Optically variable security devices

Abstract

A security article includes a light transmissive substrate having a first surface and an opposing second surface, with the first surface having an optical interference pattern such as a holographic image pattern or an optical diffraction pattern thereon. A color shifting optical coating is formed on the substrate such as on the interference pattern or on the opposing second surface of the substrate, with the optical coating providing an observable color shift as the angle of incident light or viewing angle changes. Various processes can be utilized to form the security article, such as vacuum coating processes, lamination, laser scribing, and laser imaging. The security article can be affixed to a variety of objects through various attachment mechanisms, such as pressure sensitive adhesives or hot stamping processes, to provide for enhanced security measures such as anticounterfeiting.

What is claimed and desired to be secured by United States Letters Patent is:  
     
         1 . A security article, comprising: 
 (a) a light transmissive substrate having a first surface and an opposing second surface, the first surface having an optical interference pattern associated therewith, said optical interference pattern comprises microstructures having dimensions in the range from about 0.1 microns to about 10 microns; and    (b) a color shifting multilayer optical coating overlying the second surface of the substrate.    
     
     
         2 . The security article of  claim 1 , wherein the microstructures have dimensions in the range from about 0.1 microns to about 1 micron.  
     
     
         3 . The security article of  claim 1 , wherein the color shifting multilayer optical coating comprises: 
 an absorber layer overlying the second surface of the substrate;    a dielectric layer overlying the absorber layer; and    a reflector layer overlying the dielectric layer.    
     
     
         4 . The security article of  claim 1 , wherein the color shifting multilayer optical coating comprises: 
 an absorber layer overlying the second surface of the substrate;    a dielectric layer overlying the absorber layer; and    an absorber layer overlying the dielectric layer.    
     
     
         5 . The security article of  claim 1 , wherein the color shifting multilayer optical coating comprises alternating layers of low and high index of refraction dielectric layers.  
     
     
         6 . The security article of  claim 1 , wherein the color shifting multilayer optical coating comprises a plurality of multilayer color shifting flakes dispersed in a polymeric medium.  
     
     
         7 . The security article of  claim 1 , further comprising a laser ablated image formed in said optical coating.  
     
     
         8 . The security article of  claim 1 , further comprising an adhesive layer laminating said optical coating to said second surface of the substrate.  
     
     
         9 . The security article of  claim 1 , wherein said security article is in the form of a security thread.  
     
     
         10 . The security article of  claim 1 , further comprising an adhesive layer overlying the optical coating for securing the security article to an object.  
     
     
         11 . The security article of  claim 1 , wherein the optical interference pattern is formed on said light transmissive substrate.  
     
     
         12 . The security article of  claim 1 , wherein the optical interference pattern is on a layer secured to the light transmissive substrate.  
     
     
         13 . A security article comprising: 
 (a) a light transmissive substrate having a first surface and an opposing second surface, the first surface having an optical interference pattern associated therewith;    (b) a color shifting multilayer optical coating overlying the second surface of the substrate; and    (c) a laser ablated image formed in said optical coating.    
     
     
         14 . The security article of  claim 13 , wherein the optical interference pattern comprises microstructures having dimensions in the range from about 0.1 microns to about 10 microns.  
     
     
         15 . The security article of  claim 13 , wherein the optical interference pattern comprises microstructures having dimensions in the range from about 0.1 microns to about 1 micron.  
     
     
         16 . The security article of  claim 13 , wherein the color shifting multilayer optical coating comprises: 
 an absorber layer overlying the second surface of the substrate;    a dielectric layer overlying the absorber layer; and    a reflector layer overlying the dielectric layer.    
     
     
         17 . The security article of  claim 13 , wherein the color shifting multilayer optical coating comprises: 
 an absorber layer overlying the second surface of the substrate;    a dielectric layer overlying the absorber layer; and    an absorber layer overlying the dielectric layer.    
     
     
         18 . The security article of  claim 13 , wherein the color shifting multilayer optical coating comprises alternating layers of low and high index of refraction dielectric layers.  
     
     
         19 . The security article of  claim 13 , wherein the color shifting multilayer optical coating comprises a plurality of multilayer color shifting flakes dispersed in a polymeric medium.  
     
     
         20 . The security article of  claim 13 , further comprising an adhesive layer laminating said optical coating to said second surface of the substrate.  
     
     
         21 . The security article of  claim 13 , wherein said security article is in the form of a security thread.  
     
     
         22 . The security article of  claim 13 , further comprising an adhesive layer overlying the optical coating for securing the security article to an object.  
     
     
         23 . The security article of  claim 13 , wherein the optical interference pattern is formed on said light transmissive substrate.  
     
     
         24 . The security article of  claim 13 , wherein the optical interference pattern is on a layer secured to the light transmissive substrate.  
     
     
         25 . A security article comprising: 
 (a) a light transmissive substrate having a first surface and an opposing second surface, the first surface having an optical interference pattern associated therewith; and    (b) a color shifting multilayer optical coating overlying the second surface of the substrate, and    (c) an adhesive layer laminating said optical coating to said second surface.    
     
     
         26 . The security article of  claim 25 , wherein the optical interference pattern comprises microstructures having dimensions in the range from about 0.1 microns to about 10 microns.  
     
     
         27 . The security article of  claim 25 , wherein the optical interference pattern comprises microstructures having dimensions in the range from about 0.1 microns to about 1 micron.  
     
     
         28 . The security article of  claim 25 , wherein the color shifting multilayer optical coating comprises: 
 an absorber layer overlying the second surface of the substrate;    a dielectric layer overlying the absorber layer; and    a reflector layer overlying the dielectric layer.    
     
     
         29 . The security article of  claim 25 , wherein the color shifting multilayer optical coating comprises: 
 an absorber layer overlying the second surface of the substrate;    a dielectric layer overlying the absorber layer; and    an absorber layer overlying the dielectric layer.    
     
     
         30 . The security article of  claim 25 , wherein the color shifting multilayer optical coating comprises alternating layers of low and high index of refraction dielectric layers.  
     
     
         31 . The security article of  claim 25 , wherein the color shifting multilayer optical coating comprises a plurality of multilayer color shifting flakes dispersed in a polymeric medium.  
     
     
         32 . The security article of  claim 25 , further comprising a laser ablated image formed in said optical coating.  
     
     
         33 . The security article of  claim 25 , wherein said security article is in the form of a security thread.  
     
     
         34 . The security article of  claim 25 , further comprising an adhesive layer overlying the optical coating for securing the security article to an object.  
     
     
         35 . The security article of  claim 25 , wherein the optical interference pattern is formed on said light transmissive substrate.  
     
     
         36 . The security article of  claim 25 , wherein the optical interference pattern is on a layer secured to the light transmissive substrate.