Patent Publication Number: US-10775943-B2

Title: Pressure sensor, touch input device including same, and pressure detection method using same

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present application is a U.S. national stage application under 35 U.S.C. § 371 of PCT Application No. PCT/IB2016/051916, filed Apr. 5, 2016, the disclosure of which is incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a pressure sensor for pressure detection and a touch input device including the same, and more particularly to a pressure sensor which is applied to a touch input device configured to detect a touch position and is capable of detecting a touch pressure, the touch input device including the same, and a pressure detection method using the same. 
     BACKGROUND ART 
     Various kinds of input devices are being used to operate a computing system. For example, the input device includes a button, key, joystick and touch screen. Since the touch screen is easy and simple to operate, the touch screen is increasingly being used to operate the computing system. 
     The touch screen may constitute a touch surface of a touch input device including a touch sensor panel which may be a transparent panel including a touch-sensitive surface. The touch sensor panel is attached to the front side of a display screen, and then the touch-sensitive surface may cover the visible side of the display screen. The touch screen allows a user to operate the computing system by simply touching the touch screen by a finger, etc. Generally, the computing system recognizes the touch and a position of the touch on the touch screen and analyzes the touch, and thus, performs operations in accordance with the analysis. 
     Here, there is a demand for a touch input device capable of detecting not only the touch position according to the touch on the touch screen but a pressure magnitude of the touch. 
     DISCLOSURE 
     Technical Problem 
     The object of the present invention is to provide a pressure sensor for pressure detection, a touch input device including the same, and a pressure detection method using the same. 
     Technical Solution 
     One embodiment is a touch input device capable of detecting a pressure of a touch on a touch surface. The touch input device includes: a display module; and a pressure sensor which is disposed at a position where a distance between the pressure sensor and a reference potential layer is changeable according to the touch on the touch surface. The distance is changeable according to a pressure magnitude of the touch. The pressure sensor outputs a signal including information on a capacitance which is changed according to the distance. The pressure sensor includes a plurality of electrodes to form a plurality of channels. The pressure magnitude of the touch is detected on the basis of a change amount of the capacitance detected in each of the channels. According to the embodiment of the present invention, it is possible to provide a pressure sensor for pressure detection, a touch input device including the same, and a pressure detection method using the same. In addition, according to the embodiment of the present invention, it is possible to provide the pressure sensor having a high-pressure detection accuracy of the touch and the touch input device including the pressure sensor. 
     Another embodiment is a pressure sensor including a first insulation layer and a second insulation layer and a first electrode and a second electrode which are located between the first insulation layer and the second insulation layer. A capacitance between the first electrode and the second electrode, which is changed according to a relative distance change between the pressure sensor and a reference potential layer spaced apart the pressure sensor is detected. The pressure sensor is configured such that a magnitude of a pressure which causes the distance change through the capacitance is detected. The pressure sensor is configured to include a plurality of the first electrodes and a plurality of the second electrodes and to form a plurality of channels. The pressure sensor is used to detect the pressure magnitude of a touch on the basis of a change amount of the capacitance detected in each of the channels. 
     Further another embodiment is a pressure sensor including a first insulation layer and a second insulation layer and an electrode located between the first insulation layer and the second insulation layer. A capacitance between the electrode and a reference potential layer, which is changed according to a relative distance change between the pressure sensor and the reference potential layer spaced apart the pressure sensor is detected. The pressure sensor is configured such that a magnitude of a pressure which causes the distance change through the capacitance is detected. The pressure sensor is configured to include a plurality of the electrodes and to form a plurality of channels. The pressure sensor is used to detect the pressure magnitude of a touch on the basis of a change amount of the capacitance detected in each of the channels. 
     Advantageous Effects 
     According to the embodiment of the present invention, it is possible to provide a pressure sensor for pressure detection, a touch input device including the same, and a pressure detection method using the same. 
     In addition, according to the embodiment of the present invention, it is possible to provide the pressure sensor having a high-pressure detection accuracy of the touch and the touch input device including the pressure sensor. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of a configuration of a capacitance type touch sensor panel and the operation thereof; 
         FIGS. 2 a  to 2 e    are conceptual views showing a relative position of the touch sensor panel with respect to a display panel in a touch input device according to the embodiment; 
         FIGS. 3 a  to 3 h    are cross sectional views of an exemplary pressure sensor including a pressure electrode according to the embodiment of the present invention; 
         FIG. 3 i    is a view showing a capacitance change amount according to a distance change between an electrode layer and a reference potential layer according to the embodiment of the present invention; 
         FIG. 4 a    is a cross sectional view of the touch input device of a first example, to which the pressure sensor and pressure detection module according to the embodiment of the present invention can be applied; 
         FIG. 4 b    shows an optical layer of a backlight unit in the touch input device according to the embodiment; 
         FIG. 4 c    is a cross sectional view of the touch input device of a second example, to which the pressure sensor and pressure detection module according to the embodiment of the present invention can be applied; 
         FIG. 5 a    shows a relative distance between the reference potential layer and the pressure sensor of the first example, which are included in the touch input device before a pressure is applied to the touch input device, and  FIG. 5 b    show a relative distance between the reference potential layer and the pressure sensor of the first example, which are included in the touch input device after a pressure is applied to the touch input device; 
         FIG. 5 c    shows a relative distance between the reference potential layer and the pressure sensor of the second example, which are included in the touch input device before a pressure is applied to the touch input device, and 
         FIG. 5 d    show a relative distance between the reference potential layer and the pressure sensor of the second example, which are included in the touch input device after a pressure is applied to the touch input device; 
         FIG. 5 e    shows the arrangement of pressure sensors of a third example, which is included in the touch input device; 
         FIG. 6 a    is a cross sectional view showing a portion of the touch input device to which the pressure sensor has been attached according to a first method; 
         FIG. 6 b    is a plan view of the pressure sensor to be attached to the touch input device in accordance with the first method; 
         FIG. 6 c    is a cross sectional view showing a portion of the touch input device to which the pressure sensor has been attached according to a second method; 
         FIGS. 7 a  to 7 e    show pressure electrode patterns included in the pressure sensor for pressure detection according to the embodiment of the present invention; 
         FIGS. 8 a  and 8 b    show a relation between a magnitude of a touch pressure and a saturated area in the touch input device to which the pressure sensor has been applied according to the embodiment of the present invention; 
       Cross sections of the pressure sensor according to the embodiment of the present invention are shown in (a) to (d) of  FIG. 9 ; 
         FIGS. 10 a  and 10 b    show an attachment method of the pressure sensor according the embodiment of the present invention; 
         FIGS. 11 a  to 11 c    show how the pressure sensor is connected to a touch sensing circuit in accordance with the embodiment of the present invention; 
         FIGS. 12 a  to 12 d    show that the pressure sensor according to the embodiment of the present invention includes a plurality of channels; 
         FIGS. 13 a  to 13 c    show forms of a first electrode and a second electrode included in the pressure sensor according to the embodiment of the present invention; 
         FIG. 13 d    shows the form of the first electrode included in the pressure sensor according to the embodiment of the present invention; 
         FIG. 14 a    is a view showing that a pressure is applied to a predetermined position in the pressure sensor shown in  FIG. 13   d;    
         FIG. 14 b    is a cross sectional view showing a form in which the touch input device is bent when the touch pressure is applied to a touch surface corresponding to a position “A” of  FIG. 14   a;    
         FIG. 14 c    is a cross sectional view showing a form in which the touch input device is bent when the touch pressure is applied to a touch surface corresponding to a position “C” of  FIG. 14   a;    
         FIG. 15  is a view showing a scaling factor assigned to each first electrode in the pressure sensor shown in  FIG. 13   d;    
         FIG. 16 a    is a graph for describing, when the pressure is applied to the position shown in  FIG. 14 a   , a relation between a volume change amount of the touch input device and a magnitude of the applied pressure; 
         FIG. 16 b    is a cross sectional view showing the volume change amount of the touch input device shown in  FIG. 14   b;    
         FIG. 16 c    is a cross sectional view showing the volume change amount of the touch input device shown in  FIG. 14   c;    
         FIG. 17 a    is a partial perspective view for describing a form in which the touch input device is deformed when the pressure is applied to the touch input device; 
         FIG. 17 b    is a view for describing the estimation of the volume change amount of the touch input device when the pressure is applied to the touch input device; 
         FIG. 17 c    is a cross sectional view of  FIG. 17   b;    
         FIG. 18 a    shows an equivalent circuit of a device for sensing a pressure capacitance of the pressure sensor having the forms shown in  FIGS. 13 a    to  13   c;    
         FIG. 18 b    shows an equivalent circuit of a device for sensing the pressure capacitance of the pressure sensor shown in  FIG. 13   d;    
         FIG. 19 a    is a view for describing a case where a pressure is applied to a position of the pressure sensor shown in  FIG. 14 a   , which corresponds to a position “D” of  FIG. 19   a;    
         FIG. 19 b    is a graph for describing the calculation of a pressure value when the pressure is applied to the position “D” shown in  FIG. 19 a   ; and 
         FIGS. 20 a  to 20 c    are flowcharts for describing examples of a method for detecting the magnitude of the touch pressure by using a plurality of channels in the touch input device according to the embodiment of the present invention. 
     
    
    
