Patent Publication Number: US-8968506-B2

Title: Method for making touch panel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims all benefits accruing under 35 U.S.C. §119 from Taiwan Patent Application No. 100120175, filed on Jun. 9, 2011, in the Taiwan Intellectual Property Office, the contents of which are hereby incorporated by reference. This application is related to applications entitled, “TOUCH PANEL”, filed 2011 Dec. 29, with application Ser. No. 13/339,643; and “METHOD FOR MAKING TOUCH PANEL”, filed on 2011 Dec. 29, with application Ser. No. 13/339,658; and “METHOD FOR MAKING TOUCH PANEL”, filed on 2011 Dec. 29, with application Ser. No. 13/339,664; and “PATTERNED CONDUCTIVE ELEMENT”, filed on 2011 Dec. 29, with application Ser. No. 13/339,671; and “METHOD FOR MAKING TOUCH PANEL”, filed on 2011 Dec. 29, with application Ser. No. 13/339,681; and “METHOD FOR MAKING TOUCH PANEL”, filed on 2011 Dec. 29, with application Ser. No. 13/339,688; and “TOUCH PANEL”, filed on 2011 Dec. 29, with application Ser. No. 13/339,696; and “METHOD FOR MAKING PATTERNED CONDUCTIVE ELEMENT”, filed on 2011 Dec. 29, with application Ser. No. 13/339,700; and “METHOD FOR MAKING PATTERNED CONDUCTIVE ELEMENT”, filed on 2011 Dec. 29, with application Ser. No. 13/339,703; and “TOUCH PANEL”, filed on 2011 Dec. 29, with application Ser. No. 13/339,709; and “TOUCH PANEL”, filed on 2011 Dec. 29, with application Ser. No. 13/339,718. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to touch panels and method for making the same, particularly, to a carbon nanotube based touch panel and a 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. Due to a higher accuracy and a low-cost of the production, the resistance-type touch panels have been widely used. 
     A conventional resistance-type or capacitance-type touch panel includes a conductive indium tin oxide (ITO) layer as an optically transparent conductive layer. However, the ITO layer is generally formed by means of ion-beam sputtering and etched by laser beam, and the method is relatively complicated. Furthermore, the ITO layer has poor wearability, low chemical endurance and uneven resistance in an entire area of the panel. Additionally, the ITO layer has a relatively low transparency. All the above-mentioned problems of the ITO layer produce a touch panel with low sensitivity, accuracy, and brightness. 
     What is needed, therefore, is to provide a touch panel and a 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 schematic, top view of one embodiment of a touch panel. 
         FIG. 2  is a schematic, cross-sectional view, along a line II-II of  FIG. 1 . 
         FIG. 3  is a Scanning Electron Microscope (SEM) image of a carbon nanotube film. 
         FIG. 4  is a flowchart of one embodiment of a method for making a single touch panel. 
         FIG. 5  is a flowchart of one embodiment of a method for making a single touch panel. 
         FIG. 6  is a flowchart of one embodiment of a method for making a plurality of touch panels. 
         FIG. 7  is a schematic, top view of one embodiment of step (M 10 ) of  FIG. 6 . 
         FIG. 8  is a schematic, top view of one embodiment of step (M 20 ) of  FIG. 6 . 
         FIG. 9  is a schematic, top view of one embodiment of step (M 30 ) of  FIG. 6 . 
         FIG. 10  is a schematic, top view of one embodiment of step (M 40 ) of  FIG. 6 . 
         FIG. 11  is a schematic, top view of one embodiment of step (M 50 ) of  FIG. 6 . 
         FIG. 12  is a schematic, top view of one embodiment of step (M 60 ) 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 present touch panels and method for making the same. 
     Referring to  FIGS. 1 and 2 , a touch panel  10  of one embodiment includes a substrate  12 , an adhesive layer  13 , a transparent conductive layer  14 , at least one electrode  16 , and a conductive trace  18 . 
     The touch panel  10  defines two areas: a touch-view area  10 A and a trace area  10 B. The touch-view area  10 A is typically a center area of the touch panel  10  which can be touched and viewed to realize the control function. The trace area  10 B is usually a periphery area of the touch panel  10  which can be used to support the conductive trace  18 . The touch-view area  10 A has a relatively large area. The trace area  10 B is located on at least one side of the touch-view area  10 A. The positional relationship of the touch-view area  10 A and the trace area  10 B can be selected according to need. In one embodiment, the shape of the touch panel  10  is a rectangle, and the positional relationship of the touch-view area  10 A and the trace area  10 B is given as below. 
