Abstract:
A method is disclosed of forming on a moving surface an auxiliary antenna for an RFID tag. The method includes the steps of providing a webstock of polymeric material including a conductive film, conveying the webstock with the moving surface, and applying the conductive film to the moving surface in a shape corresponding to the auxiliary antenna. The moving surface may include cardboard in a roll manufacturing process. Depending on the thickness of the auxiliary antenna the step of applying the conductive film may include cold or hot stamping. Apparatus for forming an auxiliary antenna for an RFID tag is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/852,352 filed Oct. 17, 2006, the disclosure of which is hereby incorporated herein by reference. 
     
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of Radio Frequency Identification (RFID) tags and in particular relates to a method and apparatus for manufacturing an auxiliary antenna for an RFID tag. 
       BACKGROUND OF THE INVENTION 
       [0003]    RFID tags are used to associate an object with information stored in the tag such as an identification code. The RFID tag is read via the principle of electromagnetic (EM) communication wherein an interrogator containing a transmitter generates an EM signal that is transmitted via an antenna associated with the interrogator to an antenna associated with the tag. In a passive tag the antenna receives a portion of the transmitted energy and through a rectifier generates DC power for operating a reply generation circuit. The reply generation circuit encodes the information stored in the tag into an EM reply signal that is radiated by the antenna. The radiated signal is received by the interrogator antenna and the information is decoded by the interrogator. 
         [0004]    A typical RFID tag module has a limited read range that may be less than 40 cm. To enhance performance of the tag when it is applied to an object it is known to couple a secondary or auxiliary antenna to the antenna on the tag. The auxiliary antenna may be larger than the tag antenna and may be located on the same object in close proximity to the tag antenna so that it is electromagnetically coupled thereto. 
         [0005]    Prior art methods for manufacturing such range enhancing or auxiliary antennas include etching of suitable conductors such as copper or aluminum on a substrate, and/or depositing conductive ink by means of screen printing, photographic or offset printing processes or the like. However, such manufacturing methods require too many steps and are relatively slow and expensive to apply. They are also not able to be incorporated into a cardboard roll manufacturing process. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with the present invention a process is provided for manufacturing an auxiliary antenna for an RFID tag that at least alleviates the above described disadvantages of the prior art. Further in accordance with the present invention, a process is provided for manufacturing an auxiliary antenna for an RFID tag that may be incorporated into a roll manufacturing process such as a cardboard roll manufacturing process. 
         [0007]    According to one aspect of the present invention there is provided a method of forming on a moving surface an auxiliary antenna for an RFID tag, said method including the steps of: 
         [0008]    providing a webstock of polymeric material including a conductive film; conveying said webstock with said moving surface; and 
         [0009]    applying said conductive film to said moving surface in a shape corresponding to said antenna. 
         [0010]    The moving surface may include cardboard in a roll manufacturing process. The webstock preferably is conveyed between a supply roller and a take up roller. 
         [0011]    The step of applying the conductive film may include cold stamping. Cold stamping may include applying adhesive to the moving surface. The adhesive may be applied substantially in a shape corresponding to the antenna. The adhesive may be applied via an offset printing roller. Cold stamping may include pressing the conductive film to the adhesive via a pressing roller and curing the adhesive with ultra violet light. 
         [0012]    The step of applying the conductive film may include hot stamping. Hot stamping may include applying adhesive to the conductive film and pressing the film to the moving surface via a pressing roller. The pressing roller may have a relief portion substantially in a shape corresponding to the antenna. Hot stamping may include curing the adhesive via application of heat. 
         [0013]    The method of the present invention may include applying an RFID tag over the auxiliary antenna. The RFID tag may include a tag antenna. The RFID tag preferably is applied over the auxiliary antenna such that it is electromagnetically coupled with the tag antenna. The method may include punching the cardboard surface into carton blanks such that the auxiliary antenna is positioned on a side panel of the carton. The method may include embossing each carton blank with fold lines, folding the blank along the fold lines and assembling the blank into a carton. 
