Patent Publication Number: US-2015062068-A1

Title: Sensing method based on capacitive touch panel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201310386965.4, filed on Aug. 30, 2013, in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to sensing methods of touch panel, particularly to a sensing method based on a capacitive touch panel. 
     2. Description of Related Art 
     Conventional touch panels detect contact areas between the touch conductors and the capacitive touch panels to reflect pressure information. However, if hard touch conductors are used, the contact areas may be constant regardless of the external forces applied on the touch panels. Therefore, pressure information detection may be inaccurate, and operation errors triggered. 
     What is needed, therefore, is to provide sensing methods for solving the problem discussed above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a schematic cross-sectional side view of an embodiment of a capacitive touch panel. 
         FIG. 2  is a schematic view of an embodiment of a first capacitive touch sensor and a second capacitive touch sensor of the capacitive touch panel. 
         FIG. 3  shows a schematic cross-sectional side view of another embodiment of the capacitive touch panel. 
         FIG. 4  is a schematic view of a morphological change of a deformable insulating layer of the capacitive touch panel from a non-pressed condition to a pressed condition. 
         FIG. 5  is a flowchart of an embodiment of a sensing method based on the capacitive touch panel. 
         FIG. 6  is a flowchart of one embodiment of a locating method of touch points based on the capacitive touch panel. 
         FIG. 7  is a flowchart of one embodiment of a method for obtaining a plurality of first sensing signal values in the method of  FIG. 6 . 
         FIG. 8  is a flowchart of one embodiment of the method for obtaining a first curve fitted by the plurality of first sensing signal values. 
         FIG. 9  is a flowchart of one embodiment of a method for sensing pressure information based on the capacitive touch panel. 
     
    
    
     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 , one embodiment of a capacitive touch panel  100  includes a first substrate  10 , a second substrate  20 , a first capacitive touch sensor  30 , a second capacitive touch sensor  40 , and a deformable insulating layer  50 . The first substrate  10  and the second substrate  20  are spaced from each other. The first capacitive touch sensor  30  is disposed on a surface of the first substrate  10  and located between the first substrate  10  and the second substrate  20 . The second capacitive touch sensor  40  is disposed on a surface of the second substrate  20  and located between the first substrate  10  and the second substrate  20 . The deformable insulting layer  50  is disposed between the first capacitive touch sensor  30  and the second capacitive touch sensor  40 , whereby a gap G is formed between the first capacitive touch sensor  30  and the second capacitive touch sensor  40 . A distance of the gap G changes if the deformable insulating layer  50  is deformed by a pressure. 
     The first substrate  10  and the second substrate  20  can be made of a transparent or opaque material. In one embodiment, the first substrate  10  and the second substrate  20  are made of transparent material. The transparent material can be glass, quartz, diamond, plastic, resin, polyethylene, polycarbonate, polyethylene terephathalate, polymethylmethacrylate, or combinations thereof. The first substrate  10  can be a protective layer for the capacitive touch panel  100 . In one embodiment, the first substrate  10  is a flexible and transparent plate. A display module can be used as the second substrate  20 . The display module is directly disposed on the second capacitive touch sensor  40  for displaying. 
     Referring to  FIG. 1  and  FIG. 2 , the first capacitive touch sensor  30  only includes a single conductive film for generating sensing signals to realize a multi-touch detection. The first capacitive touch sensor  30  includes a first conductive film  32  and a plurality of first driving-sensing electrodes  34  electrically connected with the first conductive film  32 . 
