Abstract:
A touch panel and a method for fabricating the touch panel are presented. The touch panel includes a panel and a conductive border. A touch circuit is formed on a first side of the panel. A conductive border is formed on a circumference of the first side along the touch circuit. A method for fabricating the touch panel is further presented. The touch circuit of the touch panel is integrated onto the panel, so as to reduce the number of substrates that need to be bonded, thereby avoiding problems caused by substrate bonding and effectively decreasing the overall thickness of the touch panel.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a touch panel, and more particularly to a capacitive touch panel. 
     DESCRIPTION OF THE PRIOR ART 
       FIG. 1A  shows a conventional capacitive touch panel  100 . In addition to a liquid crystal and a color filter, at least an extra glass substrate  101  is needed for a touch circuit. Indium tin oxide (ITO)  102 ,  103  serving as a sensing unit and a driving unit are provided at two sides of the glass substrate. The upper layer ITO  102  and the lower layer ITO  103  are perpendicularly arranged. Ultraviolet (UV) film optical glue  105  is arranged between the glass substrate  101  and the panel  104 . The glass substrate  101  and the panel  104  are then bonded in a vacuum manner.  FIG. 1B  is a sectional view of the conventional capacitive touch panel. 
     The popularity of light weight, compact electronic devices drives industrial demand for ever-smaller, lighter and thinner components. However, potential reductions in the thickness of conventional touch panels are constrained by the fact that the panel substrates and the touch circuit are independent from each other. 
     In addition, the potential for particulate contamination of each substrate may lead to formation of bubbles in the substrate bonding and adversely affect alignment thereof, affecting yield. Moreover, bonding complexity increases in accordance with the size of the contact area. Therefore, there is urgent need for a structure and a process capable of reducing the required number of substrates in the touch panel. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a touch panel and a method for fabricating the same, in which a touch circuit of the touch panel is integrated onto a panel, so as to reduce the number of substrates that need to be bonded, thereby effectively avoiding problems caused by substrate bonding and decreasing the overall thickness of the touch panel. 
     In an embodiment, the present invention provides a touch panel, which includes a panel and a conductive border. A touch circuit is formed on a first side of the panel. The conductive border is formed on a circumference of the first side along the touch circuit. 
     In another embodiment, the present invention provides a method for forming a touch panel which includes the following steps. ITO pre-formed on a first side of a panel is patterned through laser imprinting, so as to form a touch circuit. A first conductive material is printed onto a circumference of the first side of the panel along the touch circuit, so as to form a conductive border. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a conventional capacitive touch panel; 
         FIG. 1B  is a sectional view of a conventional capacitive touch panel; 
         FIG. 2  shows a touch panel according to an embodiment of the present invention; 
         FIG. 3  shows a touch panel according to another embodiment of the present invention; 
         FIG. 4  shows a touch panel according to another embodiment of the present invention; 
         FIG. 5  is a schematic view of a touch panel coupled with a flexible circuit according to another embodiment of the present invention; 
         FIG. 6  shows a touch panel according to another embodiment of the present invention; 
         FIGS. 7A to 7C  show a method for forming a touch panel according to the present invention; 
         FIGS. 8A to 8F  show a method for forming a touch circuit part of a touch panel according to the present invention; 
         FIGS. 9A to 9E  show a method for forming parts of a conductive border and a frame of a touch panel according to the present invention; 
         FIG. 10  shows a touch panel according to another embodiment of the present invention; 
         FIGS. 11A to 11C  show a method for forming a touch panel according to the present invention; and 
         FIGS. 12A to 12C  show a touch panel according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  shows a touch panel  200  according to the present invention, which includes a touch circuit  201  formed on a first side of a panel  203 , and a conductive border  202  formed on a circumference of the first side along the touch circuit  201 . In a common application, the first side of the panel  203  faces an inner side of the electronic device; that is, faces a liquid crystal and a color filter, or other display elements. 
     In a preferred embodiment, the panel  203  is formed of glass, plastic (for example, polyethylene terephthalate (PET)), or other optical transparent substrates, and has optical characteristics and a function of protecting the touch circuit. 
     In another preferred embodiment, a conductive border  202  of the touch panel  200  is printed on the first side of the panel  203  with a non-transparent conductive ink. The non-transparent conductive ink includes conductive carbon, conductive carbide, or silver colloid, and is formed on the first side of the panel  203  in a screen-printing or jet-printing manner. A conductive wire is formed within the conductive border  202 , so as to transmit signals generated by the touch circuit. 
     In another preferred embodiment, the touch circuit  201  of the touch panel  200  includes a sensing unit, a driving unit, and an interconnection circuit therebetween (inside the sensing unit, inside the driving unit, and between the sensing unit, the driving unit, and an external controller). In another embodiment, the sensing unit, the driving unit, and the interconnection circuit therebetween are formed by patterning ITO pre-formed on the first side of the panel  203  through laser imprinting. 