     MODE FOR INVENTION 
     The following detailed description of the present invention shows a specified embodiment of the present invention and will be provided with reference to the accompanying drawings. The embodiment will be described in enough detail that those skilled in the art are able to embody the present invention. It should be understood that various embodiments of the present invention are different from each other and need not be mutually exclusive. Similar reference numerals in the drawings designate the same or similar functions in many aspects. 
     Hereinafter, a pressure sensor for pressure detection and a touch input device to which a pressure detection module including the pressure sensor according to an embodiment of the present invention can be applied will be described with reference to the accompanying drawings. Hereinafter, while a capacitance type touch sensor panel  100  is exemplified below, the touch sensor panel  100  capable of detecting a touch position in any manner may be applied. 
       FIG. 1  is a schematic view of a configuration of the capacitance type touch sensor panel  100  which is included in the touch input device to which a pressure sensor  440  and the pressure detection module including the pressure sensor  440  according to the embodiment of the present invention can be applied, and the operation of the touch sensor panel. Referring to  FIG. 1 , the touch sensor panel  100  may include a plurality of drive electrodes TX 1  to TXn and a plurality of receiving electrodes RX 1  to RXm, and may include a drive unit  120  which applies a driving signal to the plurality of drive electrodes TX 1  to TXn for the purpose of the operation of the touch sensor panel  100 , and a sensing unit  110  which detects whether or not the touch occurs and/or the touch position by receiving a sensing signal including information on the capacitance change amount changing according to the touch on the touch surface of the touch sensor panel  100 . 
     As shown in  FIG. 1 , the touch sensor panel  100  may include the plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm. While  FIG. 1  shows that the plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm of the touch sensor panel  100  form an orthogonal array, the present invention is not limited to this. The plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm has an array of arbitrary dimension, for example, a diagonal array, a concentric array, a 3-dimensional random array, etc., and an array obtained by the application of them. Here, “n” and “m” are positive integers and may be the same as each other or may have different values. The magnitude of the value may be changed depending on the embodiment. 
     As shown in  FIG. 1 , the plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm may be arranged to cross each other. The drive electrode TX may include the plurality of drive electrodes TX 1  to TXn extending in a first axial direction. The receiving electrode RX may include the plurality of receiving electrodes RX 1  to RXm extending in a second axial direction crossing the first axial direction. 
     In the touch sensor panel  100  according to the embodiment of the present invention, the plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm may be formed in the same layer. For example, the plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm may be formed on the same side of an insulation layer (not shown). Also, the plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm may be formed in the different layers. For example, the plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm may be formed on both sides of one insulation layer (not shown) respectively, or the plurality of drive electrodes TX 1  to TXn may be formed on a side of a first insulation layer (not shown) and the plurality of receiving electrodes RX 1  to RXm may be formed on a side of a second insulation layer (not shown) different from the first insulation layer. 
     The plurality of drive electrodes TX 1  to TXn and the plurality of receiving electrodes RX 1  to RXm may be made of a transparent conductive material (for example, indium tin oxide (ITO) or antimony tin oxide (ATO) which is made of tin oxide (SnO 2 ), and indium oxide (In 2 O 3 ), etc.), or the like. However, this is only an example. The drive electrode TX and the receiving electrode RX may be also made of another transparent conductive material or an opaque conductive material. For instance, the drive electrode TX and the receiving electrode RX may be formed to include at least any one of silver ink, copper or carbon nanotube (CNT). Also, the drive electrode TX and the receiving electrode RX may be made of metal mesh or nano silver. 
     The drive unit  120  according to the embodiment of the present invention may apply a driving signal to the drive electrodes TX 1  to TXn. In the embodiment of the present invention, one driving signal may be sequentially applied at a time to the first drive electrode TX 1  to the n-th drive electrode TXn. The driving signal may be applied again repeatedly. This is only an example. The driving signal may be applied to the plurality of drive electrodes at the same time in accordance with the embodiment. 
     Through the receiving electrodes RX 1  to RXm, the sensing unit  110  receives the sensing signal including information on a capacitance (Cm)  101  generated between the receiving electrodes RX 1  to RXm and the drive electrodes TX 1  to TXn to which the driving signal has been applied, thereby detecting whether or not the touch has occurred and where the touch has occurred. For example, the sensing signal may be a signal coupled by the capacitance (CM)  101  generated between the receiving electrode RX and the drive electrode TX to which the driving signal has been applied. As such, the process of sensing the driving signal applied from the first drive electrode TX 1  to the n-th drive electrode TXn through the receiving electrodes RX 1  to RXm can be referred to as a process of scanning the touch sensor panel  100 . 
     For example, the sensing unit  110  may include a receiver (not shown) which is connected to each of the receiving electrodes RX 1  to RXm through a switch. The switch becomes the on-state in a time interval during which the signal of the corresponding receiving electrode RX is sensed, thereby allowing the receiver to sense the sensing signal from the receiving electrode RX. The receiver may include an amplifier (not shown) and a feedback capacitor coupled between the negative (−) input terminal of the amplifier and the output terminal of the amplifier, i.e., coupled to a feedback path. Here, the positive (+) input terminal of the amplifier may be connected to the ground or a reference voltage. Also, the receiver may further include a reset switch which is connected in parallel with the feedback capacitor. The reset switch may reset the conversion from current to voltage that is performed by the receiver. The negative input terminal of the amplifier is connected to the corresponding receiving electrode RX and receives and integrates a current signal including information on the capacitance (CM)  101 , and then converts the integrated current signal into voltage. The sensing unit  110  may further include an analog-digital converter (ADC) (not shown) which converts the integrated data by the receiver into digital data. Later, the digital data may be input to a processor (not shown) and processed to obtain information on the touch on the touch sensor panel  100 . The sensing unit  110  may include the ADC and processor as well as the receiver. 
     A controller  130  may perform a function of controlling the operations of the drive unit  120  and the sensing unit  110 . For example, the controller  130  generates and transmits a drive control signal to the drive unit  120 , so that the driving signal can be applied to a predetermined drive electrode TX 1  at a predetermined time. Also, the controller  130  generates and transmits the drive control signal to the sensing unit  110 , so that the sensing unit  110  may receive the sensing signal from the predetermined receiving electrode RX at a predetermined time and perform a predetermined function. 
     In  FIG. 1 , the drive unit  120  and the sensing unit  110  may constitute a touch detection device (not shown) capable of detecting whether the touch has occurred on the touch sensor panel  100  according to the embodiment of the present invention or not and/or where the touch has occurred. The touch detection device according to the embodiment of the present invention may further include the controller  130 . The touch detection device according to the embodiment of the present invention may be integrated and implemented on a touch sensing integrated circuit (IC, not shown) in a touch input device  1000  including the touch sensor panel  100 . The drive electrode TX and the receiving electrode RX included in the touch sensor panel  100  may be connected to the drive unit  120  and the sensing unit  110  included in the touch sensing IC through, for example, a conductive trace and/or a conductive pattern printed on a circuit board, or the like. The touch sensing IC may be located on a circuit board on which the conductive pattern has been printed. According to the embodiment, the touch sensing IC may be mounted on a main board for operation of the touch input device  1000 . 
     As described above, a capacitance (C) with a predetermined value is generated at each crossing of the drive electrode TX and the receiving electrode RX. When an object like a finger approaches close to the touch sensor panel  100 , the value of the capacitance may be changed. In  FIG. 1 , the capacitance may represent a mutual capacitance (Cm). The sensing unit  110  senses such electrical characteristics, thereby being able to sense whether the touch has occurred on the touch sensor panel  100  or not and where the touch has occurred. For example, the sensing unit  110  is able to sense whether the touch has occurred on the surface of the touch sensor panel  100  comprised of a two-dimensional plane consisting of a first axis and a second axis. 
     More specifically, when the touch occurs on the touch sensor panel  100 , the drive electrode TX to which the driving signal has been applied is detected, so that the position of the second axial direction of the touch can be detected. Likewise, when the touch occurs on the touch sensor panel  100 , the capacitance change is detected from the reception signal received through the receiving electrode RX, so that the position of the first axial direction of the touch can be detected. 
     The mutual capacitance type touch sensor panel as the touch sensor panel  100  has been described in detail in the foregoing. However, in the touch input device  1000  according to the embodiment of the present invention, the touch sensor panel  100  for detecting whether or not the touch has occurred and where the touch has occurred may be implemented by using not only the above-described method but also any touch sensing method like a self-capacitance type method, a surface capacitance type method, a projected capacitance type method, a resistance film method, a surface acoustic wave (SAW) method, an infrared method, an optical imaging method, a dispersive signal technology, and an acoustic pulse recognition method, etc. 
     Hereinafter, a component corresponding to the drive electrode TX and the receiving electrode RX for detecting whether or not the touch has occurred and/or the touch position can be referred to as a touch sensor. 
     In the pressure sensor and the touch input device  1000  to which the pressure detection module including the pressure sensor can be applied according to the embodiment of the present invention, the touch sensor panel  100  may be positioned outside or inside a display panel  200 A. The display panel  200 A of the touch input device  1000  according to the embodiment of the present invention may be a display panel included in a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting diode (OLED), etc. Accordingly, a user may perform the input operation by touching the touch surface while visually identifying an image displayed on the display panel. Here, the display panel  200 A may include a control circuit which receives an input from an application processor (AP) or a central processing unit (CPU) on a main board for the operation of the touch input device  1000  and displays the contents that the user wants on the display panel. Here, the control circuit for the operation of the display panel  200 A may be mounted on a second printed circuit board (hereafter, referred to as a second PCB) ( 210 ) in  FIGS. 10 a  to 12 c   . Here, the control circuit for the operation of the display panel  200 A may include a display panel control IC, a graphic controller IC, and a circuit required to operate other display panels  200 A. 
       FIGS. 2 a  to 2 e    are conceptual views showing a relative position of the touch sensor panel  100  with respect to the display panel  200 A in the touch input device to which the pressure sensor  440  according to the embodiment can be applied. First, the relative position of the touch sensor panel  100  with respect to the display panel  200 A using an LCD panel will be described with reference to  FIGS. 2 a    to  2   c.    
     As shown in  FIGS. 2 a  to 2 c   , the LCD panel may include a liquid crystal layer  250  including a liquid crystal cell, a first substrate  261  and a second substrate  262  which are disposed on both sides of the liquid crystal layer  250  and include electrodes, a first polarizer layer  271  formed on a side of the first substrate  261  in a direction facing the liquid crystal layer  250 , and a second polarizer layer  272  formed on a side of the second substrate  262  in the direction facing the liquid crystal layer  250 . Here, the first substrate  261  may be color filter glass, and the second substrate  262  may be TFT glass. Also, the first substrate  261  and/or the second substrate  262  may be a plastic substrate. 
     It is clear to those skilled in the art that the LCD panel may further include other configurations for the purpose of performing the displaying function and may be transformed. 
       FIG. 2 a    shows that the touch sensor panel  100  of the touch input device  1000  is disposed outside the display panel  200 A. The touch surface of the touch input device  1000  may be the surface of the touch sensor panel  100 . In  FIG. 2 a   , the top surface of the touch sensor panel  100  is able to function as the touch surface. Also, according to the embodiment, the touch surface of the touch input device  1000  may be the outer surface of the display panel  200 A. In  FIG. 2 a   , the bottom surface of the second polarizer layer  272  of the display panel  200 A is able to function as the touch surface. Here, in order to protect the display panel  200 A, the bottom surface of the display panel  200 A may be covered with a cover layer (not shown) like glass. 
       FIGS. 2 b  and 2 c    show that the touch sensor panel  100  of the touch input device  1000  is disposed inside the display panel  200 A. Here, in  FIG. 2 b   , the touch sensor panel  100  for detecting the touch position is disposed between the first substrate  261  and the first polarizer layer  271 . Here, the touch surface of the touch input device  1000  is the outer surface of the display panel  200 A. The top surface or bottom surface of the display panel  200 A in  FIG. 2 b    may be the touch surface.  FIG. 2 c    shows that the touch sensor panel  100  for detecting the touch position is included in the liquid crystal layer  250 , that is to say, the touch sensor panel  100  is disposed between the first substrate  261  and the second substrate  262 . Here, the touch surface of the touch input device  1000  is the outer surface of the display panel  200 A. The top surface or bottom surface of the display panel  200 A in  FIG. 2 c    may be the touch surface. In  FIGS. 2 b  and 2 c   , the top surface or bottom surface of the display panel  200 A, which can be the touch surface, may be covered with a cover layer (not shown) like glass. 
     Next, a relative position of the touch sensor panel  100  with respect to the display panel  200 A using an OLED panel will be described with reference to  FIGS. 2 d  and 2 e   . In  FIG. 2 d   , the touch sensor panel  100  is positioned between a polarizer layer  282  and a first substrate  281 . In  FIG. 2 e   , the touch sensor panel  100  is positioned between an organic material layer  280  and a second substrate  283 . Also, the touch sensor panel  100  is positioned between the first substrate  281  and the organic material layer  280 . 
     Here, the first substrate  281  may be made of encapsulation glass. The second substrate  283  may be made of TFT glass. Also, the first substrate  281  and/or the second substrate  283  may be plastic substrates. Since the touch sensing has been described above, the other configurations only will be briefly described. 
     The OLED panel is a self-light emitting display panel which uses a principle where, when current flows through a fluorescent or phosphorescent organic thin film and then electrons and electron holes are combined in the organic material layer, so that light is generated. The organic matter constituting the light emitting layer determines the color of the light. 
     Specifically, the OLED uses a principle in which when electricity flows and an organic matter is applied on glass or plastic, the organic matter emits light. That is, the principle is that electron holes and electrons are injected into the anode and cathode of the organic matter respectively and are recombined in the light emitting layer, so that a high energy exciton is generated and the exciton releases the energy while falling down to a low energy state and then light with a particular wavelength is generated. Here, the color of the light is changed according to the organic matter of the light emitting layer. 
