Patent Publication Number: US-2013229379-A1

Title: Touch sensor and associated manufacturing method

Description:
The present invention concerns a touch sensor, in particular for a touch-control screen. 
     It also concerns a method of manufacturing that touch sensor. 
     In general terms, the present invention concerns the field of touch sensors, and in particular multi-contact touch sensors enabling simultaneous detection of several zones of contact with the touch sensor of an object, such as a stylus or a user&#39;s finger. 
     When this touch sensor is associated with a display screen, a touch-control screen is constituted making it possible, according to the elements displayed on the display screen (graphical object, icon, image) to generate actions for controlling an item of software or equipment and/or for manipulating the displayed elements by taking into account the data acquired from the transparent touch sensor. 
     Such a touch sensor is known, which is described in particular in the document EP 1 719 047. 
     This touch sensor comprises a first layer comprising a first series of parallel conductive tracks and a second layer comprising a second series of parallel conductive tracks, the two layers being superposed against each other such that the first series of parallel conductive tracks is perpendicular to the second series of parallel conductive tracks. 
     A row/column array of conductive tracks is this obtained, making it possible, through detection of a variation in impedance (resistance, capacitance) at the location of each crossing zone of conductive tracks, to detect the presence of an object (stylus, user&#39;s finger) on the touch sensor, opposite that crossing zone. 
     This row/column array of conductive tracks thus constitutes the touch detection zone of the touch sensor. 
     Conventionally, the first layer is formed from a plate of glass on which is formed the first series of parallel conductive tracks. 
     The second layer is formed from a flexible film, for example of PET (acronym for Polyethylene Terephthalate), cut out to the dimensions of the glass plate and on which is formed the second series of parallel conductive tracks. 
     A network of conductive tracks is also formed on the glass plate and on the flexible film to connect the parallel conductive tracks to a connecting member forming an interface with an external processor. 
     An insulating protective layer is then deposited on the network of conductive tracks to provide the electrical insulation thereof. 
     A double-sided adhesive layer is cut out to the dimensions of the flexible film and of the glass plate, then deposited on the glass plate to enable the subsequent bonding of the flexible film to that glass plate and out form the row/column array of the conductive tracks of the touch detection zone of the touch sensor. 
     This manufacturing method includes a high number of operations, with manipulations of different parts which are difficult to automate. 
     Also known in document U.S. Pat. No. 5,159,159 is a method of manufacturing a touch sensor in which the two series of parallel conductive tracks are formed on two adjacent faces of a foldable insulating substrate. 
     This insulating substrate is folded face against face to form the row/column array constituting the touch detection zone, that is to say the active zone of the touch sensor. 
     However, such a touch sensor also comprises a network of conductive tracks which extend in the vicinity of the active zone and constitute, in the plane of the touch sensor, an inactive zone 
     It is then necessary to find a compromise between the size of those inactive zones, which unnecessarily increases the size of the touch sensor, and which must however be sufficient to enable the disposition of the network of conductive tracks, linking the conductive tracks of the active zone to a processor for controlling the touch sensor. 
     Thus, when that touch sensor is associated with a display screen, a frame is for example provided to mask the inactive part of the touch sensor, leading to a greater dimension for the touch screen than that of the active zone proper. 
     The present invention aims to solve at least one of the aforesaid drawbacks and to provide a method of manufacturing a touch sensor and such a touch sensor without dimension constraint of the inactive zones disposed along the edges of the touch sensor. 
     To that end, according to a first aspect, the present invention concerns a touch sensor, comprising an active zone comprising a first series of parallel conductive tracks and a second series of parallel conductive tracks, the second series of parallel conductive tracks being perpendicular to the first series of parallel conductive tracks, said first and second series of parallel conductive tracks being formed on an insulating substrate having a first face comprising said first series of parallel conductive tracks and a second face comprising said second series of parallel conductive tracks, the insulating substrate being folded and said second face being disposed facing said first face. 
     According to the invention, the insulating substrate further comprises a network of conductive tracks connecting the first and second series of parallel conductive tracks to a zone for connection with an external processor, the network of conductive tracks extending in at least one edge zone disposed between the active zone and a side of the insulating substrate, the insulating substrate comprising a fold line between the active zone and said at least one edge zone. 
     Forming an insulating substrate by folding enables simple provision of a row/column array of conductive tracks forming a touch detection zone in the touch sensor. 
     The network of conductive tracks enabling management of the signals provided or read on the row/column array of the parallel conductive tracks may be formed in one piece on the insulating substrate up to the zone for connection with an external processor. 
     Thanks to the fold line between the active zone and an edge zone bearing conductive tracks of the network, the touch sensor has, after folding of the edge zones, a flat surface of smaller size, able to substantially match the active zone proper of the touch sensor or to adapt to the dimensions of a given display screen. 
