PHOSPHOR BASED AUTHENTICATION SYSTEM

• US 20100102250A1
• Filed: 10/22/2009
• Published: 04/29/2010
• Est. Priority Date: 10/23/2008
• Status: Active Grant

• Current Assignee: Intematix Corporation
• Original Assignee: Intematix Corporation
• Inventors: Li, Yi-Qun, Yang, Haitao
• Granted Patent: US 8,822,954 B2
• Time in Patent Office: Days
• US Class Current: 250/459.100
• CPC Class Codes: B32B 2255/00 Coating on the layer surface
• CPC Class Codes: B32B 2307/422 Luminescent, fluorescent, phosphorescent
• CPC Class Codes: B32B 2425/00 Cards, e.g. identity cards, credit cards
• CPC Class Codes: B32B 2519/00 Labels, badges
• CPC Class Codes: B32B 2554/00 Paper of special types, e.g. banknotes
• CPC Class Codes: B32B 27/18 characterised by the use of special additives
• CPC Class Codes: B32B 27/283 comprising polysiloxanes
• CPC Class Codes: B32B 27/308 comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/365 comprising polycarbonates
• CPC Class Codes: B32B 29/00 Layered products comprising a layer of paper or cardboard
• CPC Class Codes: B32B 5/24 one layer being a fibrous or filamentary layer
• CPC Class Codes: B42D 25/36 comprising special materials
• CPC Class Codes: B42D 25/387 absorbing or reflecting ultraviolet light
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/7734 Aluminates
• CPC Class Codes: C09K 11/77342 Silicates
• CPC Class Codes: C09K 11/77347 Silicon Nitrides or Silicon Oxynitrides
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: C09K 11/7787 Oxides C09K11/7785 takes precedence
• CPC Class Codes: C09K 11/77924 Aluminosilicates
• CPC Class Codes: G01N 2021/6419 : Excitation at two or more wavelengths
• CPC Class Codes: G01N 2021/6421 : Measuring at two or more wavelengths
• CPC Class Codes: G01N 21/64 : Fluorescence; Phosphorescence
• CPC Class Codes: G07D 7/12 : Visible light, infrared or ultraviolet radiation
• CPC Class Codes: G07D 7/1205 : Testing spectral properties
• CPC Class Codes: Y10T 428/24802 : Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• CPC Class Codes: Y10T 428/31678 : Of metal

Abstract

A phosphor (photo-luminescent) material based authentication system in which a blend (mixture) of at least two, preferably three or more, phosphor materials are used as a photo-luminescent security marking which is applied to or incorporated within an article/document to be authenticated. Preferably, the phosphor materials are each excitable by “eye safe” excitation radiation comprising visible light of wavelength 380 nm to 780 nm. Moreover, when excited the security marking preferably also emits visible light thereby minimizing any risk of damage to an operator'"'"'s eye in the event of accidental exposure to the excitation radiation and/or light generated by the photo-luminescent marking. The authenticity of the article/document can be authenticated by verification of the composition of the phosphor by exciting the marking and comparing one or more selected parameters of light emitted by the security marking with corresponding parameters of the characteristic emission spectrum of the authentic phosphor blend.

Claims

1. A method of authenticating a photo-luminescent security marking in which an authentic security marking comprises a blend of at least two phosphor materials that are excitable by excitation radiation of a selected wavelength that is within a wavelength range 380 to 780 nm and which when excited has a known emission characteristic, the method comprising:

a) irradiating the marking with excitation radiation of the selected wavelength,

b) measuring at least one selected parameter of light emitted by the marking, and

c) comparing the at least one measured parameter with a corresponding parameter of the known emission characteristic and verifying the authenticity of the marking if the parameters are within prescribed limits.

2. The method of claim 1, wherein the marking comprises at least one phosphor material which is only excitable by excitation radiation of wavelength within a first wavelength range and at least one phosphor material which is excitable by excitation radiation of wavelength within a second different wavelength range which overlaps and includes the first wavelength range, the method comprising:

a) irradiating the marking with excitation radiation of wavelength within the first wavelength range and measuring at least one selected parameter of light emitted by the marking,

b) irradiating the marking with excitation radiation of wavelength that is within the overlapping region of the first and second wavelength ranges and measuring at least one selected parameter of light emitted by the marking,

c) irradiating the marking with excitation radiation of wavelength within a part of the second wavelength range that does not overlap the first wavelength range and measuring at least one selected parameter of light emitted by the marking, and

d) comparing the at least one measured parameters measured with corresponding parameters of the known emission characteristic and verifying the authenticity of the marking if the parameters are within prescribed limits.

