltage variation of the common electrode. The voltage of the common electrode is not interfered or disturbed. Therefore, the present invention does not lead to an unstable problem of displaying images since the voltage of the common electrode is not drifted or varied. The operation principle of the present invention to determine a position of a touch point will be described later. 
     In the present invention, the switch element  40  is a current switch. The switch element  40  may be implemented by a diode, or preferably, a metal oxide semiconductor (MOS) diode. As shown in  FIG. 3 , the switch element  40  is a MOS diode that is implemented by a metal oxide semiconductor field effect transistor (MOSFET) in which a gate and a source (or drain) are connected. As shown in  FIG. 3 , the MOSFET on the TFT array substrate  10  includes a first metal layer  11 , a dielectric layer  12 , a second metal layer  13 , and a passivation layer  14 . The gate of the MOSFET is formed by the first metal layer  11  which can be aluminum (Al) or other conductive materials. The source and drain of MOSFET is formed by the second metal layer  13  which can be composite metal materials such as Mo/Al/Mo, or other single or composite conductive materials. The dielectric layer  12  is formed between the first metal layer  11  and the second metal layer  13 . The dielectric layer  12  can be silicon nitride or silicon oxide. The passivation layer  14  is for protecting the MOSFET. The passivation layer  14  can be silicon nitride, silicon oxide, organic layer, or other dielectric materials. 
     As shown in  FIG. 3 , an indium tin oxide (ITO) layer  15  is utilized as a conductor to electrically connect the gate and source (or drain) of the MOSFET. After the gate and source (or drain) are electrically connected, the MOSFET operates as a diode, which is able to conduct an electric current in only one direction. The MOSFET having the gate and source (or drain) thereof connected together is called a MOS diode. The ITO layer  15  may be formed by patterning an ITO film in the process of manufacturing the pixel diode of display panel. 
     In addition, the touch switch  30  and the switch element  40  on the TFT array substrate  10  are connected in series. As shown in  FIG. 3 , one metal pad of the touch switch  30  is connected to the drain (or source) of the MOS diode. The two metal pads of the touch switch  30  may be formed in manufacturing the second metal layer  13 . 
     The operation principle to determine a position of a touch point in the present invention will be described below. Two implementations, respectively utilizing (1) gate lines and source lines (2) gate lines and X independent sensing lines to detect touch points, are provided below for illustrative purpose. It is noted that the present invention is not limited to the two implementations. 
     (1) Utilizing Gate Lines and Source Lines to Detect Touch Points: 
     Please refer to  FIG. 4   a  and  FIG. 4   b .  FIG. 4   a  is a diagram showing a layout of a touch sensing display device implemented according to the present invention.  FIG. 4   b  shows a top view of the components in the touch sensing display device in  FIG. 4   a . Generally, a display panel has a plurality of pixel areas divided by a plurality of interlaced gate lines (GL) and source lines (SL). Each pixel area includes at least red (R), green (G), and blue (B) sub-pixel areas. Each sub-pixel area (R, or G, or B) corresponds to a thin-film transistor  50 . The thin-film transistor  50  is served as a switch for controlling to input pixel data. It is noted that  FIG. 4   a  shows an example in which one touch switch  30  and one switch element  40  are disposed in correspondence to one pixel area. In practice, there are lots of touch switches  30  and switch elements  40  distributed over the display panel. In addition, one touch switch  30  and one switch element  40  may correspond to two or more than two pixel areas. 
     As shown in  FIG. 4   a  and  FIG. 4   b , the touch switch  30  and the switch element  40  are connected between the gate line (GL) and source line (SL) in series for controlling the electrical connection of the gate line (GL) and source line (SL). The touch switch  30  and the switch element  40  are connected to one gate line (GL) and one source line (SL) for one pixel area (or more than one pixel area). As shown in  FIG. 4   a , the gate line (GL), switch element  40 , touch switch  30 , and source line (SL) are connected in sequence. More specifically, the touch switch  30  has two metal pads  33 . The two metal pads  33  are respectively connected to the source line (SL) and the drain (or source) of the MOS diode. The gate and source (or drain) of the MOS diode are connected together, and also connected to the gate line (GL). The conductive layer  36  of the spacer  35  shown in  FIG. 3  is able to turn the touch switch  30  on. The structure and connection as to the touch switch  30  and switch element  40  are also illustrated in  FIG. 3 . 
