Patent Publication Number: US-2013249860-A1

Title: Pressure-sensing type touch panel

Description:
PRIORITY 
     This application claims priority under 35 U.S.C. §119(a) to a Korean Patent Application filed in the Korean Industrial Property Office on Mar. 22, 2012 and assigned Serial No. 10-2012-0029574, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
       1 . Field of the Invention 
     The present invention relates generally to a pressure-sensing type touch panel, and more particularly to a pressure-sensing type touch panel adapted to be flexible and to stably recognize the touch of an object even when deformed. 
     2. Description of the Related Art 
     Portable terminals have evolved into multimedia devices capable of providing various functions including, but not limited to transmission/reception, electronic organizer, game, and schedule management functions. Accordingly, portable terminals are connected with various external devices to expand their functionality to such activities as music listening, movie watching, and photography. 
     Input devices for portable terminals include key buttons, a mouse, and a digitizer. However, portable terminals having touch panels have increased in use, which enables various types of inputs simply by touch of an object. Particularly, significant attention has been given to flexible portable terminals, which have evolved from portable terminals equipped with touch panels. 
     Conventional technology related to touch panels is disclosed in Korean Registered Patent No. 10-0347439, issued Jul. 23, 2002, entitled “Touch Panel Pressure Sensing Structure and Sensing Method”, the contents of which are incorporated herein by reference. 
       FIGS. 1-3  illustrate schematic structures of conventional touch panels. Referring to  FIGS. 1-3 , the touch panels  10 ,  20 ,  30  have a plurality of sheets stacked on one another. Specifically, the touch panels  10 ,  20 ,  30  have upper panels  11 ,  21 ,  31  and lower panels  12 ,  22 ,  32 , which have electrodes intersecting with each other, and a gap is formed between the upper panels  11 ,  21 ,  31  and the lower panels  12 ,  22 ,  32 . Particularly, gaps  13 ,  23 ,  33  (such as air gaps or liquid gaps) are defined between the upper panels  11 ,  21 ,  31 , which have a single sheet or a plurality of sheets stacked on one another, and the lower panels  12 ,  22 ,  32 , which have a single sheet or a plurality of sheets stacked on one another, so that the electrodes of the upper and lower panels can contact each other by means of pressure caused by touch of an object. 
     The touch panel  10  shown in  FIG. 1  includes an upper panel  11 , which has conductive members extending in a first direction on both ends, and a lower panel  12  having conductive members extending in a second direction, which intersects with the first direction, on both ends. The upper and lower panels  11  and  12  are arranged to face each other with an air or a liquid gap  13  at the center. The touch panel  20  shown in  FIG. 2  includes an upper panel  21 , which has conductive members formed in the transverse direction (based on  FIG. 2 ), and a lower panel  22 , which has conductive members formed in the longitudinal direction (based on  FIG. 2 ). The upper and lower panels  21  and  22  are arranged to face each other with an air or a liquid gap  23  at the center. 
     The touch panel  30  shown in  FIG. 3  includes an upper panel  31 , which includes a substrate  31  a having conductive members formed in a first direction and a conductive layer  31   b,  and a lower panel  32  including a substrate  32   a  having conductive members formed in a second direction, which intersect with the first direction, and a conductive layer  32   b.  The upper and lower panels  31  and  32  are arranged to face each other with an air or a liquid gap  33  at the center. The touch panels  10 ,  20 ,  30  of the above-described structures can recognize pressure, which is generated by touch of an object, based on a current change caused by contact resistance. Specifically, the touch panels  10 ,  20 ,  30  scan a current change between electrodes of the upper panels  11 ,  21 ,  31  and electrodes of the lower panels  12 ,  22 ,  32 , which are adjacent to the place of transfer of pressure caused by touch of an object, and process the scan result to calculate the touch point. 
     When the touch panels  10 ,  20 ,  30  are adapted to be flexible, they undergo various types of deformation, depending on the environment, such as folding, bending or rolling. The existence of air or liquid gaps  13 ,  23 ,  33  between the upper panels  11 ,  21 ,  31  and the lower panels  12 ,  22 ,  32  generates a clearance between the stacked sheets. 
