Security mark, authentication method therefor, authentication device and manufacturing method as well as security mark ink and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-10449798-B2
Application number	US-201515120488-A
Country	US
Kind code	B2
Filing date	Jan 28, 2015
Priority date	Mar 3, 2014
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

A method for authenticating a security mark containing a photochromic compound can provide higher security performance. The method comprises a process of irradiating a security mark containing a photochromic compound with excitation light, a process of acquiring first security information on a time-dependent change in the absorption spectrum and/or reflection spectrum of the security mark after the irradiation with excitation light, and a process of checking the acquired first security information against previously acquired first security information on the security mark. In this method, the security mark preferably contains two or more photochromic compounds different from one another in color development and/or in quenching rate after the color development in a photochromic reaction.

First claim

What is claimed is:

1. A method for authenticating a security mark, comprising:
irradiating a security mark containing at least one first photochromic compound that is quenched within one second from the color development in a photochromic reaction, and at least one second photochromic compound that is quenched after ten or more seconds from the color development in a photochromic reaction, with excitation light, wherein the first and second photochromic compounds are spatially coincident and each exhibit a time-dependent change in an absorption wavelength and/or a reflection wavelength upon irradiation; and
acquiring first security information corresponding to the time-dependent change in the absorption wavelength and/or reflection wavelength of the security mark after the irradiation with excitation light, wherein the first security information comprises information on the time-dependent change in absorption wavelength or reflection wavelength of the first photochromic compound, wherein information on the time-dependent change in absorption wavelength or reflection wavelength solely of the first photochromic compound is used as the first security information and wherein the time-dependent change in the absorption wavelength or reflection wavelength of the second photochromic compound functions so as to hide the time-dependent change in absorption wavelength or reflection wavelength of the first photochromic compound from an observer.

2. The method for authenticating a security mark according to claim 1 , further comprising a process of checking the acquired first security information against security information previously acquired from the security mark, wherein the acquired first security information is checked against the previously acquired security information by comparing two dimensional absorption spectra of wavelength versus time including information on absorption wavelength, time, and absorbance or absorption spectra.

3. The method for authenticating a security mark according to claim 2 , wherein
the acquired first security information is calibrated based on the temperature at the time of acquiring the first security information and is then checked against the previously acquired security information on the security mark.

4. The method for authenticating a security mark according to one of claim 3 , wherein the security mark further contains a fluorescent substance, and the method further comprises a process of acquiring second security information on the spectrum of fluorescence emitted from the security mark and a process of checking the acquired second security information against the previously acquired security information.

5. A measuring device comprising:
an excitation light source for irradiating a security mark with excitation light comprising ultraviolet light and/or light having a wavelength of 400 to 600 nm, the security mark comprising at least one first photochromic compound that is quenched within one second from the color development in a photochromic reaction, and at least one second photochromic compound that is quenched after ten or more seconds from the color development in a photochromic reaction, wherein the first and second photochromic compounds are spatially coincident and each exhibit a time-dependent change in an absorption wavelength and/or a reflection wavelength upon irradiation by the excitation light source;
an observation light source for irradiating the security mark with visible and/or near-infrared light; and
a photodetector for detecting the visible and/or near-infrared light transmitted through or reflected by the security mark and generate therefrom an electrical signal output indicative of the time-dependent change in an absorption spectrum and/or a reflection spectrum of the first photochromic compound; and
an analyzer configured to receive the electrical signal output from the photodetector and to store the electrical signal output as first security information indicative of the time-dependent change in the absorption spectrum and/or reflection spectrum of the security mark after the irradiation with excitation light, wherein the analyzer processes information on the time-dependent change in absorption wavelength or reflection wavelength solely of the first photochromic compound as the first security information, and wherein the time-dependent change in the absorption wavelength or reflection wavelength of the second photochromic compound functions so as to hide the time-dependent change in absorption wavelength or reflection wavelength of the first photochromic compound from an observer.

6. The authentication device comprising the measuring device according to claim 5 , wherein the analyzer is further configured to compare for concordance the first security information against stored security information previously acquired from the security mark.

7. The authentication device according to claim 6 , wherein the analyzer stores calibration information that correlates a relationship between quenching rate of the photochromic compound and temperature of the photochromic compound, and wherein the analyzer calibrates the acquired first security information with the calibration information based on a temperature measured at the time of acquiring the first security information prior to comparing the first security information against the stored security information.

Assignees

• Japan Science & Tech Agency

Inventors

• Abe Jiro
• Kobayashi Yoichi

Classifications

• B42D25/387 Primary

  absorbing or reflecting ultraviolet light · CPC title

• C09D11/50

  Sympathetic, colour changing or similar inks · CPC title

• C09K9/02

  Organic tenebrescent materials · CPC title

• G01N21/64

  Fluorescence; Phosphorescence · CPC title

• B42D25/378

  Special inks · CPC title