Abstract:
A method of making an electronic label, such as an RFID label, includes attaching a circuit, such as an antenna, to a substrate material, applying an adhesive layer to the substrate material over the circuit, adding a release layer over the adhesive layer, forming at least one opening in the release layer to expose at least one portion of the circuit, and connecting a microchip to the at least one portion of the circuit through the at least one opening. The circuit can be an RFID inlay, including an antenna and a microchip, and can be formed of a conductive ink. A portion of the release layer at the at least one microchip has an opening to expose the at least one microchip so that the at least one microchip is free from coverage by the release layer.

Description:
[0001]     This application is a continuation of U.S. application Ser. No. 11/276,713, filed Mar. 10, 2006, which claims the benefit under 35 USC 119 of U.S. Provisional Application No. 60/596,742, filed Oct. 18, 2005. Both of the above applications are hereby incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates generally to a label incorporating an electronic component. In one of its aspects, the invention relates to a label incorporating an electronic component. In another of its aspects, the invention relates to a method of making a label with electronic components. In yet another of its aspects, the invention relates to a label that incorporates an RFID circuit. In another of its aspects, the invention relates to a method of making a label having an RFID circuit.  
         [0004]     2. Description of the Related Art  
         [0005]     The use of a radio frequency identification (RFID) to identify one of a plurality of items is well known. Typical radio frequency identification (RFID) tags or integrated circuits comprise a microprocessor, also known as a microchip, electrically connected to an antenna. Alternatively, the microchip is first attached to a pad having electrical leads that provide a larger attachment or “landing” area. This is typically referred to as a “strap” or “interposer.” The strap is then attached to the antenna.  
         [0006]     The microprocessor stores data, which can include identifying data unique to a specific item, which is transmitted to an external receiver for reading by an operator and processing of the item. RFID tags can be attached to items for inventory control, shipment control, and the like. RFID tags are particularly useful in identifying, tracking, and controlling items such as packages, pallets, and other product containers. The location of each item can be tracked, and information identifying the owner of the item or specific handling requirements, can be encoded into the RFID and later read by a scanning device capable of decoding and displaying the information.  
         [0007]     RFID tags have been incorporated into a pressure sensitive adhesive-backed label for items contained in temporary packaging, such as cardboard cartons, or containers which are to undergo a number of reuses, such as pallets, waste containers, shipment containers, and the like. These labels are conventionally fabricated by attaching an antenna made of metal foil, conductive ink, or other suitable material, to a substrate material such as paper, film, and the like, also referred to as an “inlay substrate.” A microprocessor or strap is attached to the substrate in cooperative disposition with the antenna to form what is typically referred to as an “inlay.” An adhesive is then applied to the surface of the inlay substrate over the antenna and microprocessor, and the inlay substrate is attached to a label substrate, on which text and graphics can be imprinted, so that the adhesive, antenna, and microprocessor are sandwiched between the inlay substrate and the label substrate. A layer of adhesive is then applied to the surface of the label substrate over the inlay, followed by the addition of a release layer over the adhesive. The laminate can then be die cut to the finished label size. Printing of a bar code or other information, text, and graphics onto the finished label, and coding of the microprocessor, can take place before or after the die cutting step. The labels are then wound tightly onto a spool, or processed into a fan-fold configuration, for shipment to a customer or return to the electronic manufacturer or marketer. The application of the inlay to the paper is usually carried out by an electronic manufacturer and the remaining steps are typically carried out by a label manufacturer.  
         [0008]     The handling of the inlay during this label-making process imposes stresses on the inlay which can result in damage to the microprocessor. In addition, the inlay can be subject to electrical fields or discharges during the manufacturing process that damage the microchip. Thus, a fairly high level of scrap has been generated by the current label-making process. Since the microprocessor is typically the most costly component, minimizing the incidence of damaged microprocessors is highly desirable to reducing the scrap rate.  