       FIG. 4  illustrates bending of upper panels  11 ,  21 ,  31  and lower panels  12 ,  22 ,  32 , which are stacked on each other with air or liquid gaps  13 ,  23 ,  33  at the center. Referring to  FIG. 4 , deformation of the touch panels  10 ,  20 ,  30  changes the radius of curvature of the upper panels  11 ,  21 ,  31  and the lower panels  12 ,  22 ,  32 . That is, deformation of the touch panels  10 ,  20 ,  30  changes the location at which the upper panels  11 ,  21 ,  31  and the lower panels  12 ,  22 ,  32  face each other. 
     The deformation also changes the distance between the upper panels  11 ,  21 ,  31  and the lower panels  12 ,  22 ,  32 , i.e. gap thickness. This reveals a problem of state-of-the-art touch panels  10 ,  20 ,  30 , which is the air or the liquid gaps  13 ,  23 ,  33  maintain a constant thickness before the touch panels  10 ,  20 ,  30  are deformed, but have great difficulty maintaining a constant thickness (i.e. the distance between the upper panels  11 ,  21 ,  31  and the lower panels  12 ,  22 ,  32  cannot be maintained) after the touch panels  10 ,  20 ,  30  are deformed. 
     Specifically, conventional touch panels  10 ,  20 ,  30  have a structural problem in that, when deformation increases the distance between parts of the upper panels  11 ,  21 ,  31  and the lower panels  12 ,  22 ,  32 , recognition of touch of an object on the parts may be too weak or even fail. Furthermore, when deformation decreases the distance between parts of the upper panels  11 ,  21 ,  31  and the lower panels  12 ,  22 ,  32 , erroneous recognition may be made even if there is no touch. 
     Therefore, there is a need for a pressure-sensing type touch panel adapted to have flexibility and to stably recognize the touch of an object even when deformed. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made to solve the above-stated problems occurring in the prior art, and an aspect of the present invention provides a pressure-sensing type touch panel including a plurality of sheets laminated to have a one-sheet structure, the touch panel being bonded to a rear surface of a flexible display. 
     In accordance with an aspect of the present invention, there is provided a pressure-sensing type touch panel including a pressure-sensing layer adapted to change in response to pressure, and sheets having conductive layers and electrode layers, respectively, the sheets being laminated to both surfaces of the pressure-sensing layer, respectively, to have a one-sheet structure, wherein the conductive layers and the electrode layers are adapted to change, in response to touch of an object, and cause the realization of a haptic feel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIGS. 1-3  illustrate structures of conventional touch panels; 
         FIG. 4  illustrates bending of touch panels having structures illustrated in  FIGS. 1-3 ; 
         FIG. 5  illustrates a schematic structure of a pressure-sensing type touch panel according to the present invention; 
         FIG. 6  illustrates the pressure-sensing type touch panel shown in  FIG. 5  after lamination; 
         FIG. 7  is a schematic top view of the pressure-sensing type touch panel shown in  FIG. 6 , and illustrates components at different sizes laminated on one another, ranging from the first substrate panel to the second substrate panel; 
         FIG. 8  illustrates local deformation of the pressure-sensing type touch panel shown in  FIG. 6 ; and 
         FIG. 9  illustrates a pressure value when a pressure is applied to a local portion on a laminate structure of the touch panel which is locally deformed in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings in detail. Various specific definitions found in the following description are provided only to help general understanding of the present invention, and it will be understood by those skilled in the art that various changes and modifications can be made thereto within the technical spirit and scope of the present invention. In the following description, a detailed explanation of known related functions and constitutions may be omitted for the sake of clarity and conciseness. 
     It is also be noted that, although ordinal numbers (such as first and second) are used in the following description, they are used only to distinguish similar components, the order of which is not limited, and description of former components also applies to the latter. In addition, the use of the term “deformation” herein generally refers to bending, rolling, or folding, but is not limited thereto. 
