Security labelling

Abstract

An optically detectable security marker for emitting light at a pre-selected wavelength. The marker comprises a rare earth dopant and a carrier incorporating the rare earth dopant. The interaction of the carrier and the dopant is such that the fluorescent fingerprint of the marker is different from that of the rare earth dopant. The marker may be incorporated into a plurality of items, such as fluids, for example paint, fuel or ink, and laminar products such as paper or banknotes or credit cards.

1 . A method of creating an optically detectable security feature, the method comprising: 
 providing network modifier oxides for use in creating a block of glass doped with a rare earth ion;    selecting weight percentages of the network modifier oxides to create desired energy levels in the block, where the desired energy levels are different to an intrinsic set of energy levels associated with the rare earth ion by itself or the undoped glass, and where altering the weight percentages alters the energy levels in the block;    creating the block; and    pulverizing the block to create individual optically detectable security features.    
   
   
       2 . The method of  claim 1 , wherein providing network modifier oxides for use in creating a block of glass doped with a rare earth ion includes providing at least two rare earth ions.  
   
   
       3 . The method of  claim 1 , further comprising varying the ratios, by mole percentage, of the at least two rare earth ions, thereby varying intensities of emissions at different pre-selected wavelengths.  
   
   
       4 . A method of creating an optically detectable security feature, the method comprising: 
 providing network modifier oxides for use in creating a block of glass doped with a rare earth ion;    selecting weight percentages of the network modifier oxides to create desired energy levels in the block, where the desired energy levels include a transition forbidden when the rare earth ion is in solution;    creating the block; and    pulverizing the block to create individual optically detectable security features.