3. The method according to claim 1, wherein the at least one selected parameter is selected from the group consisting of:

intensity of selected wavelength region, ratio of intensities of selected wavelength regions, intensity of an emission peak, wavelength of an emission peak, rate of rise of an emission peak, rate of fall of an emission peak, ratio of emission peak intensities, ratio of emission peak wavelengths, intensity of an emission trough, wavelength of an emission trough, ratio of emission trough intensities, ratio of emission trough wavelengths, wavelength of a point of inflection, intensity of a point of inflection, ratio of point of inflection intensities, ratio of points of inflection wavelengths, number of emission peaks, number of emission troughs, number of points of inflection, shape of emission peak, and combinations thereof.

4. A method of authenticating a photo-luminescent security marking in which an authentic security marking comprises a blend of at least two phosphor materials in which at least one phosphor material is only excitable by excitation radiation of wavelength within a first wavelength range and at least one phosphor material is excitable by excitation radiation of wavelength within a second different wavelength range which overlaps and includes the first wavelength range, the method comprising:

a) irradiating the marking with excitation radiation of wavelength within the first wavelength range and measuring at least one selected parameter of light emitted by the marking,

b) irradiating the marking with excitation radiation of wavelength that is within the overlapping region of the first and second wavelength ranges and measuring at least one selected parameter of light emitted by the marking,

c) irradiating the marking with excitation radiation of wavelength within a part of the second wavelength range that does not overlap the first wavelength range and measuring at least one selected parameter of light emitted by the marking, and

d) comparing the selected parameters measured in a), b) and c) with corresponding parameters of the known emission characteristic and if the parameters are within prescribed limits verifying the authenticity of the marking.

5. The method according to claim 4, wherein the at least one selected parameter is selected from the group consisting of:

intensity of selected wavelength region, ratio of intensities of selected wavelength regions, intensity of an emission peak, wavelength of an emission peak, rate of rise of an emission peak, rate of fall of an emission peak, ratio of emission peak intensities, ratio of emission peak wavelengths, intensity of an emission trough, wavelength of an emission trough, ratio of emission trough intensities, ratio of emission trough wavelengths, wavelength of a point of inflection, intensity of a point of inflection, ratio of point of inflection intensities, ratio of points of inflection wavelengths, number of emission peaks, number of emission troughs, number of points of inflection, shape of emission peak, and combinations thereof.

6. An apparatus for authenticating a photo-luminescent security marking in which an authentic security marking comprises a blend of at least two phosphor materials that are excitable by excitation radiation of a selected wavelength that is within a wavelength range 380 to 780 nm and which when excited has a known emission characteristic, said apparatus comprising:

at least one excitation source operable to emit and irradiate the marking with excitation radiation of the selected wavelength;

a detector operable to measure at least one selected parameter of light emitted by the marking; and

processing means for comparing the at least one measured parameter with a corresponding parameter of the known emission characteristic and if the they are within prescribed limits verifying the authenticity of the marking.

7. The apparatus according to claim 6, and further comprising wavelength separating means for dividing the light emitted by the photo-luminescent security marking into selected wavelength regions and wherein the detector is operable to measure the intensity for each selected wavelength region.

8. The apparatus according to claim 7, wherein the wavelength separating means is selected from the group consisting of:

optical filter, gel filter, dichroic filter, a grating, an optical fiber grating, and a prism.

9. The apparatus according to claim 6, wherein the at least one selected parameter is selected from the group consisting of:

intensity of selected wavelength region, ratio of intensities of selected wavelength regions, intensity of an emission peak, wavelength of an emission peak, rate of rise of an emission peak, rate of fall of an emission peak, ratio of emission peak intensities, ratio of emission peak wavelengths, intensity of an emission trough, wavelength of an emission trough, ratio of emission trough intensities, ratio of emission trough wavelengths, wavelength of a point of inflection, intensity of a point of inflection, ratio of point of inflection intensities, ratio of points of inflection wavelengths, number of emission peaks, number of emission troughs, number of points of inflection, shape of emission peak, and combinations thereof.

12. The apparatus according to claim 6, wherein the at least one excitation source is operable to generate excitation radiation of wavelength range 400 to 450 nm.

