Patent Publication Number: US-2015059172-A1

Title: Method for making touch panel

Description:
This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Applications: Application No. 201310389706.7, filed on Sep. 2, 2013, in the China Intellectual Property Office, disclosures of which are incorporated herein by references. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates touch panels and method for making the same, particularly to a carbon nanotube based capacitance-type touch panel and method for making the same. 
     2. Description of Related Art 
     In recent years, various electronic apparatuses such as mobile phones, car navigation systems have advanced toward high performance and diversification. There is continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels in front of their display devices such as liquid crystal panels. A user of such electronic apparatus operates it by pressing a touch panel with a finger or a stylus while visually observing the display device through the touch panel. Thus a demand exists for such touch panels which superior in visibility and reliable in operation. Different types of touch panels, including a resistance-type, a capacitance-type, an infrared-type and a surface sound wave-type have been developed. 
     A conventional capacitance-type touch panel usually includes a first transparent conductive layer, an insulative substrate, and a second transparent conductive layer stacked with each other in that order. That is, the first transparent conductive layer and the second transparent conductive layer are located on opposite two surfaces of the insulative substrate. However, the insulative substrate is usually a glass plate or polymer plate with a relative high thickness, which cannot meet the requirement of lightweight and small thickness of electronic device development. Furthermore, in making process, it is difficult to form the first transparent conductive layer and the second transparent conductive layer on the same insulative substrate directly. Usually, the first transparent conductive layer and the second transparent conductive layer are formed on two different insulative substrates, and then the two different insulative substrates are bound together by an optically clear adhesive (OCA), however, the thickness of the touch panel is further increased. 
     What is needed, therefore, is to provide a touch panel and method for making the same which can overcome the short come described 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 flow chart of one embodiment of a method for making a touch panel. 
         FIG. 2  is a Scanning Electron Microscope (SEM) image of a carbon nanotube film. 
         FIG. 3  is a schematic view of one embodiment of a touch panel made by the method of  FIG. 1 . 
         FIG. 4  is a schematic, cross-sectional view, along a line IV-IV of  FIG. 3 . 
         FIG. 5  is a flow chart of the other one embodiment of a method for making a touch panel. 
         FIG. 6  is a schematic view of the other one embodiment of a touch panel made by the method of  FIG. 5 . 
         FIG. 7  is a schematic, cross-sectional view, along a line VII-VII of  FIG. 6 . 
     
    
    
     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. 
     References will now be made to the drawings to describe, in detail, various embodiments of the carbon nanotube based capacitance-type touch panel and method for making the same. 
     Referring to  FIG. 1 , a method of one embodiment for making the touch panels  10  comprises following steps: 
     step (S 10 ), forming a first patterned adhesive layer  12   a  on a surface of an insulative substrate  11 , wherein the first patterned adhesive layer  12   a  includes a plurality of first adhesive layers  12  spaced from each other; 
     step (S 11 ), forming a first carbon nanotube layer  13   a  on a surface of the first patterned adhesive layer  12   a;    
     step (S 12 ), pattering the first carbon nanotube layer  13   a  to obtain a plurality of first transparent conductive layers  13  spaced from each other and with each located on a surface of one of the plurality of first adhesive layers  12 ; 
     step (S 13 ), forming a second patterned adhesive layer  14   a  on the first patterned adhesive layer  12   a,  wherein the second patterned adhesive layer  14   a  includes a plurality of second adhesive layers  14  spaced from each other and with each to cover only part of one of the plurality of first transparent conductive layers  13  so that each of the plurality of first transparent conductive layers  13  has at least part exposed; 
     step (S 14 ), forming a second carbon nanotube layer  15   a  on a surface of the second patterned adhesive layer  14   a;    
     step (S 15 ), pattering the second carbon nanotube layer  15   a  to obtain a plurality of second transparent conductive layers  15  spaced from each other and with each corresponding to one of the plurality of first transparent conductive layers  13  and located on a surface of one of the plurality of second adhesive layers  14 ; and 
     step (S 16 ), forming a plurality of first electrodes  16  and a first conductive trace  17  corresponding to each of the plurality of first transparent conductive layers  13 ; and forming a plurality of second electrode  18  and a second conductive trace  19  corresponding to each of the plurality of second transparent conductive layers  15  contemporaneously. In step (S 10 ), the insulative substrate  11  can be flat or curved and configured to support other elements. The insulative substrate  11  can be transparent or opaque. The size and shape of the insulative substrate  11  can be selected according to need. In one embodiment, the thickness of the insulative substrate  11  is in a range from about 100 micrometers to about 500 micrometers. The insulative substrate  11  can be made of rigid materials such as glass, quartz, diamond, plastic or any other suitable material. The insulative substrate  11  can also be made of flexible materials such as polycarbonate (PC), polymethyl methacrylate acrylic (PMMA), polyimide (PI), polyethylene terephthalate (PET), polyethylene (PE), polyether polysulfones (PES), polyvinyl polychloride (PVC), benzocyclobutenes (BCB), polyesters, or acrylic resin. In one embodiment, the insulative substrate  11  is a flat PET plate with a thickness of 150 micrometers. 
     The first patterned adhesive layer  12   a  can be formed by spin-coating, spraying, or brushing. The first patterned adhesive layer  12   a  can be made by depositing using a mask directly. Also the first patterned adhesive layer  12   a  can be made by forming a continuous adhesive layer first, and then patterning the continuous adhesive layer by chemically etching or mechanically scraping. The first patterned adhesive layer  12   a  is used to fix the first carbon nanotube layer  13   a  on the insulative substrate  11 . The thickness of the first patterned adhesive layer  12   a  can be in a range from about 10 nanometers to about 10 micrometers, for example, from about 1 micrometer to about 2 micrometers. The first patterned adhesive layer  12   a  can be transparent or opaque. The first patterned adhesive layer  12   a  can be made of materials such as thermal plastic glue, thermosetting glue or UV (Ultraviolet Ray) glue, for example PVC or PMMA. In one embodiment, the insulative substrate  11  is a flat and flexible PET plate with a thickness of 150 micrometers, and a patterned UV glue layer with a thickness of 2 micrometers is formed on the surface of the insulative substrate  11  by screen printing with a mask. The shape and size of the first adhesive layer  12  can be the same or different, and can be selected according o need. 
     In step (S 11 ), the first carbon nanotube layer  13   a  is a free-standing carbon nanotube film with resistance anisotropy. Referring to  FIG. 2 , the carbon nanotube film is a substantially pure structure consisting of a plurality of carbon nanotubes, with few impurities and chemical functional groups. The carbon nanotube film is a free-standing structure. The term “free-standing structure” includes, but is not limited to, the property that the carbon nanotube film can sustain the weight of itself when it is hoisted by a portion thereof without any significant damage to its structural integrity. Thus, the carbon nanotube film can be suspended by two spaced supports. The majority of carbon nanotubes of the carbon nanotube film are joined end-to-end by van der Waals force therebetween so that the carbon nanotube film is a free-standing structure. The carbon nanotubes of the carbon nanotube film can be single-walled, double-walled, or multi-walled carbon nanotubes. The diameter of the single-walled carbon nanotubes can be in about 0.5 nm to about 50 nm. The diameter of the double-walled carbon nanotubes can be in about 1.0 nm to about 50 nm. The diameter of the multi-walled carbon nanotubes can be in about 1.5 nm to about 50 nm. 