     The OLED includes a line-driven passive-matrix organic light-emitting diode (PM-OLED) and an individual driven active-matrix organic light-emitting diode (AM-OLED) in accordance with the operating characteristics of a pixel constituting a pixel matrix. None of them require a backlight. Therefore, the OLED enables a very thin display module to be implemented, has a constant contrast ratio according to an angle and obtains a good color reproductivity depending on a temperature. Also, it is very economical in that non-driven pixel does not consume power. 
     In terms of operation, the PM-OLED emits light only during a scanning time at a high current, and the AM-OLED maintains a light emitting state only during a frame time at a low current. Therefore, the AM-OLED has a resolution higher than that of the PM-OLED and is advantageous for driving a large area display panel and consumes low power. Also, a thin film transistor (TFT) is embedded in the AM-OLED, and thus, each component can be individually controlled, so that it is easy to implement a delicate screen. 
     As shown in  FIGS. 2 d  and 2 e   , basically, the OLED (particularly, AM-OLED) panel includes the polarizer layer  282 , the first substrate  281 , the organic layer  280 , and the second substrate  283 . Here, the first substrate  281  may be made of encapsulation glass. The second substrate  283  may be made of TFT glass. However, they are not limited to this. The first substrate  281  and/or the second substrate  283  may be plastic substrates. 
     Also, the organic layer  280  may include a hole injection layer (HIL), a hole transport layer (HTL), an electron injection layer (EIL), an electron transport layer (ETL), and an emission material layer (EML). 
     Briefly describing each of the layers, HIL injects electron holes and is made of a material such as CuPc, etc. HTL functions to move the injected electron holes and mainly is made of a material having a good hole mobility. Arylamine, TPD, and the like may be used as the HTL. The EIL and ETL inject and transport electrons. The injected electrons and electron holes are combined in the EML and emit light. The EML represents the color of the emitted light and is composed of a host determining the lifespan of the organic matter and an impurity (dopant) determining the color sense and efficiency. This just describes the basic structure of the organic layer  280  include in the OLED panel. The present invention is not limited to the layer structure or material, etc., of the organic layer  280 . 
     The organic layer  280  is inserted between an anode (not shown) and a cathode (not shown). When the TFT becomes an on-state, a driving current is applied to the anode and the electron holes are injected, and the electrons are injected to the cathode. Then, the electron holes and electrons move to the organic layer  280  and emit the light. 
     Also, according to the embodiment, at least a portion of the touch sensor may be disposed within the display panel  200 A and at least the remaining portion of the touch sensor may be disposed outside the display panel  200 A. For example, any one of the drive electrode TX and the receiving electrode RX which constitute the touch sensor panel  100  may be disposed outside the display panel  200 A and the other may be disposed within the display panel  200 A. When the touch sensor is disposed within the display panel  200 A, an electrode for the operation of the touch sensor may be further added. In addition, various components and/or electrodes disposed within the display panel  200 A can be also used as the touch sensor for touch sensing. 
     Also, according to the embodiment, at least a portion of the touch sensor may be disposed between the first substrate  261  and  281  and the second substrate  262  and  283  and at least the remaining portion of the touch sensor may be disposed on the first substrate  261  and  281 . For example, any one of the drive electrode TX and the receiving electrode RX which constitute the touch sensor panel  100  may be disposed on the first substrate  261  and  281  and the other may be disposed between the first substrate  261  and  281  and the second substrate  262  and  283 . Here, likewise, when the touch sensor is disposed between the first substrate  261  and  281  and the second substrate  262  and  283 , an electrode for the operation of the touch sensor may be further added. In addition, various components and/or electrodes disposed between the first substrate  261  and  281  and the second substrate  262  and  283  can be also used as the touch sensor for touch sensing. 
     The second substrate  262  and  283  may be comprised of various layers including a data line a gate line, TFT, a common electrode, and a pixel electrode, etc. Specifically, when the display panel  200 A is the LCD panel, these electrical components may operate in such a manner as to generate a controlled electric field and orient liquid crystals located in the liquid crystal layer  250 . Any one of the data line, the gate line, the common electrode, and the pixel electrode included in the second substrate  262  and  283  may be configured to be used as the touch sensor. 
     The foregoing has described the touch input device  1000  including the touch sensor panel  100  capable of detecting whether or not the touch has occurred and/or the touch position. The pressure sensor  440  according to the embodiment of the present invention is applied to the aforementioned touch input device  1000 , so that it is possible to easily detect a magnitude of a touch pressure as well as whether or not the touch has occurred and/or the touch position. Hereinafter, described in detail is an example of a case of detecting the touch pressure by applying the electrode sheet according to the embodiment of the present invention to the touch input device  1000 . According to the embodiment, the touch input device to which the pressure detection module is applied may not have the touch sensor panel  100 . 
       FIG. 3 a    is an exemplary cross sectional views of the pressure sensor including a pressure electrode according to the embodiment of the present invention. For example, the pressure sensor  440  may include an electrode layer  441  between a first insulation layer  470  and a second insulation layer  471 . The electrode layer  441  may include a first electrode  450  and/or a second electrode  460 . Here, the first insulation layer  470  and the second insulation layer  471  may be made of an insulating material like polyimide. The first electrode  450  and/or the second electrode  460  included in the electrode layer  441  may include a material like copper. In accordance with the manufacturing process of the pressure sensor  440 , the electrode layer  441  and the second insulation layer  471  may be adhered to each other by means of an adhesive (not shown) like an optically clear adhesive (OCA). Also, the pressure electrodes  450  and  460  according to the embodiment may be formed by positioning a mask, which has a through-hole corresponding to a pressure electrode pattern, on the first insulation layer  470 , and then by spraying a conductive material. 
       FIG. 4 a    is a cross sectional view of the touch input device of a first example, to which the pressure sensor and the pressure detection module according to the embodiment of the present invention can be applied. 
     The cross sectional view of the touch input device  1000  shown in  FIG. 4 a    may be a cross sectional view of a portion of the touch input device  1000 . As shown in  FIG. 4 a   , the touch input device  1000  according to the embodiment of the present invention may include the display panel  200 A, a backlight unit  200 B disposed under the display panel  200 A, and a cover layer  500  disposed on the display panel  200 A. In the touch input device  1000  according to the embodiment, the pressure sensors  450  and  460  may be formed on a cover  240 . In this specification, the display panel  200 A and the backlight unit  200 B are collectively referred to as a display module  200 . FIG.  4   a  shows that the pressure sensors  450  and  460  are attached on the cover  240 . However, according to the embodiment, the pressure sensors  450  and  460  can be also attached to a configuration which is included in the touch input device  1000  and performs the same or similar function as/to that of the cover  240 . 
     The touch input device  1000  according to the embodiment of the present invention may include an electronic device including the touch screen, for example, a cell phone, a personal data assistant (PDA), a smart phone, a tablet personal computer, an MP3 player, a laptop computer, etc. 
     At least a portion of the touch sensor is included within the display panel  200 A in the touch input device  1000  according to the embodiment. Also, according to the embodiment, the drive electrode and the receiving electrode which are for sensing the touch may be included within the display panel  200 A. 
       FIG. 4 a    does not show separately the touch sensor panel  100 . However, in the touch input device  1000  according to the first example of the present invention, the lamination is made by an adhesive like the optically clear adhesive (OCA) between the touch sensor panel  100  and the display module  200  for detecting the touch position. As a result, the display color clarity, visibility and optical transmittance of the display module  200 , which can be recognized through the touch surface of the touch sensor panel  100 , can be improved. Here, the cover layer  500  may be disposed on the touch sensor panel  100 . 
     The cover layer  500  according to the embodiment may be comprised of a cover glass which protects the front side of the display panel  200 A and forms the touch surface. As shown in  FIG. 4 a   , the cover layer  500  may be formed wider than the display panel  200 A. 
     Since the display panel  200 A such as the LCD panel according to the embodiment performs a function of only blocking or transmitting the light without emitting light by itself, the backlight unit  200 B may be required. For example, the backlight unit  200 B is disposed under the display panel  200 A, includes a light source and throws the light on the display panel  200 A, so that not only brightness and darkness but also information having a variety of colors is displayed on the screen. Since the display panel  200 A is a passive device, it is not self-luminous. Therefore, the rear side of the display panel  200 A requires a light source having a uniform luminance distribution. 
     The backlight unit  200 B according to the embodiment may include an optical layer  220  for illuminating the display panel  200 A. The optical layer  220  will be described in detail with reference to  FIG. 4   b.    
     The backlight unit  200 B according to the embodiment may include the cover  240 . The cover  240  may be made of a metallic material. When a pressure is applied from the outside through the cover layer  500  of the touch input device  1000 , the cover layer  500 , the display module  200 , etc., may be bent. Here, the bending causes a distance between the pressure sensor  450  and  460  and a reference potential layer located within the display module to be changed. The capacitance change caused by the distance change is detected through the pressure sensors  450  and  460 , so that the magnitude of the pressure can be detected. Here, a pressure is applied to the cover layer  500  in order to precisely detect the magnitude of the pressure, the position of the pressure sensors  450  and  460  needs to be fixed without changing. Therefore, the cover  240  is able to perform a function of a support capable of fixing a pressure sensor without being relatively bent even by the application of pressure. According to the embodiment, the cover  240  is manufactured separately from the backlight unit  200 B, and may be assembled together when the display module is manufactured. 
     In the touch input device  1000  according to the embodiment, a first air gap  210 ′ may be included between the display panel  200 A and the backlight unit  200 B. This intends to protect the display panel  200 A and/or the backlight unit  200 B from an external impact. This first air gap  210 ′ may be included in the backlight unit  200 B. 
     The optical layer  220  and the cover  240 , which are included in the backlight unit  200 B, may be configured to be spaced apart from each other. A second air gap  230  may be provided between the optical layer  220  and the cover  240 . The second air gap  230  may be required in order to ensure that the pressure sensors  450  and  460  disposed on the cover  240  does not contact with the optical layer  220 , and in order to prevent that the optical layer  220  contacts with the pressure sensors  450  and  460  and deteriorates the performance of the optical layer  220  even though an external pressure is applied to the cover layer  500  and the optical layer  220 , the display panel  200 A, and the cover layer  500  are bent. 
     The touch input device  1000  according to the embodiment may further include supports  251  and  252  such that the display panel  200 A, the backlight unit  200 B, and the cover layer  500  are coupled to maintain a fixed shape. According to the embodiment, the cover  240  may be integrally formed with the support  251  and  252 . According to the embodiment, the support  251  and  252  may form a portion of the backlight unit  200 B. 
     The structure and function of the LCD panel  200 A and the backlight unit  200 B is a publicly known art and will be briefly described below. The backlight unit  200 B may include several optical parts. 
       FIG. 4 b    shows the optical layer  220  of the backlight unit  200 B in the touch input device according to the embodiment.  FIG. 4 b    shows the optical layer  220  when the LCD panel is used as the display panel  200 A. 
     In  FIG. 4 b   , the optical layer  220  of the backlight unit  200 B may include a reflective sheet  221 , a light guide plate  222 , a diffuser sheet  223 , and a prism sheet  224 . Here, the backlight unit  200 B may include a light source (not shown) which is formed in the form of a linear light source or point light source and is disposed on the rear and/or side of the light guide plate  222 . 
     The light guide plate  222  may generally convert lights from the light source (not shown) in the form of a linear light source or point light source into light from a light source in the form of a surface light source, and allow the light to proceed to the LCD panel  200 A. 
     A part of the light emitted from the light guide plate  222  may be emitted to a side opposite to the LCD panel  200 A and be lost. The reflective sheet  221  may be positioned below the light guide plate  222  so as to cause the lost light to be incident again on the light guide plate  222 , and may be made of a material having a high reflectance. 
     The diffuser sheet  223  functions to diffuse the light incident from the light guide plate  222 . For example, light scattered by the pattern of the light guide plate  222  comes directly into the eyes of the user, and thus, the pattern of the light guide plate  222  may be shown as it is. Moreover, since such a pattern can be clearly sensed even after the LCD panel  200 A is mounted, the diffuser sheet  223  is able to perform a function to offset the pattern of the light guide plate  222 . 
     After the light passes through the diffuser sheet  223 , the luminance of the light is rapidly reduced. Therefore, the prism sheet  224  may be included in order to improve the luminance of the light by focusing the light again. The prism sheet  224  may include, for example, a horizontal prism sheet and a vertical prism sheet. 
     The backlight unit  200 B according to the embodiment may include a configuration different from the above-described configuration in accordance with the technical change and development and/or the embodiment. The backlight unit  200 B may further include an additional configuration as well as the foregoing configuration. Also, in order to protect the optical configuration of the backlight unit  200 B from external impacts and contamination, etc., due to the introduction of the alien substance, the backlight unit  200 B according to the embodiment may further include, for example, a protection sheet on the prism sheet  224 . The backlight unit  200 B may also further include a lamp cover in accordance with the embodiment so as to minimize the optical loss of the light source. The backlight unit  200 B may also further include a frame which maintains a shape enabling the light guide plate  222 , the diffuser sheet  223 , the prism sheet  224 , a lamp (not shown), and the like, which are main components of the backlight unit  200 B, to be exactly combined together in accordance with an allowed dimension. Also, the each of the configurations may be comprised of at least two separate parts. 
     According to the embodiment, an additional air gap may be positioned between the light guide plate  222  and the reflective sheet  221 . As a result, the lost light from the light guide plate  222  to the reflective sheet  221  can be incident again on the light guide plate  222  by the reflective sheet  221 . Here, between the light guide plate  222  and the reflective sheet  221 , for the purpose of maintaining the additional air gap, the double-sided adhesive tape (DAT) may be included on the edges of the light guide plate  222  and the reflective sheet  221 . 
     As described above, the backlight unit  200 B and the display module including the backlight unit  200 B may be configured to include in itself the air gap such as the first air gap  210 ′ and/or the second air gap  230 . Also, the air gap may be included between a plurality of the layers included in the optical layer  220 . Although the foregoing has described that the LCD panel  200 A is used, the air gap may be included within the structure of another display panel. 
