Methods of forming and detecting non-visible marks and articles marked in accordance with the methods

A method of forming an infrared detectable mark on a substrate comprising:

• applying a marking material comprising an infrared reflective inorganic pigment to the substrate to form the mark;
• applying a contrast marking material to the substrate to form a contrast mark proximal to the mark, wherein the infrared reflective inorganic pigment causes the mark to reflect radiation at a predetermined wavelength within the range of from about 0.75 μm to about 40 μm at a sufficiently different level than the contrast mark such that the mark can be discerned from the contrast mark at the predetermined wavelength, wherein at least one of the mark and the contrast mark is formed using a laser marking system;
• and
• applying a cover coating material comprising an inorganic pigment that is different than the infrared reflective inorganic pigment in the marking material over the mark and the contrast 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 both the mark and the contrast 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 contrast mark through the cover coat at the predetermined wavelength.

A method of forming an infrared detectable mark on a substrate comprising:

• applying a marking material comprising an infrared reflective inorganic pigment to the substrate to form the mark;
• applying a masking material over a least a portion of the mark and, optionally, over a portion of the substrate, to form a mask, 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 mask such that the mark can be discerned from the mask at the predetermined wavelength, wherein at least one of the mark and the mask is formed using a laser marking system;
• and
• applying a cover coating material comprising an inorganic pigment that is different than the infrared reflective inorganic pigment in the marking material over the mark and the mask 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 both the mark and the mask 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 mask through the cover coat at the predetermined wavelength.

An article marked with a non-visible authentication mark comprising a laser mark disposed between a surface of the article and a cover coating layer that covers the laser mark and at least a portion of the substrate surrounding the laser mark, wherein the laser mark comprises an infrared reflective inorganic pigment and the cover coating layer comprises an inorganic pigment that is different than the infrared reflective inorganic pigment in the laser mark, wherein the cover coating layer 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 infrared reflective inorganic pigment in the laser mark causes the laser mark to reflect radiation at a predetermined wavelength within the range of from about 0.75 μm to about 40 μm at a sufficiently different level than the surface of the article beneath the cover coating adjacent to the laser mark, and wherein the cover coating layer appears substantially opaque in the visible portion of the electromagnetic spectrum such that it conceals the laser 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 that the laser mark can be discerned from the surface of the article beneath the cover coating adjacent to the laser mark through the cover coating layer at the predetermined wavelength.