     The carbon nanotubes of the carbon nanotube film are oriented along a preferred orientation. That is, the majority of carbon nanotubes of the carbon nanotube film are arranged to substantially extend along the same direction and in parallel with the surface of the carbon nanotube film. Each adjacent two of the majority of carbon nanotubes of the carbon nanotube film are joined end-to-end by van der Waals force therebetween along the extending direction. A minority of dispersed carbon nanotubes of the carbon nanotube film may be located and arranged randomly. However, the minority of dispersed carbon nanotubes have little effect on the properties of the carbon nanotube film and the arrangement of the majority of carbon nanotubes of the carbon nanotube film. The majority of carbon nanotubes of the carbon nanotube film are not absolutely form a direct line and extend along the axial direction, some of them may be curved and in contact with each other in microcosm. Some variations can occur in the carbon nanotube film. Because the electric conductivity of the carbon nanotubes along the axial direction is much better than the electric conductivity along the radial direction, and the majority of the carbon nanotubes of the carbon nanotube film are substantially arranged to extend along the same direction, the carbon nanotube film is conductivity anisotropy. 
     The carbon nanotube film can be made by the steps of: growing a carbon nanotube array on a wafer by chemical vapor deposition (CVD) method; and drawing the carbon nanotubes of the carbon nanotube array to from the carbon nanotube film. During the drawing step, the carbon nanotubes are joined end-to-end by van der Waals attractive force therebetween along the drawing direction. The carbon nanotube film has the smallest resistance along the drawing direction and the greatest resistance along a direction perpendicular to the drawing direction. Thus, the carbon nanotube film is resistance anisotropy. Furthermore, the carbon nanotube film can be etched or irradiated by laser. After being irradiated by laser, a plurality of parallel carbon nanotube conductive strings will be formed and the resistance anisotropy of the carbon nanotube film will not be damaged because the carbon nanotube substantially extending not along the drawing direction are removed by burning. Each carbon nanotube conductive string comprises a plurality of carbon nanotubes joined end-to-end by van der Waals attractive force. 
     In one embodiment, the carbon nanotube film includes a plurality of successively oriented carbon nanotube segments joined end-to-end by van der Waals attractive force therebetween. Each carbon nanotube segment includes a plurality of carbon nanotubes parallel to each other, and combined by van der Waals attractive force therebetween. The carbon nanotubes in the carbon nanotube film are oriented along a preferred orientation. 
     The free-standing carbon nanotube film can be drawn from a carbon nanotube array and then placed on the first patterned adhesive layer  12   a  directly to cover part or entire surface of the first patterned adhesive layer  12   a.  The carbon nanotube film can be infiltrated into the first patterned adhesive layer  12   a  after being placed on the first patterned adhesive layer  12   a.  In one embodiment, part of the carbon nanotube film is infiltrated into the first patterned adhesive layer  12   a,  and part of the carbon nanotube film is exposed through of the first patterned adhesive layer  12   a.  Furthermore, a step of pressing the carbon nanotube film can be performed after step (S 11 ) to allow more carbon nanotubes of the carbon nanotube film to infiltrate into the first patterned adhesive layer  12   a.  In one embodiment, a single carbon nanotube film is placed on the first patterned adhesive layer  12   a  with the carbon nanotubes substantially extending along the Y direction to form a plurality of first conductive channels on a first surface of the first patterned adhesive layer  12   a  along the Y direction. Each carbon nanotube of the carbon nanotube film has a first portion infiltrated into the first patterned adhesive layer  12   a  and a second portion exposed through of the first patterned adhesive layer  12   a.  Also, two or more than two carbon nanotube films can be placed on the first patterned adhesive layer  12   a  side by side to obtain a greater first carbon nanotube layer  13   a . Adjacent sides of the two or more than two carbon nanotube films can be between adjacent two rows or adjacent two columns of the plurality of first adhesive layers  12 . 
