CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 11/413,499, entitled “Antimicrobial Coating For Identification Devices,” filed Apr. 28, 2006, which claims priority to U.S. Provisional Application No. 60/676,077, entitled “Antimicrobial Coating For Identification Devices,” filed Apr. 28, 2005, both of which are hereby incorporated by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is related to the field of antimicrobial materials, and in particular to medical devices with antimicrobial coatings capable of reducing the spread of bacteria. 
       DESCRIPTION OF RELATED ART 
       [0003]    The use of antimicrobial compounds, or other therapeutically active compounds to prevent the spread of microbes such as bacteria, algae, and fungi are well known in the prior art. In particular, antimicrobial compounds are commonly used in the medical field to protect patients from the growth or proliferation of bacteria. For example, antimicrobial compounds have been added to material of hospital bed sheets, surgical drapes, hospital gowns, medical mask, bandages, gauze, or any place a textile or textile fiber could be used to control the growth of microbes. 
         [0004]    One example of incorporating antimicrobial compounds within medical equipment is disclosed in U.S. Pat. No. 6,700,032 which describes a bandage or wound dressing incorporating the use of an antimicrobial compound to promote better wound management and wound healing. 
         [0005]    Additionally, U.S. Patent Application No. 2004/0092896 describes an antimicrobial sheet for environmental and human protection. These sheets are formed into rings about thee inches in diameter, three quarter of an inch wide and one eight of an inch thick and are adapted to be worn on a person&#39;s wrist. 
         [0006]    Notwithstanding the common use of antimicrobial compounds in a multitude of medical devices, the antimicrobial compounds sometimes change desirable properties of the medical devices. Therefore, there is still a need for improvements in the use of antimicrobial components with medical devices. 
         [0007]    Therefore, it would be advantageous to have medical devices that retain their original function while simultaneously providing antimicrobial protection. It would also be advantageous if the components of the devices were economical to manufacture. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The present invention addresses the above needs, and achieves other advantages, by providing an identification device that combines an antimicrobial coating with a printable substrate. For example, the invention includes a wristband with a face stock supporting indicia which are applied on (such as through thermal transfer printing) or through (such as through direct thermal printing) an antimicrobial layer. The antimicrobial layer is preferably a coating or varnish that is applied as the outermost layer and can bind with thermal transfer printing ink or supports pass through of direct thermal printing onto a chemically receptive sublayer. The antimicrobial varnish includes varnish compounds and antimicrobial compounds such as a silver zeolite ion that is configured to react to moisture to produce a controlled release of microbial disinfectant. Preferably, the wristband is a hospital wristband bearing on-site printed identification indicia for a patient. 
         [0009]    In one embodiment, the present invention includes a medical device with an antimicrobial coating that bears printed indicia. The printed indicia is either printed directly onto a printable overvarnish that includes antimicrobial compounds, or is transferred through a UV curable overvarnish containing antimicrobial compounds and printed onto an imaging chemical layer. 
         [0010]    In one aspect, the medical device is a wristband and the indicia are identifying indicia for a patient. Included in the wristband is a face stock, a protective layer over the face stock, an antimicrobial coating over the protective layer, and identifying indicia supported or permitted thereby. 
         [0011]    In another aspect, the wristband is generally rectangular and includes a pair of opposing long edges and a pair of opposing short edges. The face stock includes two portions, a body portion that supports the antimicrobial coating and the indicia and a connector portion that is configured to be secured at its free end to the body portion when encircling a wrist or appendage. 
         [0012]    Connectors may be used to connect the connector portion to the body portion, such as a clasp or clip that uses an insert for passing through communicating holes in the body and connector portions. Alternatively, a crack and peel connector may be employed that includes an adhesive patch covered by a cover. Removal of the cover reveals the adhesive patch which is pressure sensitive and adheres the opposing ends of the face stock together when the ends are applied to form the loop of the wristband. 
