Abstract:
A touch panel has a substrate and a flexible printed circuit board (PCB). The substrate has multiple wires. A first end of each of the wires is formed on a top surface of the substrate, and a second end extends to a bottom surface of the substrate through a side edge of the substrate. The substrate further has an anisotropic conductive layer mounted on the bottom surface of the substrate and covering the second end of each of the wires. The flexible PCB is mounted on a bottom surface of the anisotropic conductive film. Because the flexible PCB is mounted on the bottom surface of the substrate, a drawback of the conventional touch panels that loose bonding occurs at which the flexible PCB is mounted can be resolved.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a touch panel, and more particularly to a touch panel having a flexible printed circuit board mounted on a bottom of a substrate of the touch panel with enhanced bonding strength. 
         [0003]    2. Description of the Related Art 
         [0004]    Touch panels can be classified as capacitive touch panels, resistive touch panels, surface acoustic touch panels, infrared touch panels and the like in terms of the touch panel technologies. Among them, the capacitive touch panels and the resistive touch panels take the leading position in market share. The technologies behind the capacitive touch panels and the resistive touch panels detect the location of a touched point based on capacitive and voltage variation generated at the touched point. Structurally, resistive touch panels are bisubstrate while capacitive touch panels can be either single-substrate or bisubstrate. In case of a single-substrate touch panel, an indium tin oxide (ITO) layer is formed on a top surface of the substrate. In case of a bisubstrate touch panel, two ITO layers are respectively mounted on the surface of the upper substrate and the surface of the lower substrate, which face each other and can be folded together, and serve to sense capacitive or voltage variation. The capacitive or voltage variation signals are outputted to a controller for computation through wires and a flexible PCB mounted on the top surface of the substrate of a single-substrate touch panel or mounted between the two substrates of a bisubstrate touch panel. 
         [0005]    As for conventional touch panels, whether single-substrate touch panels or bisubstrate touch panels, the position to which the flexible PCB is mounted is prone to negative impact on the performance of the touch panels. As for the bisubstrate touch panels, since the flexible PCB is mounted and squeezed between the two substrates, the portions between the two substrates where the flexible PCB is mounted are not easy to be tightly bonded. As for the single-substrate touch panels, since a protection layer is additionally mounted on a top surface of the substrate to protect the ITO layer, the issue that the portions between the substrate and the protection layer where the flexible PCB is mounted are not easy to be tightly bonded also exists for a similar reason. To prevent bubbles generated by incorrect bonding from affecting the performance of the touch panels, manufacturers of touch panels develop an improved structure which has drill holes formed through the substrate of the single-substrate touch panels or the lower substrate of the bisubstrate touch panels and corresponding to wires thereon and conductors are mounted through the drill holes. Therefore, signals of the wires can be transmitted to the bottom of the substrate or the lower substrate, and the flexible PCB can be mounted on the bottom of the substrate and the lower substrate to resolve the loose bonding issue. 
         [0006]    However, the aforementioned structure is feasible only when applied to a resistive touch panel whose number of the wires is no larger than eight. Since the wires of a capacitive touch panel are plentiful and densely arranged, drill holes must be smaller and positioned more accurately so as to prevent misconnection with adjacent wires. Hence, the drilling process becomes complicated and infeasible and cause significant rise in cost and high defect rate in production. 
       SUMMARY OF THE INVENTION 
       [0007]    An objective of the present invention is to provide a touch panel having a flexible printed circuit board mounted on a bottom of a substrate of the touch panel with enhanced bonding strength. 
         [0008]    To achieve the foregoing objective, the touch panel has a substrate, multiple wires, an anisotropic conductive film and a flexible PCB. 
         [0009]    The wires are formed on a top surface of the substrate. Each wire has a first end and a second end, and the second end of the wire extends to a bottom surface of the substrate through a side edge of the substrate. The anisotropic conductive film is mounted on the bottom surface of the substrate and covers the second end of each of the wires. The flexible PCB is mounted on a bottom surface of the anisotropic conductive film. 
