Abstract:
The present invention relates to a touch sensing apparatus. The touch sensing apparatus of the present invention includes a first sensing electrode arranged on a rear surface of a window to sense the touch of a user on the window covering a display screen, a second sensing electrode superimposed onto the first sensing electrode with an insulating layer interposed therebetween, and a buffer for transmitting voltage of the first sensing electrode side to the second sensing electrode side. The touch sensing apparatus of the present invention is capable of effectively cutting off noise signals generated from a display module and keeping touch sensitivity at a high level.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a touch sensing apparatus, and more particularly, to a touch sensing apparatus with a noise signal shielding structure and a parasitic capacitance prevention structure. 
       BACKGROUND ART 
       [0002]    A touch sensing apparatus may be used as an input apparatus to sense a touch of a user applied to a specific position. Generally, the touch sensing apparatus may be configured to sense a touch based on a change in electrical characteristics caused by the touch of the user. 
         [0003]      FIG. 1  illustrates an example of a plane structure of a conventional touch sensing panel. The touch sensing panel of  FIG. 1  includes a window  10  to accommodate a touch input, and sensing electrodes  15  that are arranged in regular intervals on a rear surface of the window  10 . Each of the sensing electrodes  15  of  FIG. 1  may be connected to one of M signal lines  11 , and one of N signal lines  12 . Here, the M signal lines  11  and the N signal lines  12  may be respectively used to identify horizontal positions and vertical positions where touches occur. 
         [0004]    As shown in  FIGS. 2 and 3 , a touch sensing panel may be implemented as a touch screen panel that is installed on a front surface of a display apparatus, such as a Liquid Crystal Display (LCD) module  20 . Here, a sensing electrode  15  of the touch screen panel may be exposed to a noise signal generated from the LCD module  20 . The noise signal may have influence on a performance of a touch screen, for example, may cause the touch screen to incorrectly recognize a touch of a user, or to obtain inaccurate touch position information. 
         [0005]    To prevent the noise signal, the touch screen panel may be mounted away from the LCD module  20  by a predetermined interval, as shown in  FIG. 2 . In other words, the noise signal may be attenuated by an air gap  16 . Since an influence of the noise signal is reduced as the air gap  16  increases in size, ensuring a large air gap  16  may be advantageous in blocking noise. However, actually, there are many cases where it is impossible to ensure a sufficient air gap  16  to block the noise signal due to a limitation in design based on a slim design of an electronic device. 
         [0006]    Accordingly, to more closely shield against the noise signal, a scheme of providing a shielding layer  18  as shown in  FIG. 3  is becoming widespread. Generally, the shielding layer  18  is provided on a rear surface of an insulating layer  17 , and is configured to cover an entire display screen of the LCD module  20 . Since the shielding layer  18  is connected to a ground pattern of an electronic device, an electric potential of the shielding layer  18  may be maintained at a ground level, regardless of a noise signal generated from the LCD module  20 . Accordingly, the air gap  16  may be reduced in size compared with that of  FIG. 2 , or may be omitted. However, when the shielding layer  18  is connected to the ground, a parasitic capacitance may be formed between the sensing electrode  15  and the shielding layer  18 , and may have influence on a touch sensing performance. The parasitic capacitance may greatly reduce a touch sensitivity in a capacitive-type touch screen, in particular. 
         [0007]    Additionally, a parasitic capacitance may be formed between two neighboring sensing electrodes  15 . For example, it is assumed that capacitances of the sensing electrodes  15  are respectively measured in sequence. In this example, when a capacitance of one of the sensing electrodes  15  is measured, another neighboring sensing electrode  15  may be switched to be connected to the ground. A parasitic capacitance may be formed as a coupling component between the sensing electrode  15  of which the capacitance is measure, and the sensing electrode  15  connected to the ground. The parasitic capacitance may also reduce the touch sensitivity, similar to the above-described parasitic capacitance formed between the sensing electrode  15  and the shielding layer  18 . 
