Abstract: Quantum dots are used as fluorescent taggants in security inks, papers, plastics, explosives, or any other item or substance in which it is desired to provide a distinct signature or marking. Quantum dots of specific sizes, compositions and structures may be used to produce specific fluorescence, mixtures of quantum dots can be used to produce random patterns of spectrally varying fluorescence, and particular quantum dot structures can be used to provide desirable physical and optical properties. The quantum dots may be read with an optical reader, which may be combined with readers using other technologies.

Abstract: Security paper having a number of parallel lines having a substantially uniform first spacing, irregularly interrupted by a plurality of stripes having a second spacing greater than the first spacing, is flexographically printed on at least one face of a web which becomes, after further processing, a security document such as a bank check. The parallel lines typically are substantially straight and of substantially uniform thickness and formed of flexo ink, such as the type which becomes invisible when bleached. Alphanumeric indicia are preferably provided within the stripes either oriented parallel to the parallel lines (and alternately extending from top to bottom, and bottom to top), or perpendicular to the parallel lines. A pattern is provided that repeats at an interval significantly greater than the length of the security document formed from the security paper.

Abstract: A pad of bank checks in which the check pad comprises multiple logos containing advertising coupons which are designed to be perforated for easy removal, and a series of bank checks each with a rotating advertising logo and/or slogan matching the sequential representation of the coupons.