       FIG. 4 c    is a cross sectional view of the touch input device of a second example, to which the pressure sensor and pressure detection module according to the embodiment of the present invention can be applied.  FIG. 4 c    shows a cross section of the touch input device  1000  that further includes a substrate  300  as well as the display module  200 . In the touch input device  1000  according to the embodiment, the substrate  300 , together with a second outermost cover  320  of the touch input device  1000 , functions as, for example, a housing which surrounds a mounting space  310 , etc., where the circuit board and/or battery for operation of the touch input device  1000  are located. Here, the circuit board for operation of the touch input device  1000  may be a main board. A central processing unit (CPU), an application processor (AP) or the like may be mounted on the circuit board. Due to the substrate  300 , the display module  200  is separated from the circuit board and/or battery for operation of the touch input device  1000 . Due to the substrate  300 , electrical noise generated from the display module  200  can be blocked. According to the embodiment, the substrate  300  may be referred to as a mid-frame in the touch input device  1000 . 
     In the touch input device  1000 , the cover layer  500  may be formed wider than the display module  200 , the substrate  300 , and the mounting space  310 . As a result, the second cover  320  is formed in such a manner as to surround the display module  200 , the substrate  300 , and the mounting space  310  where the circuit board is located. Also, according to the embodiment, the pressure sensor  440  may be included between the display module  200  and the substrate  300 . 
     As with  FIG. 4 a   ,  FIG. 4 c    does not show separately the touch sensor panel  100 . However, the touch input device  1000  according to the embodiment of the present invention can detect the touch position through the touch sensor panel  100 . Also, according to the embodiment, at least a portion of the touch sensor may be included in the display panel  200 A. 
     Here, the pressure sensor  440  may be attached to the substrate  300 , may be attached to the display module  200 , or may be attached to the display module  200  and the substrate  300 . 
     As shown in  FIGS. 4 a  and 4 c   , since the pressure sensor  440  in the touch input device  1000  is disposed within the display module  200  or is disposed between the display module  200  and the substrate  300  and under the display module  200 , the electrodes  450  and  460  included in the pressure sensor  440  can be made of not only a transparent material but also an opaque material. 
     Hereafter, in the touch input device  1000  according to the embodiment of the present invention, the principle and structure for detecting the magnitude of touch pressure by using the pressure sensor  440  will be described in detail. In  FIGS. 5 a  to 5 e   , for convenience of description, the electrodes  450  and  460  included in the pressure sensor  440  are referred to as a pressure sensor. 
       FIGS. 5 a  and 5 b    show a relative distance between the reference potential layer and the pressure sensor of the first example, which are included in the touch input device, and show a pressure is applied to the touch input device. In the touch input device  1000  according to the embodiment of the present invention, the pressure sensors  450  and  460  may be attached on the cover  240  capable of constituting the backlight unit  200 B. In the touch input device  1000 , the pressure sensors  450  and  460  and the reference potential layer  600  may be spaced apart from each other by a distance “d”. 
     In  FIG. 5 a   , the reference potential layer  600  and the pressure sensor  450  and  460  may be spaced apart from each other with a spacer layer (not shown) placed therebetween. Here, as described with reference to  FIGS. 4 a  and 4 b   , the spacer layer may be the first air gap  210 ′, the second air gap  230 , and/or an additional air gap which are included in the manufacture of the display module  200  and/or the backlight unit  200 B. When the display module  200  and/or the backlight unit  200 B includes one air gap, the one air gap is able to perform the function of the spacer layer. When the display module  200  and/or the backlight unit  200 B includes a plurality of air gaps, the plurality of air gaps are able to collectively perform the function of the spacer layer. 
     In the touch input device  1000  according to the embodiment, the spacer layer may be located between the reference potential layer  600  and the pressure sensors  450  and  460 . As a result, when a pressure is applied to the cover layer  500 , the reference potential layer  600  is bent, so that a relative distance between the reference potential layer  600  and the pressure sensors  450  and  460  may be reduced. The spacer layer may be implemented by the air gap. According to the embodiment, the spacer layer  420  may be made of an impact absorbing material. Here, the impact absorbing material may include sponge and a graphite layer. The spacer layer  420  may be filled with a dielectric material in accordance with the embodiment. The spacer layer  420  may be formed through a combination of the air gap, the impact absorbing material, and the dielectric material. 
     In the touch input device  1000  according to the embodiment, the display module  200  may be bent or pressed by the touch applying the pressure. The display module may be bent or pressed in such a manner as to show the biggest transformation at the touch position. When the display module is bent or pressed according to the embodiment, a position showing the biggest transformation may not match the touch position. However, the display module may be shown to be bent or pressed at least at the touch position. For example, when the touch position approaches close to the border, edge, etc., of the display module, the most bent or pressed position of the display module may not match the touch position. The border or edge of the display module may not be shown to be bent very little depending on the touch. 
     Here, since the display module  200  in the touch input device  1000  according to the embodiment of the present invention may be bent or pressed by the application of the pressure, the components (a double-side adhesive tape, an adhesive tape  430 , the supports  251  and  252 , etc.) which are disposed at the border in order to maintain the air gaps  210  and  310  and/or the spacer layer  420  may be made of an inelastic material. That is, even though the components which are disposed at the border in order to maintain the air gaps  210  and  310  and/or the spacer layer  420  are not compressed or pressed, the touch pressure can be detected by the bending, etc., of the display module  200 . 
     When the cover layer  500 , the display panel  200 A, and/or the back light unit  200 B are bent or pressed at the time of touching the touch input device  1000  according to the embodiment, the cover  240  positioned below the spacer layer, as shown in  FIG. 4 b   , may be less bent or pressed due to the spacer layer. While  FIG. 5 b    shows that the cover  240  is not bent or pressed at all, this is just an example. The lowest portion of the cover  240  to which the pressure sensors  450  and  460  have been attached may be bent or pressed. However, the degree to which the lowest portion of the cover  240  is bent or pressed can be reduced by the spacer layer. 
     According to the embodiment, the spacer layer may be implemented in the form of the air gap. The spacer layer may be made of an impact absorbing material in accordance with the embodiment. The spacer layer may be filled with a dielectric material in accordance with the embodiment. 
       FIG. 5 b    shows that a pressure is applied to the structure of  FIG. 5 a   . For example, when the external pressure is applied to the cover layer  500  shown in  FIG. 4 a   , it can be seen that a relative distance between the reference potential layer  600  and the pressure sensors  450  and  460  is reduced from “d” to “d′”. Accordingly, in the touch input device  1000  according to the embodiment, when the external pressure is applied, the reference potential layer  600  is configured to be more bent than the cover  240  to which the pressure sensors  450  and  460  have been attached, so that it is possible to detect the magnitude of touch pressure. 
       FIGS. 4 a , 5 a , and 5 b    show that a first electrode  450  and a second electrode  460  are included as the pressure sensors  450  and  460  for detecting the pressure. Here, the mutual capacitance may be generated between the first electrode  450  and the second electrode  460 . Here, any one of the first and the second electrodes  450  and  460  may be a drive electrode and the other may be a receiving electrode. A driving signal is applied to the drive electrode, and a sensing signal may be obtained through the receiving electrode. When voltage is applied, the mutual capacitance may be generated between the first electrode  450  and the second electrode  460 . 
     The reference potential layer  600  may have any potential which causes the change of the mutual capacitance generated between the first electrode  450  and the second electrode  460 . For instance, the reference potential layer  600  may be a ground layer having a ground potential. The reference potential layer  600  may be any ground layer which is included in the display module. According to the embodiment, the reference potential layer  600  may be a ground potential layer which is included in itself during the manufacture of the touch input device  1000 . For example, in the display panel  200 A shown in  FIGS. 2 a  to 2 c   , an electrode (not shown) for blocking noise may be included between the first polarizer layer  271  and the first substrate  261 . This electrode for blocking the noise may be composed of ITO and may function as the ground. Also, according to the embodiment, a plurality of the common electrodes included in the display panel  200 A constitutes the reference potential layer  600 . Here, the potential of the common electrode may be a reference potential. 
     When a pressure is applied to the cover layer  500  by means of an object, at least a portion of the display panel  200 A and/or the backlight unit  200 B is bent, so that a relative distance between the reference potential layer  600  and the first and second electrodes  450  and  460  may be reduced from “d” to “d′”. Here, the less the distance between the reference potential layer  600  and the first and second electrodes  450  and  460  is, the less the value of the mutual capacitance between the first electrode  450  and the second electrode  460  may be. This is because the distance between the reference potential layer  600  and the first and second electrodes  450  and  460  is reduced from “d” to “d′”, so that a fringing capacitance of the mutual capacitance is absorbed in the reference potential layer  600  as well as in the object. When a nonconductive object touches, the change of the mutual capacitance is simply caused by only the change of the distance “d-d′” between the reference potential layer  600  and the electrodes  450  and  460 . 
     The foregoing has described that the pressure sensor  440  includes the first electrode  450  and the second electrode  460  and the pressure is detected by the change of the mutual capacitance between the first electrode  450  and the second electrode  460 . The pressure sensor  440  may be configured to include only any one of the first electrode  450  and the second electrode  460  (for example, the first electrode  450 ). 
       FIGS. 5 c  and 5 d    show a relative distance between a reference potential layer and a pressure sensor of a second example which are included in the touch input device, and show that a pressure is applied to the touch input device. Here, it is possible to detect the magnitude of touch pressure by detecting the self-capacitance between the first electrode  450  and the reference potential layer  600 . Here, the change of the self-capacitance between the first electrode  450  and the reference potential layer  600  is detected by applying the driving signal to the first electrode  450  and by receiving the reception signal from the first electrode  450 , so that the magnitude of the touch pressure is detected. 
     For example, the magnitude of the touch pressure can be detected by the change of the capacitance between the first electrode  450  and the reference potential layer  600 , which is caused by the distance change between the reference potential layer  600  and the first electrode  450 . Since the distance “d” is reduced with the increase of the touch pressure, the capacitance between the reference potential layer  600  and the first electrode  450  may be increased with the increase of the touch pressure. 
       FIGS. 4 a  and 5 a  to 5 d    show that the first electrode  450  and/or the second electrode  460  are relatively thick and they are directly attached to the cover  240 . However, this is just only for convenience of description. In accordance with the embodiment, the first electrode  450  and/or the second electrode  460  is the integral sheet-type pressure sensor  440  may be attached to the cover  240  and may have a relatively small thickness. 
     Although the foregoing has described that the pressure sensor  440  is attached to the cover  240  by referencing the touch input device  1000  shown in  FIG. 4 a   , the pressure sensor  440  may be disposed between the display module  200  and the substrate  300  in the touch input device  1000  shown in  FIG. 4 c   . According to the embodiment, the pressure sensor  440  may be disposed under the display module  200 . In this case, the reference potential layer  600  may be any potential layer which is disposed on the substrate  300  or within the display module  200 . Also, according to the embodiment, the pressure sensor  440  may be attached to the substrate  300 . In this case, the reference potential layer  600  may be any potential layer which is disposed on or within the display module  200 . 
       FIG. 5 e    shows the arrangement of pressure sensors of a third example which is included in the touch input device. As shown in  FIG. 5 e   , the first electrode  450  may be disposed on the substrate  300 , and the second electrode  460  may be disposed under the display module  200 . In this case, a separate reference potential layer may not be required. When a pressure touch is performed on the touch input device  1000 , a distance between the display module  200  and the substrate  300  may be changed, and thus, the mutual capacitance between the first electrode  450  and the second electrode  460  may be increased. Through the capacitance change, the magnitude of the touch pressure can be detected. Here, the first electrode  450  and the second electrode  460  may be included in the first pressure sensor  440 - 1  and the second pressure sensor  440 - 2  respectively and attached to the touch input device  1000 . 
     The foregoing has described that the reference potential layer  600  is located apart from the components to which the pressure sensor  440  is attached in the touch input device  1000 . It will be described in  FIGS. 6 a  to 6 c    that the component itself to which the pressure sensor  440  is attached in the touch input device  1000  functions as the reference potential layer. 
       FIG. 6 a    is a cross sectional view showing a portion of the touch input device to which the pressure sensor  440  has been attached according to a first method.  FIG. 6 a    shows that the pressure sensor  440  has been attached on the substrate  300 , the display module  200 , or the cover  240 . 
     As shown in  FIG. 6 b   , the adhesive tape  430  having a predetermined thickness may be formed along the border of the pressure sensor  440  so as to maintain the spacer layer  420 . Though  FIG. 6 b    shows that the adhesive tape  430  is formed along the entire border (for example, four sides of a quadrangle) of the pressure sensor  440 , the adhesive tape  430  may be formed only on at least a portion (for example, three sides of a quadrangle) of the border of the pressure sensor  440 . Here, as shown in  FIG. 6 b   , the adhesive tape  430  may not be formed on an area including the electrodes  450  and  460 . As a result, when the pressure sensor  440  is attached to the substrate  300  or the display module  200  through the adhesive tape  430 , the pressure electrodes  450  and  460  may be spaced apart from the substrate  300  or the display module  200  at a predetermined distance. According to the embodiment, the adhesive tape  430  may be formed on the top surface of the substrate  300 , the bottom surface of the display module  200 , the surface of the cover  240 . Also, the adhesive tape  430  may be a double adhesive tape.  FIG. 6 b    shows only one of the pressure electrodes  450  and  460 . 
       FIG. 6 c    is a partial cross sectional view of the touch input device to which the pressure sensor has been attached according to a second method. In  FIG. 6 c   , after the pressure sensor  440  is placed on the substrate  300 , the display module  200 , or the cover  240 , the pressure sensor  440  may be fixed to the substrate  300 , the display module  200 , or the cover  240  by means of the adhesive tape  430 . For this, the adhesive tape  430  may come in contact with at least a portion of the pressure sensor  440  and at least a portion of the substrate  300 , the display module  200 , or the cover  240 .  FIG. 6 c    shows that the adhesive tape  430  continues from the top of the pressure sensor  440  to the exposed surface of the substrate  300 , the display module  200 , or the cover  240 . Here, only a portion of the adhesive tape  430 , which contacts with the pressure sensor  440 , may have adhesive strength. Therefore, in  FIG. 6 c   , the top surface of the adhesive tape  430  may not have the adhesive strength. 
     As shown in  FIG. 6 c   , even if the pressure sensor  440  is fixed to the substrate  300 , the display module  200 , or the cover  240  by using the adhesive tape  430 , a predetermined space, i.e., air gap may be created between the pressure sensor  440  and the substrate  300 , the display module  200 , or the cover  240 . This is because the substrate  300 , the display module  200 , or the cover  240  is not directly attached to the pressure sensor  440  by means of the adhesive and because the pressure sensor  440  includes the pressure electrodes  450  and  460  having a pattern, so that the surface of the pressure sensor  440  may not be flat. The air gap of  FIG. 6 c    may also function as the spacer layer  420  for detecting the touch pressure. 