         [0010]    Preferably, the substrate further has multiple first conductive layers and multiple second conductive layers. The first conductive layers are formed on the top surface of the substrate, and parallelly align in a first direction. Each of the first conductive layers has multiple first sensing units and a first port. The first sensing units are serially connected. The first port is formed on an edge of one of the outermost first sensing units in the first direction. The second conductive layers are formed on the top surface of the substrate, correspond to a portion of the top surface of the substrate unfilled by the first conductive layers, and parallelly align in a second direction that is perpendicular to the first direction. Each of the second conductive layers has multiple second sensing units and a second port. The second sensing units are serially connected. The second port is formed on an edge of one of the outermost second sensing units in the second direction. A count of the wires corresponds to that of the first ports and the second ports respectively on the first conducting layer and the second conducting layer. The first end of each of the wires located on the top surface of the substrate is connected to one of the first ports and the second ports. 
         [0011]    The present invention provides an alternative touch panel. The touch panel has a lower substrate, an upper substrate, an anisotropic conductive film and a flexible PCB. 
         [0012]    The lower substrate has at least one lower wire formed on a top surface of the lower substrate. Each of the at least one lower wire has a first end and a second end, and the second end of the lower wire extends to a bottom surface of the lower substrate through a side edge of the lower substrate. 
         [0013]    The upper substrate is mounted on the top surface of the lower substrate, and has at least one upper wire formed thereon. A first end of each of the at least one upper wires is formed on a bottom surface of the upper substrate, and a second end of the upper wire extends to a bottom surface of the lower substrate through a side edge of the lower substrate. 
         [0014]    The anisotropic conductive film is mounted on the bottom surface of the lower substrate, and covers the second end of each of the lower wire and the upper wire. 
         [0015]    The flexible PCB is mounted on a bottom surface of the anisotropic conductive film. 
         [0016]    The touch panel further has an insulating layer and a separation layer. The insulating layer is frame-shaped, is mounted between the upper substrate and the lower substrate, and covers the first end of each of the lower wires on the top surface of the upper substrate. The separation layer is mounted between the upper substrate and the lower substrate and is surrounded by the insulating layer. 
         [0017]    The lower substrate further has a lower conductive layer formed thereon. The first end of each of the at least one lower wire is formed on a top surface of the lower conductive layer. 
         [0018]    The upper substrate further has an upper conductive layer formed thereon. The first end of each of the at least one upper wire is formed on a bottom surface of the upper conductive layer and is covered by the insulating layer. 
         [0019]    Preferably, the touch panel further comprises an insulating layer mounted between the upper substrate and the lower substrate. 
         [0020]    The lower substrate further has multiple lower conductive layers and a lower port. The lower conductive layers parallelly align in a first direction. Each of the lower conductive layers has multiple lower sensing units serially connected. The lower port is formed on an edge of one of the outermost lower sensing units in the first direction. 
         [0021]    The upper substrate further has multiple upper conductive layers and an upper port. The upper conductive layers parallelly align in a second direction, and correspond to a portion of a top surface of the lower substrate unfilled by the lower conductive layers. Each of the lower conductive layers has multiple lower sensing units serially connected. The upper port is formed on an edge of one of the outermost upper sensing units in the second direction. 
         [0022]    A count of the at least one lower wire formed on the lower substrate corresponds to that of the lower ports. The first end of each of the at least one lower wire is connected to a corresponding lower port. 
         [0023]    A count of the at least one upper wire formed on the upper substrate corresponds to that of the upper ports. The first end of each of the at least one upper wire is connected to a corresponding upper port. 
         [0024]    Preferably, the touch panel further has an insulating layer mounted between the upper substrate and the lower substrate. 
         [0025]    The lower substrate further has multiple lower conducting layers and a lower port. The lower conducting layers are juxtaposedly formed on the top surface of the lower substrate, are rectangular, and align in a first direction. The lower port is formed on one side of a corresponding lower conducting layer that is perpendicular to the first direction. 