       DETAILED DESCRIPTION OF THE INVENTION 
     Technical Goals 
       [0008]    Hereinafter, a touch sensing apparatus and a noise signal shielding apparatus according to the present invention will be described with reference to the accompanying drawings. In the following description, like or corresponding elements are denoted by like reference numerals, and overlapping descriptions will be omitted. 
         [0009]      FIG. 4  illustrates a panel section structure and a functional configuration of a touch sensing apparatus according to an embodiment of the present invention. For convenience of description, an adhesive layer used to deposit sensing electrodes  110  and shielding electrodes  130  is not shown in  FIG. 4 . 
         [0010]    The touch sensing apparatus of  FIG. 4  includes the sensing electrodes  110  formed on a rear surface of a window  100 . The window  100  may be formed of a dielectric, such as a tempered glass or acrylic, and a front surface of the window  100  may be exposed to an electronic device, to accommodate a touch of a user and to protect the sensing electrodes  110  and a display apparatus against an external environment. 
         [0011]    The sensing electrodes  110  may be formed of transparent conductive materials such as an Indium Tin Oxide (ITO), an Indium Zinc Oxide (IZO), a Zinc Oxide (ZnO), and the like. When the plurality of sensing electrodes  110  are included as shown in  FIG. 4 , or when processing into a specific shape is required, the sensing electrodes  110  may be manufactured by patterning by a photolithography scheme. The sensing electrodes  110  may be attached to the rear surface of the window  100  using an adhesive such as an Optically Clear Adhesive (OCA). 
         [0012]    The sensing electrodes  110  may be electrically connected to a touch sensing circuit unit  200 . When a user touches a specific position on the front surface of the window  100 , the touch sensing circuit unit  200  may sense the touch of the user based on a change in electrical characteristics occurring on a sensing electrode  110  that is arranged on a position corresponding to the touched position. Accordingly, the touch sensing circuit unit  200  may include an electrical circuit including a sample-and-hold circuit, an Analog-to-Digital Converter (ADC), or various registers. 
         [0013]    The touch sensing circuit unit  200  may acquire, from each of the sensing electrodes  110 , data regarding whether a touch is input, an intensity of a touch, and a touch position, and may transfer the acquired data to a coordinate calculation unit  300 . The coordinate calculation unit  300  may include a calculation circuit to calculate the touch position based on the data received from the touch sensing circuit unit  200 . 
         [0014]      FIG. 6  illustrates an example of an actual configuration of a sensing electrode  110 . As shown in  FIG. 6 , the sensing electrode  110  includes a transparent basement membrane  112  formed of insulating materials such as polyethylene terephthalate (PET), and a transparent conductive layer  111  formed on a surface of the transparent basement membrane  112 . The transparent conductive layer  111  may be formed of transparent conductive materials, such as an ITO, an IZO, and a ZnO. The transparent conductive layer  111  may be attached onto the window  100 , or the transparent basement membrane  112  may be attached onto the window  100 . A section structure of  FIG. 6  and the above description may equally be applied to the shielding electrode  130 . 
         [0015]    An insulating layer  120  may be provided on a rear surface of the sensing electrodes  110 . The insulating layer  120  may be formed of insulating materials such as PET. A basement membrane  112  of either the sensing electrode  110  or the shielding electrode  130  may be used as the insulating layer  120 , instead of the insulating layer  120  being deposited between the sensing electrodes  110  and the shielding electrodes  130 . 
         [0016]    As shown in  FIG. 5 , the shielding electrodes  130  may be formed on a rear surface of the insulating layer  120 , in identical configurations and in identical positions as the sensing electrodes  110 , so that the shielding electrodes  130  may be superimposed onto the sensing electrodes  110  with the insulating layer  120  therebetween. The shielding electrodes  130  may be formed of transparent conductive materials such as an ITO or the like, in the same manner as the sensing electrodes  110 . The sensing electrodes  110  and the shielding electrodes  130  corresponding to the sensing electrodes  110  may be respectively connected to input ports and output ports of buffers  140  having a predetermined gain. The buffer  140  may transfer a voltage of the sensing electrode  110  to the shielding electrode  130  corresponding to the sensing electrode  110 , so that the voltage of the sensing electrode  110  may be maintained to be equal to a voltage of the shielding electrode  130 . 