     Please refer to  FIG. 5 ,  FIG. 6   a ,  FIG. 6   b , and  FIG. 6   c .  FIG. 5  is a diagram illustrating the operation principle to determine a position of touch point for the touch sensing display device implemented according to the present invention.  FIG. 6   a  is a diagram showing a timing chart of scan signals on the gate lines (GL).  FIG. 6   b  is a diagram showing the relation between voltage and time for a Sn+1 source line.  FIG. 6   c  is a diagram showing a comparison result outputted from a voltage comparator. As shown in  FIG. 5  and  FIG. 6   a , scan signals are transmitted to the gate lines (GL). When a scan signal applied to a gate line (GL) is on a high-level voltage (Vgh), the thin-film transistor  50  will be turned on. At this moment, pixel data will be transmitted to the pixel area corresponding to the gate line (GL) by the corresponding source line (SL). Therefore, the digital data of images is updated. When the gate line (GL) is scanned, the high-level voltage of the scan signal also turns on the switch element  40 . Otherwise, when the gate line (GL) is not scanned and the scan signal is at a low-level voltage, the switch element  40  is turned off. In addition, when receiving a touch event, the touch switch  30  is turned on. When the panel is touched by a user at a position, i.e. a touch point, the touch switch  30  corresponding to the touch point is turned on. When the touch point is scanned, the switch element  40  corresponding to the touch point is also turned on. At this moment, the corresponding gate line (GL) and source line (SL) are electrically connected, and the high-level voltage of the scan signal on the corresponding gate line (GL) is superimposed to the corresponding source line (SL). The source line (SL) corresponding to the position of touch point is thereby varied in voltage. 
     As shown in  FIG. 5 ,  FIG. 6   a ,  FIG. 6   b , and  FIG. 6   c , when a touch event occurs at a position where a Gn+1 gate line and a Sn+1 source line are interlaced, and the Gn+1 gate line happened to be scanned, the touch switch  30  and switch element  40  corresponding to the position are turned on. At this moment, the high-level voltage of the scan signal on the Gn+1 gate line is superimposed to the Sn+1 source line. The voltage of the Sn+1 source line is thereby raised. Moreover, the source lines (SL) on the display panel are connected to an end of a voltage comparator  62 . Another end of the voltage comparator  62  is inputted with a reference voltage (Vref). The voltage comparator  62  compares the voltage (Vs 1 ) of a source line (SL) and the reference voltage (Vref), and then outputs a comparison result. When the voltage (Vs 1 ) of the source line (SL) is greater than the reference voltage (Vref), the comparator  62  determines that a touch event has occurred at the position where the source line (SL) is located. As shown in  FIG. 6   b , the voltage (Vs 1 ) of the Sn+1 source line is greater than the reference voltage (Vref). Therefore, the voltage comparator  62  outputs a comparison result with a high-level voltage as shown in  FIG. 6   b . The high-level voltage of the comparison result represents that a touch event has occurred at the Sn+1 source line. The X position of the touch point can be directly obtained according to the position where the Sn+1 source line is located on the display panel. When the touch point is determined by the voltage comparator  62 , the touch point happened to be scanned. Therefore, the Y position of the touch point can be obtained by resolving or analyzing the timing of the scan signal on the gate line (GL). A two-dimensional coordinate (X, Y) of the touch point on the display panel are thereby obtained. 