         [0026]    The upper substrate further has multiple upper conducting layers and an upper port. The upper conducting layers are juxtaposedly formed on the bottom surface of the upper substrate, are rectangular, and align in a second direction that is perpendicular to the first direction. The upper port is formed on one side of a corresponding upper conducting layer that is perpendicular to the second direction. 
         [0027]    A count of the at least one lower wire formed on the lower substrate corresponds to that of the lower ports. The first end of each of the at least one lower wire is connected to a corresponding lower port. 
         [0028]    A count of the at least one upper wire formed on the upper substrate corresponds to that of the upper ports. The first end of each of the at least one upper wire is connected to a corresponding upper port. 
         [0029]    With regards to the touch panel of the present invention, the flexible PCB is mounted on the bottom surface of the substrate, thereby overcoming the shortcoming that the conventional touch panels cannot be tightly bonded at the portion where the flexible PCB is mounted. Besides, one end of each of the wires in the present invention extends to the bottom surface of the substrate through a side edge of the substrate to electrically connect with the flexible PCB through the anisotropic conductive film. In contrast to the conventional drilling process, the present invention can further lower cost and improve yield of touch panels. 
         [0030]    Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is an exploded perspective view of a single-substrate touch panel in accordance with the present invention; 
           [0032]      FIG. 2  is a perspective view of a single-substrate projected capacitive touch panel in accordance with the present invention; 
           [0033]      FIG. 3  is a perspective view of a bisubstrate touch panel in accordance with the present invention; 
           [0034]      FIG. 4  is an exploded perspective view of a bisubstrate resistive touch panel in accordance with the present invention; 
           [0035]      FIG. 5  is an exploded perspective view of a bisubstrate projected capacitive touch panel in accordance with the present invention; and 
           [0036]      FIG. 6  is an exploded perspective view of a bisubstrate matrix capacitive touch panel in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    Touch panels in accordance with the present invention are characterized in that one end of each of the wires for transmitting signals extends to a bottom surface of a substrate. Such characteristic can be applied to all types of touch panels, such as projected capacitive touch panels built with single substrate, or resistive touch panels, projected capacitive touch panels, matrix capacitive touch panels built with two substrates. Embodiments are listed to describe the touch panels in accordance with the present invention as follows. 
         [0038]    With reference to  FIGS. 1 and 2 , a single-substrate projected capacitive touch panel in accordance with the present invention has a substrate  10  and a flexible PCB  20 . 
         [0039]    The substrate  10  has multiple first conductive layers  11 , multiple second conductive layers  12 , an anisotropic conductive film  13  and multiple wires  14 . The first conductive layers  11  and the second conductive layers  12  are formed on a top surface of the substrate  10  and crossly align with each other. The anisotropic conductive film  13  is mounted on a bottom surface of the substrate  10 . The wires  14  are formed on the substrate  10 . The first conductive layers  11  parallelly align in a first direction and each of the first conductive layers  11  has multiple first sensing units  111  and a first port  112 . The first sensing units  111  are serially connected and are composed of ITO. In the present embodiment, the first sensing units  111  are rhombic. Each of the first ports  112  is formed on an edge of one of the outermost first sensing units  111  in the first direction and is made of a conductive material. 
         [0040]    The second conductive layers  12  are formed on the top surface of the substrate  10 , parallelly align in a second direction that is perpendicular to the first direction, correspond to a portion of the top surface of the substrate  10  unfilled by the first conductive layers  11 , and each of the second conductive layers  12  has multiple second sensing units  121  and a second port  122 . The second sensing units  121  are serially connected, and are composed of ITO. In the present embodiment, the second sensing units  121  are rhombic. Each of the second ports  122  is formed on an edge of one of the outermost second sensing units  121  in the second direction and is made of a conductive material. 
         [0041]    The wires  14  are formed on the top surface of the substrate  10 . A count of the wires  14  corresponds to that of the first ports  112  and the second ports  122  respectively on the first conducting layer  11  and the second conducting layer  12 . One end of each of the wires  14  on the top surface of the substrate  10  is connected to one of the first ports  142  and the second ports  152 . The other end of the wire  14  extends to the bottom surface of the substrate  10  through a side edge of the substrate  10  and is covered by the anisotropic conductive film  13 . 