     Furthermore, the first patterned adhesive layer  12   a  is solidified to fix the first carbon nanotube layer  13   a . The method for solidifying the first patterned adhesive layer  12   a  depends on the material of the first patterned adhesive layer  12   a.  The thermoplastic first patterned adhesive layer  12   a  can be solidified by cooling, the thermosetting first patterned adhesive layer  12   a  can be solidified by heating, and the UV glue first patterned adhesive layer  12   a  can be solidified by irradiating with ultraviolet light. Because part of the first carbon nanotube layer  13   a  is infiltrated into the first patterned adhesive layer  12   a,  the first carbon nanotube layer  13   a  is fixed by the first patterned adhesive layer  12   a  during solidifying the first patterned adhesive layer  12   a.  In one embodiment, the first patterned adhesive layer  12   a  is a patterned UV glue layer and solidified by ultraviolet light irradiating for about 2 seconds to about 30 seconds, for example, irradiating for about 4 seconds. 
     In step (S 12 ), the first carbon nanotube layer  13   a  can be patterned by removing the part of the first carbon nanotube layer  13   a  that is suspended between adjacent two of the plurality of first adhesive layers  12 . The suspended part of the first carbon nanotube layer  13   a  is not fixed by the first patterned adhesive layer  12   a  and can be removed easily by a method such as stripping by an adhesive tape or peeling by a roller having an adhesive outer surface. The suspended carbon nanotube layer can be removed easily by the adhesive tape or the roller having an adhesive outer surface. The suspended carbon nanotube layer can also be removed by a method such as laser-beam etching, ion-beam etching, or electron-beam etching. In one embodiment, a laser beam is controlled by a computer to etch the first carbon nanotube layer  13   a  and remove both the suspended part of the first carbon nanotube layer  13   a  and the other part of the first carbon nanotube layer  13   a  that on the first adhesive layer  12 . Thus, the size of the first transparent conductive layers  13  is smaller than the size of the first adhesive layer  12 . 
     In step (S 13 ), the method for making the second patterned adhesive layer  14   a  is the same as the method for making the first patterned adhesive layer  12   a.  In one embodiment, the second adhesive layer  14  is an UV glue layer with a thickness of 15 micrometers. The size of each second adhesive layer  14  is smaller than the size of the first transparent conductive layer  13 . The width of each second adhesive layer  14  along the Y direction is smaller than the width of each first transparent conductive layer  13  along the Y direction. The carbon nanotubes of the first transparent conductive layer  13  form a plurality of conductive channels along the Y direction, and each of the plurality of conductive channels has at least part exposed. Each first transparent conductive layer  13  can have only one edge exposed from one side of the second adhesive layer  14 . 
     In step (S 14 ), the method for making the second carbon nanotube layer  15   a  and solidifying the second patterned adhesive layer  14   a  is the same as the method for making the first carbon nanotube layer  13   a  and solidifying the first patterned adhesive layer  12   a.  In one embodiment, a single carbon nanotube film is placed on part surface of the second patterned adhesive layer  14   a  with the carbon nanotubes substantially extending along the X direction. 
     In step (S 15 ), the method for patterning the second carbon nanotube layer  15   a  is the same as the method for patterning the first carbon nanotube layer  13   a . The step (S 16 ) of patterning the second carbon nanotube layer  15   a  and the step (S 13 ) of patterning the first carbon nanotube layer  13   a  can be performed at the same process. That is, patterning the first carbon nanotube layer  13   a  and the second carbon nanotube layer  15   a  simultaneously. In one embodiment, a laser beam is controlled by a computer to etch both the first carbon nanotube layer  13   a  and the second carbon nanotube layer  15   a  and remove redundant carbon nanotubes to obtain ten first transparent conductive layers  13  and ten second transparent conductive layers  15 . 