       FIG. 5  illustrates a schematic structure of a pressure-sensing type touch panel according to an embodiment of the present invention. Referring to  FIG. 5 , the pressure-sensing type touch panel  100  is bonded to the rear surface of a flexible display (not shown), and has a plurality of sheets laminated to have a one-sheet structure. Specifically, the pressure-sensing type touch panel has a pressure-sensing layer  130  adapted to change in response to pressure and positioned at the center, and sheets having conductive layers  112 ,  122  and electrode layers  113 ,  123  are laminated (lamination refers to a type of processing to overlap and bond at least two films of the same type or different types) to both surfaces of the pressure-sensing layer  130 , respectively, to provide a one-sheet structure. In particular, the pressure-sensing type touch panel  100  includes first and second layers  110  and  120  symmetrically positioned to each other and a pressure-sensing layer  130  positioned between the first and second layers  110  and  120  and adapted to change its resistance in response to pressure caused by touch of an object. 
     The touch panel  100  of this structure is obtained by arranging the first layer  110 , the pressure-sensing layer  130 , and the second layer  120  successively and laminating them. As a result, even if the flexible touch panel  100  is deformed, parts of the first and second layers  110  and  120 , which face each other, are not dislocated. That is, even if the touch panel  100  undergoes deformation, the first layer  110 , the pressure-sensing layer  130 , and the second layer  120  remain laminated to one another. 
       FIG. 6  illustrates the pressure-sensing type touch panel shown in  FIG. 5  after lamination.  FIG. 7  is a schematic top view of the pressure-sensing type touch panel shown in  FIG. 6 , and illustrates components at different sizes laminated on one another, ranging from the first substrate panel  111  to the second substrate panel  121 . Referring to  FIGS. 6 and 7 , the first and second layers  110  and  120  are formed to be symmetrically positioned to each other with the pressure-sensing layer  130  at the center. 
     Specifically, the first layer  110  includes a first conductive layer  112 , a first electrode layer  113 , and a first substrate panel  111 , which are arranged on a surface, i.e, an upper surface of the pressure-sensing layer  130  in this order. The first substrate panel  111  is positioned on the outermost part of the touch panel  100 . The first conductive layer  112  is positioned between the first substrate panel  111  and the pressure-sensing layer  130  and is directly laminated onto the upper surface of the pressure-sensing layer  130 . The first electrode layer  113  is arranged between the first substrate panel  111  and the first conductive layer  112  and is positioned on the first conductive layer  112  in a direction (vertical direction in this embodiment). The first layer  110 , which consists of a plurality of sheets, is laminated onto a surface of the pressure-sensing layer  130 , specifically the upper surface thereof, in the order of the first conductive layer  112  on the bottom, the first electrode layer  113  in the middle, and the first substrate panel  111  at the top of the first layer  110 . 
     The second layer  120  includes a second electrode layer  123 , a second conductive layer  122 , and a second substrate panel  121 , which are arranged on a lower surface of the pressure-sensing layer  130  in this order. The second substrate panel  121  is positioned on the outermost part of the touch panel  100 . The second conductive layer  122  is positioned between the second substrate panel  121  and the pressure-sensing layer  130  and is directly laminated onto the lower surface of the pressure-sensing layer  130 . The second electrode layer  123  is arranged between the second substrate panel  121  and the second conductive layer  122  and is positioned on the second conductive layer  122  in a direction, which intersects with the direction of formation of the first conductive layer  112  (horizontal direction in this embodiment). The second layer  120 , which consists of a plurality of sheets, is laminated on the other surface of the pressure-sensing layer  130 , specifically on the lower surface thereof, in the order of the second conductive layer  122 , the second electrode layer  123 , and the second substrate panel  121 . 
     The conductive layers  112  and  122  or the electrode layers  113  and  123  of the first and second layers  110  and  120  can realize haptics, i.e. the user can feel a touch, such as through a voltage change. Specifically, capacitive coupling is formed between the conductive layers  112  and  122  or the electrode layers  113  and  123  and the object, such as the body (or finger). When the conductive layers  112  and  122  or the electrode layers  113  and  123  are driven by an electric input of a low frequency (such as 10-500 Hz), the finger&#39;s touch causes the capacitive coupling to generate vibration Coulomb force, which stimulates the finger surface and provides a haptic feel. 