         [0017]    Since the sensing electrode  110  and the shielding electrode  130  that correspond to each other are maintained at the same voltage level, a parasitic capacitance may not be formed between the sensing electrode  110  and the shielding electrode  130 . The buffer  140  may transfer a voltage of the input port to the output port, however, may not transfer a voltage of the output port to the input port. Accordingly, the buffer  140  may function to prevent the sensing electrode  110  from being affected by a noise signal generated from a Liquid Crystal Display (LCD) module located on a rear surface of the touch sensing apparatus. 
         [0018]    A gain of the buffer  140  may be set to have various values as needed. A unit gain buffer  140  having a gain of ‘1’ may be used to transfer the voltage of the sensing electrode  110  to the shielding electrode  130 . Another buffer  140  having a gain other than ‘1’ may be used. In one embodiment, a buffer  140  having a gain of ‘0.5’ may be used to offset only half of a parasitic capacitance formed between the sensing electrode  110  and the shielding electrode  130 . In another embodiment, a buffer  140  having a gain of ‘0.7’ may be arranged, to improve a stability of the touch sensing apparatus. 
         [0019]    While  FIG. 4  illustrates an example of using unit gain buffers  140 , a buffer having a gain other than ‘1’ may be used as needed, as described above. When the buffer having a gain other than ‘1’ is used, a voltage of the shielding electrode  130  may be maintained at a fixed level by a voltage of the sensing electrode  110 , and an influence by the noise signal may not be transferred to the sensing electrodes  110 , thereby obtaining an effect of shielding against a noise signal generated by a display apparatus. 
         [0020]      FIG. 7  illustrates an example of a sensing principle applicable to the touch sensing apparatus according to the present invention, to explain the effect of shielding against the noise signal. As shown in  FIG. 7 , a capacitance formed when a part of a touch object, for example a fingertip of a user, touches a specific position on the window  100  may be modeled as a capacitance C t  and a human body capacitance C b . Here, the capacitance C t  may be formed in a thickness direction of the window  100 , using, as two electrode plates, the sensing electrode  110  corresponding to the specific position and a surface touched by the touch object, and using the window  100  as a dielectric. The human body capacitance C b  may be connected in series to the capacitance C t , and may be connected to the ground. Additionally, a noise signal generated from an LCD module  20  located on a rear surface of a touch screen panel may be shielded by the shielding electrode  130  and accordingly, may not have influence on a capacitance formed between the sensing electrode  110  and the touch object. Thus, the touch sensing circuit unit  200  connected to the sensing electrode  110  may stably sense a capacitance change caused by the capacitances C t  and C b , regardless of the noise signal. 
         [0021]      FIG. 8  illustrates a panel section structure and a functional configuration of a touch sensing apparatus according to another embodiment of the present invention. In the configuration of  FIG. 4 , the shielding electrodes  130  are provided in the same configuration as the sensing electrodes  110 , and a number of the shielding electrodes  130  is equal to a number of the sensing electrodes  110 . However, in the configuration of  FIG. 8 , a single shielding electrode  130  may be provided to be superimposed onto a plurality of sensing electrodes  110 . For example, a single shielding electrode  130  may be arranged to cover an entire display screen, so that the shielding electrode  130  may be superimposed onto all of the plurality of sensing electrodes  110 . Comparing an enlarged perspective diagram of  FIG. 9  with an enlarged perspective diagram of  FIG. 5 , it may be seen that a single shielding electrode  130  may be formed over an area occupied by several sensing electrodes  110 . 
         [0022]    Additionally, in the present embodiment, a buffer  140  of  FIG. 8  may be configured to selectively connect one of the plurality of sensing electrodes  110  to the shielding electrode  130 , instead of being individually included for each of the sensing electrodes  110 . To perform the selectively connecting, the buffer  140  of  FIG. 8  may include a multiplexer. 