       SUMMARY OF THE INVENTION  
       [0009]     According to the invention, a method of making an electronic label comprises the steps of attaching a circuit to a substrate, applying an adhesive layer to the substrate over at least a portion of the circuit, applying a release layer over the adhesive layer and forming at least one opening in the release layer to expose at least one portion of the circuit.  
         [0010]     In one embodiment, the invention further comprises the steps of depositing at least one microchip in the at least one opening, and attaching the at least one microchip to the at least one circuit portion.  
         [0011]     In one embodiment, the step of forming at least one opening in the release layer comprises forming multiple openings in the release layer and the step of a depositing at least one microchip comprises depositing a microchip in each of the multiple openings.  
         [0012]     In one embodiment, the circuit includes an antenna and the microchip is an RFID chip.  
         [0013]     In one embodiment, the invention further comprises the step of removing a portion of the adhesive layer in registry with the at least one exposed portion of the circuit.  
         [0014]     Further according to the invention the substrate is of indefinite length and a plurality of circuits is arranged on the substrate. Preferably, the circuit-bearing substrate is wound into a roll. The completed labels with the microchips can also be positioned on an indefinite length release layer which is then wound into a roll. Preferably, the release layer with the completed circuits is wound loosely at a relatively low tension to minimize damage to the microchips.  
         [0015]     In a preferred embodiment, the substrate is separated into individual labels such as through a die cutting process.  
         [0016]     Further according to the invention, a label comprises a substrate having on one surface a circuit, a layer of adhesive covering the circuit and the one surface of the substrate, a release layer covering the adhesive layer, and a portion of the release layer has an opening to expose at least a portion of the circuit.  
         [0017]     In another preferred embodiment of the invention, the circuit includes at least one microchip and the opening is positioned at the at least one microchip.  
         [0018]     In one embodiment of the invention, the circuit is an RFID inlay, including an antenna and a microchip. The antenna can be conductive ink or other conductive material.  
         [0019]     In yet another embodiment of the invention, there are multiple microchips in the circuit and multiple openings in the release layer in registry with each of the multiple microchips.  
         [0020]     The substrate can be made of any conventional label equipment, including paper, plastic film, or other electrically insulated film.  
         [0021]     Further according to the invention, the release layer is of indefinite length and includes a plurality of the labels described above. Preferably, the label-bearing release layer of indefinite length is wound into a roll.  
         [0022]     In one embodiment of the invention, the label is imprinted with visible information on one surface of the substrate. The one surface is typically an exposed side of the label so that the printed information is visible when the labels are stripped from the release layer and applied to a final destination surface. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     In the drawings:  
         [0024]      FIG. 1  is a perspective view of an RFID label according to the invention;  
         [0025]      FIG. 2  is an exploded view of the RFID label illustrated in  FIG. 1 ;  
         [0026]      FIG. 3  is an exploded view of the RFID label illustrated in  FIG. 1  showing an intermediate step in the fabrication of the label; and  
         [0027]      FIG. 4  is a flow chart showing various steps in the fabrication of the RFID label illustrated in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0028]     The invention will be described herein and illustrated by the Figures with respect to an RFID label comprising a microchip and antenna, and a method of making the same, which minimizes the potential for damage to the microchip comprising a component of the label. As will be apparent from the forgoing disclosure and the following description of the invention, the invention in its broadest aspects includes other types of electronic labels, and encompasses a method of manufacture of electronic labels having other types of electronic components.  
         [0029]     Referring specifically to  FIGS. 1 and 2 , an RFID label  10  according to the invention comprises a thin, flexible label substrate  12  which can be a coated paper, film, or similar material suitable for use in a label. Alternatively, the substrate can comprise a more rigid material, such as a circuit board material. An electrical circuit, illustrated as an antenna  14 , comprises a thin layer of conductive material, such as a conductive ink, metal foil, sputter-deposited conductive material, and the like, disposed in a preselected configuration suitable for receiving and transmitting radio frequency signals of a preselected frequency over a preselected distance. In a preferred embodiment, the antenna  14  is applied to the substrate  12  through a lithographic process using a commercially-available conductive ink. The antenna  14  is configured with a pair of spaced-apart antenna contacts  30 ,  32 . The Figures illustrate an antenna  14  having a preselected configuration for illustrative purposes only. Antennas of differing configurations can be utilized depending on the requirements of a particular application. Additionally, circuits having functionality other than the receipt and transmission of radio frequency signals, can be utilized with the invention described herein.  
