Patent Publication Number: US-8982064-B2

Title: Liquid crystal display device provided with a sensing electrode for sending a touch of a user

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the Korean Patent Application No. 10-2010-0098253 filed on Oct. 8, 2010, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device provided with a sensing electrode for sensing a touch of a user. 
     2. Discussion of the Related Art 
     A liquid crystal display device is widely used in various fields of notebook computers, monitors, spacecraft, aircraft, and etc. owing to advantages of low power consumption based on a low driving voltage and portability. 
     The liquid crystal display device includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the lower and upper substrates. In the liquid crystal display device, an alignment state of liquid crystal molecules in the liquid crystal layer is controlled based on whether or not an electric field is applied thereto, and light transmittance is controlled according to the alignment state of liquid crystal molecules, whereby images are displayed thereon. 
     It is general that a mouse or key board is used as an input means of the liquid crystal display device. However, a touch screen, which can allow a user to directly input information using a finger or pen, is mainly applied to a navigation system, a portable terminal and electric home appliances. 
     Hereinafter, a related art liquid crystal display device provided with a touch screen will be described with reference to the accompanying drawings. 
       FIG. 1  is a cross-sectional view illustrating the related art liquid crystal display device. 
     As shown in  FIG. 1 , the related art liquid crystal display device includes a liquid crystal panel  10  and a touch screen  20 . 
     The liquid crystal panel  10  displays images, and includes a lower substrate  12 , an upper substrate  14 , and a liquid crystal layer  16  formed between these substrates  12  and  14 . 
     The touch screen  20  is formed on the liquid crystal panel  10  to sense a touch of a user, and includes a touch substrate  22 , a first sensing electrode  24  formed below the touch substrate  22 , and a second sensing electrode  26  formed on the touch substrate  22 . 
     The first sensing electrode  24  is arranged below the touch substrate  22  in a horizontal direction, and the second sensing electrode  26  is arranged on the touch substrate  22  in a vertical direction. Accordingly, if the user touches a predetermined position, capacitance between the first sensing electrode  24  and the second sensing electrode  26  is varied at the touched position. As a result, the position where capacitance is varied is sensed, whereby the touch position of the user can be sensed. 
     However, in the aforementioned related art liquid crystal display device, since the touch screen  20  is separately formed on the liquid crystal panel  20 , the overall thickness of the liquid crystal display device is increased by the touch screen  20 . For this reason, problems occur in that fabricating process steps are complicated and the fabricating cost is increased. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a liquid crystal display device that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An advantage of the present invention is to provide a liquid crystal display device in which a sensing electrode for sensing a touch of a user is built in a liquid crystal panel so as not to require a separate touch screen on the liquid crystal panel, whereby the overall thickness of the liquid crystal display device is reduced, fabricating process steps are simplified, and the fabricating cost is reduced. 
     Additional advantages and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a liquid crystal display device comprises gate and data lines arranged to cross each other on a substrate to define a pixel region; a pixel electrode formed in the pixel region; a common electrode forming an electric field together with the pixel electrode and sensing a touch of a user; and a sensing line electrically connected with the common electrode, wherein the common electrode includes a plurality of first common electrodes for sensing any one of a touch position of X axis and a touch position of Y axis and a plurality of second common electrodes for sensing the other one of the touch positions of X axis and Y axis, and the sensing line is not electrically connected with the plurality of second common electrodes but electrically connected with the plurality of first common electrodes. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a cross-sectional view illustrating the related art liquid crystal display device; 
         FIG. 2   a  is a plane view illustrating a lower substrate for a liquid crystal display device according to the first embodiment of the present invention,  FIG. 2   b  is a cross-sectional view taken along line A-A of  FIG. 2   a , and  FIG. 2   c  is a cross-sectional view taken along line B-B of  FIG. 2   a;    
         FIG. 3   a  is a plane view illustrating a lower substrate for a liquid crystal display device according to the second embodiment of the present invention,  FIG. 3   b  is a cross-sectional view taken along line A-A of  FIG. 3   a , and  FIG. 3   c  is a cross-sectional view taken along line C-C of  FIG. 3   a;    
         FIG. 4   a  is a plane view illustrating a lower substrate for a liquid crystal display device according to the third embodiment of the present invention, and  FIG. 4   b  is a cross-sectional view taken along line A-A of  FIG. 4   a ; and 
         FIG. 5   a  is a plane view illustrating a lower substrate for a liquid crystal display device according to the fourth embodiment of the present invention,  FIG. 5   b  is a cross-sectional view taken along line A-A of  FIG. 5   a , and  FIG. 5   c  is a cross-sectional view taken along line C-C of  FIG. 5   a.    