     In step (S 16 ), the plurality of first electrodes  16 , the first conductive trace  17 , the plurality of second electrodes  18  and the second conductive trace  19  can be made by the same process one time contemporaneously. The plurality of first electrodes  16 , the first conductive trace  17 , the plurality of second electrodes  18  and the second conductive trace  19  can be can be made of material such as metal, carbon nanotube, conductive silver paste, or transparent conductive oxide (TCO), and can be made by etching a metal film, etching an TCO film, or printing a conductive silver paste. The plurality of first electrodes  16  can be entirely formed on the surface of the first adhesive layer  12 , entirely formed on the surface of the first transparent conductive layer  13 , or have a part formed on the surface of the first adhesive layer  12  and the other part formed on the surface of the first transparent conductive layer  13 . The first conductive trace  17  is formed only on the surface of the first adhesive layer  12 . The plurality of second electrodes  18  can be entirely formed on the surface of the second adhesive layer  14 , entirely formed on the surface of the second transparent conductive layer  15 , or have a part formed on the surface of the second adhesive layer  14  and the other part formed on the surface of the second transparent conductive layer  15 . The second conductive trace  19  is formed only on the surface of the second adhesive layer  14 . 
     In one embodiment, the plurality of first electrodes  16 , the first conductive trace  17 , the plurality of second electrodes  18  and the second conductive trace  19  are made of conductive silver paste and made by screen printing conductive silver paste at the same process one time contemporaneously. The conductive silver paste can include about 50% to about 90% (by weight) of the metal powder, about 2% to about 10% (by weight) of the glass powder, and about 8% to about 40% (by weight) of the binder. At least part of each first electrode  16  is formed on the surface of the first transparent conductive layer  13  and at least part of each second electrode  18  is formed on the surface of the second transparent conductive layer  15 . Thus, the first electrode  16  and the second electrode  18  can permeate into the carbon nanotube film before backing and form a composite after backing. Because the carbon nanotube film has a plurality of gaps between the carbon nanotubes, the materials of the first electrode  16  and the second electrode  18  can permeate into the carbon nanotube film easily. The plurality of first electrodes  16  are located at one side of the first transparent conductive layer  13  and on a surface of the first adhesive layer  12 . The plurality of first electrodes  16  are located along the X direction and spaced from each other. The plurality of first electrodes  16  are electrically connected to the first transparent conductive layer  13 . The first conductive trace  17  is electrically connected to the plurality of first electrodes  16 . The plurality of second electrodes  18  are located at one side of the second transparent conductive layer  15  and on a surface of the second adhesive layer  14 . The plurality of second electrodes  18  are located along the Y direction and spaced from each other. The plurality of second electrodes  18  are electrically connected to the second transparent conductive layer  15 , and the second conductive trace  19  is electrically connected to the plurality of second electrodes  18 . A plurality of touch panels  10  are obtained after step (S 16 ). The plurality of touch panels  10  are joined together. 
     Furthermore, a step (S 17 ) of separating each of the plurality of touch panels  10  by cutting can be performed. The cutting can be performed by a laser beam or a mechanical device such as a blade. The blade can move along the row direction firstly and then along the column direction. Thus, the plurality of touch panels  10  are separated from each other. In one embodiment, ten touch panels  10  are obtained by cutting. 
     The number of the electrodes  16 ,  18  and the conductive traces  17 ,  19  are not limited to only three as shown in  FIG. 1 . 
     Referring to  FIGS. 3 and 4 , a capacitance-type multi touch panel  10  of one embodiment includes an insulative substrate  11 , a first adhesive layer  12  located on a surface of the insulative substrate  11 , a first transparent conductive layer  13  located on a surface of the first adhesive layer  12 , a second adhesive layer  14  located on a surface of the first transparent conductive layer  13 , a second transparent conductive layer  15  located on a surface of the second adhesive layer  14 , a plurality of first electrodes  16 , a first conductive trace  17 , a plurality of second electrode  18 , and a second conductive trace  19 . 