         [0013]    The present invention has many advantages. For example, medical devices (such as the wristband) of the present invention with indicia and an antimicrobial coating can be used within potentially contaminated environments that require on-demand printing with variable information, such as identification information. For example, in a hospital environment, patients may be provided identification wristbands that include indicia information such as name, sex, and medical history. Thus, the patient is identified and at the same time protected by the antimicrobial coating from dangerous bacteria that could aggravate the patient&#39;s medical condition. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0014]    Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
           [0015]      FIG. 1  is a plain view of an antimicrobial identification wristband of one embodiment of the present invention including a crack and peel fastener; 
           [0016]      FIG. 2  is a plain view of an antimicrobial identification wristband according to another embodiment of the present invention including a crack and peel fastener; 
           [0017]      FIG. 3  is a plain view of an antimicrobial identification wristband according to yet another embodiment of the present invention including a clip fastener; 
           [0018]      FIG. 4  is a plain view of an antimicrobial identification wristband according to still another embodiment of the present invention including a clip fastener; 
           [0019]      FIG. 5  is a cross-sectional diagram of the antimicrobial identification wristband of  FIG. 1  showing an antimicrobial varnish layer and print indicia of the wristband; 
           [0020]      FIG. 6  is a flow diagram of a method of another embodiment of the present invention for applying identification information to an antimicrobial identification device using a thermal transfer printing process; 
           [0021]      FIG. 7  is a diagram of the thermal transfer printing process; 
           [0022]      FIG. 8  is a flow diagram of a method of another embodiment of the present invention for applying identification information to an antimicrobial identification device using a direct thermal printing process; 
           [0023]      FIG. 9  is a diagram of the direct thermal printing process of  FIG. 8 ; and 
           [0024]      FIG. 10  is a diagram of a zeolite ion exchange process. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. 
         [0026]    Generally described, the present invention is directed to identification devices with an antimicrobial coating  11  supporting printing of indicia  12  thereon or through, such as a wristband  10  of one embodiment of the present invention shown in  FIGS. 1 and 5 . The wristband  10  includes a face stock  13 , a protective top coating  14 , and a layer of antimicrobial coating  11 , or “overvarnish,” containing antimicrobial compounds, as shown in  FIG. 5 . As shown in greater detail below, different embodiments of the identification devices of the present invention are designed to be compatible with various printing procedures such as direct thermal printing and thermal transfer printing. 
         [0027]    As used herein, the term “identification device” may also apply to other devices benefiting from, or requiring, printing through or on antimicrobial layers or components. For example, within the purview of the present invention are plaques, plates and identification badges bearing the indicia  12  and the overvarnish  11 , or other antimicrobial layer of protectant that allows for printing. Notably, the identification device could be a component of an overall larger device, especially a device benefiting from antimicrobial properties, such as an implant or personalized article of clothing. 
         [0028]    The term “facestock” as used herein denotes generally the type of material used to form the supporting structure of the wristband or other identification device and is capable of retaining the print indicia  12  in combination with the protective coating  14 , without the antimicrobial overvarnish  11 . The term “antimicrobial” as used herein denotes a substance with the ability to control the breeding, growing and proliferation of microorganisms. 
         [0029]    Referring again to  FIGS. 1 and 5 , the face stock  13  of the wristband  10  includes a pair of long edges  16 , a pair of short edges  17 , a body portion  18  and a connector portion  19 . The body portion  18  is rectangular and is defined between about two-thirds of the two long edges  16  and one of the short edges  17 . The body portion  18  is relatively wider than the connector portion  19 . The connector portion  19  is similarly rectangular, but is narrow and shorter than the body portion  18 , being defined between the remaining one third of the two long edges  16  and the other one of the short edges  17 . 
         [0030]    The body portion  18  being relatively wide provides a good supporting surface for the indicia  12 , which in the illustrated embodiment of  FIG. 1  includes three panels of print indicia and a barcode symbol. The connector portion  19  is relatively slender, allowing it to be wrapped around a wrist or appendage of a wearer first and then covered over by the body portion  18  so that the indicia  12  remain visible. 
         [0031]    In the embodiment illustrated in  FIG. 1 , the wristband  10  is attached to the user through the use of an adhesive patch (not shown) supported on an underside of the body portion  18  near the short edge or on the topside of the connector portion  19  near the short edge (or both), as shown in  FIG. 1 . A cover (not shown) extends over the adhesive patch and can be removed using a “crack and peel” method. In this method, the user exposes the adhesive patch located on one end of the wristband and wraps the adhesive end onto the opposite end to secure the wristband in a closed loop. The cover, for example, may include a polyester release liner and the adhesive patch an acrylic adhesive that is pressure sensitive, allowing it to be compressed between the body and connector portions  18 ,  19  for sealing. 
         [0032]    The face stock  13  of the embodiment illustrated in  FIGS. 1 and 5  is preferably constructed from a tough synthetic material, such as from polypropylene, polyester, polyethylene or woven nylon. Alternatively, the face stock could be constructed from a natural material such as a paper material or cotton textile. Generally, it is desirable for the face stock to be relatively tough to resist breakage, flexible to allow bending into a loop and be able to withstand the heat of printing. In other embodiments, such as antimicrobial identification badges, these properties may vary, such as not requiring flexibility due to its use as a badge. 
