Abstract: Photochromic printing inks are disclosed which are in particular used for the printing of security documents. Prints are normally nearly colorless and become colored when energy irradiated, such as by ultraviolet light. This photocoloration is reversible. The printing inks contain photochromic compounds which are protected against other ink components. Methods are described to prepare the inks, to print security documents, and to detect counterfeiting.

Abstract: A printing ink for the printing of security documents by the method of engraved steel die printing, having a viscosity of at least 1 Pa.multidot.s at 40.degree. C. under a shear of about 1000 sec.sup.-1, containing a binder matrix, a polymerization initiator for polymerizable matrix components, fillers and pigments, and the usual additives. The binder matrix contains at least one cationically polymerizable compound, modified to bring about the desired rheology of the ink, and the photoinitiator, activable by UV, heat and EB, is an onium salt capable of releasing a Lewis or Bronsted acid.This ink has best and very rapid drying characteristics.

Abstract: Photochromic printing inks are disclosed which are in particular used for the printing of security documents. Prints are normally nearly colorless and become colored when energy irradiated, such as by ultraviolet light. This photocoloration is reversible. The printing inks contain photochromic compounds which are protected against other ink components. Methods are described to prepare the inks, to print security documents, and to detect counterfeiting.

Abstract: A printing ink for the printing of security documents by the method of engraved steel die printing, wherein the volatile solvents comprise at most 15%, referred to the total weight of the ink, of one or more volatile organic substances, and wherein the volatile matter may further contain water.These inks reply to the new environmental requirements and have still a better wipability on the printing cylinders or plates. They allow document printing without interleaving.

Abstract: A method for preparing a flexographic or gravure printing ink in dry, powdered form. The method comprises comminuting a blend of all ink components, the solvents excluded, under oxygen free and temperature controlled conditions. The powder obtained is homogeneous, dust free, solid, dry and free-flowing and provides a ready-for-use printing ink on simply stirring with the normally used solvents.

Abstract: A process for preventing the counterfeiting of valuable documents through use of photography, photocopying techniques, or other methods of counterfeiting. The process includes laminating an extremely thin metallic film to the substrate of the valuable document before the document is printed with the area of the metallic film being small in comparison to the area of the document. The metallic film can be located anywhere on the face of the document and a "latent image" is embossed on the metallic film when the document is printed. Embossing the latent image on the metallic film, rather than on the document substrate, provides many advantages not possible in the prior art.A photocopy of a document containing the embossed metallic film does not include the latent image and a color photocopy will be different in color than the original document. Therefore, a lay observer can readily differentiate between a genuine document and a counterfeit document.

Abstract: A printing ink for the printing of security documents by the method of engraved steel die printing, wherein the volatile solvents comprise at most 15%, referred to the total weight of the ink, of one or more volatile organic substances, and wherein the volatile matter may further contain water.These inks reply to the new environmental requirements and have still a better wipability on the printing cylinders or plates. They allow document printing without interleaving.