       FIGS. 7 a  to 7 e    show pressure electrode patterns included in the pressure sensor for pressure detection according to the embodiment of the present invention.  FIGS. 7 a  to 7 c    show the patterns of the first electrode  450  and the second electrode  460  included in the pressure sensor  440 . The pressure sensor  440  including the pressure electrode patterns shown in  FIGS. 7 a  to 7 c    may be formed on the cover  240 , the substrate  300  or on the bottom surface of the display module  200 . The capacitance between the first electrode  450  and the second electrode  460  may be changed depending on a distance between the reference potential layer  600  and the electrode layer including both the first electrode  450  and the second electrode  460 . 
     When the magnitude of the touch pressure is detected as the mutual capacitance between the first electrode  450  and the second electrode  460  is changed, it is necessary to form the patterns of the first electrode  450  and the second electrode  460  so as to generate the range of the capacitance required to improve the detection accuracy. With the increase of a facing area or facing length of the first electrode  450  and the second electrode  460 , the size of the capacitance that is generated may become larger. Therefore, the pattern can be designed by adjusting the size of the facing area, facing length and facing shape of the first electrode  450  and the second electrode  460  in accordance with the range of the necessary capacitance.  FIGS. 7 b  to 7 c    show that the first electrode  450  and the second electrode  460  are formed in the same layer, and show that the pressure electrode is formed such that the facing length of the first electrode  450  and the second electrode  460  becomes relatively longer. The patterns of the pressure electrodes  450  and  460  shown in  FIGS. 7 b  to 7 c    can be used to detect the pressure in the principle described in FIGS.  5   a  and  5   c.    
     The electrode pattern shown in  FIG. 7 d    can be used to detect the pressure in the principle described in  FIGS. 5 c  and 5 d   . Here, the pressure electrode should not necessary have a comb teeth shape or a trident shape, which is required to improve the detection accuracy of the mutual capacitance change amount. The pressure electrode may have, as shown in  FIG. 7 d   , a plate shape (e.g., quadrangular plate). 
     The electrode pattern shown in  FIG. 7 e    can be used to detect the pressure in the principle described in  FIG. 5 e   . Here, as shown in  FIG. 7 e   , the first electrode  450  and the second electrode  460  are disposed orthogonal to each other, so that the capacitance change amount detection sensitivity can be enhanced. 
       FIGS. 8 a  and 8 b    show a relation between a magnitude of a touch pressure and a saturated area in the touch input device to which the pressure sensor  440  has been applied according to the embodiment of the present invention. Although  FIGS. 8 a  and 8 b    show that the pressure sensor  440  is attached to the substrate  300 , the following description can be applied in the same manner to a case where the pressure sensor  440  is attached to the display module  200  or the cover  240 . 
     The touch pressure with a sufficient magnitude makes a state where the distance between the pressure sensor  440  and the substrate  300  cannot be reduced any more at a predetermined position. Hereafter, the state is designated as a saturation state. For instance, as shown in  FIG. 8 a   , when the touch input device  1000  is pressed by a force “f”, the pressure sensor  440  contacts the substrate  300 , and thus, the distance between the pressure sensor  440  and the substrate  300  cannot be reduced any more. Here, as shown on the right of  FIG. 8 a   , the contact area between the pressure sensor  440  and the substrate  300  may be indicated by “a”. 
     However, in this case, when the magnitude of the touch pressure becomes larger, the contact area between the pressure sensor  440  and the substrate  300  in the saturation state where the distance between the pressure sensor  440  and the substrate  300  cannot be reduced any more may become greater. For example, as shown in  FIG. 8 b   , when the touch input device  1000  is pressed by a force “F” greater than the force “f”, the contact area between the pressure sensor  440  and the substrate  300  may become greater. As shown on the right of  FIG. 8 a   , the contact area between the pressure sensor  440  and the substrate  300  may be indicated by “A”. As such, the greater the contact area, the more the mutual capacitance between the first electrode  450  and the second electrode  460  may be reduced. Hereafter, it will be described that the magnitude of the touch pressure is calculated by the change of the capacitance according to the distance change. This may include that the magnitude of the touch pressure is calculated by the change of the saturation area in the saturation state. 
       FIGS. 8 a  and 8 b    are described with reference to the example shown in  FIG. 6 a   . It is apparent that the description with reference to  FIGS. 8 a  and 8 b    can be applied in the same manner to the examples described with reference to  FIGS. 4 a , 4 c , 5 a  to 5 e , and 6 c   . More specifically, the magnitude of the touch pressure can be calculated by the change of the saturation area in the saturation state where the distance between the pressure sensor  440  and either the ground layer or the reference potential layer  600  cannot be reduced any more. 
     The top surface of the substrate  300  may also have the ground potential in order to block the noise.  FIG. 9  shows the cross sections of the pressure sensor according to the embodiment of the present invention. Referring to (a) of  FIG. 9 , a cross section when the pressure sensor  440  including the pressure electrodes  450  and  460  is attached to the substrate  300  or the display module  200  is shown. Here, in the pressure sensor  440 , since the pressure electrodes  450  and  460  are disposed between the first insulation layer  470  and the second insulation layer  471 , a short-circuit can be prevented from occurring between the pressure electrodes  450  and  460  and either the substrate  300  or the display module  200 . Also, depending on the kind and/or implementation method of the touch input device  1000 , the substrate  300  or the display module  200  on which the pressure electrodes  450  and  460  are attached may not have the ground potential or may have a weak ground potential. In this case, the touch input device  1000  according to the embodiment of the present may further include a ground electrode (not shown) between the first insulation layer  470  and either the substrate  300  or the display module  200 . According to the embodiment, another insulation layer (not shown) may be included between the ground electrode and either the substrate  300  or the display module  200 . Here, the ground electrode (not shown) is able to prevent the size of the capacitance generated between the first electrode  450  and the second electrode  460 , which are pressure electrodes, from increasing excessively. 
     Cross sections of a portion of the pressure sensor attached to the touch input device in accordance with the embodiment of the present invention are shown in (a) to (d) of  FIG. 9 . 
     For example, when the first electrode  450  and the second electrode  460  included in the pressures sensor  440  are formed in the same layer, the pressure sensor  440  may be configured as shown in (a) of  FIG. 9 . Here, each of the first electrode  450  and the second electrode  460  shown in (a) of  FIG. 9  may be, as shown in  FIG. 13 a   , composed of a plurality of lozenge-shaped electrodes. Here, the plurality of the first electrodes  450  are connected to each other in a first axial direction, and the plurality of the second electrodes  460  are connected to each other in a second axial direction orthogonal to the first axial direction. The lozenge-shaped electrodes of at least one of the first and the second electrodes  450  and  460  are connected to each other through a bridge, so that the first electrode  450  and the second electrode  460  may be insulated from each other. Also, the first electrode  450  and the second electrode  460  shown in (a) of  FIG. 9  may be composed of an electrode having a form shown in  FIG. 13   b.    
     In the pressure sensor  440 , it can be considered that the first electrode  450  and the second electrode  460  are formed in different layers in accordance with the embodiment and form the electrode layer. A cross section when the first electrode  450  and the second electrode  460  are formed in different layers is shown in (b) of  FIG. 9 . As shown in (b) of  FIG. 9 , the first electrode  450  may be formed on the first insulation layer  470 , and the second electrode  460  may be formed on the second insulation layer  471  positioned on the first electrode  450 . According to the embodiment, the second electrode  460  may be covered with a third insulation layer  472 . In other words, the pressure sensor  440  may include the first to the third insulation layers  470  to  472 , the first electrode  450 , and the second electrode  460 . Here, since the first electrode  450  and the second electrode  460  are disposed in different layers, they can be implemented so as to overlap each other. For example, the first electrode  450  and the second electrode  460  may be, as shown in  FIG. 13 c   , formed similarly to the pattern of the drive electrode TX and receiving electrode RX which are arranged in the form of M×N array. Here, M and N may be natural numbers greater than 1. Also, as shown in  FIG. 13 a   , the lozenge-shaped first and the second electrodes  450  and  460  may be disposed in different layers respectively. 
     A cross section when the pressure sensor  440  is formed to include only the first electrode  450  is shown in (c) of  FIG. 9 . As shown in (c) of  FIG. 9 , the pressure sensor  440  including the first electrode  450  may be disposed on the substrate  300  or on the display module  200 . For example, the first electrode  450  may be disposed as shown in  FIG. 12   d.    
     A cross section when the first pressure sensor  440 - 1  including the first electrode  450  is attached to the substrate  300  and the second pressure sensor  440 - 2  including the second electrode  460  is attached to the display module  200  is shown in (d) of  FIG. 9 . As shown in (d) of  FIG. 9 , the first pressure sensor  440 - 1  including the first electrode  450  may be disposed on the substrate  300 . Also, the second pressure sensor  440 - 2  including the second electrode  460  may be disposed on the bottom surface of the display module  200 . 
     As with the description related to (a) of  FIG. 9 , when substrate  300 , the display module  200 , or the cover  240  on which the pressure sensors  450  and  460  are attached may not have the ground potential or may have a weak ground potential, the pressure sensor  440  may further include, as shown in (a) to (d) of  FIG. 9 , a ground electrode (not shown) under the first insulation layers  470 ,  470 - 1 , and  470 - 2  disposed to contact the substrate  300 , the display module  200 , or the cover  240 . Here, the pressure sensor  440  may further include an additional insulation layer (not shown) which is opposite to the first insulation layers  470 ,  470 - 1 , and  470 - 2  such that the ground electrode (not shown) is located between the additional insulation layer and the first insulation layers  470 ,  470 - 1 , and  470 - 2 . 
     The foregoing has described the case where the touch pressure is applied to the top surface of the touch input device  1000 . However, even when the touch pressure is applied to the bottom surface of the touch input device  1000 , the pressure sensor  440  is able to detect the touch pressure in the same manner. 
     As shown in  FIGS. 4 to 9 , in the case where the pressure sensor  440  according to the embodiment of the present invention is attached to the touch input device, when a pressure is applied to the touch input device by the object  500 , the display module  200  or the substrate  300  is bent or pressed, so that the magnitude of the touch pressure can be calculated. Here, for the purpose of describing the change of the distance between the reference potential layer  600  and the pressure sensor  440 ,  FIGS. 4 to 9  show that the display module  200 , the substrate  300 , or only a portion of the display module  200  to which the pressure is directly applied by the object  500  is bent or pressed. However, the member to which the pressure is not directly applied by the object  500  is also actually bent or pressed. However, since how much the member to which the pressure is directly applied is bent or pressed is more than how much the member to which the pressure is not directly applied is bent or pressed, the descriptions of  FIGS. 4 to 9  are possible. As such, when the pressure is applied to the touch input device, the pressure sensor  440  attached to the touch input device may be also bent or pressed. Here, when the pressure applied to the touch input device is released, the display module  200  or the substrate  300  is restored to its original state, and thus, the pressure sensor  440  attached to the touch input device should also maintain its original shape. Also, when the original shape of the pressure sensor  440  is difficult to maintain, there may be difficulties in the process of attaching the pressure sensor  440  to the touch input device. Therefore, it is recommended that the pressure sensor  440  should have a rigidity to maintain its original shape. 
     When the pressure electrodes  450  and  460  included in the pressure sensor  440  are made of soft conductive metal such as Al, Ag, and Cu, the pressure electrodes  450  and  460  have a low rigidity and a thickness of only several micrometers. Therefore, the original shape of the pressure sensor  440  is difficult to maintain only by the pressure electrodes  450  and  460 . Accordingly, it is recommended that the first insulation layer  470  or the second insulation layer  471  which is disposed on or under the pressure electrodes  450  and  460  has a rigidity enough to maintain the original shape of the pressure sensor  440 . 
     Specifically, as shown in  FIG. 3 b   , the pressure sensor  440  may include the electrode layer and support layers  470   b  and  471   b . Here, the electrode layer may be composed of the pressure electrodes  450  and  460  including the first electrode  450  and the second electrode  460 . In this case, the pressure sensor  440  may be used to detect the change of the capacitance between the first electrode  450  and the second electrode  460 , which is changed according to a relative distance change between the electrode layer and the reference potential layer  600  which is disposed apart from the pressure sensor  440 . Also, the electrode layer may be composed of the pressure electrodes  450  and  460  including only one electrode. In this case, the pressure sensor  440  may be used to detect the capacitance change between the electrode layer and the reference potential layer  600 , which is changed according to the relative distance change between the electrode layer and the reference potential layer  600  which is disposed apart from the pressure sensor  440 . 
     Here, when the reference potential layer  600  which is disposed apart from the pressure sensor  440  does not have a uniform reference potential according to each input position, or when the distance change between the reference potential layer and the electrode layer is not uniform for the pressure having the same magnitude in accordance with the input position, for example, when the surface of the reference potential layer  600  which is disposed apart from the pressure sensor  440  is not uniform, it may be difficult to use the capacitance change amount between the electrode layer and the reference potential layer  600  which is disposed apart from the pressure sensor  440 . As shown in  FIG. 3 h   , the pressure sensor  440  according to the embodiment of the present invention may include a first electrode layer including the first electrode  450  and include a second electrode layer which includes the second electrode  460  and is disposed apart from the first electrode layer. In this case, the pressure sensor  440  may be used to detect the capacitance change between the first electrode layer and the second electrode layer, which is changed according to a relative distance change between the first electrode layer and the second electrode layer. Here, any one of the first electrode layer and the second electrode layer may be the reference potential layer. As such, the capacitance change between the electrode layers is detected, which is changed according to the distance change between the electrode layers located within the pressure sensor  440 , so that it is possible to detect a uniform capacitance change even when, as described above, the uniform capacitance change cannot be detected from the reference potential layer located outside the pressure sensor  440 . Here, an elastic layer  480  which has a restoring force and absorbs the impact may be further included between the first electrode layer and the second electrode layer in order to provide uniformity of the distance change between the first electrode layer and the second electrode layer. Also, as shown in (d) of  FIG. 9 , the pressure sensor  440  may include the first pressure sensor including the first electrode layer and a first support layer and the second pressure sensor including the second electrode layer and a second support layer. In this case, the pressure sensor  440  may be used to detect the capacitance change between the first electrode layer and the second electrode layer, which is changed according to the relative distance change between the first electrode layer and the second electrode layer. 
     The support layers  470   b  and  471   b  may be made of a material, for example, a resin material, highly rigid metal, paper, or the like, which has a rigidity capable of maintaining the shape of the pressure sensor  440  even when the distance change occurs between the pressure sensor  440  and the reference potential layer  600 . 
