Vacuum roll coated security thin film interference products with overt and/or covert patterned layers

Abstract

A security thread for embedding in or on a sheet such as a document, currency or packaging is disclosed, wherein the thread has a thin film interference structure deposited thereon. The structure may be a Fabry-Perot structure in the form of a single filter, or may be plural filters, spaced side-by-side. The thread appears to have separated interference filters deposited thereon. Preferably the thread is first roll coated with oil using an oil-ablation technique to remove deposited material in situ in the coating process. A magnetic layer may be deposited within, behind or in front of the thin film interference structure.

1 . A security thread for embedding within or upon a sheet or document, comprising: 
 an elongate substrate having a first side and a second side;    an optically variable structure deposited on one of the first and second sides of the elongate substrate, wherein the optically variable structure comprises a thin film interference structure, which appears as a plurality of separated interference filters arranged side-by-side and spaced from one another having visible color shifting properties in the form of a visible pattern of visually separated distinguishable indicia against one of a foreground and background of a different color.    
     
     
         2 . A security thread as defined in  claim 1 , wherein the visible pattern is made by the steps of: 
 a) coating the substrate with a first material in the form of the pattern or its inverse;    b) applying a layer of a second material over the first material and portions of the substrate absent said first material adjacent to where the first material is coated; c) removing the first material and the layer of the second material covering it, leaving the second material in regions where the substrate was not coated by the first material and,    d) coating a third and a fourth layer over the second material to form a plurality of Fabry-Perot filters in discrete regions.    
     
     
         3 . A security thread as defined in  claim 1 , wherein the first side of the elongate substrate has deposited thereon a first layer of reflective material comprising a plurality of side-by-side, spaced apart reflective regions, at least some of the spaced-apart reflective regions forming a first layer of the interference structure comprising a plurality of n-layered Fabry-Perot cavities.  
     
     
         4 . A security thread as defined in  claim 1  wherein a second optical structure is deposited on the second side of the elongate substrate and wherein a pattern comprising at least a patterned layer is present on the first side of the elongate substrate.  
     
     
         5 . A security thread as defined in  claim 4  wherein the second optical structure comprises an organic layer containing an anti-Stokes pigment.  
     
     
         6 . A security thread as defined in  claim 1 , further comprising a magnetic layer within or behind the interference filters.  
     
     
         7 . A security thread as defined in  claim 1 , further comprising a Fabry-Perot structure deposited on an opposite side of the elongate substrate to the separated interference filters and wherein one of the Fabry-Perot structure and the interference filters have windows that allow the other to be seen therethrough.  
     
     
         8 . A security thread as defined in  claim 4  wherein the second optical structure comprises a color shifting ink.  
     
     
         9 . A security thread as defined in  claim 1  further comprising a magnetic layer deposited between at least some of the side-by-side spaced apart interference filters.  
     
     
         10 . A security thread as defined in  claim 1 , further comprising a magnetic layer disposed upon a reflective layer or covered on at least one side by a reflective layer common to the plurality of separated interference filters.  
     
     
         11 . A security thread as defined in  claim 1  further comprising a magnetic layer disposed within and or between or behind the interference filters, wherein the magnetic layer contains machine readable information for verifying the authenticity of the thread or sheet.  
     
     
         12 . A security thread as defined in  claim 1 , wherein the security thread is disposed within or upon the sheet, and wherein the sheet forms one of an imaged security label, currency or passport security device.  
     
     
         13 . The security thread as defined in  claim 1 , wherein the thin film interference filter includes a color shifting ink.  
     
     
         14 . The security thread as defined in  claim 1  further comprising color shifting ink.  
     
     
         15 . The security thread as defined in  claim 1 , wherein the thin film interference filter includes an optically variable pigment.  
     
     
         16 . A method for forming an optically variable device upon a web, comprising the steps of: 
 patterning a reflective layer on a web having a first side and a second side using an oil-ablation technique;    removing oil residue from the first side of the web substrate; and    depositing thin-film layers supported by the web to form the optically variable device.    
     
     
         17 . A method as defined in  claim 16 , wherein the step of patterning the reflective layer is performed on the first side of the web, and wherein the thin-film layers are deposited on the first side of the web over the patterned reflective layer.  
     
     
         18 . The method of  claim 17 , further comprising the step of removing oil residue from the second side of the web.  
     
     
         19 . The method of  claim 16 , further comprising the step of depositing an optical structure over the patterned reflective layer, or behind the reflective layer on an opposite side of the web.  
     
     
         20 . The method of  claim 16 , wherein the step of removing oil residue comprises using a glow discharge.  
     
     
         21 . The method of  claim 20 , wherein the glow discharge is formed from a precursor comprising oxygen.  
     
     
         22 . The method of  claim 16 , wherein the oil ablation technique includes the step of applying oil in a pattern with an ink jet device.  
     
     
         23 . A security thread as defined in  claim 1  wherein the elongate substrate has an embossed diffractive pattern coated with a reflective layer on a side of the substrate opposite to the optically variable structure, such that the embossed pattern is at least partially visible from a side of the substrate having the interference structure.  
     
     
         24 . A security thread as defined in  claim 1  further comprising a magnetic layer disposed within and or between or behind the interference filters, wherein the magnetic layer has a thickness of less than about 5.0 microns.