     The first conductive film  32  can be transparent or opaque. The first conductive film  32  can be an anisotropic impedance layer with continuous conductivity. Continuous conductivity means that a conductive network constituting a plurality of conductive traces electrically connected with each other can be formed on the first conductive film  32 . The anisotropic impedance layer is a layer having a relatively low impedance direction D and a relatively high impedance direction H on the same surface (e.g., the surface of the first conductive film  32 ). The electrical conductivity of the anisotropic impedance layer on the relatively high impedance direction H is smaller than the electrical conductivities of the anisotropic impedance layer in other directions. The electrical conductivity of the anisotropic impedance layer on the relatively low impedance direction D is larger than the electrical conductivities of the anisotropic impedance layer in other directions. The relatively high impedance direction H is different from the relatively low impedance direction D. In one embodiment, the relatively high impedance direction H is substantially perpendicular to the relatively low impedance direction D. The relatively high impedance direction H and the relatively low impedance direction D of the anisotropic impedance layer can be achieved by having a plurality of conductive belts having a low conductivity aligned along the relatively high impedance direction H and a plurality of conductive belts having a high conductivity aligned along the relatively low impedance direction D, and the plurality of conductive belts having the low conductivity and the plurality of conductive belts having the low conductivity are electrically connected with each other. In another embodiment, the relatively high impedance direction H and the relatively low impedance direction D of the anisotropic impedance layer can be achieved by having a carbon nanotube film comprising orderly arranged carbon nanotubes. The first conductive film  32  can have a square shape having two sides substantially perpendicular to the relatively high impedance direction H and two sides substantially perpendicular to the relatively low impedance direction D. The anisotropic impedance layer with the continuous conductivity can generate a leakage current to achieve precise touch detection. 
     A material of the first conductive film  32  can be at least one of carbon nanotubes, indium tin oxide, metal, and graphene. The first conductive film  32  can be a transparent mesh, with the anisotropic impedance, made of the carbon nanotubes, indium tin oxide, metal, graphene, or combinations thereof. 
     The first conductive film  32  can be a carbon nanotube film. The carbon nanotube film comprises a plurality of carbon nanotubes orderly arranged. The plurality of carbon nanotubes are substantially aligned along a same direction so that the carbon nanotube film has a maximum electrical conductivity at the aligned direction of the carbon nanotubes which is greater than at other directions. The aligned direction of the plurality of carbon nanotubes is the relatively low impedance direction D. The carbon nanotube film can be formed by drawing the film from a carbon nanotube array. The overall aligned direction of a majority of the carbon nanotubes in the carbon nanotube film is substantially aligned along the same direction and substantially parallel to a surface of the carbon nanotube film. The carbon nanotube is joined to adjacent carbon nanotubes end to end by van der Waals force therebetween, and the carbon nanotube film is capable of being a free-standing structure. A support having a large surface area to support the entire free-standing carbon nanotube film is not necessary, and only a supportive force at opposite sides of the film is sufficient. The free-standing carbon nanotube film can be suspended and maintain its film state with only supports at the opposite sides of the film. When disposing (or fixing) the carbon nanotube film between two spaced supports, the carbon nanotube film between the two supports can be suspended while maintaining its integrity. The successively and aligned carbon nanotubes joined end to end by van der Waals attractive force in the carbon nanotube film is one main reason for the free-standing property. The carbon nanotube film drawn from the carbon nanotube array has good transparency. In one embodiment, the carbon nanotube film is substantially a pure film and consists essentially of the carbon nanotubes, and to increase the transparency of the touch panel, the carbon nanotubes are not functionalized. 
     The plurality of carbon nanotubes in the carbon nanotube film have a preferred orientation along the same direction. The preferred orientation means that the overall aligned direction of the majority of carbon nanotubes in the carbon nanotube film is substantially along the same direction. The overall aligned direction of the majority of carbon nanotubes is substantially parallel to the surface of the carbon nanotube film, thus parallel to the surface of the polarizing layer. Furthermore, the majority of carbon nanotubes are joined end to end therebetween by van der Waals force. In this embodiment, the majority of carbon nanotubes are substantially aligned along the same direction in the carbon nanotube film, with each carbon nanotube joined to adjacent carbon nanotubes at the aligned direction of the carbon nanotubes end to end by van der Waals force. There may be a minority of carbon nanotubes in the carbon nanotube film that are randomly aligned, but the number of randomly aligned carbon nanotubes is small compared to the majority of substantially aligned carbon nanotubes and therefore will not affect the overall oriented alignment of the majority of carbon nanotubes in the carbon nanotube film. 