         [0023]    For example, a switching unit  400  of  FIG. 8  may output a selection signal to select whether to transfer one of voltages of the plurality of sensing electrodes  110  connected to an input port of the buffer  140  to the shielding electrode  130  connected to an output port of the buffer  140 . The selection signal may be input to a selection signal input port of the buffer  140 . 
         [0024]    In the configuration of  FIG. 8 , a touch sensing circuit unit  200  may sequentially sense touches for each of the sensing electrodes  110 . When sensing a touch with respect to a specific sensing electrode  110 , the touch sensing circuit unit  200  may control the selection unit  400  to output the selection signal so that a voltage of the specific sensing electrode  110  may be transferred to the shielding electrode  130 . 
         [0025]    In the present embodiment, a number of buffers  140  may be reduced compared with when a buffer  140  and a shielding electrode  130  correspond one-to-one to a sensing electrode  110 , thereby reducing manufacturing costs. Additionally, an area occupied by each unit gain buffer  140  and each connection line in a touch sensing apparatus module may be reduced and accordingly, it is possible to realize compactness of the overall configuration of the touch sensing apparatus. 
         [0026]    The buffer  140  and the switching unit  400  may be integrated in a single chip configuration. When the two elements are provided in a single chip, a size of the touch sensing apparatus may be further reduced. Here, the chip may include a sensing channel terminal, together with an output terminal. The sensing channel terminal may be connected to each of the sensing electrodes  110 , and the output terminal may be used to output a voltage of a selected sensing electrode  110  passing through the buffer  140 . In the present embodiment, it is also possible to reduce a number of output terminals required when the buffer  140  and the switching unit  400  are integrated in a single chip configuration. 
         [0027]    As described above, features of the configuration of  FIG. 8  have been described based on a difference from the configuration of  FIG. 4 . Common parts between the configurations of  FIGS. 4 and 8  have been described above in detail and accordingly, the above description may also be applied to the embodiment of  FIG. 8 , or vice versa. 
         [0028]      FIG. 10  illustrates a panel section structure, and a relationship between function blocks of a touch sensing apparatus according to still another embodiment of the present invention. As described above in the embodiments of  FIGS. 4 and 8 , the input port of the buffer  140  may be connected to the sensing electrode  110 , and the output port of the buffer  140  may be connected to the shielding electrode  130  arranged in a different layer from the sensing electrode  110 . However, as shown in  FIG. 10 , an input port of a buffer  140  may be connected to a sensing electrode  110 , and an output port of the buffer  140  may be connected to each of other sensing electrodes  1101 ,  1102 , and  1103 . 
         [0029]    When a capacitance change with respect to the sensing electrode  110  is sensed, the above configuration may prevent a parasitic capacitance component from being formed between the sensing electrode  110  and the sensing electrodes  1101 ,  1102 , and  1103 . In particular, such an effect of preventing the parasitic capacitance component may be greatly exerted between the sensing electrode  110  and the sensing electrode  1101  that is located adjacent to the sensing electrode  110 . In other words, a parasitic capacitance may be prevented from being formed between the sensing electrodes  110  and  1101 , since electric potentials of the sensing electrodes  110  and  1101  may be maintained at a same level by the buffer  140 . 
         [0030]    While the buffer  140  of  FIG. 10  transfers a voltage of only the sensing electrode  110  to the sensing electrodes  1101 ,  1102 , and  1103 , another buffer  140  having the same function as the buffer  140  of  FIG. 10  may be provided with respect to all of the sensing electrodes  110 ,  1101 ,  1102 , and  1103 . Here, a switching circuit may be provided to connect an input port and an output port of a single buffer  140  to all of the sensing electrodes  110 ,  1101 ,  1102 , and  1103 , and to control a connection state between the buffer  140  and the sensing electrodes  110 ,  1101 ,  1102 , and  1103 . Accordingly, when a capacitance change is being measured for the sensing electrode  110 , the voltage of the sensing electrode  110  may be transferred to the sensing electrode  1101 . Thus, it is possible to prevent occupation of a large circuit area used to provide a buffer  140  for each of the sensing electrodes  110 ,  1101 ,  1102 , and  1103 . 