         [0042]    The flexible PCB  20  is mounted on a bottom surface of the anisotropic conductive film  13 . Each terminal of the flexible PCB  20  is electrically connected with a corresponding wire  14  through the anisotropic conductive film  13 . 
         [0043]    With reference to  FIG. 3 , a bisubstrate touch panel in accordance with the present invention, whether a resistive touch panel, a projected capacitive touch panels or a matrix capacitive touch panel, has a flexible PCB  50 , and an upper substrate  30  and a lower substrate  40  mutually folded together. The upper substrate  30  has at least one upper wire  31  formed thereon, and the lower substrate  40  has at least one lower wire  41  formed thereon. The lower substrate  40  further has an anisotropic conductive film  43  mounted on a bottom surface of the lower substrate  40 . The flexible PCB  50  is mounted on a bottom surface of the anisotropic conductive film  43 . Specific structures associated with resistive touch panels, projected capacitive touch panels or matrix capacitive touch panels are described in the following. 
         [0044]    With reference to  FIG. 4 , a resistive touch panel in accordance with the present invention further has an insulating layer  61 A and a separation layer  62 . The lower substrate  40 A has a lower conductive layer  42 A formed on a top surface thereof and is composed of ITO. The lower substrate  40 A further has at least one lower wire  41 A. Given an example of five-wire resistive touch panel in  FIG. 4 , four lower wires  41  are formed on a top surface of the lower conductive layer  42 . Similar to  FIG. 3 , each lower wire  41  has two ends, and one end of each of the four lower wires  41  extends to a bottom surface of the lower substrate  40 A through a side edge of the lower substrate  40 A, is covered by the anisotropic conductive film  43 , and is electrically connected with one of terminals of the flexible PCB  50  through the anisotropic conductive film  43 . 
         [0045]    The insulating layer  61 A is frame-shaped and is mounted between the upper substrate  30 A and the lower substrate  40 A and covers the end of each lower wire  41 A on the top surface of the lower substrate  40 A. 
         [0046]    The separation layer  62  is mounted between the upper substrate  30 A and the lower substrate  40 A and is surrounded by the insulating layer  61 A. 
         [0047]    The upper substrate  30 A has an upper conductive layer  32 A formed on a bottom surface thereof and composed of ITO. The upper substrate  30 A further has at least one upper wire  31 A. Given the example of five-wire resistive touch panel in  FIG. 4  again, one upper wire  31 A is formed on the upper conductive layer  32 A. The upper wire  31 A has two ends, and one end of the upper wire  31 A is covered by the insulating layer  61 A. Similar to  FIG. 3 , the other end of the upper wire  31 A extends to the bottom surface of the lower substrate  40 A through the insulating layer  61 A and the side edge of the lower substrate  40 A, is covered by the anisotropic conductive film  43 , and is electrically connected with a corresponding terminal of the flexible PCB  50  through the anisotropic conductive film  43 . 
         [0048]    With reference to  FIG. 5 , a projected capacitive touch panel further has an insulating layer  61 B. The lower substrate  40 B has multiple lower conductive layers  42 B, multiple lower ports  422  and multiple lower wires  41 B. The lower conductive layers  42 B are formed on a top surface of the lower substrate  40 B and parallelly align in a first direction. Each of the lower conductive layers  42 B has multiple lower sensing units  421  serially connected and composed of ITO. In the present embodiment, the lower sensing units  421  are rhombic. Each of the lower ports  422  is formed on an edge of one of the outermost lower sensing units  421  in the first direction and is made of a conductive material. A count of the lower wires  41 B formed on the lower substrate  40 B corresponds to that of the lower ports  422 . One end of each of the lower wires  41 B is formed on the top surface of the lower substrate  40 B and is connected with a corresponding lower port  422 . Similar to  FIG. 3 , the other end of the lower wire  41 B extends to a bottom surface of the lower substrate  40 B through a side edge of the lower substrate  40 B, is covered by the anisotropic conductive film  43 , and is electrically connected with a corresponding terminal of the flexible PCB  50  through the anisotropic conductive film  43 . 
