Machine-detectable security marking with an increased level of proof against forgery, production of the security marking, and security system comprising this security marking

• US 6,570,648 B1
• Filed: 11/20/2000
• Issued: 05/27/2003
• Est. Priority Date: 08/28/1997
• Status: Expired due to Term

• Current Assignee: Sicpa Holding SA
• Original Assignee: Wacker-Chemie GmbH (Dr. Alexander Wacker Familiengesellschaft Mit Beschrã¤Nkter Haftung)
• Inventors: Schwalb, Georg, Müller-Rees, Christoph, Küpfer, Jürgen, Leigeber, Horst
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M.
• Application Number:
  US09/716,688
• Time in Patent Office: 918 Days
• Field of Search: 356/71, 356/369, 356/364, 428/1.1, 428/916, 428/915, 428/913
• US Class Current: 356/71
• CPC Class Codes: B41M 3/14 Security printing securities B42D25/29
• 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 25/364 Liquid crystals
• CPC Class Codes: G03G 21/043 by using an original which is not reproducible or only reproducible with a different appearence, e.g. originals with a photochromic layer or a colour background
• CPC Class Codes: G06K 19/06046 Constructional details

Abstract

The invention relates to a security marking whose level of proof against forgery is increased relative to known security markings, comprising liquid-crystalline material with chiral phase, wherein present within the security marking are at least two liquid-crystalline materials with chiral phase which differ in at least one property selected from the group consisting of handedness, color and color flop and which are arranged in the form of a structured or unstructured marking or a multilayer marking or in the form of liquid-crystalline pigments in a liquid-crystalline matrix, or wherein there is at least one liquid-crystalline material with chiral phase whose reflection band has been broadened by means of special techniques, or wherein there is at least one liquid-crystalline material with chiral phase which has a defined three-dimensional arrangement.

Claims

1. A security marking, comprising a layer of liquid-crystalline material with chiral phase, wherein present within the security marking are at least two liquid-crystalline materials with chiral phase having a reflection band having a short wave flank and a long wave flank, such that the short wave flank of the reflection band is less than 700 nm when illuminated and viewed normal to the layer of said liquid-crystalline material with chiral phase, and such that the long wave flank of the reflection band is greater than 420 nm when illuminated at −

80°

from the normal to the surface of said liquid-crystalline material with chiral phase, and viewed at +80°

from the normal to the surface of said liquid-crystalline material, said two liquid-crystalline materials with chiral phase differing in color flop, and which are arranged in the form of a structured marking consisting of liquid crystalline pigments or unstructured marking or a multilayer marking or in the form of liquid-crystalline pigments in a liquid-crystalline matrix.

2. A process for producing a security marking as claimed in claim 1, which comprises arranging at least two liquid-crystalline materials with chiral phase which differ in color flop and optionally one or both of handedness or color, in the form of a structured or of an unstructured marking or of a multilayer marking or in the form of liquid-crystalline pigments in a liquid-crystalline matrix.

3. An article labeled with a security marking as claimed in claim 1.

4. The use of a security marking as claimed in claim 1 as a security element on data carriers, documents of value, and identity documents.

5. A security marking in accordance with claim 1 in which at least one liquid-crystalline material with chiral phase having a broadened reflection band is additionally employed.

6. A security marking in accordance with claim 1 in which said security marking is structured.

7. The security marking of claim 6 in which said security marking contains minimally two adjacent coplanar coatings which contain respective liquid-crystalline materials with chiral phase which differ from one another in color flop.

