Patent Publication Number: US-2015062079-A1

Title: Method of locating a touch point and sensing a touch pressure on a touch device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201310387181.3, 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 a method of locating a touch point and sensing a touch pressure on a touch panel, particularly 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 the pressure on the contact areas. However, if hard touch conductors are used, the contact areas may be constant regardless of the amount of the force applied on the touch panels. Therefore, the pressure may not be measured accurately, and may trigger errors in operating the touch panels. 
     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 device. 
         FIG. 2  is an exploded view of the capacitive touch device. 
         FIG. 3  shows a schematic view of a driving and a sensing circuit in one embodiment of the capacitive touch device. 
         FIG. 4  is a flowchart of an embodiment of a method of locating a touch point and sensing a touch pressure on the capacitive touch device. 
         FIG. 5  is a schematic view of a simulation curves of the method of locating a touch point and sensing a touch pressure of  FIG. 4 . 
         FIG. 6  is a flowchart of another embodiment of a method of locating a touch point and sensing a touch pressure on the capacitive touch device. 
         FIG. 7  is a schematic view of a simulation curves of the method of locating a touch point and sensing a touch pressure of  FIG. 6 . 
         FIG. 8  is a flowchart of yet another one embodiment of a method of locating a touch point and sensing a touch pressure on the capacitive touch device. 
         FIG. 9  is a flowchart of yet another one embodiment of a method of locating a touch point and sensing a touch pressure on the capacitive touch device. 
     
    
    
     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  FIGS. 1-3 , a method of locating a touch point and sensing a touch pressure on a touch device  10  is provided. The touch device  10  includes a touch module  14  and a display module  16  spaced from each other. 
     The touch module  14  can be spaced from the display module  16  via a supporter or an insulating layer (not shown). The touch module  14  includes a substrate  102  and a first conductive film  104  on the substrate  102 . The first conductive film  104  is located on a first surface of the substrate  102  adjacent to the display module  16 . Furthermore, the first conductive film  104  can be transparent. 
     In one embodiment, the touch module  14  consists of the substrate  102 , the conductive film  104 , and the plurality of driving and sensing electrodes  106 . 
     The substrate  102  can be made of a flexible and transparent material. The material can be polyethylene, polycarbonate, polyethylene terephthalate, polyethylene terephthalate, polymethyl, or methacrylate. 
     The first conductive film  104  can be electrically anisotropic defining a low electrical impedance in a direction D and a high electrical impedance in a direction H. The plurality of first driving and sensing electrodes  106  are located on at least one of two opposite sides of the substrate  102  along the low impedance direction D. Each of the plurality of first driving and sensing electrodes  106  is electrically connected to a driving integrated circuit  120  and a sensing integrated circuit  130 . The driving integrated circuit  120  is configured to provide driving signals to the plurality of driving and sensing electrodes  106 . The sensing integrated circuit  130  is configured to read the signal values from the plurality of driving and sensing electrodes  106 . 
     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  104  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  104  can be at least one of carbon nanotubes, indium tin oxide, metal, and graphene. The first conductive film  104  can be a mesh which is transparent, electrical anisotropic, and made of the carbon nanotubes, indium tin oxide, metal, graphene, or combinations thereof. 
     The conductive film  104  can include a carbon nanotube film, and the carbon nanotube film can be drawn from a carbon nanotube array. 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). 
     Furthermore, a transparent protective film (not shown) can be located on the first conductive film  104 . A material of the transparent protective film can be silicon nitride, silicon oxide, styrene cyclobutene (BCB), acrylic resin, polyester or the like material. The transparent protective film can also be polyethylene terephthalate (PET) film for protecting the first conductive film  104 . 
     Furthermore, the touch module  14  can include another conductive film (not shown) located on a second surface of the substrate  102  opposites to the first surface. The conductive film on the second surface of the substrate  102  can be ITO. The two conductive films forms a capacitive touch sensor. 
     The display module  16  includes a second conductive film  161  spaced from the first conductive film  104 . The second conductive film  161  functions as an electrode of the display module  16  adjacent to the touch module  14 . Because the display module  16  is spaced from the touch module  14 , the second conductive film  161  is spaced from the first conductive film  104 . The first conductive film  104  and the second conductive film  161  forma capacitive touch sensor and function as a touch pressure sensing unit. In one embodiment, the display module  16  is a liquid crystal module (LCM). 
     Referring to  FIGS. 4-5 , a method of sensing the touch point and sensing a touch pressure of the touch device  10  includes following steps: 
     (S 11 ), obtaining a first value C 1  from one driving and sensing electrode  106  by driving and reading signals from the driving and sensing electrode  106  while grounding remaining driving and sensing electrodes  106 , and repeating until the first value C 1  is read from every driving and sensing electrode  106 ; 
     (S 12 ), obtaining a second value C 2  from one driving and sensing electrode  106  by driving and reading signals from the driving and sensing electrode while grounding remaining driving and sensing electrodes, and repeating until the second value C 2  is read from every driving and sensing electrode  106 ; and 
     (S 13 ), determining whether there is touch pressure by comparing the first value C 1  and the second value C 2 . 