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 2   a  is a plane view illustrating a lower substrate for a liquid crystal display device according to the first embodiment of the present invention,  FIG. 2   b  is a cross-sectional view taken along line A-A of  FIG. 2   a , and  FIG. 2   c  is a cross-sectional view taken along line B-B of  FIG. 2   a.    
     Referring to  FIG. 2   a , especially a partially enlarged view marked with an arrow, the liquid crystal display device according to the first embodiment of the present invention includes a substrate  100 , a gate line  110 , a data line  120 , a thin film transistor T, a pixel electrode  130 , a common electrode  140 , and a sensing line  160 . 
     The gate line  110  is arranged on the substrate  100  in a first direction, for example, X axis direction, and the data line  120  is arranged on the substrate  100  in a second direction, for example, Y axis direction. In this way, the gate line  110  and the data line  120  cross each other to define a plurality of pixel regions. Although the gate line  110  and the data line  120  are arranged in a straight line as shown, they may be arranged in a bent line. 
     The thin film transistor T is a switching element, and is formed in a region where the gate line  110  and the data line  120  cross each other. The thin film transistor T includes a gate electrode  112 , a semiconductor layer  117 , a source electrode  122  and a drain electrode  124 . The gate electrode  112  is extended from the gate line  110 , the source electrode  122  is extended from the data line  120 , and the drain electrode  124  faces the source electrode  122 . 
     The aforementioned thin film transistor T may have various structures such as a bottom gate structure where the gate electrode  112  is arranged below the semiconductor layer  117  and a top gate structure where the gate electrode  112  is arranged over the semiconductor layer  117 . Also, various modifications may be made in types of the respective electrodes. 
     The pixel electrode  130  is formed in each of the pixel regions, and is electrically connected with the drain electrode  124  of the thin film transistor T. Particularly, the pixel electrode  130  may directly be connected with the drain electrode  124 . But, it is not limited to the above example. 
     The common electrode  140  serves to drive the liquid crystal layer by forming an electric field together with the pixel electrode  130 . Particularly, the common electrode  140  includes one or more slits  145  in the pixel region. Accordingly, a fringe field is formed between the pixel electrode  130  and the common electrode  140  through the slits  145 , and the liquid crystal may be driven by the fringe field. 
     Meanwhile, the common electrode  140  serves to drive the liquid crystal by forming the electric field together with the pixel electrode  130  as described above and also serves as a sensing electrode for sensing a touch position of a user. In order to serve as the sensing electrode, the common electrode  140  is not formed on the entire surface of the substrate  100  but formed in a predetermined pattern. 
     In other words, as shown in  FIG. 2   a , the common electrode  140  includes a plurality of first common electrodes  141  and a plurality of second common electrodes  142 . At this time, a position of Y axis touched by the user may be sensed by the first common electrodes  141 , and a position of X axis touched by the user may be sensed by the second common electrodes  142 . 
     The sizes of the first and second common electrodes  141  and  142  may be formed appropriately considering a touch surface of a finger or pen. For example, the first common electrode  141  may be formed to include several tens of pixels or several hundreds of pixels. 
     Hereinafter, the first and second common electrodes  141  and  142  serving as the sensing electrodes will be described in more detail. 
     First of all, in order to sense the position of the X axis touched by the user, the plurality of second common electrodes  142  are spaced apart from one another at predetermined intervals in X axis direction. Also, the second common electrodes  142  are longitudinally formed in a Y axis direction, and their end is connected with a sensing circuit although not shown. 