         [0033]    The face stock  13  of the wristband  10  can have other shapes and lengths and still be within the purview of the present invention. For example, the body portion  18  may be three fourths of the length of the wrist band  10  and transition therefrom to the connector portion  19  by an inward slope along one of the long edges  16 , as shown in  FIG. 2 . This differs from the sudden notch that marks the transition between the body portion  18  and connector portion  19  on the embodiment shown in  FIG. 1 .  FIGS. 3 and 4  illustrate still other embodiments of the wristband  10  of the present invention with variations in the shape of the face stock  13 . In other embodiments, identification devices such as the wristbands shown in  FIGS. 1 and 2  can be further configured to include radio frequency identification (RFID) functionality. 
         [0034]    Other fasteners may be used to connect the wristband  10  of the present invention into a loop. For example, in the embodiments illustrated in  FIGS. 3 and 4 , the wristband  10  includes a plastic clip  39  which connects to the opposing end via one of a plurality of holes  22 . In particular, one of the holes  40  is positioned near the free end of the connector portion  19  and a line of the holes  22  are spaced along the body portion  18 . The plastic clip  39  includes a base which is a plastic rectangular sheet with rounded ends. Across a middle portion of the base is a thinned section  24 , at one end is supported an opening  25  and at the other end is supported an insert  26 . The thinned section  24  allows the base to be bent over on itself for insertion of the insert  26  through an overlapping pair of the holes  22 ,  40  (when the portions  19 ,  20  are overlapped to form the loop) and into the opening  25 , thereby locking the ends of the wrist band  10  together. Advantageously, the plurality of holes allows the user to adjust the diameter of the band to fit their wrist. 
         [0035]    Dimensionally, the wristband  10  of the present invention may vary in overall length, width and thicknesses, although they typically should be sized to fit most persons. For example, the wristband may be 1 inch wide, 11 inches long and about an eighth of an inch thick and fit most normal adult persons. Wristbands intended to be used by infants or small children may be shorter than those intended to be worn by adults. Of course the dimensions and shapes of the face stock  13  can be varied for attachment to animals or other objects and not people. 
         [0036]    The wrist band  10  illustrated in  FIGS. 1 and 5  further comprises the top coating  14  which is a protective layer that is applied to the face stock  13 . Preferably, the top coating  14  is evenly applied and is thermal transfer compatible, i.e., capable of receiving the thermal transfer ink to form the indicia  12 , as shown in  FIG. 5 . In addition, the top coating  14  preferably is water resistant or hydrophobic to protect the face stock  13  from weakening and contamination. For example, the top coating may comprise a resin or a polymer that effectively seals the face stock  13  from the environment. In one embodiment, the top coating  14  comprises resin and a plurality of fillers and binders. In addition, various pigments can be added for color. 
         [0037]    The layer of overvarnish  11  is the final outer layer that can be applied to one, or both sides, of the top coating  14  over the body portion  18  or connector portion  19  depending upon the expected exposure of the wristband  10  to microbes. Preferably, the overvarnish is a water-based varnish that is applicable in an even layer and includes some type of antimicrobial compound. In addition, the overvarnish  11  is receptive to thermal transfer ink printing as shown in  FIG. 5 . The smooth and uniform coating displayed by water based overvarnish makes it particularly receptive to thermal transfer ink printing. In addition, water based overvarnish holds antimicrobial particles in suspension, thereby allowing for an distribution of antimicrobial compounds within the printing area. In one embodiment, the water based overvarnish contains a combination of resins, water, and ammonia. 
         [0038]    In one embodiment, the antimicrobial compounds contained within the water based overvarnish  11  are silver zeolites. Generally defined, a zeolite is a mineral having a porous structure. There are approximately four dozen recognized naturally occurring zeolite minerals and many more synthetic varieties. Natural zeolites often form when volcanic rocks and ash layers react with alkaline groundwater. In addition, there are several types of synthetic zeolites that form by a process of slow crystallization of a silica-alumina gel in the presence of alkalis and organic templates. Some of the more common zeolites are analcime, chabazite, heulandite, natrolite, phillissite, and stillbite. An exemplary mineral formula for natrolite is Na 2 ,Al 2 Si 3 O 10 −2H 2 O. 
         [0039]    Antimicrobial powders may also be used that include a soluble glass and antimicrobial silver ions. Glass generally is known as a material with high chemical inertness. However, it is possible to lower the chemical inertness by altering its structure. Glass also retains metals as ions. The presence of water or moisture will release the metal (silver) ions, which function as antimicrobial materials, gradually. One commercial example of the glass based product is Ion Pure® from Ishizuka Glass. 
