Patent Publication Number: US-2015062071-A1

Title: Method for detecting touch points of touch panel

Description:
RELATED APPLICATIONS 
     This application claims all benefits accruing under 36 U.S.C. §119 from China Patent Application No. 201310386930.0, filed on Aug. 30, 2013 in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference. This application is related to applications entitled, “TOUCH PANEL,” filed _____ (Atty. Docket No. US53375); and entitled, “METHOD FOR DETECTING TOUCH POINTS OF TOUCH PANEL,” filed _____ (Atty. Docket No. US53378). 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a method for detecting touch points of a touch panel. 
     2. Description of Related Art 
     Touch sensing technology is capable of providing a natural interface between an electronic system and a user, and has found widespread applications in various fields, such as mobile phones, personal digital assistants, automatic teller machines, game machines, medical devices, liquid crystal display devices, and computing devices. There are different types of touch panels. However, these touch panels can only achieve two-dimensional control, not three-dimensional control. 
     What is needed, therefore, is to provide a method for detecting touch points of the touch panel, which can overcome the above-described shortcomings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
         FIG. 1  is a schematic view of one embodiment of a capacitive touch panel. 
         FIG. 2  shows a schematic view of different conductive layers of the capacitive touch panel of  FIG. 1  when the capacitive touch panel is pressed by a pressure. 
         FIG. 3  shows a schematic view of a change of an interval of the capacitive touch panel of  FIG. 1  when the capacitive touch panel is pressed by a pressure. 
         FIG. 4  is a flow chart of one embodiment of a method for detecting a touch point by using the capacitive touch panel of  FIG. 1 . 
         FIG. 5  shows a schematic view of a capacitance change between the first conductive layer and the second conductive layer of the capacitive touch panel of  FIG. 1 , when the capacitive touch panel is pressed by a pressure. 
         FIG. 6  shows a schematic view of a capacitance change between the second conductive layer and the third conductive layer of the capacitive touch panel of  FIG. 1 , when the capacitive touch panel is pressed by a pressure. 
         FIG. 7  is a schematic view of another embodiment of a capacitive touch panel. 
         FIG. 8  is a flow chart of one embodiment of a method for detecting a touch point of the capacitive touch panel of  FIG. 7 . 
         FIG. 9  shows a schematic view of a capacitance change between the second conductive layer and the fourth conductive layer of the capacitive touch panel of  FIG. 7 , when the capacitive touch panel is pressed by a pressure. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
     Referring to  FIG. 1 , according to one embodiment, a capacitive touch panel  100  comprises a first electrode plate  12 , a number of supporters  14  and a second electrode plate  16 . The first electrode plate  12  and the second electrode plate  16  are spaced from each other by the supporters  14  to form an interval  18 . The interval  18  between the first electrode plate  12  and the second electrode plate  16  can be changed when a pressure is applied on the capacitive touch panel  100 . 
     The first electrode plate  12  comprises a first conductive layer  122 , a first substrate  124  and a second conductive layer  126 . The first conductive layer  122  and the second conductive layer  126  form a two-dimensional coordinate touching module capable of detecting the coordinates along two directions (e.g., X and Y shown in  FIG. 1 ) substantially parallel to a surface of the touch panel  100 . The first conductive layer  122  is located on a first surface of the first substrate  124  away from the second electrode plate  16 . The first conductive layer  122  comprises a number of first conductive channels. The second conductive layer  126  is located on a second surface of the first substrate  124  adjacent to the second electrode plate  16 . The second conductive layer  126  comprises a number of second conductive channels. Each of the first conductive channels is aligned along a first direction. Each of the second conductive channels is aligned along a second direction. The first direction and the second direction cross with each other. A first capacitance can be formed between each of the first conductive channels and each of the second conductive channels. The first capacitance can be used to detect a two-dimensional coordinate (X, Y) of a touch point. In one embodiment, the first direction and the second direction are substantially perpendicular with each other and substantially parallel to Y axis and X axis respectively. The number of the first conductive channels and the second conductive channels can be selected according to a size and a touch-control precision of the capacitive touch panel  100 . 
