Patent Publication Number: US-8118231-B2

Title: Security structure and article incorporating such a structure

Description:
BACKGROUND 
     The subject of the present invention is in particular a security structure and an article incorporating such a structure. 
     Patent EP-B1-0 319 157 teaches a document of value, such as a banknote, incorporating a demetallized security thread, it being possible for the thread to contain a fluorescent material. 
     SUMMARY 
     There is a need to further improve the protection of security documents and/or documents of value from falsification. 
     The aim of the present invention is in particular to meet this need. 
     The subject of the invention is, according to one of its aspects, a security structure intended to be incorporated or fastened, at least partially, in or on an article, for example a security document and/or a document of value, the structure comprising:
         at least one first fluorescent zone capable of emitting by fluorescence, under a predefined illumination condition, visible light of a first color; and   at least one second fluorescent zone capable of emitting by fluorescence, under the predefined illumination condition, visible light of a second color that differs from the first, the first and second fluorescent zones being observable from the respective opposed faces of the structure.       

     Thus, under the predefined illumination conditions, the color of the structure may vary from one face to the other, the structure for example appearing at least partially blue on one face and at least partially yellow on the other. Authentication and/or identification of an article comprising such a structure may thus involve two observation steps from the two respectively opposed faces of the article. This increases the level of protection of the article against falsification. 
     Furthermore, the invention makes it possible, owing to the presence of fluorescent zones of different colors, to create novel optical effects. 
     The predefined illumination condition may correspond to ultraviolet illumination, in particular with a wavelength close to the visible, for example about 365 nm. As a variant, the predefined illumination condition corresponds to infrared illumination. 
     In one exemplary embodiment of the invention, at least one of the first and second fluorescent zones, in particular both, are substantially colorless in white light and/or at least partially nonopaque, at least under the predefined illumination condition. 
     Advantageously, the first and second fluorescent zones are superposed at least partially so that, under the predefined illumination condition, the superposition of the two fluorescent zones appears, in transmitted light, as a third color that differs from the first and second colors. 
     Thus, authentication and/or identification of an article or document incorporating such a structure may include, in addition to two observation steps under the predefined illumination condition, so as to observe, in reflection, the first and second colors, at least one observation step in transmitted light in order to observe the third color. 
     Advantageously, the first and second fluorescent zones have absorption spectra chosen so that, under the predefined illumination condition, their superposition appears, in transmitted light, as a third or fourth color that differ from the first and second colors, depending on the order of the fluorescent zones through which the incident light passes. 
     The difference ΔE between the third and fourth colors, in the 1976 CIE calorimetric space (L*C*h), may be at least 2, in particular at least 5, thereby making this difference readily observable. 
     Authentication and/or identification of an article or document may thus involve detecting four different colors. This further enhances the security. 
     For example, under UV illumination, the first fluorescent zone appears yellow and the second fluorescent zone appears blue in reflection, while when observed in transmitted light the structure has a violet color when it is observed from a first face and appears substantially white when it is observed from a second face, opposite the first. 
     The colors and their number may differ from those described above. 
     As a variant, the first and second fluorescent zones have absorption spectra chosen so that, under the predefined illumination condition, the superposition of the two fluorescent zones appears, in transmitted light, to have substantially the same color irrespective of the side of observation. 
     In one exemplary embodiment of the invention, the structure comprises at least one third fluorescent zone observable on the same face as the first fluorescent zone, having a color that differs from the first fluorescent zone under the predefined illumination condition. 
     Advantageously, the structure comprises:
         at least one third fluorescent zone appearing in said second color under the predefined illumination condition, the first and third zones being observable from a first face of the structure; and   at least one fourth fluorescent zone appearing in said first color under the predefined illumination condition, the second and fourth zones being observable from a second face of the structure, on the opposite side from the first,
 
each fluorescent zone on one face being at least partially, preferably substantially exactly, superposed with a fluorescent zone of different color on the other face.
       