     For example, the trace area  10 B can be an annular region on the periphery, and the touch-view area  10 A is a square region on the center and surrounded by the trace area  10 B. For example, the trace area  10 B can be a strip-shaped region on one side of the touch panel  10 , and the touch-view area  10 A is rest of the touch panel  10  except the trace area  10 B. For example, the trace areas  10 B can be two strip-shaped regions on opposite sides of the touch panel  10 , and the touch-view area  10 A is the region between the trace areas  10 B. For example, the trace area  10 B can be an L-shaped region on adjacent two sides of the touch panel  10 , and the touch-view area  10 A is the rest of the touch panel  10  except the trace area  10 B. For example, the trace area  10 B can be a U-shaped region on three adjacent sides of the touch panel  10 , and the touch-view area  10 A is the rest of the touch panel  10  except the trace area  10 B. In one embodiment, the touch-view area  10 A is the center region having a shape the same as that is the shape of touch panel  10  and surrounded by the trace area  10 B. 
     The adhesive layer  13  is located on a surface of the substrate  12 . The transparent conductive layer  14  is located on a surface of the adhesive layer  13 . Both the adhesive layer  13  and the transparent conductive layer  14  are located only on the touch-view area  10 A. The electrode  16  and the conductive trace  18  are located on a surface of the substrate  12  and only on the trace area  10 B. Because the adhesive layer  13  is located only on the touch-view area  10 A and the electrode  16  and the conductive trace  18  are located only on the trace area  10 B, the electrode  16  and the conductive trace  18  can have a relative large thickness substantially same as the thickness of the adhesive layer  13 . The thickness of transparent conductive layer  14  is very small and can be omitted. 
     If the electrode  16  and the conductive trace  18  are located on the adhesive layer  13 , following problems will be caused. When the thickness of the electrode  16  and the conductive trace  18  is too small, the conductivity and durability of the electrode  16  and the conductive trace  18  will be low and short. When the thickness of the electrode  16  and the conductive trace  18  is too great, the surface of the touch panel  10  will be too rough. The electrode  16  and the conductive trace  18  can have the same thickness which is equal to the total thickness of the adhesive layer  13  and the transparent conductive layer  14 . The thickness of the electrode  16  and the conductive trace  18  can be in a range from about 1 micrometer to about 500 micrometers. In one embodiment, the thickness of the electrode  16  and the conductive trace  18  can be in a range from about 100 micrometers to about 200 micrometers. In one embodiment, the thickness of the electrode  16  and the conductive trace  18  can be in a range from about 1 micrometer to about 2 micrometers. In one embodiment, the thickness of the electrode  16  and the conductive trace  18  is about 1.5 micrometers. 
     Furthermore, because the transparent conductive layer  14  is located only on the touch-view area  10 A and the conductive trace  18  is located only on the trace area  10 B, the conductive trace  18  and the transparent conductive layer  14  do not overlap. Because the conductive trace  18  and the transparent conductive layer  14  have no overlapping part, no capacitance signal interference will be produced between the transparent conductive layer  14  and the conductive trace  18  when the touch-view area  10 A is touched by a finger or a stylus. Thus, the accuracy of the touch panel  10  is improved. 
     The electrode  16  is located on at least one side of the transparent conductive layer  14  and electrically connected with the transparent conductive layer  14  and the conductive trace  18 . The position of the electrode  16  depends on the work principle of the touch panel  10  and the detection methods of the touch-point. The number of the electrode  16  depends on the area and resolution of the touch panel  10 . In one embodiment, the touch panel  10  includes six electrodes  16  spaced from each other, arranged on one side of the transparent conductive layer  14 . The electrodes  16  can be made of material such as metal, carbon nanotube, conductive silver paste, or ITO. The electrodes  16  can be made by etching a metal film, etching an ITO film, or printing a conductive silver paste. The conductive trace  18  is electrically connected with an external circuit (not shown). The conductive trace  18  includes a plurality of conductive wires. The conductive trace  18  can be made of material such as metal, conductive silver paste, or ITO. The conductive trace  18  can be made by etching a metal film, etching an ITO film, or printing a conductive silver paste. In one embodiment, both the conductive trace  18  and the electrodes  16  are made of conductive silver paste and made by printing conductive silver paste concurrently. 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. 