     In the carbon nanotube film, the majority of carbon nanotubes that are substantially aligned along the same direction may not be completely straight. Sometimes, the carbon nanotubes can be curved or not exactly aligned along the overall aligned direction, and can deviate from the overall aligned direction by a certain degree. Therefore, it cannot be excluded that partial contacts may exist between the juxtaposed carbon nanotubes in the majority of carbon nanotubes aligned along the same direction in the carbon nanotube film. Despite having curved portions, the overall alignment of the majority of the carbon nanotubes are substantially aligned along the same direction. 
     The carbon nanotube film includes a plurality of successive and oriented carbon nanotube segments. The plurality of carbon nanotube segments are joined end to end by van der Waals attractive force. Each carbon nanotube segment includes a plurality of carbon nanotubes that are substantially parallel to each other, and the plurality of parallel carbon nanotubes are in contact with each other and combined by van der Waals attractive force therebetween. The carbon nanotube segment can have a desired length, thickness, uniformity, and shape. The carbon nanotubes in the carbon nanotube film have a preferred orientation along the same direction. The carbon nanotube wires in the carbon nanotube film can consist of a plurality of carbon nanotubes joined end to end. The adjacent and juxtaposed carbon nanotube wires can be connected by the randomly aligned carbon nanotubes. There can be clearances between adjacent and juxtaposed carbon nanotubes in the carbon nanotube film. A thickness of the carbon nanotube film at the thickest location is about 0.5 nanometers to about 100 microns (e.g., in a range from 0.5 nanometers to about 10 microns). 
     The carbon nanotube film has a unique impedance property because the carbon nanotube film has a minimum electrical impedance in the drawing direction, and a maximum electrical impedance in the direction substantially perpendicular to the drawing direction, thus the carbon nanotube film has an anisotropic impedance property. A relatively low impedance direction D is the direction substantially parallel to the aligned direction of the carbon nanotubes, and a relatively high impedance direction H is substantially perpendicular to the aligned direction of the carbon nanotubes. The carbon nanotube film can have a square shape with four sides. Two sides are opposite to each other and substantially parallel to the relatively high impedance direction H. The other two sides are opposite to each other and substantially parallel to the relatively low impedance direction D. In one embodiment, a ratio between the impedance at the relatively high impedance direction H and the impedance at the relatively low impedance direction D of the carbon nanotube film is equal to or greater than 50 (e.g., in a range from 70 to 500). 
     The plurality of first driving-sensing electrodes  34  are spaced with each other and arranged in a row along the relatively high impedance direction H. More specifically, the plurality of first driving-sensing electrodes  34  are space arranged on at least one side of the first conductive film  32 , and the side is substantially perpendicular to the relatively low impedance direction D. In one embodiment, the plurality of first driving-sensing electrodes  34  are arranged on two opposite sides of the first conductive film  32 , and the two sides are substantially perpendicular to the relatively low impedance direction D. A length along the relatively high impedance direction H of each first driving-sensing electrode  34  can be between about 1 mm to about 8 mm. A distance between the two adjacent first driving-sensing electrodes  34  can be between about 3 mm to about 5 mm. The plurality of first driving-sensing electrodes  34  can be made of at least one a metal, a conductive polymer, and a carbon nanotube layer including a plurality of carbon nanotubes. A signal, input by each first driving-sensing electrode  34  to the first conductive film  32  or received from the first conductive film  32 , will transmit primarily along the relatively low impedance direction D. 
     The first capacitive touch sensor  30  further includes at least one first driving circuit  36  and at least one first sensing circuit  38  electrically connected with at least some of the plurality of first driving-sensing electrodes  34 . The at least one first driving circuit  36  inputs driving signals to the first conductive film  32  via the at least some of the plurality of first driving-sensing electrodes  34 . The at least one first sensing circuit  38  receives sensed signals via the at least some of the plurality of first driving-sensing electrodes  34 . The at least one first driving circuit  36  can include a plurality of first driving circuits  36 , and the at least one first sensing circuit  38  can include a plurality of first driving circuits  38 . In one embodiment, each of the plurality first driving-sensing electrodes  34  is electrically connected with one first driving circuit  36  and one first sensing circuit  38 . 
