Abstract:
The present disclosure relates to a touch panel with a conductive bridge structure and a manufacturing method thereof, wherein an anti-reflective layer is disposed on the conductive bridge. According to the touch panel with a conductive bridge structure and the manufacturing method provided in the present disclosure, the problem of visual difference of a touch screen can be eliminated and the manufacturing process can be reduced.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This Application claims the benefit of the People&#39;s Republic of China Application No. 201110347217.6, filed on Nov. 2, 2011. 
       FIELD OF THE INVENTION 
       [0002]    The present disclosure relates to a touch panel and a manufacturing method thereof. More particularly, the present disclosure relates to a touch panel with a conductive bridge structure and a manufacturing method thereof. 
       DESCRIPTION OF THE RELATED ART 
       [0003]    A touch panel usually comprises a substrate, sensing pads arranged along a first axis, and sensing arrays arranged along a second axis on the substrate, wherein the sensing pads arranged along the first axis are electrically connected by a conductive bridge and are electrically insulated from the sensing arrays arranged along the second axis. 
         [0004]    The conductive bridge is made of a lightproof material with high reflectivity (such as molybdenum, aluminum or other metals), so that when touch screen is operated, the conductive bridge reflects light and then a light spot area is formed, namely, a visual difference between the area with the conductive bridge and the area without the conductive bridge appears in the touch screen, leading to visual discomfort for a user. 
       SUMMARY OF THE INVENTION 
       [0005]    In view of the defect of the conventional touch panel, an object of the present disclosure is to provide a touch panel with a conductive bridge structure, forming an anti-reflective layer with a laminated structure on the conductive bridge, such that the conductive bridge is invisible in the touch panel, thereby eliminating the problem of visual difference. 
         [0006]    According, to an embodiment of the present disclosure, a touch panel with a conductive bridge structure is provided, and an anti-reflective layer is disposed on the conductive bridge. 
         [0007]    The anti-reflective layer comprises: a first refractive index layer covering the conductive bridge and a second refractive index layer located on the first refractive index layer, wherein refractive index of the first refractive index layer is lower than that of the conductive bridge and refractive index of the second refractive index layer is higher than that of the first refractive index layer. 
         [0008]    The anti-reflective layer further comprises a third refractive index layer located on the second refractive index layer, wherein refractive index of the third refractive index layer is lower than that of the second refractive index layer. The conductive bridge structure further comprises a protection layer covering the third refractive index layer, wherein refractive index of the third refractive index layer is lower than that of the protection layer. 
         [0009]    Thickness of the first refractive index layer is 19˜23 nm: thickness of the second refractive index layer is 9˜13 nm; and thickness of the third refractive index layer is 22˜28 nm. 
         [0010]    The first refractive index layer and the third refractive index layer are made of a transparent conductive material, and the second refractive index layer is made of a conductive metal material. Preferably, the transparent conductive material is indium tin oxide (ITO), aluminum zinc oxide (AZO) or antimony tin oxide (ATO), and the conductive metal material is aluminum (Al), chromium (Cr), molybdenum (Mo) or copper (Cu). 
         [0011]    According to another embodiment of the present disclosure, a method of manufacturing a touch panel with a conductive bridge structure is provided, the method comprising the following step: forming an anti-reflective layer to cover the conductive bridge. 
         [0012]    The step of forming the anti-reflective layer comprises: forming a first refractive index layer to cover the conductive bridge; and forming, a second refractive index layer on the first refractive index layer, wherein refractive index of the first refractive index layer is lower than that of the conductive bridge and refractive index of the second refractive index layer is higher than that of the first refractive index layer. 
         [0013]    The step of forming the anti-reflective layer further comprises: forming a third refractive index layer to cover the second refractive index layer, wherein refractive index of the third refractive index layer is lower than that of the second refractive index layer. The step of forming the anti-reflective layer further comprises forming a protection layer to cover the anti-reflective layer. The conductive bridge and the anti-reflective layer are formed by a same patterning process. 