     The size of the active surface of such a touch sensor is thus improved relative to the dimension or bulk in a plane of that touch sensor. 
     It is possible that surface occupied by the touch sensor in a plane may be substantially equal to the active zone proper of that touch sensor. 
     Furthermore, since the edge zones bearing the network of conductive tracks may be folded, their width may be greater to facilitate the disposition of the network of conductive tracks. 
     In practice, the insulating substrate is a film of thickness comprised between 20 and 200 μm and preferably between 25 and 50 μm, enabling a touch sensor of small thickness to be formed by folding. 
     In a practical embodiment of the invention, the insulating substrate comprises a wing forming an extension on one side of the insulating substrate, adapted to form the zone for connection with an external processor, the insulating substrate comprising a fold line between the active zone and an edge disposed between the active zone and said side of the insulating substrate. 
     Thus, the connection zone of the touch sensor may be formed as a single piece in the insulating substrate. 
     Furthermore, the connection zone formed by the wing of the insulating substrate may be folded under the active zone of the touch sensor, so enabling direct mounting of that touch sensor on an electronic board. 
     According to an advantageous embodiment of the invention, the insulating substrate further comprises control circuits associated with each conductive track of the first and second series of parallel conductive tracks, the network of conductive tracks extending between the control circuits and the zone for connection with an external processor. 
     By thus placing control circuits on the insulating substrate which are associated with each conductive track of the row/column array, it is possible to reduce the number of conductive tracks connected to an external processor, which are necessary for the provision and/or the reading of the electrical signals on each conductive track of the row/column array. 
     In practice, the first and second series of conductive tracks and the network of conductive tracks are produced from metal, such as silver or copper. 
     The use of a metallic material for producing the conductive tracks of the touch sensor is particularly advantageous, provided those conductive tracks can be folded with the insulating substrate without loss of conductivity nor wear over time despite the curvature imposed upon those conductive tracks at the location of the insulating substrate fold lines. 
     In a practical embodiment, making it possible in particular to maintain transparency for the touch sensor in its active zone, each conductive track of the first and second series of parallel conductive tracks comprises at least one metal wire of width less than 20 μm. 
     In order to give each conductive track sufficient resistivity, each conductive track comprises several metal wires extending substantially parallel to each other and connected together at one of their ends. 
     According to a second aspect the present invention concerns a method of manufacturing a touch sensor comprising an active zone comprising a first series of parallel conductive tracks and a second series of parallel conductive tracks, said second series of parallel conductive tracks being perpendicular to said first series of parallel conductive tracks. 
     According to the invention, this manufacturing method comprises the following steps:
         forming the first and second series of parallel conductive tracks respectively on adjacent zones of an insulating substrate;   forming a network of conductive tracks connecting the first and second series of parallel conductive tracks to a zone for connection with an external processor, the network of conductive tracks extending in at least one edge zone disposed between said active zone and a side of the insulating substrate;   depositing an insulating film on the network of conductive tracks;   folding the insulating substrate along a fold line extending between the two adjacent zones; and   folding the insulating substrate along a fold line extending between the active zone and said at least one edge zone.       

     Thus manufacturing method enables a row/column array of conductive tracks in a touch sensor to be formed in a particularly simplified manner. 
     This method is particularly advantageous relative to the manufacturing techniques in which the connection zone is an added-on part, fastened to the touch detection zone and thus requiring precise positioning in the alignment of the conductive tracks located at the junction with the connection zone. 
     The network of conductive tracks may thus be formed before folding. An insulating film also makes it possible, before folding, to avoid any contact with the conductive tracks of that network. 
     In an advantageous embodiment of the invention, it further comprises a step of forming control circuits on the insulating substrate which are each associated with each conductive track of the first and second series. 
     It is thus possible to reduce the number of conductive tracks of the network for connection with an external processor. 
     Lastly, according to a third aspect, the present invention concerns a touch-control screen, comprising a touch sensor in accordance with the invention and a display screen which are superposed. 
     This touch-control screen has features and advantages which are similar to those described in relation to the touch sensor. 
     In practice, the active zone of the touch sensor extends above the display screen, the edge zone or zones being folded along an edge of said display screen or between the touch sensor and the display screen. 
     Thus, the touch sensor and its active surface may adapt as well as possible to the various dimensions of the display screens. 
     More particularly, when the touch sensor comprises a wing forming an extension on one side of the insulating substrate, and that is adapted to form the zone for connection with an external processor, that wing is folded under the display screen, thus enabling the touch sensor to be directly connected to an electronic system for management of that sensor disposed on the electronic board placed under the touch-control screen. 
     Still other particularities and advantages of the invention will appear in the following description. 