         [0014]    According to a further aspect of the present invention there is provided an apparatus for forming on a moving surface an auxiliary antenna for an RFID tag, said apparatus including: 
         [0015]    means for providing a webstock of polymeric material including a conductive film; 
         [0016]    means for conveying said webstock with said moving surface; and 
         [0017]    means for applying said conductive film to said moving surface in a shape corresponding to said antenna. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Preferred embodiments of the present invention will now be described with reference to the accompanying detailed description which refers to the drawings wherein: 
           [0019]      FIG. 1   a  is a top, perspective, schematic view of a cold stamping process for manufacturing an auxiliary antenna for an RFID tag in accordance with the present invention; 
           [0020]      FIG. 1   b  is a top, perspective, schematic view of a subsequent step in the cold stamping process shown in  FIG. 1   a;    
           [0021]      FIG. 1   c  is a top, perspective, schematic view of a subsequent step in the cold stamping process shown in  FIG. 1   a;    
           [0022]      FIG. 1   d  is a top, perspective, schematic view of a subsequent step in the cold stamping process shown in  FIG. 1   a;    
           [0023]      FIG. 2  is a side, perspective, cross-sectional view of webstock including conductive film suitable for use with cold stamping in accordance with the present invention; 
           [0024]      FIG. 3  is a side, perspective, cross-sectional view of further webstock including conductive film suitable for use with the cold stamping process of the present invention; 
           [0025]      FIG. 4  is a top, perspective, schematic view of a hot stamping process for manufacturing an auxiliary antenna for an RFID tag in accordance with the present invention; 
           [0026]      FIG. 5  is a side, perspective, cross-sectional view of webstock including conductive film suitable for use with hot stamping in accordance with the present invention; 
           [0027]      FIG. 6  is a side, perspective, cross-sectional view of further webstock including conductive film suitable for use with hot stamping in accordance with the present invention; 
           [0028]      FIG. 7   a  is a side, perspective view of an auxiliary antenna and RFID tag applied to a cardboard object in accordance with the present invention; 
           [0029]      FIG. 7   b  is a front view of the auxiliary antenna shown in  FIG. 7   a;  and 
           [0030]      FIG. 7   c  is a side, perspective, enlarged view of the RFID tag module shown in  FIG. 7   a.    
       
    
    
     DETAILED DESCRIPTION 
       [0031]      FIG. 1   a  shows a cardboard roll manufacturing process including a cold stamping apparatus  10  for manufacturing an auxiliary antenna  20  for an RFID tag  21 . The cold stamping apparatus  10  shown in  FIG. 1   a  is adapted to apply a relatively thin antenna (approximately not more than about 5 μm) to a cardboard surface  11  in the cardboard roll manufacturing process. The cold stamping apparatus  10  includes an offset printing roll  12  for applying to the surface  11  of the cardboard roll a suitable adhesive  13  in a shape corresponding to the auxiliary antenna. The apparatus  10  includes a roller  14  for supplying continuous webstock  15  including a conductive film  16 . The conductive film  16  is applied to the surface  11  of the cardboard roll by means of a pressing roller  17  and a source  18  of ultra violet (UV) light for irradiating the film prior to being taken up by a roller  19 . 
         [0032]    Pressure applied by roller  17  causes the conductive film  16  to adhere to the adhesive  13  in the shape corresponding to the auxiliary antenna  20 . The adhesive is cured via the UV source  18 . As webstock  15  is pulled away from surface  11  the conductive film peels away from webstock  15  and the webstock excluding portions corresponding to the peeled antennas is taken up by roller  19 . 
         [0033]    An RFID tag module  21  is then positioned and applied over the auxiliary antenna  20 . The carton blank is subsequently punched from the cardboard roll at punching station  22  prior to being embossed with fold lines  28  (refer  FIG. 1   b ), folded  29  along the fold lines (refer  FIG. 1   c ) and assembled into a carton  30  (refer  FIG. 1   d ). 
         [0034]      FIG. 2  shows one example of webstock  15  including conductive film suitable for use with the cold stamping process. The webstock  15  includes a substrate  23  comprising a flexible polymeric material such as polyester (PE), polyethylene terephthalate (PET) or polyethylene napthalate (PEN). A release layer  24  is applied over the substrate  23  to facilitate peeling of subsequent layers from substrate  23 . An insulating layer  25  such as a varnish is applied over the release layer  24 . The insulating layer  25  may be color coded for a purpose as described below. A layer of a first conductive material  26  such as aluminum is applied over the insulating layer  25 . A layer of a second conductive material  27  such as copper is applied over the first conductive material  26 . The conductive layers may be deposited over the insulating layer in any suitable manner and by any suitable means such as by metal evaporation. The relative thickness of the first and second layers of conductive material may vary in the range of 25% to 75%. The relative thickness may be varied to adjust resistivity of the conductive film and for a purpose as described below. The resistivity of the conductive film is preferably in the range of 0.05-0.1 ohms/cm or less. 
         [0035]      FIG. 3  shows another example of webstock  15  including conductive film suitable for use with the cold stamping process. The webstock  15  includes a substrate  33  comprising a flexible polymeric material (PE, PET or PEN), a combined insulating/release layer  34  is applied over the substrate  33  to facilitate peeling thereof from substrate  33 . A layer of a first conductive material  36  (e.g. aluminum) is applied over the insulating/release layer  34 . A layer of a second conductive material  37  (e.g. copper) is applied over the first conductive material  36 . 