         [0014]    For the touch panel of the present disclosure, an anti-reflective layer is formed on a conductive bridge structure by adjusting refractive indices of different refractive index layers in the anti-reflective layer, wherein reflectivity of the anti-reflective layer can be reduced such that the conductive bridge is invisible in the touch panel, thereby eliminating the problem of visual difference. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    For those skilled in the art to understand the present disclosure, numerous embodiments are described below, annexing drawings to minutely illustrate the matters of the disclosure and the purpose thereof. 
           [0016]      FIG. 1A  is a schematic view of an electrode structure of a capacitive touch panel; 
           [0017]      FIG. 1B  is a schematic sectional view along a section line I-I′ shown in  FIG. 1A ; 
           [0018]      FIG. 2  is a schematic view of an anti-reflective layer composed of two layers of materials in a touch panel with a conductive bridge structure in accordance with the present disclosure; 
           [0019]      FIG. 3  is a schematic view of an anti-reflective layer composed of three layers of materials in a touch panel with a conductive bridge structure in accordance with the present disclosure; and 
           [0020]      FIG. 4  is a schematic view of an anti-reflective layer composed of n layers of materials in a touch panel with a conductive bridge structure in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0021]      FIG. 1A  is a schematic view of an electrode structure of a touch panel. A touch panel  10  usually comprises a substrate  11 , first sensing pads  12  arranged along a first axis and second sensing pads  13  arranged along a second axis on the substrate  11 . The two adjacent first sensing pads  12  are connected by a conductive wire  14 . The two adjacent second sensing pads  13  are disposed respectively at two sides of the conductive wire  14  and connected by a conductive bridge  30  that crosses over the conductive wire  14 , and the conductive bridge  30  is electrically insulated from the conductive wire  14  by means of an insulation layer  20 . Moreover, a plurality of metal wires  16  are disposed at the periphery of the electrodes to transmit signals sensed to the external. The conductive bridge  30  can be made of a lightproof material with high reflectivity (such as molybdenum, aluminum or other metals), so that when a touch panel is operated, the conductive bridge  30  can reflect light and then a light spot area is funned. Thus, disposing an anti-reflective layer on the conductive bridge  30  (details will be described subsequently) can solve the problem of light spot, making the conductive bridge invisible in the touch panel and thereby eliminating the problem of visual difference. The above described touch panel structure is only an embodiment of the present disclosure, but it is not limited thereto. If there are elements that can cause a light spot in other touch panel structures, the anti-reflective layer of the present disclosure is also applicable. 
         [0022]      FIG. 1B  is a schematic sectional view along a section line I-I′ shown in  FIG. 1A . Insulation layer  20  covers conductive wire  14  and conductive bridge  30  crosses over the insulation layer  20  to connect adjacent second sensing pads  13 . A protection layer  40  covers the conductive bridge  30 . The anti-reflective layer can be a single-layer structure made of a material, reflectivity of which is lower than that of the conductive bridge, such as indium tin oxide (ITO), aluminum zinc oxide (AZO), antimony tin oxide (ATO) or other transparent conductive materials, or can be a multi-layer structure (as shown in  FIG. 2˜FIG .  4 ), wherein a multi-layer structure is preferred. 
         [0023]      FIG. 2  is a schematic view of an anti-reflective layer composed of two layers of materials in a touch panel with a conductive bridge structure in accordance with the present disclosure. As shown in  FIG. 2 , element symbol  20  refers to an insulation layer and element symbol  30  refers to a conductive bridge. A transparent conductive material layer used as a first refractive index layer  501 , a conductive metal material layer used as a second refractive index layer  502 , and a photoresistive layer (not shown), used for patterning, is formed (such as coating) on the conductive bridge  30  in sequence, wherein refractive index of the first refractive index layer  501  is lower than that of the conductive bridge  30  and refractive index of the second. refractive index layer  502  is higher than that of the first refractive index layer  501 . The transparent conductive material of the first refractive index layer  501  can include indium tin oxide (ITO), aluminum zinc oxide (AZO) or antimony tin oxide (ATO), and the conductive metal material of the second refractive index layer  502  can include aluminum (Al), chromium (Cr), molybdenum (Mo) or copper (Cu). After exposure, an anti-reflective layer  50  with a laminated structure is formed by etching with acidic etchant; and then, a protection layer  40  is coated on the anti-reflective layer  50 . 
