Security paper

• US 4,452,843 A
• Filed: 10/23/1981
• Issued: 06/05/1984
• Est. Priority Date: 05/30/1980
• Status: Expired due to Term

• Current Assignee: GAO Gesellschaft Fur Automation und Organisation mbH
• Original Assignee: GAO Gesellschaft Fur Automation und Organisation mbH
• Inventors: Kaule, Wittich, Schwenk, Gerhard, Stenzel, Gerhard
• Primary Examiner(s): Ives, P.
• Application Number:
  US06/314,844
• Time in Patent Office: 956 Days
• Field of Search: 428/403, 428/464, 428/438, 428/537, 428/690, 428/913, 428/916, 428/917, 428/918, 428/199, 428/204, 428/207, 428/333, 428/323
• US Class Current: 428/199
• CPC Class Codes: B41M 3/144 using fluorescent, luminescent or iridescent effects
• CPC Class Codes: B42D 2033/20 Coloured material; Pigments or inks
• CPC Class Codes: B42D 25/00 Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof printing processes to produce identification or security features B41M3/14
• CPC Class Codes: B42D 25/29 Securities; Bank notes
• CPC Class Codes: B42D 25/382 absorbing or reflecting infrared light
• CPC Class Codes: C09K 11/7701 Chalogenides
• CPC Class Codes: C09K 11/7769 Oxides C09K11/7768 takes precedence
• CPC Class Codes: D21H 21/48 Elements suited for physical verification, e.g. by irradiation
• CPC Class Codes: G06K 19/14 the marking being sensed by radiation
• CPC Class Codes: G07D 7/12 Visible light, infrared or ultraviolet radiation
• CPC Class Codes: G07D 7/121 Apparatus characterised by sensor details
• CPC Class Codes: Y10S 101/46 Printing operation controlled by code indicia on printing plate or substate
• CPC Class Codes: Y10S 428/908 Impression retention layer, e.g. print matrix, sound record
• CPC Class Codes: Y10S 428/913 Material designed to be responsive to temperature, light, moisture
• CPC Class Codes: Y10S 428/915 Fraud or tamper detecting
• CPC Class Codes: Y10S 428/917 Electroluminescent
• CPC Class Codes: Y10S 428/918 Material abnormally transparent
• CPC Class Codes: Y10T 428/24835 including developable image or soluble portion in coating or impregnation [e.g., safety paper, etc.]
• CPC Class Codes: Y10T 428/24876 Intermediate layer contains particulate material [e.g., pigment, etc.]
• CPC Class Codes: Y10T 428/24901 including coloring matter
• CPC Class Codes: Y10T 428/24934 : including paper layer
• CPC Class Codes: Y10T 428/25 : Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/261 : In terms of molecular thickness or light wave length
• CPC Class Codes: Y10T 428/2933 : Coated or with bond, impregnation or core
• CPC Class Codes: Y10T 428/2991 : Coated
• CPC Class Codes: Y10T 428/31703 : Next to cellulosic
• CPC Class Codes: Y10T 428/31993 : Of paper
• CPC Class Codes: Y10T 428/31996 : Next to layer of metal salt [e.g., plasterboard, etc.]

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.

Claims

1. A security document with authenticity features, comprising:

a substrate material, a luminescing substance on said carrier material, said luminescing substance comprising a host lattice doped with a rare earth metal, wherein said host lattice absorbs radiation in the visible region and is excited in at least one of the visible and near infrared regions and has an opticaly translucent region in the invisible optical spectrum in which said luminescing substance emits, and wherein the emission lines of the dopant are such that said host lattice absorbs radiation emitted by said dopant at least in the regions of the visible region whereby each emission from said dopant in the visible region is suppressed.

2. Security document according to claim 1, wherein said host lattice is excited in substantial portions of at least one of the visible range and near infrared range.

3. Security document according to claim 1, wherein the host lattice is a mixed lattice of a lattice absorbing in the visible region and a non-absorbing lattice of the same structure.

4. Security document according to claim 1, wherein said host lattice is doped with ions of the rare earth metals of atomic number 58 to 71.

5. Security document according to claim 3, wherein the proportion of absorbing to non-absorbing host lattice components determines the absorption ability of said luminescing substance.

6. Security document according to claim 1, wherein the optically translucent region lies between 0.8 and 10 μ

m.

7. Security document according to claim 6, wherein the optically translucent region lies between 1.1 and 10 μ

m.

8. Security document according to claim 1, wherein the host lattice includes absorbing elements comprising transition metal ions.

9. Security document according to claim 8, wherein said absorbing elements comprise metals of the sub groups VI, VII or VIII.

10. Security document according to claim 9, wherein said absorbing elements comprise cobalt, nickel, manganese or iron.

11. Security document according to claim 8, wherein the host lattice has a structure selected from the group consists of a garnet structure, a perovskite structure and ferrite structure.

12. Security document according to claim 11, wherein the garnet structure can be described by the general formula

13. Security document according to claim 12, wherein the host lattice is Y₃ Fe₄ Ni₀.5 Ge₀.5 O₁₂.

14. Security document according to claim 11, wherein the garnet structure can be described by the general formula

15. Security document according to claim 14, wherein the host lattice is Y₂ CaFe₄ SiO₁₂.

16. Security document according to claim 14, wherein the garnet structure can be described by the general formula

17. Security document according to claim 16, wherein the host lattice is Y₃ Fe₃ AL₂ O₁₂.

18. Security document according to claim 11, wherein the garnet structure can be described by the general formula

19. Security document according to claim 18, wherein the host lattice is Y Ca₂ Fe₄ VO₁₂.

20. Security document according to claim 11, wherein the host lattice has a perovskite structure according to the general formula

21. Security document according to claim 11, wherein the host lattice has a ferrite structure according to the general formula

22. Security document according to claim 1, including a printing ink on said substrate, and wherein said luminescing substance is mixed into said printing ink.

23. Security document according to claim 22, wherein said luminescing substance has an absorption ability dependent on the lightness of said printing ink used such that substantially no adulteration of the printing ink arises.

24. Security document according to claim 23, wherein the luminescing substance has a small absorption ability and said ink is very light.

25. Security document according to claim 23, wherein the luminescing substance has a relatively high absorption ability and said ink is dark.

26. Security document according to claim 1, wherein the luminescing substance is mixed into said substrate material composition.

27. Security document according to claim 1, wherein the luminescing substance is provided at least partly in large areas of said substrate material.

28. Security document according to claim 27, wherein the luminescing substance comprises strips.

29. Security document according to claim 1, wherein the luminescing substance comprises an invisible layer at least partly covering the carrier material.

30. Security document according to claim 26, wherein the luminescing substance is present in the bulk of the substrate material on correspondingly prepared mottling fibers.

31. Security document according to claim 26, wherein the luminescing substance is present in the bulk of the substrate material on a correspondingly prepared security thread.

32. Security document according to claim 1, wherein the excitation spectrum is matched to the emission spectrum of an illuminating test lamp such that said luminescent substance absorbs substantially all frequencies of radiation emitted by said lamp.

33. Security document according to claim 1, wherein said luminescent substance is a powder having a particle size less than 1 μ

m.