     The second electrode plate  16  comprises a third conductive layer  162  and a second substrate  164 . The third conductive layer  162  is located on a first surface of the second substrate  164  adjacent to the first electrode plate  12 . Thus, the third conductive layer  162  and the second conductive layer  126  are spaced from each other by the interval  18 . The second conductive layer  126  and the third conductive layer  162  form a third-dimensional coordinate touching module capable of detecting the coordinate along a direction (e.g., Z shown in  FIG. 1 ) substantially perpendicular to the surface of the touch panel  100 . The third conductive layer  162  comprises a number of third conductive channels arranged substantially along a third direction. The third direction of the third conductive channels and the second direction of the second conductive channels cross with each other. In one embodiment, the third direction of the third conductive channels is substantially perpendicular to the second direction of the second conductive channels. That is, each of the third conductive channels can also be aligned substantially along the first direction. A second capacitance can be formed between each of the second conductive channels and each of the third conductive channels. The second capacitance can be used to detect a third-dimensional coordinate (Z) of a touch point. The interval  18  between the second conductive channels and the third conductive channels can be changed when a pressure is applied on the capacitive touch panel  100 . The number of the third conductive channels can be equal to the number of the first conductive channels. 
     A material of the first substrate  124  and the second substrate  164  can be a flexible material having a good transparency. The material of the first substrate  124  and the second substrate  164  can be polymethylmethacrylate, polycarbonate, polyethylene terephthalate, polyimide, or cyclic olefin copolymer. 
     The first conductive layer  122 , the second conductive layer  126 , and the third conductive layer  162  are all anisotropic impedance layers, and can be formed by ITO, metals, graphene, or a carbon nanotube film. The carbon nanotube film comprises a number of carbon nanotubes arranged substantially along a same direction, and joined end to end substantially along the arranged direction. The carbon nanotubes of the carbon nanotube film are joined end to end substantially along the arranged direction to form a number of conductive channels substantially along the arranged direction. The carbon nanotube film has a minimum impedance along the arranged direction of the carbon nanotubes and a maximum impedance along the direction substantially perpendicular to the arranged direction of the carbon nanotubes, thus having anisotropic impedance. In one embodiment, the first conductive layer  122 , the second conductive layer  126 , and the third conductive layer  162  are formed by a number of ITO conductive strips. 
     A material of the supporters  14  can be electric insulative materials. 
     A gas, an electric insulative fluid, or an elastic electric insulative solid can be filled into the interval  18 . The electric insulative fluid and the elastic electric insulative solid can be transparent or translucent. In one embodiment, the capacitive touch panel  100  does not include supporter  14  therein because the first electrode plate  12  and the second electrode plate  16  are spaced from each other by the electric insulative solid. 
     In one embodiment, the capacitive touch panel  100  further comprises a transparent protective film  10  to protect the first electrode plate  12 . A material of the transparent protective film  10  can be silicon nitride, silicon oxide, benzocyclobutene, polyester, or acrylic resin. 
     Referring to  FIG. 2 , when a touch point A is pressed by a user, the value of the first capacitance between the first conductive channels and the second conductive channels can be changed. Thus, the two-dimensional coordinate (X, Y) of the touch point A can be achieved according to a capacitance change of the first capacitance. Referring to  FIG. 3 , with the decrease of the interval  18  between the second conductive channels and the third conductive channels, the value of the second capacitance increases. Thus, the third-dimensional coordinate (Z) of the touch point A can be achieved according to a capacitance change of the second capacitance. 
     The capacitive touch panel  100  can further include a display module (not shown). The display module can be located on a second surface of the second substrate  164  opposite to the first surface of the second substrate  164 . In one embodiment, a thickness of the capacitive touch panel  100  is decreased because the display module and the second electrode plate  16  share the same second substrate  164 . 
     Referring to  FIG. 4 , one embodiment of a method for detecting a touch point T of the capacitive touch panel  100  comprises: 
     S10, applying a first driving signal to one of the first conductive layer  122  and the second conductive layer  126 , and obtaining a capacitance change ΔC 1  of the first capacitance from the other of the first conductive layer  122  and the second conductive layer  126  that the first driving signal is not applied thereon; 
     S11, determining a two-dimensional coordinate (X, Y) of the touch point T according to the capacitance change ΔC 1 ; 
     S12, applying a second driving signal to one of the second conductive layer  126  and the third conductive layer  162 , and obtaining a capacitance change ΔC 2  of the second capacitance from the other of the second conductive layer  126  and the third conductive layer  162  that the second driving signal is not applied thereon; 
     S13, comparing the ΔC 2  with a threshold value C 0 ; if ΔC 2 &gt;C 0 , outputting a three-dimensional coordinate (X, Y, Z) of the touch point T; if ΔC 2 ≦C 0 , outputting the two-dimensional coordinate (X, Y) of the touch point T. 