         [0040]    More specifically defined, zeolites are framework silicates consisting of interlocking tetrahedrons of SiO 4  and AlO 4 . In order to be a zeolite, the ratio (Si+Al)/O must equal 1/2. Zeolites have a negatively charged, hydrated alumino-silicate structure comprising large vacant spaces or cages that allow space for large cations such as sodium, potassium, barium, and calcium and even relatively large molecules and action groups such as water, ammonia, carbonate ions and nitrate ions. The negatively charged aluminum-silicate structure attracts and accommodates the positive cations listed above, i.e., NA, K, Ca, Mg, and others. The large vacant spaces of the zeolite structure allow for the easy movement of the resident ions and molecules into and out of the structure. 
         [0041]    In general, zeolites are characterized by their ability to lose and absorb water without damage to their crystal structures. This characteristic makes zeolites useful in a number of commercial applications. For example, zeolites are commonly used to perform ion exchange, filtering, odor removal, chemical sieve and gas absorption tasks. One of the most well-known uses of zeolites is in water softeners. Water having significant quantities of calcium is often referred to as being “hard.” Hard water is conducive to the growth of scum. The process of softening water involves passes the hard water through a plurality of zeolites charged with the much less damaging sodium ions. As the hard water passes through the zeolites, the calcium is exchanged for the sodium ions. In similar fashion, zeolites can absorb ions and molecules and this act as a filter for odor control, toxin removal, and as a chemical sieve. 
         [0042]    As mentioned above, in one embodiment of the present invention, silver zeolite represents the antimicrobial compound used in conjunction with water based overvarnish. As illustrated in  FIG. 10 , the zeolite structure contains a plurality of silver ions. When exposed to moisture, sodium ions (present in the moisture) are exchanged for the silver ions. 
         [0043]    Preferable, the overvarnish  11  includes AgION™ brand silver zeolite compounds for its antimicrobial properties. As with all silver zeolite compounds, AgION™ is a compound containing silver ions (the active ingredient) bonded to a ceramic material that is completely inert (a zeolite carrier). Ambient moisture in the air causes low-level release that effectively maintains the antimicrobial properties of the overvarnish  11 . As humidity increases, more silver is released. Ultimately, the powerful antimicrobial silver ions kill microbes such as bacteria, fungi, and algae. In particular, the silver ions interfere with the nutrients that sustain bacteria, thereby providing the antimicrobial effects. 
         [0044]    It should be understood that any number of antimicrobial compounds compatible with the varnish, or other binding or coating compound used in the overvarnish  11 , are within the scope of the present invention. In another example, a compound in the overvarnish  11  used to prevent the spread of bacteria may be “Inorganic Antibacterial XAW10D,” produced by SINANEN-ZEOMIC Corporation. As with AgION™ antibacterial Zeomic is a mineral zeolite composite containing silver ions. 
         [0045]    In addition, although the embodiments described above use silver zeolites as the antimicrobial compound, other embodiments use antimicrobial substances such as Triclosan. Triclosan exhibits similar properties as the silver zeolites described above, i.e., it is a highly effective antimicrobial agent that is mixable and compatible with the varnish. Triclosan is manufactured by Ciba Specialty Chemical Products under the trade names IRGASAN and IRGACARE and has a molecular formula of C 12 H 7 CL 3 O 2 . 
         [0046]    The overvarnish  11  is created by mixing the water-based varnish with the antimicrobial compound. In one embodiment, the anti-microbial compound such as AgION™ comes in a powder form and is mixed with a water based varnish prior to being applied to the wristband. As discussed in greater detail below, the mixed water based varnish and antimicrobial compound is applied to the wristband using a flexographic printing press. 
         [0047]      FIG. 6  illustrates the steps for construction of the wristband  10  using thermal transfer printing. In step  27 , the thermal transfer receptive coating  14  is applied to the surfaces of the face stock  13 , preferably on the body portion  18 . At step  28 , the coating of water based overvarnish  11  containing antimicrobial compounds (which were mixed as described above) is applied to the face stock  13 . Application of the overvarnish  11  is preferably by an even and thorough application process. For example, the water based overvarnish  11  may be applied over the entire face stock  13  using a flexographic printing press. Alternatively, the flexographic printing press can be configured to apply the overvarnish only to specific areas of the face stock  13  that are expected to experience exposure to microbes or contaminants. Preferably, however, the overvarnish  11  is uniformly applied across the entire surface area of one side of the face stock  13 . 