         [0030]     The RFID label  10  also comprises a thin adhesive layer  18  suitable for adhering to the substrate  12 , antenna  14 , and container, and a release layer  20  for protecting the adhesive layer  18  until the label  10  is to be applied. Suitable adhesives can include well-known transfer adhesives, spray adhesives, or UV adhesives. The substrate  12 , antenna  14 , adhesive layer  18 , and release layer  20  are disposed in a layered configuration. The substrate  12  can be imprinted with visual information, such as text, graphics, bar coding, other optically-readable information, and the like. Typically, the visual information is imprinted on the substrate  12  subsequent to the application of the antenna  14 , adhesive layer  18 , and release layer  20  to the substrate  12 .  
         [0031]     A microchip  16  having data storage, processing, transmitting, and receiving specifications suitable for the purposes described herein is cooperatively disposed with the antenna  14  through the antenna contacts  30 ,  32 . It is anticipated that the microchip  16  will have passive UHF specifications. However, microchips having active UHF specifications, and other devices subject to a risk of damage during a label fabrication process such as a solar chip, a battery, a temperature sensor, and the like, can be incorporated into a label according to this invention. The microchip  16  can be prepared for a “direct die attach,” or a “strap attach,” as are well-known in the art. As used hereinafter, the term “microchip” will refer to a microchip, a microprocessor, a strap, an interposer, or a similar device adapted for attachment to an antenna.  
         [0032]     Referring now to  FIGS. 3 and 4 , the RFID label fabrication process  40  will be described.  FIG. 4  illustrates a series of steps in one embodiment of the label fabrication process. However, certain steps can be modified or eliminated based upon a particular label configuration, adhesive pattern, layer configuration, and the like, as described hereinafter. It is anticipated that the substrate material  12  will be provided as a web of material, and that the following described process will be automated and conducted in a rapid sequence or concurrently on a plurality of labels. However, the process will be described with respect to a single label having a single microchip.  
         [0033]     The process  40  is initiated by the selection  42  of a substrate material  12  having suitable properties for the intended label, such as size, durability, color, and the like. The antenna  14  is then applied  44  to the substrate  12  in a preselected configuration. The label adhesive layer  18  is applied  46  over the substrate  12 , followed by the addition of a release layer  20 . This can be followed by the printing of information or graphics on the substrate material  12 .  
         [0034]     The substrate material  12  is then separated into individual labels such as through a die cutting process. The die cutting step  50  can form perforations along a separation border for readily separating the labels along the perforations, or can completely separate the labels from each other, or can further cut selvage from the substrate to separate the labels into spaced-apart relationship and the selvage thus cut from the release layer can be subsequently removed from the release layer. Typically, the die cutting step  50  and any selvage removal step are carried out prior to the winding step. The chip windows  22 ,  24  are cut in the release layer  20  and label adhesive layer  18  through a well known die cutting process. Alternatively, the chip window  22  can be cut in the release layer  20  alone, leaving the adhesive layer  18  intact. The die cutting operation is controlled utilizing any well-known registration method so that the cut does not extend into the antenna  14 . The chip window release layer portion  26  is then removed  54 . The adhesive portion  28  can also be removed  56  if it is not removed during the removal of the chip window release layer portion  26 . Alternatively, if a transfer adhesive is utilized for the adhesive layer  18 , the transfer adhesive can be pre-cut with the chip window  24 , thereby eliminating step  56 , i.e. the separate removal of the adhesive portion  28 . Additionally, the chip window die cutting operation can either occur before or after the label cutting operation, or be conducted concurrently with it.  