     In this implementation, it is necessary to dispose only the current switches triggered by scan signals and the mechanical switches in the pixel areas of the display panel for detecting touch events. The original gate lines and source lines in the panel are utilized for determining the coordinate of touch point. There is no need to dispose other sensing lines. Therefore, the manufacturing cost is reduced. In addition, this implementation will not lead to the problem of increasing parasitic capacitances, and thereby image displaying is maintained stable. If additional sensing lines are disposed, parasitic capacitances may reside between the sensing lines and the gate lines or between the sensing lines and the source lines. The parasitic capacitances due to the additional sensing lines may interfere with the gate lines and source lines. 
     In this implementation, the switch elements disposed between the gate lines and source lines are served as current switches. When the gate lines are not scanned, the corresponding switch elements are turned off. Therefore, since the corresponding switch elements are turned off, the voltage of the corresponding source lines will not be affected even though touch events occur thereon. Therefore, images on the screen can be updated normally. When the panel is touched by a user, an area including many touch points is touched actually. If the switch elements are not disposed in the panel, these touch points will affect the voltage of the source lines at the same time so that images on the screen may be disturbed and may not be updated well. 
     (2) Utilizing Gate Lines and X-Sensing Lines to Detect Touch Points: 
     The difference between this implementation and the previous implementation is that additional sensing lines are disposed in the panel for this implementation. As shown in  FIG. 7   a  and  FIG. 7   b , the touch switch  30  and switch element  40  are connected between the gate line (GL) and an X independent sensing line (XL) in series. More specifically, the touch switch  30  has two metal pads  33 . The two metal pads  33  are respectively connected to the X independent sensing line (XL) and the drain (or source) of MOS diode. The gate and source (or drain) of MOS diode are electrically connected. 
     As shown in  FIG. 8 , the X independent sensing lines (XL) on the display panel are connected to a resistor  61 . The X independent sensing lines (XL) are also connected to an end of a voltage comparator  62 . Another end of the voltage comparator  62  is inputted with a reference voltage (Vref). The voltage comparator  62  compares the voltage of the X independent sensing line (XL) and the reference voltage (Vref), and then outputs a comparison result. 
       FIG. 9   a  is a diagram showing a timing chart of scan signals on the gate lines (GL).  FIG. 9   b  is a diagram showing the relation between voltage and time for a Sn+1 source line.  FIG. 9   c  is a diagram showing a comparison result outputted from the voltage comparator  62 . In this implementation, the gate line (GL), switch element  40 , touch switch  30 , and X independent sensing line (XL) are connected in sequence. When the touch switch  30  and switch element  40  are turned on, a high-level voltage of the scan signal on the corresponding gate line (GL) is superimposed to the corresponding X independent sensing line (XL). The voltage (Vs 1 ) of the source line (SL) will not be affected by a voltage variation of the X independent sensing line (XL). As shown in  FIG. 9   b , the voltage of a Sn+1 source line will not be affected by the X independent sensing line (XL). 
     In this implementation, X independent sensing lines are parallel to source lines. The voltage of source lines will not be affected by the high-level voltage of scan signals on the gate lines. Therefore, pixel data transmitted by the source lines will not be affected. In addition, the X independent sensing lines may increase the accuracy of the position determination operated by the voltage comparator. 
     The present invention is not limited to the two above-mentioned implementations. The present invention may also be implemented as (3) utilizing source lines and additional independent scanning lines parallel to gate lines, and (4) utilizing additional independent scanning lines and additional independent sensing lines interlaced each other to detect a touch point. In case (3), the touch switch  30  and switch element  40  are connected between a source line and an independent scanning line in series. In case (4), the touch switch  30  and switch element  40  are connected in series between an independent scanning line and an independent sensing line. The above-mentioned additional independent scanning lines can be connected to a gate driving circuit originally disposed on the display panel, or to an additional gate driving circuit for driving or transmitting the scan signals. 
     While the preferred embodiments of the present invention have been illustrated and described in detail, various modifications and alterations can be made by persons skilled in this art. The embodiment of the present invention is therefore described in an illustrative but not restrictive sense. It is intended that the present invention should not be limited to the particular forms as illustrated, and that all modifications and alterations which maintain the spirit and realm of the present invention are within the scope as defined in the appended claims.