         [0048]    After the water based overvarnish is applied to the wristband, identification information is printed onto the wristband at step  29  using a thermal transfer printing process, as shown in  FIG. 7 . In the thermal transfer printing process, a thermal transfer ribbon  31  is passed between a thermal print head  30  and the wristband  10  so that the ink  50  of the thermal transfer ribbon  31  is imprinted by the heat of the print head  30  directly onto the overvarnish  11  to form the indicia  12 . 
         [0049]    A variety of ribbon types are available and can be used in conjunction with the thermal transfer printing process and the wristband  10  of the present invention. For example, the ribbons can be wax ribbons, wax/resin ribbons, or resin ribbons. In addition, thermal ribbons come in a variety of colors or print solely with black ink. 
         [0050]    In another embodiment of the present invention, the wristband  10  of the present invention is configured for printing on with a direct thermal printing process. As shown in  FIG. 9 , the wristband  10  in this embodiment includes an additional layer having thermal imaging chemicals  32 , such as one or more color formers  33  in a direct thermal paper. The thermal imaging chemical layer  32  is positioned underneath the protective top coating  14  and extends over the face stock  13  of the wristband  10 . The top coating  14  protects the thin layer of thermal imaging chemicals  32  from the environment, thereby limiting its exposure to water, blood, alcohol, alcohol from soaps, or soaps that could inadvertently alter the chemistry&#39;s appearance. The direct thermal imaging chemicals  32  are generally any form of heat sensitive material that will manifest portions of the indicia  12  with the application of heat. 
         [0051]    The wristband  10  also preferably includes a UV curable overvarnish mixed with an antimicrobial agent to form the overvarnish  11  layer. The UV curable nature of the overvarnish allows it to be used with the high heat of direct thermal printing and still preserves its antimicrobial properties. Much like the protective top coating  14 , the UV curable overvarnish protects the chemistry layer  32  from exposure to substances typically found in hospital, such as water, blood, and alcohol. Without protection from the UV curable overvarnish, the chemistry layer  32  can be activated, turning the chemistry layer  32  black or otherwise discolored. The result being the degradation of all or portions of the indicia  12  (e.g. bar codes and/or human readable information) which might lead to errors and reduce patient safety. 
         [0052]      FIG. 8  illustrates the steps for constructing the wristband  10  shown in  FIG. 9 . At step  34 , the thermal imaging chemical layer  32  or chemistry is applied in a layer to the face stock  13 . At step  35 , the protective top coating  14  is applied, as described in step  27  above. Then, in step  36 , a coating of UV curable overvarnish containing antimicrobial compounds is applied to the face stock  13 . For example, the UV curable overvarnish is applied using a process known as flexographic printing. 
         [0053]    The flexographic printing process may incorporate a form of rotary web letterpress that uses one or more relief plates comprised of flexible rubber or photopolymer plates. This allows the application of water-based or UV curable inks or varnishes to a material such as the protective coating  14  on the face stock  13  and chemical layer  32 . In this embodiment, the flexographic printing press applies the coating of UV curable overvarnish  11  containing antimicrobial sliver zeolite. 
         [0054]    In step  37 , the indicia  12  are printed onto the wristband  10  using a direct thermal printing method. Under the direct thermal printing method, a heated printhead  38  transfers an image directly onto the heat sensitive imaging chemical layer  32  located within the wristband  10 . In particular, the image is formed when the heat from the printhead causes the heat sensitive material to darken or burn and form the indicia  12 , as shown in  FIG. 9 . 
         [0055]    The present invention has many advantages. For example, medical devices (such as the wristband  10 ) of the present invention with indicia  12  and an antimicrobial coating  11  can be used within potentially contaminated environments that require on-demand printing with variable information, such as identification information. For example, in a hospital environment, patients may be provided identification wristbands  10  that include indicia  12  information such as name, sex, and medical history. Thus, the patient is identified and at the same time protected by the antimicrobial coating  11  from dangerous bacteria that could aggravate the patient&#39;s medical condition. 
         [0056]    Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
An identification device that combines an antimicrobial coating with a printable substrate. For example, the invention includes a wristband with a face stock supporting indicia which are applied on (such as through thermal transfer printing) or through (such as through direct thermal printing) an antimicrobial layer. The antimicrobial layer is preferably a coating or varnish that is applied as the outermost layer and can bind with thermal transfer printing ink or supports pass through of direct thermal printing on a chemically receptive sublayer. The antimicrobial varnish includes varnish compounds and antimicrobial compounds such as a silver zeolite ion that is configured to react to moisture with a controlled release of microbial disinfectant. Preferably, the wristband is a hospital wristband bearing on-site printed identification indicia for a patient.