Security paper

US4452843A · kind A · utility

Assignee

• GAO Gesellschaft für Automation und organisation mbH · DE

Inventors

• Wittich Kaule · Grafing, DE
• Gerhard Schwenk · Puchheim, DE
• Gerhard Stenzel · Germering, DE

Key dates

• Filing date: Oct 23, 1981
• Grant date: Jun 5, 1984
• Expiry date: Oct 23, 2001

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/31996
• WIPO field: Other consumer goods
• WIPO sector: Other fields

Abstract

Security papers with luminescing authenticity characteristics built in or printed thereon which absorb in the visible region of the optical spectrum but in the infrared have a transparent region in which the luminophore also emits. By the absorption in the visible undesired parasitic emissions are suppressed which would make the luminophore visually evident on corresponding excitation. For testing the authenticity of the document the emission is investigated in the infrared. Suitable luminophores are rare earth metal luminophores in suitable host lattices, particularly in ferrite lattices or garnet lattices, which contain transition metal ions as absorbing elements.