     The pressure sensor  440  may further include the first insulation layer  470  and the second insulation layer  471 . Here, the electrode layer may be located between the first insulation layer  470  and the second insulation layer  471 , and the support layers  470   b  and  471   b  may be included in at least any one of the first insulation layer  470  and the second insulation layer  472 . 
     The first insulation layer  470  or the second insulation layer  471  may further include electrode covering layers  470   a  and  471   a . The electrode covering layers  470   a  and  471   a  may function to insulate the electrode layer and may function to protect the electrode layer, for example, to prevent the electrode from being oxidized, scraped, cracked, or the like. Also, the electrode covering layers  470   a  and  471   a  are formed of or coated with a material with a color, thereby preventing the pressure sensor  440  from being degraded due to exposure to the sun during the distribution of the pressure sensor  440 . Here, the electrode covering layers  470   a  and  471   a  may be adhered to the electrode layer or to the support layers  470   b  and  471   b  by means of an adhesive or may be printed or coated on the support layers  470   b  and  471   b . The electrode covering layers  470   a  and  471   a  may be also made of a highly rigid resin material. However, since the thickness of the electrode covering layer is only several micrometers, it is difficult to maintain the original shape of the pressure sensor  440  of about 100 μm. 
     Also, as shown in  FIGS. 3 e  and 3 f   , the pressure sensor  440  according to the embodiment of the present invention may further include the adhesive layer  430  and a protective layer  435  outside either the first insulation layer  470  or the second insulation layer  471 . Though it has been described in  FIGS. 4 to 9  that the adhesive layer  430  is formed separately from the pressure sensor  440 , the adhesive layer  430  may be manufactured as one component included in the pressure sensor  440 . The protective layer  435  functions to protect the adhesive layer  430  before the pressure sensor  440  is attached to the touch input device. When the pressure sensor  440  is attached to the touch input device, the protective layer  435  is removed and the pressure sensor  440  can be attached to the touch input device by using the adhesive layer  430 . 
     As shown in  FIG. 3 c   , the electrode covering layers  470   a  and  471   a  may not be formed on the side where the support layers  470   b  and  471   b  are formed. The support layers  470   b  and  471   b  made of a resin material, paper, or the like are able to insulate and protect the electrode layer. In this case, likewise, the support layers  470   b  and  471   b  may be formed of or coated with a material with a color. 
     As shown in  FIG. 3 d   , any one of the first insulation layer  470  and the second insulation layer  471  may have a thickness less than that of the other. Specifically, since the capacitance (C) is inversely proportional to the distance “d” between the electrode layer and the reference potential layer  600 ,  FIG. 3 i    shows that, for the same distance change, the smaller the distance between the electrode layer and the reference potential layer  600  is, the greater the capacitance change amount becomes, and then it becomes easier to precisely detect the pressure. Therefore, the pressure sensor  440  is attached to the touch input device including the cover  240 , the substrate  300  and/or the display module  200 , and the thickness of one of the first and second insulation layers  470  and  471 , which is closer to the reference potential layer  600  than the other, may be less than that of the other. 
     Preferably, only one of the first and second insulation layers  470  and  471  may include the support layers  470   b  and  471   b . Specifically, in the state where the pressure sensor  440  is attached to the touch input device, only one of the first and second insulation layers  470  and  471 , which is farther from the reference potential layer  600  than the other, may include the support layers  470   b  and  471   b.    
     Likewise, as shown in (d) of  FIG. 9 , when the first pressure sensor  440 - 1  is attached to the substrate  300  and the second pressure sensor  440 - 2  is attached to the display module  200 , the thickness of the second insulation layer  471 - 1  which is closer to the first electrode  450  out of the first and the second insulation layers  470 - 1  and  471 - 1  may be less than the thickness of the first insulation layer  470 - 1 , the thickness of the fourth insulation layer  471 - 2  which is closer to the second electrode  460  out of the third and the fourth insulation layers  470 - 2  and  471 - 2  may be less than the thickness of the third insulation layer  470 - 2 . Preferably, only the first and the third insulation layers  470 - 1  and  470 - 2  may include the support layer  470   b.    
     As shown in  FIG. 3 h   , even when the pressure sensor  440  includes the first electrode layer including the first electrode  450  and the second electrode layer which includes the second electrode  460  and is disposed apart from the first electrode layer, the thickness of any one of the first insulation layer  470  and the second insulation layer  471  may be less than that of the other. Specifically, in a case where the pressure sensor  440  is attached to the display module  200  or the substrate  300 , when a pressure is applied to the touch input device, a distance between the pressure sensor  440  and the member to which the pressure sensor  440  has been attached is not changed. However, a distance between the pressure sensor  440  and the member to which the pressure sensor  440  has been not attached is changed. Here, the capacitance change according to the distance change between the pressure sensor  440  and the reference potential layer  600  located outside the pressure sensor  440  is not desired. Thus, it is preferable to minimize such a capacitance change. Therefore, the pressure sensor  440  is attached to the touch input device including the substrate  300  and the display module  200  in such a manner as to be attached to any one of a side of the substrate  300 , which is opposite to the display module  200  and a side of the display module  200 , which is opposite to the substrate  300 . In a state where the pressure sensor  440  is attached to the touch input device, the thickness of one of the first and second insulation layers  470  and  471 , which is closer to the side to which the pressure sensor  440  has been attached than the other, may be less than that of the other. 
     Preferably, only one of the first and second insulation layers  470  and  471  may include the support layers  470   b  and  471   b . Specifically, in the state where the pressure sensor  440  is attached to the touch input device, only one of the first and second insulation layers  470  and  471 , which is farther from the side to which the pressure sensor  440  has been attached than the other, may include the support layers  470   b  and  471   b.    
     The pressure sensor  440  shown in  FIG. 3 e    is attached to the cover  240 , the substrate  300  or the display module  200  toward the side on which the adhesive layer  430  is formed. The pressure sensor  440  shown in  FIG. 3 e    is used to detect the magnitude of the pressure according to the distance change between the electrode layer and the reference potential layer  600  formed in or on the member to which the pressure sensor  440  has not been attached. The pressure sensor  440  shown in  FIG. 3 f    is attached to the cover  240 , the substrate  300  or the display module  200  toward the side on which the adhesive layer  430  is formed. The pressure sensor  440  shown in  FIG. 3 f    is used to detect the magnitude of the pressure according to the distance change between the electrode layer and the reference potential layer  600  formed in or on the member to which the pressure sensor  440  has been attached. 
     A space in which the pressure sensor  440  is disposed, for example, an interval between the display module  200  and the substrate  300  depends on the touch input device and is about 100 to 500 μm. The thicknesses of the pressure sensor  440  and the support layers  470   b  and  471   b  are limited according to the interval. As shown in  FIG. 3 g   , when the pressure sensor is attached to the display module  200  and a distance between the display module  200  and the substrate  300  is 500 μm, it is desirable that the pressure sensor  440  has a thickness of 50 μm to 450 μm. If the thickness of the pressure sensor  440  is less than 50 μm, the thickness of the support layers  470   b  and  471   b  having a relatively high rigidity also becomes smaller, so that the original shape of the pressure sensor  440  is difficult to maintain. If the thickness of the pressure sensor  440  is larger than 450 μm, an interval between the pressure sensor  440  and the substrate  300 , i.e., the reference potential layer, is significantly reduced below 50 μm, so that it is difficult to measure the pressure with a wide range. 
     The pressure sensor  440  is disposed in the touch input device. Therefore, as with the touch input device, the pressure sensor  440  is required to meet a given reliability under a predetermined condition, for example, temperature, humidity, etc. In order to meet the reliability that the appearance and characteristics are less changed under a harsh condition of 85 to −40° C., a humidity condition of 85%, etc., it is desirable that the support layers  470   b  and  471   b  are made of a resin material. Specifically, the support layers  470   b  and  471   b  may be formed of polyimide (PI) or polyethylene terephthalate (PET). Also, polyethylene terephthalate costs less than polyimide. The material constituting the support layers  470   b  and  471   b  may be determined in terms of cost and reliability. 
     As described above, in order to detect the pressure through the touch input device  1000  to which the pressure sensor  440  is applied according to the embodiment of the present invention, it is necessary to sense the capacitance change occurring in the pressure electrodes  450  and  460 . Therefore, it is necessary for the driving signal to be applied to the drive electrode out of the first and second electrodes  450  and  460 , and it is required to detect the touch pressure by the capacitance change amount by obtaining the sensing signal from the receiving electrode. According to the embodiment, it is possible to additionally include a pressure detection device in the form of a pressure sensing IC for the operation of the pressure detection. The pressure detection module (not shown) according to the embodiment of the present invention may include not only the pressure sensor  440  for pressure detection but also the pressure detection device. 
     In this case, the touch input device repeatedly has a configuration similar to the configuration of  FIG. 1  including the drive unit  120 , the sensing unit  110 , and the controller  130 , so that the area and volume of the touch input device  1000  increase. 
     According to the embodiment, the touch detection device  1000  may apply the driving signal for pressure detection to the pressure sensor  440  by using the touch detection device for the operation of the touch sensor panel  100 , and may detect the touch pressure by receiving the sensing signal from the pressure sensor  440 . Hereafter, the following description will be provided by assuming that the first electrode  450  is the drive electrode and the second electrode  460  is the receiving electrode. 
     For this, in the touch input device  1000  to which the pressure sensor  440  is applied according to the embodiment of the present invention, the driving signal may be applied to the first electrode  450  from the drive unit  120 , and the second electrode  460  may transmit the sensing signal to the sensing unit  110 . The controller  130  may perform the scanning of the touch sensor panel  100 , and simultaneously perform the scanning of the touch pressure detection, or the controller  130  performs the time-sharing, and then may generate a control signal such that the scanning of the touch sensor panel  100  is performed in a first time interval and the scanning of the pressure detection is performed in a second time interval different from the first time interval. 
     Therefore, in the embodiment of the present invention, the first electrode  450  and the second electrode  460  should be electrically connected to the drive unit  120  and/or the sensing unit  110 . Here, it is common that the touch detection device for the touch sensor panel  100  corresponds to the touch sensing IC  150  and is formed on one end of the touch sensor panel  100  or on the same plane with the touch sensor panel  100 . The pressure electrode  450  and  460  included in the pressure sensor  440  may be electrically connected to the touch detection device of the touch sensor panel  100  by any method. For example, the pressure electrode  450  and  460  may be connected to the touch detection device through a connector by using the second PCB  210  included in the display module  200 . For example, conductive traces  461  which electrically extend from the first electrode  450  and the second electrode  460  respectively may be electrically connected to the touch sensing IC  150  through the second PCB  210 , etc. 
       FIGS. 10 a  to 10 b    show that the pressure sensor  440  including the pressure electrodes  450  and  460  is attached to the bottom surface of the display module  200 .  FIGS. 10 a  and 10 b    show the second PCB  210  on which a circuit for the operation of the display panel has been mounted is disposed on a portion of the bottom surface of the display module  200 . 
       FIG. 10 a    shows that the pressure sensor  440  is attached to the bottom surface of the display module  200  such that the first electrode  450  and the second electrode  460  are connected to one end of the second PCB  210  of the display module  200 . Here, the first electrode  450  and the second electrode  460  may be connected to the one end of the second PCB  210  by using a double conductive tape. Specifically, since the thickness of the pressure sensor  440  and an interval between the substrate  300  and the display module  200  where the pressure sensor  440  is disposed are very small, the thickness can be effectively reduced by connecting both the first electrode  450  and the second electrode  460  to the one end of the second PCB  210  by using the double conductive tape rather than by using a separate connector. A conductive pattern may be printed on the second PCB  210  in such a manner as to electrically connect the pressure electrodes  450  and  460  to a necessary component like the touch sensing IC  150 , etc. The detailed description of this will be provided with reference to  FIGS. 11 a  to 11 c   . An attachment method of the pressure sensor  440  including the pressure electrodes  450  and  460  shown in  FIG. 10 a    can be applied in the same manner to the substrate  300  and the cover  240 . 
       FIG. 10 b    shows that the pressure sensor  440  including the first electrode  450  and the second electrode  460  is not separately manufactured but is integrally formed on the second PCB  210  of the display module  200 . For example, when the second PCB  210  of the display module  200  is manufactured, a certain area (not shown) is separated from the second PCB, and then not only the circuit for the operation of the display panel but also the pattern corresponding to the first electrode  450  and the second electrode  460  can be printed on the area. A conductive pattern may be printed on the second PCB  210  in such a manner as to electrically connect the first electrode  450  and the second electrode  460  to a necessary component like the touch sensing IC  150 , etc. 
       FIGS. 11 a  to 11 c    show a method for connecting the pressure electrodes  450  and  460  included in the pressure sensor  440  to the touch sensing IC  150 . In  FIGS. 11 a  to 11 c   , the touch sensor panel  100  is included outside the display module  200 .  FIGS. 12 a  to 12 c    show that the touch detection device of the touch sensor panel  100  is integrated in the touch sensing IC  150  mounted on the first PCB  160  for the touch sensor panel  100 . 
       FIG. 11 a    shows that the pressure electrodes  450  and  460  included in the pressure sensor  440  attached to the display module  200  are connected to the touch sensing IC  150  through a first connector  121 . As shown in  FIG. 11 a   , in a mobile communication device such as a smart phone, the touch sensing IC  150  is connected to the second PCB  210  for the display module  200  through the first connector  121 . The second PCB  210  may be electrically connected to the main board through a second connector  224 . Therefore, through the first connector  121  and the second connector  224 , the touch sensing IC  150  may transmit and receive a signal to and from the CPU or AP for the operation of the touch input device  1000 . 
     Here, while  FIG. 11 a    shows that the pressure sensor  440  is attached to the display module  200  by the method shown in  FIG. 10 b   , the first electrode  450  can be attached to the display module  200  by the method shown in  FIG. 10 a   . A conductive pattern may be printed on the second PCB  210  in such a manner as to electrically connect the first electrode  450  and the second electrode  460  to the touch sensing IC  150  through the first connector  121 . 
