Abstract:
The present invention is a touch detection panel that uses capacitance changes between electrodes and changes thereof to determine a position of touch. The touch panel can be used in commercial applications where using a finger, stylus, or other object is the desired method of interface with an electronic system. The touch panel includes conductive electrodes and conductive lines connecting the conductive electrodes. The conductive electrodes themselves can be made of opaque conductive material, substantially transparent conductive material, or transparent conductive material depending on the requirements of an application. One such material is a metal mesh. The Touch panel is connected to a controller that applies current and/or voltage to the touch panel and senses current and/or voltage from the touch panel to determine either single or multiple touch locations.

Description:
BACKGROUND 
       [0001]    Human-machine interface has long been studied and different methods have been developed to interface with machines. Entering characters on a keyboard is one way of entering information into a machine. Mice are also used to move a cursor on a screen and point to a certain area to enter information. Combination of keyboard and mice entries can be replaced by touch panels that are either overlaid or embedded on a display device or a mouse pad to enter information to a machine. Touch panels detect the object touching the surface of the touch panel and produce a signal that indicates the position of a touch. There are different touch technologies including resistive, capacitive, projected capacitive, acoustic, force and optical. 
         [0002]    Currently the most popular technology is a projective capacitive technology due to its ability to provide multiple touches, meaning if several objects touch the touch panel the locations of all the objects can be determined either simultaneously or in a very short period of time from each other. 
         [0003]    Multiple touch projective capacitive touch panels detect the change in current due to change in capacitance. When an electrode line of a capacitive touch panel is driven by a current source, all capacitances on those electrodes are charged. The charging time changes depending upon the number of electrodes and the resistance of the given line on a given axis. As the touch panel gets larger, an increasing number of electrodes are needed per axis to provide proper resolution. As the number of electrodes increases, the resistance increases therefore increasing the charging time. Increased charging time reduces the speed of the touch panel circuit. 
       SUMMARY OF THE INVENTION 
       [0004]    One objective of the invention is to reduce the charging time on a given axis for a capacitive touch panel therefore increasing the response time. 
         [0005]    Another object of the invention is to provide a touch panel with a better visual performance while reducing the resistance of electrodes. 
         [0006]    Another object of the invention is to manufacture a touch panel wherein all electrodes with lower resistance are placed on the same layer of a substrate and self capacitances or mutual capacitances or the combination of both self capacitance and mutual capacitances are used to determine the location of a touch. 
         [0007]    Another object of the invention is to build a touch panel wherein a plurality of capacitances on a surface are used to determine a single or multiple touch locations. 
         [0008]    Another object of the invention is to provide a touch panel wherein as the size increases, regardless of the touch panel structure, the speed of the touch panel is kept at an acceptable level. 
         [0009]    Another object of the invention is to provide a formula for designing a touch panel wherein proper variables are used to change the touch panel design that is sensitive to touches on its surface. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  shows a single layer projective capacitive touch panel using metal mesh 
           [0011]      FIG. 2  shows four electrodes set up with metal mesh 
           [0012]      FIG. 3  shows four electrodes with a different embodiment 
           [0013]      FIG. 4  shows an embodiment where discrete insulation is used 
           [0014]      FIG. 5  shows a single layer touch panel using elongated electrodes 
           [0015]      FIG. 6  shows a touch panel being connected to a controller 
           [0016]      FIG. 7  shows the process of making the touch panel 
           [0017]      FIG. 8  shows cross section of a dual layer touch panel 
           [0018]      FIG. 9  shows cross section of a single layer touch panel 
           [0019]      FIG. 10  shows cross section of a single layer touch panel 
           [0020]      FIG. 11  shows cross section of a dual layer touch panel 
           [0021]      FIG. 12  shows cross section of a single layer touch panel 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0022]      FIG. 1  shows touch panel  80  that has substrate  1 . First conductive electrode assembly  2  built on substrate  1 , second conductive assembly  3  built on substrate  1 . First conductive assembly  2  contains a plurality of conductive electrodes  2  in a horizontal direction. A plurality of conductive electrodes  6  of first conductive electrode assembly  2  are connected to each other by conductive lines  8 . There is a plurality of first conductive electrode assembly  2 . Second conductive assembly  3  contains a plurality of conductive electrodes  5  in vertical direction. Conductive electrodes  5  of second conductive electrode assembly  3  are connected to each other by conductive lines  7 . There is a plurality of second conductive electrode assembly  3 . Plurality of first conductive assemblies  2  are connected to controller  4  by plurality of connecting wires  82  and  84 . Likewise, a plurality of second conductive assemblies  3  are connected to controller  4  by plurality of connecting wires  81  and  83 . Plurality of conductive lines  7  and plurality of conductive lines  8  are insulated from each other by using plurality of discrete insulators  9 . Discrete insulators are made of material that do not conduct electricity. The material can be opaque or transparent. 
         [0023]    Each conductive electrode  6  has a self capacitance between conductive electrode  6  and the ground. Likewise each conductive electrode  5  has a self capacitance between conductive electrode  5  and the ground. A self capacitance in this invention is defined as a capacitance between a conductor and the ground. A self capacitance depends on the size of the conductor and the permittivity of the conductor. It is also determined by the distance between the conductor and the ground. There also exists mutual capacitance between conductive electrode  6  and conductive electrode  5 . Mutual capacitance is determined by three variables among other things. The distance between conductive electrode  5  and conductive electrode  6 , the area between the conductive electrode  5  and conductive electrode  6  and the permittivity of the material used to build conductive electrode  5  and conductive electrode  6 . 
         [0024]    Touch panel  80  can detect touches on substrate  1  by using different techniques. In the first technique, controller  4  applies a current at a predetermined fundamental frequency to conductive assembly  3 . The current is applied to one conductive assembly  3  at a time in sequence. While current is applied to one of the conductive assemblies  3 , conductive assemblies  2  in the horizontal direction are sensed in a sequence. Once all the conductive assemblies  2  in horizontal direction are sensed, a current is applied to next conductive assembly  3  and then all conductive assemblies  2  are sensed in sequence. This process is repeated so that a map of capacitance distribution of touch panel  80  is calculated and stored in controller  4 . This mapping of the touch panel is important because there are many stray capacitances caused by the touch panel structure and other neighboring structures. By mapping the touch panel  80 , all the current capacitances captures while there is no touch on the surface. If a touch occurs, the capacitance at the point of touch will alter the capacitance at that point and as a result, the current sensed from that line will change. Controller  4  detects this change and determines the touch location based on this change. 
         [0025]    An alternative method of increasing signal to noise ratio is to model touch panel  80  as a band pass filter (BPF). It has many self and mutual capacitances and conductive resistances built on the panel. When a current is applied to conductive assembly  3 , certain amount of current will pass to conductive assembly  2  based on the filter characteristics. Therefore it is important to find the optimum frequency for the signal applied to touch panel  80  based on the filter characteristics. The filter characteristics can be best recognized by applying signals with different frequencies to touch panel  80  and measuring the output to determine the filter characteristics. This way, an amplitude versus frequency graph can be obtained and saved in the storage in controller  4  for each conductive assembly  3  and conductive assembly  2 . By knowing these many curves, an optimum input frequency can be identified to provide the best signal to noise ratio. The system is adaptive in that during the normal operation of touch panel  80 , a current with a certain frequency is applied to each conductive assembly  3 . The frequency of the current applied to each individual conductive assembly in the vertical direction may be the same or similar or different based on the filter characteristic is obtained. When current is applied to one of the conductive assemblies  3 , conductive assemblies  2  are sensed in a sequence. Alternatively a current with a certain frequency may be applied to each conductive assembly  2 . The frequency of the current applied to each individual conductive assembly in the vertical direction may be the same or similar or different based on the filter characteristic is obtained. When current is applied to one of the conductive assemblies  2 , conductive assemblies  3  are sensed in a sequence. By knowing the filter characteristics of touch panel  80 , each conductive assembly is driven with a current with an optimum frequency based on the filter characteristics and therefore an optimum signal to noise ratio is obtained at the output of sensing conductive assemblies. 
         [0026]      FIG. 2  shows the detailed structure of four electrodes. Conductive electrodes  5  and  55  form second conductive electrode assembly  3 . Conductive electrodes  6  and  66  form first conductive electrode assembly  2 . Conductive line  7  connects conductive electrode  5  to conductive electrode  55 . Conductive line  8  connects conductive electrode  6  to conductive electrode  66 . Insulator  9  is placed between conductive line  7  and conductive line  8  and provides insulation so that conductive line  7  and conductive line  8  do not touch each other. In this embodiment, conductive electrodes  5 ,  55 ,  6 , and  66  are built using metal mesh structure. Metal mesh is a structure where very thin metal lines in both horizontal and vertical direction are placed within each electrode such that horizontal and vertical metal lines touch each other. In this embodiment, conductive electrodes  5 ,  55 ,  6 , and  66  are built using metal meshes while conductive line  7  is a single conductive line connecting conductive electrode  5  to conductive electrode  55 . Conductive line  8  is a single conductive line connecting conductive electrode  6  to conductive electrode  66 . In a different embodiment, conductive electrodes  5 ,  55 ,  6 , and  66  can be solid metal or transparent conductive material replacing metal meshes. 
         [0027]      FIG. 3  shows another embodiment of this invention. In this embodiment, metal mesh is used to build conductive electrode  35 , conductive electrode  37 , conductive electrode  36 , and conductive electrode  38 . Conductive line  10  connects conductive electrode  36  to conductive electrode  38 . Conductive line  10  in this embodiment is different from conductive line  8  in embodiment in  FIG. 2  in that conductive line  10  is made of metal mesh while conductive line  8  is a single line. Conductive line  11  connects conductive electrode  35  to conductive electrode  37 . Conductive line  11  in this embodiment is different than conductive line  7  in embodiment in  FIG. 2  in that conductive line  11  is made of metal mesh while conductive line  7  is a single line. Insulator  12  is placed between conductive line  10  and conductive line  11  and insulates conductive line  10  from conductive line  11 . In this embodiment, a single discrete insulator  12  is used to insulate conductive line  10  from conductive line  11 . In an alternative embodiment, conductive electrodes  35 ,  37 ,  36 , and  38  can be built using solid metal or solid transparent material while conductive line  10  and conductive line  11  can be built using metal mesh structure. 
         [0028]    Metal mesh used in this invention can be any conductive metal including metal nanowires or micro wires. 
         [0029]      FIG. 4  shows another embodiment of this invention wherein a different insulation structure is used. Conductive line  10  and conductive line  11  are made of metal meshes. Metal meshes are built by placing vertical and horizontal metal lines on a substrate and after the process, patterning these metal meshes to form conductive electrodes and conductive lines as shown in  FIG. 3  and  FIG. 4 . When conductive lines  10  and  11  cross each other, a connection will be made between individual metal mesh lines unless they are insulated from each other. Here, each metal mesh line has discrete insulator  13 . Plurality of discrete insulators  13  are used to insulate each metal mesh line in conductive line  11  from each metal mesh line in conductive line  10 . The size and shape of discrete insulator  13  can be chosen to provide insulation between metal mesh lines. Insulator  13  can be built using transparent or opaque material. Metal mesh line size can be between 1 nanometer and 100 micrometer. Preferably between 1 nm and 100 nanometer. The size of conductive line  10  and conductive line  11  may be between 10 nm and 1 mm. 
         [0030]      FIG. 5  shows another embodiment of the invention. In this embodiment, touch panel  91  includes conductive lines  21  in horizontal direction and conductive lines  22  in vertical direction. Both conductive lines  21  and conductive lines  22  are placed on the same side of substrate  90 . A plurality of discrete insulators  23  are placed between conductive lines  21  and conductive lines  22  such that conductive lines  21  do not make contact with conductive lines  22 . The shape and size of discrete insulator  23  can be adjusted based on the touch panel size and the sizes of conductive lines  21  and conductive lines  22 . Conductive lines  21  are connected to controller  93  by using plurality of first conductive lines  24 , second conductive lines  25 , third conductive lines  26  and fourth conductive lines  27 . While  FIG. 5  shows first conductive lines  24  at the right bottom of touch panel  91 , first conductive lines  24  can be placed anywhere on touch panel  91 . While  FIG. 5  shows second conductive lines  25  at the right top of touch panel  91 , second conductive lines  25  can be placed anywhere on touch panel  91 . While  FIG. 5  shows third conductive lines  26  at the right top of touch panel  91 , third conductive lines  26  can be placed anywhere on touch panel  91 . While  FIG. 5  shows fourth conductive lines  27  at the left bottom of touch panel  91 , fourth conductive lines  24  can be placed anywhere on touch panel  91 . First conductive lines  24 , second conductive lines  25 , third conductive lines  26 , and fourth conductive lines  27  can be all placed in the same area of touch panel  91 . 
         [0031]      FIG. 7  shows the process of making a touch panel using metal meshes. The process can be used for any embodiment explained above. In step  100 , metal lines are placed on a substrate in the first direction. In step  101  an insulation layer is placed over the substrate. In step  102 , a mask is placed on insulation layer. In step  103 , unmasked insulation is removed such that discrete insulators stay only in the areas where insulation is desired. In step  104 , metal lines are placed on the substrate in the second direction. The second direction is substantially perpendicular to the first direction. After step  104 , the substrate has metal lines in the first direction and in the second direction and they are insulated from each other as shown in  FIG. 3  or  FIG. 4 . In step  105  and  106 , a mask is used to produce a pattern on the substrate. 
