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.

1 . A security article comprising: 
 a substrate;    a diffractive grating having a grating pattern on or supported by the substrate;    an optically variable coating supported by the substrate visible through the diffractive grating, wherein the optically variable coating includes an absorber layer, a dielectric layer and a reflector layer for providing an observable color shift as the angle of incident light or viewing angle changes, and whereby the reflector layer or the diffractive grating is segmented.    
   
   
       2 . A security article as defined in  claim 1  whereby the reflector layer is segmented.  
   
   
       3 . A security article as defined in  claim 2 , whereby when the article is irradiated with light a first visual effect is present from incident light reflecting from the optically variable coating, wherein a second visual effect is present from incident light diffracting from the diffractive grating and wherein a third visual effect is present resulting from an interaction between light reflecting from the optically variable coating and light diffracted from the diffractive grating.  
   
   
       4 . A security article as defined in  claim 1  whereby the diffractive grating is segmented.  
   
   
       5 . A security article as defined in  claim 4 , whereby when the article is irradiated with light a first visual effect is present from incident light reflecting from the optically variable coating, wherein a second visual effect is present from incident light diffracting from the diffractive grating and wherein a third visual effect is present resulting from an interaction between light reflecting from the optically variable coating and light diffracted from the diffractive grating.  
   
   
       6 . A security article as defined in  claim 3  wherein the reflector layer is semi-transmitting.  
   
   
       7 . A security article as defined in  claim 5 , wherein the reflector layer is segmented.  
   
   
       8 . A security article as defined in  claim 1  wherein a portion of beam of light incident upon the security article from a side closest to the diffractive grating is conditioned by the grating in the absence of color shifting effects and wherein another portion of the beam is conditioned by the grating and subsequently by interference filters to provide color shifting effects reflected back through the diffractive grating.  
   
   
       9 . A security article as defined in  claim 2  wherein contrasting effects as a result of reflector layer being segmented are visible to a viewer viewing the security article through the substrate.  
   
   
       10 . A security article as defined in  claim 4  wherein contrasting effects as a result of diffraction grating being segmented are visible to a viewer viewing the security article through the substrate.  
   
   
       11 . A security article for providing an image with an optically variable effect comprising: 
 a substrate having a first side and a second side;    an optically variable structure supported by the first side of the substrate for providing the optically variable effect, and    a diffractive structure supported by the substrate, wherein an optical effect is seen from a segmented layer supported by the substrate when viewing the security article through the substrate.