A security system, such as a banknote, comprises: i) a substrate, ii) a first ink, which is applied on at least a part of at least one surface of the substrate, wherein the first ink includes at least one IR luminescent dye and/or at least one IR luminescent pigment, and iii) a second non-luminescent ink, which is applied on at least a part of at least one surface of the substrate onto which the first ink is/are applied, wherein the second ink includes at least one non-luminescent IR absorbing pigment and/or a least one non-luminescent IR absorbing dye, wherein the first ink and the second ink at least partially overlap on the at least one surface of the substrate, wherein the second ink is applied in the overlapping area onto the first ink, and wherein the emission spectrum of the first ink and the absorption spectrum of the second ink at least partially overlap.

A security system, such as a banknote, comprises: i) a substrate, ii) a first ink, which is applied on at least a part of at least one surface of the substrate, wherein the first ink includes at least one IR luminescent dye and/or at least one IR luminescent pigment, and iii) a second non-luminescent ink, which is applied on at least a part of at least one surface of the substrate onto which the first ink is/are applied, wherein the second ink includes at least one non-luminescent IR absorbing pigment and/or a least one non-luminescent IR absorbing dye, wherein the first ink and the second ink at least partially overlap on the at least one surface of the substrate, wherein the second ink is applied in the overlapping area onto the first ink, and wherein the emission spectrum of the first ink and the absorption spectrum of the second ink at least partially overlap.

An IR and/or UV machine-readable optical security device (e.g., micro-optic security thread) that is made up of at least one IR-absorbing component with a characteristic IR signature detectable at two or more IR-wavelengths, at least one UV-absorbing component with a characteristic UV signature detectable at two or more UV-wavelengths, at least one IR-absorbing component that absorbs IR light and emits light at a different invisible wavelength, at least one UV-absorbing component that absorbs UV light and emits light at a different invisible wavelength, or a combination thereof, is provided. The IR and UV machine-readable features do not interfere with the optical effects projected by the optical material.

An IR and/or UV machine-readable optical security device (e.g., micro-optic security thread) that is made up of at least one IR-absorbing component with a characteristic IR signature detectable at two or more IR-wavelengths, at least one UV-absorbing component with a characteristic UV signature detectable at two or more UV-wavelengths, at least one IR-absorbing component that absorbs IR light and emits light at a different invisible wavelength, at least one UV-absorbing component that absorbs UV light and emits light at a different invisible wavelength, or a combination thereof, is provided. The IR and UV machine-readable features do not interfere with the optical effects projected by the optical material.

A printed object includes a substrate and a first information code disposed on the substrate, wherein: the first information code is constituted of an infrared ray-absorptive ink layer that has been printed with an infrared ray absorptive ink; and the infrared ray absorptive ink layer is configured such that, when a laminated body constituted of a test substrate made of the same material as that of the substrate, and a test infrared absorptive ink layer made of the same material as that of the infrared ray absorptive ink layer and disposed on the test substrate is subjected to a relative spectral reflectivity measurement on the test infrared ray absorptive ink layer side, with the test substrate as the reference (100% reflectivity), the minimum relative reflectivity in the visible region is 50% or higher, and the minimum relative reflectivity in the infrared region is 75% or lower.

A printed object includes a substrate and a first information code disposed on the substrate, wherein: the first information code is constituted of an infrared ray-absorptive ink layer that has been printed with an infrared ray absorptive ink; and the infrared ray absorptive ink layer is configured such that, when a laminated body constituted of a test substrate made of the same material as that of the substrate, and a test infrared absorptive ink layer made of the same material as that of the infrared ray absorptive ink layer and disposed on the test substrate is subjected to a relative spectral reflectivity measurement on the test infrared ray absorptive ink layer side, with the test substrate as the reference (100% reflectivity), the minimum relative reflectivity in the visible region is 50% or higher, and the minimum relative reflectivity in the infrared region is 75% or lower.

Techniques are described in which articles (e.g., security documents, traffic signage and personal protective equipment) are formed to include an infrared absorptive material. In some instances, the infrared absorptive material includes a reduced tungsten oxide, such as cesium tungsten oxide, calcium tungsten oxide, potassium tungsten oxide, or the like, and exposed to radiation such that one or more regions of the security document has a modified appearance, thereby providing a visual marking or information on the article. Example articles include at least one layer including a polymer and an infrared absorptive material including a reduced tungsten oxide. The layer includes a radiation-treated region that exhibits a first appearance under visible light and at least one non-radiation-treated region that exhibits a second, different appearance under visible light. The at least one radiation-treated region may be formed by exposing the at least one radiation-treated region to infrared light to change at least one property of the reduced tungsten oxide in the radiation-treated region compared to the reduced tungsten oxide in the non-radiation-treated region. The first appearance may be whiter than the second appearance.

Techniques are described in which articles (e.g., security documents, traffic signage and personal protective equipment) are formed to include an infrared absorptive material. In some instances, the infrared absorptive material includes a reduced tungsten oxide, such as cesium tungsten oxide, calcium tungsten oxide, potassium tungsten oxide, or the like, and exposed to radiation such that one or more regions of the security document has a modified appearance, thereby providing a visual marking or information on the article. Example articles include at least one layer including a polymer and an infrared absorptive material including a reduced tungsten oxide. The layer includes a radiation-treated region that exhibits a first appearance under visible light and at least one non-radiation-treated region that exhibits a second, different appearance under visible light. The at least one radiation-treated region may be formed by exposing the at least one radiation-treated region to infrared light to change at least one property of the reduced tungsten oxide in the radiation-treated region compared to the reduced tungsten oxide in the non-radiation-treated region. The first appearance may be whiter than the second appearance.

The use of a modified reduced indium tin oxide to provide a security image wherein the modified reduced indium tin oxide is obtained by heating indium tin oxide in a reducing atmosphere at a temperature of from 300 to 500° C.; and contacting the reduced indium tin oxide with an organophosphorus compound.

The use of a modified reduced indium tin oxide to provide a security image wherein the modified reduced indium tin oxide is obtained by heating indium tin oxide in a reducing atmosphere at a temperature of from 300 to 500° C.; and contacting the reduced indium tin oxide with an organophosphorus compound.