Document with an optical diffraction safety element

• US 4,984,824 A
• Filed: 02/15/1989
• Issued: 01/15/1991
• Est. Priority Date: 03/03/1988
• Status: Expired due to Term

• Current Assignee: OVD Kinegram AG (Leonhard KURZ Stiftung & Company KG)
• Original Assignee: LGZ Landis & Gyr Zug AG (Landis+Gyr Group AG)
• Inventors: Saxer, Christian, Antes, Gregor
• Primary Examiner(s): Bell, Paul A.
• Application Number:
  US07/311,596
• Time in Patent Office: 699 Days
• Field of Search: 283/91, 283/72, 283/85, 283/86, 283/901, 283/904, 350/3.6, 350/3.61, 350/3.7, 350/3.73, 350/162.17, 350/162.18, 350/162.2, 350/162.23, 356/71
• US Class Current: 283/91
• CPC Class Codes: B42D 2035/44 Miniaturised markings
• 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 25/324 Reliefs
• CPC Class Codes: B42D 25/328 Diffraction gratings; Holograms
• CPC Class Codes: B42D 25/41 using electromagnetic radiation B42D25/435 takes precedence
• CPC Class Codes: B42D 25/425 by deformation, e.g. embossing
• CPC Class Codes: D21H 21/48 Elements suited for physical verification, e.g. by irradiation
• CPC Class Codes: G03H 1/0011 for security or authentication holograms on information-bearing cards B42D25/328; testing papers with holograms G07D7/0032
• CPC Class Codes: G03H 1/0276 Replicating a master hologram without interference recording surface relief holograms G03H1/0244
• CPC Class Codes: G03H 1/028 by embossing
• CPC Class Codes: G03H 1/0476 Holographic printer G03H1/268 takes precedence
• CPC Class Codes: G03H 2001/0016 Covert holograms or holobjects requiring additional knowledge to be perceived, e.g. holobject reconstructed only under IR illumination
• CPC Class Codes: G03H 2001/0284 by moulding
• CPC Class Codes: G03H 2001/0288 by electroforming
• CPC Class Codes: G03H 2001/0296 Formation of the master hologram
• CPC Class Codes: G03H 2001/0497 Dot matrix holograms
• CPC Class Codes: G03H 2001/187 Trimming process, i.e. macroscopically patterning the hologram
• CPC Class Codes: G03H 2210/55 Having particular size, e.g. irresolvable by the eye
• CPC Class Codes: G03H 2224/06 Thermal or photo-thermal means
• CPC Class Codes: G03H 2230/10 Microhologram not registered to the substrate
• CPC Class Codes: Y10S 283/904 : Credit card

Abstract

A document with an embossed macroscopic structure and acting through optical diffraction is disclosed. The structure, which serves as a security element comprises a plurality of surface portions with predetermined relief structures having spatial frequencies of over 10 lines/mm. Each surface portion is different from directly adjoining surface portions and at least some of the surface portions have a maximum dimension of less than 0.3 mm. To the naked eye, the pattern of surface portions on the document appears as a mesh of dots and lines. However, to an examiner with a magnifying device, the dots and lines appear as numbers, characters or other graphic features.

Claims

1. A document comprising

an embossed microscopic structure which operates through optical diffraction to serve as a security element for preventing unauthorized copying, said embossed structure including numerous surface portions,

each of said surface portions having a predetermined relief structure with a spatial frequency larger than 10 lines/mm, each relief structure of each surface portion being different from that of adjoining surface portions, and

a group of said surface portions having a predetermined geometric shape which carries security information and a largest dimension of less than 0.3 mm.

2. The document of claim 1 wherein said geometric shape of each surface portion of said group forms a character.

3. The document of claim 1 wherein said surface portions of said group are aligned in a row whereby the distance between them is less than 0.3 mm, said row forming a straight or curved line when viewed with the naked eye.

4. The document of claim 1 or 3 wherein said group of surface portions forms a predetermined macroscopic pattern of lines and dots which are each formed by one of said geometric shapes when viewed with the naked eye.

5. The document of claim 1 wherein said group of surface portions forms a predetermined macroscopic pattern of lines and dots when viewed with the naked eye, and a second determined pattern of geometric shapes when viewed with a magnifying device.

6. The document of claim 1 wherein said structure is embossed in a plastic film to be applied to an object to be protected.

7. The document of claim 1 wherein said structure is formed in a layer which is applied by a printing method.

8. A security element for preventing unauthorized copying which operates by diffracting light comprising:

a plurality of embossed surface portions, each of said embossed surface portions having a predetermined relief structure with a spatial frequency larger than 10 lines/mm for diffracting incident light;

each relief structure of each surface portion being different from the relief structure of directly adjoining surface portions;

one group of said surface portions having a predetermined geometric shape for carrying security information and having a largest dimension less than 0.3 mm to provide a first pattern which can be seen with the naked eye and a second pattern which can be seen only with a magnifying device.

9. A security element for preventing unauthorized copying comprising

an embossed microscopic structure which operates through optical diffraction, said embossed structure including numerous surface portions,

each of said surface portions having a predetermined relief structure with a spatial frequency larger than 10 lines/mm, each relief structure of each surface portion being different from that of adjoining surface portions, and

a group of said surface portions having predetermined geometric shape for carrying authenticity information and a largest dimension of less than 0.3 mm, said group of surface portions standing against a background by the color and luminosity of radiation diffracted thereby.

10. A document comprising

an embossed microscopic structure which operates through optical diffraction to serve as a security element for preventing unauthorized copying, said embossed structure including numerous surface portions,

each of said surface portions having a predetermined relief structure with a spatial frequency larger than 10 lines/mm, each relief structure of each surface portion being different from that of adjoining surface portions, and

a group of said surface portions having a predetermined geometric shape for carrying authenticity information and a largest dimension of less than 0.3 mm, said relief structures of said group of surface portions having the same orientation and spatial frequency to increase the visibility of said group when a magnifying device is utilized.

11. A document comprising

an embossed microscopic structure which operates through optical diffraction to serve as a security element for preventing unauthorized copying, said embossed structure including numerous surface portions,

each of said surface portions having a predetermined relief structure with a spatial frequency larger than 10 lines/mm, each relief structure of each surface portion being different from that of adjoining surface portions, and

one group of said surface portions having a largest dimension less than 0.3 mm to provide a first pattern of lines and dots which can be seen with the naked eye and a second pattern which can be seen only with a magnifying device, said group of surface portions having relief structures with the same orientation and spatial frequency.