     The insulative substrate  11 , the first adhesive layer  12 , the first transparent conductive layer  13 , the second adhesive layer  14 , and the second transparent conductive layer  15  are stacked with each other in that order. That is, all the first adhesive layer  12 , the first transparent conductive layer  13 , the second adhesive layer  14 , and the second transparent conductive layer  15  are located on the same side of the insulative substrate  11 . Adjacent two of the insulative substrate  11 , the first adhesive layer  12 , the first transparent conductive layer  13 , the second adhesive layer  14 , and the second transparent conductive layer  15  are in contact with each other directly. That is, there is no other layer being located between the adjacent two of the insulative substrate  11 , the first adhesive layer  12 , the first transparent conductive layer  13 , the second adhesive layer  14 , and the second transparent conductive layer  15 . Thus, the touch panel  10  has a decreased thickness. The plurality of first electrodes  16  are located on at least one side of the first transparent conductive layer  13  and electrically connected with the first transparent conductive layer  13 . The plurality of first electrodes  16  are also electrically connected with a sensing circuit (not shown) via the first conductive trace  17 . The plurality of second electrodes  18  are located on at least one side of the second transparent conductive layer  15  and electrically connected with the second transparent conductive layer  15 . The plurality of second electrodes  18  are also electrically connected with a driving circuit (not shown) via the second conductive trace  19 . The sensing circuit and the driving circuit can be two printed circuit board (PCB) or integrated in the same PCB. 
     The second adhesive layer  14  only covers part of the first transparent conductive layer  13  so that the first transparent conductive layer  13  has at least part exposed, and also all the plurality of first electrodes  16  and the first conductive trace  17  are exposed. The plurality of first electrodes  16  are in contact with and electrically connected with the exposed part of the first transparent conductive layer  13 . The first transparent conductive layer  13  has at least part exposed includes that the size of the first transparent conductive layer  13  is greater than the size of the second adhesive layer  14 . For example, the second adhesive layer  14  is a continuous adhesive layer, and one edge of the first transparent conductive layer  13  is exposed from one side of the second adhesive layer  14 . Because the plurality of first electrodes  16  and the first conductive trace  17  not covered by the second adhesive layer  14 , the plurality of first electrodes  16 , the first conductive trace  17 , the plurality of second electrodes  18  and the second conductive trace  19  can be made by the same screen printing process once time. Thus, the method of making the touch panel  10  is simple and cost less. The size of the first transparent conductive layer  13  is greater than the size of the second transparent conductive layer  15 . The second transparent conductive layer  15  and the first transparent conductive layer  13  are only partially overlapped with each other. The overlapped part of the second transparent conductive layer  15  and the first transparent conductive layer  13  is defined as the view area of the touch panel  10 . The non-overlapped part of the second transparent conductive layer  15  and the first transparent conductive layer  13  is defined as the trace area of the touch panel  10 . 
     In one embodiment, all the shapes of the first adhesive layer  12 , the first transparent conductive layer  13 , the second adhesive layer  14 , and the second transparent conductive layer  15  are rectangular. The length of the second adhesive layer  14  along the Y direction is smaller that the length of the first transparent conductive layer  13  along the Y direction so that part of the first transparent conductive layer  13  is exposed. The width of the second transparent conductive layer  15  along the X direction can be greater than or equal to the width of the first transparent conductive layer  13   a  long the X direction. The length of the second transparent conductive layer  15  along the Y direction is smaller that the length of the first transparent conductive layer  13  along the Y direction. The width of the second adhesive layer  14  along the X direction is greater than the width of the first transparent conductive layer  13  along the X direction so that the part of the second adhesive layer  14  can be located in the trace area. Thus, the plurality of second electrodes  18  and the second conductive trace  19  can be located on the second adhesive layer  14 . The length of the first adhesive layer  12  along the Y direction is greater than the length of the second adhesive layer  14  along the Y direction so that part of the first adhesive layer  12  can be located in the trace area. Thus, the plurality of first electrodes  16  and the first conductive trace  17  an be located on first adhesive layer  12 . 