         [0049]    The insulating layer  61 B is mounted between the upper substrate  30 B and the lower substrate  40 B. 
         [0050]    The upper substrate  30 B has multiple upper conductive layers  32 B, multiple upper ports  322  and multiple upper wires  31 B. The upper conductive layers  32 B are formed on a bottom surface of the upper substrate and parallelly align in a second direction that is perpendicular to the first direction, and correspond to a portion of the top surface of the lower substrate  40 B unfilled by the lower conductive layers  42 B. Each of the upper conductive layers  32 B has multiple upper sensing units  321  serially connected and composed of ITO. In the present embodiment, the upper sensing units  321  are rhombic. Each of the upper ports  322  is formed on an edge of one of the outermost upper sensing units  321  in the second direction and is made of a conductive material. A count of the upper wires  31 B formed on the upper substrate  30 B corresponds to that of the upper ports  322 . One end of each of the upper wires  31 B is formed on the bottom surface of the upper substrate  30 B and is connected with a corresponding upper port  322 . Similar to  FIG. 3 , the other end of the upper wire  31 B extends to the bottom surface of the lower substrate  40 B through the insulating layer  61 B and a side edge of the lower substrate  40 B, is covered by the anisotropic conductive film  43  and is electrically connected with a corresponding terminal of the flexible PCB  50  through the anisotropic conductive film  43 . 
         [0051]    With reference to  FIG. 6 , a matrix capacitive touch panel further has an insulating layer  61 C. The lower substrate  40 C has multiple lower conducting layers  42 C juxtaposedly formed on a top surface of the lower substrate  40 C, are rectangular, align in a first direction, and are composed of ITO. Each of the lower conducting layers  42 C has a lower port  423  formed on one side thereof that is perpendicular to the first direction, and is made of a conductive material. The lower wires  41 C are formed on the lower substrate  40 C, and a count of the lower wires  41 C corresponds to that of the lower ports  423 . One end of each of the lower wires  41 C is formed on the top surface of the lower substrate  40 C and is connected to a corresponding lower port  423 . Similar to  FIG. 3 , the other end of the lower wire  41 C extends to a bottom surface of the lower substrate  40 C through a side edge of the lower substrate  40 C, is covered by the anisotropic conductive film  43 , and is electrically connected with a corresponding terminal of the flexible PCB  50  through the anisotropic conductive film  43 . 
         [0052]    The insulating layer  61 C is mounted between the upper substrate  30 C and the lower substrate  40 C. 
         [0053]    The upper substrate  30 C has multiple upper conducting layers  32 C. The upper conducting layers  32 C are juxtaposedly formed on a bottom surface of the upper substrate  30 C, are rectangular, align in a second direction that is perpendicular to the first direction, and are composed of ITO. Each of the upper conducting layers  32 C has a upper port  323  formed on one side thereof that is perpendicular to the second direction, and is composed of a conductive material. The upper wires  31 C are formed on the upper substrate  30 C, and a count of the upper wires  31 C corresponds to that of the upper ports  323 . One end of each of the upper wires  31 C is formed on the bottom surface of the upper substrate  30 C and is connected to a corresponding upper port  323 . Similar to  FIG. 3 , the other end of the upper wire  31 C extends to a bottom surface of the lower substrate  40 C through the insulating layer  61 C and the side edge of the lower substrate  40 C, is covered by the anisotropic conductive film  43 , and is electrically connected with a corresponding terminal of the flexible PCB  50  through the anisotropic conductive film  43 . 
         [0054]    In sum, one end of each of the wires of the touch panels in accordance with the present invention, which is connected with the flexible PCB, extends to the bottom surface of the substrate through a side edge of the touch panel so that the flexible PCB can be mounted on the bottom surface of the substrate. Such design resolves the issue that the portion of a conventional touch panel where the flexible PCB is mounted is not easy to be tightly bonded. Also because the fabrication process of the present invention is relatively simpler than the drilling process used in conventional technique, the resulting cost is lowered and the yield is improved. 
         [0055]    Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.