IR METAMERIC INKS

Inks which have similar spectral features in visible light (perceived as having the same color) but different under IR illumination (some inks absorb IR light, others reflect). When examining an image printed using IR metameric inks, only a part of the image is visible in IR light. This security feature is based on the ability of document materials and inks to absorb or reflect IR light.

a                                                                 b

a —  Paper substrate. White light; 

b — Text fragments which absorb IR light look dark. The background image is transparent in IR light. IR light

a — Paper substrate. White light; 

b —  Fragments of the image and text are different in the degree of IR light absorption. So, they look semitransparent or dark on the light background. IR light