FR3011508A1 - SECURITY DOCUMENT COMPRISING AN INTERFERENTIAL EFFECT FILM, METHOD FOR DETERMINING THE AUTHENTICITY OF SUCH A DOCUMENT AND DEVICE FOR IMPLEMENTING SUCH A METHOD - Google Patents

Abstract

The invention relates to a security document comprising a support (2, 102, 202) comprising at least one security element (3, 103, 203). According to the invention, the security element comprises a film with interference effects (4, 110, 220). The invention also relates to a method for determining the authenticity of such a document and a device for implementing such a method.

Description

The invention relates to a security document comprising a film with interference effects, a method for determining the authenticity of such a document and a device for implementing such a method.

BACKGROUND OF THE INVENTION There are known banknotes comprising a support which comprises at least one security element. The security element is printed on the banknote using an ink called OVI (Optical Variable Ink) ink. The security element thus has a different color depending on the orientation with which the security element is observed. However, security elements printed from OVI inks change little color according to the orientations with which they are observed. In addition, printing the security element with OVI ink makes the security element opaque. When the banknote is observed by transmission, that is by illuminating one of the faces of the banknote and by observing the other side of the banknote, the security element Pass no light: there is therefore no color change of the security element even changing viewing angle and the variable optical effects of the security element are lost. OBJECT OF THE INVENTION An object of the invention is to provide a security document comprising a security element with interference effects which is more difficult to reproduce than the security elements printed from an OVI type ink. BRIEF DESCRIPTION OF THE INVENTION In order to achieve this goal, a security document is proposed comprising a support comprising at least one security element.

According to the invention, the security element comprises a film with interference effects. By "interferential effects" it is of course understood that the film has optical properties such that: the film has a different color depending on the orientation with which the film is observed; the film has a different color for at least some distinct lighting and for the same observation angle of the film. The interference effect film is sufficiently transparent to allow the transmission of light rays through it and allow objects to be clearly viewed through it. The film is therefore colored but is not opaque. By virtue of the interference effect film, the security element according to the invention has the advantage of being much more sensitive to the direction of the light rays passing through it than the security elements of the prior art printed from FIG. an OVI ink. Thus, the security element can take a multitude of different colors depending on the directions with which it is observed. This multitude of different colors makes the security element much more difficult to reproduce fraudulently. The fraudulent printing of the security document even with particular inks thus does not make it possible to reproduce such a multiplicity of colors. In addition, the security element exhibits color variations both by orienting the security element differently than by illuminating the security element differently (different illumination angle, different type of light, possible illumination of the security element). back side of the security document instead of the front of the security document. ").

It is therefore particularly difficult to fraudulently reproduce the security document and this multiplicity of colors. Due to the fact that the film is sufficiently transparent, it is possible to study the color change variations of the security element by reflection (study of one side of the security document without illumination on the other side of the document). security document is the study of the rays reflected by the security document) 10 but also by transmission (study of one side of the security document with illumination of the other side of the security document is the study of refracted rays and transmitted by the security document). To authenticate the security document, it is therefore possible to check the color changes by reflection or transmission. There is therefore a possible double check that can not be performed with the security elements of the prior art printed with OVI type inks. It is therefore much more difficult to fraudulently reproduce the security element without this fraud being detected. There is also provided a method for determining the authenticity of such a security document comprising the successive steps of: illuminating a first face of the security document at a first incidence at a range of wavelengths centered around a first wavelength and identify at least one variable representative of a first light beam reflected by the security document, - illuminate the first face of the security document under a second incidence different from the first incidence and to a range of wavelengths centered around a second wavelength different from or identical to the first wavelength and locating at least one variable representative of a second light beam reflected by the security document, - estimating the authenticity of the security document according to the variables identified, - indicate whether the security document is authentic or not. There is also provided a device for carrying out the aforementioned determination method comprising at least a first radiation source and a second radiation source spaced apart and inclined with respect to each other with respect to the first face of the document of FIG. security, and at least first means for locating the variables of the light rays reflected by the security document, the first locating means being arranged opposite the first face of the security document. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in the light of the following description of a non-limiting embodiment of the invention with reference to the attached figures, in which: FIG. perspective of a security document according to a first embodiment of the invention; FIG. 2 is a view of the edge of the security document illustrated in FIG. 1; FIG. 3 is a perspective view of a security document according to a second embodiment of the invention; FIG. 4 is a view of the edge of the security document illustrated in FIG. 3; FIG. 5 is a perspective view of a security document according to a third embodiment of the invention; FIG. 6 is a schematic side view of a device for implementing a method for detecting a security document illustrated in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1 and 2 , the security document according to the first embodiment is here a banknote 1. The ticket 1 comprises a support 2 which comprises a security element 3. The thickness of the ticket and the security element are of course exaggerated in Figures 1 and 2 to facilitate understanding of said figures. The support 2 thus has a thickness of 100 micrometers. According to the invention the security element 3 comprises a film with interferential effects 4.