8. A test setup suitable for testing the genuineness of a security marking of claim 1, said test setup comprising:

a) a spectral detector comprising at least one of

a)i) a broad band light source, and at least one wavelength selective filter positioned between said broadband light source and a security marking to be tested or positioned between said security marking and a photodetector such that light reflected from said security marking and falling upon said photodetector is filtered broadband light having a spectral intensity distribution different from that of said broadband light;

or

a)ii) a light source emitting discrete wavelength(s), optionally having associated therewith one or more wavelength selective filters which filter the light from said light source emitting discrete wavelength(s) prior to said light falling upon said security marking, or positioned such that light from said light source emitting discrete wavelength(s) and reflected from said security marking passes through said one or more wavelength selective filters prior to falling upon a photodetector; and

optionally

b) a polarization and wavelength selective detector which detects the right- or left-handedness of light reflected from said security marking at one or more wavelengths;

wherein at least one of the following conditions is satisfied;

1) said spectral detector measures reflected light intensity from said security marking at at least two different wavelengths within the reflection bandwidth of at least one liquid-crystalline material having a chiral phase present in said security marking;

2) said spectral detector measures at least one reflected light intensity from said security marking within the spectral bandwidth of at least one liquid-crystalline material having a chiral phase present in said security marking, and said polarization and wavelength selective detector detects the right- or left-handedness of light reflected from said security marking at at least one wavelength within the reflection band of at least one liquid-crystalline material having a chiral phase present in said security marking.

9. The test setup of claim 8 wherein a plurality of wavelength selective filters positioned i) in succession between said security element and said light source;

ii) between said security marking and said photodetector;

or iii) at least one filter positioned between either said light source and said security marking or between said security marking and said photodetector, and two or more filters positioned in an alternative location so as to filter light impinging upon or reflected from said security marking, said alternative location different from the location of said at least one filter positioned as heretofore described.

10. The test setup of claim 8 wherein the characteristic form of the reflection band of at least one liquid-crystalline material having a chiral phase is measured by comparing the intensity of light reflected from a security marking being tested at a first wavelength which corresponds to the center wavelength of a liquid-crystalline material having a chiral phase present in a genuine security marking and the intensity of light reflected from said security marking being tested at a second wavelength which corresponds to a wavelength of a liquid-crystalline material having a chiral phase present in a genuine security marking, said second wavelength being a wavelength of said liquid-crystalline material in said genuine security

11. The test setup of claim 8 wherein a given wavelength of reflected light or range thereof is subjected to detection at a first angle normal to the surface of said security marking, and at a second angle, meeting the Bragg condition and which deviates from the normal to the surface to the same degree as the angle of illumination deviates from the normal.

12. The test setup of claim 8 wherein a polarization beam splitting device is positioned between a light source and a photodetector which is positioned to receive light from said light source which has been reflected from said security device.

13. A security system comprising a security marking and a test setup for recognizing the security marking, said test setup comprising at least one light source, at least one wavelength selective element polarization selective element, or both a wavelength selective element and polarization selective element and at least one photodetector which detects light reflected from said security marking, said light having passed through said wavelength selective element, said polarization selective element, prior to or following reflection from said security marking and prior to detection by said photodetector, wherein said security marking is a security marking as claimed in claim 1.

14. The security system as claimed in claim 4, wherein the test setup permits complete identification of one or more selected properties which are characteristic of the liquid-crystalline material with chiral phase.

15. The security system as claimed in claim 14, wherein the properties selected are one or more of the handedness, the color, or the color flop of the liquid-crystalline material with chiral phase or the defined arrangement of the material.

16. The security system of claim 13, wherein said test setup for recognizing a security marking comprises a test setup which detects the characteristic form of the reflection band of at least a portion of said security marking by determining the intensity of reflection at at least two spectrally different points of the reflection band.

17. The security system of claim 16, wherein said different points of the reflection band comprise the center wavelength and a second wavelength in the reflection band where the expected intensity of reflected light is less than 50% of the maximum.

18. The security system of claim 16, wherein said different points of the reflection band comprise the center wavelength and a second wavelength in the reflection band where the expected intensity of reflected light is less than 10% of the maximum.

19. The security system of claim 16, further comprising detecting color flop of said security marking by measuring the reflectance at one angle from the normal to the security marking and at a second angle to said normal to said security marking, said second angle greater than said first angle.

20. An object having a planar surface on which is located a security marking of claim 1, said security marking comprising at least one liquid-crystalline material with chiral phase in a defined three-dimensional arrangement such that said defined three-dimensional arrangement comprises at least two surfaces, a normal to at least one surface being disposed in space at a different angle to a normal to another surface of said at least two surfaces.