HK1210268B - Gas activated changes to ligth absorption and emission characteristics for security articles - Google Patents

Description

Gas-activated changes in the light absorption and emission properties of security articles

This application is a divisional application of the invention patent application with application number 201180012703.0, application date February 4, 2011, and invention name “Gas-activated changes in light absorption and emission properties of security articles”.

Related applications

This application claims priority to Provisional Application No. USSN 61/301,340, filed February 4, 2010, the disclosure of which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to security articles, and more particularly, to security articles having light absorption and emission properties that change upon exposure to a specific gaseous environment.

Background Art

Counterfeiting and forgery have become significant concerns in the modern economy and marketplace. Advances in computing and printing technology have increased the incidence of forged and counterfeited documents and other fraudulent activities. Countless areas of today's high-tech society require and rely on the authentication, authentication, and protection of high-value documents, official documents, currency, and other materials. Consequently, there is a need to incorporate security markings into currency, valuable documents, packaging, and other authentic materials to prevent unauthorized copying, forgery, counterfeiting, and other fraudulent use.

While fraudulent activities such as counterfeiting currency and forging signatures or handwriting are common, with the advent of sophisticated computer printing and processing, methods for creating and perfecting forged and counterfeit documents have become easier and more available. As early as 1991, the U.S. Treasury Department has continuously added security features to the face of its currency in an effort to combat the use of counterfeit bills. These safeguards have included watermarks, security threads embedded in the bills, microprinting, color-shifting inks, and the use of multi-colored bills.

Current methods for authenticating currency involve visual inspection, scanning under ultraviolet light, and incorporating security threads and emissive materials (e.g., ink and metal planchette) into banknotes. Such security threads emit a distinct marking, color, or code in response to exposure to ultraviolet light. In some cases, the emissive features of banknotes of different denominations may emit different colors. In addition to the emitted color, a code number or other unique identifier can be detected by the naked eye when the banknote is exposed to ultraviolet light or some form of excitation.

The authentication of security items (e.g., valuable documents or materials) impacts many aspects of the economy. Notaries use embossed stamps to authenticate notarized documents. Conversely, driver's licenses, passports, and other photo identification documents contain holograms and microprinting. Similarly, sports memorabilia and retail clothing retailers use holographic labels and stamps to prove authenticity. Even fashion designers are now incorporating authentication devices into their apparel to prevent counterfeit goods from being passed off as designer products.

For example, if a counterfeiter knows that there is a security thread in a banknote or a watermark in a document, the duplication of the security feature will become easier. Once a feature is known, a counterfeiter can start developing specific strategies and solutions to overcome the security protection provided by the specific feature.

Therefore, there is a need for security features that further reduce the likelihood of success for counterfeiters, even if they are aware of the security feature's existence.

Summary of the Invention

Embodiments of the present invention include security articles and methods and systems for authenticating security articles using multiple stimuli. According to one embodiment, an illustrative security feature includes activation of a phosphorescent or fluorescent material by the simultaneous presence of an electromagnetic radiation source and a specific gaseous environment. Thus, the radiation and gas serve as the first and second stimuli.

Security articles, such as those described herein, may require more than one stimulus (e.g., application of both light and a gaseous environment) to detect an authentication feature. Furthermore, such security articles may have security features that can be used publicly, covertly, or both (i.e., having a first response for public acquisition and a second response for covert use).

In one embodiment, the present invention relates to a security article. The security article may include a host material comprising a gas-activated security feature incorporated on or within the host material, wherein the gas-activated security feature is capable of emitting a spectral emission that changes upon exposure to a change in the gas environment of the gas-activated security feature. The host material may include a polymer. The host material may include a responsive portion and a non-responsive portion, wherein the gas-activated security feature may be incorporated on or within the responsive portion. The host material may include a reference security feature. In this case, the security feature and the reference security feature may emit different spectral emissions upon exposure to a change in the gas environment. And, in this case, the security feature and the reference security feature may emit equivalent spectral emissions upon exposure to a change in the gas environment. The gas-activated security material may include a material selected from the group consisting of fluorescent materials and phosphorescent materials. The gas-activated security feature may include a material selected from the group consisting of platinum(II) or palladium(II) porphyrins, platinum(II) or palladium(II) phthalocyanines or naphthalocyanines, terpyridine ruthenium(II) type complexes, terbium(III) mixed complexes, perylene dyes, hydroxybenzotrisulfonic acid, Reichardt's dyes, or combinations thereof. The gas-activated security feature may be incorporated on or within a carrier selected from the group consisting of inks, coatings, security threads, metal flakes, particles, holograms, and windowed areas.

In another embodiment, the present invention relates to a method for authenticating a security article. The method may include the steps of directing electromagnetic radiation at a security article comprising a gas-activated security feature; initiating a change in the gaseous environment of the security feature; and detecting a spectral emission of the security feature caused by the change in the gaseous environment. The step of initiating a change in the gaseous environment of the security feature may include removing gas from a first gaseous environment of the security feature or injecting gas into the first gaseous environment of the security feature to form a second gaseous environment of the security feature. The method may further include the step of comparing the spectral emission to an expected spectral emission to determine the authenticity of the security article. The method may further include the step of measuring a time response of the spectral emission. The method may further include the step of causing the spectral emission of the security feature to change from an original state to a gas-activated state. The method may further include the step of causing the spectral emission of the security feature to change from a gas-activated state to an original state.

In a further embodiment, the present invention relates to a detector system for authenticating a security article. The system includes an electromagnetic radiation source for directing electromagnetic radiation toward a security article comprising a gas-activated security feature; a gas environment source for initiating a change in the gas environment of the gas-activated security feature; and a detector for detecting spectral emissions from the gas-activated security feature resulting from the change in the gas environment. The electromagnetic radiation source may include wavelengths selected from the group consisting of infrared, visible light, and ultraviolet light. The gas environment source may provide a gas environment selected from the group consisting of an inert gas, water vapor, oxygen, carbon dioxide, chemical vapors, and human breath. The gas environment source may provide the gas environment by changing pressure or density or by applying a vacuum. The detector system may further include a gas environment modification device that removes gas from the gas environment or injects gas into the gas environment. The detector may be a spectrometer.

BRIEF DESCRIPTION OF THE DRAWINGS

These embodiments and other aspects of the present invention will be readily understood from the following detailed description and accompanying drawings, which are intended to illustrate rather than limit the present invention, and in which:

FIG1 is an illustrative embodiment of the present invention, showing a security article, an electromagnetic radiation source, a gas environment source, and a detector according to an embodiment of the present invention;

FIG2 is an illustrative graph of the spectral emissions of a security article according to an embodiment of the present invention;

FIG3 depicts the application of a gaseous environment to a security article according to an embodiment of the present invention; and

4 is an illustrative graph of the spectral emissions of a security article according to an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will be more fully understood from the following detailed description, which should be read in conjunction with the accompanying drawings. While a detailed description of the present invention is disclosed herein, it should be understood that the disclosed embodiments are merely exemplary of the present invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as a basis for the appended claims and as a representative basis for teaching one skilled in the art to employ the present invention in various ways in virtually any appropriately detailed embodiment.

Embodiments of the present invention include detecting fluorescent or phosphorescent emissions from a security article immediately after application of a specific gaseous environment. Specifically, application of the specific gas reveals a unique spectral pattern of the security article. In one embodiment, exposing the security article to a gaseous excitation (i.e., a specific gaseous environment) reveals a unique spectral emission by which the security article can be identified. According to embodiments of the present invention, the excitation of the security article may include visible ambient light or sunlight, or may include other optical or electromagnetic sources (e.g., ultraviolet or infrared sources).

The specific gaseous environment to which the security article may be exposed may include a responsive gas portion (which is capable of causing a change in absorption or excitation of the security feature) and a non-responsive gas portion (which does not cause such a response to the security feature). According to one embodiment of the present invention, the gas used for excitation may be a non-toxic, safe-to-exposure gas, such as an inert gas. According to other embodiments, the responsive gas portion may include water vapor, oxygen, carbon dioxide, or other chemical vapors, or human breath, which has a significantly reduced oxygen level compared to atmospheric air. Furthermore, the responsive gas portion may be the result of a change in the gaseous environment, such as a change in pressure or density (e.g., by creating a vacuum).

The security article may include one or more gas-sensitive materials, which may be disposed on or within a permeable host material (e.g., a polymeric material). The gas-sensitive material of the security article may be part of an ink, coating, security thread, metal flake, particle, hologram, or windowed area in a document or banknote. Depending on the gaseous environment, the luminescence spectrum of the security article may extend from ultraviolet to infrared. The excitation response of the gas-sensitive material is a result of the type of molecule used, the material's ability to bind to the host material, and the material's permeability to various gaseous components of the host material.

The absorption characteristics of gas-sensitive materials change with exposure to a specific gas environment. Changes in the absorption characteristics can result in changes in the visible color of the gas-sensitive material. Changes in the absorption characteristics can occur with or without the application of a light source or electromagnetic radiation source in addition to or in place of ambient light or sunlight. The light emission or color of the gas-sensitive material can change immediately after being excited by a stimulus from an electromagnetic source (e.g., ultraviolet, visible light, or infrared). Therefore, the authenticity of the security article can be determined by measuring the intensity of the spectral emission of the security feature or changes therein.

Furthermore, the gas-sensitive material may have the property that it changes color immediately upon stimulation from an electromagnetic source and has a rate of relaxation or return to its original color that is determined by the gas environment. In other words, the light emission of the gas-sensitive material may have a lifetime that depends on the particular gas environment or a change to the gas environment. The gas-activated security feature may be in: (1) an original state prior to application of the electromagnetic radiation and/or gas environment, (2) a gas-activated state simultaneously with or after application of the electromagnetic radiation and/or gas environment, or (3) recovered to the original state after application of the electromagnetic radiation and/or gas environment. The spectral emission may respond differently in the original, activated, and recovered states. Thus, the authenticity of the security article may also be determined by measuring the fluorescence lifetime (i.e., the temporal response of the spectral emission of the security feature, or its changes).

A detector system for analyzing security features in a security article may include an electromagnetic or optical excitation source, a device for spectral detection of absorption, color, or emission, and a gaseous environment modification device (e.g., a pump, nozzle, or ejector from a gas source). The gaseous environment modification device may draw air away from the security article or may blow a specific gaseous composition onto the security article. Alternatively, the gaseous environment modification device may include a straw-like device for blowing human breath onto the article. The detector system may also be capable of measuring the temporal response of the phase response of the spectral changes of the security article relative to periodic excitation of the light or gaseous environment, for example.

The spectral emissions of security articles can be used to identify and prove the authenticity of the article. Spectral emissions can be illustrated by displaying the intensity of a feature as a function of wavelength. Spectral emissions from a typical security feature produce a pattern with detectable characteristics or patterns across a spectrum of wavelengths. According to one embodiment of the present invention, the security feature is enhanced so that excitation of the feature produces a distinct spectral pattern that can be analyzed to prove authenticity. If, after scanning the spectral emissions of an article containing the feature, the expected emission pattern does not match the expected pattern, the article is likely counterfeit or may have been tampered with. If the pattern matches the expected pattern or value, the document is likely authentic.

FIG1 is an illustrative embodiment of the present invention, showing a security article, an electromagnetic radiation source, a gaseous environment source, and a detector. A security article 2 has a gas-activated security feature 4 incorporated into or on a host material 6. An electromagnetic radiation source 8 directs electromagnetic radiation toward the security article 2 having the gas-activated security feature 4. A gaseous environment source 10 initiates a change in the gaseous environment of the security feature 4. A detector 12 detects spectral emissions 14 resulting from the change in the gaseous environment and/or a simultaneous or subsequent exposure to electromagnetic radiation.

FIG2 shows spectral emission graphs of a security feature according to an embodiment of the present invention. Specifically, FIG2 depicts the intensity of the emission response from two excitation modalities—one optical, and one optical and gaseous—as a function of wavelength. A first spectral graph 16 is the result of optical excitation of the security feature; application of optical excitation produces higher emissions at certain wavelengths. A second spectral graph 18 results from excitation of the security feature by both optical and gaseous exposure. As shown in the graph of FIG2 , the spectral graph including excitation of a particular gaseous environment produces a significantly higher emission response. As part of the authentication process, a detector system (e.g., a spectrometer) can easily read the higher-intensity emissions of the security article.

Figure 3 depicts the application of optical and gas excitation to a phosphorescent material.When exposed to ultraviolet light or another type of electromagnetic radiation and a specific gas from an injector 19, the phosphorescent material 20 exhibits a detectable intensity 21 in the region λ where the light and gas are applied.

According to another embodiment of the present invention, a dual excitation material or coating can be included within an existing phosphorescent or fluorescent emitting security feature. FIG4 depicts a spectral graph (intensity versus wavelength) according to an embodiment of the present invention. A first spectral pattern 22 exhibits a unique pattern under optical and gas excitation. For example, the first spectral emission of a chromophore produces a pattern with a unique and definable characteristic at a given wavelength. In the example shown in FIG4 , dips (absorption) and peaks (emission) in the spectral emission occur at certain wavelengths. These dips and peaks are undetectable to the human eye; however, the characteristics are machine-readable, requiring only the use of a spectrometer or other detector system. A second spectral emission 24 exhibits the effect of the non-responsive portion of the gaseous environment, thereby highlighting an additional spectral pattern, namely, a measurable and quantifiable spectral shift obtained immediately after applying optical and gas excitation in the spectral pattern 22.

According to embodiments of the present invention, a machine-detectable security feature is included in a security article (e.g., a document, currency, or secondary packaging for goods such as cigarettes, luxury goods, or pharmaceuticals). The security feature can, for example, be embedded within a security thread, metal sheet, or as part of an ink, resulting in a visible change in the thread's excited pattern when viewed using a UV light source or lamp, or other suitable excitation source. However, the application of a specific gaseous environment can result in a color change and a measurable and quantifiable spectral shift in the security feature, as illustrated in FIG4 . While undetectable to the naked eye in certain circumstances, the security feature emits a specific and distinct color and a unique spectral fingerprint under optical and gaseous excitation in a specific gaseous environment. The choice of different phosphors results in different color and spectral emissions. The incorporation of a machine-readable, covert feature can be implemented without any change to the public perception of the excited emission pattern, thereby making forgery or duplication of documents more difficult.

There are various classes of compounds that can exhibit an increase or decrease in electromagnetic radiation emission, a change in intensity, fluorescence, or other detectable changes upon exposure to a particular gaseous environment. By way of example and not limitation, in one embodiment, the following classes of compounds can be gas-activated in an oxygen environment or other gaseous environment: platinum(II) or palladium(II) porphyrins; platinum(II) or palladium(II) phthalocyanines or naphthalocyanines; terpyridine ruthenium(II) type complexes; terbium(III) mixed complexes, and perylene dyes. By way of example and not limitation, in another embodiment, the following classes of compounds can be gas-activated in a carbon dioxide environment or other gaseous environment: hydroxypyridine trisulfonic acid ("HPTS") in a wet polymer or gel medium. By way of example and not limitation, in a further embodiment, the following classes of compounds can be gas-activated in an aqueous environment or other type of environment: terpyridine ruthenium(II) type complexes; perylene dyes; and Richard dyes. In one embodiment, water-sensitive absorbers can be used to selectively block absorption or emission from fluorescent dyes or other types of dyes that are unaffected by water.

While the embodiments of the invention disclosed herein describe the detection of emission features under excitation by light and gas sources, those skilled in the art will recognize that the absorption properties of gas-sensitive materials can be advantageously utilized as security features. For example, according to another embodiment of the invention, the security feature may include a phosphorescent material having an absorptive spectral response at certain wavelengths under optical excitation. Applying gas excitation to the material results in a recovery of the material's emission intensity.

While the embodiments of the invention disclosed herein are described based on the detection of a specific response to an excitation source, those skilled in the art will recognize that additional parameters, such as the temporal decay of the emission, the spectral profile of the subject, and the response time and emission changes under gas excitation, may be incorporated without departing from the scope of the invention.

The aspects, embodiments, features and examples of the present invention should be considered in all respects as illustrative and not intended to limit the present invention, the scope of which is defined solely by the appended claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

The use of headings and sections in the application is not intended to limit the invention; each section may apply to any aspect, embodiment, or feature of the invention.

Throughout this application, where compositions are described as having, including, or comprising particular ingredients, or where processes are described as having, including, or comprising particular process steps, it is contemplated that the compositions taught herein also substantially contain or comprise the recited ingredients, and that the processes taught herein also substantially contain or comprise the recited process steps.

