Quantum dot security device and method

• US 20020021003A1
• Filed: 09/18/2001
• Published: 02/21/2002
• Est. Priority Date: 12/31/1998
• Status: Active Grant

• Current Assignee: McGrew, Stephen P.
• Original Assignee: McGrew, Stephen P.
• Inventors: McGrew, Stephen P.
• Granted Patent: US 6,692,031 B2
• Time in Patent Office: Days
• US Class Current: 283/93
• CPC Class Codes: B41M 3/144 using fluorescent, luminescent or iridescent effects
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C09D 11/50 Sympathetic, colour changing or similar inks
• CPC Class Codes: G07D 7/0032 using holograms
• CPC Class Codes: G07D 7/128 Viewing devices
• CPC Class Codes: Y10S 283/901 Concealed data

Abstract

Quantum dots are used as fluorescent taggants in security inks, papers, plastics, explosives, or any other item or substance in which it is desired to provide a distinct signature or marking. Quantum dots of specific sizes, compositions and structures may be used to produce specific fluorescence, mixtures of quantum dots can be used to produce random patterns of spectrally varying fluorescence, and particular quantum dot structures can be used to provide desirable physical and optical properties. The quantum dots may be read with an optical reader, which may be combined with readers using other technologies.

Claims

1. An anti-counterfeit device comprising quantum dots applied in a predetermined pattern, the dots having specific optical or physical properties in predetermined parts of the pattern.

2. An anti-counterfeit device comprising quantum dots applied to a surface, the quantum dots having detectable properties such that the properties vary randomly from point to point on the surface.

3. The anti-counterfeit device of claim 2 wherein the quantum dots are arranged in clusters of quantum dots.

4. The anti-counterfeit device of claim 2, wherein the surface comprises a paper surface having a surface overcoated with a transparent layer.

5. The anti-counterfeit device of claim 4, wherein the transparent layer comprises a transparent hologram hot-stamped to the paper.

6. The anti-counterfeit device of claim 2, wherein the quantum dots are applied by mixing them into a liquid carrier, coating the liquid carrier onto the surface, and hardening the carrier by drying or curing.

7. A data recording medium comprising quantum dots of random sizes arrayed in regions on a surface, the quantum dots being selectively altered such that information is encoded in the distribution or selection of properties of the quantum dots in each of the regions.

8. The data recording medium of claim 7 wherein the act of selectively altering the quantum dots comprises selectively altering the quantum dots by illumination of selected regions using light having a controlled, variable wavelength.

9. A data recording medium comprising quantum dots of specific properties bound to selected regions on a surface such that information is encoded in the distribution or selection of properties of the quantum dots in each region.

10. The data recording medium of claim 9 wherein the quantum dote are bound to selected regions on a surface by optically controlled chemical or physically controlled binding.

11. An anticounterfeit/security system comprising:

a document bearing quantum dots in a detectable arrangement, and

a reader adapted for detecting the presence and arrangement of at least a portion of the quantum dots on the document.

14. A product manufactured according to the method of claim 13.

16. The fluorescent ink of claim 15 wherein the carrier comprises a UV-curable resin.

17. A product made by printing the fluorescent ink of claim 16 onto a surface.

12. An anticounterfeit/security system comprising:

means for applying quantum dots to a document in a detectable arrangement;

means for detecting the presence and arrangement of the quantum dots on at least a portion of the document;

means for comparing the arrangement to a reference.

13. A method of tagging a substance, comprising adding quantum dots to the substance, the quantum dots having a predetermined detectable distribution of properties such that the absence, or alteration of the distribution of properties in a sample can be detected.

15. A fluorescent ink comprising quantum dots of a predetermined size distribution suspended in a dryable or curable liquid carrier.

18. A product having enhanced counterfeit-resistance, the product being made by the method comprising combining quantum dots with at least one of another printing, embossing, marking, tagging, or counterfeit-resistant feature or component.

19. An ink or other marking composition comprising quantum dots in a dryable or curable binding matrix liquid.

20. A fluorescent coating comprising a layer of hardenable liquid containing a suspension of quantum dots placed on a surface and then hardened.

21. A security thread for use in security marking objects, comprising a thread coated with a plurality of quantum dots.

22. A security label reader comprising:

means for illuminating a plurality of regions on a label;

means for detecting fluorescent light emitted by sub-microscopic objects such as quantum dots on the label, and

means for determining if the emitted fluorescent light has characteristics typical of quantum dot fluorescence.

24. The security label reader of claim 23 wherein the means for measuring the characteristics of the fluorescent light comprise means for measuring the fluorescence lifetime of the fluorescent light.

25. The security label reader of claim 23 wherein the means for measuring the characteristics of the fluorescent light comprise means for measuring the fluorescence spectrum of the fluorescent light.

28. The remote security tag verifier of claim 27, where the means for measuring the spectral and temporal characteristics of the fluorescent fluorophores comprises means for distinguishing quantum dot fluorescence from the fluorescence of organic dyes by emission bandwidth or fluorescence lifetime.

29. The remote security tag verifier of claim 28, wherein the means for distinguishing comprises means for modulating the light from the illumination source and comparing the resulting phase difference between the modulation of the illumination source light and the fluorescent light.

30. The verifier of claim 28, wherein the means for distinguishing comprises means for analyzing the spectrum of the fluorescence.

31. The verifier of claim 28, wherein the means for distinguishing comprises means for measuring the fluorescence intensity at a plurality of predetermined wavelengths and/or times.

23. A security label reader comprising:

means for illuminating small regions on a label;

means for detecting fluorescent light emitted by sub-microscopic objects such as quantum dots on the label;

means for measuring the characteristics of the fluorescent light;

means for moving the reader relative to the label such that the reader reads multiple locations on the label in an approximately predetermined pattern and sequence, and

means for representing the sequence and characteristics of the fluorescent light as a string of characters.

26. A label system for impeding counterfeiting, comprising:

a substrate defining a label base having one side for attachment to a product or packaging therefore and an opposite product identification side;

features on the product identification side in the form of detectable features, the features being in random locations,

means for detecting the properties and/or locations of the features,

means for applying visible indicia on the product identification side, the indicia incorporating an encrypted message derived from the properties and/or locations; and

means for reading the indicia, detecting the properties and the locations and decrypting at least a portion of the indicia to determine the inclusion or non-inclusion of the message.

27. A remote security tag verifier comprising:

an illumination source having a first, relatively short range of wavelengths,

means to direct light from the illumination source to a security tag;

light gathering means to detect fluorescent light emitted by an object illuminated by light from the illumination source, and

means for measuring the spectral and temporal characteristics of the fluorescent light and thereby determining if the tag contains a particular mix of specific fluorophores.