Part of the film 4 is here integrated in the thickness of the support 2 so that a first main face of the film 4 is visible and the second main face of the film 4, opposite to the first main face, is embedded in the thickness of the support 2. The film 4 is flush with the surface of the support 2. In particular, the ticket 1 has an orifice 5 passing through the thickness of the support 2 so that part of the second main face of the film 4 remains visible at through this orifice 5.

Preferably, the film 4 is a multilayer film having a thickness of less than 50 micrometers. Each layer of the film 4 comprises a sheet, each sheet having a refractive index different from that of the two sheets framing it.

In this way each light ray illuminating the film 4 is reflected differently by each sheet forming the film 4 which gives a multi-color rendering: different portions of the film 4 have different colors at the same angle of observation of the one of the main faces of the support 2. Depending on the incidence with which the light rays reach the film 4, the multi-color rendering of the film 4 is also different. Preferably, the film 4 has an asymmetrical structure along a plane P of the film 4 which is parallel to the two main faces of the film 4 and which extends in the center of said film 4, that is to say in the middle of the thickness 4. For example, if the film 4 has a first succession of leaves and a second succession of sheets arranged on either side of a central sheet, the first succession of sheets has refractive indices distinct from those of the second succession of leaves. Thus, the multi-color rendering of the film 4 is also clearly different depending on whether one illuminates one or the other of the main faces of the support 2. Thus, if we observe the first main face of the support 2 (corresponding to the first main face of the film 4) and that we illuminate the first main face of the support 2 we observe a first multi-color rendering of the film 4. If we observe the first main face of the support 2 and that we illuminate the second main face of the support 2 (opposite the first main face of the support 2), there is a second multi-color rendering of the film 4, the rendering being brighter at the portion of the film 4 covering the orifice 5 If the second main face of the support 2 is observed and the second main face of the support 2 is illuminated, a third multi-color rendition of the film 4 is observed at the aperture 5. If we observe the second main face of the support 2 and that we explode In the first main support face 2, there is a fourth multi-color rendition of the film 4 which is brighter at the orifice 5.

The very particular optical properties of the film 4 make it difficult to reproduce fraudulently the security element 3 and therefore the banknote 1. The security element here comprises a marking carried by the first major face of the film 4. The marking 6 is here a barcode. The barcode thus makes it possible to further secure the security element. For example, the bar code is imprinted with a preferably transparent fluorescent ink under a visible spectrum. For example, the marking 6 is printed with a fluorescent ink under ultraviolet light (for example white fluorescent). If the first main surface of the support 2 is illuminated by a light having a wavelength range extending between the ultraviolet and a part of the visible spectrum and the first main surface of the support 2 is observed under different angles, the film 4 will change color due to its optical properties but the marking remained white. If the first main surface of the support 2 is now illuminated by a light having a wavelength range extending between the ultraviolet and a portion of the visible spectrum and the second main surface of the support 2 is observed. from different angles, the film 4 will change colors because of its optical properties and will also have different colors in the marking 6, the colors at the marking 6 being different from those of the rest of the film 4 because the passage of the rays 30 ultraviolet and the part of the visible spectrum through the marking ink 6 modifies the properties of the film 4. The marking ink 6 thus makes it possible to locally modify the optical properties of the film 4. This then makes it particularly difficult to reproduce fraudulently of the security element.