     Both the first adhesive layer  12  and the second adhesive layer  14  are a layer of solidified electrically insulating glue. The first adhesive layer  12  is used to fix the first transparent conductive layer  13  on the insulative substrate  11 . The second adhesive layer  14  is used to bind the first transparent conductive layer  13  and the second transparent conductive layer  15  with each other, and electrically insulate the first transparent conductive layer  13  and the second transparent conductive layer  15  from each other. Because the first transparent conductive layer  13  and the second transparent conductive layer  15  are electrically insulated from each other only by the second adhesive layer  14 , the second adhesive layer  14  should have a certain thickness. The thickness of the first adhesive layer  12  can be in a range from about 10 nanometers to about 10 micrometers, for example, from about 1 micrometer to about 2 micrometers. The thickness of the second adhesive layer  14  can be in a range from about 5 micrometers to about 50 micrometers, for example, from about 10 micrometers to about 20 micrometers. The first adhesive layer  12  and the second adhesive layer  14  can be transparent or opaque. The first adhesive layer  12  and the second adhesive layer  14  can be made of materials such as thermal plastic glue, thermosetting glue or UV (Ultraviolet Ray) glue, for example PVC or PMMA. In one embodiment, the first adhesive layer  12  is an UV glue layer with a thickness of 1.5 micrometers and the second adhesive layer  14  is an UV glue layer with a thickness of 15 micrometers. The second adhesive layer  14  covers all the first transparent conductive layer  13 , the plurality of first electrodes  16  and the first conductive trace  17 . 
     The solidified electrically insulating glue is different from the widely used insulative layer, such as a previously prepared glass plate, or previously prepared polymer sheet. Usually, the carbon nanotube film is attached on the previously prepared glass plate or polymer sheet, and the glass plate or polymer sheet with the carbon nanotube film thereon is bound with the insulative substrate  11  by OCA. However, it is easy to result a stress difference between the two different insulative substrates during bounding process, which will cause the insulative substrates to be twisted or curled. Furthermore, the previously prepared glass plate or polymer sheet usually has a thickness greater than 100 micrometers, which cause the thickness of the touch panel is increased. If the previously prepared glass plate or polymer sheet has a too small thickness, the difficulty of bounding will be increased greatly. The touch panel  10  only has the second adhesive layer  14  located between the first transparent conductive layer  13  and the second transparent conductive layer  15 , which allows the making process to be simplified, and the second adhesive layer  14  have smaller thickness. 
     Referring to  FIG. 5 , a method of one embodiment for making the touch panel  20  comprises following steps: 
     step (S 20 ), providing an insulative substrate  21  with a TCO layer  23   a  thereon; 
     step (S 21 ), patterning the TCO layer  23   a  to obtain a plurality of first transparent conductive layers  23  spaced from each other, wherein each of the plurality of first transparent conductive layers  13  is a patterned TCO layer; 
     step (S 22 ), forming a second patterned adhesive layer  24   a  on the insulative substrate  21 , wherein the second patterned adhesive layer  24   a  includes a plurality of second adhesive layers  24  spaced from each other and with each to cover only part of one of the plurality of first transparent conductive layers  23  so that each of the plurality of first transparent conductive layers  23  has at least part exposed; 
     step (S 23 ), forming a second carbon nanotube layer  25   a  on a surface of the second patterned adhesive layer  24   a;    
     step (S 24 ), pattering the second carbon nanotube layer  25   a  to obtain a plurality of second transparent conductive layers  25  spaced from each other and with each corresponding to one of the plurality of first transparent conductive layers  23  and located on one of the plurality of second adhesive layers  24 ; 
     step (S 25 ), forming a plurality of first electrodes  26  and a first conductive trace  27  corresponding to each of the plurality of first transparent conductive layers  23 ; and forming a plurality of second electrode  28  and a second conductive trace  29  corresponding to each of the plurality of second transparent conductive layers  25  contemporaneously; and 
     step (S 26 ), separating each of the plurality of touch panels  20  by cutting. 