     The first capacitive touch sensor  30  as a touch sensor can realize multi-touch detection using only one conductive film. Other touch sensors with only one conductive film which can realize multi-touch detection can also be used in the capacitive touch panel  100 . In addition, the touch sensing module can also be a capacitive touch sensor including two conductive films. 
     The second capacitive touch sensor  40  is a pressure sensor for detecting pressure information acted on the capacitive touch panel  100 . Structures of the second capacitive touch sensor  40  and the first capacitive touch sensor  30  can be the same. The second capacitive touch sensor  40  can also include only one conductive film for sensing pressure. The pressure information can be detected by changes of self-capacitance sensed from the second conductive film  42  if the deformable insulating layer  50  is deformed. In one embodiment, the second capacitive touch sensor  40  includes a second conductive film  42  and a plurality of second driving-sensing electrodes  44  electrically connected with the second conductive film  42 . 
     The second conductive film  42  can be the same as the first conductive film  32 . In one embodiment, the second conductive film  42  is the anisotropic impedance layer. The relatively low impedance direction D of the second conductive film  42  is the same as that of the first conductive film  32 , and the relatively high impedance direction H of the second conductive film  42  is the same as that of the first conductive film  32 . In one embodiment, the relatively low impedance direction D of the second conductive film  42  is substantially perpendicular to the relatively high impedance direction H of the first conductive film  32 . The plurality of second driving-sensing electrodes  44  are spaced from each other and arranged in a row along the relatively high impedance direction H of the second conductive film  42 . More specifically, the plurality of second driving-sensing electrodes  44  are spaced and arranged on at least one side of the second conductive film  42 , and the side is substantially perpendicular to the relatively low impedance direction D. In one embodiment, the plurality of second driving-sensing electrodes  44  are arranged on two opposite sides of the second conductive film  42 , and the two sides are substantially perpendicular to the relatively low impedance direction D. 
     In one embodiment, the second conductive film  42  is a transparent and continuous conductive film. In one embodiment, a plurality of conductive belts constitute the second conductive film  42 , and the plurality of conductive belts are spaced from each other and extend substantially along a same direction. In one embodiment, the second conductive film  42  is a continuous isotropic impedance layer. Isotropic impedance means that the impedance of the second transparent conductive film  42  is substantially uniform everywhere. 
     The second capacitive touch sensor  40  further includes at least one second driving circuit  46  and at least one second sensing circuit  48  electrically connected with at least some of the plurality of second driving-sensing electrodes  44 . In one embodiment, each of the plurality second driving-sensing electrodes  44  is electrically connected with one second driving circuit  46  and one second sensing circuit  48 . The second driving circuit  46  is the same as the first driving circuit  36  and the second sensing circuit  48  is the same as the first sensing circuit  38 . 
     The first capacitive touch sensor  30  and the second capacitive touch sensor  40  work independently from each other. Therefore, touch positions and pressure information can be detected independently at the same time. 
     Referring to  FIGS. 1-4 , the deformable insulating layer  50  is disposed between the touch sensor and the pressure sensor. The deformable insulating layer  50  is deformable. The gap G changes with an external force applied on the deformable insulating layer  50 . The decreased distance causes a self-capacitance sensed from the second conductive film  42  varied. The varied self-capacitance reflects the pressure information. 
     The deformable insulating layer  50  can be deformed by the external force and can restore to its former condition when the force vanishes. A material of the deformable insulating layer  50  can be at least one of a gas, liquid, liquid crystal material, solid elastic material, and combinations thereof. The elastic material can be a gel, such as a silica gel or acrylic gel. The liquid can be an ester. The gas can be air, nitrogen, inert gases, or combinations thereof. Referring back to  FIG. 3 , in one embodiment, the material of the deformable insulating layer  50  is a gas, the capacitive touch panel  100  further includes a support frame  52  disposed between the first conductive film  32  and the second conductive film  42  and supports peripheries of the first conductive film  32  and the second conductive film  42  to form a hermetic air cavity. 