In this application, when an element or component is referred to as being included in and/or selected from a recited list of elements or components, it should be understood that the element or component may be any one of the recited elements or components and may be selected from a group consisting of two or more of the recited elements or components. Furthermore, it should be understood that the elements and/or features of the compositions, apparatuses, or methods described herein may be combined in various ways without departing from the spirit and scope of the present teachings (whether explicitly or implicitly included therein).

The use of the terms "including," "comprising," or "having" should generally be construed as open-ended and without limitation unless expressly stated otherwise.

The use of the singular herein includes the plural (and vice versa) unless expressly stated otherwise. Furthermore, the use of the singular forms "a," "an," and "the" includes the plural unless the context clearly indicates otherwise. Furthermore, where the term "about" precedes a numerical value, the present teachings also include the specific numerical value itself, unless expressly stated otherwise. As used herein, the term "about" refers to a variation of ±10% from the nominal value.

It should be understood that the order of steps or the order in which certain actions are performed is not critical, as long as the present teachings remain operable. In addition, two or more steps or actions may be performed simultaneously.

Where a range or list of values is provided, each intervening value between the upper and lower limits of the range or list of values is individually contemplated and included in the present invention, just as if each value were expressly recited herein. In addition, smaller ranges between and including the upper and lower limits of a given range are contemplated and included in the present invention. The listing of exemplary values or ranges is not a disclaimer of other values or ranges between and including the upper and lower limits of a given range.

Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and/or additions may be made, and that substantial equivalents may be substituted for its elements without departing from the spirit and scope of the present invention. Furthermore, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the specific embodiments disclosed for practicing the present invention, but that the present invention will include all embodiments falling within the scope of the appended claims. Furthermore, unless expressly stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather, the terms first, second, etc. are used to distinguish one element from another.

Claims (13)

1. A safety article comprising: A host material having responsive and non-responsive portions, the host material including gas-activated safety features incorporated on or within the responsive portions of the host material. The gas-activated safety feature is capable of emitting a first spectral emission, which immediately changes to a second spectral emission upon exposure to a change in the gas environment of the gas-activated safety feature. 2. The safety article of claim 1, wherein the body material comprises a polymer. 3. The safety article of claim 1, wherein the gas-activated safety feature is further incorporated into an existing safety feature in the article. 4. The safety article of claim 3, wherein the gas-activated safety feature and the existing safety feature immediately emit different spectral emissions upon exposure to the change in the gas environment. 5. The safety article of claim 3, wherein the gas-activated safety feature and the existing safety feature immediately emit equivalent spectral emissions upon exposure to the change in the gas environment. 6. The safety article of claim 1, wherein the gas-activated safety feature comprises a material selected from the group consisting of fluorescent materials and phosphorescent materials. 7. The safety article according to claim 1, wherein the gas-activated safety feature comprises a material selected from the group consisting of platinum(II) or palladium(II) porphyrin, platinum(II) or palladium(II) phthalocyanine or naphthalenephthalocyanine, terpyridine ruthenium(II) type complex, terbium(III) mixed complex, perylene dyes, hydroxytrisulfonic acid, Richard dyes, or combinations thereof. 8. A method for identifying a safe article, comprising the following steps: Electromagnetic radiation is directed to a safety article containing a gas-activated safety feature, the safety article having a responsive portion and a non-responsive portion; Changes in the gaseous environment that initiate the safety features; and The change in the spectral emission of the safety feature caused by the change in the gaseous environment is detected from the first spectral emission to the second spectral emission. 9. The method of claim 8, wherein the step of initiating a change in the gas environment of the safety feature comprises removing gas from a first gas environment of the safety feature or injecting gas into the first gas environment of the safety feature to form a second gas environment of the safety feature. 10. The method of claim 8, further comprising the step of comparing the differential spectral emission with the desired spectral emission to determine the authenticity of the security article. 11. The method of claim 8, further comprising the step of measuring the time response of the spectral emission. 12. The method of claim 8, further comprising the step of changing the spectral emission of the safety feature from a pristine state to a gas-activated state. 13. The method of claim 8, further comprising the step of changing the spectral emission of the safety feature from a gas-activated state to its original state.