    
    
     
       In the accompanying drawings, given by way of non-limiting example: 
         FIGS. 1 and 2  are diagrammatic views illustrating the manufacture of a touch sensor in accordance with a first embodiment of the invention; 
         FIG. 3  is a similar view to  FIG. 2  illustrating a touch sensor according to a second embodiment of the invention; 
         FIGS. 4A and 4B  diagrammatically illustrate a first touch sensor structure in accordance with the invention; 
         FIGS. 5A and 5B  diagrammatically illustrate a second touch sensor structure in accordance with the invention; 
         FIG. 6  is a diagrammatic illustration in cross-section of a touch-control screen according to a first embodiment of the invention; 
         FIG. 7  is a diagrammatic illustration in cross-section of a touch-control screen according to a second embodiment of the invention; 
         FIG. 8  is a diagrammatic illustration in cross-section of a touch-control screen according to a third embodiment of the invention; 
         FIGS. 9 and 10  are diagrammatic views illustrating the manufacture of a touch sensor in accordance with a third embodiment of the invention; 
         FIG. 11  is a similar view to  FIG. 9  illustrating the manufacture of a touch sensor according to a fourth embodiment of the invention; 
         FIG. 12  is a diagrammatic cross-section view of a touch-control screen according to a fourth embodiment of the invention; and 
         FIG. 13  is an algorithm illustrating the steps of a method of manufacturing a touch sensor according to an embodiment of the invention. 
     
    
    
     A description will first of all be made with reference to  FIGS. 1 and 2  of a touch sensor according to a first embodiment of the invention. 
     In general terms, such a touch sensor  10  comprises a touch detection zone, enabling for example multi-contact detection, that is to say adapted to simultaneously detect several points of pressing or of pressure applied to the surface of the touch sensor  10 . 
     To that end, as illustrated in  FIG. 1 , the touch sensor  10  comprises on an insulating substrate  11   a  first series of parallel conductive tracks  12  and a second series of parallel conductive tracks  13 . 
     The first series of parallel conductive tracks  12  is formed on a first zone  11   a  of the insulating substrate. 
     The second series of parallel conductive tracks  13  is formed on a second zone  11   b  of the insulating substrate  11 , the first zone  11   a  and the second zone  11   b  being adjacent on the insulating substrate  11 . 
     As illustrated in  FIG. 2 , the insulating substrate  11  of the touch sensor  10  is folded along a fold line  11   c , extending between the two adjacent zones  11   a ,  11   b.    
     In this folded position of the insulating substrate  10 , the first zone  11   a  thus constitutes a first face  11   a  of the insulating substrate comprising the first series of parallel conductive tracks  12  and the second zone  11   b  constitutes a second face  11   b  of the insulating substrate  11  comprising the second series of parallel conductive tracks  13 . 
     In the folded position, the second face  11   b  of the insulating substrate  11  is thus disposed facing the first face  11   a  of the insulating substrate  11  such that the first series of parallel conductive tracks  12  and the second series of parallel conductive tracks  13  are also disposed face-to-face. 
     The disposition of the first series of parallel conductive tracks  13  is such that in folded position, the first series of parallel conductive tracks  12  is perpendicular to the second series of parallel conductive tracks  13 . 
     A touch detection zone is thus formed in the touch sensor  10  at the location of the first and second faces  11   a ,  11   b  disposed facing each other. 
     More particularly, the first series of parallel conductive tracks  12  and the second series of parallel conductive tracks  13  constitute a row/column array of conductive tracks thus defining crossing zones or points at the location of which the detection of a variation in impedance makes it possible to detect the presence of an object opposite that crossing zone. 
     Reference may advantageously be made to the description of document EP 1 719 047 for a more detailed description of the detection of the pressing points on such a touch sensor  10 , in particular by detection of the variation in the resistance at the location of pressing point. 
     As clearly illustrated in  FIGS. 1 and 2 , the insulating substrate  11  is preferably of substantially rectangular shape, the two adjacent zones  11   a ,  11   b  being separated by a fold line  11   c  extending widthwise of the insulating substrate  11 . 
     The first series of parallel conductive tracks  12  is disposed in a first direction on the first zone  11   a  of the insulating substrate  11  and the second series of parallel conductive tracks  13  is disposed in a second direction, perpendicular to the first direction, on the second zone  11   b  of the insulating substrate  11 . 
     The insulating substrate  11  is thus folded widthwise, along the fold line  11   c.    
     In addition to the row/column array so constituted, the touch sensor  10  also comprises means making it possible to manage the operation of the touch detection zone, and in particular to provide an electrical signal or read such an electrical signal at the terminals of the first series of parallel conductive tracks  12  and of the second series of parallel conductive tracks  13 . 
     To that end, the touch sensor  10  comprises a connection zone  20  adapted to be connected with an external processor (not illustrated) in order to manage the operation of the touch sensor  10 . 