     The substrate  12  can be flat or curved and configured to support other elements. The substrate  12  is insulative and transparent. The substrate  12  can be made of rigid materials such as glass, quartz, diamond, plastic or any other suitable material. The substrate  12  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 substrate  12  is a flat and flexible PET plate. 
     The transparent conductive layer  14  includes a carbon nanotube film. The carbon nanotube film includes a plurality of carbon nanotubes. The carbon nanotube film can be a substantially pure structure of the carbon nanotubes, with few impurities and chemical functional groups. A majority of the carbon nanotubes are arranged to extend along the direction substantially parallel to the surface of the carbon nanotube film. The carbon nanotubes in the carbon nanotube film can be single-walled, double-walled, or multi-walled carbon nanotubes. The length and diameter of the carbon nanotubes can be selected according to need, for example the diameter can be in a range from about 0.5 nanometers to about 50 nanometers and the length can be in a range from about 200 nanometers to about 900 nanometers. The thickness of the carbon nanotube film can be in a range from about 0.5 nanometers to about 100 micrometers, for example in a range from about 100 nanometers to about 200 nanometers. The carbon nanotube film has a good flexibility because of the good flexibility of the carbon nanotubes therein. 
     The carbon nanotubes of the carbon nanotube film can be arranged orderly to form an ordered carbon nanotube structure or disorderly to form a disordered carbon nanotube structure. The term ‘disordered carbon nanotube structure’ includes, but is not limited to, to a structure where the carbon nanotubes are arranged along many different directions, and the aligning directions of the carbon nanotubes are random. The number of the carbon nanotubes arranged along each different direction can be almost the same (e.g. uniformly disordered). The carbon nanotubes in the disordered carbon nanotube structure can be entangled with each other. The term ‘ordered carbon nanotube structure’ includes, but is not limited to, to a structure where the carbon nanotubes are arranged in a consistently systematic manner, e.g., the carbon nanotubes are arranged approximately along a same direction and/or have two or more sections within each of which the carbon nanotubes are arranged approximately along a same direction (different sections can have different directions). 
     In one embodiment, the carbon nanotube film is a free-standing structure. The term “free-standing structure” means 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 free-standing carbon nanotube film can be laid on the epitaxial growth surface  101  directly and easily. 
     In one embodiment, the transparent conductive layer  14  is a single carbon nanotube film. The carbon nanotube film includes a plurality of successive and oriented carbon nanotubes joined end-to-end by van der Waals attractive force therebetween. The carbon nanotube film is a free-standing film. Referring to  FIG. 3 , each 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. Some variations can occur in the carbon nanotube film. The carbon nanotubes in the carbon nanotube film are oriented along a preferred orientation. The carbon nanotube film can be treated with an organic solvent to increase the mechanical strength and toughness and reduce the coefficient of friction of the carbon nanotube film. A thickness of the carbon nanotube film can range from about 0.5 nanometers to about 100 micrometers. 
     The transparent conductive layer  14  can include at least two stacked carbon nanotube films. In other embodiments, the transparent conductive layer  14  can include two or more coplanar carbon nanotube films. Additionally, when the carbon nanotubes in the carbon nanotube film are aligned along one preferred orientation, an angle can exist between the orientations of carbon nanotubes in adjacent films, whether stacked or adjacent. Adjacent carbon nanotube films can be combined by only the van der Waals attractive force therebetween. An angle between the aligned directions of the carbon nanotubes in two adjacent carbon nanotube films can range from about 0 degrees to about 90 degrees. When the angle between the aligned directions of the carbon nanotubes in adjacent stacked carbon nanotube films is larger than 0 degrees, a plurality of micropores is defined by the carbon nanotube film. Stacking the carbon nanotube films will also add to the structural integrity of the carbon nanotube film. 
     The carbon nanotube film can be made by the steps of: growing a carbon nanotube array on a wafer by chemical vapor deposition 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. 
     The adhesive layer  13  is configured to fix the carbon nanotube film on the substrate  12 . Part of the carbon nanotubes of the carbon nanotube film are embedded in the adhesive layer  13  and part of the carbon nanotubes are exposed from the adhesive layer  13 . In one embodiment, most of the carbon nanotubes are embedded in the adhesive layer  13 . The adhesive layer  13  is transparent and can be made of materials such as hot plastic or UV (Ultraviolet Rays) glue, for example PVC or PMMA. The thickness of the adhesive layer  13  can be in a range from about 1 nanometer to about 500 micrometers, for example, the thickness is in a range from about 1 micrometer to about 2 micrometers. In one embodiment, the adhesive layer  13  is a UV glue layer with a thickness of 1.5 micrometers. 