       FIG. 3  shows another touch panel  300  according to an embodiment. A touch circuit  301  and a conductive border  302  are formed on a first side of a panel  303  of the touch panel  300 , and a recess  304  is formed on a periphery of a second side of the panel  303 . The recess  304  may be designed to connect signals of the touch circuit  301  to an external controller. 
       FIG. 4  shows another touch panel  400  according to an embodiment, which includes a controller  407  outside a touch circuit  401 . In a preferred embodiment, the touch panel  400  has a flexible circuit  406  arranged between the touch circuit  401  and the controller  407 , so as to transmit control signals and touch signals between the touch circuit  401  and the controller  407 . 
     Referring to  FIG. 5 , apertures  508  are formed in a frame  502  of a touch panel  500 , and a conductive material is printed in the apertures  508  through jet-printing, so as to form conductive pads  509 . The conductive pads  509  may also be a product label or other aesthetic designs, and the flexible circuit  506  can be coupled through the conductive pads  509 , so that the touch circuit  501  of the touch panel  500  is coupled to an external controller through the flexible circuit  506 . 
       FIG. 6  shows another touch panel  600  according to the present invention, which has a touch circuit  601  formed on a first side of a panel  603 . In addition, a conductive border  602  and a frame  604  are also formed on the first side of the panel  603 , and the frame  604  encircles the conductive border  602 . 
     In a preferred embodiment, the frame  604  of the touch panel  600  is formed of an insulating material through screen-printing or jet-printing. The insulating material is a black or non-transparent ink, and the conductive border  602  is formed of the non-transparent conductive ink through screen-printing or jet-printing. The touch circuit  601  includes a sensing unit, a driving unit, and an interconnection circuit therebetween, which are formed by patterning ITO pre-formed on the first side of the panel  603  through laser imprinting. The first side of the panel  603  faces an inner side of the electronic device, that is, faces a liquid crystal and a color filter, or other display elements. 
       FIG. 7  shows a method for forming a touch panel according to the present invention. As shown in  FIGS. 7A to 7B , ITO pre-formed on a first side of a touch panel  700  is patterned through laser imprinting, so as to form a touch circuit  701 . In  FIG. 7C , a conductive material is printed onto a circumference of the first side of the touch panel  700  along the touch circuit  701 , so as to form a conductive border  702 . 
       FIGS. 8A to 8F  show the formation of a touch circuit part of a touch panel according to another embodiment of the present invention. In  FIG. 8A , a substrate is provided, which may be glass, plastic, or other optical transparent substrates. In  FIG. 8B , a layer of ITO is formed on the substrate. In  FIG. 8C , a touch circuit  801  is formed by laser imprinting. The touch circuit includes a sensing unit, a driving unit, and an interconnection circuit therebetween. In  FIG. 8D , an optical coating layer is further formed on the touch circuit  801 . The optical coating layer may be formed by applying an insulating material on the touch circuit  801  through rolling or spin coating. In a preferred embodiment, the optical coating layer may be poly(methyl methacrylate) (PMMA) or a photoresist material, so that the optical coating layer serves as an insulation layer  8011  in the touch circuit. 
     In  FIG. 8E , the insulation layer  8011  is further patterned through laser imprinting, and at the same time the lower layer of ITO is also patterned to form through holes. In  FIG. 8F , a conductive ink is jet-printed into the through holes, so as to form an interconnection circuit  8012  in the touch circuit. The conductive ink that forms the interconnection circuit  8012  may include a conductive polymer or other nano-metal-containing particles, such as poly(3,4-ethylenedioxythiophene) (PEDOT), nano-gold, and nano-silver. 
     In an embodiment, in  FIG. 8F , the thickness of the ITO  801  pre-formed on the substrate is about 20 nm. The thickness of the insulation layer  8011  is about 1.5 μm. The thickness of the PEDOT that forms the interconnection circuit  8012  is about 600 nm. The size of an area of the interconnection circuit formed by the PEDOT is about 800 μm long and 300 μm wide. The size of an interconnection area inside an area of the interconnection circuit is about 200 μm long and 10 μm wide. In addition, an insulation layer having the thickness of about 1.5 μm is further coated on the uppermost layer of the touch circuit, and the insulation layer may be an optical coating layer, so as to protect the touch circuit. 
       FIGS. 9A to 9E  show parts of a conductive border and a frame of a touch panel according to another embodiment of the present invention. In  FIG. 9A , a transparent substrate is provided. ITO  901  is pre-formed on a side of the substrate, so as to pattern the ITO layer through laser imprinting. In  FIG. 9B , a frame  904  is formed on the patterned ITO  901 . In a preferred embodiment, the frame  904  is formed by printing a non-transparent ink onto the patterned ITO  901  through screen-printing, and is disposed at an outer edge of the substrate. In another preferred embodiment, the non-transparent ink that forms the frame  904  is an insulating material. 