         [0036]    The color of the varnish may be defined in accordance with a specific use. The defined color may provide an anti-counterfeiting measure and/or a means for coding products, e.g. the varnish may be colored red for dangerous goods, blue for safe goods, green for perishable goods, etc. Colored varnish may also be used for aesthetic purposes. 
         [0037]    An additional or alternative anti-counterfeiting/coding measure may include adjusting relative thickness of the first and second conductive materials  26 / 36 ,  27 / 37 . In one form the relative thickness of the conductive materials may be 75% aluminum and 25% copper. The relative thicknesses of the first and second conductive materials may be detected and/or measured by means of x-ray fluorescence spectroscopy. If a detected and/or measured thickness of the first and second conductive materials does not substantially agree with an expected relative thickness of the conductive materials, the product may be treated as being counterfeit or non-genuine. 
         [0038]      FIG. 4  shows a cardboard roll manufacturing process including a hot stamping apparatus  40  for manufacturing an auxiliary antenna  48  for an RFID tag  49 . The hot stamping apparatus  40  is adapted to apply a relatively thick antenna (approximately at least about 5 μm) to a cardboard surface  41  in the cardboard roll manufacturing process. The hot stamping apparatus  40  includes a roller  42  for supplying continuous webstock  43  including a conductive film  44  overlaid with a heat curing adhesive. The conductive film  44  and adhesive is applied to the surface  41  of the cardboard roll by means of a pressing roller  45  and a source of heat (not shown) prior to being taken up by a roller  46 . 
         [0039]    Pressing roller  45  includes a relief portion  47  in a shape corresponding to the auxiliary antenna  48 . Pressure applied by the relief portion  47  of roller  45  causes conductive film  44  to adhere to the surface  41  in the shape corresponding to the antenna  48 . Adhesive provided on the conductive film  44  is cured by the heat source. As webstock  43  is pulled away from surface  41 , the conductive film peels away from webstock  43  and the webstock excluding portions corresponding to the peeled antennas is taken up by roller  46 . 
         [0040]    An RFID tag module  49  is then positioned and applied over the conductive antenna  48 . The carton blank is subsequently punched from the cardboard roll at punching station  50  prior to being embossed with fold lines, folded and assembled into a carton as described with reference to  FIGS. 1   b  to  1   d.    
         [0041]      FIG. 5  shows one example of webstock  43  including conductive film suitable for use with the hot stamping process. The webstock  43  includes a substrate  53  comprising a flexible polymeric material such as polyester (PE), polyethylene terephthalate (PET) or polyethylene napthalate (PEN). A release layer  54  is applied over the substrate  53  to facilitate peeling of subsequent layers from substrate  53 . An insulating layer  55  such as a colored varnish is applied over the release layer  54 . The insulating layer  55  may be color coded for a purpose as described above. A layer of a first conductive material  56  such as aluminum is applied over the insulating layer  55 . A layer of a second conductive material  57  such as copper is applied over the first conductive material  56 . The conductive layers may be deposited over the insulating layer in any suitable manner and by any suitable means such as by means of metal evaporation. The relative thickness of the first and second layers of conductive layers may vary in the range of 25% to 75%. The relative thickness may be varied for a purpose as described above. The resistivity of the first and second conductive layers preferably is in the range of 0.05-0.1 ohms/cm or less. A final layer of a heat curing adhesive  58  is applied over the second layer of conductive material  57 . 
         [0042]      FIG. 6  shows another example of webstock  43  including conductive film. The webstock  43  includes a substrate  63  comprising a flexible polymeric material (PE, PET or PEN). A combined insulating/release layer  64  is applied over the substrate  63  to facilitate peeling thereof from substrate  63 . A layer of a first conductive material  66  (e.g. aluminum) is applied over the insulating/release layer  64 . A layer of a second conductive material  67  (e.g. copper) is applied over the first conductive material  66 . A final layer of a heat curing adhesive  68  is applied over the second layer of conductive material  67 . 
         [0043]      FIGS. 7   a  to  7   c  show RFID tag module  21 ,  49  positioned relative to an auxiliary antenna  20 ,  48  applied to a side panel  70  of a cardboard box or carton  30 . The RFID tag module  21 ,  49  is preferably applied such that it overlaps a portion of a conductive track of the auxiliary antenna  20 ,  48 . An enlarged view of the RFID tag module  21 ,  49  and auxiliary antenna  20 ,  48  is shown in  FIG. 7   c . The RFID tag module  21 ,  49  includes a U-shaped tag antenna  71  formed over a PET substrate  72 , and an IC chip (not shown) connected to antenna  71 . A layer of adhesive  73  is applied to the underside of substrate  72 . The RFID tag module  21 ,  49  is affixed over the insulating layer  34 ,  64  (colored varnish) associated with auxiliary antenna  20 ,  48 . 
         [0044]    Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention. 
         [0045]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.