13. The apparatus according to claim 6, wherein the at least one excitation source comprises a light emitting diode.

10. An apparatus for authenticating a photo-luminescent security marking in an authentic marking comprises at least one phosphor material which is only excitable by excitation radiation of wavelength within a first wavelength range and at least one phosphor material which is excitable by excitation radiation of wavelength within a second different wavelength range which overlaps and includes the first wavelength range the apparatus comprising:

i) a first independently operable excitation source operable to emit and irradiate the marking with excitation radiation of wavelength within the first wavelength range;

ii) a second independently operable excitation source operable to emit and irradiate the marking with excitation radiation of wavelength within the second wavelength range;

iii) a detector operable to measure at least one selected parameter of light emitted by the marking; and

iv) processing means for comparing the at least one selected parameter with a corresponding parameter of the known emission characteristic and if the they are within prescribed limits verifying the authenticity of the marking;

wherein the apparatus is operable

a) to irradiate the marking with excitation radiation of wavelength within the first wavelength range and to measure the at least one selected parameter of light emitted by the marking,

b) to irradiate the marking with excitation radiation of wavelength within the overlapping region of the first and second wavelength ranges and to measure the at least one selected parameter of light emitted by the marking,

c) to irradiate the marking with excitation radiation of wavelength within a part of the second wavelength range that does not overlap the first wavelength range and to measure the at least one selected parameter of light emitted by the marking and

d) compare values of the at least one selected parameter with corresponding parameters of the known emission characteristic and verifying the authenticity of the marking if the parameters are within prescribed limits.

11. The apparatus according to claim 10, wherein the at least one selected parameter is selected from the group consisting of:

intensity of selected wavelength region, ratio of intensities of selected wavelength regions, intensity of an emission peak, wavelength of an emission peak, rate of rise of an emission peak, rate of fall of an emission peak, ratio of emission peak intensities, ratio of emission peak wavelengths, intensity of an emission trough, wavelength of an emission trough, ratio of emission trough intensities, ratio of emission trough wavelengths, wavelength of a point of inflection, intensity of a point of inflection, ratio of point of inflection intensities, ratio of points of inflection wavelengths, number of emission peaks, number of emission troughs, number of points of inflection, shape of emission peak, and combinations thereof.

14. A photo-luminescent security marking comprising a blend of at least two phosphor materials in which each phosphor material is excitable by excitation radiation of a selected wavelength that is within a wavelength range 380 to 780 nm.

15. The marking according to claim 14, wherein the phosphor materials have the same host lattice structure.

16. The marking of claim 14, wherein each phosphor material is excitable by excitation radiation of a same wavelength range.

17. The marking of claim 14, wherein at least one phosphor material is only excitable by excitation radiation of a first wavelength range and at least one phosphor material is excitable by excitation radiation of a second wavelength range which overlaps and includes the first wavelength range.

18. The marking of claim 14, wherein the marking comprises a blend of at least three phosphor materials in which at least one phosphor material is excitable by excitation radiation of a first wavelength range, at least one phosphor material is excitable by excitation radiation of a second wavelength range which overlaps and includes the first wavelength range, and at least one phosphor material is excitable by excitation radiation of a third wavelength range which overlaps and includes the first and second wavelength ranges.

19. The marking according to claim 14, wherein the blend of at least two phosphor materials is selected from the group consisting of:

being incorporated with a binder material, being incorporated with an ink, being incorporated in a polymer material, being incorporated into a sheet of polymer material, being incorporated into a fiber of polymer material, being laminated between sheets of material in which at least one sheet is transmissive to the excitation radiation and light emitted by the phosphor materials, being applied to a surface of a metal foil, being applied to a surface of a metal foil and being incorporated as part of a bar code.

20. The marking according to claim 14, wherein the phosphor materials are excitable with excitation radiation of wavelength range 400 to 450 nm.

21. The marking according to claim 14, wherein each phosphor material has an average particle size selected from the group consisting of:

five microns or less, two microns or less, and one micron or less.

22. The marking according to claim 14, wherein the phosphor materials are selected from the group consisting of:

an aluminate, a silicate, a nitride, a sulfate, an oxy-nitride, an oxy-sulfate, and a garnet material.

23. A photo-luminescent security marking comprising a blend of at least two phosphor materials in which at least one phosphor material is only excitable by excitation radiation of a first wavelength range and at least one phosphor material is excitable by excitation radiation of a second wavelength range which overlaps and includes the first wavelength range.