Security Feature for Value Documents
AssigneesRainer Hoppe, Thomas Giering
InventorsRainer Hoppe, Thomas Giering
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Abstract
The present invention relates to a security feature for security papers, value documents and the like having an acid-labile feature substance as the core and a shell consisting substantially of metal oxide, the security feature exhibiting greater stability against the action of acids compared with the acid-labile feature substance.
Claims50
A security feature for security papers, value documents and the like having an acid-labile feature substance as the core and a shell consisting substantially of metal oxide, characterized in that the security feature exhibits greater stability against the action of acids compared with the acid-labile feature substance, and indium tin oxide is used as the acid-labile feature substance.
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A method for manufacturing a security feature for security papers, value documents and the like that exhibits an acid-labile feature substance as the core and a shell consisting substantially of metal oxide, characterized in that one or more feature substances are dispersed in a solvent under basic conditions at a pH>8, preferably >9, and subsequently one or more metal oxide precursors dissolved in a solvent are slowly added by drops with vigorous stirring of the presented dispersion of the feature substance, subsequently the precipitate that forms in the course of the reaction of the feature substances and the metal oxide precursors is separated from the supernatant solution, after separation, the precipitate is annealed at elevated temperatures, water, ethanol or a water/ethanol mixture is used as the solvent, and one or more luminescent substances with characteristic luminescence properties are added as the acid-labile feature substance.
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Dependencies are inferred from the claim text.