Method of detecting a concealed pattern

A coating system configured to enable detection of a concealed pattern, comprising:

• a first coating layer comprising a pattern disposed over a primer layer, the primer layer being disposed over at least a portion of the substrate, wherein the first coating layer forms the pattern in a shape of a machine-readable image, barcode, or QR code using a plurality of regions provided in part by the first coating layer and in part by the primer layer, wherein at least one region in the plurality comprises near-IR absorptive material, and at least one region in the plurality comprises near-IR emissive material;
• and
• a second coating layer applied over the first coating layer, the second coating layer comprising a visibly opaque layer that is substantially free of TiO2, the visibly opaque layer being near-IR transparent, the visibly opaque layer comprising an infrared transparent pigment disposed over the pattern,
• wherein the emissivity and/or absorbance of infrared electromagnetic radiation by the first coating layer at a wavelength in the range of 700 to 1100 nm differs from the emissivity and/or absorbance of the primer layer at the same wavelength;
• wherein the visibly opaque layer is substantially free of an infrared absorbing pigment and/or an infrared emissive pigment, such that the combination of near-IR absorptive and near-IR emissive material beneath the second coating layer is detectable through the second coating layer at the wavelength.

A coating system configured to enable detection of a concealed pattern, comprising:

• a first coating layer comprising a pattern disposed over at least a portion of the substrate, wherein the first coating layer forms the pattern in a shape of a machine-readable image, barcode, or QR code using a plurality of regions using a combination of near-IR absorptive and near-IR emissive material;
• and
• a second coating layer comprising a visibly opaque layer that comprises TiO2 in a form that is visibly opaque but transparent at a near-IR wavelength selected from the range of from 1100 nm to 2500 nm, the visibly opaque layer comprising TiO2 at an average particle size from 0.1 to 1 μm;
• wherein the emissivity and/or absorbance of infrared electromagnetic radiation by the pattern at a wavelength in the range of 1100 to 2500 nm differs from the emissivity and/or absorbance by the contrasting regions of the pattern of the first coating layer at the wavelength using regions of near-IR absorptive and near-IR emissive material;
• wherein the visibly opaque layer is substantially free of an infrared absorbing pigment and/or an infrared emissive pigment, such that the combination of near-IR absorptive and near-IR emissive material beneath the second coating layer is detectable through the second coating layer at the wavelength;
• wherein the near-IR emissive material comprises an infrared fluorescent pigment.