METHOD FOR PRODUCTION OF LATENT REVERSIBLE IMAGE Russian patent published in 2001 - IPC

FIELD: production of reversible images that can be observed in certain physical conditions and make them invisible in other conditions. SUBSTANCE: hydrophilic sections in accordance with the image contours are produced by a film 50 to 200 nm thick. The hydrophilic film is applied either in the glow discharge plasma at direct or alternating current, or from a solution of hydrophilic substance. In case of use of the plasmochemical process the hydrophilic film consists of metallooxide layers on the surface. Conditions of application: vacuum at partial air or argon pressure of 10 Pa, material of the cathode-steel, titanium, tungsten or aluminum, the voltage at a high-frequency discharge within 400 to 1000V, and for a direct-voltage discharge the voltage within 1000 to 3000V. The discharge current in both cases is within 0.1 o 1.0 A. When hydrophilic substances are used, the film consists of molecules of saccharose, magnesium chloride, calcium chloride or similar hydrophilic substances. Development of image occurs due to optical contrast in the atmosphere of satured water vapor between the sections coated with a film of water (hydrophilic sections) and coated with water droplets (hydrophobic sections). EFFECT: enhanced reliability of protection of documents, securities against unauthorized reproduction and forgery. 2 cl