     In step (S 11 ), the touch point on the touch device  10  is obtained by calculating the first values C 1  of the plurality of driving and sensing electrodes  106 . The first values C 1  can be obtained by driving and sensing the plurality of driving and sensing electrodes  106  one by one through the driving integrated circuit  120  and sensing integrated circuit  130 . 
     In one embodiment, the plurality of driving and sensing electrodes  106  are located on single side of the substrate  102 . In one embodiment, the plurality of driving and sensing electrodes  106  are located on the two opposite sides of the substrate  102 . The first values C 1  can be obtained by driving the plurality of the driving and sensing electrodes  106  one by one on a first side of the substrate  102 , and sensing the plurality of the driving and sensing electrodes  106  on a second side opposite to the first side of the substrate  102 . 
     In one embodiment, the plurality of first values C 1  can be capacity values sensed through the plurality of driving and sensing electrodes  106 . 
     In step (S 12 ), the second values C 2  are obtained by driving and sensing the plurality of driving and sensing electrodes  106  again. In one embodiment, the second values C 2  are capacity values detected through the plurality of driving and sensing electrodes  106 . In one embodiment, each one driving and sensing electrode  106  is driven, and while remaining of the driving and sensing electrodes  106  are grounded until every one of the driving and sensing electrodes are driven. The second values C 2  are obtained via the sensing integrated circuit  130 . 
     In step (S 13 ), the touch pressure can be detected by comparing the second values C 2  with the first values C 1  of each of the plurality of driving and sensing electrodes  106  one to one. When no touch pressure is applied on the touch module  14 , the distance between the first conductive film  104  and the second conductive film  161  may be unchanged, and the second values C 2  may be equal to the first values C 1 . When a touch pressure is applied on the touch module  14 , and the distance between the first conductive film  104  and the second conductive film  161  near the touch point is reduced. Since the second conductive film  161  is grounded or driven by a direct current voltage, the capacity of the first conductive film  104  is affected by the second conductive film  161 . Therefore, the second values C 2  may be greater than the first values C 1 . The greater the touch pressure, the smaller the distance, and greater the differences between the second values C 2  and the first values C 1 . 
     Furthermore, because the first conductive film  104  has impedance, current leakage occurs in the first conductive film  104  adjacent to the touch point. Thus touch pressure can be detected by comparing the second values C 2  with the first values C 1  obtained through some of the plurality of driving and sensing electrodes  106  near the touch point. As a result, an accuracy of the detecting touch pressure can be improved. 
     In one embodiment, the driving and sensing electrode  106  nearest to the touch point is numbered as a P electrode. The driving and sensing electrodes  106  number M electrodes away from the P electrode, wherein M&lt;N/2, and N is a total of the plurality of driving and sensing electrodes  106  can be selected to be sensed to determine the touch pressure. For example, if M=2, the touch pressure can be detected by comparing the second values C 2  and the first values C 1  of the driving and sensing electrodes  106  numbered P+1, P+2, P−1, or P−2. Furthermore, the touch pressure can also be detected by simultaneously comparing the second values C 2  and the first values C 1  of the driving and sensing electrodes  106  numbered P+1, P+2, P−1, and P−2 to improve accuracy. 
     The method of detecting a touch point and touch pressure has the following advantages. Since both the touch point and the touch pressure can be detected, and touch feedback can be provided by the detection of the touch pressure. Therefore, the touch device  10  may be suitable for game playing to enhance the realistic senses while playing the game. 
     Referring to  FIG. 6  and  FIG. 7 , a method of one embodiment of detecting the touch point and touch pressure on the touch device  10  includes following steps: 
     (S 21 ), obtaining a first value C 1  from one driving and sensing electrode  106  by driving and reading signals from the driving and sensing electrode  106  while grounding remaining driving and sensing electrodes  106 , and repeating until the first value C 1  is read from every driving and sensing electrode  106 ; 
     (S 22 ), obtaining a second value C 2  from one driving and sensing electrode  106  by driving and reading signals from the driving and sensing electrode  106  while grounding remaining driving and sensing electrodes  106 , and repeating until the second value C 2  is read from every driving and sensing electrode  106 ; 
     (S 23 ), calculating coordinates of a touch point on the touch device according to the first values C 1  and the second values C 2  from the driving and sensing electrodes; 
     (S 24 ), obtaining a third value C 3  from one driving and sensing electrode by driving and reading signals from the driving and sensing electrode while grounding remaining driving and sensing electrodes, and repeating until the third value C 3  is read from every driving and sensing electrode; and 
     (S 25 ), determining whether there is touch pressure by comparing the first value C 1  and the third value C 3 . 