     In step S10, when the first driving signal is applied to one of the first conductive layer  122  and the second conductive layer  126 , the third conductive layer  162  can be connected to ground. When the first driving signal is applied to the first conductive layer  122 , the capacitance change ΔC 1  can be obtained by scanning the second conductive layer  126 . When the first driving signal is applied to the second conductive layer  126 , the capacitance change ΔC 1  can be obtained by scanning the first conductive layer  122 . In one embodiment, the first driving signal is applied to the second conductive layer  126 , and the capacitance change AC 1  is obtained by scanning the first conductive layer  122 . Thus a noise between the first conductive layer  122  and second conductive layer  126  can be reduced. 
     The first driving signal can be applied to the first conductive channels of the first conductive layer  122  one by one or at the same time. When the first driving signal is applied to the first conductive channels one by one, the other first conductive channels without the first driving signal applied thereon can be connected to ground or floating. The first driving signal can also be applied to the second conductive channels of the second conductive layer  126  one by one or at the same time. When the first driving signal is applied to the second conductive channels one by one, the other second conductive channels without the first driving signal applied thereon can also be connected to ground or floating. In one embodiment, the first driving signal is applied to the second conductive channels one by one, and the other second conductive channels without the first driving signal applied thereon is connected to ground. 
     In step S11, referring to  FIG. 5 , before touching the capacitive touch panel  100 , the first capacitance between the first conductive layer  122  and the second conductive layer  126  is C 1 . During the touching process, a coupled capacitance C 2  between a finger and the first conductive layer  122  can be formed. The first capacitance between the first conductive layer  122  and the second conductive layer  126  can be affected by the coupled capacitance C 2 , and be changed to C 1 ′. The capacitance change ΔC 1  and the first capacitance C 1  and C 1 ′ satisfy a formula: ΔC 1 =C 1 ′-C 1 . The two-dimensional coordinate (X, Y) of the touch point T can be determined according to the capacitance change ΔC 1 . 
     In step S12, the first conductive layer  122  can be connected to ground. 
     The capacitance change ΔC 2  of the second capacitance can be obtained by a mutual sensing method. For example, when the second driving signal is applied to the second conductive layer  126 , the capacitance change ΔC 2  of the second capacitance can be obtained by scanning the third conductive layer  162 ; or when the second driving signal is applied to the third conductive layer  162 , the capacitance change ΔC 2  of the second capacitance can be obtained by scanning the second conductive layer  126 . 
     The second driving signal can be applied to all of the second conductive channels or the specific second conductive channels having the touch points T applied thereon one by one or at the same time. In one embodiment, a time for applying the second driving signal can be reduced because the second driving signal is applied only to the second conductive channels having the touch point T applied thereon. When the second driving signal is applied to the second conductive channels one by one, the other second conductive channels without the second driving signal applied thereon can be connected to ground or floating. The second driving signal can also be applied to all the third conductive channels of the third conductive layer  162  or the specific third conductive channels having the touch point T applied thereon one by one or at the same time. In another embodiment, the second driving signal is applied to the third conductive channels having the touch point T applied thereon one by one. When the second driving signal is applied to the third conductive channels one by one, the other third conductive channels without the second driving signal applied thereon can be connected to ground or floating. 
     When the second driving signal is applied to the second conductive channels, the capacitance change ΔC 2  can be obtained by scanning all of the third conductive channels or the specific third conductive channels having the touch points T applied thereon one by one or at the same time. In one embodiment, a period time of scanning the third conductive channels can be reduced because the capacitance change ΔC 2  is obtained only by scanning the third conductive channels having the touch points T applied thereon. When the second driving signal is applied to the third conductive channels, the capacitance change ΔC 2  can be obtained by scanning all of the second conductive channels or the specific second conductive channels having the touch points T applied thereon one by one or at the same time. In another embodiment, the capacitance change ΔC 2  is obtained by scanning the second conductive channels having the touch points T applied thereon. 