A second embodiment of the invention will now be described with reference to Figures 3 and 4. The thickness of the ticket and the security element are of course exaggerated in Figures 3 and 4 to facilitate understanding of said figures. The elements in common with the first embodiment retain their numbering increased by one hundred. The security element 103 here comprises a film with interference effects which is shaped into a wire 110. The wire 110 is arranged in the support in "windowed thread". This term is well known in the field of bank notes and means that the wire 110 is arranged in the support so that first portions of the wire are entirely embedded in the thickness of the support 102 and that second portions of the wire are flush with the surface of the first main face of the support 102, these second portions therefore being visible at said first main face of the support 102. The first portions and the second portions extend successively in the support 102.

The security element here comprises a film 115 having a structure acting as a diffraction grating. In particular, the film 115 completely covers one of the faces of the wire 110 so as to be visible at the second portions of the wire 110.

It is recalled that a diffraction grating is an optical device composed of a series of parallel slits (grating in transmission) or reflective stripes (lattice in reflection): if white light reaches the grating, the grating breaks down the light at the way of a prism. Thus, the film 115 adds colored iridescence on one of the faces of the wire 110 due to its particular structure. The film 115 therefore modifies the optical properties of the wire 110 on only one side of the wire 110, which makes it particularly difficult to fraudulently reproduce the security element 103 according to this second embodiment. In this way, different portions of the film assembly 115 - wire 110 have different colors at the same angle of observation of one of the faces of the support 102. Depending on the incidence with which the light rays reach the film assembly 115 - thread 110, the multi-color rendering of the film assembly 115 - thread 110 is furthermore different.

In addition, the multi-color rendering of the film assembly 115 - thread 110 is different depending on whether one illuminates one or the other of the main faces of the support 102. In fact, the security element then has a asymmetric structure according to a plane P 'of the security element which is parallel to the two main faces of the security element and which extends in the center of the security element by the arrangement of the film 115 on a Only the face of the wire 110. The other side of the wire 110 is not covered with any film, the light path of the rays transmitted in one direction and the other through the support 102 is not the same. Thus, if we observe the first main face of the support 102 and that we illuminate the first main face of the support 102 is observed a first multi-color rendering of the second portions of the film assembly 115 - 110 thread. observes the first main face of the support 102 and that we illuminate the second main face of the support 102, there is a second multi-color rendering of the second portions of the film assembly 115 - 110 thread. If we observe the second main face of the support 102 and that the first main face of the support 102 is illuminated, a third multi-color rendering of the second portions of the film assembly 115 - wire 110 is observed.

It should be noted that the first portions may possibly be observed in transmission but their color rendition will then be much less noticeable than that of the second portions.

The marking of the security element 103 is here a printed letter 111 on each second portion of the wire 110. A third embodiment of the invention will now be described with reference to FIG.

The thickness of the note and the security element are, of course, exaggerated in FIG. 5 to facilitate the understanding of FIG. 5. The elements in common with the first embodiment retain their numbering increased by two hundred.

The security element 203 here comprises a film with interference effects 220 which is stuck on one of the main faces of the support 202. The marking of the security element is here a logo 221 printed on the film.

A method of determining the authenticity of the bill according to the second embodiment will now be described. In a first step, a first face of the ticket 101 is illuminated at a first incidence at a wavelength range centered around a first wavelength. The spectral response of first light rays reflected by the bill 101 under the action of the illumination according to three distinct observation angles is then located and the spectral response of second light rays refracted and transmitted by the bill 101 under the action of lighting according to three different viewing angles. Thus, the light response of the first face and the light response of the second face of the ticket 101 opposite to the first face of the note are studied in three different observation angles for each of the two faces of the bill 101. During a second step, the ticket 101 is illuminated under a second first incidence and at a centered around a second the first wavelength. The spectral response of third light rays reflected by the ticket 101 under the action of the illumination according to the three different observation angles and the response spectrum of fourth light rays refracted and transmitted by the ticket 101 under the action of lighting according to the three different viewing angles. The luminous response of the first face and the luminous response of the second face are thus studied again under different angles of observation between them but identical to those of the first step. In a third step, the ticket 101 is illuminated under a third incidence different from the first incidence and at a wavelength range centered around a third wavelength identical to the first wavelength. The spectral response of fifth light rays reflected by the bill 101 under the action of the illumination according to the three distinct observation angles and the spectral response of the sixth light rays refracted and transmitted by the bill 101 under the action are then located. lighting according to three different viewing angles. We thus study again the light response of the first face and the light response of the second face at different angles of observation between them but identical to those of the first step and the second step. During a fourth step, the authenticity of the ticket 101 is estimated as a function of the spectral responses of the first, second, third, fourth, fifth and sixth light rays, for example by comparing each of the 18 spectral responses identified with a response. corresponding theoretical spectral. The estimate may be such that all comparisons must match for ticket 101 to be considered authentic or may be such that only a predetermined number of comparisons must match for ticket 101 to be deemed authentic. In a fifth step, it is indicated whether the ticket 101 is authentic or not. It is thus possible to study the authenticity of the ticket 101 by reflection (study of the light rays reflected by the ticket and thus of the colors of the first face of the ticket) and by transmission (study of the light rays refracted and transmitted by the ticket and therefore colors of the second face of the note). The authentication method of the ticket 101 according to the invention is therefore particularly severe and allows a very good detection of illicitly reproduced tickets. Such a method can not be implemented with a security element of the prior art printed with OVI ink on the support since such inks are opaque in transmission. According to a particular embodiment, the method furthermore comprises the successive additional steps of: - taking at least one image of at least a part of the bank note 101, - marking of the marking 111, - analysis of the Authenticity of the marking 111. During the fifth step, it is thus indicated whether the ticket 101 is authentic according to the analysis of the spectral responses of the first, second, third, fourth, fifth and sixth light rays identified and the analysis of the authenticity of the marking 111. With reference to FIG. 6, the device for carrying out the method described above comprises here a first radiation source 301 for the implementation of the first step, a second source radiation 302 for the implementation of the second step and a third radiation source 303 for the implementation of the third step. The three radiation sources 301, 302, 303 are spaced apart and inclined with respect to each other facing the first face of the ticket 101. The device furthermore comprises here first locating means comprising in this case three first detection sensors. recording 311, 312, 313 spectral responses of light rays reflected by the ticket 101 for the implementation of the first three steps, the first three sensors 311, 312, 313 being arranged opposite the first face of the ticket 101. The device also comprises second identification means comprising here three second recording sensors 321, 322, 323 of the spectral responses of the light rays refracted and transmitted by the ticket 101 for the implementation of the first three steps. The three second sensors 321, 322, 323 are arranged facing the second face of the ticket 101. Naturally, the invention is not limited to the embodiment described and variant embodiments can be provided without departing from the scope. of the invention as defined by the claims. In particular, although here the various security documents described are banknotes, the security document according to the invention may be an identity card, an official paper ... The security element may have a security card. symmetrical structure 35 in a plane of the security element which is parallel to the two parallel main faces of the security element and extends in the center of the security element. Alternatively, the security element may have an asymmetrical structure which will allow a greater number of color variations of the interference effect film according to the face of the observed security element. Although here the film is composed of a stack of sheets of different refractive indices, the film may have any structure for imparting interference properties to the film. The film may thus comprise a mesh of micro-elements (like micro-spheres) in three dimensions or comprise a structure based on liquid crystals. Unlike an OVI ink, it is above all the particular internal structure of the film with interferential effects, and not the material constituting it, which gives the film its optical properties. The film may be arranged partially in the thickness of the support or be only reported on the support. The film can be a patch reported on the support. The film may also be pasted on one side of the security document. The film may also film or encapsulate an entire face of the security document. The security element may not have any marking carried by the film. Preferably, however, a marking will be carried by the film. Indeed, the marking of the film will further secure the security element and make more complex the fraudulent reproduction of the security document. By "marking" will of course be understood any form, symbol, acronym, alphanumeric character ... entered voluntarily on or in the film to authenticate the film. The marking and / or the security element may comprise a protective layer, such as a layer of varnish, to protect the marking and / or the security element. The marking may be printed by another type of ink than that described as an ink visible in the visible or visible spectrum only under infrared or ultraviolet light or more generally a visible ink under radiation at a wavelength range centered around a first wavelength and transparent under radiation at a wavelength range centered around a second wavelength. The ink may also be an ink having a different color depending on the illumination with which the marking and / or the angle is illuminated according to which the marking is viewed as an ink having a first color under ultraviolet light and a second color under illumination. infrared. The ink may also be an ink called "anti-Stokes" which designates in the field of security documents inks that contain luminescent substances reacting under a given wavelength excitation illumination, the inks having a length retransmission wave of value less than the given wavelength of the excitation illumination. When the marking is composed of at least one luminescent ink, the latter may be able to re-emit in several distinct wavelengths when it is excited at a given wavelength or a range of wavelengths. For example, the ink may be such that it will be totally transparent under visible spectrum and will react in three distinct colors (a wavelength in green, one in red and one in blue) when it is excited with Infra Red radiation. The marking ink can thus make it possible to locally modify the optical properties of the film of the security element. This then makes it particularly difficult the fraudulent reproduction of the security element.

Although here the marking is registered by printing, the marking may be inscribed on or in the film by any other possible method such as embossing (mechanical or thermal) of the film or by metallization and / or demetallization of the film. Remarkably, embossing the film also makes it possible to locally modify the optical properties of the film, which makes the fraudulent reproduction of the security element particularly difficult.

The marking may be different from what has been described. The marking may thus comprise a barcode, a logo, an image and / or an alphanumeric code. The marking may possibly not represent a precise thing but be only identifiable by its shape or size, for example. The security document may not include a film having a structure acting as a diffraction grating. The security document may of course include a film having a structure acting as a diffraction grating in other embodiments than that described. The security document may not include an orifice for observing the second face of the integrated film or attached to the support.

The method of determination described is of course applicable to other embodiments than that described. The determination method may comprise a different number of illumination and identification steps of the variable related to light rays than those described. The marking may be carried out only for the reflected light rays or only for the light rays transmitted by the security document and not for both the reflected rays and rays transmitted by the security document. Lighting at different angles may also be wavelength ranges centered around different wavelengths. Preferably, when the marking will be printed from a visible ink under radiation at a range of wavelengths centered around a first wavelength and transparent under radiation at a wavelength range centered around a second wavelength, the method will include the steps of: - illuminating a first face of the security document at a first incidence at a wavelength range centered around a first wavelength and locating at least one variable representative of a first light beam reflected by the security document and taking at least a first image of at least a portion of the security document, - illuminating the first face of the security document under the second incidence and locate at least one variable representative of a second light ray reflected by the security document and take at least 20 a second image of at least a portion of the security document, - estimate the authenticity of the security document according to the variables identified, - identify the marking on the first image and the second image, - analyze the authenticity of the marking from the marking of the marking on the first image and the second image, indicate whether the security document is authentic according to the step of estimating the authenticity of the security document according to the variables identified and the step of analyzing the authenticity of the security document. marking. In this way, it is possible to simultaneously authenticate the film and the marking carried by the film.

Each radiation source may be operable in a single mode of excitation different from that of other radiation sources. Alternatively, each radiation source may illuminate the security document under illuminations of wavelength ranges centered around different wavelengths. Throughout the present application, the lighting of the banknote for the implementation of the determination method will be such that the wavelength range of the lighting will always comprise at least part of the visible spectrum. Visible spectrum is of course that part of the electromagnetic spectrum that is visible to the human eye (which corresponds substantially to a wavelength range of 380-800 nanometers).