     Referring to  FIG. 4 , a method for making the touch panel  10  of one embodiment includes the steps of: 
     step (S 10 ), providing a substrate  12 , wherein the substrate  12  defines two areas: a touch-view area  10 A and a trace area  10 B; 
     step (S 20 ), applying an adhesive layer  13  on a surface of the substrate  12 ; 
     step (S 30 ), placing a carbon nanotube film  19  on a surface of the adhesive layer  13 , and solidifying the adhesive layer  13  to fix the carbon nanotube film  19 ; 
     step (S 40 ), removing part of the carbon nanotube film  19  and the part of the adhesive layer  13  that are on the trace area  10 B to obtain a transparent conductive layer  14  and expose part of the substrate  12  that is on the trace area  10 B; and 
     step (S 50 ), forming an electrode  16  and a conductive trace  18  on the exposed part of the substrate  12  that is on the trace area  10 B. 
     In step (S 10 ), the substrate  12  is a flat glass plate. 
     In step (S 20 ), the adhesive layer  13  can be any adhesive which can be solidified on a certain condition. The adhesive layer  13  is transparent and can be made of materials such as hot plastic or UV glue, for example PVC or PMMA. The adhesive layer  13  can be formed by spin-coating, spraying, or brushing. In one embodiment, a UV glue layer with a thickness of 1.5 micrometers is formed on the substrate  12  by spin-coating. 
     In step (S 30 ), the carbon nanotube film  19  can be formed by transfer printing a preformed carbon nanotube film, filtering and depositing a carbon nanotube suspension, or laying a free-standing carbon nanotube film. In one embodiment, the carbon nanotube film  19  is drawn from a carbon nanotube array and then placed on the adhesive layer  13  directly. The carbon nanotube film  19  can be infiltrated into the adhesive layer  13  after being placed on the adhesive layer  13 . In one embodiment, part of the carbon nanotube film  19  is infiltrated into the adhesive layer  13 , and part of the carbon nanotube film  19  is exposed through of the adhesive layer  13 . Furthermore, a step of pressing the carbon nanotube film  19  can be performed after step (S 30 ) to allow more carbon nanotubes of the carbon nanotube film  19  to infiltrate into the adhesive layer  13 . 
     The method for solidifying the adhesive layer  13  depends on the material of the adhesive layer  13 . The thermoplastic adhesive layer  13  can be solidified by cooling, the thermosetting adhesive layer  13  can be solidified by heating, and the UV glue adhesive layer  13  can be solidified by irradiating with ultraviolet light. In one embodiment, because part of the carbon nanotube film  19  is infiltrated into the adhesive layer  13 , the carbon nanotube film  19  is fixed by the adhesive layer  13  during solidifying the adhesive layer  13 . In one embodiment, the adhesive layer  13  is 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 40 ), part of the carbon nanotube film  19  that is on the trace area  10 B and part of the adhesive layer  13  that is on the trace area  10 B are removed. The removing step can be performed by a method such as laser-beam etching, ion-beam etching, or electron-beam etching. In one embodiment, a laser beam  15  is controlled by a computer (not shown) to etch the part of the carbon nanotube film  19  and the part of the adhesive layer  13  that are on the trace area  10 B. The part of the carbon nanotube film  19  on the trace area  10 B is removed, and the part of the carbon nanotube film  19  on the touch-view area  10 A is maintained to form the transparent conductive layer  14 . 
     In step (S 50 ), the electrode  16  and the conductive trace  18  can be made by a method such as screen printing, chemical vapor deposition, or magnetron sputtering. In one embodiment, the electrode  16  and the conductive trace  18  are formed only on the trace area  10 B and have the same thickness which is equal to total thickness of the adhesive layer  13  and the transparent conductive layer  14 . The electrode  16  and the conductive trace  18  are formed concurrently by printing conductive silver paste. 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. 
     Furthermore, a step of planarizing the exposed part of the substrate  12  on the trace area  10 B can be performed before step (S 50 ), because the exposed part of the substrate  12  on the trace area  10 B will has a rough surface caused by etching. The step of planarizing can be performed by mechanical polishing or coating an insulating layer. The step of planarizing allows the exposed part of the substrate  12  on the trace area  10 B fit for printing conductive silver paste. 
     Furthermore, an optically clear adhesive (OCA) layer and a cover lens can be applied on the touch panel  10  to cover the transparent conductive layer  14 , the electrode  16 , and the conductive trace  18 . Thus, a touch screen is obtained. 