     In step S13, the threshold value C 0  can be determined according to a precision of the capacitive touch panel  100 , and can be greater than zero. Referring to  FIG. 6 , before touching, the second capacitance between the second conductive layer  126  and the third conductive layer  162  is C 3 . During the touching process, the second capacitance between the second conductive layer  126  and the third conductive layer  162  can be changed to C 3 ′. The capacitance change ΔC 2  and the second capacitance C 3  and C 3 ′ satisfy a formula: ΔC 2 =C 3 ′-C 3 . If ΔC 2 ≦C 0 , only the two-dimensional coordinate (X, Y) of the touch point T obtained in step S11 is outputted because the interval  18  between the second conductive layer  126  and the third conductive layer  162  is deemed to be unchanged. If ΔC 2 &gt;C 0 , the third-dimensional coordinate (Z) of the touch point T together with the two-dimensional coordinate (X, Y) of the touch point T obtained in step S11 are outputted because the interval  18  between the second conductive layer  126  and the third conductive layer  162  is deemed to decrease. 
     A pressure of the touch point T can be defined by the second capacitance C 3  and C 3 ′. For example, when C 3 ′=C 3 , the pressure of the touch point T can be defined as zero Newton (N); when C 3 ′=1.1×C 3 , the pressure of the touch point T can be defined as 0.1 N; when C 3   ′=1.2×C   3 , the pressure of the touch point T can be defined as 0.2 N, and so on. Furthermore, a second two-dimensional coordinate (X, Y) of the touch point T can also be obtained according to the capacitance change ΔC 2 , and be verified with the two-dimensional coordinate (X, Y) obtained according to the capacitance change ΔC 1 . Thus, the touch-control precision of the two-dimensional coordinate (X, Y) of the capacitive touch panel  100  can be further improved. 
     In some embodiments, when the capacitance change ΔC 2  reaches different predetermined values, such as 0.1×C 3 , 0.2×C 3 , 0.3×C 3 , and 0.4×C 3 , a different third-dimensional coordinate (Z) of the touch point T can be obtained. Thus, a touch-control precision of the third-dimensional coordinate (Z) of the capacitive touch panel  100  can be improved. 
     The capacitive touch panel  100  of the present embodiment has the following advantages. First, the pressure of the touch point can be detected by the second electrode plate  16 , thus the three-dimensional coordinate of the touch point can be obtained. Second, the two-dimensional coordinate and the third-dimensional coordinate of the touch point is obtained in different steps, thus preventing the two-dimensional coordinate and the third-dimensional coordinate of the touch point from influencing each other. Third, the number of the third conductive channels is equal to the number of the first conductive channels. Thus, different third-dimensional coordinates of different touch points can be obtained at the same time. 
     Referring to  FIG. 7 , according to another embodiment, a capacitive touch panel  200  comprises a first electrode plate  12 , a number of supporters  14 , and a second electrode plate  17 . The second electrode plate  17  is basically the same as the second electrode plate  16 , except that the second electrode plate  17  comprises a successive fourth conductive layer  166  having isotropic impedance. That is, the fourth conductive layer  166  has a substantially uniform impedance along different directions. The second conductive layer  126  and the fourth conductive layer  166  form a third-dimensional coordinate touching module capable of detecting the coordinate along a direction (e.g., Z shown in  FIG. 7 ) substantially perpendicular to the surface of the touch panel  200 . The fourth conductive layer  166  can be a transparent structure or a translucent structure. The fourth conductive layer  166  can be a successive ITO layer, a successive metal layer, a successive graphene layer, or a successive carbon nanotube layer having a number of carbon nanotubes uniformly dispersed therein. 