         [0024]    As shown in  FIG. 3 , another transparent conductive material layer as a third refractive index layer  503  can be coated on the second refractive index layer  502  to adjust refractive index of the anti-reflective layer  50 . Refractive index of the third refractive index layer  503  is lower than that of the second refractive index layer  502 . The transparent conductive material of the third refractive index layer  503  can include indium tin oxide (ITO), aluminum zinc oxide (AZO) or antimony tin oxide (ATO). According to the requirement, the laminated structure of the anti-reflective layer  50  can have more than three layers by coating to further adjust refractive index of the anti-reflective layer  50 , as first refractive index layer  501 , second refractive index layer  502  . . . nth refractive index layer  50   n , as shown in  FIG. 4 . 
         [0025]    Various embodiments have been described below giving a brief idea about material composition and thickness of each layers of the anti-reflective layer  50  coated on the conductive bridge  30 . 
       Embodiment 1 
       [0026]    An anti-reflective layer  50  having, three refractive index lavers made of ITO, Cr and ITO respectively and a photoresistive layer used for patterning are coated on a conductive bridge  30  in sequence. After exposure, an acidic etchant is used for etching such that the conductive bridge  30  together with the anti-reflective layer  50  has the following structure: the conductive bridge  30 /ITO (thickness: 21 nm)/Cr (thickness: 12 nm)/ITO (thickness: 25 nm). 
       Embodiment 2 
       [0027]    An anti-reflective layer  50  having, three refractive index lavers made of ITO, Al and ITO respectively and a photoresistive layer used for patterning are coated on a conductive bridge  30  in sequence. After exposure, an acidic etchant is used for etching such that the conductive bridge together with the anti-reflective layer  50  has the following structure: the conductive bridge/ITO (thickness: 21 nm)/Al(thickness: 10 nm)/ITO(thickness: 25 nm). 
       Embodiment 3 
       [0028]    An anti-reflective layer  50  having three refractive index layers made of AZO, Al and AZO respectively and a photoresistive layer used for patterning are coated on a conductive bridge  30  in sequence. After exposure, an acidic etchant is used for etching such that the conductive bridge together with the anti-reflective layer  50  has the following structure: the conductive bridge/AZO (thickness: 20 nm)/Al (thickness: 11 nm)/AZO (thickness: 23 nm). 
       Embodiment 4 
       [0029]    An anti-reflective layer  50  having three refractive index layers made of ATO. Mo and ATO respectively and a photoresistive layer used for patterning are coated on a conductive bridge  30  in sequence. After exposure, an acidic etchant is used for etching such that the conductive bridge together with the anti-reflective layer  50  has the following structure: the conductive bridge/ATO (thickness: 22 nm)/Mo (thickness: 12 nm)/ATO (thickness: 27 nm). 
       Embodiment 5 
       [0030]    An anti-reflective layer  50  having three refractive index layers made of AZO, Cr and AZO respectively and a photoresistive layer used for patterning are coated on a conductive bridge  30  in sequence. After exposure, an acidic etchant is used for etching such that the conductive bridge together with the anti-reflective layer  50  has the following structure: the conductive bridge/AZO (thickness: 20 nm)/Cr (thickness: 10 nm)/AZO (thickness: 28 nm). 
         [0031]    By adjusting materials and coating thickness of the laminated layers of the anti-reflective layer, refractive index of the anti-reflective layer can be reduced, thereby making the conductive bridge under the anti-reflective layer invisible. In the above embodiments, thickness of the first, second and third refractive index layers which form the anti-reflective layer is within the scope of 19˜23 nm, 9˜13 nm and 22˜28 nm respectively, thereby achieving a preferable effect. 
         [0032]    While certain embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the disclosure. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitations.