Fluorescence notch coding and authentication

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DESCRIPTION

Fluorescence notch coding and authentication.

CROSS REFERENCE TO RELATED REQUESTS

This application claims priority to U.S. Patent Application Serial No. 12 / 316,037, filed December 8, 2008.

FIELD OF THE INVENTION

The present invention relates to security labeling, and more specifically to fluorescence and phosphorescent security labels that are optically encoded from the ultraviolet to far infrared spectral regions.

BACKGROUND

Imitation and counterfeiting have become major concerns in the modern market and economy. Advances in computer technology and printing techniques have increased the incidence of counterfeits, forged documents, and other fraudulent activities. Countless areas of today's high-tech society require and rely on the certification, authentication, and protection of highly valuable documents, papers, currency, or other materials.

While fraudulent activities, such as counterfeiting currency and forged signatures or handwriting are common, the methods for creating and refining counterfeit documents and forged documents are easier and more available with the advent of printing and printing. specialized computer processing. As early as 1991, the United States Treasury has continually added security protection features to currency denominations in an attempt to combat the use of counterfeit money. These protections have included watermarks, security threads embedded in the paper, micro-printing, color-changing ink, and the use of multi-colored banknotes.

Current methods of currency authentication involve visual observation under ultraviolet lamps of banknotes containing security threads and emitting materials such as inks and plates. Such security threads emit a different marking, color or code in response to exposure to ultraviolet light. In some circumstances, the emissive characteristics of different banknote denominations may emit different colors. In addition to the colors of the issue, a code number or other unique identifier can be detected with the naked eye when the note is exposed to ultraviolet light or excitation in any way.

Authentication of valuable documents or materials affects many facets of the economy. Public notaries use a raised seal to authenticate notarized documents; driver's licenses, passports and other photo identification contain holograms and microprints; and sports memorabilia and clothing retailers use holographic stamps and labels to demonstrate authenticity. Even fashion designers are now including authentication devices in their clothing to prevent knockoffs from passing off as designer goods.

A disadvantage of traditional security features is that they are visible and known to the world. If a counterfeiter is aware that there is a security thread on a banknote or a watermark on a document, duplicating the security feature is easier. Once a feature is known to the public, a counterfeiter can begin to develop specific strategies and solutions to overcome the security protections provided by the specific feature.

There is a need for covert security marking that is incorporated into currency, important and valuable documents, packaging, and other authentic materials to prevent unauthorized copying, imitation, counterfeiting, and other fraudulent use.

US 2006/0186348 describes a method of authenticating articles having a luminescent label. The label comprises two luminescent compounds and the emission band of one compound overlaps, at least partially, the absorption band of the second. Both compounds light up, and the relative intensity of the emissions gives a signature response that is used to authenticate articles.

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RESUME

Embodiments of the invention include systems and methods for authenticating documents and products using a combination of interacting absorb and issue signatures. Emission signatures in the form of fluorescent or phosphorescent coatings, inks, security threads, plates, particles, and substrates are used for the authentication and protection of items, such as documents, currency, and secondary packaging for tobacco, luxury goods, and pharmaceuticals. .

Absorption ink substrates and coatings can also be used to create unique optical signatures for authentication and encoding. Such signatures are created using a variety of materials including, for example, dyes, quantum dots, semiconductors, and nanostructures with plasmon-polariton resonances. Both emissive and absorption characteristics are used through the expansion of the electromagnetic spectrum from the ultraviolet spectrum to the infrared (IR) spectrum. Spectrally overlapping combinations of these characteristics are used to create codes that are concealed by the naked eye and signatures through a variety of application methods to print articles with such protective measures.

BRIEF DESCRIPTION OF THE DRAWINGS

These embodiments and other aspects of this invention will be readily apparent from the detailed description below and the accompanying drawings, which are intended to illustrate and not limit the invention, and in which:

Figure 1 is a cross section of a coating that is deposited on top of a dispersion and absorption substrate in accordance with one embodiment of the invention;

Figure 2 is a cross section of a monolayer or ink coating according to one embodiment of the invention;

Figure 3 is a cross section of a multilayer coating or ink according to one embodiment of the invention;

Figure 4 is an illustrative spectral emission graph of an enhanced security feature in accordance with one embodiment of the invention; and Figure 5 is an illustrative spectral emission graph of an enhanced security feature in accordance with one embodiment of the invention.

DETAILED DESCRIPTION

The invention will be more fully understood from the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein, however, it will be understood that the disclosed embodiments are only exemplary of the invention, which may be incorporated in various ways. Therefore, the specific functional details disclosed herein shall not be construed as limiting, but only as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the invention virtually in any appropriately detailed realization.

Embodiments of the invention include fluorescent and phosphorescent emissions that are combined with a narrow band absorption material (narrower than the excitable emission broad band) to create a new type of encryption and authentication signature. A broadband emitter material is combined with one or more narrowband absorbent materials that have a narrower absorption bandwidth than the emission line to create an emitter signature with one or more specific depressions or indentations at specific wavelengths. . A signature can be created with a series of depressions or specific characteristics at given wavelengths when more than one single absorber component is used below the emission line. Authentication codes or signatures can be created depending on spectral positions, shape relationships, and notch depth. Codes or signatures that use multiple emission materials combined to create a broad emission that overlaps the absorption lines are also possible.

The emission component can be an ink, security thread, or a coating that is deposited on top of a dispersion substrate that contains the substantially narrower absorption line. As shown schematically in Figure 1, a paper or plastic substrate 2 is embedded with particles of an absorbing material 4. A dye or ink coating 6 is embedded with one or more emitters. In one embodiment, the dye or ink coating 6 may include colored pigment particles to display a distinct color when viewed under ambient lighting conditions while also emitting a broad emission line with

ES 2 552 775 T3 specific absorption notches when subjected to optical or electrical excitation. The dye or ink coating 6 is deposited on the substrate 2 to form a security feature. When an optical or electrical excitation is applied to the security feature, the combination of the substrate absorbing materials and the coating emitting materials produces a unique spectral signature. The spectral signature is described in more detail below.

In another embodiment, the absorber material and the emitter material can be combined into one layer as a coating or ink. In such an embodiment, the use of scattering emitters and / or absorbers improves the absorptive depression identified in the spectral fingerprint. As shown schematically in FIG. 2, a single layer host material 14, such as a polymeric film, is embedded with emitter particles 16 and absorption particles 18. An optional pigment dye 20 may be employed to give the combined coating or coating-substrate a specific color. The pigment is chosen so that its absorption does not interfere with the absorption of the narrow line under the wider emission line. When an optical or electrical excitation is applied to the security feature, the combination of absorbing materials and the emitting materials of the polymeric film produces a unique spectral signature or code. According to one embodiment, the coating may be an ink for use in a variety of ink-based printing techniques, such as, without limitation, intaglio and lithographic printing.

Another embodiment, as shown in Figure 3, includes a multi-layer security feature in which two narrow-band absorption layers are sandwiched around a broadband emitter layer. A first layer 21, which may be a paper or polymer substrate, contains a plurality of one or more types of narrow band absorption particles 24. A core layer 23, such as a polymeric host or security thread, is provided in the first layer 21. The core layer includes a plurality of one or more types of broadband emitting particles 25. An upper layer 22 is disposed in the core layer, which includes a plurality of one or more types of narrow band absorbing particles 24.

The spectral emissions of a security feature can be used to identify and verify the authenticity of an item. A spectral emission can be illustrated by showing the intensity of the feature as a function of wavelength. A spectral emission from a typical security feature produces a signature 26 with few detectable features across the wavelength spectrum. According to one embodiment of the invention, the security feature is enhanced such that the excitation of the feature creates a distinct spectral pattern that can be analyzed to verify authenticity. If, after scanning the spectral emission of the article containing the characteristic, the expected emission signature does not match an expected signature, the article is a copycat or has been tampered with. If the signature matches the pattern or expected value, the document is authentic.

Figures 4 and 5 show examples of the fluorescent notch effect using a chromophore having broadband emitters and narrowband absorbers. Figure 4 represents a graph of the spectral emission intensity as a function of wavelength. A spectral emission from the chromophore produces a signature 28 that has unique and definable characteristics at given wavelengths. In the example shown in Figure 4, a drop in spectral emission occurs at a wavelength represented as 'A'. Figure 5 is yet another illustrative spectral fingerprint 30 of a security feature in accordance with one embodiment of the invention. The spectral imprint experiences a drastic drop in intensity due to absorption around the wavelength region represented as B. These absorption characteristics are undetectable to the human eye; however, the features are machine-readable requiring only the use of a spectrometer or other spectral detector.

In accordance with one embodiment of the invention, a machine-readable covert security feature is included for use in security threads on a banknote or other valuable document. A covert security feature can be embedded within the security thread or plate, without resulting in any obvious visible change in the excited signature of the threads when viewed using a standard ultraviolet lamp or source or other appropriate excitation source. The covert security feature, while undetectable to the naked eye, emits a specific and distinct spectral fingerprint. The incorporation of the new machine-readable covert feature is implemented without any change to the public perception of the excited issuing signature, making copying or duplication of the note more difficult.

According to one embodiment, the security feature appears as a series of sharp, chemically strong and stable spectral depressions within the existing much broader issue of the issue security feature as shown in Figure 5. When a banknote is subject to excitation, such as an ultraviolet lamp, the security feature within the bill appears as an existing one already in use. Without

ES 2 552 775 T3 However, when the note emission is analyzed with a spectrometer or other spectral resolution instrument, such as a spectrometer or detector and filter arrangement, the spectral emission of the security feature produces additional characteristics that cannot be see through the human eye under ultraviolet or other appropriate excitation.

Embedded covert signature authentication relies on the presence of all spectral features found in a signature. These characteristics include, without limitation, peaks or troughs at specific wavelengths, as well as relative relationships found throughout the spectral range. The precision of these wavelength characteristics can be defined as better than one part in a thousand and their ratios can be prescribed as better than 10% accuracy according to one embodiment. The sharpness of the absorption notches does not result in any obvious change in the color or appearance of the phosphorescent or fluorescent emission.

One embodiment of the invention includes a detector for authenticating and / or denominating currency. The detector includes a spectral resolving component or spectrometer that is configured to scan the spectral emission of the emission characteristic in a banknote under optical or electrical excitation. Alternatively, one embodiment of the invention includes a scanner, detector, or other device that can be incorporated into existing bill sorting or authentication machines with little or no adaptation or modernization. The security feature, according to one embodiment, can be read at high speeds at speeds exceeding the speed of forty notes per second using machines sold by Geisecke and Devireint, De La Rué International and other note processing machine manufacturers.

While the embodiments of the invention described herein show and describe spectral emissions with a spectral dip, one skilled in the art should recognize that any number of spectral features can be incorporated into a security feature without departing from the scope of the invention, which is limited only by the appended claims.

Furthermore, while the embodiments of the invention described herein discuss the excitation of an ultraviolet lamp, one skilled in the art should recognize that the disguised distinguishable characteristics of the security feature are not limited to the ultraviolet spectrum. For example, an ink or dye may contain spectral identification notches in other spectral ranges, such as the infrared range, that is, an ink, dye, or other characteristic that does not have any absorbing notches or notches in the ultraviolet or infrared range may have a spectral notch, or multiple notches in the infrared spectrum.

One embodiment of the invention includes excitation of the security feature, which can occur at more than one wavelength to reveal the different spectral bands that include distinguishable broad emissions with absorber notches. For example, a intaglio ink may have invisible and visible infrared emission characteristics that can be excited by one or more sources with one or both emission bands containing one or more absorber notches.

Although the invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various different changes, omissions, and / or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the scope of the invention. , which is limited only by the appended claims. Also, unless any use of the terms first, second, etc. is specifically stated. they do not represent any order or importance, but rather the terms first, second, etc. they are used to distinguish one element from another.