A different number of responses may be identified during the implementation of the authentication method. Answers may only be identified from a single particular angle of view if the security element is illuminated differently (different lighting angle, different type of light, backlighting of the security document and the front panel of the security document. ") Alternatively, rather than illuminate one side of the security document and simultaneously study the transmitted and reflected rays from the security document on each side of the security document each of the sides of the security document can be successively illuminated and the transmitted and reflected rays of the security document on the one side of the security document respectively successively studied, the radiation sources being able to be arranged vis-à-vis the two faces. The sensors can be arranged on a single side of the security document. each of the sensors and each of the sources of

Claims (21)

REVENDICATIONS1. Security document comprising a support (2, 102, 202) comprising at least one security element (3, 103, 203), the document being characterized in that the security element comprises a film with interference effects (4, 110 , 220). 2. Security document according to claim 1, wherein the security element comprises a marking (6, 111, 221) carried by the film (4, 110, 220). 3. Security document according to claim 2, wherein the marking comprises at least one fluorescent ink. 4. Security document according to claim 3, wherein the fluorescent ink is adapted to re-emit in several wavelengths when it is excited at at least one given wavelength. 5. Safety document according to claim 2, wherein the marking (6, 111, 221) is inscribed on or in the film (4, 110, 220) by printing, metallization and / or demetallization, embossing. 6. Security document according to claim 2, in which the marking (4, 110, 220) comprises a bar code and / or a logo and / or an image and / or an alphanumeric code. 7. Security document according to claim 1, wherein the film (4, 110, 220) is a multilayer film. 8. Security document according to claim 7, wherein each layer comprises a sheet, each sheet having a refractive index different from that of the two sheets flanking it. The security document of claim 1, wherein the film (4, 110, 220) has a thickness of less than 50 microns. The security document as claimed in claim 1, wherein the film comprises a mesh of micro-elements in three dimensions. 11. Security document according to claim 5, wherein the film (4, 110) is integrated at least in part in the thickness of the support. 12. Security document according to claim 1, wherein the film (220) is attached to the support. 13. The security document of claim 12, wherein the film laminates an entire surface of the carrier or the film (220) is adhered to a portion of the carrier. The security document of claim 1, further comprising a film (115) having a structure acting as a diffraction grating. 15 15. Security document according to claim 14, wherein the film (115) covers one side of the film (110). The security document according to claim 1, wherein the security element is configured to have an asymmetric structure in a plane (P, P ') of the security element which is parallel to the two main faces of the security element. the security element and extending to the center of the security element. 17. Security document according to claims 8 and 16, wherein a first succession of leaves and a second succession of leaves are arranged on either side of a central sheet, the first succession of sheets having refractive indices. distinct from those of the second succession of leaves. 30 18. A method for determining the authenticity of a security document according to one of the preceding claims, comprising the successive steps of: - illuminating a first face of the security document (1, 101, 201) under a first incidence to a wavelength range centered around a first wavelength and locating at least one variable representative of a first light beam reflected by the security document (1, 101, 201), - illuminating the first face of the security document (1, 101, 201) under a second incidence different from the first incidence and at a range of wavelengths centered around a second wavelength different from or identical to the first wavelength and locating at least one variable representative of a second light beam reflected by the security document (1, 101, 201), - estimate the authenticity of the security document (1, 101, 201) according to the variables identified - indicate whether the security document (1, 101, 201) is authentic or not. 19. The determination method according to claim 18, comprising the additional steps of locating at least one variable representative of a third light beam refracted and transmitted by the security document (1, 101, 201) when the first side is illuminated under the first incidence and at the wavelength range centered around the first wavelength; and locating at least one variable representative of a fourth light beam refracted and transmitted by the security document (1, 101, 201) when the first side is illuminated under the second incidence and at the wavelength range centered around of the second wavelength, the step of estimating the authenticity of the security document (1, 101, 201) being then implemented as a function of the variables representative of the first light ray, the second light ray, the third light ray and fourth light ray. Apparatus for carrying out the determination method according to claim 18 or claim 19, comprising at least a first radiation source (301) and a second radiation source (302) spaced apart and inclined relative to one another. to the other opposite the first face of the security document (1, 101, 201), and at least first means for locating the variables representative of the light rays reflected by the security document, the first locating means being arranged next to the first side of the security document. 21. Detection device according to claim 20, further comprising at least second means for locating the variables representative of the light rays refracted and transmitted by the security document, the second locating means being arranged opposite the second face of the document. of security.