Touch panel with improved optical performance

Abstract

Sunlight can damage a conventional touch screen display and cause the display to be quite difficult to read. Furthermore, conventional touch screen displays are easily damaged, and, once damaged, the entire touch screen is replaced. To address these concerns, a touch panel includes anti-reflective coatings on the surfaces of the top plate and the base plate that are open to the air. These coatings substantially reduce reflections and make the touch screen easier to read in direct sunlight. In particular, the anti-reflective coating used on the upper surface of the base plate is dielectric in nature to reduce reflectivity even further. This dielectric coating includes openings to an underlying conductive layer so that an electrical contact is made when a user deflects the top plate into the base plate. Also, the top plate may be detachably coupled to the base plate, advantageously by double stick adhesive tape, so that only the top plate is replaced when damaged. Furthermore, a resistive voltage divider may be fabricated on the base plate. The resistive voltage divider may include a substantially continuous strip of resistive material disposed on the conductive layer of the base plate, and a plurality of conductive traces disposed on the dielectric layer of the base plate and coupled to the resistive material in selected locations.

What is claimed is:  
     
         1 . A touch panel display system comprising: 
 a computer;    a controller coupled to the computer;    a display screen coupled to the computer;    a touch panel coupled to the controller and being disposed over the display screen, the touch panel comprising: 
 a base plate being disposed adjacent the display screen, the base plate having a rigid substrate having an upper surface and a lower surface, a first conductive layer disposed over the upper surface of the rigid substrate, an anti-reflective dielectric layer disposed over the first conductive layer, the anti-reflective dielectric layer having openings through to the first conductive layer, and a first anti-reflective layer disposed on the lower surface of the rigid substrate; and  
 a top plate being disposed in spaced apart relation over the base plate, the top plate having a flexible substrate having an upper surface and a lower surface, a hard coating layer and a second anti-reflective layer disposed over the upper surface of the flexible substrate, and an anti-reflective conductive layer disposed on the lower surface of the flexible substrate.  
   
     
     
         2 . The system, as set forth in  claim 1 , wherein the display screen comprises a liquid crystal display.  
     
     
         3 . The system, as set forth in  claim 1 , wherein the top plate is removably mounted in spaced apart relation over the base plate.  
     
     
         4 . The system, as set forth in  claim 3 , comprising double stick adhesive tape coupling the top plate to the base plate.  
     
     
         5 . The system, as set forth in  claim 4 , wherein the double stick adhesive tape comprises a relatively high tack adhesive side and a relatively low tack adhesive side.  
     
     
         6 . The system, as set forth in  claim 5 , wherein the relatively high tack adhesive side is coupled to the top plate and the relatively low tack adhesive side is coupled to the base plate.  
     
     
         7 . The system, as set forth in  claim 5 , wherein the relatively high tack adhesive side is coupled to the base plate and the relatively low tack adhesive side is coupled to the top plate.  
     
     
         8 . The system, as set forth in  claim 1 , wherein the second anti-reflective layer is disposed over the hard coating layer.  
     
     
         9 . The system, as set forth in  claim 1 , wherein the top plate comprises an anti-fingerprint layer disposed over the second anti-reflective layer and the hard coating layer.  
     
     
         10 . The system, as set forth in  claim 1 , wherein the anti-fingerprint layer comprises a hydrophobic material.  
     
     
         11 . The system, as set forth in  claim 1 , wherein the rigid substrate comprises glass.  
     
     
         12 . The system, as set forth in  claim 1 , wherein the rigid substrate comprises a first substrate portion bonded to a second substrate portion.  
     
     
         13 . The system, as set fort in  claim 12 , wherein the first substrate portion and the second substrate portion comprise glass.  
     
     
         14 . The system, as set forth in  claim 1 , comprising a coating which reflects solar energy outside the visible spectrum disposed on at least one of the top plate and the base plate.  
     
     
         15 . The system, as set forth in  claim 14 , wherein the coating which reflects solar energy comprises a hot mirror capability.  
     
     
         16 . The system, as set forth in  claim 1 , wherein the first conductive layer comprises at least one of titanium and indium tin oxide.  
     
     
         17 . The system, as set forth in  claim 1 , wherein the anti-reflective dielectric layer comprises at least one of silicon dioxide and magnesium fluoride.  
     
     
         18 . The system, as set forth in  claim 1 , wherein each opening has an area in a range from about 2.5 mils to about 10.0 mils, and wherein the openings have an average spacing in a range from about 10.0 mils to about 50.0 mils.  
     
     
         19 . The system, as set forth in  claim 1 , wherein the first anti-reflective layer comprises multiple layers.  
     
     
         20 . The system, as set forth in  claim 1 , wherein the flexible substrate comprises one of Mylar, Lexan, and CR-39.  
     
     
         21 . The system, as set forth in  claim 1 , wherein the hard coating layer comprises silicon dioxide.  
     
     
         22 . The system, as set forth in  claim 1 , wherein the second anti-reflective layer comprises at least one of silicon dioxide and magnesium fluoride.  
     
     
         23 . The system, as set forth in  claim 1 , wherein the anti-reflective conductive layer comprises at least one of titanium and indium tin oxide.  
     
     
         24 . The system, as set forth in  claim 1 , wherein the touch panel comprises a sensing circuit coupled to the first conductive layer and to the anti-reflective conductive layer, the sensing circuit delivering a signal correlative to a position where the first conductive layer contacts the anti-reflective conductive layer.  
     
     
         25 . The system, as set forth in  claim 24 , wherein the sensing circuit comprises: 
 a substantially continuous resistive member disposed on the first conductive layer adjacent a peripheral portion of the anti-reflective dielectric layer; and    a plurality of conductive traces disposed on the anti-reflective dielectric layer, each of the plurality of conductive traces having a first end coupled to a respective selected location of the resistive member and having a second end coupled to the controller.    
     
     
         26 . A touch screen overlay comprising: 
 a flexible substrate having an upper surface and a lower surface; and    double stick adhesive tape coupled to the lower surface of the flexible substrate.    
     
     
         27 . The overlay, as set forth in  claim 20 , comprising a hard coating layer disposed over the upper surface of the flexible substrate.  
     
     
         28 . The overlay, as set forth in  claim 27 , wherein the hard coating layer comprises silicon dioxide.  
     
     
         29 . The overlay, as set forth in  claim 26 , wherein the flexible substrate comprises one of Mylar, Lexan, and CR-39.  
     
     
         30 . The overlay, as set forth in  claim 26 , comprising an anti-reflective layer disposed over the upper surface of the flexible substrate.  
     
     
         31 . The overlay, as set forth in  claim 30 , wherein the anti-reflective layer comprises at least one of silicon dioxide and magnesium fluoride.  
     
     
         32 . The overlay, as set forth in  claim 26 , comprising an anti-reflective conductive layer disposed on the lower surface of the flexible substrate.  
     
     
         33 . The overlay, as set forth in  claim 32 , wherein the anti-reflective conductive layer comprises at least one of titanium and indium tin oxide.  
     
     
         34 . The overlay, as set forth in  claim 26 , wherein the double stick adhesive tape comprises a relatively high tack adhesive side and a relatively low tack adhesive side.  
     
     
         35 . The overlay, as set forth in  claim 34 , wherein the relatively high tack adhesive side is coupled to the flexible substrate.  
     
     
         36 . The overlay, as set forth in  claim 34 , wherein the relatively low tack adhesive side is coupled to the flexible substrate.  
     
     
         37 . The overlay, as set forth in  claim 26 , comprising an anti-fingerprint layer disposed over the flexible substrate.  
     
     
         38 . The overlay, as set forth in  claim 37 , wherein the anti-fingerprint layer comprises a hydrophobic material.  
     
     
         39 . The overlay, as set forth in  claim 26 , comprising a coating which reflects solar energy outside the visible spectrum disposed over the flexible substrate.  
     
     
         40 . The overlay, as set forth in  claim 39 , wherein the coating which reflects solar energy outside the visible spectrum comprises a hot mirror capability.  
     
     
         41 . A touch screen comprising: 
 a top plate having an upper surface and a lower surface;    a base plate having an upper surface and a lower surface; and    a member detachably coupling the lower surface of the top plate to the upper surface of the base plate.    
     
     
         42 . The touch screen, as set forth in  claim 41 , wherein the top plate comprises a flexible substrate having an upper surface and a lower surface.  
     
     
         43 . The touch screen, as set forth in  claim 42 , wherein the flexible substrate comprises one of Mylar, Lexan, and CR-39.  
     
     
         44 . The touch screen, as set forth in  claim 42 , comprising a hard coating layer disposed over the upper surface of the flexible substrate.  
     
     
         45 . The touch screen, as set forth in  claim 44 , wherein the hard coating layer comprises silicon dioxide.  
     
     
         46 . The touch screen, as set forth in  claim 42 , comprising an anti-reflective layer disposed over the upper surface of the flexible substrate.  
     
     
         47 . The touch screen, as set forth in  claim 46 , wherein the anti-reflective layer comprises at least one of silicon dioxide and magnesium fluoride.  
     
     
         48 . The touch screen, as set forth in  claim 42 , comprising an anti-reflective conductive layer disposed on the lower surface of the flexible substrate.  
     
     
         49 . The touch screen, as set forth in  claim 48 , wherein the anti-reflective conductive layer comprises at least one of titanium and indium tin oxide.  
     
     
         50 . The touch screen, as set forth in  claim 41 , wherein the member comprises double stick adhesive tape.  
     
     
         51 . The touch screen, as set forth in  claim 50 , wherein the double stick adhesive tape comprises a relatively high tack adhesive side and a relatively low tack adhesive side.  
     
     
         52 . The touch screen, as set forth in  claim 51 , wherein the relatively high tack adhesive side is coupled to the lower surface of the top plate and the relatively low tack adhesive side is coupled to the upper surface of the base plate.  
     
     
         53 . The touch screen, as set forth in  claim 51 , wherein the relatively low tack adhesive side is coupled to the lower surface of the top plate and the relatively high tack adhesive side is coupled to the upper surface of the base plate.  
     
     
         54 . The touch screen, as set forth in  claim 42 , comprising an anti-fingerprint layer disposed over the flexible substrate.  
     
     
         55 . The touch screen, as set forth in  claim 54 , wherein the anti-fingerprint layer comprises a hydrophobic material.  
     
     
         56 . The touch screen, as set forth in  claim 42 , comprising a coating which reflects solar energy outside the visible spectrum disposed over the flexible substrate.  
     
     
         57 . The touch screen, as set forth in  claim 56 , wherein the coating which reflects solar energy outside the visible spectrum comprises a hot mirror capability.  
     
     
         58 . The touch screen, as set forth in  claim 41 , wherein the base plate comprises a rigid substrate having an upper surface and a lower surface.  
     
     
         59 . The touch screen, as set forth in  claim 58 , comprising a conductive layer disposed over the upper surface of the rigid substrate.  
     
     
         60 . The touch screen, as set forth in  claim 59 , wherein the conductive layer comprises at least one of titanium and indium tin oxide.  
     
     
         61 . The touch screen, as set forth in  claim 59 , comprising an anti-reflective dielectric layer disposed over the conductive layer, the anti-reflective dielectric layer having openings through to the conductive layer.  
     
     
         62 . The touch screen, as set forth in  claim 61 , wherein the anti-reflective dielectric layer comprises one of silicon dioxide and magnesium fluoride.  
     
     
         63 . The touch screen, as set forth in  claim 58 , comprising an anti-reflective layer disposed on the lower surface of the rigid substrate.  
     
     
         64 . The touch screen, as set forth in  claim 63 , wherein the anti-reflective layer comprises multiple layers of anti-reflective material.  
     
     
         65 . The touch screen, as set forth in  claim 41 , comprising a sensing circuit coupled to the top plate and to the base plate, the sensing circuit delivering a signal correlative to a position where the top plate contacts the base plate.  
     
     
         66 . The touch screen, as set forth in  claim 65 , wherein the sensing circuit comprises: 
 a substantially continuous resistive member disposed on a conductive layer on the base plate adjacent a peripheral portion of a patterned anti-reflective dielectric layer disposed over the conductive layer on the base plate; and    a plurality of conductive traces disposed on the anti-reflective dielectric layer, each of the plurality of conductive traces having a first end coupled to a respective selected location of the resistive member.    
     
     
         67 . A method of repairing a damaged touch screen having a flexible top plate disposed in spaced apart relation over a relatively rigid base plate, the method comprising the acts of: 
 (a) removing the top plate from the base plate; and    (b) disposing a replacement top plate on the base plate.    
     
     
         68 . The method, as set forth in  claim 67 , wherein act (a) comprises the act of breaking an adhesive seal of adhesive tape holding the top plate to the base plate.  
     
     
         69 . A method of manufacturing a touch panel, the method comprising the acts of: 
 (a) providing a base plate;    (b) providing a top plate; and    (c) detachably disposing the top plate over the base plate in spaced apart relation.    
     
     
         70 . A method of manufacturing a touch panel, the method comprising the acts of: 
 (a) disposing a layer of conductive material over an upper surface of a relatively rigid substrate of a base plate;    (b) disposing a patterned layer of anti-reflective dielectric material over the layer of conductive material, the patterned layer of anti-reflective dielectric material having openings through to the layer of conductive material;    (c) disposing a first layer of anti-reflective material over a lower surface of the relatively rigid substrate of the base plate;    (d) disposing a second layer of anti-reflective material over an upper surface of a relatively flexible substrate of a top plate;    (e) disposing a layer of anti-reflective conductive material over a lower surface of the relatively flexible substrate of the top plate; and    (f) arranging the top plate over the base plate such that the anti-reflective conductive material disposed over the lower surface of the top plate is in spaced apart relation to the patterned anti-reflective dielectric layer disposed over the upper surface of the base plate.    
     
     
         71 . A sensing unit for a touch panel comprising: 
 a first plate having a first layer of conductive material disposed on its surface;    a second plate having a second layer of conductive material disposed on its surface and having a layer of dielectric material disposed over the second layer of conductive material such that a peripheral portion of the second layer of conductive material remains exposed, the layer of dielectric material having openings through to the second layer of conductive material;    a substantially continuous resistive member disposed over the exposed peripheral portion of the second layer of conductive material adjacent a periphery of the layer of dielectric material; and    a plurality of conductive traces disposed on the layer of dielectric material, each of the plurality of conductive traces having a first end coupled to a respective selected location of the resistive member.