     Accordingly, if the user touches a predetermined position, the sensing circuit recognizes the second common electrode  142  of which capacitance is varied, among the plurality of second common electrodes  142 . As a result, the position of the X axis touched by the user can be sensed. 
     Next, in order to sense the position of the Y axis touched by the user, the plurality of first common electrodes  141  are spaced apart from one another at predetermined intervals in Y axis direction. However, if the first common electrodes  141  are longitudinally formed in X axis direction, the first common electrode  141  and the second common electrode  142  are electrically connected with each other, whereby the positions of the X axis and the Y axis touched by the user cannot be sensed. Accordingly, the first common electrodes  141  are not formed longitudinally in X axis direction but spaced apart from one another at predetermined intervals in X axis direction. In other words, as shown, the second common electrode  142  is formed between the first common electrodes  141  in X axis direction, whereas the second common electrode  142  is not formed between the first common electrodes  141  in Y axis direction. 
     Since the plurality of first common electrodes  141  are spaced apart from one another at predetermined intervals in X axis direction by interposing the second common electrode  142  therebetween as described above, it is required that the plurality of first common electrodes  141  are electrically connected with one another. 
     The sensing line  160  is extended in X axis direction as above to electrically connect the first common electrodes  141  with one another. Although not shown, the end of the sensing line  160  is connected with the sensing circuit. 
     Accordingly, if the user touches a predetermined position, the sensing circuit recognizes the first common electrode  141  of which capacitance is varied, among the plurality of first common electrodes  141 . As a result, the position of the Y axis touched by the user can be sensed. 
     Meanwhile, although the sensing line  160  serves to electrically connect the first common electrodes  141  arranged in X axis direction with one another, the first common electrode  141  should not be connected with the second common electrode  142  electrically due to the sensing line  160 . Accordingly, although the sensing line  160  is electrically connected with the first common electrodes  141 , it is not connected with the second common electrodes  142  electrically. 
     Meanwhile, the sensing line  160  is connected with the common electrodes  140  through a predetermined first contact hole  151 . In this case, since the first contact hole  151  is formed only in a region for the first common electrodes  141 , the sensing line  160  is electrically connected with the first common electrode  141  through the first contact hole  151  but is not connected with the second common electrode  142  electrically. 
     Meanwhile, although one sensing line  160  is connected with the first common electrode  141  as shown, a plurality of sensing lines  160  may be connected with the first common electrode  141 . Particularly, since a transparent conductive oxide having high resistance such as ITO is generally used as the first common electrode  141 , the plurality of sensing lines  160  of metal having excellent electric conductivity are preferably connected with the first common electrode  141  to reduce resistance. 
     If the sensing line  160  is formed of opaque metal having excellent electric conductivity to reduce resistance, light transmittance may be reduced due to the sensing line  160 . Accordingly, the sensing line  160  is preferably formed in a non-transmissive region through which light is not transmitted, to prevent light transmittance from being reduced. Namely, as shown in the partially enlarged view of  FIG. 2   a , the sensing line  160  is preferably formed in a region corresponding to the gate line  110 . 
     Also, although the first common electrode  141  is connected with the sensing line  160  through the two first contact holes  151  as shown, it may be connected with the sensing line  160  through one first contact hole  151  or three or more first contact holes  151 . However, in order to reduce resistance, it is preferable to increase the number of the first contact holes  151 . Also, as shown in the partially enlarged view of  FIG. 2   a , the first contact hole  151  may be formed in the region where the gate line  110  and the data line  120  cross each other. However, the position of the first contact holes  151  is not limited to the example of  FIG. 2   a.    
     It has been described that the second common electrodes  142  are longitudinally arranged in Y axis direction and the first common electrodes  141  are connected with the sensing line  160  in X axis direction. However, the second common electrodes  142  may longitudinally be arranged in X axis direction, and the first common electrodes  141  may be connected with the sensing line  160  in Y axis direction. If the sensing line  160  is extended in Y axis direction, it is preferably formed in a region corresponding to the data line  120  to prevent light transmittance from being reduced. 
     Hereinafter, a sectional structure of the liquid crystal display device according to the first embodiment of the present invention will be described with reference to  FIG. 2   b  and  FIG. 2   c.    
       FIG. 2   b  corresponds to a section of the gate line  110  taken in a vertical direction. As shown in  FIG. 2   b , the gate line  110  is formed on the substrate  100 , and a gate insulating film  115  is formed on the gate line  110 . Also, the data line  120  is formed on the gate insulating film  115  at a predetermined interval, and a first passivation film  125  is formed on the data line  120 . 
     The first common electrode  141  and the second common electrode  142  are alternately formed on the first passivation film  125 , a second passivation film  150  is formed on the first common electrode  141  and the second common electrode  142 , and the sensing line  160  is formed on the second passivation film  150 . 
     At this time, since the first contact hole  151  is formed in the second passivation film  150 , the sensing line  160  is electrically connected with the first common electrode  141  through the first contact hole  151 . Particularly, since the first contact hole  151  is formed in the region corresponding to the first common electrode  141 , the sensing line  160  is electrically connected with the first common electrode  141  but is not electrically connected with the second common electrode  142 . 
       FIG. 2   c  corresponds to a section of the pixel region taken in a vertical direction. As shown in  FIG. 2   c , the gate electrode  112  is formed on the substrate  100 , and the gate insulating film  115  is formed on the gate electrode  112 . Also, the semiconductor layer  117  is formed on the gate insulating film  115 , and source and drain electrodes  122  and  124  are formed on the semiconductor layer  117  to face each other. 
     Since the pixel electrode  130  is formed on the drain electrode  124 , the drain electrode  124  is directly connected with the pixel electrode  130 . Meanwhile, although the pixel electrode  130  may be extended to the upper surface of the drain electrode  124  as shown, it may be extended to the lower surface of the drain electrode  124 . 
     The first passivation film  125  is formed on the pixel electrode  130 , the common electrode  140  is formed on the first passivation film  125 , and a second passivation film  150  is formed on the common electrode  140 . 
     Since the common electrode  140  includes one or more slits  145  above the pixel electrode  130 , a fringe field may be formed between the pixel electrode  130  and the common electrode  140 . 
     Meanwhile, the aforementioned liquid crystal display device according to the first embodiment of the present invention may be driven by a projected cap mode such as a self cap mode or a mutual cap mode. 
     The projected cap mode allows the user to sense the positions of the X axis and the Y axis by sensing capacitance varied between the first common electrode  141  and the second common electrode  142  if the user touches a predetermined position. The projected cap mode may be divided into a self cap mode and a mutual cap mode depending on a voltage mode applied to the electrodes  141  and  142 . 
     The self cap mode is to sense the positions of the X axis and the Y axis by sensing capacitance variation between the first common electrode  141  and the second common electrode  142  when the user touches a predetermined position after simultaneously applying a voltage to the sensing lines  160  connecting the first common electrodes  141 . 
     By contrast, the mutual cap mode is to sense the positions of the X axis and the Y axis by sensing capacitance variation between the first common electrode  141  and the second common electrode  142  when the user touches a predetermined position after applying a voltage to the sensing lines  160 , which connects the first common electrodes  141 , in accordance with a time gap. In other words, the mutual cap mode means that the sensing line  160  serves as a transmission line and the common electrode  142  serves as a reception line, and has recently received more attention than the self cap mode. 
       FIG. 3   a  is a plane view illustrating a lower substrate for a liquid crystal display device according to the second embodiment of the present invention,  FIG. 3   b  is a cross-sectional view taken along line A-A of  FIG. 3   a , and  FIG. 3   c  is a cross-sectional view taken along line C-C of  FIG. 3   a.    
     The lower substrate for the liquid crystal display device according to the second embodiment of the present invention as shown in  FIG. 3   a  to  FIG. 3   c  is the same as that for the liquid crystal display device according to the first embodiment of the present invention except that a conductive line  170  is additionally connected with a plurality of second common electrodes  142 . Accordingly, the same reference numbers will be used throughout the drawings to refer to the same or like parts, and detailed description of the same or like parts will be omitted. 
     As shown in  FIG. 3   a , according to the second embodiment of the present invention, the conductive line  170  is connected with the plurality of second common electrodes  142 . 
     A transparent conductive oxide such as ITO is generally used as the second common electrode  142 . The transparent conductive oxide has a problem in that resistance is high. Accordingly, in the second embodiment of the present invention, the conductive line  170  of a metal having excellent electric conductivity is connected with the second common electrode  142  to reduce resistance of the second common electrode  142 . 
     The conductive line  170  is connected with the second common electrode  142  through a second contact hole  152 . In this case, it is preferable that more second contact holes  152  are provided to reduce resistance. 
     It is preferable that the conductive line  170  is extended in a length direction of the second common electrode  142 , i.e., Y axis direction. However, in this case, the conductive line  170  is cross-connected with the sensing line  160 , whereby short occurs. Accordingly, the conductive line  170  is formed as a discontinuous line such that it is not connected with the sensing line  160 . 
     The conductive line  170  may be formed of the same opaque metal as that of the sensing line  160  by the same process as that of the sensing line  160 . If the conductive line  170  is formed of the opaque metal, light transmittance may be reduced due to the conductive line  170 . Accordingly, the conductive line  170  is preferably formed in a non-transmissive region through which light is not transmitted, to prevent light transmittance from being reduced. Namely, as shown in the partially enlarged view of  FIG. 3   a , the conductive line  170  is preferably formed in a region corresponding to the data line  120 . 
     Although one discontinuous conductive line  170  is connected with the second common electrode  142  as shown, it is preferable that a plurality of conductive lines  170  are connected with the second common electrode  142  to minimize resistance of the second common electrode  142 . Also, it is preferable that each of the plurality of conductive lines  170  is formed in the region corresponding to the data line  120  to prevent light transmittance from being reduced. The conductive line  170  may be formed in a region corresponding to the gate line  110  as the case may be. 
       FIG. 3   b  corresponds to a section of line A-A of  FIG. 3   a , and is the same as  FIG. 2   b  of the first embodiment. Accordingly, the repeated description will be omitted. 
       FIG. 3   c  corresponds to a section of the data line  120  taken along line C-C of  FIG. 3   a  in a vertical direction. In more detail, gate lines  110  are formed on the substrate  100  at predetermined intervals, and a gate insulating film  115  is formed on the gate lines  110 . Also, a data line  120  is formed on the gate insulating film  115 , and a first passivation film  125  is formed on the data line  120 . 
     A second common electrode  142  is formed on the first passivation film  125 , and a second passivation film  150  is formed on the second common electrode  142 . 
     A sensing line  160  and a conductive line  170  are alternately formed on the second passivation film  150 . At this time, since a second contact hole  152  is formed in the second passivation film  150 , the conductive line  170  is electrically connected with the second common electrode  142  through the second contact hole  152 . 
       FIG. 4   a  is a plane view illustrating a lower substrate for a liquid crystal display device according to the third embodiment of the present invention, and  FIG. 4   b  is a cross-sectional view taken along line A-A of  FIG. 4   a.    
     The lower substrate for the liquid crystal display device according to the third embodiment of the present invention as shown in  FIG. 4   a  and  FIG. 4   b  is the same as that for the liquid crystal display device according to the first embodiment of the present invention except for a layer formed between the common electrodes  141  and  142  and the sensing line  160 . Accordingly, the same reference numbers will be used throughout the drawings to refer to the same or like parts, and repeated description of the same or like parts will be omitted. 
     In the first embodiment of the present invention as described above, the common electrodes  141  and  142  and the sensing line  160  are formed by interposing the second passivation film  150  therebetween, wherein the common electrodes  141  and  142  are formed below the second passivation film  150  and the sensing line  160  is formed over the second passivation film  150 . 
     However, in the third embodiment of the present invention, although the common electrodes  141  and  142  and the sensing line  160  are formed by interposing the second passivaiton film  150 , the first common electrodes  141  and  142  are formed over the second passivation film  150  and the sensing line  160  is formed below the second passivation film  150 . 
     Referring to  FIG. 4   b , a gate line  110  is formed on a substrate  100 , a gate insulating film  115  is formed on the gate line  110 , a data line  120  is formed on the gate insulating film  115 , and a first passivation film  125  is formed on the data line  120 . 
