US Patent 8360323 Security label laminate and method of labeling

A labeling method for marking a product with invisible information. The label includes a removable laminate formed from a light transmissive layer, and a light transmissive adhesive that detachably affixes the label to a product. The label includes an invisible marker that contains information, detectable by light of selected wavelength. The amount of marker selected is sufficient to allow information in the marker to be detected only when the laminate is affixed over a surface with a selected optical background. The label laminate is removed from the surface of the product and affixed to a surface having the selected optical background and is exposed to light that renders the information in the marker detectable. The method allows covert information in the label laminate to be reliably detected and read with the use of minimal quantities of marker material.