     In step (S 20 ), the insulative substrate  21  is a glass plate with a thickness in a range from about 100 micrometers to about 300 micrometers. The TCO layer  23   a  defines a plurality of area  22 . The material of the TCO layer  23   a  can be indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), zinc oxide (ZnO) or tin oxide (TO). In one embodiment, TCO layer  23   a  is an ITO layer on an ITO glass. 
     In step (S 21 ), the TCO layer  23   a  is patterned by laser etching. Each first transparent conductive layer  23  is located in one of the plurality of area  22 . The first transparent conductive layer  23  includes a plurality of strap-shaped TCO layers spaced from and in parallel with each other. The plurality of strap-shaped TCO layers extend along the X direction. The pattern of the first transparent conductive layer  23  is not limited, as long as it can form a conductive film with resistance anisotropy. The thickness, width, and gaps of the plurality of strap-shaped TCO layers can be selected according to need. 
     Step (S 22 ) to step ( 26 ) are the same as the step (S 13 ) to step ( 17 ) above. Each of the plurality of strap-shaped TCO layers has one end exposed and electrically connected with one of the plurality of first electrodes  26 . 
     Because the first transparent conductive layer  23  is a patterned TCO layer, the touch panel  20  can omit the first electrodes  26 , and the first conductive trace  27  can be in contact with and electrically connected to the patterned TCO layer directly. That is, the plurality of first electrodes  26  and the first conductive trace  27  can be made during the process of laser etching the ITO layer in step (S 21 ). 
     Referring to  FIGS. 6 and 7 , a capacitance-type multi touch panel  20  of one embodiment includes an insulative substrate  21 , a first transparent conductive layer  23  located on a surface of the insulative substrate  21 , a second adhesive layer  24  located on a surface of the first transparent conductive layer  23 , a second transparent conductive layer  25  located on a surface of the second adhesive layer  24 , a plurality of first electrodes  26 , a first conductive trace  27 , a plurality of second electrode  28 , and a second conductive trace  29 . 
     The insulative substrate  21 , the first transparent conductive layer  23 , the second adhesive layer  24 , and the second transparent conductive layer  25  are stacked with each other in that order. That is, all the first transparent conductive layer  23 , the second adhesive layer  24 , and the second transparent conductive layer  25  are located on the same side of the insulative substrate  21 . The touch panel  20  is similar as the touch panel  10  except that the first transparent conductive layer  23  is a patterned TCO layer located on a surface of the insulative substrate  21  directly. That is, the touch panel  20  does not have any adhesive layer between the first transparent conductive layer  23  and the insulative substrate  21 . 
     The first transparent conductive layer  23  includes a plurality of strap-shaped TCO layers spaced from and in parallel with each other. The plurality of strap-shaped TCO layers extend along the X direction. The pattern of the first transparent conductive layer  23  is not limited, as long as it can form a conductive film with resistance anisotropy. The thickness, width, and gaps of the plurality of strap-shaped TCO layers can be selected according to need. The material of the TCO layer can be indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), zinc oxide (ZnO) or tin oxide (TO). In one embodiment, the first transparent conductive layer  23  includes a plurality of strap-shaped ITO layers with each electrically connected to one of the plurality of first electrodes  26 . 
     The second adhesive layer  24  is located on the insulative substrate  21  and covers the entire patterned TCO layer. Part of the second adhesive layer  24  permeates the gaps between the adjacent strap-shaped TCO layers. 
     Because the first transparent conductive layer  23  is a patterned TCO layer, the touch panel  20  can omit the first electrodes  26 . That is the first conductive trace  27  can be in contact with and electrically connected to the patterned TCO layer directly. 
     Because only the adhesive layer is located between the first transparent conductive layer and the second transparent conductive layer, the touch panel has small thickness, which can meet the requirement of lightweight and small thickness of electronic device development. The touch panel with such structure is easy to fabricate. Furthermore, there is no need to bound two different insulative substrates by an OCA, and the method of making the touch panel is simple and cost less. 
     It is to be understood that the above-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 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.