         [0032]      FIG. 8  shows the cross sectional view of an embodiment wherein conductive electrode assemblies  151  are placed on one surface of substrate  150 . Conductive electrode assemblies  152  are placed on the other surface of substrate  150 . Substrate  150  is made of an insulating material such that conductive electrode assemblies  151  and conductive electrode assemblies  152  are insulated from each other. Conductive electrode assemblies  151  and conductive electrode assemblies  152  can be built using metal mesh material or solid metal or transparent conductive material. 
         [0033]      FIG. 9  shows the cross sectional view of another embodiment wherein touch circuit  153  is placed on one side of substrate  150 . This is a single layer structure. For example substrate  150  may be a cover glass for a device and touch circuit  153  may be placed on one surface of cover glass  150 . Cover glass  150  can be a chemically strengthened or tempered glass. Cover glass  150  can be either a flat cover glass or a curved cover glass. Touch circuit  153  includes conductive electrode assemblies  2 , conductive electrode assemblies  3 , conductive lines  7 , conductive lines  8 , insulators  9 , conductive lines  81 ,  82 ,  83  and  84  as shown in  FIG. 1 . In this embodiment, conductive electrode assemblies  2  and conductive electrode assemblies  3  can be built of transparent or opaque material. Conductive lines  7  and conductive lines  8  are built using transparent material. Conductive lines  81 ,  82 ,  83  and  84  can be made of transparent or opaque material. 
         [0034]      FIG. 10  shows the cross sectional view of another embodiment wherein black mask  154  is placed on a surface of substrate  150  such that it is placed in the periphery region of substrate  150 . Supporting layer  155  is placed on the same surface as black mask  154 . Touch circuit  156  is placed on supporting layer  155  and black mask  154 . Touch circuit  156  includes conductive electrode assemblies  2 , conductive electrode assemblies  3 , conductive lines  7 , conductive lines  8 , insulators  9 , conductive lines  81 ,  82 ,  83  and  84  as shown in  FIG. 1 . In this embodiment, conductive electrode assemblies  2  and conductive electrode assemblies  3  can be built of transparent or opaque material. Conductive lines  7  and conductive lines  8  are built using transparent material. Conductive lines  81 ,  82 ,  83  and  84  can be made of transparent or opaque material. Conductive lines of  FIG. 1  are usually made of metal lines but alternatively can be made of transparent conductive material. If conductive lines  81 ,  82 ,  83  and  84  are made of metal, and these lines are large enough then they will be visible to the naked eye. Therefore connecting lines  81 ,  82 ,  83  and  84  are placed under black mask  154  such that connecting lines cannot be visible to a user. 
         [0035]      FIG. 11  shows the cross sectional view of another embodiment wherein black mask  157  is placed on a surface of substrate  150  such that it is placed in the periphery region of substrate  150 . Supporting layer  161  is placed on the same surface as black mask  157 . Touch circuit  158  is placed on supporting layer  155  and black mask  154 . Insulating layer  159  is placed on touch circuit  158 . Another touch circuit  160  is placed on insulating layer  159 . Touch circuit  158  includes conductive electrode assemblies  2  and connection lines  82  and  84  as shown in  FIG. 1 . Touch circuit  160  includes conductive electrode assemblies  3  and connection lines  81  and  83 . Connecting lines  81 ,  82 ,  83  and  84  are usually made of metal lines. If the size of these lines are large enough then they may be visible to the naked eye. Therefore connecting lines  81 ,  82 ,  83  and  84  are placed under black mask  157  such that connecting lines cannot be visible. 
         [0036]      FIG. 12  shows the cross sectional view of another embodiment wherein black mask  164  is placed on a surface of substrate  160  such that it is placed in the periphery region of substrate  160 . Supporting layer  165  is placed on the same surface as black mask  164 . Touch circuit  166  is placed on supporting layer  165  and black mask  164 . Touch circuit  166  includes conductive electrodes, assemblies  2 , conductive assemblies  3 , conductive lines  7 , conductive lines  8  and connecting lines  82  and  84  of  FIG. 1 . Connecting lines  82  and  84  of  FIG. 1  are usually made of metal lines. If the size of these lines are large enough they will be visible. Therefore connecting lines are placed under black mask  164  such that connecting lines cannot be visible. An antireflective coating  163  is placed on the other surface of substrate  150 . In an alternative embodiment, the antireflective coating  163  can be placed between substrate  160  and supporting layer  165 .