     The sensing line  160  is formed on the first passivation film  125 , and the second passivation film  150  is formed on the sensing line  160 . Also, the first common electrode  141  and the second common electrode  142  are alternately formed on the second passivation film  150 . 
     At this time, since the first contact hole  151  is formed in the second passivation film  150 , the sensing line  160  is electrically connected with the first common electrode  141  through the first contact hole  151 . Particularly, since the first contact hole  151  is formed in the region corresponding to the first common electrode  141 , the sensing line  160  is electrically connected with the first common electrode  141  but is not electrically connected with the second common electrode  142 . 
       FIG. 5   a  is a plane view illustrating a lower substrate for a liquid crystal display device according to the fourth embodiment of the present invention,  FIG. 5   b  is a cross-sectional view taken along line A-A of  FIG. 5   a , and  FIG. 5   c  is a cross-sectional view taken along line C-C of  FIG. 5   a.    
     The lower substrate for the liquid crystal display device according to the fourth embodiment of the present invention as shown in  FIG. 5   a  to  FIG. 5   c  is the same as that for the liquid crystal display device according to the third embodiment of the present invention except that a conductive line  170  is additionally connected with a plurality of second common electrodes  142 . Accordingly, the same reference numbers will be used throughout the drawings to refer to the same or like parts, and detailed description of the same or like parts will be omitted. 
     As shown in  FIG. 5   a , according to the fourth embodiment of the present invention, since the conductive line  170  of a metal having excellent electric conductivity is connected with a plurality of second common electrodes  142 , resistance of the second common electrodes  142  may be reduced. 
     The conductive line  170  is connected with the second common electrode  142  through a second contact hole  152 . In this case, it is preferable that more second contact holes  152  are provided to reduce resistance. 
     The conductive line  170  is formed as a discontinuous line such that it is not connected with the sensing line  160 . 
     It is preferable that the conductive line  170  is formed in a non-transmissive region through which light is not transmitted, i.e., a region corresponding to the data line, to prevent light transmittance from being reduced. It is also preferable that a plurality of conductive lines  170  are connected with the second common electrode  142  to minimize resistance of the second common electrode  142 . 
       FIG. 5   b  corresponds to a section of line A-A of  FIG. 5   a , and is the same as  FIG. 4   b  of the third embodiment. Accordingly, the repeated description will be omitted. 
       FIG. 5   c  corresponds to a section of the data line  120  taken along line C-C of  FIG. 5   a  in a vertical direction. In more detail, gate lines  110  are formed on the substrate  100  at predetermined intervals, and a gate insulating film  115  is formed on the gate lines  110 . Also, a data line  120  is formed on the gate insulating film  115 , and a first passivation film  125  is formed on the data line  120 . 
     A sensing line  160  and a conductive line  170  are alternately formed on the first passivation film  125 . 
     A second passivation film  150  is formed on the conductive line  170  and the sensing line  160 , and a second common electrode  142  is formed on the second passivation film  150 . At this time, since a second contact hole  152  is formed in the second passivation film  150 , the conductive line  170  is electrically connected with the second common electrode  142  through the second contact hole  152 . 
     The lower substrate constituting the liquid crystal display device according to the present invention has been described in detail as above. Accordingly, the liquid crystal display device according to the present invention includes the lower substrate, an upper substrate provided with a color filter, and a liquid crystal layer formed between both substrates. 
     The upper substrate may include light shielding layers for shielding light from leaking to a region other than the pixel region, color filter layers of red R, green G and blue B formed between the light shielding layers, and an overcoat layer formed on the color filter layers. Various modifications known in the art may be made in the above structure of the upper substrate. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 
     As described above, the liquid crystal display device according to the present invention has the following advantages. 
     Since the common electrode used to form an electric field for driving a liquid crystal is used as a sensing electrode for sensing a touch of a user, a separate touch screen on the liquid crystal panel is not required unlike the related art, whereby the overall thickness of the liquid crystal display device is reduced, fabricating process steps are simplified, and the fabricating cost is reduced.