     When the order of superposition of the fluorescent zones is not without effect on the result produced when observing the structure in transmitted light, what may be observed on each face of the structure, in transmitted light, under the predefined illumination conditions, is an alternation of fluorescent zones appearing in the third and fourth colors respectively. Thus, irrespective of from which side the face is observed, the structure has overall the same appearance under the predefined illumination condition. This may facilitate authentication and/or identification. 
     Preferably, the third fluorescent zone, or the fourth fluorescent zone, is adjacent the first zone, or adjacent the second zone respectively, these zones preferably being substantially exactly superposed. Advantageously, the structure is nonopaque in a joining region between the first and third fluorescent zones, or second and fourth fluorescent zones, respectively. 
     Such a structure offers enhanced security against falsification insofar as a defect in the arrangement of the fluorescent zones can be detected relatively easily. This is because when the fluorescent zones on the opposed faces of the structure are exactly superposed, when the structure is observed by holding it up to the light, under the predefined illumination conditions, only one or two colors are revealed. However, when fluorescent zones on the opposed faces are not superposed exactly and overlap onto neighboring fluorescent zones, other colors are revealed. 
     In one exemplary embodiment of the invention, the structure has at least one entirely fluorescent face, in particular two opposed entirely fluorescent faces. As a variant, the structure has at least one entirely fluorescent face, in particular two opposed entirely fluorescent faces, comprising for example fluorescent zones alternating with nonfluorescent zones. 
     In one exemplary embodiment of the invention, the structure comprises a support which is at least partially, in particular entirely, transparent or translucent and bears the fluorescent zones. The support may be flexible, in particular being made of a plastic, for example a polyester. 
     At least one of the fluorescent zones may be formed by depositing a fluorescent composition on one face of the support. 
     Preferably, the structure, for example the support, comprises at least first and second adjacent portions, the first portion having a greater aptitude to opposing the passage of light, under a given illumination, than that of the second portion. 
     The first portion may be substantially opaque and/or reflective, at least under the predefined illumination condition, for example under UV illumination and/or under ambient illumination. 
     The second portion may be substantially transparent and/or translucent at least under the predefined illumination condition, for example under UV illumination and/or at least under ambient illumination. 
     Preferably, the second aforementioned portion is at least partially superposed with at least one fluorescent zone or, as the case may be, with the superposition of two fluorescent zones so that, under the predefined illumination condition, in transmitted light, the second portion appears with a color corresponding to the fluorescent zone or to the superposition of the fluorescent zones. 
     In one exemplary embodiment of the invention, the second portion has a shape chosen so as to define a pattern, which appears, in transmitted light, lighter than adjacent regions of the structure. 
     The second portion may, where appropriate, be entirely surrounded by the first. 
     In another exemplary embodiment of the invention, the first portion has a form chosen so as to define a pattern, which appears, in transmitted light, darker than adjacent regions of the structure. 
     The first portion may, where appropriate, be entirely surrounded by the second. 
     The pattern may be chosen from one of the following elements: a letter, a drawing, a symbol, a logo, this list not being exhaustive. 
     In one exemplary embodiment of the invention, the aforementioned first portion is formed by a metal layer, in particular a metal coating, and the afore-mentioned second portion is formed by demetallizing this layer. 
     As a variant, the structure includes printing, in negative or positive, with an ink, the first portion having the ink and the second portion having no ink. 
     Advantageously, the aforementioned second portion and the fluorescent zone at least partially covering it are nonopaque in white light so as to allow, in ambient light, when the article is held up to the light, to see patterns present on the structure, thus offering additional security. 
     The invention thus makes it possible to have, for a document, the following levels of security:
         first level: observation in ambient light, when the document is held up to the light, of the one or more second portions, with recognition of the corresponding one or more patterns;   second level: observation of fluorescent zones, by reflection, under the predefined illumination condition; and   third level: observation, in transmitted light, under the predefined illumination condition, of the one or more second portions, with recognition of the one or more patterns and, where appropriate, of colors formed by the superposition of the fluorescent zones.       

     Advantageously, the second portion extends over a joining region between adjacent aforementioned first and third fluorescent zones, or adjacent second and fourth fluorescent zones, respectively. 
     The first aforementioned opaque and/or reflective portion may optionally include a composition that may or may not contain fluorescent dyes or pigments. 
     In one exemplary embodiment of the invention, the aforementioned first and second portions form a plurality of patterns or groups of patterns that repeat, in a regular or random fashion, along a predetermined direction. 
     In order for the protection to be further enhanced, the structure may include one of the following elements:
         an electronic chip;   a holographic or diffractive element;   a magnetic or crystalline coating;   liquid crystals;   printing with a varnish;   a marker, in particular a biological, mineral or synthetic marker;   a luminescent ink or substance;   a thermochromic and/or piezochromic pigment.       

