Patent ID: 8006909

Claim:
A method of forming an infrared detectable mark on a substrate comprising: forming the mark on the substrate using a laser marking system and a laser marking composition comprising an infrared reflective inorganic pigment, wherein the infrared reflective inorganic pigment causes the mark to reflect radiation at a predetermined wavelength within the range of 0.75 μm to 40 μm at a sufficiently different level than the substrate adjacent to the mark such that the mark can be discerned from the substrate at the predetermined wavelength; and applying a cover coating material comprising an inorganic pigment that is different than the infrared reflective inorganic pigment in the laser marking composition over the mark and over at least a portion of the substrate adjacent to the mark to form a cover coat, wherein the cover coat is in the form of a film selected from the group consisting of paint films, porcelain enamel coating films, glass enamel coating films, extruded plastic films and laminated plastic films, wherein the cover coat appears substantially opaque in the visible portion of the electromagnetic spectrum such that it conceals the mark covered by the cover coat in the visible portion of the electromagnetic spectrum but is sufficiently transmissive of radiation emitted at the predetermined wavelength such that the mark can be discerned from the substrate through the cover coat at the predetermined wavelength.