       FIG. 11 b    shows that the pressure electrodes  450  and  460  included in the pressure sensor  440  attached to the display module  200  are connected to the touch sensing IC  150  through a third connector  473 . In  FIG. 11 b   , the pressure electrodes  450  and  460  may be connected to the main board for the operation of the touch input device  1000  through the third connector  473 , and in the future, may be connected to the touch sensing IC  150  through the second connector  224  and the first connector  121 . Here, the pressure electrodes  450  and  460  may be printed on the additional PCB separated from the second PCB  210 . Otherwise, according to the embodiment, the pressure electrodes  450  and  460  may be attached to the touch input device  1000  in the form of the pressure sensor  440  shown in  FIGS. 3 a  to 3 h    and may be connected to the main board through the third connector  473  by extending the conductive trace, etc., from the pressure electrodes  450  and  460 . 
       FIG. 11 c    shows that the pressure electrodes  450  and  460  are directly connected to the touch sensing IC  150  through a fourth connector  474 . In  FIG. 11 c   , the pressure electrodes  450  and  460  may be connected to the first PCB  160  through the fourth connector  474 . A conductive pattern may be printed on the first PCB  160  in such a manner as to electrically connect the fourth connector  474  to the touch sensing IC  150 . As a result, the pressure electrodes  450  and  460  may be connected to the touch sensing IC  150  through the fourth connector  474 . Here, the pressure electrodes  450  and  460  may be printed on the additional PCB separated from the second PCB  210 . The second PCB  210  may be insulated from the additional PCB so as not to be short-circuited with each other. Also, according to the embodiment, the pressure electrodes  450  and  460  may be attached to the touch input device  1000  in the form of the pressure sensor  440  shown in  FIGS. 3 a  to 3 h    and may be connected to the first PCB  160  through the fourth connector  474  by extending the conductive trace, etc., from the pressure electrodes  450  and  460 . 
     The connection method of  FIGS. 11 b  and 11 c    can be applied to the case where the pressure sensor  440  including the pressure electrode  450  and  460  is formed on the substrate  300  or on the cover  240  as well as on the bottom surface of the display module  200 . 
       FIGS. 11 a  to 11 c    have been described by assuming that a chip on board (COB) structure in which the touch sensing IC  150  is formed on the first PCB  160 . However, this is just an example. The present invention can be applied to the chip on board (COB) structure in which the touch sensing IC  150  is mounted on the main board within the mounting space  310  of the touch input device  1000 . It will be apparent to those skilled in the art from the descriptions of  FIGS. 11 a  to 11 c    that the connection of the pressure electrodes  450  and  460  through the connector can be also applied to another embodiment. 
     The foregoing has described the pressure electrodes  450  and  460 , that is to say, has described that the first electrode  450  constitutes one channel as the drive electrode and the second electrode  460  constitutes one channel as the receiving electrode. However, this is just an example. According to the embodiment, the drive electrode and the receiving electrode constitute a plurality of channels respectively. Here, a high-pressure detection accuracy of the touch can be obtained by the plurality of channels constituted by the drive electrode and the receiving electrode, and it is possible to detect multi pressure of a multi touch. 
       FIGS. 12 a  to 12 d    show that the pressure electrode of the present invention constitutes the plurality of channels.  FIG. 12 a    shows that first electrodes  450 - 1  and  450 - 2  and second electrodes  460 - 1  and  460 - 2  constitute two channels respectively.  FIG. 12 a    shows that all of the first electrodes  450 - 1  and  450 - 2  and the second electrodes  460 - 1  and  460 - 2  which constitute the two channels are included in one pressure sensor  440 .  FIG. 12 b    shows that the first electrode  450  constitutes two channels  450 - 1  and  450 - 2  and the second electrode  460  constitutes one channel.  FIG. 12 c    shows the first electrode  450 - 1  to  450 - 5  constitute five channels and the second electrode  460 - 1  and  460 - 5  constitute five channels. Even in this case, all of the electrodes constituting the five channels may be also included in one pressure sensor  440 .  FIG. 12 d    shows that first electrodes  451  to  459  constitute nine channels and all of the first electrodes  451  to  459  are included in one pressure sensor  440 . 
     As shown in  FIGS. 12 a  to 12 d  and 13 a  to 13 d   , when the plurality of channels are formed, a conductive pattern which is electrically connected to the touch sensing IC  150  from each of the first electrode  450  and/or the second electrode  460  may be formed. 
     Here, described is a case in which the plurality of channels shown in  FIG. 12 d    are constituted. In this case, since a plurality of conductive patterns  461  should be connected to the first connector  121  with a limited width, a width of the conductive pattern  461  and an interval between the adjacent conductive patterns  461  should be small. Polyimide is more suitable for a fine process of forming the conductive pattern  461  with such a small width and interval than polyethylene terephthalate. Specifically, the support layers  470   b  and  471   b  of the pressure sensor  440 , in which the conductive pattern  461  is formed, may be made of polyimide. Also, a soldering process may be required to connect the conductive pattern  461  to the first connector  121 . For a soldering process which is performed at a temperature higher than 300° C., polyimide resistant to heat is more suitable than polyethylene terephthalate relatively vulnerable to heat. Here, for the purpose of reducing production costs, a portion of the support layers  470   b  and  471   b , in which the conductive pattern  461  is not formed, may be made of polyethylene terephthalate, and a portion of the support layers  470   b  and  471   b , in which the conductive pattern  461  is formed, may be made of polyimide. 
       FIGS. 12 a  to 12 d  and 13 a  to 13 d    show that the pressure electrode constitutes a single or a plurality of channels. The pressure electrode may be comprised of a single or a plurality of channels by a variety of methods. While  FIGS. 12 a  to 12 d  and 13 a  to 13 d    do not show that the pressure electrodes  450  and  460  are electrically connected to the touch sensing IC  150 , the pressure electrodes  450  and  460  can be connected to the touch sensing IC  150  by the method shown in  FIGS. 11 a  to 11 c    and other methods. 
     In the foregoing description, the first connector  121  or the fourth connector  474  may be a double conductive tape. Specifically, since the first connector  121  or the fourth connector  474  may be disposed at a very small interval, the thickness can be effectively reduced by using the double conductive tape rather than a separate connector. Also, according to the embodiment, the functions of the first connector  121  and the fourth connector  474  can be implemented by a Flex-on-Flex Bonding (FOF) method capable of achieving a small thickness. 
     Hereinafter, various methods in which the pressure sensor  440  detects the magnitude of the pressure of the touch on the basis of the capacitance change amount detected from the channel. 
     Example of First Method 
       FIG. 20 a    is a flowchart for describing an example of a method for detecting the magnitude of the touch pressure by using a plurality of channels in the touch input device according to the embodiment of the present invention. 
     When a pressure is applied to the touch surface (S 10 ), the magnitude of the touch pressure is detected based on the sum of the change amounts of the capacitances detected in the respective channels (S 20 ). For example, the magnitude of the touch pressure can be calculated based on the sum of the change amounts of the capacitances detected in the respective fifteen first electrodes  450  in the pressure sensor  440  shown in  FIG. 13 d   . As such, by using a value obtained by adding the pressure magnitudes detected from the respective channels (or the capacitance values corresponding thereto) or an average value of the pressure magnitudes detected from the respective channels, the accuracy of the pressure magnitude detected by using the plurality of channels can be further improved than the accuracy of the pressure magnitude detected by using a single channel. 
     Example of Second Method 
       FIG. 14 a    is a view showing that a pressure is applied to a predetermined position in the pressure sensor shown in  FIG. 13 d   .  FIG. 14 b    is a cross sectional view showing a form in which the touch input device is bent when the touch pressure is applied to a touch surface corresponding to a position “A” of  FIG. 14 a   .  FIG. 14 c    is a cross sectional view showing a form in which the touch input device is bent when the touch pressure is applied to a touch surface corresponding to a position “C” of  FIG. 14   a.    
     When the touch pressure is applied to the touch surface corresponding to a position “A” shown in  FIG. 14 a   , that is, when the touch pressure is applied to the central portion of the display module  200 , the degree of bending of the display module  200  may be relatively high as shown in  FIG. 14 b   . On the other hand, when the touch pressure is applied to the touch surface corresponding to a position “C” shown in  FIG. 14 a   , that is, when the touch pressure is applied to the edge of the display module  200 , the degree of bending of the display module  200  may be relatively small as shown in  FIG. 14 c   . Specifically, as shown in  FIGS. 14 b  and 14 c   , when the same touch pressure is applied, the distance d 1  between the pressure electrode  450  and the position where the display module  200  is most bent when the touch pressure is applied to the central portion of the display module  200  may be smaller than the distance d 2  between the pressure electrode  450  and the position where the display module  200  is most bent when the touch pressure is applied to the edge of the display module  200 . Therefore, even though the same touch pressure is applied, the capacitance change amounts detected in the respective channels are different according to the position where the touch pressure is applied. Therefore, there is a requirement for a method capable of detecting a more accurate pressure value than the pressure value detected by using the magnitude of the pressure detected from each channel or by using the sum or average of the capacitances, which corresponds to the magnitude. 
       FIG. 20 b    is a flowchart for describing another example of a method for detecting the magnitude of the touch pressure by using a plurality of channels in the touch input device according to the embodiment of the present invention.  FIG. 15  is a view showing a scaling factor assigned to each first electrode in the pressure sensor shown in  FIG. 13   d.    
     When a pressure is applied to the touch surface (S 100 ), the magnitude of the touch pressure is detected based on the sum of values obtained by multiplying the change amount of the capacitance detected in each of the channels by a scaling factor assigned previously to each of the channels (S 200 ). For example, as shown in  FIG. 15 , a scaling factor of 1 is assigned to the first electrode  450  located at the central portion of the display module  200 , a scaling factor of 6 is assigned to the first electrodes  450  adjacent to the first electrode  450  located at the central portion, and scaling factors of 12 and 16 are respectively assigned to the first electrodes  450  located at the edge. As described above, when a smaller scaling factor is assigned to the channel corresponding to the central portion of the display module  200  and a larger scaling factor is assigned to the channel corresponding to the edge of the display module  200 , the central portion of the display module  200  is, as shown in  FIGS. 14 b  and 14 c   , bent more than the edge of the display module  200  when the same pressure is applied. Therefore, it is possible to offset that the change amount of the capacitance detected at the central portion of the display module  200  becomes greater than the change amount of the capacitance detected at the edge of the display module  200 . As a result, a more accurate pressure value can be calculated. 
     Example of Third Method 
       FIG. 16 a    is a graph for describing, when the pressure is applied to the position shown in  FIG. 14 a   , a relation between a volume change amount of the touch input device and the magnitude of the applied pressure.  FIG. 16 b    is a cross sectional view showing the volume change amount of the touch input device shown in  FIG. 14 b   .  FIG. 16 c    is a cross sectional view showing the volume change amount of the touch input device shown in  FIG. 14   c.    
     When the same touch pressure is applied, a volume (hereinafter, referred to as volume change amount) at which the touch input device  1000  is deformed when the touch pressure is applied to the central portion of the display module  200  may be greater than the volume change amount of the touch input device  1000  when the touch pressure is applied to the edge of the display module  200 . In other words, when the same touch pressure is applied to the touch surface corresponding to the positions “A”, “B”, and “C” shown in  FIG. 14 a   , as shown in  FIGS. 16 a  to 16 c   , the volume change amount of the touch input device  1000  when the touch pressure is applied to the position “A”, the central portion of the display module  200 , is greater than the volume change amount of the touch input device  1000  when the touch pressure is applied the position “C” located at the edge relative to the position “A” of the display module  200 . 
     Here, when the touch pressure is applied to the same position, the magnitude of the applied pressure and the volume change amount of the touch input device  1000  have a linear relationship. In other words, when the touch pressures having different magnitudes are applied to any one of the positions “A”, “B”, and “C” shown in  FIG. 14 a   , the volume change amount of the touch input device  1000  is, as shown in  FIG. 16 a   , changed in proportion to the magnitude of the applied pressure. 
     Therefore, the magnitude of the pressure can be detected by estimating the volume change amount of the touch input device  1000 . 
     First, when a pressure having a predetermined magnitude is applied to a predetermined touch position of the display module  200 , a reference value corresponding to the touch position is stored in a memory (not shown) on the basis of the capacitance detected from each channel. In this case, the reference value may be the volume change amount of the touch input device  1000  calculated based on the capacitance detected from each channel. Alternatively, the reference value may be a normalized pressure value having a linear relationship with the volume change amount of the touch input device  1000 , or may be a slope in the graph shown in  FIG. 16 a   . Such a method is repeatedly performed for each touch position, and the reference value for all positions of the entire area of the display module  200  when a pressure having a predetermined magnitude is applied is stored in the memory. Here, since it is difficult to generate the reference value for all positions of the entire area of the display module  200 , the reference value may be generated and stored only for a plurality of representative positions spaced apart by a predetermined interval. For example, the volume change amounts of 432 calculated based on each capacitance change amount detected when a pressure of 800 g is applied to each of the touch positions of 432 (18×24) spaced apart at regular intervals of the display module  200  may be stored in the memory. 
     Next, a method for detecting the magnitude of the touch pressure by using the reference value is shown. 
       FIG. 20 c    is a flowchart for describing further another example of a method for detecting the magnitude of the touch pressure by using a plurality of channels in the touch input device according to the embodiment of the present invention.  FIG. 17 a    is a partial perspective view for describing a form in which the touch input device is deformed when the pressure is applied to the touch input device.  FIG. 17 b    is a view for describing the estimation of the volume change amount of the touch input device when the pressure is applied to the touch input device.  FIG. 17 c    is a cross sectional view of  FIG. 17   b.    
     When a pressure is applied to the touch surface (S 1000 ), the touch position is detected (S 2000 ), and a distance change corresponding to each channel is calculated from the change amount of the capacitance detected in each channel (S 3000 ). 
     The value of capacitance detected in each channel depends on the configuration of the pressure electrode or the configuration of the circuit for sensing the touch pressure. However, when the touch pressure is applied, the value of capacitance can be represented by a function of the distance change “di” corresponding to each channel shown in  FIG. 17 c   . Therefore, it is possible to calculate the distance change “di” corresponding to each channel by performing an inverse calculation on the capacitance value detected from each channel. Here, the distance change “di” corresponding to each channel means a distance which corresponds to each channel and at which the surface of the touch input device is deformed after the pressure is applied with respect to the time before the pressure is applied. 
       FIG. 18 a    shows an equivalent circuit of a device for sensing a pressure capacitance  11  between the first electrode  450  and the second electrode  460  when, as shown in  FIGS. 13 a  to 13 c   , the first electrode  450  is composed of the drive electrode TX and the second electrode  460  is composed of the receiving electrode RX, so that the magnitude of the touch pressure is detected from the change of the mutual capacitance between the first electrode  450  and the second electrode  460 . Here, a relational expression between the driving signal Vs and the output signal Vo can be expressed by the following equation (1). 
     