     Referring to  FIG. 5 , a method for making the touch panel  10  of another embodiment includes the steps of: 
     step (L 10 ), providing a substrate  12 , wherein the substrate  12  defines two areas: a touch-view area  10 A and a trace area  10 B; 
     step (L 20 ), forming a first mask layer  17  to cover the trace area  10 B; 
     step (L 30 ), applying an adhesive layer  13  on a surface of the substrate  12  and only on the touch-view area  10 A; 
     step (L 40 ), placing a carbon nanotube film  19  on the adhesive layer  13  and the first mask layer  17 ; 
     step (L 50 ), solidifying the adhesive layer  13  to fix the carbon nanotube film  19 ; 
     step (L 60 ), removing the first mask layer  17  and part of the carbon nanotube film  19  that on the trace area  10 B to obtain a transparent conductive layer  14  and expose part of the substrate  12  that on the trace area  10 B; and 
     step (L 70 ), forming an electrode  16  and a conductive trace  18  on the exposed part of the substrate  12  that is on the trace area  10 B. 
     In step (L 10 ), the substrate  12  is a flat and flexible PET plate. 
     In step (L 20 ), the first mask layer  17  is a free-standing structure that can be easily peeled off as a whole from the substrate  12 . The first mask layer  17  can be made of polymer such as PC, PMMA, PI, PET, PE, PES, PVC, BCB, polyesters, or acrylic resin. In one embodiment, the first mask layer  17  is a PET film frame with a thickness of about 1.5 micrometers. 
     In step (L 30 ), the adhesive layer  13  can be formed by spin-coating, spraying, or brushing. In one embodiment, a UV glue layer with a thickness of 1.5 micrometers is formed on the substrate  12  by spraying. Furthermore, a second mask layer (not shown) can be applied to cover the first mask layer  17  before applying the adhesive layer  13  and removed after applying the adhesive layer  13 . Thus, the adhesive layer  13  will not remain on the first mask layer  17 . In one embodiment, the shape and area of the second mask layer are same as that of the first mask layer  17 . The thickness of the second mask layer is less than that of the first mask layer  17 . 
     In step (L 40 ), the carbon nanotube film  19  can be formed by transfer printing a preformed carbon nanotube film, filtering and depositing a carbon nanotube suspension, or laying a free-standing carbon nanotube film. In one embodiment, the carbon nanotube film  19  is drawn from a carbon nanotube array and then placed on the adhesive layer  13  and the first mask layer  17  directly. The carbon nanotube film  19  on the touch-view area  10 A can be infiltrated into the adhesive layer  13 . In one embodiment, part of the carbon nanotube film  19  is infiltrated into the adhesive layer  13 , and part of the carbon nanotube film  19  is exposed through of the adhesive layer  13 . The carbon nanotube film  19  on the trace area  10 B is only located on and connected with the first mask layer  17  by van der Waals attractive force. 
     In step (L 50 ), the method for solidifying the adhesive layer  13  depends on the material of the adhesive layer  13 . Because part of the carbon nanotube film  19  is infiltrated into the adhesive layer  13 , the carbon nanotube film  19  is fixed by the adhesive layer  13  during solidifying the adhesive layer  13 . In one embodiment, the adhesive layer  13  is 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 (L 60 ), the entire first mask layer  17  is peeled off as a whole from the substrate  12 . The part of the carbon nanotube film  19  on the trace area  10 B is removed together with the first mask layer  17 . The part of carbon nanotube film  19  that is on the touch-view area  10 A is fixed on the substrate  12  by the adhesive layer  13  to form the transparent conductive layer  14 . Because the transparent conductive layer  14  is fabricated easily by removing the first mask layer  17 , the efficiency of making touch panel  10  is improved. The first mask layer  17  can be recycled and the cost of the touch panel  10  is decreased. 
     In step (L 70 ), the electrode  16  and the conductive trace  18  can be made by a method such as screen printing, chemical vapor deposition, or magnetron sputtering. In one embodiment, the electrode  16  and the conductive trace  18  are formed concurrently by printing conductive silver paste. 