     The touch point is sensed by comparing the first values C 1  and the second values C 2 , thus the unintended “ghost point” may be avoided. Therefore, the accuracy of locating a touch point can be improved. 
     The touch point can be determined by comparing the second values C 2  with the first values C 1 . When C 2 =C 1 , the touch point is intentional by a touching device. When C 2 &gt;C 1 , the touch point is unintentional. 
     As an example, in the Step (S 22 ), when there is a water droplet on the touch device  10 , the water droplet can be grounded through the grounded driving and sensing electrodes  106 , and the second values C 2  will be greater than the first values C 1 . When the touch device  10  is touched by a finger, because the finger has already been grounded during obtaining the first values C 1 , the second values C 2  will be equal to the first values C 1 . Therefore, the touch point caused by the finger or the water droplet can be distinguished. 
     Referring to  FIG. 8 , a method of locating a touch point and sensing a touch pressure includes following steps: 
     (S 31 ), presetting a threshold C 0 ; 
     (S 32 ), obtaining a first value C 1  from one driving and sensing electrode  106  by driving and reading signals from the driving and sensing electrode  106  while grounding remaining driving and sensing electrodes  106 , and repeating until the first value C 1  is read from every driving and sensing electrode  106 ; 
     (S 33 ), obtaining a second value C 2  from one driving and sensing electrode  106  by driving and reading signals from the driving and sensing electrode  106  while grounding remaining driving and sensing electrodes  106 , and repeating until the second value C 2  is read from every driving and sensing electrode  106 ; 
     (S 34 ), calculating a value ΔC wherein ΔC=|C 1 −C 2 |; and 
     (S 35 ), determining the touch pressure by comparing the plurality of difference values AC with the threshold C 0 . 
     The threshold C 0  can be preset according to the accuracy requirements of the touch device  10 . When the touch pressure F is weak, the change of distance d between the first conductive film  104  and the second conductive film  161  will be small. Thus the value AC will be small. Therefore, a proper threshold C 0  can be selected according to the accuracy requirements of sensing touch pressure. 
     In one embodiment, the threshold C 0  is defined as a difference between the first values C 1  and a plurality of values sensed by the driving and sensing electrodes  106  when a finger touches the touch panel but does not cause a change in distance between the first conductive film  104  and the second conductive film  161  of the touch module  14 . When the value ΔC is greater than the threshold value C 0 , the touch pressure can be sensed. While the value ΔC is smaller than the threshold value C 0 , a touch pressure may not be sensed. 
     Furthermore, the touch pressure F can be calculated by the value ΔC. The touch pressure F varies with the change of the distance Δd between the first conductive film  104  and the second conductive film  161 . Furthermore, Δd varies with the value ΔC. A relationship between the touch pressure F and value ΔC may be F∝ΔC, i.e., the greater the value ΔC, the greater the touch pressure F. Thus the touch pressure F can be calculated through the value ΔC. 
     Referring to  FIG. 9 , a method of locating a touch point and sensing a touch pressure includes following steps: 
     (S 41 ), presetting a threshold C 0 ; 
     (S 42 ) obtaining a first value C 1  from one driving and sensing electrode  106  by driving and reading signals from the driving and sensing electrode  106  while grounding remaining driving and sensing electrodes  106 ; and repeating until the first value C 1  is read from every driving and sensing electrode  106 ; 
     (S 43 ) obtaining a second value C 2  from one driving and sensing electrode  106  by driving and reading signals from the driving and sensing electrode  106  while grounding remaining driving and sensing electrodes  106 ; repeating until the second value C 2  is read from every driving and sensing electrode  106 ; 
     (S 44 ) calculating a value ΔC wherein ΔC=C 2 /C 1 ; and 
     (S 45 ) determining the touch pressure by comparing the plurality of ratio ΔC with the threshold C 0 . 
     The threshold value C 0  can be preset according to the accuracy requirements of the touch device  10 . While touch pressure F is weak, the change of distance Δd between the first conductive film  104  and the second conductive film  161  will be small. Thus the value ΔC will be small. Therefore, a proper threshold C 0  can be selected according to the accuracy requirements of the sensing touch pressure. 
     In one embodiment, the threshold value C 0  satisfies 1≦C 0 ≦2, for example, C 0 =1, 1.1, 1.2, or 1.5. While the ratio ΔC is greater than the threshold value C 0 , the touch pressure can be sensed. When the ratio ΔC is smaller than the threshold value C 0 , the touch pressure on the touch device  10  may not be sensed. 
     It is to be understood that the described embodiments are intended to illustrate rather than limit the disclosure. Any elements described in accordance with any embodiments is understood that they can be used in addition or substituted in other embodiments. Embodiments can also be used together. Variations may be made to the embodiments without departing from the spirit of the disclosure. The disclosure illustrates but does 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.