Quantum dot security device and method

• US 6,692,031 B2
• Filed: 09/18/2001
• Issued: 02/17/2004
• Est. Priority Date: 12/31/1998
• Status: Expired due to Term

• Current Assignee: Stephen P. Mcgrew
• Original Assignee: Stephen P. Mcgrew
• Inventors: McGrew, Stephen P.
• Primary Examiner(s): CARTER, MONICA SMITH
• Application Number:
  US09/955,808
• Publication Number:
  US 20020021003A1
• Time in Patent Office: 882 Days
• Field of Search: 283/87, 283/72, 283/91, 283/92, 283/93, 283/901, 283/57-59, 382/116, 382/135, 382/137, 382/191, 399/15, 399/16, 399/17, 399/47, D19/11
• 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 to a substrate in a pattern, the quantum dots having sizes, compositions and structures which at least partially determine the fluorescence properties of the quantum dots such that the pattern of quantum dots produces fluorescence signatures upon illumination with excitation light, the fluorescence signatures having a relatively narrow emission spectrum, a relatively long fluorescence lifetime, and a fluorescence spectrum peak correlated to quantum dot diameter.

2. An anti-counterfeit device comprising quantum dots applied to a surface in a random pattern, the quantum dots having sizes, compositions and structures which at least partially determine the fluorescence properties of the quantum dots such that the pattern of quantum dots produces fluorescence signatures upon illumination with excitation light and which vary randomly from point to point on the surface, the fluorescence signatures having a relatively narrow emission spectrum, a relatively long fluorescence lifetime, and a fluorescence spectrum peak correlated to quantum dot diameter, further comprising a hardened liquid carrier in which the quantum dots are embedded, the hardened liquid carrier coating at least a portion of the substrate.

3. A data recording medium comprising quantum dots having random sizes arrayed in regions on a surface, the quantum dots having sizes, compositions and structures which at least partially determine the fluorescence properties of the quantum dots such that the pattern of quantum dots produces fluorescence signatures upon illumination with excitation light, the fluorescence signatures having a relatively narrow emission spectrum, a relatively long fluorescence lifetime, and a fluorescence spectrum peak correlated to quantum dot diameter, 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.

4. A data recording medium comprising quantum dots bound to selected regions on a surface, the quantum dots having sizes, compositions and structures which at least partially determine the fluorescence properties of the quantum dots such that the pattern of quantum dots produces fluorescence signatures upon illumination with excitation light, the fluorescence signatures having a relatively narrow emission spectrum, a relatively long fluorescence lifetime, and a fluorescence spectrum peak correlated to quantum dot diameter such that information is encoded in the distribution or selection of properties of the quantum dots in each region.

5. The data recording medium of claim 4 wherein the quantum dote are bound to selected regions on a surface by optically controlled chemical or physically controlled binding.

6. An anticounterfeit/security system comprising:

a document bearing quantum dots in a detectable arrangement, said quantum dots having sizes, compositions and structures which at least partially determine the fluorescence properties of the quantum dots such that the pattern of quantum dots produces fluorescence signatures upon illumination with excitation light, the fluorescence signatures having a relatively narrow emission spectrum, a relatively long fluorescence lifetime, and a fluorescence spectrum peak correlated to quantum dot diameter; and

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

7. An anticounterfeit/security system comprising:

means for applying quantum dots to a document in a detectable arrangement, the quantum dots having sizes, compositions and structures which at least partially determine the fluorescence properties of the quantum dots such that the pattern of quantum dots produces fluorescence signatures upon illumination with excitation light, the fluorescence signatures having a relatively narrow emission spectrum, a relatively long fluorescence lifetime, and a fluorescence spectrum peak correlated to quantum dot diameter;

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

means for comparing the arrangement to a reference.

8. A product having enhanced counterfeit resistance, comprising quantum dots deposited on a surface of the product, the quantum dots having sizes, compositions and structures which at least partially determine the fluorescence properties of the quantum dots such that the pattern of quantum dots produces fluorescence signatures upon illumination with excitation light, the fluorescence signatures having a relatively narrow emission spectrum, a relatively long fluorescence lifetime, and a fluorescence spectrum peak correlated to quantum dot diameter, the product further having an additional counterfeit-resistant feature located on the surface of the product.

9. 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;

quantum dots placed on the product identification side of the substrate in a detectable arrangement, the quantum dots having sizes, compositions and structures which at least partially determine the fluorescence properties of the quantum dots such that the pattern of quantum dots produces fluorescence signatures upon illumination with excitation light, the fluorescence signatures having a relatively narrow emission spectrum, a relatively long fluorescence lifetime, and a fluorescence spectrum peak correlated to quantum dot diameter;

means for detecting the properties or locations of the quantum dots based on the signature;

means for applying visible indicia on the product identification side, the indicia incorporating an encrypted message derived from the properties 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.