     Referring to  FIG. 6 , a method for making a plurality of touch panels  10  of one embodiment includes the steps of: 
     step (M 10 ), providing a substrate  12  having a surface defining a plurality of target areas  120 , each target area  120  including two areas: a touch-view area  10 A and a trace area  10 B; 
     step (M 20 ), forming a first mask layer  17  to cover the trace area  10 B of each target area  120 ; 
     step (M 30 ), forming an adhesive layer  13  on the touch-view area  10 A of each target area  120 ; 
     step (M 40 ), forming a carbon nanotube film  19  on all the adhesive layers  13  and all the first mask layers  17 , and solidifying the adhesive layers  13  to fix the carbon nanotube film  19 ; 
     step (M 50 ), removing the first mask layer  17  and part of the carbon nanotube film  19  on the trace areas  10 B to obtain a plurality of transparent conductive layers  14  spaced from each other and expose parts of the substrate  12  that are on the trace areas  10 B; 
     step (M 60 ), forming an electrode  16  and a conductive trace  18  on the exposed part of the substrate  12  that on the trace area  10 B of each target area  120 ; and 
     step (M 70 ), cutting and obtaining a plurality of touch panels  10 . 
     In step (M 10 ), the shape and size of the target areas  120  can be selected according to need. Referring to  FIG. 7 , in one embodiment, the surface of the substrate  12  is divided into nine target areas  120  arranged in an array of three rows and three columns by four cutting lines  121 . The target areas  120  have the same shape and size. The touch-view area  10 A is typically a center area of the touch panel  10  which can be touched and viewed to realize the control function. The trace area  10 B is usually a periphery area of the touch panel  10  which can be used to support the conductive trace  18 . The touch-view area  10 A has a relatively large area. The trace area  10 B is located on at least one side of the touch-view area  10 A. The positional relationship of the touch-view area  10 A and the trace area  10 B can be selected according to need. In one embodiment, the shape of the touch panel  10  is a rectangle, the touch-view area  10 A is the center region having a shape the same as that is the shape of touch panel  10  and surrounded by the trace area  10 B. 
     In step (M 20 ), the first mask layer  17  covers all the trace areas  10 B of the substrate  12  as shown in  FIG. 8 . In one embodiment, the first mask layer  17  is a single PET film with a thickness of about 1.5 micrometers and defining a plurality of square openings. 
     In step (M 30 ), the adhesive layer  13  can be formed by spin-coating, spraying, or brushing. In one embodiment, the substrate  12  is a PET film. The adhesive layer  13  is an UV glue layer with a thickness of 1.5 micrometers and formed on the substrate  12  by spraying. Furthermore, a second mask layer (not shown) can be applied to cover the first mask layer  17  before applying the adhesive layer  13  and removed after applying the adhesive layer  13 . Thus, the adhesive layer  13  will not remain on the first mask layer  17  as shown in  FIG. 9 . 
     In step (M 40 ), the carbon nanotube film  19  can be formed by transfer printing a preformed carbon nanotube film, filtering and depositing a carbon nanotube suspension, or laying a free-standing carbon nanotube film. The carbon nanotube film  19  can cover the entire substrate  12  as shown in  FIG. 10 . When the width of the free-standing carbon nanotube film is less than the width of the substrate  12 , a plurality of free-standing carbon nanotube films can be coplanarly placed on the adhesive layer  13  and the first mask layer  17  side by side. Each two contacting sides of each two adjacent free-standing carbon nanotube films can be overlapped with the cutting lines  121  between two adjacent target areas  120 . 
     The method for solidifying the adhesive layer  13  depends on the material of the adhesive layer  13 . In one embodiment, the adhesive layer  13  is UV glue layer and solidified by ultraviolet light irradiating for about 4 seconds. 
     In step (M 50 ), the entire first mask layer  17  is peeled off from the substrate  12  as a whole. The parts of the carbon nanotube film  19  on the trace areas  10 B are removed together with the first mask layer  17 . The parts of the carbon nanotube film  19  on the touch-view areas  10 A are fixed on the substrate  12  to form the plurality of transparent conductive layers  14  spaced from each other as shown in  FIG. 11 . 
     In step (M 60 ), the electrode  16  and the conductive trace  18  can be made of material such as metal, carbon nanotube, conductive silver paste, or ITO and made by etching a metal film, etching an ITO film, or printing a conductive silver paste. Referring to  FIG. 12 , in one embodiment, all the electrodes  16  and the conductive traces  18  are formed concurrently by printing conductive silver paste. 
     In step (M 70 ), the step of cutting can be performed by a laser beam or a mechanical device such as a blade. In one embodiment, the target areas  120  of the substrate  12  are cut and separated from each other by blade from the cutting lines  121 . The blade can move along the row direction firstly and then along the column direction. Thus, the plurality of touch panels  10  is obtained. 
     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.