         [0035]     In a “direct die attach” process, a chip adhesive is applied  58  through the chip windows  22 ,  24  to the substrate  12  intermediate the antenna contacts  30 ,  32 . The microchip  16  is then attached  60  to the antenna contacts  30 ,  32  by embedding the microchip  16  in the chip adhesive through the chip windows  22 ,  24 . Alternatively, the microchip  16  can be supplied with an adhesive already applied, thus obviating the separate chip adhesive application step  58 . The label  10  is then positioned intermediate a pair of machine-controlled thermodes which are heated and brought together under carefully controlled conditions of temperature and pressure  62  to cure the adhesive and fix the microchip  16  in the adhesive. Alternatively, the adhesive can be cured by other suitable methods, such as UV curing, and the like.  
         [0036]     Alternatively, in order to facilitate the connection of the microchip to the antenna, the microchip (conventionally referred to as a “strap” or “interposer”) can be provided with extension leads for connection to the antenna contacts  30 ,  32 . The leads can be configured to enable the microchip to be connected to the antenna  14  without having to precisely position the microchip relative to the antenna contacts  30 ,  32 .  
         [0037]     This is followed by loosely accumulating  64  the labels  10  onto a roller with the chip windows  22 ,  24  facing inwardly, or in a fan-fold configuration. The finished labels  10  can then be removed from the release layer  20  and applied to a carton, pallet, shipping container, and the like.  
         [0038]     Alternatively, the adhesive layer  18  can be applied to the substrate  12  under controlled conditions to eliminate adhesive in the area corresponding to the chip windows  22 ,  24 , thus eliminating the need for separate removal of the adhesive portion  28  from the substrate  12 . Similarly, the adhesive layer  18  can be applied to the substrate  12  in two strips on either side of the chip window area to eliminate the adhesive in the chip window area. The two adhesive strips can be aligned on the substrate  12  longitudinally or laterally, or can cover predefined areas of the substrate  12 , e.g. the corners.  
         [0039]     In another embodiment, the adhesive layer  18  and the release layer  20  can be applied over the entire substrate  12 , and then a strip of the release layer  20 , with or without a strip of the adhesive layer, can be removed to expose the microchip attachment area. The strip can be retained, such as on a roller, while the microchip  16  is attached to the antenna  14  as previously described. The strip can be reapplied to the substrate  12  over the microchip  16  after the attachment and curing processes, followed by accumulating the finished labels  10  onto a roller, or in a fan-fold configuration.  
         [0040]     In yet another embodiment, the adhesive layer  18  and the release layer  20  can be applied over the entire substrate  12  on the surface opposite the antenna  14  and the microchip  16 . The label  10  as applied will be attached to an item with the antenna  14  and the microchip  16  facing away from the item surface. The microchip  16  will be attached to the antenna  14  in the final step of the label fabrication and printing processes in order to minimize damage to the microchip  16 .  
         [0041]     The microchip  16  is illustrated in the Figures as located in a central portion of the antenna  14 . However, the invention can also be employed with a microchip  16  in any location within the label, or with a plurality of microchips.  
         [0042]     The process according to the invention can be carried out in a single or in multiple facilities. For example, the steps of printing and applying the circuits to the substrate, applying adhesive to the substrate, and applying a release layer to the adhesive layer can be carried out at a label conversion facility, and the steps of applying the microchip to the circuit and connecting the microchip to the circuit can be carried out at an electronic manufacturing plant. Typically, the steps of removing a portion of the release layer and the adhesive layer can be carried out at the label converter.  
         [0043]     The method of fabricating an RFID label described herein differs from prior art RFID label fabrication methods in that the microchip or strap is incorporated into the label as essentially a last step in the fabrication process. This occurs after the rest of the label has been fabricated, and after printing of the label, thereby minimizing the potential for damage to the microchip caused by the label fabrication and printing processes.  
         [0044]     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the forgoing disclosure and drawings without departing from the spirit of the invention which is defined in the appended claims.