         [0031]      FIG. 11  is an enlarged perspective diagram stereoscopically illustrating the configuration of  FIG. 10 . While the above-described shielding electrode  130  is not shown in  FIG. 11 , a configuration including a shielding electrode  130  configured as shown in  FIG. 4  or  8 , and a unit gain buffer  140  configured as shown in  FIG. 4  or  8  to transfer voltages of the sensing electrodes  110 ,  1101 ,  1102 , and  1103  to the shielding electrode  130  may also be added to the present embodiment. Specifically, the plurality of sensing electrodes  110 ,  1101 ,  1102 , and  1103  arranged in a same layer may be connected to each other through the buffer  140  and thus, it is possible to prevent an occurrence of a parasitic capacitance. Additionally, it is possible to shield against noise transferred from a display module by separately arranging a shielding electrode  130  in a different layer from the sensing electrodes  110 ,  1101 ,  1102 , and  1103 . 
         [0032]    The configuration of the touch sensing apparatus according to the present invention has been described based on the panel section structure. In the touch sensing apparatus, a sensing electrode  110  may be formed with a tetragonal shape, for example the sensing electrode  15  of the conventional touch sensing panel of  FIG. 1 , or may have various shapes, such as a triangle, or a lozenge. Additionally, various plane structures may be applied to the touch sensing apparatus. For example, lattices may be arranged in horizontal and vertical directions, in the same manner as the sensing electrodes  15  of  FIG. 1 , and a single sensing electrode  110  may be provided to cover an entire display screen. In other words, it is possible to freely select the shape, the number, and the arrangement of the sensing electrode  110  of the touch sensing apparatus, without departing from the scope of the present invention. 
         [0033]    Although a few embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0034]      FIG. 1  schematically illustrates a plane structure of a conventional touch sensing apparatus. 
           [0035]      FIG. 2  schematically illustrates a section structure of a conventional touch sensing apparatus. 
           [0036]      FIG. 3  schematically illustrates a section structure of another conventional touch sensing apparatus. 
           [0037]      FIG. 4  illustrates a section structure and a functional configuration of a touch sensing apparatus according to an embodiment of the present invention. 
           [0038]      FIG. 5  is an enlarged perspective diagram illustrating a panel lamination structure of the touch sensing apparatus of  FIG. 4 . 
           [0039]      FIG. 6  is a cross-section diagram illustrating a lamination structure of a sensing electrode. 
           [0040]      FIG. 7  illustrates an example of a touch sensing principle applicable to a touch sensing apparatus according to the present invention, and an example of a noise signal shielding effect by the touch sensing apparatus. 
           [0041]      FIG. 8  illustrates a section structure and a functional configuration of a touch sensing apparatus according to another embodiment of the present invention. 
           [0042]      FIG. 9  is an enlarged perspective diagram illustrating a panel lamination structure of the touch sensing apparatus of  FIG. 8 . 
           [0043]      FIG. 10  illustrates a section structure and a functional configuration of a touch sensing apparatus according to still another embodiment of the present invention. 
           [0044]      FIG. 11  is an enlarged perspective diagram illustrating a panel lamination structure of the touch sensing apparatus of  FIG. 10 . 
       
    
    
     INDUSTRIAL APPLICABILITY 
       [0045]    According to the present invention, a touch sensing apparatus may cut off noise signals generated from a display apparatus, such as an LCD module, and may maintain a touch sensitivity at a high level. 
         [0046]    Additionally, according to the present invention, it is possible to achieve slimness of an electronic device equipped with a touch sensing apparatus, without sacrificing a touch sensitivity, thereby satisfying user&#39;s demand for a slim design. 
         [0047]    Moreover, according to the present invention, a single buffer may be shared by a plurality of sensing electrodes and thus, limited resources may be effectively used even when a number of connection lines to be arranged or a number of buffers is limited, thereby obtaining a noise signal shielding effect. 
         [0048]    Furthermore, according to the present invention, there may be provided a touch sensing apparatus that may eliminate an influence by a parasitic capacitance formed as a coupling component between neighboring sensing electrodes, to exactly recognize a touch position without reducing a touch sensitivity.