Patent Publication Number: US-2013234732-A1

Title: Touch panel and method for producing same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. Ser. No. 12/847,327 filed on Jul. 30, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION  
     1. Field of the Invention 
     The present invention relates to a touch panel and a method for producing the touch panel and, more particularly, to a touch panel adapted for large-scale production and a method for producing the touch panel at high productivity and low manufacture cost. 
     2. Description of the Prior Art 
     There are some common types of touch panels, namely, the resistive panels, capacitive panels, surface acoustic wave panels, optical (infrared) panels and so on. Among these, the most commonly used are the resistive panels, followed by the capacitive panels. The advantages of the capacitive touch panels are water-proofing and scratch-proofing, and they have high light transmittance and a broad range of temperature tolerance. Therefore, the panels come at a high price. With the advancement of technology, however, the capacitive touch panels are beginning to gain a share in the market of small monitors. 
     Typically, a conventional capacitive touch panel comprises a bottom transparent substrate, a top transparent substrate and a transparent cover lens. A top indium-tin oxide layer and a bottom indium-tin oxide layer are formed on the surfaces of the top and the bottom transparent substrates, respectively. 
     Afterwards, an optical clear adhesive (OCA) is applied to bind the top transparent substrate and the bottom transparent substrate, so that a layer of OCA is sandwiched between the top indium-tin oxide layer and the bottom indium-tin oxide layer facing each other. The transparent cover lens is bound to the top transparent substrate by a layer of OCA, so as to complete the assembly of the transparent capacitive touch panel. The transparent cover lens serves to protect the top and the bottom transparent substrates. 
     However, the conventional transparent capacitive touch panel is too thick and heavy to meet the design trend of light-weight and slimness, as the top and bottom transparent substrates and the transparent cover lens are all made of glass material. In addition, the conventional manufacturing methods can only produce a single touch panel product at a time and, thus, has limited productivity. There is a need for a method for producing touch panels at elevated productivity and reduced manufacture cost. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide to a touch panel adapted for large-scale production and a method for producing the touch panel at high productivity and low manufacture cost. 
     In order to achieve the object described above, the method according to the invention comprises the steps of : providing a plastic substrate having a top surface and a bottom surface, wherein the plastic substrate includes a plurality of predetermined regions, each of which is to be fabricated into a touch panel;
         forming an icon or artwork layer on the bottom surface of the plastic substrate, wherein the icon or artwork layer comprises a plurality of icon or artwork units, each being disposed on the periphery of a corresponding one of the predetermined regions;   forming a sensing layer on the icon or artwork layer, wherein the sensing layer comprises a plurality of sensing series and a plurality of peripheral wires electrically connected to the sensing series, the sensing series being formed on an area of the predetermined regions that is not covered by the icon or artwork units, and the peripheral wires are disposed on the icon or artwork units in such a manner that they are shielded from outside by the icon or artwork units;   cutting the predetermined regions from the plastic substrate to become individual touch panels; and   subjecting the touch panels to bonding, so that the peripheral wires of the respective touch panels are connected to a flexible printed circuit board.       

     The invention further provides a touch panel produced by the method described above. The touch panel comprises:
         a plastic substrate having a bottom surface, on which an icon or artwork unit is disposed at its periphery;   a sensing layer disposed on the bottom surface of the plastic substrate and the icon or artwork unit and comprising a plurality of sensing series and a plurality of peripheral wires electrically connected to the sensing series;   wherein the sensing series are disposed on an area of the bottom surface of the plastic substrate that is not covered by the icon or artwork unit, and the peripheral wires are disposed on the icon or artwork unit in such a manner that they are shielded from outside by the icon or artwork unit.       

     The invention is superior to the prior art methods in view of the following aspects:
         1. The substrate used in the invention is made of plastic material and, thus, the touch panel produced by the invention is slim enough to meet the trend of light-weight and compactness for electronic products.   2. The invention allows production of multiple touch panels in a single run of operation, thereby greatly enhancing the productivity and lowering the manufacture cost.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and effects of the invention will become apparent with reference to the following description of the preferred embodiments taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a flowchart of the method for producing touch panels according to an embodiment of the invention; 
         FIG. 2  is a schematic diagram of the plastic substrate used in an embodiment of the invention; 
         FIG. 3  is a schematic diagram showing the formation of the icon or artwork layer on the plastic substrate according to an embodiment of the invention; 
         FIG. 4  is a schematic diagram showing the predetermined region and the icon or artwork layer according to an embodiment of the invention; 
         FIG. 5  is a schematic diagram showing the formation of the sensing layer according to an embodiment of the invention; 
         FIG. 6  is a schematic diagram showing the finishing of the sensing layer according to an embodiment of the invention; 
         FIG. 7  is a schematic diagram of a touch panel obtained after the cutting according to an embodiment of the invention; 
         FIG. 8  is a schematic diagram of a touch panel according to an alternative embodiment of the invention; and 
         FIG. 9  is a schematic diagram of a touch panel according to another alternative embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to the flowchart shown in  FIG. 1 , the invented method for producing touch panels comprises the following steps. 
     A plastic substrate  10  is provided. As shown in  FIG. 2 , the plastic substrate  10  includes a plurality of predetermined regions  11 , optionally arranged in a matrix manner on the plastic substrate  10 . Each of the predetermined regions is to be fabricated into a touch panel. 
     Then, an icon or artwork layer  20  is formed. As shown in  FIGS. 3 and 4 , the icon or artwork layer  20  is formed on the bottom surface of the plastic substrate  10  using a screen-printing, ink-jet printing or photolithographic process. The icon or artwork layer  20  comprises a plurality of icon or artwork units  21 , each being disposed on the periphery of a corresponding one of the predetermined regions  11 . The inner periphery of the icon or artwork unit  21  is not perpendicular to the adjacent line of the corresponding predetermined region  11 , so that the formation of the subsequent structures can be complete. In the case of using a screen-printing process to form the icon or artwork units  21  whose outer surfaces meet the corresponding predetermined regions  11  at a non-perpendicular angle, the following parameters may by way of example be used in the process: an ink viscosity of 10-30 dPa·s, the screen conditioned at 50˜400 mesh tetron screen, and the tension at minimum 15 Newton force. The icon or artwork layer  20  thus formed has a film thickness of about 2˜15 μm. 
     Then, a sensing layer is formed. As shown in  FIG. 5 , the plastic substrate  10  and the icon or artwork layer  20  are coated, in sequence, with a transparent conductive layer  31  and a metal layer  32 . The transparent conductive layer  31  and the metal layer  32  are patterned (using, for example, a photolithographic process, a laser patterning process or a printing process) to form a plurality of sensing series  41  and a plurality of peripheral wires  42  electrically connected to the sensing series  41 . As shown in  FIG. 6 , the sensing series  41  are formed on an area of the predetermined regions  11  that is not covered by the icon or artwork units  21 , and the peripheral wires  42  are formed on the icon or artwork units  21  in such a manner that they are shielded from outside by the icon or artwork units  21 . The transparent conductive layer  31  is made of transparent conductive material, such as ITO, with a thickness of about 10-100 nm. The transparent conductive layer  31  is preferably formed by using vacuum DC and RF magnetron sputtering deposition technique. Optionally, an alternative method, such as layer-by-layer sputtering, spray pyrolysis, pulsed laser deposition, arc discharge ion plating, reactive evaporation, ion beam sputtering, or chemical vapor deposition (CVD) etc. can be used. Considering the temperature tolerance of the plastic substrate  10  used in the method, the coating of the transparent conductive layer  31  and the metal layer  32  is preferably carried out at a temperature of less than 100° C. 
     Afterwards, the respective predetermined regions  11  are cut from the plastic substrate  10  to become individual touch panels  1 , as shown in  FIG. 7 . The cutting step can be carried out on a CNC cutting machine, a contour cutting machine, or a laser cutting machine. Considering the mechanical strength of the plastic substrate  10  used in the method, the plastic substrate  10  is preferably subjected to air-cooled dry cutting, whereby it is cut by a synthetic diamond-coated tungsten carbide rotary blade operated at a rotary speed of 10,000˜30,000 rpm, preferably about 25,000 rpm, and a forward speed of 1000˜5000 mm/min, preferably about 3000 mm/min. 
     After cutting, the obtained touch panels are subjected to a bonding step, in which the peripheral wires  42  of the respective touch panels  1  are connected to a flexible printed circuit board (not shown), thereby producing finished touch panel products. It should be noted that the cutting step and the bonding step shown in  FIG. 1  can be interchanged. That is to say, the cutting step may be carried out either prior to or subsequent to the bonding step. Considering the temperature tolerance of the plastic substrate  10  used in the method, the bonding is preferably carried out at a relatively low temperature, more preferably less than 120° C., and a pressure of 1˜2 bar, more preferably about 1.5 bar, for a time period of 10˜40 seconds, more preferably about 25 seconds. 
     The touch panel produced according to the invention comprises a plastic substrate. According to the embodiment shown in  FIG. 7 , the touch panel comprises a plastic substrate  10  having a bottom surface, on which an icon or artwork unit  21  is disposed at its periphery. A sensing layer is disposed on the bottom surface of the plastic substrate  10  and the icon or artwork unit  21  and comprises a plurality of sensing series  41  and a plurality of peripheral wires  42  electrically connected to the sensing series  41 . The sensing series  41  are disposed on an area of the bottom surface of the plastic substrate  10  that is not covered by the icon or artwork unit  21 , and the peripheral wires  42  are disposed on the icon or artwork unit  21  in such a manner that they are shielded from outside by the icon or artwork unit  21 . In addition, the icon or artwork unit  21  has an inner periphery that is not perpendicular to the adjacent line of the plastic substrate  10 , so that the cladding of the subsequent structures can be complete. 
     In addition, an optical film may be formed before and/or after the formation of the sensing layer, so that the sensing layer is coated on one or both of its surfaces with the optical film. According to an alternative embodiment shown in  FIG. 8 , the bottom surface of the plastic substrate  10  is further provided with a first optical film  51 , on which the sensing layer is mounted. The first optical film  51  is disposed on the icon or artwork unit and an area of the bottom surface of the plastic substrate  10  that is not covered by the icon or artwork unit  21 . The first optical film  51  serves to minimize the adverse effect of the etched pattern of the sensing layer on the user&#39;s visual perception. The first optical film  51  may be formed to have a thickness of less than 200 nm by a sputtering, spraying or coating process. 
     It is apparent to those skilled in the art that the sensing layer may be additionally coated with a second optical film. According to the embodiment shown in  FIG. 9 , the sensing layer is further coated with a second optical film  52 , such as an anti-glare coating or an anti-reflection coating, as a means to enhance the overall transparency. 
     While the invention has been described with reference to the preferred embodiments above, it should be recognized that the preferred embodiments are given for the purpose of illustration only and are not intended to limit the scope of the present invention and that various modifications and changes, which will be apparent to those skilled in the relevant art, may be made without departing from the spirit of the invention and the scope thereof as defined in the appended claims.