     Referring to  FIGS. 1-5 , one embodiment of a sensing method based on the capacitive touch panel  100  includes the following steps: 
     S 1 , locating touch positions using the first capacitive touch sensor  30 ; and 
     S 2 , sensing the pressure information using the second capacitive touch sensor  40 . 
     Referring to  FIG. 6 , the step S 1  further includes the following substeps: 
     S 11 , inputting a driving signal to each of the plurality of first driving-sensing electrodes  34  via the at least one first driving circuit  36 ; receiving a plurality of first sensing signal values from each of the plurality of first driving-sensing electrodes  34  via the at least one first sensing circuit  38 ; searching at least one relative maximum C 1  from the plurality of first sensing signal values and at least one first driving-sensing electrode  34  corresponding to the at least one relative maximum C 1 ; calculating a position coordinate of a touch point in the relatively high impedance direction H of the first conductive film  32  by analyzing a position of the at least one first driving-sensing electrode  34  corresponding to the at least one relative maximum; and 
     S 12 , calculating a position coordinate of the touch point in the relatively low impedance direction D according to the relative maximum C 1 . 
     In step S 11 , the plurality of first sensing signal values are capacitance variation values before and after touching the capacitive touch panel  100 . The plurality of first sensing signal values can be fitted as a first curve showing a dependence of the first sensing signal values on the position of the first driving-sensing electrodes  34 . If a multi-touch is applied on the capacitive touch panel  100 , more than one relative maximum can be present in the first curve. The position coordinate of every touch point can be calculated using substeps S 11 -S 12 . 
     Referring to  FIG. 7  and  FIG. 8 , the step S 11  further includes the following substeps: 
     S 111 , driving each of the plurality of first driving-sensing electrodes  34  by the driving signal and receiving a plurality of second sensing signal values from each of the plurality of first driving-sensing electrodes  34 , wherein when one of the plurality of first driving-sensing electrodes  34  is driven and sensed, the other first driving-sensing electrodes  34  are suspending or receiving the same driving signal; 
     S 112 , driving each of the plurality of first driving-sensing electrodes  34  by the driving signal and receiving a plurality of third sensing signal values from each of the plurality of first driving-sensing electrodes  34 , wherein when one of the plurality of first driving-sensing electrodes  34  is driven and sensed, the other first driving-sensing electrodes  34  are grounded; and 
     S 113 , fitting the plurality of first sensing signal values using the plurality of second sensing signal values and the plurality of third sensing signal values. 
     In substeps S 111  and S 112 , the plurality of first driving-sensing electrodes  34  can be orderly driven. The plurality of second sensing signal values can be fitted as a second curve showing a dependence of the second sensing signal values on the position of the first driving-sensing electrodes  34 . The plurality of third sensing signal values can be fitted as a third curve showing a dependence of the third sensing signal values on the position of the first driving-sensing electrodes  34 . The position coordinates of the touch point can be calculated based on the plurality of second sensing signal values (or the second curve) or the plurality of third sensing signal values (or the third curve). However, sometimes, touch errors can occur, whereby a detection precision of the position coordinates can be decreased only using the plurality of second sensing signal values or the plurality of third sensing signal values. The detection precision can be improved by fitting the plurality of first sensing signal values using the plurality of second sensing signal values and the plurality of third sensing signal values. In addition, the first curve can be fitted by the second curve and the third curve. 
     In substep S 113 , the second sensing signal value and the third sensing signal value sensed from the same first driving-sensing electrode  34  are defined as a sensing signal value pair. The fitting can be a weighted averaging process of the second sensing signal value and the third sensing signal value in each sensing signal value pair, to obtain the first sensing signal value for each first driving-sensing electrode  34 . 
     In step S 2 , when the pressure information is being sensed, the first capacitive touch sensor  30  can work or not work. 