     In  FIG. 9C , a conductive border  902  is formed on the patterned ITO  901  within the range of the frame  904 , so that the frame  904  is arranged on a peripheral of the conductive border  902 . In a preferred embodiment, the ink that forms the conductive border  902  may include conductive carbon. 
     In  FIG. 9D , the conductive ink is further printed on the conductive border  902  and the frame  904  through jet-printing to form metal leads  905 , so as to transmit signals of a touch circuit inside the touch panel. In a preferred embodiment, the material of the metal leads includes silver. 
     In  FIG. 9E , the insulating material is further applied to cover the metal leads, so as to protect the metal leads for transmitting signals. The insulating material is the same as the insulating material that forms the frame  904 . 
     In an embodiment, the size of an area of the conductive frame is about 2300 μm long and 300 μm wide, the width of the metal lead is about 70 μm, and the spacing between the metal leads is about 130 μm. 
       FIG. 10  shows a preferred embodiment of the present invention. In this embodiment, a method of the present invention is adopted to form a touch panel  1000 , which includes a touch circuit  1001 , a conductive border  1002 , a frame  1004 , and metal leads  1005 . The method is the same as that in  FIGS. 9A to 9E , and the details will be omitted herein. 
       FIGS. 11A to 11C  further show the formation of a touch panel according to another embodiment of the present invention. In  FIG. 11A , ITO pre-formed on a first side of a substrate is patterned to form a touch circuit  1101 . A non-transparent insulating material is printed at edges of the substrate through screen-printing on a peripheral of the touch circuit  1101  so as to form a frame  1104 , and a conductive border  1102  is formed within the range of the frame  1104 . 
     In another preferred embodiment of the present invention, a conductive material is printed on the conductive border  1102  and the frame  1104  to form metal leads  1105 , so as to transmit signals of the touch circuit inside the touch panel. In a preferred embodiment, the material of the metal leads includes silver. 
     In another embodiment of the present invention, peelable glue is printed inside the touch circuit area, an insulating material is further applied on the touch circuit  1101  to form an insulation layer  1106  inside the touch circuit  1101 , and the insulation layer  1106  covers the metal leads  1105 , so as to protect the metal leads. In a preferred embodiment, the insulating material may be silica through PVD evaporation or a printed optical coating layer. As shown in  FIG. 11B , the peelable glue is removed to pattern the insulation layer  1106 . 
       FIG. 11C  shows another embodiment of the present invention, in which peelable glue is further printed on the insulation layer  1106  of the touch circuit  1101 , ITO is formed by evaporation on the insulation layer  1106 , and then the peelable glue is removed, so that the evaporated ITO forms an interconnection circuit  1107  in the touch circuit. 
     In an embodiment, for the touch panel as shown in  FIG. 11 , the thickness of the ITO pre-formed on the substrate is about 20 nm, the thickness of the insulation layer  1106  is about 1.5 μm, and the thickness of the ITO that forms the interconnection circuit  1107  in the touch circuit is about 40 nm. The width of the metal lead is about 70 μm and the spacing between the metal leads is about 130 μm. The size of an area of the conductive frame is about 2300 μm long and 300 μm wide, and the size of the area may be smaller. The size of an area of the ITO interconnection circuit is about 800 μm long and 300 μm wide, and the size of an sub-interconnection area inside the area is about 200 μm long and 10 μm wide. In addition, an insulation layer having a thickness of about 1.5 μm is further coated on the uppermost layer of the touch circuit, and the insulation layer may be an optical coating layer, so as to protect the touch circuit. 
     In still another preferred embodiment of the present invention, a simple touch panel is formed. As shown in  FIG. 12A , a substrate pre-formed with ITO is imprinted with a laser, so as to form a plurality of sensing areas  1201 , and a conductive border  1202  is formed on a peripheral of the sensing areas  1201 . In  FIG. 12A , a controller outside the touch panel can be externally connected through a flexible circuit  1203  at a rear side of the touch panel. In  FIG. 12C , the simple touch panel may display signals at a plurality of different touch positions. Taking the touch panel in  FIGS. 12A and 12C  as an example, four sensing areas are divided, so that signals of up to nine touch positions  1205  can be processed. 
     An extra substrate is not needed for the touch panel of the present invention, as the touch circuit is already directly formed below the panel. Therefore, the number of substrates is reduced and the thickness of the touch panel is further diminished. Moreover, the assembly process is simplified and manufacturing cost is reduced, so that yield is enhanced. 
     Although the technical solutions and features of the present invention are described above, persons skilled in the art can still make various variations and modifications without departing from the teachings and contents disclosed by the present invention. Thus, the scope of the present invention is not limited to the disclosed embodiments but includes other variations and modifications without departing from the present invention as defined by the appended claims.