     Referring to  FIG. 8 , another embodiment of a method for detecting the touch point T of the capacitive touch panel  200  comprises: 
     S20, applying a first driving signal to one of the first conductive layer  122  and the second conductive layer  126 , and obtaining a capacitance change ΔC 1  of the first capacitance from the other of the first conductive layer  122  and the second conductive layer  126  that the first driving signal is not applied thereon; 
     S21, determining a two-dimensional coordinate (X, Y) of the touch point T according to the capacitance change ΔC 1 ; 
     S22, applying a second driving signal to one of the second conductive layer  126  and the fourth conductive layer  166 , and obtaining a capacitance change ΔC 3  of the second capacitance from the one of the second conductive layer  126  and the fourth conductive layer  166 ; 
     S23, comparing ΔC 3  with a threshold value C 0 ; if ΔC 3 &gt;C 0 , outputting a three-dimensional coordinate (X, Y) of the touch point T; if ΔC 3 ≦C 0 , outputting the two-dimensional coordinate (X, Y, Z) of the touch point T. 
     Steps S20 and S21 are the same as the steps S10 and S11 respectively. 
     In step S22, the capacitance change ΔC 3  can be obtained by a self-sensing method or the mutual-sensing method. In the self-sensing method, the second driving signal is applied to the second conductive layer  126  or the fourth conductive layer  166 , and the capacitance change ΔC 3  is obtained by scanning the second conductive layer  126  or the fourth conductive layer  166  with the second driving signal applied thereon at the same time. 
     In one embodiment, the second driving signal is applied to the second conductive layer  126 , and the capacitance change ΔC 3  is obtained by scanning the second conductive layer  126  at the same time. At this time, the first conductive layer  122  and the fourth conductive layer  166  can be connected to ground or floating. Specifically, the second driving signal can be applied to a first end of the second conductive channels of the second conductive layer  126 , and the capacitance change ΔC 3  can be obtained by scanning the first end or a second end opposite to the first end of the second conductive channels at the same time. In one embodiment, the second driving signal is applied to the first end of the specific second conductive channels having the touch point T applied thereon, and the capacitance change ΔC 3  is obtained by scanning the second end opposite to the first end of the second conductive channels at the same time. Thus, a period time of step S22 can be reduced. 
     In another embodiment, a single second driving signal is applied to the fourth conductive layer  166 , and the capacitance change ΔC 3  is obtained by scanning the fourth conductive layer  166  at the same time. This is because the fourth conductive layer  166  is a successive conductive layer having a substantially uniform impedance along different directions. At this time, the first conductive layer  122  and the second conductive layer  126  can be connected to ground or floating. 
     In step S23, the threshold value C 0  can be determined according to a precision of the capacitive touch panel  200 , and can be greater than zero. Referring to  FIG. 9 , before touching, the second capacitance between the second conductive layer  126  and the fourth conductive layer  166  is C 4 . During touching, the second capacitance between the second conductive layer  126  and the fourth conductive layer  166  can be changed to C 4 ′. The capacitance change ΔC 3  and the second capacitance C 4  and C 4 ′ can satisfy a formula: ΔC 3 =C 4 ′-C 4 . If ΔC 3 ≦C 0 , only the two-dimensional coordinate (X, Y) of the touch point T obtained in step S21 is outputted because the interval  18  between the second conductive layer  126  and fourth conductive layer  166  is deemed to be unchanged. If ΔC 2 &gt;C 0 , the third-dimensional coordinate (Z) of the touch point T together with the two-dimensional coordinate (X, Y) of the touch point T obtained in step S21 are outputted because the interval  18  between the second conductive layer  126  and the fourth conductive layer  166  is deemed to decrease. 
     A pressure of the touch point T can be defined by the second capacitance C 4  and C 4 ′. For example, when C 4 ′=C 4 , the pressure of the touch point T can be defined as zero N; when C 4 ′=1.1×C 4 , the pressure of the touch point T can be defined as 0.1 N; when C 4 ′=1.2×C 4 , the pressure of the touch point T can be defined as 0.2 N, and so on. 
     In some embodiments, when the capacitance change ΔC 3  reaches different predetermined values, such as 0.1×C 4 , 0.2×C 4 , 0.3×C 4 , and 0.4×C 4 , different third-dimensional coordinates of the touch point T can be obtained. Thus, a touch-control precision of the third-dimensional coordinate (X, Y, Z) of the capacitive touch panel  200  can be improved. 
     Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the present disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. Elements associated with any of the above embodiments are envisioned to be associated with any other embodiments. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure. 
     Depending on the embodiment, certain of the steps of methods described may be removed, others may be added, and the sequence of steps may be altered. It is also to be understood that the description and the claims drawn to a method may include some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps.