Method of marking a document or item; method and device for identifying the marked document or item; use of circular polarizing particles

• US 8,186,573 B2
• Filed: 04/18/2008
• Issued: 05/29/2012
• Est. Priority Date: 04/24/2007
• Status: Active Grant

• Current Assignee: Sicpa Holding SA
• Original Assignee: Sicpa Holding SA
• Inventors: Callegari, Andrea, Decoux, Eric
• Primary Examiner(s): Lee, Michael G
• Assistant Examiner(s): Mikels, Matthew
• Application Number:
  US12/597,047
• Publication Number:
  US 20100200649A1
• Time in Patent Office: 1,502 Days
• Field of Search: 235/375, 235/380, 235/385, 235/435, 235/439, 235/454, 235/457, 235/460
• US Class Current: 235/375
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00
• CPC Class Codes: G06K 19/00 Record carriers for use with machines and with at least a part designed to carry digital markings
• CPC Class Codes: G06K 19/086 with markings consisting of randomly placed or oriented elements, the randomness of the elements being useable for generating a unique identifying signature of the record carrier, e.g. randomly placed magnetic fibers or magnetic particles in the body of a credit card
• CPC Class Codes: G07D 7/003 using security elements using digital security elements G07D7/004
• CPC Class Codes: G07D 7/005 Testing security markings invisible to the naked eye, e.g. verifying thickened lines or unobtrusive markings or alterations
• CPC Class Codes: G07D 7/12 Visible light, infrared or ultraviolet radiation

Abstract

Optical identification and/or authentication of a document or item with the help of a marking comprising a random distribution of circular polarized light reflecting particles, the marking being applied to the document or item through an ink, and the reading device exploiting circular polarization to discriminate the flakes from the background.

Claims

1. A method of marking and identifying or authenticating an item, wherein the method comprises at least one of

(i) providing the item with a mark comprising randomly distributed cholesteric liquid crystal polymer (CLCP) flakes reflecting a circular polarized light component and recording and storing data representative of the random distribution using a first reading device that comprises illumination and optical detection units, and

(ii) identifying or authenticating the marked item by reading data representative of the random distribution with a second reading device that comprises illumination and optical detection units and comparing read data with stored data, the first and second reading devices detecting circular polarized light reflected from the CLCP flakes and discriminating the flakes from a background thereof by forming a circular polarization difference image.

2. The method of claim 1, wherein the circular polarization difference image is formed from two images obtained under different polarization conditions selected from unpolarized, left-circular polarized, and right-circular polarized.

3. The method of claim 1, wherein the circular polarization difference image is formed from two images obtained under left-circular polarized and right-circular polarized conditions, respectively.

4. The method of claim 1, wherein the CLCP flakes exhibit at least two spectral reflection bands in at least one of the ultraviolet, visible, and infrared electromagnetic spectrum.

5. The method of claim 4, wherein each spectral reflection band is individually left-handed polarized or right-handed circular polarized.

6. The method of claim 1, wherein the random distribution is produced or detected in an area of at least 1 mm².

7. The method of claim 1, wherein the random distribution is produced or detected in an area of at least 100 mm².

8. The method of claim 1, wherein the random distribution comprises from 3 to 1000 flakes.

9. The method of claim 1, wherein the random distribution comprises from 30 to 100 flakes.

10. The method of claim 1, wherein the data representative of the random distribution is obtained by selecting a number of flakes among a larger total number of flakes according to a pre-defined criterion.

11. The method of claim 10, wherein the pre-defined criterion comprises position.

12. The method of claim 10, wherein the pre-defined criterion comprises orientation.

13. The method of claim 10, wherein the pre-defined criterion comprises graphic design.

14. The method of claim 1, wherein each of the first and second reading devices comprises at least one circular polarizing filter.

15. The method of claim 14, wherein each of the first and second reading devices comprises a right-circular polarizing filter and a left-circular polarizing filter.

16. The method of claim 1, wherein each of the first and second reading devices comprises at least one color filter having a band pass in at least one of the ultraviolet, visible and infrared electromagnetic spectrum.

17. The method of claim 1, wherein the item is provided with the random distribution of CLCP flakes by at least one coating technique selected from coating or printing with a liquid composition, coating or printing with a pasty coating composition, coating or printing with a solid, and “

bronzing”

.

18. The method of claim 1, further comprising at least one of overprinting and coating the random distribution of CLCP flakes with indicia.

19. The method of claim 1, wherein the random distribution of CLCP flakes is applied on top of pre-existing indicia.

20. The method of claim 1, wherein the random distribution of CLCP flakes is applied by applying a preconfigured pattern of ink droplets.

21. The method of claim 1, wherein the item is provided with the random distribution of CLCP flakes in the form of at least one of a label, a laminate, a film, and a transfer foil.