     The first conductive layer  112 , the first electrode layer  113 , the second conductive layer  122 , the second electrode layer  123 , and the pressure-sensing layer  130  are preferably made of a transparent material having a high degree of optical transmittance, such as ITO (Indium Tin Oxide) film. 
     The pressure-sensing layer  130  includes a material, the linear resistance of which varies in response to pressure generated by touch of an object. For example, the pressure-sensing layer  130  according to the present embodiment preferably includes QTC (Quantum Tunneling Composite) material, which uses Ni (Nickel) particles as the conductive material, but the present invention is not limited thereto. For example, the pressure-sensing layer  130  is made of a material obtained by mixing a base material (usually a high-molecular material such as rubber) with conductive particles at a suitable ratio. When the pressure-sensing layer  130  is subjected to force or pressure, the resulting contraction of material reduces the particle interval and allows electric current to flow. Examples of such material include conductive rubber, which uses carbon black as conductive particles, and FSR (Force Sensing Resistor). 
     The pressure-sensing type touch panel  100  is obtained by laminating the second substrate panel  121 , which serves as the bottom surface, the second electrode layer  123 , the second conductive layer  122 , the pressure-sensing layer  130 , the first conductive layer  112 , the first electrode layer  113 , and the first substrate panel  111 , in this order. Those skilled in the art can understand that, although two types of methods for manufacturing a pressure-sensing type touch panel  100  according to the present embodiment will now be described, the present invention is not limited to such methods, and various modifications are possible as long as the first layer  110 , the pressure-sensing layer  130 , and the second layer  120  are fastened to one another to form a single sheet. In a method for manufacturing a pressure-sensing type touch panel  100  according to the present embodiment, the second substrate panel  121  is used as the bottom surface, and, on the second substrate panel  121 , the second electrode layer  123 , the second conductive layer  122 , the pressure-sensing layer  130 , the first conductive layer  112 , the first electrode layer  113 , and the first substrate panel  111  are successively printed and laminated. 
     In another method for manufacturing a pressure-sensing type touch panel  100 , the second electrode layer  123  and the second conductive layer  122  are bonded to the second substrate panel  121  to obtain the second layer  120 ; the first electrode layer  113  and the first conductive layer  112  are bonded to the first substrate panel  111  to obtain the first layer  110 ; the pressure-sensing layer  130  is arranged between the fabricated first and second layers  110  and  120 , specifically between the first and second conductive layers  112  and  122 ; and the components are subjected to high temperature and high pressure to laminate them. 
       FIG. 8  illustrates local deformation of the pressure-sensing type touch panel shown in  FIG. 6 , and  FIG. 9  illustrates a pressure value when a pressure is applied to a local portion on a laminate structure of the touch panel which is locally deformed in  FIG. 8 . 
     Referring to  FIGS. 8 and 9 , in the local deformation of the pressure-sensing type touch panel  100  of the above-mentioned stacked and laminated structure, the first layer  110 , the pressure-sensing layer  130 , and the second layer  120 , which have been laminated, deform in the manner of a single sheet. This limits any change of thickness between the first and second layers  110  and  120  or dislocation of the first or second layer  110  or  120 . That is, the pressure-sensing type touch panel  100  maintains the stacked structure either before or after bending. Particularly, referring to  FIGS. 8 and 9 , it can be noted that the pressures are changed at a local portion  1  and a local portion  2  near the location  1  where the touches are inputted in the touch panel staying in the bent state, and there are no pressure change at remaining local portions  3  thru  13 . That is, the touch panel of the embodiment of the present invention is made in a form of one sheet without air gaps or liquid gaps, so as to definitely recognize the transmission of the pressure in a bent or folded state. As a result, it is possible for the touch panel to transmit the pressure more stably. Therefore, the touch panel  100  can accurately sense a touch at any location where pressure is applied, regardless of any deformation. 
     As described above, the pressure-sensing type touch panel according to the present invention has a pressure-sensing layer closely stacked between the first and second layers so that any change of distance between the first and second layers or their dislocation is prevented even if deformation occurs locally. 
     This ensures that the first and second layers can maintain a constant gap, regardless of flexible deformation, and the touch of an object can be sensed stably at any location. 
     While the present invention has been shown and described with reference to certain embodiments and drawings thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.