Abstract: A latent or “invisible ink” security marking formulation is provided using a phosphor with distinct emissions characteristics including visible emission due to excitation at a particular invisible wavelength. An insoluble inorganic phosphor with this or a similarly distinct emission characteristic is milled to a small particle size, preferably less than one micron particle diameter, and is combined with a carrier at very low pigment concentration, for example one percent by weight of the ink formulation. Preferably the pigment is cropped to resin particles in a binder. This ink formulation is diluted by a volatile solvent and applied using a conventional inkjet printer of the type used to mark codes on packages and labels. To test for security purposes the printing is irradiated and a response according to the predetermined characteristic is noted (or not noted) to detect security information.

Abstract: A document has information appearing thereon, with at least a portion of the information being located on a front face of a portion of the document. The front face portion has a color with a sufficiently low reflection spectral response to render the document portion substantially incapable of being photocopied in an information-readable manner. The document portion is capable of transmitting visible light from the rear face to the front face to cause sufficient contrast between the relatively non-translucent information and the transmitted light to enable the information to be read by a human eye viewing the front face of the document when visible light is transmitted through the document from the rear face to the front face.

Abstract: Confidential information is printed, typed or otherwise applied to paper with a color having a reflection spectral response or less than about 10% for light with a wave-length below about 600 millimicrons. The color is sufficiently contrasting with the information to enable the information to be read by the human eye when the document is viewed under white light, but the document cannot be successfully photocopied.