       
         
           
             
               
                 
                   
                     v 
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                           C 
                           p 
                         
                         
                           C 
                           FB 
                         
                       
                     
                     · 
                     
                       v 
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     Here, among the capacitance between the first electrode  450  and the second electrode  460 , the capacitance which is lost as a reference potential layer is fringing capacitance. Here, the pressure capacitance  11  can be expressed as follows.
 
 C   p   =C   0   +C   fringing   =C   0   +αf ( d )  Equation (2)
 
     Here, Co is a fixed capacitance value generated between the first electrode  450  and the second electrode  460 , and C fringing  is a capacitance value generated by fringing effect between the first electrode  450  and the second electrode  460 . The equation (2) represents the value of C fringing  by the distance “d” and a coefficient “α”. The fixed capacitance means a capacitance generated by the first electrode  450  and the second electrode  460  irrespective of the distance “d” between the reference potential layer and the electrode. 
     When a random pressure is applied to any position of the display module  200 , the distance change “di” corresponding to each channel can be calculated by performing an inverse calculation on the capacitance change amounts detected in each of the channels, the equation (1), and the equation (2). 
       FIG. 18 b    shows an equivalent circuit of a device for sensing the capacitance  11  between the first electrode  450  and the reference potential layer when, as shown in  FIG. 13 d   , the driving signal is applied to the first electrode  450  and the reception signal is detected from the first electrode  450 , so that the magnitude of the touch pressure is detected from the change of the self-capacitance of the first electrode  450 . 
     When a first switch  21  is turned on, a capacitor for sensing the pressure capacitance  11  is charged to a power supply voltage VDD to which one end of the first switch  21  is connected. When a third switch  23  is turned on immediately after the first switch  21  is turned off, the electric charges charged in the capacitor for sensing the pressure capacitance  11  are transferred to an amplifier  31  to obtain the output signal Vo corresponding thereto. When a second switch  22  is turned on, all the electric charges remaining in the capacitor for sensing the pressure capacitance  11  are discharged. When the third switch  23  is turned on immediately after the second switch  22  is turned off, the electric charges are transferred to the capacitor for sensing the pressure capacitance  11  through a feedback capacitor  32  to obtain the output signal corresponding thereto. Here, the output signal Vo of the circuit shown in  FIG. 18 b    can be expressed by the following equation (3). 
     
       
         
           
             
               
                 
                   
                     
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     Here, ε is a dielectric constant ε o ε r  of the material filled between the first electrode  450  and the reference potential layer, and “A” is the area of the first electrode  450 . 
     When a random pressure is applied to any position of the display module  200 , the distance change “di” corresponding to each channel can be calculated by performing an inverse calculation on the capacitance change amounts detected in each of the channels and the equation (3). 
     The volume change amount of the touch input device is estimated by using the calculated distance change “di” corresponding to each channel (S 4000 ). Specifically, when the touch pressure is applied, the surface of the touch input device  1000  is deformed as shown in  FIG. 17 a   , and the volume change amount of the touch input device  1000  due to the deformation of the surface of the touch input device  1000  can be estimated as the sum of the volume change amounts corresponding to the respective channels shown in  FIGS. 17 b  and 17 c   . Here, when the areas corresponding to the respective channels are the same, for example, when the areas of the first electrodes  450  shown in  FIG. 13 d    are the same, the sum of the volume change amounts corresponding to the respective channels may be a value obtained by multiplying the sum of the distance changes “di” corresponding to the respective channels by the area “A” of the first one electrode  450 . 
     Here, when the touch pressure is applied to a predetermined position, the magnitude of the applied pressure and the volume change amount of the touch input device  1000  have, as shown in  FIG. 16 a   , a linear relationship. Therefore, the magnitude of the applied pressure is calculated on the basis of the estimated volume change amount of the touch input device  1000  and the reference value which is stored in the memory and corresponds to the touch position (S 5000 ). 
     For example, when the estimated volume change amount of the touch input device  1000  is 1000 and the volume change amount stored in the memory as a reference value corresponding to the touch position for a pressure of 800 g is 2000, the magnitude of the applied pressure is 400 g. 
     Also, when the reference value corresponding to the input touch position is not stored in the memory, the pressure value can be calculated through various interpolations such as linear interpolation, bi-cubic interpolation, etc., by using the reference value which is stored in the memory and corresponds to a touch position adjacent to the input touch position. 
       FIG. 19 a    is a view for describing a case where a pressure is applied to a position of the pressure sensor shown in  FIG. 14 a   , which corresponds to a position “D” of  FIG. 19 a   .  FIG. 19 b    is a graph for describing the calculation of the pressure value when the pressure is applied to the position “D” shown in  FIG. 19   a.    
     For example, when reference values corresponding to the position “A” and the position “B” shown in  FIG. 19 a    are stored in the memory and when a reference value corresponding to the position “D” which is a mid-point between the position “A” and the position “B” is not stored in the memory, the reference value of the position “D” can be, as shown in  FIG. 19 b   , estimated by linearly interpolating the reference values of the position “A” and the position “B”, that is to say, by taking an intermediate value between the reference value of the position “A” and the reference value of the position “B”. The magnitude of the pressure applied to the position “D” can be calculated by using the estimated reference value of the position “D”. 
     The foregoing has described that the third method for detecting the touch pressure by using the plurality of channels. However, as shown in  FIGS. 10 a  to 11 c   , the third method can be applied even when the pressure electrodes  450  and  460  constitute a single channel. 
     When a pressure is applied to the touch surface, the touch position is detected, and the distance change can be calculated from the change amount of the capacitance detected in the single channel. 
     The value of the capacitance detected in the single channel can be represented by a function of the distance change corresponding to the single channel. Therefore, the distance change corresponding to the single channel can be calculated by performing an inverse calculation on the capacitance value detected from the single channel. 
     When a random pressure is applied to any position of the display module  200 , the distance change corresponding to the single channel can be calculated by performing an inverse calculation on the capacitance change amount detected in the single channel and the equations (1), (2) or (3). 
     The volume change amount of the touch input device is estimated by using the calculated distance change corresponding to the single channel. Specifically, when the touch pressure is applied, the volume change amount of the touch input device may be a value obtained by multiplying the distance change corresponding to the single channel by the areas of the single electrodes  450  and  460 . 
     Here, when the touch pressure is applied to a predetermined position, the magnitude of the applied pressure and the volume change amount of the touch input device  1000  have, as shown in  FIG. 16 a   , a linear relationship. Therefore, the magnitude of the applied pressure is calculated on the basis of the estimated volume change amount of the touch input device  1000  and the reference value which is stored in the memory and corresponds to the touch position. 
     As described above, by calculating the magnitude of the pressure on the basis of the volume change amount by the touch pressure, it is possible to detect a more accurate pressure magnitude. The accurate magnitude of the pressure can be detected even though the reference potential layer or the pressure sensor is deformed from its initial position. 
     Although the pressure sensor  440  having the type shown in  FIG. 13 d    has been described above, the embodiment of the present invention is not limited to this. The embodiment of the present invention can be applied to a pressure sensor including the pressure electrode having the types shown in  FIGS. 13 a    to  13   c.    
     When the pressure sensor  440  is configured to form a plurality of channels, multi pressure of a multi touch can be detected. This can be performed, for example, by using the pressure magnitudes obtained from the channels of the pressure electrodes  450  and  460  disposed at a position corresponding to each of the multiple touch positions obtained from the touch sensor panel  100 . Alternatively, when the pressure sensor  440  is configured to form a plurality of channels, the touch position can be directly detected by the pressure sensor  440 , and multi pressure can be also detected by using the pressure magnitudes obtained from the channels of the pressure electrodes  450  and  460  disposed at the corresponding position. 
     Although embodiments of the present invention were described above, these are just examples and do not limit the present invention. Further, the present invention may be changed and modified in various ways, without departing from the essential features of the present invention, by those skilled in the art. For example, the components described in detail in the embodiments of the present invention may be modified. Further, differences due to the modification and application should be construed as being included in the scope and spirit of the present invention, which is described in the accompanying claims. 
     
       
         
           
               
             
               
                   
               
               
                 REFERENCE NUMERALS 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 1000: touch input device 
                 100: touch sensor panel 
               
               
                   
                 120: drive unit 
                 110: sensing unit 
               
               
                   
                 130: controller 
                 200: display module 
               
               
                   
                 300: substrate 
                 420: spacer layer 
               
               
                   
                 440: pressure sensor 
                 450, 460: pressure electrode 
               
               
                   
                 470: first insulation layer 
                 471: second insulation layer 
               
            
           
           
               
               
            
               
                   
                 470a, 471a: electrode covering layer 
               
            
           
           
               
               
               
            
               
                   
                 470b, 471b: support layer 
                 430: adhesive layer 
               
               
                   
                 435: protective layer 
                 480: elastic layer