     The structure may take various forms, for example in the form of a strip, and constitute for example a security thread. The structure may have for example a width of at least 0.7 mm but preferably less than 60 mm, in particular between 1 mm and 40 mm. 
     In an exemplary embodiment of the invention, the structure is designed to be entirely incorporated into or onto the security article and/or article of value. 
     As a variant, the structure comprises a support forming a carrier strip designed to be separated from at least one fluorescent layer after the structure has been applied on an article, in particular a security document and/or a document of value, it being possible for the structure to include, where appropriate, between the support and the fluorescent layer, at least one release layer. The structure may constitute for example a security patch. 
     The subject of the invention is also, according to another of its aspects, an article, for example a security document and/or a document of value, comprising a security structure as mentioned above. 
     The structure may be at least partially embedded in a layer of the article and comprise, for example, alternately zones embedded in a layer of the article and exposed portions. As a variant, the structure may be flush with one face of the article or may be entirely embedded in it. 
     The article may include, in contact with the structure, at least one fibrous layer containing, for example, paper fibers, in particular cellulose fibers, and/or synthetic fibers. 
     As a variant, the article may include, in contact with the structure, at least one nonfibrous layer, for example made of plastic. 
     In one exemplary embodiment of the invention, the security structure extends from a first edge of the article to a second edge, opposite the first. 
     The article may be intended to receive printing, especially to form a document. 
     The article may be intended to constitute one of the following elements: a banknote; a security paper; a passport sheet or cover; a visa; a coupon; a document of value other than a banknote, for example a check or a credit card; a protective and/or authenticating label; a traceability label; an optical disc; a ticket. 
     Preferably, the article includes, in line with the fluorescent zones, a region that is sufficiently transparent and/or translucent for at least one portion of the fluorescent zones to be visible through said region when the article is observed by holding it up to the light. 
     The aforementioned region may for example correspond to an aperture in the article or to a layer of at least one transparent and/or translucent material. 
     Yet another subject of the invention, according to another of its aspects, is a method of manufacturing an article, which includes the following steps:
         provision of a structure as mentioned above,   at least partial incorporation or transfer of the structure into or onto the article.       

     When the article includes a fibrous layer, the method may include the following steps:
         formation of the fibrous layer by depositing fibers on a surface immersed in a dispersion of fibrous material; and   contacting of the structure with the fibrous layer being formed.       

     As a variant, the method may include the following steps:
         contacting of one face of an article with a support for at least one fluorescent layer;   transfer of the fluorescent layer; and   after transfer, separation of the support from the fluorescent layer.       

     Yet another subject of the invention, according to another of its aspects, is a method of authenticating and/or identifying an article, comprising a structure as defined above, the method including the following steps:
         the article is exposed to the predefined illumination condition; and   the authenticity and/or identity of the article is checked on the basis of the color or colors revealed by the fluorescent zones.       

     When the first and second fluorescent zones are non-opaque, observable from opposite sides of the structure and at least partially superposed, the method advantageously comprises the following steps:
         observation of the first fluorescent zone in reflected light, under the predefined illumination condition;   observation of the second fluorescent zone in reflected light, under the predefined illumination condition;   observation of the structure in transmitted light, under the predefined illumination condition; and   verification of the authenticity and/or identity of the article on the basis of the colors observed in the above steps.       

     When the first and second fluorescent zones have absorption spectra chosen so that, under the predefined illumination condition, light passing in succession through the two fluorescent zones has third and fourth colors, which differ from the first and second colors, depending on the order of the fluorescent zones through which the incident light passes, the method advantageously comprises the following steps:
         observation of the structure in transmitted light, under the predefined illumination condition, from a first face of the article;   observation of the structure in transmitted light, under the predefined illumination condition, from a second face of the article, opposite the first; and   verification of the authenticity and/or identity of the article on the basis of the colors observed in the above steps.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood on reading the following detailed description of nonlimiting exemplary embodiments of the invention and on examining the appended drawing in which: 
         FIG. 1  shows, schematically and partially, an example of an article produced in accordance with the invention; 
         FIGS. 2 and 3  show, schematically and partially, in cross section, the structure incorporated into the article of  FIG. 1 , in accordance with two exemplary embodiments of the invention; 
         FIGS. 4 to 13  show, schematically and partially, other exemplary embodiments of the structure; 
         FIGS. 14 to 16  show, schematically and partially, in cross section, articles respectively conforming to various exemplary embodiments of the invention; 
         FIG. 17  illustrates schematically one step of a method of manufacturing the article of  FIG. 1 ; 
         FIG. 18  shows, schematically and partially, in cross section, a security structure according to another exemplary embodiment of the invention; 
         FIG. 19  shows, schematically and partially, in cross section, an article incorporating the structure of  FIG. 18 ; and 
         FIG. 20  illustrates, schematically, one step of the method of manufacturing the article of  FIG. 19 , in accordance with an exemplary embodiment of the invention. 
     
    
    
     In the drawing, for the sake of clarity, the relative proportions of the various elements shown have not always been respected, the views being schematic. 
     DETAILED DESCRIPTION 
       FIG. 1  shows an article  1 , for example a banknote, which includes a fibrous layer  2  in which a security structure  3  according to the invention is incorporated. 
     The article  1  may also constitute a security paper, a passport sheet or cover, a visa, a coupon, a document of value other than a banknote, for example a check or a credit card, a protective and/or authenticating label, a traceability label or an optical disk. 
     The article  1  may, where appropriate, consist of the structure itself, for example in the case of a plastic banknote. 
     The structure  3 , in the example considered, takes the form of a band of longitudinal axis X, with a width less than that of the article  1 , being for example about 15 mm or less. 
     The structure  3  may be completely embedded in the article  1 , as may be seen in  FIG. 14 . As a variant, as illustrated in  FIG. 15 , the structure  3  is flush with one face  4  of the article. Again as a variant, as illustrated in  FIG. 16 , the structure  3  is partially embedded in the fibrous layer  2  so as to have alternately embedded portions and exposed portions. For this purpose, the fibrous layer  2  may include recesses  5 , allowing portions of the structure  3  to be exposed. Where appropriate, the fibrous layer  2  may include protrusions  7 , shown in dotted lines in  FIG. 16 , located between the recesses  5 . 
     The article  1  may have, where appropriate, apertures that facilitate observation in transmitted light. 
     The structure  3  includes for example a support  10  made of a transparent plastic, especially a polyester, as illustrated in  FIG. 2 . 
     The structure  3  includes a substantially opaque and/or reflective first portion  13  surrounding substantially transparent second portions  12 . 
     In the example considered, the second portions  12  form groups of patterns  11 , such as text, as illustrated in  FIGS. 6 and 7 , which is repeated along the longitudinal direction of the structure  3 . 
     As a variant, the patterns may represent a drawing, a symbol or a logo. 
     The first portion  13  may be formed by a metal coating and the portions  12  by demetallizing this coating. 
     As a variant, the first portion  13  is formed by depositing an ink by printing in negative, and the second portions  12  correspond to the zones containing no ink. 
     The portions  12  and  13  may be produced on only one face of the support  10 , as illustrated in  FIG. 2  or, as a variant, on both opposed faces of the support  10 , as illustrated in  FIG. 3 . 
     The support  10  with the portions  13  is covered on at least one of its faces with at least one fluorescent composition. 
     In the example shown in  FIGS. 2 and 3 , the support  10  and the portions  13  are covered with fluorescent compositions  15  and  16  which appear, in fluorescence, in a first color C 1  and a second color C 2  respectively, under a predefined illumination condition, for example under UV illumination, in particular having a wavelength close to 365 nm. 
     Furthermore, the fluorescent compositions  15  and  16  have absorption spectra chosen so that, under the predefined illumination condition, their superposition appears in a third color C 3  or a fourth color C 4 , which differ from the first and second colors C 1  and C 2 , depending on the order of the fluorescent compositions through which the incident light passes. 
     The fluorescent compositions  15  and  16  are for example those sold by Honeywell. 
     The compositions  15  and  16  are nonopaque, so that the second portions  12  can be observed in daylight, when the article is held up to the light. 
     Various steps for authenticating and/or identifying the article  1  will now be described with reference to  FIGS. 4 to 7 . 
     When the article  1  is observed from the face  18  of the structure  3 , under the predefined illumination condition, in reflection, the structure  3  appears with the first color C 1 , as illustrated in  FIG. 4 . 
     When observing the article  1  from the opposite face  19 , again under the predefined illumination condition, in reflection, the structure  3  appears with the second color C 2 , as illustrated in  FIG. 5 . 
     Under the predefined illumination condition, when the article  1  is observed in transmitted light from the face  18 , the portions  12  appear with the third color C 3 , as may be seen in  FIG. 6 , while observation from the other face  19 , when the article is held up to the light, reveals the portions  12  with the fourth color C 4 , as illustrated in  FIG. 7 . 
     Thus, the article  1  may be authenticated and/or identified by observing four different colors. 
     In the example that has just been described, the structure  3  has, on each face  18  or  19 , a single color under the predefined illumination condition. 
     It would not be outside the scope of the present invention for the security structure to include fluorescent zones of different colors on each face. 
       FIGS. 8 and 9  show a structure  3 ′ according to the invention, having on opposed faces  20  and  23  an alternation of adjacent fluorescent zones  21  and  22 , and  24  and  25  respectively. The zones  21  and  25 , and the zones  22  and  24  respectively, are capable of emitting, by fluorescence, light of a first color C 1 , and of a second color C 2 , respectively, under the predefined illumination condition. 
     In the example considered, the fluorescent zones  21 ,  22 ,  24  and  25  are of rectangular shape. Of course, these fluorescent zones may have any other shape, for example trapezoidal. 
     Each respective zone  21 ,  22  is superposed exactly with a respective zone  24 ,  25  on the other face. In the example considered, each pair of fluorescent zones  21 ,  24  and  22 ,  25  entirely covers a group of portions  12 . 
     The color C 3  or C 4  produced by observing, in transmitted light, the fluorescent zones depends on the order in which the light passes through them. 
     Authentication and/or identification of an article having the structure  3 ′ may thus comprise the following steps:
         the structure  3 ′ is observed from the respective face  20 ,  23 , under the predefined illumination condition, in reflection, so as to detect the alternation of colors C 1  and C 2  on the respective face  20 ,  23 , as illustrated in  FIGS. 8 and 9 ; and   the respective face  20 ,  23  of the structure  3 ′ is observed under the predefined illumination condition, by holding the article up to the light, as illustrated in  FIGS. 10 and 11 , so as to detect the succession of groups of portions  12  having alternately colors C 3  and C 4 .       

     To enhance the security of the structure  3 ′, it is possible to provide, as illustrated in  FIG. 12 , transparent and/or translucent intermediate portions  27  between two groups of portions  12 , these intermediate portions  27  revealing, at least when the article is held up to the light, the join between two respective adjacent fluorescent zones  21  and  22 ,  24  and  25 . 
     Thus, under the predefined illumination condition, when the structure  3 ′ is observed by holding it up to the light, for example from the face  20 , the intermediate portions  27  each have the colors C 3  and C 4 . 
     It may be seen that, if the fluorescent zones  21 ,  22  and  24 ,  25  do not coincide exactly, since for example one of the fluorescent zones  22  is wider than the facing zone  25 , the intermediate portion  27  would not only have the colors C 3  and C 4 , but also a portion with the color C 2  corresponding to the superposition of the zone  22  with the neighboring zone  24 . This means that the structure  3 ′ has been falsified. 
     The intermediate portions  27  may form patterns  28 , for example drawings, revealing the join between two respective adjacent fluorescent zones  21  and  22 ,  24  and  25 , as illustrated in  FIG. 13 . 
       FIG. 17  shows, schematically and partially, a cylinder mold paper machine. 
     This machine comprises a tank  40  containing a suspension  41  of fibers, for example cellulose fibers for example onto the surface of the latter, as illustrated in  FIG. 19 . 
     The assembly  60  may in particular be transferred hot onto the fibrous layer  2 , as illustrated in  FIG. 20 . 
     The layer  2  and the structure  50  are driven in the same direction by means of a machine comprising first  61  and second  62  rotating rolls. After having passed through these rolls, the support  51  and the release layer  52  are separated from the assembly  60 , which remains attached on the layer  2 . 
     In the example considered, the layer  2  has a relatively small thickness, making it possible to observe, when the article is held up to the light, the assembly  60  from the opposite face of the layer  2  from the assembly  60 . 
     As a variant, the layer  2  may for example be made in a transparent material, for example a transparent plastic. 
     Of course, the invention is not limited to the exemplary embodiments described above. 
     The structure according to the invention may be produced other than in the form of a band, for example in the form of a patch. The structure according to the invention may include compositions exhibiting fluorescence other than in UV, for example in infrared. 
     The structures  3  and  3 ′ and the foil  50  may include, if so desired, one of the following elements:
         an electronic chip;   a holographic or diffractive element;   a magnetic or crystalline coating;   liquid crystals;   printing with a varnish;   a marker, in particular a biological, mineral or synthetic marker;   a luminescent ink or substance;   a thermochromic and/or piezochromic pigment.       

     Throughout the description, including the claims, the expression “comprising one” or “including one” must be understood to be synonymous with the expression “comprising at least one” or “including at least one”, unless specified otherwise.