     Referring to  FIG. 9 , the pressure information can be sensed by the following substeps: 
     S 21 , setting a pressure threshold C 0 , the pressure threshold C 0  reflecting if there is a pressure applied on the capacitive touch panel  100 ; 
     S 22 , inputting a driving signal to each of the plurality of second driving-sensing electrodes  44  via the at least one second driving circuit  46 , receiving a plurality of fourth sensing signal values from each of the plurality of second driving-sensing electrodes  44 , and searching at least one relative maximum C 2  from the plurality of fourth sensing values; and 
     S 23 , judging if there is pressure applied on the capacitive touch panel  100  by comparing the at least one relative maximum C 2  with the pressure threshold C 0 . 
     The pressure information can be detected by changes in the self-capacitance sensed from the second conductive film  42  when the deformable insulating layer  50  is deformed. The plurality of fourth sensing signal values are self-capacitance variation values during pressing the capacitive touch panel  100 . The self-capacitance variation value can be a self-capacitance value difference or a self-capacitance value ratio, in which the self-capacitance values are detected before and after pressing the capacitive touch panel  100 . The pressure information includes pressure values. The pressure information can further include pressure positions. 
     In substep S 21 , the pressure threshold C 0  is used to reflect whether there is a pressure applied on the capacitive touch panel  100 . The pressure threshold C 0  can be an exact value. If the self-capacitance variation value sensed from the second capacitive touch sensor  40  is larger than the pressure threshold C 0 , the pressure information is detected. If the self-capacitance variation value is smaller than or equal to the pressure threshold C 0 , no pressure information is detected. In addition, the pressure threshold C 0  can also be a self-capacitance variation value range. If the self-capacitance variation value is within the range, the pressure information is detected. Otherwise, no pressure information is detected. 
     In substep S 22 , the plurality of fourth sensing signal values can be fitted as a fourth curve showing a dependence of the fourth sensing signal values on the position of the second driving-sensing electrodes  44 . The plurality of fourth sensing signal values or the fourth curve can be used to reflect the pressure information. 
     In substep S 23 , if C 2 &lt;C 0 , no pressure information is detected, and a first function can be triggered. The first function can be doing nothing or showing that the pressure is too small. If C 2 &gt;C 0 , the pressure information is detected, and a second function can be triggered. 
     If the pressure information is detected, the pressure value reflecting the pressure information can be calculated. The self-capacitance variation value detected from the second capacitive touch sensor  40  can be used as or reflect the pressure value. In one embodiment, the pressure value is in direct proportion to the self-capacitance variation value. 
     The substep S 21  further includes a step of setting a plurality of pressure thresholds C 01 , C 02  . . . to reflect different pressure ratings, thereby to execute different functions. In one embodiment, C 0 &lt;C 01 &lt;C 02 , if C 0 &lt;C 2 &lt;C 01 , a light pressing is detected, the second function can be triggered. If C 01 &lt;C 2 &lt;C 02 , a medium strength pressing is detected, a third function can be triggered. If C 2 &gt;C 02 , a heavy strength pressing is detected, a fourth function can be triggered. The second function, third function, and fourth function can be some gestures, such as tuning the volume up or down, dragging icons or pictures, or displaying right-click context menu. 
     In step S 2 , the pressure position is the touch position of the touch point. Therefore, if the touch position is calculated by the first capacitive touch sensor  30 , only those second driving-sensing electrodes  44  corresponding to the touch position can be driven and sensed to obtain the at least one relative maximum C 2 . Therefore, the pressure information can be quickly fixed. 
     The capacitive touch panel  100  includes the touch sensor and the pressure sensor. The touch sensor is achieved by the first capacitive touch sensor  30 . The pressure sensor is achieved by the second capacitive touch sensor  40 . The touch position and the pressure information can be detected independently and at the same time. Structures of the second capacitive touch sensor  40  and the first capacitive touch sensor  30  can be the same. Therefore, the pressure sensor can also detect the touch position, and the detection precision of the pressure information by the pressure sensor can be increased. 
     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 present 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 present disclosure but do not restrict the scope of the present 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.