     In the embodiment as illustrated in  FIGS. 1 and 2 , the insulating substrate comprises a wing  21  thus forming an extension on one side  11   d  of the insulating substrate  11 . 
     Here, the wing  21  is integrally formed in the material constituting the insulating substrate  11  and forms an extension on one edge  11   d  of the insulating substrate  11 , corresponding to an edge which extends widthwise of that insulating substrate  11 . 
     In a manner that is in no way limiting, in this embodiment, the wing  21  thus constitutes a substantially rectangular tab extending in the middle of the edge  11   d  of the insulating substrate  11 . 
     It is to be noted with reference to  FIG. 2  that when the insulating substrate  11  is folded along the fold line  11   c , that connection zone  20  remains visible and extends beyond the first face  11   a  and second face  11   b  opposite the touch sensor  10 . 
     This connection zone  20  thus enables the subsequent connection of the touch sensor  10  to a microprocessor or other element necessary for its operation. 
     The insulating substrate  11  further comprises a network of conductive tracks  22  which extends between each conductive track of the first and second series of conductive tracks  12 ,  13  and the connection zone  20 . 
     This network of conductive tracks  22  thus enables the passage of an electric current for the supply of each conductive track or for reading an electrical signal on each conductive track of the touch detection zone. 
     In such a touch sensor  10 , and according to the resolution and the size of the touch sensor, a very high number of parallel conductive tracks  12 ,  13  is provided. For example, the first series of parallel conductive tracks  12  may comprise 2000 tracks whereas the second series of parallel conductive tracks  13  may comprise 1500 tracks. 
     The embodiment described in  FIGS. 1 and 2  thus requires the formation of 3500 conductive tracks  22  for the operation of the touch sensor  10  so formed. 
     Of course, this number of conductive tracks  12 ,  13 ,  22  is given as being in no way limiting and solely to illustrate the high number of conductive tracks to form on such a touch sensor. 
     In order to simplify the network of conductive tracks  22 , it is possible, as illustrated in  FIG. 3 , to provide control circuits  23 ,  24  on the insulating substrate  11  which are respectively associated with each conductive track of the first and second series of parallel conductive tracks  12 ,  13 . 
     These control circuits  23 ,  24  constitute drivers such that the network of conductive tracks  22  may be simplified when only conductive tracks  22  extending between the control circuits  23  and  24  and the connection zone  20  are necessary for the operation of the touch sensor  10 . 
     Thus, when the row/column array is scanned, the control circuits  23 ,  24  make it possible to control the supply of electric current to a series of parallel conductive tracks, and for example the first series of parallel conductive tracks  12 , as well as the measurement of an electrical parameter on the other series of parallel conductive tracks, and in this example, of the second series of parallel conductive tracks  13 . 
     The network of conductive tracks  22  enabling the control circuits  23 ,  24  to be supplied and controlled may thus be simplified in terms of the number of conductive tracks  22 . 
     Whatever the embodiment illustrated in  FIG. 1  or  3 , it is necessary to provide an insulating film (not shown) disposed on the network of conductive tracks  22  such that when the insulating substrate  11  is folded along the fold line  11   c , the conductive tracks  22  of the network do not come into contact with each other, disturbing the passage of the electrical signals. 
     In  FIGS. 4A and 4B  a first embodiment for manufacturing a touch sensor in accordance with the invention has been illustrated, also corresponding to the embodiment described in  FIG. 1  or  3 . 
     Thus, in this manufacturing embodiment, the fold line  11   c  extends widthwise of the insulating substrate  11  and, after folding as illustrated in  FIG. 4B , corresponds to an edge of the touch sensor  10  extending widthwise of the touch sensor  10  of substantially rectangular shape. 
     As clearly illustrated in  FIG. 4A  the connection zone  20  thus extends on an opposite edge  11   d  to the edge constituted by the fold line  11   c  of the touch sensor  10 . 
     Alternatively, as illustrated in  FIGS. 5A and 5B , the fold line  11   c  of the insulating substrate  11  may extend widthwise of the insulating substrate  11  and, after folding, constitute a longitudinal edge  11   c  of the touch sensor  10 . 
     In this manufacturing embodiment, the connection zone  20  extends on an edge  11   d  corresponding to the width of the touch sensor  10  and which is perpendicular to the longitudinal edge constituted by the fold line  11   c  of the insulating substrate  11 . 
     Of course, these example embodiments are not limiting, it being possible for the connection zone  20  to extend at any other location on an edge of the touch sensor  10 . 
     Furthermore, different embodiments of a touch-control screen have been illustrated in  FIGS. 6 to 8 . 
     This touch-control screen  30  comprises a display screen, disposed here under a touch sensor  10  corresponding to a touch sensor as described above with reference to  FIGS. 1 to 3 . 
     In such a structure, it is thus necessary for the touch sensor  10  to be transparent in order to enable the elements displayed on the underlying display screen  31  to be viewed. 
     Of course, other embodiments of a touch-control screen based on a touch sensor  10  as described above could be employed. 
     In particular, the display screen could be disposed above the touch sensor  10  provided that the display screen is sufficiently flexible to enable transmission of a press made on the display screen to the surface of the underlying touch sensor. 
     In such a case, the touch sensor is not necessarily transparent. 
     In the first embodiment illustrated in  FIG. 6 , a series of spacers  32  (also called spacer dots) is disposed between the first and second faces  11   a ,  11   b  facing the folded insulating substrate  11 . 
     These spacers  32  so disposed between the first series of parallel conductive tracks  12  and second series of parallel conductive tracks  13  make it possible to maintain a space between the two faces  11   a ,  11   b  of the insulating substrate  11 , in order to avoid the parallel conductive tracks  12 ,  13  being placed in contact. 
     This series of spacers  32  thus enables the parallel conductive tracks  12 ,  13  of the row/column array in the touch detection zone of the touch sensor  10  to be kept insulated by a layer of air. 
     It is also possible as illustrated in the second embodiment of  FIG. 7 , to furthermore add an inner resistive layer  33  disposed between the first and second faces  11   a ,  11   b  opposite the folded insulating substrate  11 . 
     As is known in the state of the art, such an inner resistive layer  33  makes it possible to eliminate the re-passage of the current through the row/column array of the touch sensor  10 , and thus eliminate masking effects or ghosts. 
     In a third embodiment as illustrated in  FIG. 8 , the inner resistive layer  33  and the series of spacers  32  may be replaced by an inner layer  34  of variable resistance also disposed between the first and second faces  11   a ,  11   b  opposite the folded insulating substrate  11 . 
     This inner layer  34  has the particularity of being formed from a material of which the resistance varies according to the pressure applied to that material such that it is also possible by measuring the variation in the resistance, to evaluate the pressing force applied on the touch sensor at a pressing point thanks to the variation in the resistance in the inner layer  34 . 
     The variable resistance inner layer  34  may be produced from known materials such as a contact pressure sensitive polymer layer or an FSR ink (FSR standing for “Force Sensitive Resistor”), or even a gel or foam with a conductive particle filler. 
     This variable resistance inner layer  34  makes it possible both to insulate the parallel conductive tracks  12 ,  13  of the row/column array, to eliminate the re-passage of the current through that array and to evaluate the pressing force at the pressing point or points on the touch sensor. 
     When the touch sensor  10  is adapted, as in this embodiment, to be disposed above a display screen  31 , it may further comprise a decorative layer  35  (also called a coverlens). 
     This decorative layer  35  may thus be bonded onto an outside face of the insulating substrate  11 , and for example here on the back of the second face  11   b  of the insulating substrate  11  bearing the second series of parallel conductive tracks  13 . 
     With reference to  FIGS. 9 and 10  a third embodiment of a touch sensor will now be described. 
     This touch sensor has similar features to those of the embodiments described above with reference to  FIGS. 1 and 2 , the parts in common bearing the same reference numbers. 
     This touch sensor  10  is modified mainly as regards the constitution of the first and second series of parallel conductive tracks  12 ,  13 . 
     Here, the first and second series of conductive tracks  12 ,  13  are produced from metal, such as silver or copper. 
     In the example embodiment described below, the metal used is for example silver. 
     This same material is used to form the network of conductive tracks  22  connecting the parallel conductive tracks  12 ,  13  to the connection zone  20 . 
     The use of such a metal material, such as silver, instead of ITO to form the network of conductive tracks  22  makes it possible to give that network of conductive tracks  22  satisfactory properties of bending and durability over time, in particular at the location of the fold lines of the insulating substrate  11 , and in particular the fold line  11   c  enabling the two adjacent faces  11   a ,  11   b  of the insulating substrate  11  to be disposed facing each other. 
     When a transparent touch sensor is formed, the network of conductive tracks  22  may be opaque provided that those conductive tracks are placed outside the active zone proper of the touch sensor  10 . 
     Thus, the constitution of that network of conductive tracks  22  from silver, an opaque material, is not a drawback for producing a transparent touch sensor. 
     On the other hand, the parallel conductive tracks  12 ,  13  of the active zone of the touch sensor  10  must be invisible to preserve the transparency of the touch sensor  10 . 
     In practice, each conductive track  12 ,  13  comprises one or more metal wires  12   a ,  13   a  of width less than 20 μm. 
     Preferably, the width of each metal wire  12   a ,  13   a  produced from silver is of the order of 10 μm. 
     In order to obtain the desired resistivity for each conductive track  12 ,  13  of the active zone of the touch sensor  10 , the conductive tracks  12 ,  13  of the touch detection zone are constituted by several metal wires  12   a ,  13   a  linked together at one end in the form of a comb. 
     The number of metal wires  12   a ,  13   a  so extending parallel to each other to constitute a conductive track  12 ,  13  depends on the desired resistivity, and is comprised between 3 and 5. 
     In a manner which is in no way limiting, in the example illustrated in  FIGS. 9 and 10 , the number of metal wires  12   a ,  13   a  constituting each conductive track  12 ,  13 , is four. 
     In order to avoid the moiré effect and improve the visual comfort of the user, the metal wires  12   a ,  13   a  may be disposed in saw tooth configuration, parallel to each other. 
     By way of example, by disposing several metal wires  12   a ,  13   a  parallel to each other, with a predetermined spacing between each metal wire  12   a ,  13   a , the total width of an active track  12 ,  13  may be comprised between 0.5 and 3 mm, each metal wire  12   a ,  13   a  having a width of the order of 10 μm. 
     Thus, the transparency of the touch sensor  10  in the active zone is preserved. 
     By virtue of the possible bending of the conductive tracks thus formed from a metallic material, and as illustrated in  FIG. 10 , the insulating substrate  11  may comprise fold lines, in addition to the fold line  11   c  disposed between the two adjacent faces  11   a ,  11   b  of the touch sensor already described above. 
     Thus, as illustrated in  FIG. 10  in this embodiment, the insulating substrate  11  comprises for example three other fold lines  11   e ,  11   f ,  11   g.    
     These fold lines  11   e ,  11   f ,  11   g  extend between the active zone bearing the first series of conductive tracks  12  and the second series of conductive tracks  13  and an edge zone disposed between that active zone and one side of the insulating substrate  11 . 
     As the network of conductive tracks  22  extends in those edge zones, those zones may be folded at each fold line  11   e ,  11   f ,  11   g.    
     Thus, as clearly illustrated in  FIG. 9 , when the insulating substrate  11  comprises a wing  21  forming an extension on one side lid of the insulating substrate  11 , to form the connection zone  20 , that insulating substrate  11  comprises a fold line  11   g  between the active zone and an edge zone disposed between that active zone and the side lid of the insulating substrate  11 . 
     The network of conductive tracks  22  disposed in that edge zone may thus be folded under the touch sensor  10 . 
     In another alternative as illustrated in  FIG. 10 , it is possible for the connection zone  20  of the network of conductive tracks  22  not to be formed on an extension wing of the insulating substrate  11 , the edge  11   d  of the insulating substrate  11  not being cut out. 
     Thanks to the folding of that edge zone between the active zone and the edge  11   d  of the insulating substrate, all the conductive tracks  22  extending in the connection zone  20  may be disposed under the touch sensor  10  to enable direct connection to a driver of the sensor, mounted on an electronic board. 
     In general terms, the fold lines  11   e ,  11   f ,  11   g  extend substantially parallel to one side of the insulating substrate  11 . 
     In this embodiment, a fold line  11   g  extends parallel to the side  11   d  of the insulating substrate  11 , corresponding to the width of the insulating substrate  11 . 
     Two other fold lines  11   e ,  11   f  extend parallel to the longitudinal sides of the insulating substrate  11 . 
     Furthermore, the disposition of those fold lines  11   e ,  11   f ,  11   g  between the active zone and each side of the insulating substrate  11  may be variable, and in particular those fold lines  11   e ,  11   f ,  11   g  may extend at a variable distance from the active zone proper. 
     It will be noted that advantageously, as the edge zones bearing the network of conductive tracks  22  can be folded, the dimension of those edge zones is no longer a constraint. 
     In particular, each edge zone may have any width, taken in a direction perpendicular to the side of the insulating substrate  11 , which width may be adapted to the number of tracks of the network of conductive tracks  22  disposed on that edge zone, parallel to that same side of the insulating substrate  11 . 
     In  FIG. 11 , a fourth embodiment of such a touch sensor has been illustrated. 
     This fourth embodiment is identical in every way to those described above in relation to  FIG. 9 , except for the formation of the network of conductive tracks  22  which has been modified. As described above in relation to  FIG. 3 , control circuits (drivers)  23 ,  24  are integrated onto the insulating substrate  11 , so limiting the number of conductive tracks of the network of conductive tracks  22  which extends between the control circuits  23 ,  24  and the zone  20  for connection with an external processor. 
     As illustrated in  FIG. 12 , when this touch sensor  10  is juxtaposed against a display screen  31  to constitute a touch-control screen, the edge zones bearing the network of conductive tracks  22  may be folded along the edges of the display screen  31 . 
     As clearly illustrated in  FIG. 12 , when the touch sensor  10  comprises a wing  21  forming an extension on one side  11   d  of the insulating substrate  11 , as illustrated in  FIG. 9 , that wing  21  may be folded under the display screen  31  such that the zone  20  for connection with an internal processor is disposed under the display screen  31  and may be directly connected to an electronic board  32  bearing the external control processor of the touch sensor  10 . 
     A method of manufacturing such a touch sensor will now be described with reference to  FIG. 13 . 
     The first step of the method of manufacturing the touch sensor  10  consists of a step S 1  of forming the first and second series of parallel conductive tracks  12 ,  13  on adjacent zones  11   a ,  11   b  of an insulating substrate  11 . 
     Preferably, this insulating substrate is a film of small thickness, comprised for example between 20 and 200 μm, and preferably between 25 and 50 μm. 
     This small thickness must enable easy folding of that insulating substrate  11 . 
     In a manner that is not limiting, the insulating substrate  11  is produced from a transparent PET film in order to ensure the transparency of the touch sensor  10 . 
     According to a first manufacturing embodiment, at the step S 1  of forming the parallel conductive tracks  12 ,  13  later constituting the touch detection zone of the touch sensor  10 , a technique of etching a homogenous conductive layer deposited in advance on the insulating substrate  11  is implemented. 
     This homogenous conductive layer may for example be formed of ITO (acronym for Indium Tin Oxide) which has the particularity of being transparent. 
     As described above in relation with  FIGS. 9 to 12 , the material used may alternatively be silver. 
     It is possible in that homogenous conductive layer to form, by etching, all the parallel conductive tracks  12 ,  13  of the touch zone as well as the conductive tracks  22  of the connection network, up to the connection zone  20 . 
     Alternatively, and as illustrated in  FIG. 13 , only the parallel conductive tracks  12 ,  13  may be formed by the technique of etching the homogeneous conductive layer, the network of conductive tracks  22  being formed by a printing technique, of the ink jet printing type or by vacuum deposition. 
     Alternatively, according to a second manufacturing embodiment, all the parallel conductive tracks  12 ,  13  and the network of conductive tracks  22  may be formed by a printing technique. 
     The printing may be formed by printing a conductive ink on the insulating substrate of PET type, deposited by ink jet or vacuum deposition. 
     When the conductive tracks  12 ,  13  of the active zone of the touch sensor  10  are formed from several silver metal wires, of width of the order of 10 μm, the deposition of those metal wires is preferably carried out by ink jet printing or laser deposition. 
     A technique for manufacturing conductive tracks formed from one or more metal wires of very small width, and in particular less than 80 μm, is described in particular in the document FR 2 925 717. 
     Taking into account the folding of the insulating substrate  11 , the materials used (conductive layer to etch or ink to print) to form the network of conductive tracks  22  by printing or etching must be sufficiently flexible to maintain their electrical properties despite the fold line  11   c  of the insulating substrate  11 . 
     In general terms, the radius of curvature of the insulating substrate  11  in the fold zone, which is proportional to the thickness of the touch sensor, must be determined according to the tolerance of the conductive ink at the location of that fold zone. 
     A conductive track formed from conductive ink must therefore be able to be folded with that radius of curvature without breaking. 
     By way of non-limiting example, if the insulating substrate is formed from a PET film of 50 μm thickness, and an insulating film is disposed on the network of conductive tracks  22  with a thickness of the order of 100 μm, the conductive ink used to form the network of conductive tracks  22  must be able to be folded without modifying its electrical properties with a radius of curvature substantially equal to 50 μm. 
     Forming the network of conductive tracks  22  on the insulating substrate  11  enables integral formation of those conductive tracks which extend between each parallel conductive track  12 ,  13  of the row/column array up to the wing  21  forming the connection zone  20  of the touch sensor. 
     This production technique enables the manufacturing of the touch sensor to be simplified, in particular in that connection zone  20 . 
     Furthermore, at the step of forming the conductive tracks  22 , is also possible to form control circuits  23 ,  24  on the insulating substrate  11  such as are described earlier with reference to the embodiment illustrated in  FIG. 3 . 
     The control circuits  23 ,  24  so printed at the location of each parallel conductive track  12 ,  13  of the row/column array may then be managed by an addressing signal from a multiplexing system, requiring fewer conductive tracks  22 . 
     After step S 1  of forming the conductive tracks  12 ,  13  of the touch detection zone and the network of conductive tracks  22 , a step S 2  of printing the spacers  32  may be performed. 
     Alternatively or successively, a step S 3  of printing an inner resistive layer  33 ,  34  may be performed. 
     As described above with reference to  FIGS. 7 and 8 , this inner resistive layer may either be an inner resistive layer  33  of stable resistance, thus requiring the presence of spacers  32  to ensure spacing between the parallel conductive tracks  12 ,  13  in the touch detection zone, or be an inner resistive layer of variable resistance. 
     This printing steps S 2 , S 3  may be carried out by conventional printing techniques or by vacuum disposition on the insulating substrate  11 . 
