Tamper evident packaging

Abstract

A tamper evident packaging system including a tag ( 10 ) attachable to a package comprising a substantially oxygen impermeable upper barrier layer ( 12 a ), a reactive intermediate layer ( 14 ) including a reactive material changeable between an un-reacted condition in the absence of oxygen and a reacted condition in the presence of oxygen to produce a visible colour change, and a lower layer ( 12 b ) which can be a substantially oxygen impermeable lower barrier layer or an integral part of the package.

1 . A tag attachable to a package so as to produce a tamper evident packaging system, characterised in that said tag includes a substantially oxygen impermeable upper barrier layer, a reactive intermediate layer, wherein the reactive intermediate layer includes a reactive material being a Matrix of a un oxidised vat dye in base material, said base material being selected from a protein matrix an agar-agar matrix, a polyvinylacetate/polyvieyl alcohol matrix or a cellulose matrix or mixtures thereof, said reactive material being changeable between an un-reacted condition in the absence of oxygen and a reacted condition in the presence of oxygen wherein said change takes the form of a colour change.  
     
     
         2 . A tag according to  claim 1 , characterised in that said substantially oxygen impermeable upper barrier layer is formed of colourless transparent material.  
     
     
         3 . A tag according to  claim 1 , characterised in that said tag additionally includes a substantially oxygen impermeable lower barrier layer.  
     
     
         4 . A tag according to  claim 3 , characterised in that, the lower barrier layer may be an integral part of a product package or container.  
     
     
         5 . A tag according to  claim 3 , characterised in that said lower barrier layer is of a colour selected to enhance the visibility of the colour change that occurs on exposure of the reactive layer to oxygen.  
     
     
         6 . A tag according to  claim 3 , characterised in that said lower barrier layer and tag dimensions are selected such that a colour change reaction exposes or obscures a logo or other indicia present on the packaged product or on a surface of the tag.  
     
     
         7 . A tag according to  claim 3 , characterised in that said lower barrier layer is formed of colourless, transparent or white material.  
     
     
         8 . A tag according to  claim 3 , characterised in that said upper and lower barrier layers are formed of adhesive coated transparent material with the addition of cellulose material said cellulose material serving to promote adhesion of the reactive material to the upper and lower barrier layers.  
     
     
         9 . A tag according to  claim 3 , characterised in that said upper and lower barrier layers are made of a thin film product.  
     
     
         10 . A tag according to  claim 9 , characterised in that said thin film product is a copolymer of ethylene and polyvinyl alcohol and adducts thereof having a maximum rate of oxygen and carbon dioxide diffusion therethrough of the order of 0.5 cm 3 /m 2 /24 hr for a 20 micron film thickness at 0% relative humidity and atmospheric pressure.  
     
     
         11 . A tag according to  claim 9 , characterised in that said thin film product is selected from a, biaxially oriented ethyl vinyl alcohol, polyvinyl alcohol, polypropylene and adducts thereof.  
     
     
         12 . A tag according to  claim 9 , characterised in that said thin film product is a polyvinyl alcohol film or a film of adducts thereof having a maximum oxygen permeability of 0.25 cm 3 /m 2 /24 hr for a 14 nanometre film thickness at a relative humidity of 35% and atmospheric pressure.  
     
     
         13 . A tag according to  claim 9 , characterised in that said thin film product is a copolymer of ethylene and vinyl alcohol and adducts thereof having a maximum gas permeability of: 
 O 2  0.2 cm 3 /m 2 /24 hr for a 20 micron film thickness at 0% relative humidity and atmospheric pressure; and    CO 2  0.8 cm 3 /m 2 /24 hr for a 20 micron film thickness at 0% relative humidity and atmospheric pressure.    
     
     
         14 . A tag according to  claim 3 , characterised in that said upper and lower barrier layers are constituted as laminate films, at least one layer of said laminate film being a substantially gas impermeable barrier film formed as mono or coextruded film.  
     
     
         15 . A tag according to  claim 3 , characterised in that said upper and lower barrier layers additionally include oxygen scavenging materials, or ultra violet resistant materials or wherein the upper and lower barrier layers incorporate ultra violet stabilized plastics materials such as polycarbonate, treated polycarbonate and adducts thereof with anti-oxidant materials such as butylated hydroxy-toluene.  
     
     
         16 . A tag according to  claim 1 , characterised in that said reactive material includes an un-oxidised vat dye composition in the proportion 0.001%-50% wt/wt the base material forming the balance.  
     
     
         17 . A tag according to  claim 1 , characterised in that said un-oxidised vat dye composition contains indigo 3.8 mM, sodium hydroxide 0.3M, sodium dithionite 0.24M and has a pH within the range 4-12.  
     
     
         18 . A tag according to  claim 1 , characterised in that said base material is a casein hydrochloride adhesive material which acts as a matrix material containing the un-oxidised vat dye.  
     
     
         19 . A tag according to  claim 1 , characterised in that said base material is constituted by a polyvinyl acetate material hydrolysed and converted in situ to a polyvinyl alcohol vat dye adduct.  
     
     
         20 . A tag according to  claim 1 , characterised in that the oxygen reactive layer is secured between two substantially oxygen impermeable layers such that oxygen penetrates the tag through lateral diffusion into exposed edges of the tag, whereby, the reactive intermediate layer undergoes a colour change that commences at the periphery of the tag and that gradually moves towards a centre of the tag.  
     
     
         21 . A method of manufacturing a tag according to any one of the preceding claims, characterised in that the tag is affixed to a product package in an oxygen-depleted atmosphere such that the tag will undergo the colour change reaction on opening of the package in an oxygen containing atmosphere.  
     
     
         22 . A method according to  claim 21 , characterised in that the tag is placed on the package and subsequently covered in an air excluding covering such as a shrink wrap covering.  
     
     
         23 . A method according to  claim 22 , characterised in that a shrink-wrap package is placed around the tag in an oxygen free atmosphere.  
     
     
         24 . A method according to  claim 23 , characterised in that the tag is located on a product packaging in a non oxidising atmosphere, such as a carbon dioxide environment, a nitrogen environment or a vacuum or combinations thereof and subsequently wrapped in a gas impermeable covering.  
     
     
         25 . A method according to  claim 23 , characterised in that the tag is placed in a package having a positive pressure and a non-oxidising gas within the package.