     A step S 4  of printing adhesive elements is also carried out. 
     It makes it possible in particular to deposit an insulating film that is bonded on the network of conductive tracks  22  in order to ensure insulation of those conductive tracks  22  after folding of the insulating substrate  11 . 
     The insulating film may thus be formed from a double-sided adhesive layer enabling both to insulate the conductive tracks of the network of conductive tracks  22  and then to provide bonding at the location of the edges of the folded insulating substrate  11 . 
     These adhesive elements may be deposited using a mask placed on the insulating substrate  11  in order to limit the area coated with the adhesive, and in particular to avoid the disposition of adhesive and/or insulation on the touch detection zone. 
     Glue or adhesive may be deposited over the entirety of the edges of the insulating substrate  11  or else over only three or four edges of one of the zones  11   a  or  11   b  of the insulating substrate  11 , the deposit of glue or adhesive at the location of the fold line  11   c  of the insulating substrate  11  not being necessary. 
     Of course, the deposition of glue or adhesive may also be carried out along continuous lines or at separate points, for example at the corners of each adjacent zone  11   a ,  11   b  adapted to come to face each other. It should be noted that these different steps S 1 , S 2 , S 3 , S 4  may be carried out successively on the same continuous printing machine having several printing stations dedicated to each step of forming S 1  and printing S 2 , S 3 , S 4 . 
     The insulating substrate  11  is next cut out to the dimensions of the touch sensor  10  in a cutting-out step S 5 . 
     Further to this cutting-out step S 5 , the touch sensor thus has a substantially rectangular shape and is provided with its wing  21  in the connection zone  20 , already provided with the network of conductive tracks  22 . 
     A folding step S 6  next enables the insulating substrate  11  to be folded along a first fold line  11   c  in order to dispose the two faces  11   a ,  11   b  of the insulating substrate  11  face to face with each other. 
     A sealing step S 7  may be carried out in order to ensure bonding at the edges of the touch sensor  10 . 
     This sealing step S 7  may be carried out by passing the folded insulating substrate  11  through a rolling mill. 
     Optionally, the manufacturing method may also comprise a step S 8  of printing a decorative layer  35  on one of the visible faces of the folded insulating substrate  11 . 
     The touch sensor  10  so formed may then be bonded onto a display screen in order to form a touch-control screen as illustrated in  FIGS. 6 to 8 . 
     When a touch sensor  10  as illustrated in  FIGS. 9 to 11  is manufactured, the manufacturing method further comprises a step S 9  of folding of the edge zones. 
     As described above, when this folding step S 9  takes place, the touch sensor  10  is folded at the edge zones, along fold lines  11   e ,  11   f ,  11   g.    
     In particular, the edge zone bearing the connection zone  20  may be folded at a fold line  11   g  and be disposed under the display screen  31 . 
     The edge zones bearing a network of conductive tracks but not requiring any connection to an external processor may themselves be folded directly under the touch sensor  10 , that is to say between the surface of the touch sensor  10  and the display screen  31 , at the fold lines  11   e ,  11   f  of the touch sensor  10 . 
     In this case, the insulating substrate  11  is folded at the fold lines  11   e ,  11   f  through 180° in order to be disposed under the touch sensor  10 . 
     This type of fabrication may be used when the touch sensor  10  is not transparent or else if the edge zones so folded do not extend directly under the transparent active surface of the touch sensor  10 . 
     Alternatively, the edge zones bearing a network of conductive tracks not requiring any connection to an external processor may be folded along the edges of the display screen. 
     In this case, the insulating substrate is folded at the fold lines  11   e ,  11   f  through 90°, such that the edge zones extend along the display screen substantially perpendicularly to the active surface of the touch sensor  10 . 
     The manufacturing method so described makes it possible to manufacture a touch sensor at lower cost with a limited number of steps, in particular through implementing techniques of printing or etching the different electrical circuits on the same insulating substrate. 
     Thus, all the circuits necessary for the operation of the touch sensor may be formed in simultaneous or successive printing steps on the same insulating film. 
     This manufacturing method in particular makes it possible to dispense with the alignment of the conductive tracks in the connection zone. 
     When the touch sensor furthermore incorporates control circuits at the location of each conductive track  12 ,  13  of the row/column array, the limited number of conductive tracks  22  necessary for managing the operation of the touch sensor makes it possible to further reduce the production cost of such a touch sensor. 
     Of course, the present invention is not limited to the example embodiments described above. 
     Thus, in the embodiment described in relation with  FIGS. 9 and 10 , it is possible for the insulating substrate  11  to comprise only some of the fold lines  11   e ,  11   f ,  11   g  at the location of the edge zones, and for example only one fold line  11   g  at the location of an edge zone of the insulating substrate  11  bearing the connection zone  20 .